CN104193585A - System and process for preparing methyl alcohol through coke-oven gas-assisted coal gasification - Google Patents

Abstract

The invention discloses a coke oven gas-assisted coal gasification system and process for methanol production. The system includes a coal water slurry preparation unit, a coal gasification unit, a synthesis gas purification unit, a methanol synthesis unit, a coke oven gas purification and separation unit, a triple reforming reaction unit and a gas mixer connected in sequence. The invention realizes the effective utilization of coal resources through the complementary utilization of elements of coal and coke oven gas, and avoids the waste of effective elements and the cost of energy consumption caused by component adjustment operations. Moreover, the present invention utilizes carbon dioxide and coke oven gas by integrating the triple reforming reaction unit, so that the operation unit is simpler, the reaction process is more flexible, and the equipment investment is relatively small.

Description

A coke oven gas assisted coal gasification system and process for methanol production

technical field

The invention belongs to the technical field of energy and chemical industry, and in particular relates to a coke oven gas-assisted coal gasification system and process for methanol production.

Background technique

Methanol is an important chemical basic product and an important raw material for the manufacture of various organic products such as formaldehyde, acetic acid, methyl chloride, methylamine and dimethyl sulfate, as well as C1 chemicals such as ethylene and propylene. In 2010, my country's methanol production capacity reached 37.57 million tons, with an output of 15.75 million tons, making it the world's largest producer of methanol. At present, my country mainly uses coal as raw material to produce methanol.

There are two main problems in the existing coal-to-methanol process: high energy consumption and large _CO2 emissions. The main reason for the large _CO2 emissions and low energy efficiency is that the hydrogen-to-carbon ratio of the crude synthesis gas produced during the coal gasification process is only about 0.7, while the hydrogen-to-carbon ratio required for the synthesis of methanol is about 2.1, so the crude synthesis gas needs to enter water The coal conversion unit converts CO in the synthesis gas into H ₂ and CO ₂ , which causes a large amount of CO ₂ emissions and waste of carbon elements, and the conversion process consumes a large amount of energy at the same time.

In order to solve the above-mentioned problems in the coal-to-methanol process, a process of coal and coke oven gas combined supply to methanol (olefin) is proposed (application publication number CN 103694074 A), and the process flow chart is shown in Figure 1 . This coal and coke oven gas joint supply methanol production process, through the dry and wet reforming of methane in the coke oven gas, to improve the hydrogen-carbon ratio of coal gasification synthesis gas, avoiding the water coal in the original methanol production process The waste of synthesis gas brought by the conversion unit improves the utilization rate of carbon elements and reduces _CO2 emissions. However, the methanol synthesis gas produced by this process needs to be composed of four strands (coal gasification synthesis gas, dry weight integrated gas, wet weight integrated gas, hydrogen), and the operation flexibility is small, and the system flexibility is low. The composition of raw materials changes, and the process may not be able to obtain the synthesis gas that meets the hydrogen-to-carbon ratio required for methanol synthesis; and the introduction of too many operating units also greatly increases the equipment investment of the process.

Contents of the invention

In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a coke oven gas assisted coal gasification methanol production system.

Another object of the present invention is to provide a process for preparing methanol using the above system.

In order to realize the above-mentioned purpose of the invention, the present invention adopts following technical scheme:

A coke oven gas assisted coal gasification methanol production system, comprising a coal water slurry preparation unit, a coal gasification unit, a synthesis gas purification unit, a coke oven gas purification and separation unit, a gas mixer and a methanol synthesis unit, the coal water slurry The preparation unit is provided with a raw coal inlet, the coal water slurry outlet of the coal water slurry preparation unit is connected to the coal water slurry inlet of the coal gasification unit through a pipeline, and the coal gasification crude synthesis gas outlet of the coal gasification unit is connected with the coal gas of the synthesis gas purification unit through a pipeline The crude synthesis gas inlet is connected, and the purified coal gasification crude synthesis gas outlet of the synthesis gas purification unit is connected to the gas mixer through a pipeline; the coke oven gas purification and separation unit is provided with a coarse coke oven gas inlet, and the coke oven gas purification and separation The hydrogen outlet of the unit is connected to the gas mixer through a pipeline; the methanol reaction synthesis gas outlet of the gas mixer is connected to the methanol synthesis gas inlet of the methanol synthesis unit through a pipeline; the system also includes a triple reforming reaction unit;

The carbon dioxide outlet of the synthesis gas purification unit is connected with the carbon dioxide inlet of the triple reforming reaction unit through a pipeline;

The methane gas outlet of the coke oven gas purification and separation unit is connected with the methane gas inlet of the triple reforming reaction unit through a pipeline; the triple reforming reaction synthesis gas outlet of the triple reforming reaction unit is connected with a gas mixer through a pipeline, and the triple reforming reaction unit The whole reaction unit is also provided with an oxygen inlet and a water vapor inlet.

A kind of technique that adopts above-mentioned system to prepare methanol, process step is as follows:

After the raw coal is made into coal-water slurry in the coal-water slurry preparation unit, it enters the coal gasification unit together with oxygen for coal gasification reaction to obtain coal gasification crude synthesis gas; the coal gasification crude synthesis gas enters the synthesis gas purification unit to remove sulfide and Carbon dioxide, to obtain purified coal gasification crude synthesis gas and carbon dioxide;

Raw raw coke oven gas enters the coke oven gas purification and separation unit, and methane gas, hydrogen gas and impurities are obtained after purification and separation; the carbon dioxide, oxygen and water vapor obtained by the methane gas and synthesis gas purification unit enter the triple reforming reaction unit together to obtain triple reforming synthesis gas; the triple reforming synthesis gas, the purified coal gasification crude synthesis gas obtained by the synthesis gas purification unit, and the hydrogen obtained by the coke oven gas purification and separation unit enter the gas mixer together, and are mixed Finally, the methanol reaction synthesis gas is obtained; the methanol reaction synthesis gas enters the methanol synthesis unit, and the methanol product is obtained after reaction and purification.

Preferably, the feed mass ratio of the crude coke oven gas to the raw coal is (3-8):1, wherein the mass of the crude coke oven gas is calculated by converting the calorific value into the mass of standard coal.

Preferably, the hydrogen-to-carbon ratio of the coal gasification crude synthesis gas is 0.5-1.0.

Preferably, the composition of the raw raw coke oven gas includes H ₂ with a volume fraction of 55-60% and CH ₄ with a volume fraction of 20-27%. The carbon ratio is 5-7.

Preferably, the operating temperature of the triple reforming reaction unit is 800-900° C., and the operating pressure is 1 atm.

Preferably, the separation process of the crude coke oven gas is a pressure swing adsorption process.

The principle of the present invention is: to make full use of coke oven gas, not only its high hydrogen-to-carbon ratio, but also CH ₄ with extremely high utilization value must be considered, and CO and H ₂ can be produced through reforming. There are three pathways for methane reforming, namely steam reforming of methane, carbon dioxide reforming of methane, and partial oxidation of methane. Among them, steam reforming of methane, carbon dioxide reforming of methane are all endothermic reactions, and the energy consumption of the process is high, while carbon dioxide reforming of methane is an exothermic reaction. If the steam reforming of methane, carbon dioxide reforming of methane and partial oxidation of methane are combined Together (methane triple reforming), the energy of the exothermic reaction can be supplied to the endothermic reaction, realizing the self-heating of the reaction. Therefore, the present invention uses this triple reforming reaction to couple coke oven gas and gasification coal gas to produce methanol.

Compared with the existing coal and coke oven gas combined supply technology for methanol production, the present invention has the following advantages and beneficial effects:

(1) Compared with the current coal and coke oven gas combined supply process for methanol production, the present invention couples methane dry reforming reaction, methane steam reforming reaction and methane partial oxidation reaction through a methane triple reforming reactor, which makes the production process A triple reforming reaction unit replaces the original methane dry reforming reaction unit and methane steam reforming reaction unit, simplifies the operation unit of coal and coke oven gas methanol production process, and reduces equipment investment.

(2) At present, the methanol synthesis gas in the coal and coke oven gas combined supply process for methanol production is composed of three streams. Therefore, the operating flexibility of the current system is low. Synthesis gas required for synthesis, low system flexibility. The new process proposed by the invention reduces the number of constituent streams of methanol synthesis gas, and improves system flexibility and operation flexibility. At the same time, due to the simplification of the process, the operation stability is high.

(3) Compared with the current coal and coke oven gas cogeneration process for producing methanol, the present invention reduces the methane dry reforming and steam reforming units with high energy consumption, so the energy efficiency of the process can be improved by more than 8%, and the carbon element Utilization can be increased by more than 5%.

Description of drawings

Figure 1 is a schematic diagram of the current coal and coke oven gas cogeneration process for methanol production. Among them, 101 is the coal water slurry preparation unit, 102 is the coal gasification unit, 103 is the synthesis gas purification unit, 104 is the methanol synthesis unit, 105 is the coke oven gas purification and separation unit, 106 is the methane dry reforming unit, and 107 is the methane water Steam reforming unit, 108 is a gas mixer; 200~215 is a logistics number, of which 200 is raw coal, 201 is coal water slurry, 202 is oxygen, 203 is coal gasification crude syngas, 204 is purified coal gasification crude Syngas, 205, 215 is carbon dioxide, 206 is methanol synthesis gas, 207 is methanol, 208 is coke oven gas, 209, 210, 211 is methane, 212 is hydrogen, 213 is dry weight integrated gas, 214 wet weight integrated gas gas.

Fig. 2 is a schematic diagram of coke oven gas-assisted coal-to-methanol process of the present invention. Among them, 109 is the triple reforming reaction unit; 200-218 is the stream number, of which 216 is oxygen, 217 is water vapor, 218 is the triple reforming reaction synthesis gas, 219 is the impurity obtained by purifying coke oven gas such as tar, and the rest of the numbers are the same as in Figure 1 The same number in the same number indicates the same operating unit or stream.

Detailed ways

The present invention will be further described in detail below with reference to the examples and drawings, but the implementation of the present invention is not limited thereto.

A coke oven gas assisted coal gasification methanol production system of the present invention, as shown in Figure 2, includes a coal water slurry preparation unit 101, a coal gasification unit 102, a synthesis gas purification unit 103, a coke oven gas purification and separation unit 105, a gas Mixer 108 and methanol synthesis unit 104, described coal-water slurry preparation unit 101 is provided with raw coal inlet, and the coal-water slurry outlet of coal-water slurry preparation unit 101 is connected with the coal-water slurry inlet of coal gasification unit 102 through pipeline, and coal gasification The coal gasification crude synthesis gas outlet of the unit 102 is directly connected to the coal gasification crude synthesis gas inlet of the synthesis gas purification unit 103 through a pipeline, and the coal gasification crude synthesis gas outlet of the synthesis gas purification unit 103 is connected to a gas mixer 108 through a pipeline Coke oven gas purification and separation unit 105 is provided with coarse coke oven gas inlet, and the hydrogen outlet of coke oven gas purification and separation unit 105 is connected with gas mixer 108 by pipeline; The methanol reaction synthesis gas outlet of gas mixer 108 is connected with gas mixer through pipeline The methanol synthesis gas inlet of the methanol synthesis unit 104 is connected; the system also includes a triple reforming reaction unit 109;

The carbon dioxide outlet of the synthesis gas purification unit 103 is connected with the carbon dioxide inlet of the triple reforming reaction unit 109 through a pipeline;

The methane gas outlet of the coke oven gas purification and separation unit 105 is connected to the methane gas inlet of the triple reforming reaction unit 109 through a pipeline; the triple reforming synthesis gas outlet of the triple reforming reaction unit 109 is connected to the gas mixer 108 through a pipeline.

The coal gasification unit 102 is also provided with an oxygen inlet, the coke oven gas purification and separation unit 105 is also provided with a coke oven gas purification impurity outlet, and the methanol synthesis unit 104 is also provided with a methanol outlet; the triple reforming reaction unit 109 is also provided with an oxygen inlet and a water outlet. Steam inlet.

As can be seen from Fig. 2, the present invention adopts the processing steps of above-mentioned system to prepare methanol as follows:

Raw coal 200 is made into coal-water slurry 201 by coal-water slurry preparation unit 101, and enters coal gasification unit 102 together with oxygen 202 for coal gasification reaction to produce coal gasification crude synthesis gas 203; coal gasification crude synthesis gas 203 enters synthesis gas Purification unit 103 removes sulfide and carbon dioxide to obtain purified coal gasification synthesis gas 204 and carbon dioxide 205;

Raw material crude coke oven gas 208 enters coke oven gas purification and separation unit 105, and methane gas 209, hydrogen gas 212 and impurities 219 are obtained after purification and separation; And water vapor 217 enters triple reforming reaction unit 109 jointly, makes triple reforming reaction synthesis gas 218; The coal gasification synthesis gas 204 after the purification of described triple reforming reaction synthesis gas 218, synthesis gas purification unit 103 obtains and coke oven gas purification Together with the hydrogen 212 obtained from the separation unit 105, it enters the gas mixture 108, and the methanol reaction synthesis gas 206 is obtained after mixing; the methanol reaction synthesis gas 206 enters the methanol synthesis unit 104, and the methanol product 207 is obtained after reaction and purification.

The difference between coke oven gas assisted coal gasification methanol production process of the present invention and the prior art shown in Fig. Separately into the dry reforming and wet reforming units to generate syngas, but directly into the triple reforming reaction unit. The triple reforming reaction can absorb CO ₂ emitted from the coal gasification process. The hydrogen obtained from coke oven gas separation is mixed with the synthesis gas directly reacted with coal gasification and triple reforming to adjust the hydrogen-to-carbon ratio.

(2) In the system of the present invention, the synthesis gas required for methanol synthesis is composed of coal gasification synthesis gas, triple reforming reaction synthesis gas and hydrogen obtained by separation of coke oven gas, and the hydrogen-to-carbon ratio of the synthesis gas is 2.1 to 2.15 about. Compared with the coal-only methanol production process, the synthesis gas produced by the process proposed by the present invention does not need to enter the water-coal conversion unit to adjust the hydrogen-carbon ratio.

Example 1

The specific implementation of the coke oven gas assisted coal gasification methanol production system in this embodiment is as follows:

The raw coal flow rate entering the process of the present invention is 250t/h. The raw material coke oven gas flow rate is 350t/h. The composition of coke oven gas is shown in Table 1. See Figure 2 for the general flow chart of coke oven gas-assisted coal-to-methanol process:

Raw coal 200 is made into coal-water slurry 201 by the coal-water slurry preparation unit, and then enters the coal gasification unit 101 for coal gasification reaction together with oxygen 202 to produce coal gasification crude synthesis gas 203; the coal gasification crude synthesis gas 203 enters the synthesis gas purification Unit 103 removes sulfide and carbon dioxide to obtain purified coal gasification synthesis gas 204 and carbon dioxide 205;

Raw material crude coke oven gas 208 enters coke oven gas purification and separation unit 105, and methane gas 209, hydrogen gas 212 and impurities 219 are obtained after purification and separation; And water vapor 217 enters triple reforming reaction unit 109 jointly, makes triple reforming reaction synthesis gas 218; The coal gasification synthesis gas 204 after the purification of described triple reforming reaction synthesis gas 218, synthesis gas purification unit 103 obtains and coke oven gas purification Together with the hydrogen 212 obtained from the separation unit 105, it enters the gas mixture 108, and the methanol reaction synthesis gas 206 is obtained after mixing; the methanol reaction synthesis gas 206 enters the methanol synthesis unit 104, and the methanol product 207 is obtained after reaction and purification.

Among them, the operating temperature of the triple reforming reactor is 850°C, and the operating pressure is 1 atm. Other operating units refer to the current working conditions of the coal-to-methanol process.

Table 1 Composition of coke oven gas

Element H ₂ CH ₄ CO CO ₂ N ₂ O ₂ C _m H _n Volume fraction% 59.5 24.8 6.5 5.5 3.2 0.3 0.2

The flow simulation software Aspen is used to simulate the meter of this embodiment, and the simulation results are shown in Table 2.

Table 2 Simulation results

tracking number 203 211 213 214 209 215 212 217 mole fraction N ₂ 0.004 0.006 0.01 0 0.006 0.005 0.067 0.019 O ₂ trace 0.002 0.95 0 trace trace 0.006 0.002 Ar 0.001 0 0.04 0 0.001 trace 0 Trace H ₂ O 0.224 trace 0 1.0 trace trace 0 trace CO 0.356 0.014 0 0 0.558 0.330 0.086 0.319 COS trace 0 0 0 trace trace 0 trace CO ₂ 0.135 trace 0 0 trace 0.005 0 0.003 H ₂ S 0.003 trace 0 0 trace trace trace trace H ₂ 0.277 0.002 0 0 0.434 0.660 0.84 0.652 CH ₄ trace 0.976 0 0 trace trace 0.001 0.005 Molar flow rate, kmol/hr 28202 7495 678 4212 17993 27105 19645 64743 Mass flow rate,t/hr 598.3 122 21.9 75.8 301 295 121.2 717.3 temperature, ℃ 152 65 110 25 240 240 240 240 pressure bar 28 twenty three 41 1.0 twenty three 82 82 82

The product unit consumption and energy consumption of the technological process are converted into energy efficiency. It can be seen from Table 2 that the triple reforming unit absorbs 56% of CO ₂ produced by coal gasification, and converts it together with CH ₄ into CO and H ₂ , which not only reduces CO ₂ emissions, but also increases the amount of effective gas, and the synthesis is more efficient. Much methanol. At this time, _CO2 emission was reduced by 61.2%, and the utilization rate of carbon element was increased to 84.1%. Due to the improvement of the utilization rate of carbon element, the raw coal consumption of the same amount of methanol products produced by the co-generation process is only 28% of that of the single coal-to-methanol process, which greatly reduces the total energy input of the system, so the process has higher energy efficiency, compared with The coal-to-methanol process alone increased by 16.8 percentage points.

The above-mentioned Example 1 was compared with coal and coke oven gas co-produced methanol production in the prior art (the specific process is shown in Figure 1 ) and coal-only methanol production process, and the results are shown in Table 3. Compared with the coal and coke oven gas co-supply methanol production process, the energy efficiency of the present invention is increased by 13%, and the utilization rate of carbon element is increased by 6%. Compared with the coal-only methanol production process, the energy efficiency of the present invention is increased by 17%, and the utilization rate of carbon element is increased by 28%.

Table 3 Comparison between the present invention and coal-to-methanol main indicators

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (7)

1. A coke oven gas assisted coal gasification methanol system, comprising a coal water slurry preparation unit, a coal gasification unit, a synthesis gas purification unit, a coke oven gas purification and separation unit, a gas mixer and a methanol synthesis unit, the water The coal slurry preparation unit is provided with a raw coal inlet, the coal water slurry outlet of the coal water slurry preparation unit is connected to the coal water slurry inlet of the coal gasification unit through a pipeline, and the coal gasification crude synthesis gas outlet of the coal gasification unit is connected to the synthesis gas purification unit through a pipeline The inlet of the coal gasification crude synthesis gas is connected, and the outlet of the purified coal gasification crude synthesis gas of the synthesis gas purification unit is connected to the gas mixer through a pipeline; the coke oven gas purification and separation unit is provided with a crude coke oven gas inlet, and the coke oven gas purification The hydrogen outlet of the separation unit is connected to the gas mixer through a pipeline; the methanol reaction synthesis gas outlet of the gas mixer is connected to the methanol synthesis gas inlet of the methanol synthesis unit through a pipeline; it is characterized in that the system also includes a triple reforming reaction unit; The carbon dioxide outlet of the synthesis gas purification unit is connected with the carbon dioxide inlet of the triple reforming reaction unit through a pipeline; The methane gas outlet of the coke oven gas purification and separation unit is connected with the methane gas inlet of the triple reforming reaction unit through a pipeline; the triple reforming reaction synthesis gas outlet of the triple reforming reaction unit is connected with a gas mixer through a pipeline, and the triple reforming reaction unit The whole reaction unit is also provided with an oxygen inlet and a water vapor inlet. 2. a process utilizing the described system of claim 1 to prepare methanol, is characterized in that, described processing step is as follows: After the raw coal is made into coal water slurry, it enters the coal gasification unit together with oxygen for coal gasification reaction to obtain coal gasification crude synthesis gas; the coal gasification crude synthesis gas enters the synthesis gas purification unit to remove sulfide and carbon dioxide to obtain purified coal gas crude synthesis gas, carbon dioxide and sulfur compounds; Raw raw coke oven gas enters the coke oven gas purification and separation unit, and methane gas, hydrogen gas and impurities are obtained after purification and separation; the methane gas, carbon dioxide, oxygen and water vapor obtained from the synthesis gas purification unit enter the triple reforming reaction unit together , to obtain triple reforming synthesis gas; the triple reforming synthesis gas, the purified coal gasification crude synthesis gas obtained by the synthesis gas purification unit, and the hydrogen obtained by the coke oven gas purification and separation unit enter the gas mixture together, and after mixing Finally, the methanol reaction synthesis gas is obtained; the methanol reaction synthesis gas enters the methanol synthesis unit, and the methanol product is obtained after reaction and purification. 3. The process according to claim 2, characterized in that, the feed mass ratio of the raw material coarse coke oven gas to the raw material coal is (3-8): 1, wherein the quality of the coarse coke oven gas is converted according to the calorific value Calculated by the mass of standard coal. 4. The process according to claim 2, characterized in that the hydrogen-to-carbon ratio of the crude coal gasification synthesis gas is 0.5-1.0. 5. The process according to claim 2, characterized in that, the raw raw coke oven gas comprises H ₂ with a volume fraction of 55-60% and CH ₄ with a volume fraction of 20-27%, and the raw raw coke oven gas The ratio of hydrogen to carbon after being purified by the purification and separation unit is 5-7. 6. The process according to claim 2, characterized in that the operating temperature of the triple reforming reaction unit is 800-900° C., and the operating pressure is 1 atm. 7. The process according to claim 2, characterized in that, the separation process of the raw coke oven gas is a pressure swing adsorption process.