CN103073379B - Olefin separation and alkene separation method - Google Patents

Abstract

The invention provides an olefin separation system and an olefin separation method. The olefin separation system includes a demethanization unit, and the demethanization unit includes a primary demethanizer, a membrane separation module, a pressure swing adsorption system and a secondary demethanizer, and a device is arranged between the top outlet of the primary demethanizer and the inlet of the membrane separation module The first gas phase flow pipeline; and the connection mode of the pressure swing adsorption system adopts one of the following: connection mode 1: the hydrocarbon-rich gas flow outlet of the membrane separation module is connected with the inlet of the pressure swing adsorption system, and the hydrocarbon-rich gas flow outlet of the pressure swing adsorption system There is a hydrocarbon-rich gas flow pipeline between the inlet of the secondary demethanizer; or connection method 2: the hydrogen-rich gas outlet of the membrane separation module is connected to the inlet of the pressure swing adsorption system, and the hydrocarbon-rich gas outlet of the membrane separation module and the pressure swing A hydrocarbon-rich gas flow pipeline is arranged between the hydrocarbon-rich gas flow outlet of the adsorption system and the inlet of the secondary demethanizer. The olefin separation system increases the ratio of CH ₄ /H ₂ in the secondary demethanizer and reduces energy consumption.

Description

Olefin separation device and olefin separation method

technical field

The invention relates to the field of gas separation, in particular to an olefin separation device and an olefin separation method.

Background technique

In addition to ethylene and propylene, petroleum cracking gas, refinery dry gas and methanol-to-olefin product gas also contain a large number of other components, such as hydrogen, methane, acetylene, propane and nitrogen. Since ethylene and propylene are important chemical raw materials, Therefore, the above petroleum cracking gas, refinery dry gas and methanol-to-olefin product gas can be used as raw materials to separate ethylene and propylene. At present, the cryogenic separation method is the most mature and widely used.

Typical conventional cryogenic separation methods have many disadvantages. For example, it usually requires 4 to 5 stages of compression of the raw material gas, which requires a large amount of low-temperature cooling medium. For example, methane-hydrogen separation requires a refrigeration system below -100°C for cooling. Therefore, Conventional cryogenic separation methods have high energy consumption and high requirements for equipment, so investment has to be increased in order to achieve ideal separation effects. In the cryogenic separation process, the separation of hydrogen and methane consumes the most energy and expense in the entire separation device, and the process is complex. Because the molecular ratio of CH ₄ /H ₂ in the feed gas has a great influence on the loss of ethylene in the tail gas, this is because the demethanizer item reduces the partial pressure of CH ₄ due to the presence of H ₂ and other inert gases, and only by increasing the pressure or reducing the temperature To meet the dew point requirements at the top of the tower, increase the pressure and lower the temperature while separating _CH4 , part of ethylene will also be separated together with _CH4 , resulting in the loss of ethylene. The above-mentioned effects are determined by the phase equilibrium and are not It depends on the number of trays and the reflux ratio. Therefore, under constant temperature and pressure conditions, the smaller the ratio of CH ₄ /H ₂ molecules in the feed gas, the greater the loss of ethylene in the tail gas, and vice versa, and the lower the energy consumption. . Therefore, how to separate hydrogen from cracked gas or olefin mixture as much as possible to reduce the energy consumption of hydrogen-methane separation has attracted widespread attention.

The existing Lummus technology is one of the more advanced technologies in the cryogenic olefin separation. The structural diagram of the Lummus olefin cryogenic separation device is shown in Figure 1: the feed gas is dried by the dryer 52' and then enters the depropanizer 51', the top gas phase of the depropanizer 51' is partially condensed by the top condenser 54' of the depropanizer unit, and then separated from gas and liquid, and the condensed liquid is used as the reflux of the depropanizer system, and the rest contains C3 hydrocarbons and carbon The gas phase of the hydrocarbon components below three enters the compressor 53' to increase the pressure, and then passes through the second reboiler 192', the first refrigerant chiller 161' and the second refrigerant chiller 162' for a series of heat exchanges After the cooling process, it enters the demethanizer 11'; the bottom product of the depropanizer 51' is C4 and components above C4 and is sent to the debutanizer 61'. The overhead condenser of the demethanization unit uses propylene (or ethylene) as a refrigerant, and after the partially condensed overhead stream enters the reflux tank (the overhead condenser and the reflux tank of the demethanization unit are not shown in Figure 1), the reflux tank The separated liquid phase is used as the reflux of the demethanizer 11', and the gas phase (mainly hydrogen and methane, called hydrogen-methane flow) is sent to the gas pipeline network outside the device after heat exchange by the cold box 142'. The stream composed of carbon dihydrocarbons and carbon trihydrocarbons at the bottom of the demethanizer 11' enters the deethanizer 31', and the overhead stream of the deethanizer 31' first passes through the hydrodeacetylation reactor 21' to convert the stream Alkynes (mainly acetylene) are converted into ethylene and ethane and then enter the ethylene rectification tower 22', and the gas phase at the top of the ethylene rectification tower 22' is sent to the device tank area as ethylene products, and the ethylene rectification tower 22' The ethane at the bottom of the tower is heated and vaporized by the heat exchanger, and then sent to the fuel gas system for use as fuel or recycling. The bottom stream of the deethanizer 31' enters the propylene rectification unit, and the propylene product at the top of the propylene rectification tower 41' is condensed by the top water cooler 43', and part of the liquid phase material is refluxed through the top reflux tank 42' , and then pass through the product guard bed (not shown in Fig. 1) to remove methanol, oxides and other impurities as propylene product and send it to the propylene tank area of the device, and partly reflux the propylene rectifying tower 41'. The propane stream at the bottom of the propylene rectification tower 41' passes through the cold box 142' to exchange heat with the hydrogen and methane gas stream to cool down, and is quenched by the refrigerant through the third refrigerant chiller 163' and then introduced to the top of the demethanizer 11' to Absorb the methane at the demethanizer 11' and the ethylene in the hydrogen stream; the other stream enters the gas pipeline network for use as gas after heat exchange through the cold box 142'. The material containing C4 and above components separated by the propylene rectification unit enters the debutanizer 61' to separate C4 hydrocarbons and C4 or above hydrocarbon products.

The above-mentioned conventional cryogenic technology and Lummus technology are difficult to obtain the ideal molecular ratio of methane and hydrogen by one-time demethanization treatment, which leads to high energy consumption, large ethylene loss and high investment in the process of separating ethylene from tail gas Disadvantage, the present invention is mainly an improvement on the Lummus technology in order to reduce energy consumption and reduce ethylene loss on the basis of the Lummus technology.

Contents of the invention

The invention aims to provide an olefin separation device and an olefin separation method, which reduce energy consumption in the olefin separation process.

In order to achieve the above object, according to one aspect of the present invention, an olefin separation device is provided, the above-mentioned olefin separation device includes a demethanizer unit, and the demethanizer unit includes an initial demethanizer, a membrane separation module, a pressure swing adsorption system and a secondary demethanizer Tower, the first gas phase flow pipeline is set between the top outlet of the initial demethanizer and the inlet of the membrane separation module; and the connection mode of the pressure swing adsorption system adopts one of the following: connection mode 1: the hydrocarbon-rich gas flow of the membrane separation module The outlet is connected to the inlet of the pressure swing adsorption system, and a hydrocarbon-rich gas flow pipeline is set between the outlet of the pressure swing adsorption system and the inlet of the secondary demethanizer; or connection method 2: the outlet of the hydrogen-rich gas flow of the membrane separation module is connected to the The inlet of the pressure swing adsorption system is connected, and a hydrocarbon-rich gas flow pipeline is arranged between the hydrocarbon-rich gas flow outlet of the membrane separation module and the hydrocarbon-rich gas flow outlet of the pressure swing adsorption system and the inlet of the secondary demethanizer.

Further, the above-mentioned demethanizer unit also includes a first compressor, a first cold box, a first heat exchanger, a second heat exchanger, a first refrigerant chiller and an expander, and the top outlet of the secondary demethanizer There is a second gas phase flow pipeline between the inlet of the expander; the first compressor is set on the hydrocarbon-rich gas flow pipeline; the first cold box has: the first gas phase flow path in the first cold box, connected in series to the first gas phase In the logistics pipeline; the flow path in the first cold box of the hydrocarbon-rich gas flow is connected in series in the hydrocarbon-rich gas flow pipeline between the first compressor and the inlet of the secondary demethanizer; the first heat exchanger has: the hydrocarbon-rich gas flow first The inner flow path of the heat exchanger is connected in series in the hydrocarbon-rich gas flow pipeline between the first cold box inner flow path of the hydrocarbon-rich gas flow and the inlet of the secondary demethanizer; the second liquid phase flow first heat exchanger inner flow path, It is connected with the bottom outlet of the secondary demethanizer; the second heat exchanger has: the internal flow path of the second heat exchanger of the hydrocarbon-rich gas flow, which is connected in series between the internal flow path of the first heat exchanger of the hydrocarbon-rich gas flow and the secondary demethanizer In the hydrocarbon-rich gas flow pipeline between the inlets; the flow path in the second heat exchanger of the second gas phase flow is connected with the outlet of the expander; the first refrigerant chiller is arranged in the second heat exchanger of the hydrocarbon-rich gas flow Between the flow path and the inlet of the secondary demethanizer.

Further, the above-mentioned demethanizer unit also includes: a first reboiler, which is connected with the first bottom outlet of the initial demethanizer and connected with the bottom of the initial demethanizer to form a first circulation line; the second reboiler , communicated with the second tower bottom outlet of the primary demethanizer and connected with the tower still of the primary demethanizer to form a second circulation pipeline.

Further, the above-mentioned olefin separation device also includes an ethylene rectification unit, and the ethylene rectification unit includes: a hydrodeacetylation reactor, having: a hydrogen gas flow inlet, when the pressure swing adsorption system adopts connection mode 1, the hydrogen gas flow inlet and the pressure swing adsorption There is a hydrogen-rich gas flow pipeline between the hydrogen-rich gas flow outlet of the system and the hydrogen-rich gas flow outlet of the membrane separation module. It has a high-purity hydrogen flow pipeline, and a flow regulating valve is set on the high-purity hydrogen flow pipeline; there is a second liquid phase flow pipeline between the hydrocarbon material inlet and the bottom outlet of the secondary demethanizer; the ethylene product outlet; The distillation tower is connected with the ethylene product outlet.

Further, the above-mentioned olefin separation device also includes a deethanizer unit and a propylene rectification unit, the deethanizer unit includes a deethanizer tower, and the deethanizer tower has: the first liquid phase stream inlet, and the third demethanizer tower There is a first liquid phase stream pipeline between the bottom outlet of the tower; there is a hydrocarbon deacetylation material delivery pipeline between the deethanizer overhead stream outlet and the hydrocarbon material inlet of the hydrodeacetylation reactor; the propylene rectification unit includes : Propylene rectification tower, has: the third liquid phase flow import, has the third liquid phase flow line between the tower bottom outlet of deethanizer; Tower top propylene outlet; Tower top reflux tank, with the propylene rectification tower The top propylene outlet is communicated with the propylene rectifying tower to form a third circulation pipeline, and the first reboiler or the second reboiler has a propylene inlet and a propylene outlet communicated with the third circulation pipeline.

Further, a control valve is further arranged on the third circulation line between the above-mentioned propylene rectification tower and the top reflux tank, and the control valve is arranged in parallel with the first reboiler or the second reboiler.

Further, the above-mentioned olefin separation device also includes a second cold box, the second cold box has a second gas-phase liquid flow second cold box internal flow path, the second gas-phase liquid flow second cold box internal flow path and the second heat exchanger The second gas-phase flow of the second heat exchanger is communicated with the flow path; there are two fourth liquid-phase flow pipelines between the propylene rectification tower and the second cold box, and one of the fourth liquid-phase flow pipelines passes through the second After the cold box, it is connected with the gas pipeline network; another fourth liquid phase flow pipeline passes through the second cold box and extends to communicate with the primary demethanizer. The olefin separation device also includes a second refrigerant chiller, and the second The refrigerant chiller is arranged on the fourth liquid phase stream line between the second cold box and the primary demethanizer.

Further, the above-mentioned olefin separation device also includes: a depropanizer unit, including: a depropanizer, a primary degassing phase flow line is arranged between the top outlet of the depropanizer and the primary demethanizer; a dryer, connected to the depropanizer The inlet is connected to the depropanizer to transport the raw material gas to be separated; the second compressor is set on the primary degassing phase flow pipeline between the depropanizer and the primary demethanizer; the third refrigerant chiller is set on the second On the primary degassed phase stream line between the compressor and the primary demethanizer, the first cold box has a primary degassed phase stream connected to the primary degassed phase stream line between the second compressor and the third refrigerant chiller The inlet and the initial degasification phase stream outlet; the debutanizer unit, including: debutanizer, and the first liquid phase stream line is arranged between the debutanizer and the debutanizer; The connected inlet and the outlet for the condensed product to flow out.

According to another aspect of the present invention, there is also provided a method for separating olefins, the above method for separating olefins includes a process of separating a mixed gas whose main components are hydrogen, C3 hydrocarbons and hydrocarbons below C3, the process includes: initial demethanization Process: Make the mixed gas undergo non-clear cutting in the initial demethanization process to obtain the first gas phase stream and the first liquid phase stream separated from each other, the first gas phase stream includes hydrogen, methane and carbon dihydrocarbons, and the first liquid phase stream includes C2 hydrocarbons and C3 hydrocarbons; membrane separation process: the first gas phase stream is subjected to membrane separation to obtain the first hydrocarbon-rich gas flow and the first hydrogen-rich gas flow separated from each other; the pressure swing adsorption process adopts the following methods: Mode 1: Performing pressure swing adsorption on the first hydrocarbon-rich gas stream to obtain a second hydrocarbon-rich gas stream and a second hydrogen-rich gas stream that are separated from each other; method 2: subjecting the first hydrogen-rich gas stream to pressure swing adsorption to obtain a high-purity hydrogen gas stream and a third hydrocarbon-rich gas stream Secondary demethanization process: the first hydrocarbon-rich gas stream in mode one or the first hydrocarbon-rich gas stream and the third hydrocarbon-rich gas stream in mode two are clearly cut in secondary demethanization to obtain the second gas phase stream and the second gas phase stream separated from each other two-phase flow.

Further, the first gas phase stream obtained from the above primary demethanization process contains carbon dihydrocarbons with a volume percentage of 15-90%; the volume percentage of hydrogen in the first hydrogen-rich gas stream obtained from the membrane separation process is 75-95%, The volume of hydrogen in the hydrogen-rich gas stream accounts for 45-65% of the total volume of hydrogen in the first gas-phase stream. When the pressure swing adsorption process adopts mode one, the volume percentage of hydrogen in the second hydrogen-rich gas stream obtained by the pressure swing adsorption process is 85-65%. 99.99%; the volume content of ethylene in the second gas phase stream obtained from the secondary demethanization process is ≤2%.

Further, the above process also includes: making the mixed gas undergo heat exchange with the first gaseous phase stream obtained by non-clear cutting in sequence, and conduct heat exchange with the refrigerant to perform the initial demethanization process; make the first hydrocarbon-rich The gas stream or the first hydrocarbon-rich gas stream and the third hydrocarbon-rich gas stream in the second method are sequentially compressed, exchanged heat with the first gas phase stream separated from the primary demethanization process, and exchanged heat with the second liquid stream separated from the secondary demethanization process. The phase stream is subjected to heat exchange, and the secondary demethanization process is performed after heat exchange with the second gas phase stream separated from the secondary demethanization; before the heat exchange between the second gas phase stream separated from the secondary demethanization and the second hydrocarbon-rich gas Carry out expansion and cooling; make part of the first liquid phase flow separated from the initial demethanization process, and then reheat and boil to repeat the initial demethanization process.

Further, the above olefin separation method also includes: depropanizing the raw material gas to be separated and then compressing to form a mixed gas; deethanizing part of the first liquid phase stream to obtain the deethanizer overhead stream and the third liquid Phase flow; when the pressure swing adsorption process adopts mode one, make the deethanizer overhead stream and the first hydrogen-rich gas stream and/or the second hydrogen-rich gas stream and/or external hydrogen carry out hydrodeacetylation reaction to obtain the deacetylated For the ethylene-containing mixture, when the pressure swing adsorption process adopts the second method, the de-ethanizer overhead stream is subjected to hydrodeacetylation reaction with high-purity hydrogen flow and/or external hydrogen to obtain the deacetylated ethylene-containing mixture; the ethylene-containing mixture is The mixture is rectified to obtain ethylene products; the third liquid phase stream is rectified to obtain the fourth gas phase stream and the fourth liquid phase stream, and the fourth gas phase stream is exchanged with part of the first liquid phase stream to form propylene after further impurity removal treatment Product; after exchanging heat between the fourth liquid-phase stream and the second gas-phase stream, a part of the heat-exchanged fourth liquid-phase stream and the refrigerant are further exchanged for heat to be used to form the first gas phase in the initial demethanization process The ethylene in the gas phase material of the stream is transported as fuel gas by another part of the heat-exchanged fourth liquid phase stream.

Applying the technical scheme of the present invention, the primary demethanizer, the membrane separation module, the pressure swing adsorption system and the secondary demethanizer are used together, and after the cryogenic treatment of the primary demethanizer, the top work of the primary demethanizer is reasonably controlled The temperature and pressure of the gas to be separated are not clearly cut or clearly cut, so that the gas to be separated is treated by the primary demethanizer to obtain the first gas phase stream without carbon three and above hydrocarbons and further passes through the membrane of the membrane separation module After separation, the first hydrogen-rich gas stream and the first hydrocarbon-rich gas stream can be obtained, and the obtained first hydrocarbon-rich gas stream can be directly entered into the secondary demethanizer for further cryogenic separation, or can be adsorbed by a pressure swing adsorption system to obtain the second gas stream. The hydrogen-rich gas stream and the second hydrocarbon-rich gas stream, whether it is the first hydrocarbon-rich gas stream or the second hydrocarbon-rich gas stream, the CH ₄ /H ₂ molecular ratio has been greatly improved compared with the feed gas, thereby increasing the number of secondary demethanizers. The partial pressure of CH ₄ at the top, so it is only necessary to lower the temperature of the secondary demethanizer to a higher dew point to separate CH ₄ and H ₂ , then the energy consumption required for cooling during the separation process is reduced; and, Due to the increase of the dew point, only a lower cooling capacity is required to make the second gaseous phase stream separated from the top of the demethanizer tower have little or no ethylene, thus reducing the loss of ethylene; at the same time, the realization of the above technical effects The investment in olefin separation can be greatly reduced.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide a further understanding of the present invention, and the schematic embodiments and descriptions of the present invention are used to explain the present invention, and do not constitute an improper limitation of the present invention. In the attached picture:

Fig. 1 shows the structural representation of the Lummus olefin cryogenic separation device according to the prior art;

Fig. 2 shows a schematic structural view of an olefin separation device according to a preferred embodiment of the present invention; and

Fig. 3 shows a schematic structural diagram of an olefin separation device in another preferred embodiment of the present invention.

detailed description

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and examples.

As shown in Figure 2 and Figure 3, in a typical embodiment of the present invention, a kind of olefin separation device is provided, and this olefin separation device comprises demethanization unit, and demethanization unit comprises primary demethanizer 11, membrane separation module 121. The pressure swing adsorption system 122 and the secondary demethanizer 17, the first gas phase flow pipeline is arranged between the tower top outlet of the primary demethanizer 11 and the inlet of the membrane separation module 121; and the connection mode of the pressure swing adsorption system 122 adopts One of the following, connection mode one: the outlet of the hydrocarbon-rich gas flow of the membrane separation module 121 is connected with the inlet of the pressure swing adsorption system 122, and the outlet of the hydrocarbon-rich gas flow of the pressure swing adsorption system 122 and the inlet of the secondary demethanizer 17 Hydrocarbon-rich gas flow pipeline; connection mode two: the hydrogen-rich gas flow outlet of the membrane separation module 121 is connected to the inlet of the pressure swing adsorption system 122, the hydrocarbon-rich gas flow outlet of the membrane separation module 121 and the hydrocarbon-rich gas flow outlet of the pressure swing adsorption system 122 are connected to the A hydrocarbon-rich gas flow pipeline is arranged between the inlets of the secondary demethanizer 17

The olefin separation device with the above structure is used in conjunction with the primary demethanizer 11, the membrane separation module 121, the pressure swing adsorption system 122 and the secondary demethanizer 17. After the cryogenic treatment of the primary demethanizer 11, the primary demethanizer is reasonably controlled. The working temperature and pressure at the top of the methane tower 11 perform non-clear cutting or clear cutting on the gas to be separated, so that the gas to be separated can be treated by the primary demethanizer 11 to obtain the first gas phase that does not contain carbon three and above hydrocarbons After the stream is further separated by the membrane separation module 121, the first hydrogen-rich gas stream and the first hydrocarbon-rich gas stream are obtained. The obtained first hydrocarbon-rich gas stream can directly enter the secondary demethanizer for further cryogenic separation, or can be transformed into The second hydrogen-rich gas stream and the second hydrocarbon-rich gas stream are obtained after the adsorption treatment by the pressure adsorption system 122, and the _CH4 / _H2 molecular ratios of the first hydrocarbon-rich gas stream and the second hydrocarbon-rich gas stream are much higher than those of the raw material gas. improve, and then increase the partial pressure of CH at the top of the secondary demethanizer 17, so it is only necessary to reduce the temperature of the secondary demethanizer 17 to a higher dew point to separate _{CH 4 and H 2 , then} in the separation process The required energy consumption for cooling in the medium is reduced; and, because the increase of the dew point makes it only need a lower cooling capacity, only little or no ethylene can be made in the second gaseous phase stream separated from the top of the secondary demethanizer 17, so The loss of ethylene is reduced; at the same time, the realization of the above technical effects can greatly reduce the investment in olefin separation.

When the pressure swing adsorption system 122 adopts connection mode two, the hydrocarbon-rich gas flow pipeline provided between the hydrocarbon-rich gas flow outlet of the membrane separation module 121 and the hydrocarbon-rich gas flow outlet of the pressure swing adsorption system 122 and the inlet of the secondary demethanizer 17 can be For two, the hydrocarbon-rich gas flow outlet of the membrane separation module 121 and the hydrocarbon-rich gas flow outlet of the pressure swing adsorption system 122 can be combined first, and then connected with the inlet of the secondary demethanizer 17 to set up a hydrocarbon-rich gas flow with branches. Airflow lines.

As shown in Figure 2 and Figure 3, in a preferred embodiment of the present invention, the above-mentioned demethanizer unit also includes a first compressor 131, a first cold box 141, a first heat exchanger 151, a second heat exchanger 152, the first refrigerant chiller 161 and the expander 18, there is a second gas phase stream pipeline between the tower top outlet of the secondary demethanizer 17 and the inlet of the expander 18; the first compressor 131 is arranged on the hydrocarbon-rich gas flow pipeline Above; the first cold box 141 has the first flow path in the first cold box of the first gaseous phase stream and the first flow path in the cold box of the hydrocarbon-rich gas flow, and the first flow path in the cold box of the first gaseous phase stream is connected in series with the pipeline of the first gaseous phase stream middle; the flow path in the first cold box of the hydrocarbon-rich gas flow is connected in series in the hydrocarbon-rich gas flow pipeline between the first compressor 131 and the inlet of the secondary demethanizer 17; The internal flow path of the heat exchanger and the internal flow path of the first heat exchanger of the second liquid phase flow, the internal flow path of the first heat exchanger of the hydrocarbon-rich gas flow are connected in series between the flow path of the first cold box of the hydrocarbon-rich gas flow and the secondary demethanizer 17 In the hydrocarbon-rich gas flow pipeline between the inlets; the flow path in the first heat exchanger of the second liquid phase stream communicates with the outlet at the bottom of the second demethanizer 17; The internal flow path of the heat exchanger and the second internal flow path of the second gas phase stream, the internal flow path of the second heat exchanger of the hydrocarbon-rich gas flow are connected in series between the internal flow path of the first heat exchanger of the hydrocarbon-rich gas flow and the secondary demethanizer 17 In the hydrocarbon-rich gas flow pipeline between the inlets; the flow path in the second heat exchanger of the second gas phase flow is connected with the outlet of the expander 18; the first refrigerant chiller 161 is arranged in the second heat exchanger of the rich hydrocarbon gas flow Between the internal flow path and the inlet of the secondary demethanizer 17.

In the above-mentioned olefin separation device, when the pressure swing adsorption system 122 adopts the connection mode 1, the second hydrocarbon-rich gas stream from the pressure swing adsorption system 122 or when the pressure swing adsorption system 122 adopts the connection mode 2, the first rich gas stream from the membrane separation module 121 After the hydrocarbon gas stream and the third hydrocarbon-rich gas stream from the pressure swing adsorption system 122 are compressed and boosted by the first compressor 131, they exchange heat with the first gas phase stream from the primary demethanizer 11 in the first cold box 141, and then the temperature decreases. , and then enter the first heat exchanger 151 to exchange heat with the cooling medium again, and then continue to enter the second heat exchanger 152 to exchange heat with the second gaseous stream whose temperature drops sharply after being expanded by the expander 18; The hydrocarbon gas stream or the second hydrocarbon-rich gas stream continues to enter the first refrigerant chiller 161 to exchange heat with the refrigerant for further cooling and enter the secondary demethanizer 17 at a lower temperature for cryogenic separation again. The first hydrocarbon-rich gas stream or the second A series of heat exchanges carried out by the second hydrocarbon-rich gas stream greatly reduces the temperature, further reducing the energy consumption of cryogenic separation in the secondary demethanizer 17 .

The first compressor 131 of the above-mentioned olefin separation device can be set in the following different ways. When the pressure swing adsorption system 122 adopts connection mode 1, the first compressor 131 is arranged on the hydrocarbon-rich gas flow pipeline. When the pressure swing adsorption system 122 adopts In connection mode 2, the first compressor 131 is arranged on the hydrocarbon-rich gas flow pipeline after the hydrocarbon-rich gas flow outlet of the membrane separation module 121 and the hydrocarbon-rich gas flow outlet of the pressure swing adsorption system 122 converge. A person skilled in the art can select an appropriate connection mode of the compressor according to the actual needs and the layout of the piping in the factory area.

As shown in Figure 2, the demethanizer unit also includes a first reboiler 191 and a second reboiler 192, the first reboiler 191 is in communication with the first bottom outlet of the initial demethanizer 11 and is connected with the initial demethanizer The bottoms of the towers 11 are connected to form a first circulation line; the second reboiler 192 is connected to the second bottom outlet of the primary demethanizer 11 and connected to the bottoms of the primary demethanizer 11 to form a second circulation line.

Part of the first liquid phase flowing out of the first bottom outlet and the second bottom outlet of the primary demethanizer 11 is heated by the first reboiler 191 or the second reboiler 192 and then returns to the primary demethanizer in a gas phase 11 in the tower kettle, and reverse contact mass transfer with the liquid phase flow left from the top of the tower to achieve the purpose of cryogenic distillation.

As shown in Figure 2 and Figure 3, the olefin separation device also includes an ethylene rectification unit, and the ethylene rectification unit includes a hydrodeacetylation reactor 21 and an ethylene rectification tower 22, and the hydrodeacetylation reactor 21 has a hydrogen gas flow inlet, Hydrocarbon material inlet and ethylene product outlet, when the pressure swing adsorption system 122 adopts connection mode 1, there is a hydrogen-rich gas flow between the hydrogen gas flow inlet and the hydrogen-rich gas flow outlet of the pressure swing adsorption system 122 and the hydrogen-rich gas flow outlet of the membrane separation module 121 Pipeline, when the pressure swing adsorption system 122 adopts connection mode 2, there is a high-purity hydrogen flow pipeline between the hydrogen gas flow inlet and the high-purity hydrogen flow outlet of the pressure swing adsorption system 122, and a flow regulating valve is set on the high-purity hydrogen flow pipeline There is a second liquid phase stream line between the hydrocarbon material inlet and the bottom outlet of the second demethanizer 17; the ethylene rectification tower 22 is connected with the ethylene product outlet.

The second liquid-phase stream separated from the secondary demethanizer 17, which is mainly carbon dihydrocarbons, is used as the cooling medium of the first heat exchanger 151 to exchange heat with the first gas-phase stream, after which the temperature rises and then enters the hydrodesorption process. The hydrogenation reaction is carried out in the alkyne reactor 21. In the hydrodeykyne reactor 21, the hydrogen is derived from the hydrogen-rich gas stream and/or external hydrogen separated by the membrane separation module 121 and the pressure swing adsorption system 122 or is combined with the hydrogen from the pressure swing adsorption system. 122 high-purity hydrogen stream and/or external hydrogen, and the material obtained after hydrogenation is rectified by ethylene rectification tower 22 to form ethylene products. In the above structure, the separated hydrogen can be rationally utilized, the consumption of external hydrogen for acetylene hydrogenation is reduced, and the cost of acetylene hydrogenation is saved. In addition, when the pressure swing adsorption system 122 adopts the second connection mode, the high-purity hydrogen flow generated by the pressure swing adsorption system 122 can also be led out of the olefin separation device for other processes.

As shown in Figure 2, the olefin separation unit also includes a deethanizer unit and a propylene rectification unit, and the deethanizer unit includes a deethanizer 31, and the deethanizer 31 has a first liquid phase stream inlet and a deethanizer tower The top stream outlet has a first liquid phase stream pipeline between the first liquid phase stream inlet and the third tower bottom outlet of the initial demethanizer 11; There is a hydrocarbon deykyne material delivery pipeline between the material inlets; the propylene rectification unit includes a propylene rectification tower 41 and a tower top reflux tank 42, and the propylene rectification tower 41 has a third liquid phase stream inlet and a tower top propylene outlet, and the second There is a third liquid-phase flow line between the three-liquid-phase flow inlet and the outlet at the bottom of the deethanizer 31; the top reflux tank 42 is connected with the top propylene outlet of the propylene rectification tower 41 and is connected with the propylene rectification tower 41 Constituting the third circulation line, the first reboiler 191 or the second reboiler 192 has a propylene inlet and a propylene outlet communicating with the third circulation line.

In the above-mentioned olefin separation device, the ethylene mixed gas with ethylene as the main component formed after the first liquid phase stream separated from the primary demethanizer 11 is processed by the deethanizer 31 can be used as the inlet of the hydrodeacetylation reactor 21. to remove a small amount of acetylenic organic matter therein; at the same time, because the second liquid phase stream separated by the secondary demethanizer 17 is almost all carbon distillates, so this stream does not need to enter the deethanizer 31, only primary demethanizer The first liquid phase stream containing carbon 2 and carbon 3 components in tower 11 enters the deethanizer 31 for separation, thereby greatly reducing the load on the deethanizer 31 and helping to reduce the energy consumption and investment of the deethanizer 31 Expense; The third liquid-phase stream based on propylene separated by the deethanizer 31 enters the propylene rectification tower 41 for rectification, and the top propylene product obtained after rectification enters the first reboiler 191 or the second reboiler 191 of the demethanizer unit. The reboiler 192 exchanges heat with the first liquid-phase stream and then lowers the temperature. At the same time, the heat of the propylene product at the top of the tower is absorbed by the first liquid-phase stream. And with the liquid phase stream left by the top of the tower, the reverse contact mass transfer is achieved to achieve the purpose of cryogenic rectification, so that the top propylene product is used to replace the hot steam and the first liquid phase stream in the first reboiler 191 or the second reboiler 191 Heat exchange is carried out in the boiler 192, which makes full use of the remaining heat and cold capacity in the system, reduces the consumption of hot steam and water, saves energy consumption and water resources, and saves the use of cooling water and the overhead water cooler. equipment investment. The cooled top propylene product passes through a product protection bed and other devices to remove a small amount of methanol, oxides and other impurities to obtain a qualified propylene product

In order to effectively control the heat exchange of the overhead propylene product and adjust the operation (such as operating temperature) of the initial demethanizer 11, as shown in Figure 2, on the third circulation line between the propylene rectifying tower 41 and the overhead reflux tank 42 A control valve 43 is also provided, and the control valve 43 is arranged in parallel with the first reboiler 191 or the second reboiler 192 to regulate the amount of propylene product flowing through the first reboiler 191 or the second reboiler 192 .

As shown in Figure 2, the olefin separation device also includes a second cold box 142, the second cold box 142 has a second gas-phase liquid flow in the second cold box flow path, the second gas-phase liquid flow in the second cold box flow path and the first cold box flow path The second gas flow of the second heat exchanger 152 is communicated with the flow path in the second heat exchanger; there are two fourth liquid-phase flow pipelines between the propylene rectification tower 41 and the second cold box 142, one of which is the fourth The liquid-phase logistics pipeline passes through the second cold box 142 and communicates with the gas pipeline network; another fourth liquid-phase logistics pipeline passes through the second cold box 142 and extends to communicate with the primary demethanizer 11, and the olefin separation device also The second refrigerant chiller 162 is included, and the second refrigerant chiller 162 is arranged on the fourth liquid phase stream line between the second cold box 142 and the primary demethanizer 11 .

In the above-mentioned olefin separation device, the second gas phase stream from the secondary demethanizer 17 is expanded and cooled by the expander 18, and the hydrocarbon-rich gas stream passing through the second heat exchanger 152 is cooled in the second cold box 142 as a cooling The medium cools the fourth liquid phase stream. On the one hand, the temperature of the second gas phase stream rises after heat exchange and is sent out of the olefin separation device for use as fuel; The cooler 162 enters the top part of the primary demethanizer 11 after further quenching to absorb the ethylene in the first gas phase stream at the top of the primary demethanizer 11, and another part of the fourth liquid phase stream can be sent to the gas pipeline network Used as gas.

As shown in Figure 2, the olefin separation unit also includes a depropanization unit and a debutanization unit, and the depropanization unit includes a depropanization tower 51, a drier 52, a second compressor 132 and a third refrigerant chiller 163, and the depropanization unit A primary degassing phase stream line is arranged between the tower top outlet of the tower 51 and the primary demethanizer 11; the drier 52 is connected with the inlet of the depropanizer 51 and leads to the depropanizer 51 to deliver the raw material gas to be separated; the second compressor 132 Be arranged on the initial degassed phase stream line between the depropanizer 51 and the initial demethanizer 11; the third refrigerant chiller 163 is arranged on the initial degassed phase stream between the second compressor 132 and the initial demethanizer 11 On the pipeline, the first cold box 141 has the first degassed phase stream inlet and the first degassed phase stream outlet communicated with the first degassed phase stream pipeline between the second compressor 132 and the third refrigerant chiller 163; The unit comprises a debutanizer 61 and a tower top condenser 62, and an initial liquid phase stream line is arranged between the debutanizer 61 and the depropanizer 51; The outlet is connected to the inlet and the outlet for the condensed product to flow out.

In order to meet the better separation of gases such as petroleum cracking gas with complex components, refinery dry gas, and methanol-to-olefin product gas, a depropanization unit and a debutanization unit are set in the above-mentioned olefin separation device, and the depropanizer 51 is used to separate the C4 hydrocarbons and hydrocarbons above C4 in the gas to be separated are separated from C3 hydrocarbons and hydrocarbons below C3 to form an initial degassed phase stream containing C3 hydrocarbons and hydrocarbons below C3 and hydrocarbons containing C4 And the initial liquid phase stream of hydrocarbons with carbon four or more. Wherein the first degassed phase stream enters the above-mentioned demethanizer unit for separation and treatment, and the first degassed phase stream is separated from the first demethanizer 11 in the first cold box 141 before entering the first demethanizer 11 The heat exchange of the gas phase stream and the heat exchange with the refrigerant in the third refrigerant chiller 163 results in a large degree of temperature reduction, thus reducing the energy consumption of the primary demethanizer 11 for cryogenic separation. Among them, the initial liquid-phase stream enters the debutanizer 61 for separation to obtain C4 products and C5 products, which realizes sufficient and detailed separation of the raw material gas and is beneficial to the utilization of the raw material gas.

According to another typical embodiment of the present invention, a method for separating olefins is also provided, the method for separating olefins includes a process of separating a mixed gas whose main components are hydrogen, C3 hydrocarbons and hydrocarbons below C3, the process Including the initial demethanization process, membrane separation process, pressure swing adsorption process and secondary demethanization process, the initial demethanization process includes the mixed gas in the initial demethanization process. Phase stream, the first gas phase stream includes hydrogen, methane and carbon two hydrocarbons, the first liquid phase stream includes carbon two hydrocarbons and carbon three hydrocarbons; the membrane separation process includes making the first gas phase stream undergo membrane separation to obtain the second phase of mutual separation A hydrocarbon-rich gas stream and a first hydrogen-rich gas stream; the pressure swing adsorption process adopts the following method, mode 1: the first hydrocarbon-rich gas stream is subjected to pressure swing adsorption to obtain a second hydrocarbon-rich gas stream and a second hydrogen-rich gas stream separated from each other, mode 2 : the first hydrogen-rich gas stream is subjected to pressure swing adsorption to obtain a high-purity hydrogen gas stream and a third hydrocarbon-rich gas stream; the secondary demethanization process includes making the first hydrocarbon-rich gas stream in mode one or the first hydrocarbon-rich gas stream in mode two and the third hydrocarbon-rich gas stream are clearly cut during the sub-demethanization process to obtain a second gas phase stream and a second liquid phase stream.

The above-mentioned olefin separation method adopts the non-clear cutting method at the top of the primary demethanizer 11 to replace the currently commonly used clear cutting method, which reduces the cooling load and heat load required in the primary demethanization separation process and reduces energy consumption. Taking the primary demethanizer 11 and the secondary demethanizer 17 as examples to illustrate the above olefin separation method, the so-called non-clear cut means that the content of carbon dihydrocarbons in the top component of the primary demethanizer 11 does not need to be clearly cut Instead, a part of the carbon dihydrocarbons of the initial demethanizer 11 is separated as the first gas phase stream together with the light components at the top of the tower, while another part of the carbon dihydrocarbons and the carbon trihydrocarbons are used as the first gas phase stream. The liquid stream is separated from the bottom of the tower, so that the first gas stream of the tower does not contain carbon three and hydrocarbons above carbon three, so that the volume of the lost carbon three hydrocarbons in the initial demethanizer 11 accounts for 0.01% of the total volume of carbon three % or less, those skilled in the art can select an appropriate non-clear cutting temperature and pressure according to the withstand temperature and pressure of the device. The membrane separation process adopted in the above olefin separation method effectively separates the hydrogen of the hydrocarbons in the first gas phase stream to obtain the first hydrocarbon-rich gas stream and the first hydrogen-rich gas stream, wherein the separation membrane that can be used in the present invention includes but is not limited to polyetheramide Separation membrane of imine material; then use the pressure swing adsorption process to further carry out adsorption separation of the first hydrocarbon-rich gas flow to obtain the second hydrocarbon-rich gas flow and the second hydrogen-rich gas flow, or use the pressure swing adsorption process to further separate the first hydrogen-rich gas flow The high-purity hydrogen gas flow and the third hydrocarbon-rich gas flow are obtained through adsorption separation, wherein the adsorbents that can be used in the present invention include but not limited to activated carbon adsorbents, activated alumina and the like. Compared with the CH ₄ /H ₂ molecular ratio in the first hydrocarbon-rich gas stream obtained by membrane separation, the second hydrocarbon-rich gas stream separated by pressure swing adsorption, and the third hydrocarbon-rich gas stream compared with the CH ₄ in the first hydrocarbon-rich gas stream obtained by membrane separation /H _The molecular ratio is further increased, and then the partial pressure of CH at the top of the secondary demethanizer ₁₇ is increased, so it is only necessary to reduce the temperature of the secondary demethanizer ₁₇ to a higher dew point to separate CH and H ₂ , then the required energy consumption for cooling in the separation process is reduced; and, due to the increase of the dew point, there is little or no ethylene in the second gas phase stream separated from the top of the secondary demethanizer 17, and the second liquid phase There is no hydrogen and methane in the stream, so the loss of ethylene is reduced; at the same time, the realization of the above technical effects can greatly reduce the investment in olefin separation.

In another preferred embodiment of the present invention, the first gas phase stream obtained in the initial demethanization process contains carbon dihydrocarbons with a volume percentage of 15-90%; The volume percentage is 75-95%, and the volume of hydrogen in the hydrogen-rich gas stream accounts for 45-65% of the total volume of hydrogen in the first gas phase stream; The volume percentage of hydrogen in the medium is 85-99.99%; the volume content of ethylene in the second gas phase stream obtained from the secondary demethanization process is ≤2%. Those skilled in the art can select a reasonable pressure and temperature according to the composition of the feed gas to be processed and the device used to obtain the expected results of non-clear cut, pressure swing adsorption and clear cut, which is beneficial to the product obtained by the entire olefin separation method. control.

In order to rationally use the heat and cold produced in the separation process, the above-mentioned process of separating the main components of hydrogen, carbon three hydrocarbons and the mixed gas of hydrocarbons below carbon three also includes making the mixed gas pass through sequentially and the gas obtained by non-clear cutting. The first gaseous stream undergoes heat exchange and heat exchange with the refrigerant, and then performs the initial demethanization process; the first hydrocarbon-rich gas stream in mode 1 or the first hydrocarbon-rich gas stream and the third hydrocarbon-rich gas stream in mode 2 are sequentially compressed Treatment, heat exchange with the first gas phase stream separated from the primary demethanization process, heat exchange with the second liquid phase stream separated from the secondary demethanization process, and the second gas phase stream separated from the secondary demethanization process After the heat exchange, the secondary demethanization process is carried out; the second gas phase stream separated from the secondary demethanization process is expanded and cooled before heat exchange with the second hydrocarbon-rich gas; Reheating and boiling are repeated for the initial demethanization process.

In the olefin separation process, heat exchange is performed between the mixed gas to be separated and the lower temperature first gas phase stream separated in the initial demethanization process, and the hydrocarbon-rich gas stream is mixed with the first gas phase, the second liquid phase and the second gas phase The heat exchange of the stream is carried out by using the heat difference in the separation steps in the separation process, and the purpose of expanding and cooling the second gas phase stream separated from the secondary demethanization is to recover more cooling capacity , so the input of external cooling medium can be reduced, and the cost of separation can be saved.

In yet another preferred embodiment of the present invention, the above-mentioned olefin separation method further includes gradually compressing the raw material gas to be separated to obtain a suitable separation temperature after depropanization treatment; performing deethanization treatment on part of the first liquid phase stream to obtain Deethanizer overhead stream and the third liquid phase stream; when the pressure swing adsorption process adopts mode one, make the deethanizer overhead stream and the first hydrogen-rich gas stream and/or the second hydrogen-rich gas stream and/or external hydrogen Hydrodeacetylation reaction is carried out to obtain the ethylene-containing mixture after deacetylation. When the pressure swing adsorption process adopts mode 2, the overhead stream of the deethanizer is subjected to hydrodeacetylation with high-purity hydrogen flow and/or external hydrogen. Reaction to obtain the ethylene-containing mixture after deacetylation; the rectification of the ethylene-containing mixture to obtain ethylene products; the rectification of the third liquid phase stream to obtain the fourth gas phase stream and the fourth liquid phase stream, so that the fourth gas phase stream and part of the first After the heat exchange of the liquid phase stream, it is further treated to remove impurities to form a propylene product; after the heat exchange between the fourth liquid phase stream and the second gas phase stream, a part of the heat exchanged fourth liquid phase stream and the refrigerant are further used for heat exchange In the process of absorbing the initial demethanization process, the ethylene in the gas phase material to form the first gas phase stream is absorbed, and another part of the heat exchanged fourth liquid phase stream is transported as gas. The purpose of depropanizing the raw gas to be separated and then compressing it is to obtain a mixed gas with a suitable separation temperature.

The feed gas to be separated that can be used in the present invention includes but is not limited to petroleum cracking gas, refinery dry gas, methanol-to-olefin product gas, and utilizes the first hydrogen-rich gas stream and the second hydrogen-rich gas stream separated from the feed gas as acetylene addition The hydrogen source for the hydrogen reaction reduces the amount of external hydrogen and saves the cost of ethylene synthesis. Moreover, the first gas phase stream formed by the non-clear cut of the initial demethanization process does not contain C3 and hydrocarbons above C3, so only the first liquid phase stream needs to be deethanized, so that the deethanized process The energy consumption and load of the deethanizer will be reduced, and the investment and operation cost of the deethanizer can be reduced accordingly.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. an olefin separation, described olefin separation comprises demethanation unit, it is characterized in that, described demethanation unit comprises just demethanizing tower (11), membrane separation assemblies (121), pressure swing adsorption system (122) and time demethanizing tower (17)

The first gaseous stream pipeline is provided with between the tower top outlet of described just demethanizing tower (11) and the import of described membrane separation assemblies (121); And

The mode of connection of described pressure swing adsorption system (122) adopts one of following:

Mode of connection one: the rich hydrocarbon stream outlet of described membrane separation assemblies (121) is connected with the import of described pressure swing adsorption system (122), is provided with rich hydrocarbon stream pipeline between the rich hydrocarbon stream outlet of described pressure swing adsorption system (122) and the import of described demethanizing tower (17); Or

Mode of connection two: the hydrogen rich stream outlet of described membrane separation assemblies (121) is connected with the import of described pressure swing adsorption system (122), the rich hydrocarbon stream outlet of described membrane separation assemblies (121) and the rich hydrocarbon stream of described pressure swing adsorption system (122) export and be provided with rich hydrocarbon stream pipeline between the imports of described demethanizing tower (17);

Described demethanation unit also comprises the first compressor (131), the first ice chest (141), First Heat Exchanger (151), the second interchanger (152), the first cryogen chiller (161) and decompressor (18)

Between the tower top outlet of described demethanizing tower (17) and the import of described decompressor (18), there is the second gaseous stream pipeline;

Described first compressor (131) is arranged on described rich hydrocarbon stream pipeline;

Described first ice chest (141) has:

Stream in first gaseous stream first ice chest, is serially connected in described first gaseous stream pipeline;

Stream in rich hydrocarbon stream first ice chest, is serially connected in the rich hydrocarbon stream pipeline between described first compressor (131) and the import of described demethanizing tower (17);

Described First Heat Exchanger (151) has:

Stream in rich hydrocarbon stream First Heat Exchanger, is serially connected in the described rich hydrocarbon stream pipeline in described rich hydrocarbon stream first ice chest between stream and the import of described demethanizing tower (17);

Stream in second liquid phase logistics First Heat Exchanger, is connected with the tower bottom outlet of described demethanizing tower (17);

Described second interchanger (152) has:

Stream in rich hydrocarbon stream second interchanger, in the described rich hydrocarbon stream pipeline between the import being serially connected in stream and described demethanizing tower (17) in rich hydrocarbon stream First Heat Exchanger;

Stream in second gaseous stream second interchanger, is connected with the outlet of described decompressor (18);

Described first cryogen chiller (161) to be arranged in described rich hydrocarbon stream second interchanger between stream and the import of described demethanizing tower (17).

2. olefin separation according to claim 1, is characterized in that, described demethanation unit also comprises:

First reboiler (191), is connected with the first tower bottom outlet of described just demethanizing tower (11) and is connected to form the first circulation line with the tower reactor of described just demethanizing tower (11);

Second reboiler (192), is connected with the second tower bottom outlet of described just demethanizing tower (11) and is connected to form the second circulation line with the tower reactor of described just demethanizing tower (11).

3. olefin separation according to claim 2, is characterized in that, described olefin separation also comprises ethylene distillation unit, and described ethylene distillation unit comprises:

Hydrogenation acetylene removal reactor (21), has:

Hydrogen gas stream import, when described pressure swing adsorption system (122) adopts mode of connection for the moment, the hydrogen rich stream of described hydrogen gas stream import and described pressure swing adsorption system (122) exports and the hydrogen rich stream of described membrane separation assemblies (121) export between there is hydrogen rich stream pipeline, when described pressure swing adsorption system (122) adopts mode of connection two, between the high-purity hydrogen spout of described hydrogen gas stream import and described pressure swing adsorption system (122), there is High Purity Hydrogen flow line, and described High Purity Hydrogen flow line is provided with flow control valve;

Hydrocarbon material import, and between the tower bottom outlet of described demethanizing tower (17), there is second liquid phase logistic pipeline;

Ethylene product exports;

Ethylene rectification tower (22), exports with described ethylene product and is connected.

4. olefin separation according to claim 3, is characterized in that, described olefin separation also comprises deethanizing unit and propylene rectification cell,

Described deethanizing unit comprises deethanizing column (31), and described deethanizing column (31) has:

First liquid phase stream import, and between the 3rd tower bottom outlet of described just demethanizing tower (11), there is the first liquid phase stream pipeline;

Deethanizer overhead stream exports, and has hydro carbons acetylene removal Location Detection of Medium Transportation Pipeline between the hydrocarbon material import of described hydrogenation acetylene removal reactor (21);

Described propylene rectification cell comprises:

Propylene rectification tower (41), has:

3rd liquid phase stream import, and between the tower bottom outlet of described deethanizing column (31), there is the 3rd liquid phase stream pipeline;

Tower top propylene exports;

Return tank of top of the tower (42), export with the tower top propylene of described propylene rectification tower (41) and be connected and form the 3rd circulation line with described propylene rectification tower (41), described first reboiler (191) or the second reboiler (192) have the propylene import that is connected with described 3rd circulation line and propylene exports.

5. olefin separation according to claim 4, it is characterized in that, described 3rd circulation line between described propylene rectification tower (41) and described return tank of top of the tower (42) is also provided with control valve (43), and described control valve (43) is arranged in parallel with described first reboiler (191) or the second reboiler (192).

6. olefin separation according to claim 4, is characterized in that, described olefin separation also comprises the second ice chest (142),

Described second ice chest (142) has stream in the second gas phase liquid stream second ice chest, and in described second gas phase liquid stream second ice chest, stream is connected with stream in the second gaseous stream second interchanger of described second interchanger (152);

There is between described propylene rectification tower (41) and described second ice chest (142) two article of the 4th liquid phase stream pipeline,

One article of the 4th liquid phase stream pipeline is wherein connected with gas ductwork afterwards through described second ice chest (142);

Another article the 4th liquid phase stream pipeline is connected with described just demethanizing tower (11) through extending to after described second ice chest (142), described olefin separation also comprises the second cryogen chiller (162), and described second cryogen chiller (162) is arranged on described second ice chest (142) and described the 4th liquid phase stream pipeline just between demethanizing tower (11).

7. olefin separation according to claim 6, is characterized in that, described olefin separation also comprises:

Depropanizing unit, comprising:

Depropanizing tower (51), tower top outlet and described being just provided with between demethanizing tower (11) of described depropanizing tower (51) just take off gaseous stream pipeline;

Moisture eliminator (52), is connected with the import of described depropanizing tower (51) to described depropanizing tower (51) and carries unstripped gas to be separated;

Second compressor (132), is arranged on described depropanizing tower (51) and described described just de-gaseous stream pipeline just between demethanizing tower (11);

3rd cryogen chiller (163), be arranged on described second compressor (132) and described described just de-gaseous stream pipeline just between demethanizing tower (11), described first ice chest (141) has the first degassed phases be connected with the described first de-gaseous stream pipeline between described second compressor (132) with described 3rd cryogen chiller (163) and flows to mouth and first degassed phase stream outlet;

Debutylize unit, comprising:

Debutanizing tower (61), and between described depropanizing tower (51), be provided with just de-liquid phase stream pipeline;

Overhead condenser (62), has the import be connected with the tower top outlet of described debutanizing tower (61) and the outlet of flowing out for condensation after product.

8. an alkene separation method, is characterized in that, described alkene separation method comprises the process that separation main component is the gas mixture of hydrogen and carbon less than three hydro carbons, and described process comprises:

First demethanizing process: described gas mixture is carried out in described just demethanizing process the first gaseous stream that non-clear cutting obtains being separated from each other and the first liquid phase stream, described first gaseous stream comprises hydrogen, methane and C2 hydrocarbon class, and described first liquid phase stream comprises C2 hydrocarbon class and carbon three hydro carbons;

Membrane separating process: described first gaseous stream is carried out the first rich hydrocarbon stream that membrane sepn obtains being separated from each other and the first hydrogen rich stream;

Pressure-swing adsorption process, in the following ways:

Mode one: described first rich hydrocarbon stream is carried out the second rich hydrocarbon stream that pressure-variable adsorption obtains being separated from each other and the second hydrogen rich stream;

Mode two: make described first hydrogen rich stream carry out pressure-variable adsorption and obtain High Purity Hydrogen air-flow and the 3rd rich hydrocarbon stream;

Secondary demethanizing process: the first rich hydrocarbon stream in described mode one or the first rich hydrocarbon stream in described mode two and the 3rd rich hydrocarbon stream are carried out in described demethanizing the second gaseous stream that clear cutting obtains being separated from each other and second liquid phase logistics; Wherein, described process also comprises:

Described gas mixture is made after carrying out heat exchange with the first gaseous stream obtained by described non-clear cutting, carrying out heat exchange with cryogen, to carry out just demethanizing process successively;

Make the first rich hydrocarbon stream in described mode one or the first rich hydrocarbon stream in described mode two and the 3rd rich hydrocarbon stream successively through processed compressed, with undertaken by described just isolated first gaseous stream of demethanizing process heat exchange, with undertaken by the logistics of described demethanizing isolated second liquid phase heat exchange, with carry out heat exchange by isolated second gaseous stream of described demethanizing after carry out described demethanizing process;

Carry out expansion before making to carry out heat exchange by isolated second gaseous stream of described demethanizing and described second rich appropriate hydrocarbon gas to lower the temperature;

Described just demethanizing process is repeated through reheating boiling after described first liquid phase stream of part is separated by described just demethanizing process.

9. alkene separation method according to claim 8, is characterized in that,

Be the described C2 hydrocarbon class of 15 ~ 90% containing volume percent in described first gaseous stream that described just demethanizing process obtains;

In described first hydrogen rich stream that described membrane separating process obtains, the volume percent of hydrogen is 75 ~ 95%, and in described hydrogen rich stream, the volume of hydrogen accounts for 45 ~ 65% of hydrogen cumulative volume in described first gaseous stream,

When described pressure-swing adsorption process adopts mode for the moment, in described second hydrogen rich stream that described pressure-swing adsorption process obtains, the volume percent of hydrogen is 85 ~ 99.99%;

Volume content≤2% of ethene in described second gaseous stream that described demethanizing process obtains.

10. alkene separation method according to claim 8, is characterized in that, described alkene separation method also comprises:

Compress to form described gas mixture after making unstripped gas to be separated carry out depropanizing process;

Make described first liquid phase stream of part carry out deethanizing process and obtain deethanizer overhead stream and the 3rd liquid phase stream;

When described pressure-swing adsorption process adopts mode for the moment, make described deethanizer overhead stream and described first hydrogen rich stream and/or the second hydrogen rich stream and/or external hydrogen carry out hydrogenation acetylene removal react after acetylene removal containing mixture of ethylene, when described pressure-swing adsorption process adopts mode two, make described deethanizer overhead stream and described High Purity Hydrogen air-flow and/or external hydrogen carry out hydrogenation acetylene removal and react contain mixture of ethylene after acetylene removal;

Ethylene product is obtained containing mixture of ethylene rectifying by described;

Described 3rd liquid phase stream rectifying is obtained the 4th gaseous stream and the 4th liquid phase phase logistics, after making described 4th gaseous stream and the described first liquid phase stream heat exchange of part, form propylene product through further removal of impurity process;

After making described 4th liquid phase stream and described second gaseous stream carry out heat exchange, be used for after described 4th liquid phase stream after a part of heat exchange and cryogen are carried out heat exchange further absorbing for forming the ethene in the gaseous substance of described first gaseous stream in described just demethanizing process, using described 4th liquid phase stream after another part heat exchange as fuel gas transmission.