CN102451653B - Micro reaction method for realizing efficient absorption of acid gas - Google Patents

Abstract

A micro-reaction method capable of realizing high-efficiency absorption of acid gas provides a micro-reaction technology method capable of intensifying the absorption process of acid gas (CO ₂ , H ₂ S, SO ₂ , SO ₃ , HCl, etc.). The method adopts a micro-reactor, and the acid gas to be absorbed and the absorption liquid flow through the micro-reactor under a reaction pressure of 0.1-7MPa, and stay in the parallel micro-reaction channel for 0.001-10 seconds to complete the absorption. The parallel micro-reaction channel at least includes a row of micropores, and the acid gas flowing through the microreactor is contacted and mixed with the absorption liquid through the micropores on the microchannel; the gas-liquid two-phase fluid after contacting and mixing is at least Experience a zigzag or curved flow. The invention can strengthen the chemical absorption process of the acid gas mixture within millisecond-level material residence time, and is a micro-reaction technology capable of realizing rapid production scale-up.

Description

A Microreaction Method for Efficient Absorption of Acid Gases

technical field

The invention relates to a micro-reaction technology capable of realizing high-efficiency absorption of acid gas, in particular to a micro-channel reactor technology capable of strengthening acid gas absorption. The invention provides a high-efficiency absorption micro-reactor technology for the decarbonization and desulfurization of flue gas, synthetic ammonia, natural gas chemical industry and other industrial gases. the

Background technique

Acid gas emissions, especially CO ₂ , H ₂ S and other gases, have had a serious impact on the global climate and environment. As of December 2009, 184 countries around the world have signed the " Kyoto Protocol, it can be seen that the reduction of greenhouse gas emissions is of great significance, and the separation and absorption of CO ₂ from concentrated emission sources such as the tail gas of coal-fired power plants is the most operational emission reduction method. Industrial gases such as synthetic ammonia (using natural gas as raw material) and natural gas chemical industry contain a large amount of acid gas, and removing the acid gas to purify the raw gas is a necessary part of these large-scale installations.

At present, the acid gas purification is mainly based on the chemical absorption method with activated MDEA as the solvent, and the purification device generally uses a packed tower as the absorption tower. The biggest disadvantage of the packed tower is that it is prone to liquid flooding, mist entrainment and tower corrosion, as well as the low capacity of the tower equipment per unit volume. the

Patent CN101612510A discloses a microchannel absorber for absorbing _CO2 , which replaces the filler on the conventional absorption tower with a regular microchannel similar to honeycomb, which improves the processing capacity of the equipment. US patent US20100024645 relates to a method of using ionic liquid as an absorbent to separate gases in a microchannel, and a way to improve thermal efficiency—using the heat of absorption reaction for the desorption process to reduce additional energy. US20060073080 discusses the multiphase mixing in the microchannel mixer, through the holes on the microchannel, one of the two phases forms a discontinuous phase in the microchannel and disperses in the continuous phase to obtain a higher gas-liquid phase contact area .

In the microchannel reactors involved in the above-mentioned patents, the regular microchannel absorber uses spray dispersion to realize the mixing of gas-liquid two-phase fluids. Although it is more efficient than conventional tower reactors, it cannot guarantee the gas-liquid flow in each channel. The ratio of the two phases is uniform, resulting in a decrease in absorption efficiency. From the disclosed content, this kind of regular microchannel will become the main constraint factor for its large-scale application in terms of material selection and preparation, that is, it is difficult to meet the requirements of large-scale production. Requirements; Patent US20100024645 emphasizes the energy utilization of the microchannel separation system, while US20060073080 only strengthens mixing from the pore size or the length of the pore extension, and also involves heat exchange with the microchannel heat sink, but for this pore distribution and microchannel The study of structural synergistically enhanced mass transfer has not involved, or at least has not disclosed, the geometrical characteristics of microreactors for synergistically enhanced mass transfer. the

Contents of the invention

The purpose of the invention is to strengthen the gas-liquid two-phase mixing in the microchannel, especially the two-phase reaction process involving acid gas chemical absorption. The invention strengthens this mass transfer process through the synergistic effect of the pore distribution on the microchannel and the structure of the microchannel. the

To achieve the above object, the technical solution adopted in the present invention is:

A micro-reaction method capable of realizing high-efficiency absorption of acid gas. The method adopts a micro-reactor, and the acid gas to be absorbed or its mixture and the absorption liquid flow through the micro-reactor under a reaction pressure of 0.1-7 MPa, and the Stay in the parallel micro-reaction channel in the micro-reactor for 0.001-10 seconds to complete the absorption;

The microreactor comprises one or more micro-mixing plates and one or more micro-distribution plates, the micro-mixing plate and the micro-distribution plate are stacked; each micro-mixing plate is provided with a parallel micro-reaction channel, and each A micro-reaction channel contains one or more micro-holes perpendicular to the direction of the plate surface; each micro-distribution plate is provided with parallel distributed micro-channels that correspond to and communicate with the above-mentioned micro-holes; The acid gas or its mixture and the absorption liquid in the reactor flow through the micro-distribution plate and the micro-mixing plate respectively, and contact through the micro-holes on the micro-channel; the gas-liquid two-phase fluid after contacting and mixing occurs at least one zigzag flow in the micro-channel and/or at least one curved flow. the

In the method provided by the invention, the micropores between the parallel microreaction channels are regularly distributed in rows, and contain at least one row of micropores; the parallel microreaction channels containing at least one row of holes constitute absorption liquid or acid gas channels, and two or the mixed mixing plate (M plate), i.e. the micro-mixing plate; and the micro-distribution plate does not contain micropores, only includes parallel distribution micro-channels, or the distribution plate (D plate) for short, by such One piece of micro-mixing plate and one piece of micro-distribution plate can form a small micro-reactor, and the above-mentioned multi-piece micro-mixing plate and micro-distribution plate can form a parallel enlarged micro-reactor. During assembly, each or more mixing plates are interposed between two adjacent distribution plates, and each or two micro-distribution plates are interposed between two adjacent micro-mixing plates. The number of parallel distributed microchannels on the microdistribution plate is the same as that of the single row of holes on the micromixing plate; and the distribution channel extends to a row of holes on the micromixing plate near the axial tail of the parallel microreaction channel. the

In a preferred embodiment, the parallel micro-reaction channels include multiple rows of regular micro-holes in the axial direction, and the position of the last row of micro-holes is within the first row of micro-holes (at the material inlet) to the center of the channel. The parallel microchannels on each micro-mixing plate and micro-distribution plate that constitute the microreactor contain walls (the walls mentioned in the present invention do not include the ribs between the parallel channels on the monolithic plate, which can be understood as the bottom surface of the parallel channels ), the micro-mixing plate arranged alternately and the parallel micro-channel on the micro-distribution plate are separated by a wall, the single row of holes or multiple rows of holes on the parallel micro-channel are located on the wall, and the parallel micro-reaction channel and the parallel distribution micro-channel pass through The micropores on the wall are connected. the

In order to produce a synergistically enhanced two-phase mass transfer effect, the present invention makes the channel on the micro-mixing plate into a curved or broken line structure in the entire axial direction, and the bending angle or folding angle is 10°-150°, preferably 45°-120° °, the preferred implementation is 30° or 45° or 90° or 120° or 150° or other angles. And the matching micropore distribution is: when the bending angle or kink angle of the microchannel is 45° and below, the spacing _l1 between two adjacent rows of holes is greater than or equal to the spacing _l2 between two adjacent bending angles or knuckle tops 2 times, that is, l ₁ ≥ 2l ₂ , when the microchannel bending angle or kink angle is >45°-90°, 2l ₂ >l ₁ >l ₂ , when the microchannel fold line or curve angle is above 90°, l ₁ = l ₂ .

In the microreactor of the present invention having the above-mentioned characteristics, the acid gas to be absorbed or its mixture is contacted and mixed with the absorption liquid through micropores or rows of micropores, in parallel microreaction channels with specific curves or broken line angles Complete mixed absorption, that is, one of the gas-liquid two-phase fluids forms a small branch flow through parallel distributed microchannels, and enters multiple small branch flows of another component through micropores. In order to prevent the branch flow of a certain fluid from entering the microreaction channel Before the flow break, a plurality of micropores are set near the inlet of the microreaction channel, and the channels are distributed in parallel to form multiple rows of micropores; the multi-branch flow of the two-phase fluid mixed at the micropores is further formed in a curved or knuckle The absorption is enhanced in parallel micro-reaction channels and maintained for a period of time. the

The micro-reaction technology method for strengthening _CO2 absorption provided by the present invention also includes, making the residence time of the acid gas to be absorbed and its mixture and the absorption liquid in the microreactor be 0.001-10 seconds, preferably the material residence time is 0.01 -0.5 seconds, the reaction pressure is 0.1-7MPa, preferably 1.0-5.0MPa. The acid gas or its mixture to be absorbed comes from industrial gases such as coal-fired boiler flue gas or natural gas. The acid gas can be CO ₂ , H ₂ S, SO ₂ , SO ₃ , or HCl. It is organic amines or their composite components or organic amines with activators added, or ionic liquid absorbent and its composite components, or the composite components of organic amines and ionic liquids. The absorption liquid is a technology well known to those skilled in the art, and it is under continuous development and improvement. The purpose of the present invention is to provide microreactor technology that can realize the efficient absorption of acid gas, and the absorption in various known absorption liquid systems The process can be further strengthened by the method of the present invention.

The microreactor technology of the present invention can strengthen acid gas chemical absorption, and for the decarburization process of alcohol amine chemical absorption, under the conditions of residence time of only 0.01-0.5 seconds and reaction pressure of 0.1-5MPa, the removal rate of high-concentration _CO2 can be generally high More than 90%, the highest can reach more than 99.5%.

Description of drawings

Figure 1 is a diagram of micro-reaction channel structure and pore distribution at different broken line angles;

Figure 2 is a microchannel structure and hole distribution diagram with curves at different angles;

Fig. 3 is a monolithic view of a 30° angle curve microchannel structure;

Fig. 4 is a distribution channel corresponding to Fig. 3 or a schematic diagram of its plate structure;

Fig. 5 is the combination form of micro-mixing plate M and micro-distribution plate D of the present invention;

Fig. 6 is a two-phase mixing view in the microchannel structure of the 30 ° angle curve (mixing channel and distribution channel overlay);

Among accompanying drawings 1-6, label M represents micro-mixing (passage or plate), and D represents micro-distribution (passage or plate, and P represents micropore, and W represents channel wall, and A and B represent gas-liquid two-phase fluid;

Fig. 7 is that DEA absorbs _CO in the microreactor of the present invention Reaction result one;

Fig. 8 is the second result of DEA absorbing CO ₂ reaction in the microreactor of the present invention.

Detailed ways

The specific embodiment of the present invention will be described in detail in conjunction with the technical solution. the

The present invention is comparatively familiar to those skilled in the art of microreactor or microchemical industry: at first what the present invention relates to is a microchannel reactor, that is, the channel characteristic equivalent size is micron to millimeter order, secondly what relates to is the microchannel in the microchannel Gas-liquid two-phase mixed mass transfer process. The difference is that the present invention provides a different microchannel structural feature to strengthen the gas-liquid two-phase mass transfer in the microchannel, especially the reactor technology for acid gas absorption reaction. the

The microreactor comprises at least one or more micro-mixing plates and at least one or more micro-distribution plates stacked on each other; and each micro-mixing plate is provided with parallel micro-reaction channels; each micro-mixing plate on the micro-mixing plate The reaction channel is provided with one or more holes perpendicular to the direction of the plate surface, and the micro-distribution plate is provided with channels corresponding to the above-mentioned holes and communicated with each other; the acid gas flowing through the micro-reactor or The mixture and the absorption liquid flow through the micro-distribution plate and the micro-mixing plate respectively, and contact through the holes on the micro-channel; the gas-liquid two-phase fluid after contacting and mixing occurs at least one zigzag flow and/or at least one curved flow in the micro-channel . the

The structure of the microreactor for the efficient absorption of acid gas of the present invention is shown in accompanying drawing 1 and accompanying drawing 2. As shown in Figure 1, the parallel micro-reaction channels are made into folded line structures M ₁ , M ₂ , M ₃ , M ₄ , M ₅ , M ₆ , and the corresponding fold angles are 30°, 45°, 60°, 90°, 120°, 150°. Figure 2 shows micro-reaction channels M ₀ ', M ₁ ', M ₂ ', M ₃ ', M ₄ , M ₅ , M ₆ with curved surface structures, and the angles of the corresponding curves are 0°, 30°, 45°, 60°, 90°, 120°, 150°. Multiple rows of holes P ₀ , P ₁ , P ₂ , P ₃ , P ₄ , P ₅ , P ₆ are arranged on the parallel micro-reaction channel with a certain angle shown in Fig. 1 and Fig. 2 , and the holes are located in the channel Within the first half; when the angle of the microchannel knuckle or the angle of the curved part is 45° or less, the distance l ₁ between two adjacent rows of holes is greater than the distance l ₂ between two adjacent knuckle tops. In the present invention, l ₁ =2l ₂ , the microchannel When the angle of the broken line or curve is 45°-90°, l ₁ =1.5l ₂ , and when the angle of the broken line or curve of the microchannel is 90° or above, l ₁ =l ₂ .

Figure 3 shows a mixing plate (M plate) for two-phase fluid mixing composed of parallel micro-reaction channels with a 30° angle curve structure, which is also called a micro-mixing plate in the present invention. Figure 4 is a distribution plate (D plate) with no holes but containing microchannels distributed in parallel, also referred to as a microdistribution plate in the present invention. Multiple M-boards as shown in Figure 3 and D-boards as shown in Figure 4 are superimposed in sequence to form a combined form as shown in Figure 5, that is, one or more D-boards are between two adjacent M-boards, and the same There is one or more M plates between every two D plates, and the microreactor of the present invention which can be applied to scale-up production is constituted by such several units. Parallel distributed microchannels in Fig. 4 are used as distribution channels of one of the two-phase fluids. In this implementation, as distribution channels of acid gas or its mixture, the number of channels is the same as that of each row of micropores on the parallel microreaction channels in Fig. 3 The number is the same, in this implementation, there are 8 acid gas distribution channels, corresponding to the 8 distribution holes (P ₁ ) in a single row in Figure 3; the distance between the first row of holes and the last row of holes on the parallel micro-reaction channels in Figure 3 L ₁ is L ₁ , which accounts for 20% of the distance L between the head and the tail of the channel. The length of the parallel distribution micro-channel used as the distribution channel in Figure 4 is L ₂ , and the value of L ₂ needs to be slightly greater than L ₁ during design. Parallel microchannel is straight line structure among Fig. 4, and those skilled in the art infers easily, when the multirow micropore on the parallel microreaction channel of the present invention is not on a straight line, distribution channel can directly adopt microreaction channel structure, so distribution The channel structure is also within the scope of the technical solution of the present invention.

Figure 6 is a superimposed schematic diagram of a micro-reaction channel and a distribution channel. The figure schematically shows the wall (W) between the two channels, and several distribution holes (P) on the wall. In Figure 6, the width of the micro-reaction channel is w, the height is h, and the equivalent diameter of the channel is 2w·h/(w+h). A and B in Figure 6 represent gas-liquid two-phase fluids. In principle, A and B can correspond to gas phase (acid gas) and liquid phase (absorbing liquid) respectively, and can also correspond to liquid phase (absorbing liquid) and gas phase (acidic gas) respectively. Gas), preferably the gas enters the micro-reaction channel from the distribution channel. the

The mechanism of the enhanced two-phase mixed mass transfer of the present invention can be briefly described as follows: after changing the straight channel to a broken line or curved structure with a certain angle, at the channel with a curved angle, the air bubbles will be broken or twisted to generate a strong turbulent flow; at the same time, Multiple rows of distribution holes are set on the curved parallel micro-reaction channel. On the one hand, the air bubbles can shear the continuous mobile phase of the absorption liquid to maximize the contact surface between the two phases. On the other hand, the holes are set between adjacent corners. In the straight section, the gas-liquid two-phase also produces a large disturbance flow mixing at the hole, and the above-mentioned avoidance of a branch flow before entering the reaction channel cuts off, which strengthens the gas-liquid two-phase mass transfer and absorption. the

The microreactor whose surface structure is formed by the parallel microreaction channel (equivalent diameter 400 μm) shown in Figure 3 and the parallel distributed microchannel shown in Figure 4 is used to chemically absorb _CO2 gas mixture with DEA, and the residence time is 0.002s -0.5 second, reaction pressure is under the condition of 0.1-5MPa, test microreactor of the present invention strengthens mass transfer absorption effect, reaction result is listed in Fig. 7 and Fig. 8 respectively, in the gas raw material involved in reaction data in the figure _volume The score is 36.2%.

Claims (6)

1. A micro-reaction method that can realize acid gas efficient absorption is characterized in that: adopt micro-reactor to make acid gas to be absorbed or its mixture and absorption liquid flow through this micro-reactor under reaction pressure 1-5MPa, and in Stay in the parallel micro-reaction channels in the micro-reactor for 0.01-0.5 seconds to complete the absorption; The microreactor comprises one or more micro-mixing plates and one or more micro-distribution plates; each micro-mixing plate is provided with parallel micro-reaction channels, and each micro-reaction channel contains One or more micropores; each microdistribution plate is provided with parallel distributed microchannels corresponding to and connected to the above micropores; the acid gas or its mixture flowing through the microreactor and the absorption liquid Flowing through the micro-distribution plate and the micro-mixing plate respectively, and contacting through the micropores on the micro-reaction channel; the gas-liquid two-phase fluid after contacting and mixing occurs at least one zigzag flow and/or at least one curved flow in the micro-reaction channel; Wherein, the parallel micro-reaction channels on each micro-mixing plate include two or more rows of regular microholes in the axial direction, and the position of the last row of microholes is within the first row of microholes to the center of the channel; The parallel micro-reaction channel on the micro-mixing board is a curved or folded line structure, and the bending or folding angle is 10°-150°, The equivalent diameter of the micro-reaction channel is 400 μm. 2. micro-reaction method as claimed in claim 1, is characterized in that: the parallel distribution microchannel number on the described micro-distribution plate is identical with the number of the single row of holes on the micro-mixing plate; The distribution microchannel extends to a row of holes on the micromixing plate near the axial tail of the parallel microreaction channel, and serves as a distribution channel for one of the gas-liquid two-phase fluids; Each micro-mixing plate and the parallel micro-channels on the micro-distribution plate constituting the microreactor contain walls, and the parallel micro-channels on each alternately arranged micro-mixing plate and the micro-distribution plate are separated by walls; A single row of micropores or multiple rows of micropores are located on the wall, and the parallel microreaction channels communicate with the parallel distributed microchannels through the micropores on the wall. 3. micro-reaction method as claimed in claim 1, is characterized in that: when micro-reaction channel bending angle or kink angle are at 45 ° and below, the spacing _l of adjacent two rows of holes is greater than or equal to adjacent two bending angles or twice the distance l ₂ between the tip of the knuckle, that is, l ₁ ≥ 2l ₂ , when the bending angle or knuckle angle of the micro-reaction channel is (>45°) ~ 90°, 2l ₂ ＞l ₁ ＞l ₂ , the micro-reaction channel has a broken line or When the curve angle is above 90°, l ₁ =l ₂ . 4. The micro-reaction method according to claim 1, wherein the distance between the first row of holes and the last row of holes on the parallel micro-reaction channel accounts for 20% of the distance between the head and tail of the micro-reaction channel. 5. micro-reaction method as claimed in claim 1, is characterized in that: described micro-reactor comprises at least one micro-mixing plate and at least one micro-distributing plate; Mixing plates and multiple micro-distribution plates, except for the micro-mixing plates or micro-distribution plates at both ends, each or more micro-distribution plates are between two micro-distribution plates, and each or two micro-distribution plates are between between two micromixing plates. 6. The micro-reaction method according to claim 1, characterized in that: the acid gas to be absorbed can be CO ₂ , H ₂ S, SO ₂ , SO ₃ , or HCl, and the absorption liquid is organic amines Or its composite components or organic amines with activators added.

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