Alcohol / ammonia synthesis process, device and reactor adapting to large fluctuation of renewable energy sources

Abstract

The invention provides an alcohol / ammonia synthesis process capable of greatly fluctuating renewable energy sources, a plurality of reactors with different sizes are arranged in the alcohol / ammonia synthesis process, the large reactor is filled with 60-90% of catalyst, and the small reactor is filled with 10-40% of catalyst. The technological process is rapidly switched only through simple valve adjustment, different production loads are met, control is easy, response is rapid, and rapid fluctuation of renewable energy sources is dealt with. The invention also discloses an alcohol / ammonia synthesis device and a multi-stream heat exchange reactor suitable for the process.

Description

Technical Field

[0001] The invention relates to chemical synthesis to consume renewable energy, and in particular to an alcohol / ammonia synthesis process and device and a reactor with large fluctuations in renewable energy. Technical Background

[0002] Renewable energy is affected by natural environmental factors. The energy input and power output in the power generation process cannot be precisely controlled like thermal power generation. Its large fluctuations, intermittent, random and uncontrollable characteristics make it difficult to directly integrate into the power grid for use, which has also led to the large-scale abandonment of renewable energy equipment.

[0003] As a way to consume renewable energy locally, the production of methanol and synthetic ammonia from carbon dioxide hydrogenation can effectively improve energy utilization and avoid abandoning renewable energy equipment. At present, many renewable energy alcohol / ammonia projects have been planned in China, namely, renewable energy gasification, carbon dioxide hydrogenation to methanol, or ammonia synthesis from nitrogen and hydrogen in the air and subsequent refining stages. As a typical chemical plant, the operating flexibility of methanol / ammonia synthesis is generally 50% to 120%, and it will be difficult to operate the plant outside this range. Since renewable energy not only fluctuates frequently, but also has a wide fluctuation range, if it is not peaked, it can only be abandoned when the power generation is low, which reduces the energy utilization efficiency. At the same time, the synthesis unit must be shut down. The frequent start and stop of the unit will greatly reduce the service life of the unit and the catalyst, affecting the safe operation of the equipment.

[0004] To solve this problem, some research has been carried out in China. Generally speaking, they all store a part of the electricity through mechanical energy storage, chemical energy storage and other methods when the power generation peaks, and the rest of the electricity is supplied to the methanol / ammonia synthesis device. When the power generation is low, the stored energy is used to generate electricity to supplement the renewable energy supply to the methanol / ammonia synthesis device. These methods can avoid the waste of energy caused by the abandonment of renewable energy devices to a certain extent, and at the same time can keep the synthesis device running continuously and avoid frequent start-up and shutdown, but the cost is too high and the engineering difficulty is very high. Summary of the invention

[0005] The purpose of the present invention is to provide an alcohol / ammonia synthesis process with large fluctuations in renewable energy. By improving the alcohol / ammonia synthesis process route, an operational flexibility of 10% to 120% can be achieved, and the synthesis device can continue to operate stably when the renewable energy power supply is at a peak or trough.

[0006] An alcohol / ammonia synthesis process adapting to large fluctuations in renewable energy includes synthesis and product separation. Fresh gas is mixed with circulating gas to form synthesis gas. The fresh gas used for synthesizing methanol refers to a gas obtained by mixing hydrogen produced from renewable energy and CO2 in a certain proportion. The fresh gas used for synthesizing ammonia refers to a gas obtained by mixing hydrogen produced from renewable energy and N2 extracted from the air in a certain proportion. The alcohol / ammonia synthesis process is provided with a plurality of reactors of different sizes, wherein a large reactor is filled with 60-90% of the catalyst amount, and a small reactor is filled with 10-40% of the catalyst amount. When there are a plurality of large reactors, the catalyst loading amount of a single large reactor is greater than or equal to the catalyst loading amount of a single small reactor.

[0007] As a preference, the multiple reactors are two reactors of different sizes, the large reactor is filled with 80% of the catalyst, and the small reactor is filled with 20% of the catalyst.

[0008] The alcohol / ammonia synthesis process is adjusted as follows when the system has different loads:

[0009] When the alcohol / ammonia synthesis process is operated at a low load of 10% to 25%, the synthesis gas only passes through the catalyst bed of the small reactor, and the outlet gas of the small reactor enters the large reactor to provide heat to maintain the temperature of the catalyst layer. When the load is added in the future, the large reactor does not need to go through a heating process and can be started immediately.

[0010] When the alcohol / ammonia synthesis process is operated at a low load of 25% to 50%, the large reactor is activated, and the synthesis gas enters the large reactor and the small reactor respectively after being preheated. The synthesis gas can also be separated into another mixed gas that is not preheated according to demand and mixed with the preheated mixed gas entering the small reactor. The outlet gas of the small reactor is mixed with the inlet gas of the large reactor and then enters the large reactor to achieve thermal balance of the large reactor and avoid deactivation due to too little reaction heat.

[0011] When the alcohol / ammonia synthesis process is operated at a load of 50% to 120%, the large reactor and the small reactor are connected in parallel, and the synthesis gas enters the large reactor and the small reactor respectively after being preheated. The synthesis gas can also be separated into another non-preheated mixed gas according to demand and mixed with the preheated mixed gas entering the small reactor. The outlet gas of the small reactor is mixed with the outlet gas of the large reactor and used to heat the synthesis gas.

[0012] As a preference, the large reactor is a multi-stream heat exchange reactor, and the heat exchange medium can be boiler water or gas or heat transfer oil or molten salt.

[0013] As a preference, the small reactor can be an air-cooled reactor or an adiabatic reactor.

[0014] An alcohol / ammonia synthesis device adapting to large fluctuations in renewable energy comprises a compressor, a circulation machine, a heat exchanger, a cooler, a multi-stream heat exchange reactor, a small reactor and a separator, wherein the compressor outlet is connected to the circulation machine outlet and the heat exchanger, the shell side outlet of the heat exchanger is divided into two paths and respectively connected to the multi-stream heat exchange reactor and the small reactor, the outlet of the small reactor is respectively connected to the reaction gas outlet pipeline, the reaction gas inlet pipeline and the heat exchange medium inlet pipeline of the multi-stream heat exchange reactor through pipelines with control valves, and then connected to the tube side inlet of the heat exchanger, the tube side outlet of the heat exchanger is connected to the cooler and the separator in sequence; the reaction gas inlet pipeline, the reaction gas outlet pipeline, the heat exchange medium inlet pipeline and the heat exchange medium outlet pipeline of the multi-stream heat exchanger are all provided with control valves, and a bypass with a control valve is provided in front of the heat exchanger inlet to connect to the inlet of the small reactor.

[0015] When the above device is in operation, according to different load processes, the control valves on each pipeline are opened or closed to make the device operate as follows:

[0016] 10% to 25% low load process: the fresh gas pressurized by the compressor is mixed with the circulating gas compressed by the circulating machine, and then heat exchanged with the outlet gas of the multi-stream heat exchange reactor in the heat exchanger, and then enters the small reactor. The outlet gas of the small reactor enters at least one group of heat exchange tube bundles of the multi-stream heat exchange reactor to provide heat to the catalyst layer of the multi-stream heat exchange reactor to maintain the temperature of its catalyst. The outlet gas of the multi-stream heat exchange reactor is cooled by heat exchange in the heat exchanger and the cooler, and then enters the separator to separate the coarse product. The separated gas is divided into two streams, one of which is used as circulating gas to be compressed by the circulating machine, and the rest is used as relaxation gas.

[0017] 25% to 50% low load process: the fresh gas pressurized by the compressor is mixed with the circulating gas compressed by the circulating machine to form synthesis gas, the synthesis gas is heat exchanged with the outlet gas of the multi-stream heat exchange reactor in the heat exchanger and then enters the multi-stream heat exchange reactor and the small reactor respectively, and the synthesis gas can also be separated into another mixed gas without preheating according to demand and mixed with the preheated mixed gas entering the small reactor, the outlet gas of the small reactor is mixed with another heated inlet gas of the multi-stream heat exchange reactor and then enters the multi-stream heat exchange reactor, the outlet gas of the multi-stream heat exchange reactor is cooled by heat exchange in the heat exchanger and the cooler, and then enters the separator to separate the crude product, and the separated gas is divided into two streams, one of which is used as the circulating gas to be compressed by the circulating machine, and the rest is used as the relaxation gas.

[0018] 50% to 120% load process: the fresh gas pressurized by the compressor is mixed with the circulating gas compressed by the circulating machine to form synthesis gas, and then the synthesis gas is heat exchanged with the outlet gas of the multi-stream heat exchange reactor in the heat exchanger and enters the multi-stream heat exchange reactor and the small reactor respectively. The synthesis gas can also be separated into another mixed gas without preheating according to demand and mixed with the preheated mixed gas entering the small reactor. The outlet gas of the multi-stream heat exchange reactor and the outlet gas of the small reactor are mixed and cooled by heat exchange and cooler, and then enter the separator to separate the crude product. The separated gas is divided into two streams, one of which is used as the circulating gas to be compressed by the circulating machine, and the rest is used as relaxation gas.

[0019] As a preference, the heat exchange medium of the multi-stream heat exchange reactor may be boiler water or gas or heat transfer oil or molten salt.

[0020] As a preference, the small reactor is an air-cooled reactor or an adiabatic reactor.

[0021] A multi-stream heat exchange reactor for the above-mentioned alcohol / ammonia synthesis process that adapts to large fluctuations in renewable energy. The heat exchange tubes in the alcohol / ammonia synthesis reactor are divided into at least two groups of heat exchange tube bundles, each group of heat exchange tube bundles carries different heat exchange media, and the heat exchange tube spacing of the heat exchange tube bundles is 6 to 10 times the diameter of the catalyst loaded between the tubes.

[0022] As a preference, the distance between the heat exchange tubes of the heat exchange tube bundle is 6 to 8 times the diameter of the catalyst loaded between the tubes.

[0023] The process route of the present invention is simple and easy to implement. While improving the safety and stability of the production device, it can greatly improve the energy utilization rate and avoid the abandonment of wind and photovoltaic power. It has the following innovations and advantages:

[0024] 1. Set up multiple reactors of different sizes, with large reactors filled with 60-90% of the catalyst, and small reactors filled with 10-40% of the catalyst, which can adapt to the production load fluctuations caused by renewable energy fluctuations, improve energy utilization when renewable energy supply is low, and each reactor can operate within the safe production load range to avoid frequent start-up and shutdown of the reactor. At the same time, there is no need to set up peak-shaving devices to smooth out fluctuations, reducing investment and engineering implementation difficulties.

[0025] 2. According to the different load conditions of the system, the opening and operating modes of multiple reactors are adjusted. The process flow can be quickly switched by simply adjusting the valves to meet different production loads. The control is simple and the response is fast to cope with the rapid fluctuations of renewable energy. For example, when the load is low at 10% to 25%, only the small reactor is turned on, and the outlet gas of the small reactor is used to enter the large reactor for insulation. When the load is added in the future, the large reactor does not need to go through the heating process and can be started immediately; when the load is low at 25% to 50%, the large reactor and the small reactor are enabled at the same time to achieve thermal balance of the large reactor to avoid deactivation due to low reaction heat; when the load is 50% to 120%, the large reactor is connected in parallel with the small reactor, and each reactor operates independently, which is easy to operate and control.

[0026] 3. The large reactor adopts a multi-stream heat exchange reactor. During operation, a variety of heat exchange media can be selected for efficient heat exchange and effective control of the catalyst bed temperature. When it is stopped, the outlet gas and heat exchange medium of the small reactor can be used to keep the reactor warm and maintain a hot standby state, which can be started immediately when the load is added. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a simplified flow chart of the device of the present invention.

[0028] Figure 2 This is a flow chart of the process of the present invention when used for the synthesis of green alcohol with disorderly and large fluctuations in wind and photovoltaic power at a load of 10 to 25%.

[0029] Figure 3 This is a flow chart of the process of the present invention under a load of 25-50% when the process is used for the synthesis of green alcohol with disorderly and large fluctuations in wind and photovoltaic power.

[0030] Figure 4 This is a flow chart of the process of the present invention under a load of 50 to 120% when the process is used for the synthesis of green alcohol with disorderly and large fluctuations in wind and photovoltaic power.

[0031] Description of reference numerals:

[0032] C1- compressor C2- circulation machine R1- multi-stream heat exchange reactor R2- small reactor

[0033] E1-heat exchangerE2-coolerS1-separatorS2-steam drum

[0034] V1-first valve V2-second valve V3-third valve V4-fourth valve

[0035] V5-fifth valve V6-sixth valve V7-seventh valve DETAILED DESCRIPTION

[0036] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0037] Example 1

[0038] like Figure 1 As shown, the alcohol / ammonia synthesis device adapting to large fluctuations in renewable energy of the present invention comprises a compressor C1, a circulation machine C2, a heat exchanger E1, a cooler E2, a multi-stream heat exchange reactor R1, a small reactor R2 and a separator S1, wherein the outlet of the compressor C1 is connected to the outlet of the circulation machine C2 and the inlet of the heat exchanger E1, the shell-side outlet pipeline of the heat exchanger E1 is divided into two routes, one of which is provided with a first valve V1 and connected to the multi-stream heat exchange reactor R1, and the other is connected to the small reactor R2, the outlet of the small reactor R2 is divided into two routes, one of which is provided with a second valve V2 and is divided into two routes, and one of which is provided with a sixth valve V6 and connected to the outlet of the multi-stream heat exchange reactor E1. The reaction gas inlet pipeline is connected, and the other branch of the outlet pipeline of the small reactor R2 is provided with a fifth valve V5 connected to the heat exchange medium inlet pipeline of the multi-stream heat exchange reactor E1; the other branch of the outlet pipeline of the small reactor R2 is provided with a third valve V3 connected to the reaction gas outlet pipeline and the heat exchange medium outlet pipeline of the multi-stream heat exchange reactor, and then connected to the tube side inlet of the heat exchanger E1, and the tube side outlet of the heat exchanger E1 is connected to the cooler E2 and the separator S1 in sequence, and the heat exchange medium outlet pipeline of the multi-stream heat exchange reactor is provided with a seventh valve V7, and the shell side inlet of the heat exchanger E1 is provided with a bypass of the fourth valve V4 connected to the inlet pipeline of the small reactor R2. The gas outlet of the separator S1 is divided into two paths, one of which is connected to the circulation machine C2, and the other is the relaxation gas.

[0039] The above device is used in the green alcohol synthesis process. The multi-stream heat exchange reactor adopts a reactor with a spiral winding tube structure. The catalyst in the reactor is installed between the tubes. The heat exchange tubes in the multi-stream heat exchange reactor R1 are divided into two groups of heat exchange tube bundles, which respectively carry steam and reaction gas. The heat exchange tube spacing of the heat exchange tube bundle is 8 times the diameter of the catalyst loaded between the tubes. The multi-stream heat exchange reactor R1 is connected to the steam drum S2. In order to adapt to the disordered and large fluctuations of wind and photovoltaic power, the valves of each pipeline are opened or closed when the system is in different load states, so that the system operates according to the following requirements:

[0040] 10% to 25% low load process: open the second valve V2, the fifth valve V5, and the seventh valve V7, and close the first valve V1, the third valve V3, the fourth valve V4, and the sixth valve V6. The operation process of the device under this load state is as follows: Figure 2As shown, the fresh gas pressurized by the compressor C1 is mixed with the circulating gas compressed by the circulating machine C2, and then heat exchanged with the outlet gas of the multi-stream heat exchange reactor E1 to 170°C in the heat exchanger E1, and then enters the small reactor E2. The outlet gas of the small reactor E2 enters a part of the heat exchange tubes of the multi-stream heat exchange reactor E1 to keep the idle multi-stream heat exchange reactor E1 warm. The outlet gas of the multi-stream heat exchange reactor E1 is cooled to 40°C through heat exchange between the heat exchanger E1 and the water cooler E2, and then enters the separator S1 to separate the crude methanol. The separated gas is divided into two streams, one of which is used as the circulating gas to be compressed by the circulating machine C2, and the rest is used as the relaxation gas.

[0041] 25% to 50% low load process: open the first valve V1, the second valve V2, the fourth valve V4, and the sixth valve V6, and close the third valve V3, the fifth valve V5, and the seventh valve V7. The operation process of the device under this load state is as follows: Figure 3 As shown in the figure, the fresh gas compressed by the compressor C1 is mixed with the circulating gas compressed by the circulating machine C2 and then divided into

[0042] Two streams, one of which is heat exchanged with the outlet gas of the multi-stream heat exchange reactor R1 to 210℃ in the heat exchanger E1 and then divided into two streams, one of which is mixed with the other mixed gas that has not been heat exchanged, and the temperature after mixing is 170℃, and then enters the small reactor R2, the outlet gas of the small reactor R2 is mixed with the other heated inlet gas and then enters the multi-stream heat exchange reactor R1, the outlet gas of the multi-stream heat exchange reactor R1 is cooled to 40℃ through heat exchange in the heat exchanger E1 and the cooler E2, and then enters the separator S1 to separate the crude methanol, and the separated gas is divided into two streams, one of which is used as circulating gas to be compressed by the circulating machine C2, and the rest is used as relaxation gas.

[0043] 50% to 120% load process: open the first valve V1, the third valve V3, and the fourth valve V4, and close the second valve V2, the fifth valve V5, the sixth valve V6, and the seventh valve V7. The operation process of the device under this load state is as follows: Figure 4 As shown, the fresh gas pressurized by the compressor C1 is mixed with the circulating gas compressed by the circulating machine C2 and then divided into two streams, one of which is heat exchanged with the outlet gas of the multi-stream heat exchange reactor R1 to 210°C in the heat exchanger E1 and then divided into two streams, one of which directly enters the multi-stream heat exchange reactor R1, and the rest is mixed with the other mixed gas that has not been heat exchanged. The temperature after mixing is 170°C, and then enters the small reactor R2. The outlet gases of the multi-stream heat exchange reactor R1 and the small reactor R2 are mixed and cooled to 40°C through heat exchanger E1 and cooler E2, and then enter the separator S1 to separate the crude methanol. The separated gas is divided into two streams, one of which is used as the circulating gas to be compressed by the circulating machine C2, and the rest is used as the relaxation gas.

Claims

1. An alcohol / ammonia synthesis process adapting to large fluctuations in renewable energy, including synthesis and product separation, fresh gas and recycled gas are mixed to form a mixed gas, characterized in that: In the alcohol / ammonia synthesis process, multiple reactors of different sizes are arranged, the large reactor is filled with 60-90% of the catalyst, and the small reactor is filled with 10-40% of the catalyst. The synthesis process is adjusted as follows when the system has different loads: When the alcohol / ammonia synthesis process is operated at a low load of 10% to 25%, the mixed gas only passes through the catalyst bed of the small reactor, and the outlet gas of the small reactor enters the large reactor to provide heat to maintain the temperature of the catalyst layer. When the load is added in the future, the large reactor does not need to go through a heating process and can be started immediately. When the alcohol / ammonia synthesis process is operated at a low load of 25% to 50%, the large reactor is activated, the mixed gas is divided into two streams, one stream is preheated and enters the large reactor and the small reactor respectively, and the other stream of mixed gas that is not preheated is mixed with the preheated mixed gas entering the small reactor, and the outlet gas of the small reactor is mixed with the inlet gas of the large reactor and then enters the large reactor, so as to achieve thermal balance of the large reactor and avoid deactivation due to too little reaction heat; When the alcohol / ammonia synthesis process is operated at a load of 50% to 120%, the large reactor and the small reactor are connected in parallel, the mixed gas is divided into two streams, one stream enters the large reactor and the small reactor respectively after preheating, and the other stream of mixed gas without preheating is mixed with the preheated mixed gas entering the small reactor, and the outlet gas of the small reactor is mixed with the outlet gas of the large reactor to heat the mixed gas.

2. The alcohol / ammonia synthesis process adapted to large fluctuations in renewable energy as claimed in claim 1, characterized in that: The multiple reactors are two reactors of different sizes, the large reactor is filled with 80% of the catalyst, and the small reactor is filled with 20% of the catalyst.

3. The alcohol / ammonia synthesis process adapted to large fluctuations in renewable energy as claimed in claim 1, characterized in that: When there are multiple large reactors, the catalyst loading capacity of a single large reactor is greater than or equal to the catalyst loading capacity of a single small reactor.

4. The alcohol / ammonia synthesis process adapted to large fluctuations in renewable energy as claimed in claim 1, characterized in that: The large reactor is a multi-stream heat exchange reactor, and the heat exchange medium can be boiler water or gas or heat transfer oil or molten salt.

5. The alcohol / ammonia synthesis process adapting to large fluctuations in renewable energy as claimed in claim 1, characterized in that: The small reactor is a small reactor, which can be an air-cooled reactor or an adiabatic reactor.

6. An alcohol / ammonia synthesis device that can adapt to large fluctuations in renewable energy, comprising a compressor, a circulator, a heat exchanger, a cooler, a multi-stream heat exchange reactor, a small reactor and a separator, characterized in that: The compressor outlet is connected to the circulation machine outlet and the heat exchanger. The shell side outlet of the heat exchanger is divided into two routes and respectively connected to the multi-stream heat exchange reactor and the small reactor. The outlet of the small reactor is respectively connected to the reaction gas outlet pipeline, the reaction gas inlet pipeline and the heat exchange medium inlet pipeline of the multi-stream heat exchange reactor through pipelines with control valves, and then connected to the tube side inlet of the heat exchanger. The tube side outlet of the heat exchanger is connected to the cooler and the separator in sequence. The shell side inlet pipeline, the shell side outlet pipeline, the tube side inlet pipeline and the tube side outlet pipeline of the multi-stream heat exchanger are all provided with control valves. A bypass with a control valve is provided in front of the heat exchanger inlet to connect the inlet of the small reactor.

7. The alcohol / ammonia synthesis device capable of adapting to large fluctuations in renewable energy as claimed in claim 6, characterized in that: The heat exchange medium of the multi-stream heat exchange reactor can be boiler water or gas or heat transfer oil or molten salt.

8. The alcohol / ammonia synthesis device capable of adapting to large fluctuations in renewable energy as claimed in claim 6, characterized in that: The small reactor is an air-cooled reactor or an adiabatic reactor.

9. A multi-stream heat exchange reactor for an alcohol / ammonia synthesis device that can adapt to large fluctuations in renewable energy as claimed in claim 6, characterized in that: The heat exchange tubes in the multi-stream heat exchange reactor are divided into at least two groups of heat exchange tube bundles, each of which carries different heat exchange media. The distance between the heat exchange tubes in the heat exchange tube bundle is 6 to 10 times the diameter of the catalyst loaded between the tubes.

10. The multi-stream heat exchange reactor according to claim 9, characterized in that: The distance between the heat exchange tubes of the heat exchange tube bundle is 6 to 8 times the diameter of the catalyst loaded between the tubes.

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