UA65856A - A process for preparation of hydrogen and methanol - Google Patents

Abstract

A process for preparation of hydrogen and methanol from converted gas containing carbon oxides and hydrogen involves the methanol synthesis. For the methanol synthesis the converted gas is used; the gas has functional of ì2-cÄ2/cÄ+cÄ2, equal to 2.03-5.4 and being supplied to the reactor system consisting of flow reactor or cascade of flow reactors and/or reactor with recycle of gas mixture, and from the gas which has not reacted the hydrogen is obtained after cleaning.

Description

Description of the invention

The invention relates to a method of obtaining technical hydrogen and methanol from converted gas, which contains 2 carbon monoxide, carbon dioxide and hydrogen.

A known method of obtaining hydrogen from synthesis gas by converting methanol with water vapor and subsequent purification from carbon dioxide (US patent Mo4869894, MKV СО181/13, dated 04.15.87, op. 09.26.89).

The process follows the following reactions: synthesis gas preparation process:

SNAtNo CO ZN»-206 AkJ/mol (1); carbon monoxide conversion process:

СОонОо-СОовН2на1 kJ/mol (2).

The disadvantage of this method is that in the process of obtaining hydrogen, almost all the carbon of the synthesis gas is lost during the washing of carbon dioxide with monoethanolamine or potash from the gas mixture. 19 The closest in technical essence is the method of obtaining hydrogen and methanol from synthesis gas, which mainly contains carbon monoxide and hydrogen, and includes the conversion of carbon monoxide, the subsequent washing of carbon dioxide and the synthesis of methanol, which is carried out before the conversion of carbon monoxide. For methanol synthesis, recirculation gas is used next to fresh syngas, and the amount of recirculation gas does not exceed double the amount of fresh syngas. The molar ratio of hydrogen to carbon monoxide in the gas entering the synthesis is 0.8:1-1.5:1 (patent FRG Mo2904008, MKV СО1В 2, 3. 02.02.79, op. 07.08.8Or., prototype ).

The disadvantage of the known method is that the composition of the gas is much lower than stoichiometric; with this ratio of reacting components, the synthesis of methanol is characterized by a low speed and is accompanied by the occurrence of a large number of side reactions. Such a significant deviation of the ratio of reacting components from stoichiometry leads to a decrease in the degree of conversion of carbon oxides into methanol due to a lack of hydrogen in the source gas, and residual carbon dioxide is blown out of the system. "

However, as the authors themselves note, preference is given to recycling to obtain the required synthesis gas composition.

For this purpose, the possibility of varying the composition of the gas for the synthesis of methanol is provided, which is achieved by returning part of the product flow, which contains hydrogen, from different points of the process: after the stage of conversion of oxide "o" to carbon or purification from carbon dioxide, at the same time, a compressor is used to equalize pressure losses in system. at

Thus, the second disadvantage of this method includes additional energy costs for co-compressing the flow to eliminate pressure losses inside the unit, for recirculation of the unconverted gas mixture, and the fact that the return of part of the product hydrogen leads to product loss. at

The basis of the invention is the task of improving the method of obtaining hydrogen and methanol, in which, "due to the process of obtaining methanol at the volume ratio (Н 5-СО5/СО-СО5), the so-called functional, equal to 2.03-5, 4, and a certain organization of the technological scheme, achieve the maximum production of carbon oxides in the methanol synthesis department, and hydrogen is obtained from the unreacted gas after purification. "

The problem is solved by the fact that in the method of obtaining hydrogen and methanol from converted gas, which contains carbon oxides and hydrogen, and includes the synthesis of methanol, according to the invention, for the synthesis of methanol

And they use converted gas with the functionality of H»-СО5/СО-СО5, which is equal to 2.03-5.4, which is served in и? a reactor system, which consists of a flow reactor or a cascade of flow reactors and/or a reactor with a gas mixture recycle, and hydrogen is obtained from the unreacted gas after purification.

For the synthesis of methanol, a part of the converted gas is taken, and the unreacted gas is directed to carbon monoxide conversion, carbon dioxide purification, and hydrogen production.

To obtain methanol, the converted gas, which is fed to the synthesis, is dosed with carbon dioxide, which is released at the stage of purification of the converted gas. o Part of the unreacted gas is used as hydrogen-containing gas before the desulfurization of the bundle gas that enters the conversion. o A distinctive feature of the method of obtaining hydrogen and methanol is the process of methanol synthesis at

Ф functionality, which is equal to 2.03-5.4, when all the converted gas is fed into the reactor system, which consists of a flow reactor or a cascade of flow reactors and/or a reactor with a gas mixture recycle, and at the same time the maximum activation of the amount of carbon oxides is obtained. The degree of transformation of carbon oxides reaches no

Less than 9390. The unreacted gas is immediately used as product hydrogen after the fusion reactor.

At the same time, the technological scheme is simplified due to the exclusion from it of the stages of carbon monoxide conversion and

P" cleaning from carbon dioxide, and the emission of carbon oxides into the air in the form of carbon dioxide is completely absent, unlike the prototype, where the emission of carbon dioxide is 420nm? at 100O0nm? convertible gas.

If only a part of the total converted gas flow is taken for the synthesis of methanol, then the second part of this flow along the hydrogen thread is directed to the conversion of carbon monoxide, while the purge gases of methanol synthesis are returned to the reactor of low-temperature conversion of carbon monoxide and used in full for the formation of hydrogen, the combined flow after conversion of carbon monoxide is submitted to absorption purification from carbon dioxide and product hydrogen is obtained.

Returning carbon dioxide after the stage of absorption purification to the flow of fresh gas supplied to the methanol synthesis reactor 65 brings the functionality of synthesis gas to stoichiometric - 2.03. At the same time, methanol productivity significantly increases, and carbon dioxide output decreases by 3.5 times compared to the prototype.

In addition, the unreacted gas is used as hydrogen-containing gas in the desulfurization stage of the natural gas entering the conversion, which also allows for maximum utilization of the off-gases.

Research has established that the advantages of joint production flow from the chemistry of interdependent reactions that describe the processes of obtaining hydrogen and methanol.

As mentioned above, technically pure hydrogen is obtained in the process of steam reforming of methane and other hydrocarbons with the subsequent conversion of carbon monoxide with water according to reactions (1), (2) and removal of carbon dioxide into the air from the gas mixture with solutions of potash and monoethanolamine. 70 During the joint production of hydrogen and methanol, carbon oxides are used as raw materials for the production of methanol in accordance with the following reactions:

СОо3Но-СНЗОнН-Ноа9.53KJ/mol (3);

СО2нН»-СНЗОНнОО, 7КДЖ/mol (4).

Thus, the carbon of natural gas is not thrown into the air, but is used to obtain a scarce 7/5 precious product - methanol, which increases the profitability of the entire production as a whole. In addition, in the process of methanol synthesis, product hydrogen is purified from carbon oxides.

For the initial converted gas, the limit of the volume ratio H2-СО5/СО-СО»5, the so-called functional, is proposed, from 2.03 to 5.4. This limit is chosen based on the following considerations. A decrease in the functional below 2.03, i.e. below stoichiometric, leads to a decrease in the production of product hydrogen, as well as to a 2o decrease in the degree of conversion of carbon oxides into methanol, and, therefore, to a deterioration in the purification of hydrogen supplied to the consumer from carbon oxides, which leads to additional costs to ensure the required level of cleaning.

In addition, if the functionality in the converted gas is below stoichiometric, methanol synthesis is characterized by a low speed and is accompanied by the passage of a large number of side reactions, which deteriorates the quality of raw methanol. The upper limit for the volumetric ratio of H "-СО5/СОСО", which is equal to 5.4, is determined by the fact that with a higher value of the functionality due to the lack of carbon oxides in the synthesis gas, the specific productivity of the methanol catalyst decreases, which leads to an increase in dimensions equipment of the methanol synthesis department.

The proposed method of obtaining hydrogen and methanol is explained by the diagram shown in the figure, where 1 is the conversion department; Gasoline 2 - recovery boiler;

C - recovery heat exchanger; o 4 - condensation and separation equipment; so 5 - compressor; 6 - department of methanol synthesis; Shcheo, 35 7 - methanol extraction system; "at 8 - fine purification of outgoing gas; 9 - high-temperature conversion of carbon monoxide; - low-temperature conversion of carbon monoxide; 11 - cleaning from carbon dioxide; « 12 - gas desulfurization. with c a, B, c, a, e, 7 - gas flows.

The proposed method is carried out as follows. Converted gas from conversion department 1, received ;" by steam or two-stage conversion of natural gas (the latter is a combination of steam and steam-oxygen conversion) enters the recovery boiler 2, in which energy steam is obtained due to the cooling of the converted gas. After the boiler-utilizer, the converted gas, which is directed to the synthesis of methanol, enters the recovery heat exchanger 3, passes through the heat utilization system, condensation and separation equipment 4 and, after separating the gas condensate, enters the suction of the compressor 5. Then the converted gas enters the methanol synthesis department 6. Reactor system of the methanol synthesis stage

Go! is a flow reactor or a cascade of flow reactors and/or a reactor with gas mixture recycling. In this case, the gas stream (stream a), which comes from the methanol extraction system 7, is sent to the thin o purification 8, without the use of high-temperature, low-temperature conversion of carbon monoxide and purification from

F of carbon monoxide. Part of the purge gases is advantageously supplied as gas containing hydrogen to the desulfurization unit 12, thereby saving product hydrogen. If methanol is obtained in a reactor with recycling, then to obtain hydrogen, the purge gases of the methanol synthesis cycle (stream b) are used, which are sent to fine purification 8, without the use of high-temperature 9 and low-temperature conversion of carbon monoxide 10 and purification from carbon dioxide 11, and circulating gas (flow c or a) using

P of the circulation compressor is returned to the methanol synthesis department 6 for mixing with fresh gas. Part of the purge gases is supplied to the desulfurization department 12.

In the case when it is necessary to change the ratio of plant capacities in the direction of increasing the capacities for water, the process is carried out as follows. After the conversion of natural gas 1, only a part of the converted gas is taken at the exit from the waste boiler 2 to the methanol synthesis unit 6, and the rest of the converted gas is sent along a hydrogen thread to the stage of high-temperature conversion of carbon monoxide. Blowing gases (flow e) are returned to the hydrogen thread, part of this flow after heating to a temperature of 220-2507C in the recovery heat exchanger C (flow 7 is returned to the low-temperature conversion of carbon monoxide 10 with subsequent cleaning of the combined flow from carbon dioxide in 11. Part purge gases (stream 4) are fed to the desulfurization department 12.

The proposed method allows you to vary the composition of the synthesis gas, supplying part of the carbon dioxide after 11 to the suction of the compressor 5, while reducing the emission of carbon dioxide into the air. At the same time, the degree of use of the carbon component of natural gas increases accordingly.

The following examples are proof of the implementation of the proposed method.

Example 1 (comparative).

The installation for obtaining gas, which is used for the synthesis of hydrogen and methanol, is supplied with 3,000 Okg of heavy oil fraction, which is mixed with oxygen obtained at the air distribution installation, then by the method of partial oxidation, synthesis gas with a functionality of 0.85 is obtained. Synthesis gas is fed to the desulphurization unit 70 for purification from compounds that contain sulfur. Purified synthesis gas in the amount of 91,000 cubic meters is fed to the methanol synthesis in a flow reactor for a single pass.

The synthesis of methanol is carried out in the presence of a copper catalyst at an inlet gas temperature of 230°C, an outlet gas temperature of 2707°C, and a synthesis pressure of 100 bar. During a single passage of the synthesis gas, the reaction yields 8–994 nm/h of crude methanol. The amount of unreacted gas is 63,846 bcm/ h is directed to the conversion of carbon monoxide 75. The resulting gas is washed from carbon dioxide and 617 bOnm/h of raw hydrogen is obtained.

The test results are shown in the table.

Example 2

Converted gas under a pressure of 2.0-2.5 MPa with a functional H2-СО5/СОСО»5 equal to 5.4, obtained at the stage of gas preparation by steam or two-stage steam-oxygen conversion, is fed for cooling to the recovery boiler to obtain energy steam . The temperature of the converted gas after cooling is 360-380". After the recovery boiler, all the converted gas is sent to the recovery heat exchanger 3, then passed through a system that uses the heat of the condensation and separation equipment, separated from the gas condensate and fed to the suction of the compressor. Next, the converted gas enters into a system of two flow reactors for the synthesis of methanol. The synthesis is carried out under a pressure of 5.0-5.5MPa and a temperature of 200-2607"С on a copper-zinc-aluminum catalyst. The unreacted gas, after the separation of methanol, is given to the consumer as a food hydrogen If it is necessary to reduce the content of impurities in the product water, condense crude methanol at reduced temperatures, while using recycled water with a lower temperature or another refrigerant. The test results are shown in the table.

Example C (se)

The tests are carried out as in example 2, but for the synthesis of methanol, converted gas with a functional of 2.97 is supplied and the process is carried out in a reactor with a gas mixture recycle. To ensure the required ratio of hydrogen and methanol capacities, the consumption of converted gas supplied to the synthesis reactor is equal to approximately 4395 of the total flow of converted gas supplied to the plant.

The remainder of the flow (5795), bypassing the synthesis of methanol, is fed to the high-temperature conversion of carbon monoxide. and

The unreacted gas from the methanol synthesis section, heated in the recovery heat exchanger to 2507C, (Ce) is combined with the stream (5795) selected for the production of hydrogen before the low-temperature conversion of carbon monoxide, after which the gas is fed to absorption purification from carbon dioxide and obtain product hydrogen.

The test results are shown in the table. "

Example 4

The tests are carried out as in example 3, but return 9OOnm/h of carbon dioxide after stage - s of absorption purification from carbon dioxide into the stream of fresh gas, which is fed into the methanol synthesis reactor. and Synthesis gas functionality is brought to the stoichiometric value of 2.03. At the same time, the power of methanol increases significantly, and the emission of carbon monoxide and carbon dioxide decreases. The test results are shown in the table.

Example 5 (o) Tests are carried out as in example 2, but the synthesis of methanol is supplied with a converted gas with a functional sl of 2.05, and the synthesis of methanol is carried out in a reactor with a recycle. At the same time, all converted gas supplied to the plant is sent to the methanol synthesis department. The purge gases of the methanol synthesis cycle are directed (ee) to fine purification from impurities and receive 10095th hydrogen. The test results are shown in the table. p. 50 Example 6

The tests are carried out as in example 2, but for the synthesis of methanol, a converted gas with a 4) functional of 2.43 is supplied, and the synthesis of methanol is carried out sequentially in a flow reactor and in a reactor with a recycle.

At the same time, all converted gas supplied to the plant is sent to the methanol synthesis department. The unreacted gas after the recycle reactor with a hydrogen content of 86.43956 is either given to the consumer as product hydrogen or sent to fine purification from impurities. The results of the tests are given in the table.

As can be seen from the examples, the operation of the unit on converted gas with a functionality of 2.03-5.4 allows to increase the degree of conversion of the amount of carbon oxides from 18.6395, achieved in the prototype, to 93.68-96.2390 in the proposed method. At the same time, the emission of carbon dioxide 60 into the air is either completely eliminated or significantly reduced: from 42o0nm/1000nm of converted gas in the prototype to 124nm?/1000nm? converted gas in the proposed method. When the ratio of hydrogen to methanol productivity varies from 0.578 to 0.010, even under comparative conditions (0.577tN 2/1 SNZON in the prototype and 0.578tNoSNZON in the proposed method), the emission of carbon oxides is 3.4 times less.

Based on the above, it can be concluded that the proposed method of obtaining hydrogen and b5 methanol allows you to flexibly vary the ratio of capacities for hydrogen and methanol, based on the demand situation, to use raw materials more efficiently, to significantly reduce the loss of its carbon component, and to improve the environmental performance of the process due to reduction of emissions of carbon oxides into the air.

Mo Name of indicators (Units Example 1 Example 2 Example C Example 4 / Example 5 | Example 6 n/n of measurement 35117613 1 Converted gas per nmU/h 91000 150000 30857 30857 то00о0 112192 hydrogen and methanol production plant: consumption "vm 1-1 19520200 0

The number of SOZHSO" 41884 22500 6692.88 6692.88 21343 30168 5 battle metnyulutostdyamo 00000011 ?о00ожжеютеу 00000000 мя 100131000800100501 5015350

Type of reactors Flow-through - - - Flow-through

Number of reactors 1 2 1 - - with recyl! )| with recycle!1 |with recycle!1 |with recycle!1

Selection of converted gas for methanol synthesis: 25 91000 150000 13250 13250 t0000 | 112192 "

Dosing of CO" from the nmZ/h purification department for methanol synthesis:

Consumption (se) 30 Converted gas for synthesis nmU/h 91000 150000 13250 14150 70000 112192 methanol: IF) consumption of

Composition: Uoob. 46.48 84.0 75.94 71.11 67.39 71.73 2 years in 10000001 and 1956026 6110595

Amount of CO2 41885 22500 2874 3773 21343 30168 -in s Functional 0.85 BA 2.97 2.03 2.05 2.A3

Non-COg/CO CO" . and? 2.1 |Synthesis of methanol in flow reactors 2.1.3 Gas at the exit from flow nmU/h 87805 89730 1 reactors: costs

F ov 1387 » season to 10095 SNZON 8920 21077 10579 2.1.5 Degree of conversion to 18.63 93.68 35.06

SovSoO" into methanol 2.2 Synthesis of methanol in a reactor with recycle 65 2.2.1 Catalyst volume m 15.5 15.5 61 61 teye plo blya 0732 ni i p PIT bu | oyu son ny PC SL 2.2.A Gas at the entrance/exit in 130000 139423 600000 | 600,000

Composition: CO» 2.08/1.03 7.18/5.84 4.30/4.10 2.62/1.73 75 85.92/84.15 | 58.68/54.68 | 61.74/58.44 | 84.64/82.59 041.29 021195 007060 | 01/18 2.12 and 2.22 0 DAD /12.18/13.06 | 2.89/3.08

To21, Ba | 22.70123.94 | 9.6910.40 | 5.08/5.40 1980/1092 | 2.91/205 | 11.24/8.96 | 3.93/2.08 snzon 0.64/2.87 0.84/3.64 0.77/4 A 0.74/3.95 2.2.5 Methanol-raw t/h 5.044 7.146 31.684 31.211 10096- she methanol 3,891 5,185 28,847 26203 2.2.6 Total amount of t/h 5,044 7,147 31,684 46,87 obtained crude methanol 100th SNZON 12,74 30,11 3,891 5,185 28,847 41,32 « Total degree of conversion, 2.2.186 93.68 96.23 95.97 94.61 95.86

SovsCo»5 into methanol in the synthesis department 2.2.8 Unreacted gas, with nmZ/h 63846 81670 3643 873 5У76 17261 (Се) from the synthesis of methanol to obtain hydrogen: costs of IF) 37.6 96.67 8749 БТ2В 61, 00 86.32

BEAR DROUGHT KN

VAZ sno « vva - z vdeant 7771011; - 3.1.1 Selection of the initial con. gas per nmU/h 17607 17607 conversion of carbon monoxide to methanol synthesis: costs (in terms of dry gas) 33109 33109

1718 3.1.3 Temperature at the inlet/outlet 345/390 345/390 at the stages of high-temperature conversion CO with BAN - Я - - - s -- - Р - - -х Е Е ЕЕЕ« Е 2 Е 5 - - - - 3.1.2 Return of gas from the separation nmU/h 63846 3178 573 about synthesis for CO conversion after selection for sulfur purification: expenses » n PO SE Zlo POL ti NO PONG g i PE slov PE ti NO PON vva 11 сНнзОон - 0.71 0.94 65 conversion of carbon monoxide AFTER SEPARATION OF GAS CONDENSATE: consumption byu 10001115 pi 1000011 ni p PO PO POLYA POLYA m 10000120 in 1601

SHISHISHZY-202 2 « « ЗР 252 32 Purification of exhaust 11111111 them (88 Vydozhyutyvyasso 00 pair, 000000 Apooranya yara 02000007 shi 1 11 released into the air

Ash 1 122121 domMmISHOK 41 Type of fine cleaning Separation of KCA bo shen cooling (I1-0"7C) and cleaning: consumption of

M OO POLYA POLYA POLYA PC ET

WE CARRY OUR SUS, BUT OURS ON NOAH

POS ZY SU VYN NO ZNNYA NOOE ZO NO NOYA

11021081 0 » 60000008 yu oy | oo you Output convertible basin: 11111110 of 5 F sunchotvya soy 000000008500000085400000028701002050 205243 « 6.3 | Amount of received 10055-nmZ/h 8920 21077 2124 3630 20193 28924

RN se: nie: NN Eh SHE YAN NE p

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Claims (4)

Formula of the invention p. 50 Ф 1. The method of obtaining hydrogen and methanol from converted gas, which contains carbon oxides and hydrogen, and includes the synthesis of methanol, which is distinguished by the fact that for the synthesis of methanol, converted gas with the functionality Н»-СО5/СО-СО5, which is equal to 2, is used, 03-5.4, which is fed into the reactor system, which consists of a high-pressure flow reactor or a cascade of flow reactors, and/or a reactor with a gas mixture recycle, and hydrogen is obtained from the unreacted gas after purification. P 2. The method according to claim 1, which differs in that a part of the converted gas is taken for the synthesis of methanol, and the unreacted gas is directed to the conversion of carbon monoxide, purification from carbon dioxide and production of hydrogen. in C. The method according to claim 2, which differs in that, to obtain methanol, carbon dioxide released at the stage of purification of the converted gas is dosed into the converted gas, which is fed to the synthesis. 4. The method according to claims 1-3, which differs in that part of the gas that did not react is used as gas containing hydrogen before the desulfurization of the synthesis gas that enters the conversion. b5