CN100582201C - Combined system and process for producing electricity-substituted natural gas based on coal gasification and methanation - Google Patents

Abstract

An electric-substituting natural gas combined system and process based on coal gasification and methanation are disclosed. The process is carried out by delivering oxygen, powdered coal or water-gas slurry into gasified apparatus, recovering for crude gasified gas by wet heat, delivering into sulfur-resisting carbon monoxide carbon reactor, adjusting hydrogen-carbon ratio, entering into desulfurizing decarbonizer, recovering elementary sulfur while enriching carbon dioxide, delivering synthetic gas into methane reactor to generate substituted natural gas as domestic gas partially, entering into gas and steam combined circulator partially, and entering into substituted natural gas storage tank partially. It integrates coal gasified, methanation and gas steam combined circulation together, it's efficient and clean, has better utilizing rate, no CO2 discharge and need for changing gas turbine or load.

Description

Electricity-alternative natural gas cogeneration system and process based on coal gasification and methanation

technical field

The present invention mainly relates to a novel electricity-replacing natural gas cogeneration system and process method, in particular to a cogeneration system and process method based on coal gasification and methanation. Coke oven gas utilization method.

Background technique

Coal gasification is the most important core technology and key equipment in the chemical system based on coal. The energy and chemical system based on it can not only better solve the problems of efficiency and pollutant discharge in the coal conversion process, but also produce Energy products such as liquid fuel and electricity are of great significance to solving the comprehensive utilization of coal resources and alleviating the shortage of oil and gas resources in China.

The traditional application of methanation as a purification technology is: (1) to remove a small amount of CO and CO ₂ in process gas (such as refined H ₂ or ammonia synthesis gas); (2) city gas is purified by CO methanation Detoxification, and the calorific value per unit volume increases. The large-scale application of methanation is to produce alternative natural gas. For example, the Great Plains natural gas plant in the United States was put into operation in 1984, with a daily coal consumption of 18,500 tons, an availability rate of more than 98.7%, and a _CO2 emission reduction of 5,000 tons/day.

In recent years, due to the soaring price of fuel oil and natural gas worldwide, coupled with the obvious intensification of the impact of the greenhouse effect on climate and ecology. According to the resource situation of rich coal and little gas in our country, IGCC, as a new type of clean coal power generation technology, has once again stood on the stage of history by virtue of its high power supply efficiency and potential CO ₂ emission reduction advantages. However, it still faces the following three problems: first, the economy of IGCC power plants, the cost of IGCC power plants is currently twice the cost of ordinary coal-fired power plants; second, the variable load operation capacity of IGCC power plants; Value gas transformation technology.

In addition, my country's coke production, consumption, and export volume all rank first in the world, but a large amount of coke oven gas is not effectively used, and it is directly vented and burned, which not only wastes precious resources, but also seriously pollutes the environment.

Contents of the invention

The purpose of the present invention is to comprehensively utilize the coal gasification and methanation technology that has been applied on a large scale, solve the problems existing in the existing high-efficiency coal utilization technology and propose a coal-based electricity-alternative natural gas cogeneration system and process method, and change the traditional power station A single form of energy supply, simultaneously producing electricity and substituting natural gas; at the same time, with the help of this system and process method, it provides a new solution for the utilization of coke oven gas, transforming it into an alternative natural gas with higher energy density.

The purpose of the present invention can be achieved through the following technical solutions:

A coal gasification methanation-based electricity-replacing natural gas cogeneration system is characterized in that the system includes:

a) a gas-steam combined cycle device;

b) an air separation plant that produces oxygen;

c) A coal gasification device that produces high-pressure steam and crude gas, the coal gasification device is connected to the air separation device through an oxygen pipeline, and connected to a gas-steam combined cycle device through a high-pressure steam pipeline;

d) a carbon monoxide sulfur-tolerant shift reactor, which adjusts the crude gasification gas produced by the coal gasification equipment into gasification gas suitable for methane synthesis;

e) a desulfurization and decarbonization device, which removes organic sulfur and inorganic sulfur from the gasification gas coming out of the carbon monoxide sulfur-tolerant shift reactor, and is connected with the carbon monoxide sulfur-tolerant shift reactor through the gasification gas pipeline and Recover elemental sulfur and enrich carbon dioxide;

f) A methanation reactor, which generates alternative natural gas after the reaction, which is connected to the carbon monoxide sulfur-resistant shift reactor through a gasification gas pipeline, and is respectively connected to a civil fuel pipeline, an alternative natural gas storage tank and a fuel gas pipeline through an alternative natural gas pipeline. The steam combined cycle device is connected to the gas-steam combined cycle device, the carbon monoxide sulfur-resistant shift reactor and the desulfurization and decarbonization equipment respectively through steam pipelines.

A kind of electricity-replacing natural gas cogeneration process method based on coal gasification methanation provided by the present invention is characterized in that the method is carried out according to the following steps:

1) The oxygen produced by air entering the air separation device enters the coal gasification equipment together with pulverized coal or coal-water slurry, and the crude gasification gas produced is recovered by sensible heat to generate high-pressure steam and sent to the gas-steam combined cycle device to generate electricity;

2) The cooled crude gasification gas enters the carbon monoxide sulfur-tolerant shift reactor for shift reaction to adjust the hydrogen-carbon ratio suitable for methane synthesis; the adjusted gasification gas enters the desulfurization and decarbonization equipment to remove the organic sulfur and inorganic Sulfur, to obtain net synthesis gas, and recover elemental sulfur to obtain enriched carbon dioxide to achieve emission reduction;

3) Send the obtained net synthesis gas into the methanation reactor to generate alternative natural gas, part of which is used as civil gas, part of which is sent into the gas-steam combined cycle device as fuel to generate electricity, and part of which is sent into the alternative natural gas storage tank for emergency needs; The reaction process releases a large amount of heat to generate medium-pressure steam, part of which is sent to the gas-steam combined cycle device to be converted into electricity, part of which is sent to the carbon monoxide sulfur-tolerant shift reactor, and part of which is sent to the desulfurization and decarbonization equipment.

The electricity-replacing natural gas cogeneration process based on coal gasification and methanation is characterized in that: the catalyst used in the carbon monoxide sulfur-tolerant shift reactor is a cobalt-molybdenum catalyst, and the hydrogen-carbon ratio suitable for methane synthesis is adjusted to be 3:1.

The electricity-replacing natural gas cogeneration process based on coal gasification and methanation is characterized in that: the reaction process in the methanation reactor described in step 3) is carried out in two steps, and the first step is carried out at a temperature of 500-600 The second step is carried out in an isothermal reactor at 250-300°C, and the reaction pressure is 50-60bar; the heat released during the reaction and the pressure of the medium-pressure steam generated is 40-60bar.

The electricity-replacing natural gas cogeneration process based on coal gasification and methanation is characterized in that: the coal gasification equipment adopts coal powder or coal-water slurry feeding and sensible heat recovery, and the gasification pressure is 55- 65bar, the pressure of the high-pressure steam generated is 80-140bar, and the temperature of the crude gasification gas after cooling is 150-400°C.

The described electricity-replacement natural gas cogeneration process method based on coal gasification and methanation is characterized in that: when the coal gasification equipment fails, the substitute natural gas stored in the substitute natural gas storage tank is sent to the gas-steam combined cycle device to generate electricity.

The electricity-replacing natural gas cogeneration process based on coal gasification and methanation is characterized in that the hydrogen-carbon ratio is adjusted by direct mixing of coke oven gas and gasification gas after shift reaction.

The present invention has the following advantages and outstanding effects: ① Coal (especially high-sulfur coal, etc.) can be converted into clean, high value-added electricity and substitute natural gas energy carriers. Therefore, electricity-alternative natural gas joint production plants can be established in places with coal resources but scarce natural gas resources around major cities, which can not only provide electricity for cities, but also provide alternative natural gas for civilian use. The organic integration of coal gasification, methanation and gas-steam combined cycle realizes the efficient and clean utilization of coal without the need to modify the gas turbine. ② It can efficiently and comprehensively utilize coke oven gas, and solve the coke oven gas outlet problem of coking plants, especially small and medium coking plants. ③Electricity and alternative natural gas jointly bear the equipment cost of coal gasification, purification and other processes, thus reducing the specific investment cost. The diversity of products has changed the supply mode of the single energy carrier of traditional power stations, which can enhance the competitiveness and economic benefits of enterprises. ④The production process of electricity and alternative natural gas is coupled together. When the load of electricity needs to change, it only needs to send the alternative natural gas produced by the methanation reaction to the urban natural gas pipeline network. Adjustment changes the load. ⑤Replacing natural gas as the fuel of the gas turbine, its composition fully meets the requirements of the traditional gas turbine, so there is no need to modify the gas turbine. ⑥Because the hydrogen-carbon ratio needs to be adjusted in the production process of replacing natural gas, CO ₂ emission can be reduced, and the purpose of emission reduction is more reasonable.

Description of drawings

Figure 1 is a process flow chart of the electricity-alternative natural gas cogeneration system based on coal gasification and methanation in the present invention.

Detailed ways

The system structure and specific implementation of the present invention will be further described below with the aid of the accompanying drawings.

The system proposed by the present invention mainly includes a gas-steam combined cycle device 20, an air separation device 21, a coal gasification device 15, a carbon monoxide sulfur-resistant shift reactor 16, a desulfurization and decarbonization device 17, a methanation reactor 18, and an alternative natural gas storage tank 19; The coal gasification equipment is connected to an air separation device through an oxygen pipeline, and is connected to a gas-steam combined cycle device through a high-pressure steam pipeline; Gasification gas synthesized from methane; the desulfurization and decarbonization equipment removes the organic sulfur and inorganic sulfur in the gasification gas from the carbon monoxide sulfur-resistant shift reactor, and connects the gasification gas pipeline with the carbon monoxide sulfur-resistant The shift reactor is connected and recovers elemental sulfur to enrich carbon dioxide; the methanation reactor generates natural gas after reaction, and the reactor is connected with the carbon monoxide sulfur-resistant shift reactor through the gasification gas pipeline. The pipelines are respectively connected to civil fuel pipelines, alternative natural gas storage tanks and gas-steam combined cycle devices, and are respectively connected to gas-steam combined cycle devices, carbon monoxide sulfur-resistant shift reactors and desulfurization and decarbonization equipment through steam pipelines.

Concrete process of the present invention is as follows:

Air 1 enters the air separation device 21 to produce oxygen 3 and coal powder or coal-water slurry 2 enters the coal gasification equipment 15 together, and the crude gasification gas produced is recovered by sensible heat to generate high-pressure steam 5 and sent to the gas-steam combined cycle device 20 The cooled crude gasification gas 4 enters the carbon monoxide sulfur-resistant shift reactor 16 to undergo a shift reaction, using cobalt-molybdenum as a catalyst to adjust the hydrogen-carbon ratio suitable for methane synthesis; the adjusted gasification gas 6 enters the desulfurization and decarbonization equipment 17 , to remove the organic and inorganic sulfur therein to obtain a net synthesis gas 7, and recover elemental sulfur 9 to enrich carbon dioxide 8 to achieve emission reduction; the obtained net synthesis gas 7 is sent to the methanation reactor 18 to generate alternative Natural gas 10, part of which is used as civil gas, part of which is sent to gas-steam combined cycle device 20 as fuel to generate electricity 12, and part of which is sent to replace natural gas storage tank 19 for emergency needs; a large amount of heat released during the reaction process is taken away by high-temperature feed water, The reaction temperature is maintained in a certain range, and medium-pressure steam 11 is generated, part of which is sent to the gas-steam combined cycle device 20 to be converted into electricity 12, part of which is sent to the carbon monoxide sulfur-tolerant shift reactor 16 as a reaction raw material, and part of which is sent to desulfurization and decarburization The equipment 17 provides heat for the regeneration of the absorbent; when the coal gasification equipment 15 etc. fails, the substitute natural gas 13 stored in the substitute natural gas storage tank 19 can be sent to the gas-steam combined cycle device 20 to generate electricity 12 .

The present invention will be described in further detail below through the examples and accompanying drawings, but the present invention is not limited to the examples.

Embodiment 1: Based on the consumption of 5000 tons of raw coal per day and the gas-steam combined cycle of Siemens V94.3a as the basis, the calculation of the overall performance of the system at base load is carried out for the embodiment.

The oxygen 3 produced by the air 1 entering the air separation device 21 is pressurized to 60-70 bar and enters the coal gasification equipment 15 together with the coal water slurry 2 with a concentration of 60-70%. The coal gasification equipment can adopt various structural forms, For example, two-stage, four-nozzle opposed type or Texaco type, etc., the gasification pressure is 55-65bar, the temperature is 1300-1500℃, and the crude gasification gas produced is recovered by sensible heat to produce high-pressure steam of 80-140bar5 Send it to the gas-steam combined cycle device 20; the crude gasified gas 4 after cooling is 150-400 ° C, and enters the carbon monoxide sulfur-resistant shift reactor 16 to undergo a shift reaction. The catalyst used is a cobalt-molybdenum catalyst, and the hydrogen-carbon ratio is adjusted to 3:1 suitable for methane synthesis; the adjusted gasification gas 6 enters the desulfurization and decarbonization equipment 17, and uses MDEA or NHD as the absorbent to remove the main organic sulfur (H ₂ S) and inorganic sulfur (COS). The Claus process recovers elemental sulfur (S) 9 and enriches carbon dioxide 8, which is pressurized and liquefied and then injected into oil fields or stored on the seabed to reduce emissions; the obtained net synthesis gas 7 enters the methanation reactor 18 to generate alternative natural gas, and the methanation reaction The molar content of methane in the alternative natural gas 10 can reach 93-96%, which is divided into three parts for utilization, part of which is sent to the gas-steam combined cycle device 20 as fuel to generate electricity 12, and part of which is sent to the natural gas pipeline network for urban civilian use Gas, and a small part is sent to substitute natural gas storage tank 19, so that when coal gasification equipment breaks down, the substitute natural gas 13 will be supplied to gas-steam combined cycle unit 20 for use, improving the availability of the whole plant; after the adiabatic reaction The heat of the high-temperature gas and the large amount of heat released during the reaction process are taken away by the high-temperature feed water, and the isothermal reaction temperature is maintained at 250-300°C. The generated 40-60bar medium-pressure steam 11 is divided into three streams, and one stream is sent to the gas-steam joint The circulation device 20 is converted into electricity 12, one of which is sent to the carbon monoxide sulfur-resistant shift reactor 16 as a reaction raw material, and the other is sent to the desulfurization and decarbonization equipment 17 to provide heat for the regeneration of the absorbent.

The gasification coal used in Example 1 is bituminous coal from Binxian County, Shaanxi, and its composition and lower calorific value are shown in Table 1.

Table 1 Raw coal composition and calorific value

Example 2: Taking the situation where gasification gas 6 and coke oven gas 14 are directly mixed to adjust the hydrogen-carbon ratio to 3:1 as an example, so as to reduce the load of the carbon monoxide sulfur-tolerant shift reactor for shift reaction, other organizational forms of the process flow And processing parameters are defined as embodiment 1. In Example 2, the raw material consumption and overall system performance are calculated based on the product output calculated in Example 1.

The coke oven gas composition and lower calorific value used in Example 2 are shown in Table 2.

Table 2 Composition and lower calorific value of coke oven gas

Through calculation, the overall performance of the system and process method of the present invention in Embodiment 1 and Embodiment 2 is shown in the data in Table 3. It can be seen from the table that the coal gasification and methanation electricity-replacing natural gas cogeneration system and process based on the present invention, in addition to the aforementioned advantages, the system efficiency is also improved compared with the prior art.

Table 3 embodiment 1 and embodiment 2 overall performance data

Alternative natural gas efficiency = low calorific value of alternative natural gas / raw material calorific value;

Power supply efficiency = replacement natural gas efficiency × gas-steam combined cycle efficiency;

System efficiency = (low calorific value of alternative natural gas × output of alternative natural gas + net power supply) / raw material heat

Claims (6)

1. electric-substituted natural gas co-generation system based on coal-gasification methaneization is characterized in that this system comprises:

A) a combustion and steam combined cycle power plant (20);

B) an oxygenous air separation plant (21);

C) coal gasification apparatus (15) that produces high pressure steam and raw gas, this coal gasification apparatus is connected with air separation plant (21) by oxygen channel, is connected with the combustion and steam combined cycle power plant by the high pressure steam pipeline;

D) a carbon monoxide sulfur-tolerant water gas shift device (16), the thick gasification gas that this carbon monoxide sulfur-tolerant water gas shift device makes coal gasification apparatus are adjusted into and are fit to methane synthetic gasification gas;

E) a desulfurization and decarburization equipment (17), this equipment removes organosulfur and the inorganic sulfur from the gasification gas that carbon monoxide sulfur-tolerant water gas shift device comes out, be connected with described carbon monoxide sulfur-tolerant water gas shift device by the gasification gas pipeline, and reclaim elemental sulfur (9), carbon dioxide-enriched (8);

F) methanator (18), the reaction back generates instead of natural gas, this reactor is connected with domestic fuel pipeline, instead of natural gas storage tank (19) and described combustion and steam combined cycle power plant respectively by the instead of natural gas pipeline, is connected with desulfurization and decarburization equipment with combustion and steam combined cycle power plant, carbon monoxide sulfur-tolerant water gas shift device respectively by steam-pipe.

2. one kind is adopted the electric-substituted natural gas joint process method based on coal-gasification methaneization of system according to claim 1, it is characterized in that this method carries out as follows:

1) air (1) enters oxygen (3) that air separation plant (20) makes and coal dust or coal water slurry (2) and enters coal gasification apparatus (15) together, the thick gasification gas (4) that produces reclaims through sensible heat, produces high pressure steam (5) and sends into combustion and steam combined cycle power plant (20) to produce electric power (12);

2) the thick gasification gas (4) after the cooling enters carbon monoxide sulfur-tolerant water gas shift device (16) generation transformationreation, is fit to methane synthetic hydrogen-carbon ratio to adjust; Gasification gas (6) after adjusting enters desulfurization and decarburization equipment (17), removes wherein organosulfur and inorganic sulfur, obtains clean synthetic gas (7), and reclaims elemental sulfur (9), and carbon dioxide-enriched (8) is to realize reduction of discharging;

The clean synthetic gas (7) that 3) will obtain is sent into methanator (18) and is generated instead of natural gas (10), part is as domestic gas, part is sent into combustion and steam combined cycle power plant (20) and is acted as a fuel to produce electric power (12), and part is sent into instead of natural gas storage tank (19) in case of need; The thermogenesis middle pressure steam (11) of emitting in the reaction process, part is sent into combustion and steam combined cycle power plant (20) and is changed electric power (12) into, and part is sent into carbon monoxide sulfur-tolerant water gas shift device (16), and part is sent into desulfurization and decarburization equipment (17).

3. the electric-substituted natural gas joint process method based on coal-gasification methaneization as claimed in claim 2, it is characterized in that: the catalyzer that described carbon monoxide sulfur-tolerant water gas shift device uses is the cobalt-molybdenum catalyzer, and regulating suitable methane synthetic hydrogen-carbon ratio is 3: 1.

4. as claim 2 or 3 described electric-substituted natural gas joint process methods based on coal-gasification methaneization, it is characterized in that: the reaction process in the described methanator of step 3) is carried out in two steps, the first step is carried out in temperature 500-600 ℃ adiabatic reactor, second step carried out in 250-300 ℃ isothermal reactor, and reaction pressure is 50～60bar; The heat that reaction process is emitted is 40-60bar with the middle pressure steam pressure that produces.

5. the electric-substituted natural gas joint process method based on coal-gasification methaneization as claimed in claim 2, it is characterized in that: described coal gasification apparatus adopts coal dust or coal water slurry charging and sensible heat way of recycling, vapor pressure is 55-65bar, the high-pressure steam pressure that produces is 80～140bar, and the temperature of the thick gasification gas after the cooling is 150～400 ℃.

6. the electric-substituted natural gas joint process method based on coal-gasification methaneization as claimed in claim 2, it is characterized in that: when when breaking down, the instead of natural gas (13) that stores in the instead of natural gas storage tank (19) being sent into combustion and steam combined cycle power plant (20) to produce electric power (12) at coal gasification apparatus (15).

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