A heat coupling device suitable for adsorption enhanced ammonia synthesis

Abstract

The present application relates to a kind of heat coupling device suitable for adsorption enhanced ammonia synthesis, comprising reactor, first adsorption tower and second adsorption tower, the inlet of the reactor is connected with hydrogen nitrogen mixture gas source;The first adsorption tower and second adsorption tower are same structure, its gas outlet simultaneously with the inlet of the reactor is connected, its gas inlet simultaneously after the tube side of first heat exchanger with the outlet of the reactor is connected, its heat transfer agent inlet simultaneously after the shell side of first heat exchanger with the liquid outlet of high-temperature heat transfer agent tank is connected, its heat transfer agent outlet simultaneously with the liquid return port of high-temperature heat transfer agent tank is connected;The gas outlet of this first adsorption tower and second adsorption tower also simultaneously after condenser with liquid ammonia storage tank is connected.Thereby, two adsorption towers can be operated adsorption and desorption process respectively at the same time.Thereby, the waste heat of reactor outlet gas can be effectively utilized, and it is conducive to energy saving and environmental protection.

Description

Technical Field

[0001] This invention relates to the field of chemical production, and in particular to an ammonia synthesis production system, specifically a thermal coupling device suitable for adsorption-enhanced ammonia synthesis. Background Technology

[0002] In traditional industry, ammonia synthesis is mainly carried out using the Habor-Bosch process. This reaction typically requires high temperature (673K~773K) and high pressure (>100 bar), and the single-pass conversion rate is only around 20%. It necessitates cooling at low temperature (<-15℃) to separate liquid ammonia before recycling the remaining gases to achieve a total conversion rate exceeding 99%. This method is energy-intensive and has high investment costs.

[0003] Currently, separation-enhanced ammonia synthesis technologies, such as adsorption-enhanced ammonia synthesis, have emerged, which can reduce the operating pressure of the ammonia synthesis process. This technology mainly uses metal halides or corresponding complexes as adsorbents, releasing adsorbed ammonia through a temperature-switching adsorption process, followed by cooling or pressurization to obtain liquid ammonia, or directly using the released ammonia to produce downstream products. This replaces the ammonia cooling step in traditional processes, effectively removing ammonia from the circulating gas and significantly reducing the required pressure of the overall ammonia synthesis cycle. However, since the desorption and release of ammonia requires high-temperature driving, currently electric heating is mainly used to drive desorption, introducing additional electricity consumption. This results in higher overall energy consumption than traditional ammonia synthesis processes, which is not conducive to energy conservation and environmental protection.

[0004] Therefore, improvements are urgently needed to better meet production demands. Summary of the Invention

[0005] The purpose of this invention is to address the problems encountered in the current adsorption-enhanced ammonia synthesis production and to provide a thermal coupling device suitable for adsorption-enhanced ammonia synthesis. This device can efficiently recover and utilize the waste heat from the ammonia synthesis reaction process without introducing additional energy consumption, and transfer it to the adsorption bed, so that the temperature of the adsorption bed can be rapidly switched and maintained stably during the cycle of temperature-variable adsorption.

[0006] The technical solution of this invention is: A thermal coupling device suitable for adsorption-enhanced ammonia synthesis includes a reactor, a first adsorption tower, and a second adsorption tower. The inlet of the reactor is connected to a hydrogen-nitrogen mixed gas source. The first and second adsorption towers have identical structures, with their outlets simultaneously connected to the inlet of the reactor. Their inlets simultaneously pass through the tube side of a first heat exchanger and are connected to the outlet of the reactor. Their heat exchanger inlets simultaneously pass through the shell side of the first heat exchanger and are connected to the liquid outlet of a high-temperature heat exchanger tank. Their heat exchanger outlets simultaneously connect to the liquid return port of the high-temperature heat exchanger tank. The outlets of the first and second adsorption towers also simultaneously pass through a condenser and are connected to a liquid ammonia storage tank. Valves are provided at the inlet, outlet, heat exchanger inlet, and heat exchanger outlet to allow the first and second adsorption towers to operate the adsorption and desorption processes simultaneously.

[0007] Furthermore, it also includes a low-temperature heat exchanger tank, which stores the low-temperature heat exchanger, and its outlet and return outlet are connected to the heat exchanger inlet and outlet of the first adsorption tower and the second adsorption tower, respectively.

[0008] Furthermore, the heat exchanger is heat transfer oil; the oil temperature in the high-temperature heat exchanger tank is 150~300℃; and the oil temperature in the low-temperature heat exchanger tank is 30~50℃.

[0009] Furthermore, it also includes a second heat exchanger, the shell side of which is located on the inlet pipe of the reactor, and the tube side of which is located on the outlet pipe of the reactor after the first heat exchanger.

[0010] Furthermore, it also includes a compressor, which is installed on the pipeline between the outlet of the first adsorption tower and the second adsorption tower and the first heat exchanger.

[0011] Furthermore, it also includes a buffer tank, which is installed on the pipeline between the outlet of the first adsorption tower and the second adsorption tower and the condenser.

[0012] Furthermore, it also includes a cooler, which is located in front of the return port of the cryogenic heat exchanger tank.

[0013] Furthermore, a first oil pump and a second oil pump are respectively installed at the liquid outlet of the high-temperature heat exchanger tank and the liquid outlet of the low-temperature heat exchanger tank.

[0014] Furthermore, it also includes an electric heater, which is installed on the pipeline between the first heat exchanger and the heat exchanger inlets of the first and second adsorption towers.

[0015] Furthermore, it also includes a thermometer, which is installed at the outlet of the electric heater and electrically connected to the electric heater, so as to sense the temperature of the heat exchanger at the outlet of the electric heater and control the operating state of the electric heater.

[0016] The beneficial effects of this invention are: This invention features a reasonable design, simple structure, and convenient use. It utilizes the waste heat from the reactor outlet gas for adsorption operation, avoiding the increased overall energy consumption caused by introducing additional power consumption, thus greatly improving energy utilization efficiency and promoting energy conservation and environmental protection. Furthermore, it allows for rapid switching between adsorption and desorption between the two adsorption towers, maintaining stability within their respective operating cycles. This significantly enhances the overall thermal efficiency and operational controllability of the adsorption-enhanced ammonia synthesis process. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention.

[0018] Among them, 1-high temperature heat exchanger tank, 2-low temperature heat exchanger tank, 3-reactor, 4-first adsorption tower, 5-second adsorption tower, 6-second heat exchanger, 7-first oil pump, 8-second oil pump, 9-first heat exchanger, 10-1~10-12 first valve~twelfth valve, 11-electric heater, 12-cooler; 13-buffer tank; 14-condenser; 15-compressor. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] like Figure 1 As shown.

[0021] A thermal coupling device suitable for adsorption-enhanced ammonia synthesis includes a reactor 3, a first adsorption tower 4, a second adsorption tower 5, a high-temperature heat exchanger tank 1, a low-temperature heat exchanger tank 2, a first heat exchanger 9, a second heat exchanger 6, a buffer tank 13, a condenser 14, and a variable-temperature adsorption cycle switching valve group, etc.

[0022] The reactor 3 is an ammonia synthesis reactor, including an inlet and an outlet.

[0023] The first adsorption tower 4 and the second adsorption tower 5 have the same structure, both being internally heat-exchange tube-type towers, equipped with an inlet, an outlet, a heat exchanger inlet, and a heat exchanger outlet. Their shell sides are filled with ammonia adsorbent, and their tube sides flow with heat exchanger, enabling adsorption or desorption operation. Preferably, the tower bodies of the first and second adsorption towers are cylindrical, with parallel heat exchange tubes inside forming a shell-and-tube configuration. The outer shell side of the tubes is filled with ammonia adsorbent, and the heat exchanger flows through the tubes, exchanging heat with the adsorbent in the shell side. The ammonia adsorbent is preferably a metal halide composite adsorbent, such as magnesium chloride, calcium chloride, strontium chloride, copper chloride, manganese chloride, etc., as the active adsorbent, supported on alumina, silica, magnesium oxide, molecular sieves, zeolites, etc. The heat exchange tubes are preferably arranged in an equilateral triangular configuration. Alternatively, the tubes can be internally filled with adsorbent, with heat exchange occurring between the heat exchanger in the shell side and the adsorbent bed within the tubes.

[0024] The high-temperature heat exchanger storage tank 1 and the low-temperature heat exchanger storage tank 2 have the same structure, storing high-temperature heat transfer oil and low-temperature heat transfer oil respectively. They are equipped with an outlet and a return outlet, as well as a thermometer to monitor their internal temperature. Simultaneously, a first oil pump 7 and a second oil pump 8 are respectively installed at the outlets of the high-temperature heat exchanger storage tank 1 and the low-temperature heat exchanger storage tank 2 to ensure the normal flow of the heat exchanger. Preferably, the temperature of the high-temperature heat transfer oil in the high-temperature heat exchanger storage tank 1 is 150~300℃, and the temperature of the low-temperature heat transfer oil in the low-temperature heat exchanger storage tank 2 is 30~50℃. The first heat exchanger 9 and the second heat exchanger 6 are both shell-and-tube heat exchangers, which can realize gas-liquid heat exchange or gas-gas heat exchange.

[0025] The variable temperature adsorption cycle switching valve group includes multiple two-way valves that can be shut off and two three-way valves that can be switched.

[0026] The connection method of the thermal coupling system of this invention is as follows: The inlet of reactor 3 is connected to a hydrogen-nitrogen mixed gas source after passing through the shell side of the second heat exchanger 6, and its outlet is connected to the gas inlet of the first adsorption tower 4 and the second adsorption tower 5 after passing through the tube side of the first heat exchanger 9 and the tube side of the second heat exchanger 6 in sequence.

[0027] The outlets of the first adsorption tower 4 and the second adsorption tower 5 are simultaneously connected to an outlet pipeline. This outlet pipeline passes sequentially through the buffer tank 13 and the condenser 14 before connecting to the liquid ammonia storage tank, so as to condense the desorbed ammonia gas into liquid ammonia for collection.

[0028] The outlets of the first adsorption tower 4 and the second adsorption tower 5 are also connected to a circulation pipeline. This circulation pipeline is connected to the shell side of the second heat exchanger 6 after passing through the compressor 15, so that the adsorbed gas is mixed with the hydrogen-nitrogen mixture and then recirculated into the reaction loop, thereby improving the raw material utilization rate.

[0029] The outlet pipeline is equipped with a ninth valve 10-9 and a tenth valve 10-10. The circulation pipeline is equipped with an eleventh valve 10-11 and a twelfth valve 10-12. The ninth valve 10-9 and the eleventh valve 10-11 correspond to the outlet of the first adsorption tower 4. The tenth valve 10-10 and the twelfth valve 10-12 correspond to the outlet of the second adsorption tower 5. Thus, by controlling the opening and closing of the corresponding valves, the simultaneous adsorption and desorption of the first and second adsorption towers can be achieved.

[0030] The heat exchanger inlets of the first adsorption tower 4 and the second adsorption tower 5 are simultaneously connected to the liquid outlet of the high-temperature heat exchanger tank 1 via a first heat exchange pipeline, which passes through the shell side of the first heat exchanger 9. Thus, the high-temperature heat transfer oil from the high-temperature heat exchanger tank 1 can exchange heat with the waste heat of the outlet gas of the reactor 3, and this waste heat can be introduced into the first or second adsorption tower to heat the adsorbent bed. This not only ensures the smooth progress of the adsorption process but also eliminates the need for additional power consumption, achieving energy saving and environmental protection.

[0031] An electric heater 11 is also provided on the first heat exchange pipeline. This electric heater 11 is located downstream of the first heat exchanger 9 so that if the temperature of the high-temperature heat transfer oil after heat exchange does not meet the requirements, the electric heater can be turned on to heat the high-temperature heat transfer oil to meet the needs of subsequent adsorption operation. Preferably, a thermometer is provided at the outlet of the electric heater 11. This thermometer is electrically connected to the electric heater 11, can monitor the oil temperature in real time, and transmit the temperature signal to control the output power of the electric heater 11, ensuring that the oil temperature meets the usage requirements.

[0032] The heat exchanger inlets of the first adsorption tower 4 and the second adsorption tower 5 are also connected to the outlet of the low-temperature heat exchanger tank 2 through a second heat exchange pipeline, so that the low-temperature heat transfer oil can be input into the tube side of the first adsorption tower or the second adsorption tower. Through heat exchange with the adsorbent bed, a large amount of heat generated during the desorption process can be carried away in time to ensure the stability of the bed temperature.

[0033] The first heat exchange pipeline is equipped with a first valve 10-1 and a second valve 10-2, corresponding to the heat exchanger inlets of the first adsorption tower 4 and the second adsorption tower 5, respectively. Simultaneously, the second heat exchange pipeline is equipped with a third valve 10-3 and a fourth valve 10-4. The first valve 10-1 and the third valve 10-3 correspond to the heat exchanger inlet of the first adsorption tower 4. The second valve 10-2 and the fourth valve 10-4 correspond to the heat exchanger inlet of the second adsorption tower 5. Therefore, by controlling the opening and closing of the corresponding valves, the operational requirements for simultaneous adsorption and desorption in the first and second adsorption towers can be met.

[0034] The heat exchanger outlets of the first adsorption tower 4 and the second adsorption tower 5 are simultaneously connected to the return port of the high-temperature heat exchanger tank 1 through a third heat exchange pipeline, and the temperature of the high-temperature heat transfer oil in the high-temperature heat exchanger tank is preferably 220°C.

[0035] The heat exchanger outlets of the first adsorption tower 4 and the second adsorption tower 5 are also connected to the return port of the low-temperature heat exchanger tank 2 through a fourth heat exchange pipeline, and the temperature of the low-temperature heat transfer oil in the low-temperature heat exchanger tank is preferably 40°C.

[0036] The third and fourth heat exchange pipelines are connected by a seventh valve 10-7 and an eighth valve 10-8. Both the seventh valve 10-7 and the eighth valve 10-8 are convertible three-way valves, allowing for simultaneous adsorption and desorption operations of the two adsorption towers by switching directions. Preferably, the fourth heat exchange pipeline is equipped with a cooler 12 to ensure that the low-temperature heat transfer oil is fully cooled before being returned to the low-temperature heat exchanger tank.

[0037] The operation process of this invention is as follows: A hydrogen-nitrogen mixture of 24 kmol / h, at 40°C and 3 MPa, composed of 75% hydrogen and 25% nitrogen, is mixed with circulating gas from compressor 15 and serves as the reactant mixture. This mixture enters the tube side of the second heat exchanger 6, where it exchanges heat with the outlet gas from the tube side of the first heat exchanger 9, preheating it to 340°C. It then enters reactor 3 for ammonia synthesis. The reactor outlet temperature is 430°C, with an ammonia content of 5.5%. The reactor outlet gas first enters the tube side of the first heat exchanger 9 for heat exchange, then enters the shell side of the second heat exchanger 6, preheating the reactant mixture and reducing the reactor outlet gas temperature to approximately 77°C. It then enters the adsorption section.

[0038] In the adsorption section, continuous operation of temperature-switching adsorption is achieved by opening and closing the corresponding valves in the temperature-switching adsorption cycle switching valve group.

[0039] First, when the first adsorption tower 4 is in the desorption stage and the second adsorption tower 5 is in the adsorption stage, the specific opening and closing states of the variable temperature adsorption cycle switching valve group are as follows: the second valve 10-2, the third valve 10-3, the fifth valve 10-5, the tenth valve 10-10, and the eleventh valve 10-11 are closed; the first valve 10-1, the fourth valve 10-4, the sixth valve 10-6, the ninth valve 10-9, and the twelfth valve 10-12 are open. The flow direction of the seventh valve 10-7 is from the heat exchanger outlet of the first adsorption tower 4 to the high-temperature heat exchanger tank 1; the flow direction of the eighth valve 10-8 is from the heat exchanger outlet of the second adsorption tower 5 to the low-temperature heat exchanger tank 2.

[0040] After passing through the first and second heat exchangers, the reactor outlet gas then passes through the sixth valve 10-6 and enters the second adsorption tower 5 for gas adsorption. The second adsorption tower 5 is filled with ammonia adsorbent, which selectively adsorbs ammonia from the reactor outlet gas, reducing the ammonia content in the adsorbed gas to below 1%. The adsorbed gas then flows out of the outlet of the second adsorption tower 5, passes through valve 10-12, and flows into the compressor 15 to be pressurized to 3 MPa. After mixing with the hydrogen-nitrogen mixture, it re-enters the reaction loop for reuse.

[0041] During desorption, the temperature inside the adsorption bed is 150~300℃, preferably 220℃. At this time, driven by the high temperature, the adsorbed ammonia is released. Moreover, since no purge gas is provided, the purity of the desorbed ammonia is very high, with an average concentration >95%. Then, it enters the buffer tank 13 through the ninth valve 10-9 to stabilize the release flow rate. After being liquefied by the condenser 14, it becomes liquid ammonia and flows into the liquid ammonia storage tank for collection. During this period, the desorption temperature is maintained by the flow of high-temperature heat transfer oil in the first and third circulation pipelines. Specifically, the high-temperature heat transfer oil in the high-temperature heat exchanger tank 1 is 150~300℃, preferably 220℃. After being pumped out by the first oil pump 7, it passes through the shell side of the first heat exchanger, exchanges heat with the reactor outlet gas, and then passes through the electric heater 11 to supplement heat before entering the inner heat exchanger tubes of the first adsorption tower 4 through the heat exchanger inlet to fully heat the adsorption bed temperature. At this time, the thermometer monitors the oil temperature in the pipeline in real time and transmits the temperature signal to control the output power of the electric heater 11, ensuring that the oil temperature after flowing through the electric heater meets the requirements. After the high-temperature heat transfer oil flows out from the internal heat exchange tube of the first adsorption tower 4, it passes through the seventh valve 10-7 and returns to the high-temperature heat exchanger tank 1. In order to reduce heat loss, the first circulation pipeline, the third circulation pipeline, and the outer shell of the high-temperature heat exchanger tank 1 are all wrapped with heat insulation material.

[0042] The operating temperature of the second adsorption tower 5 is 30~50℃. Cooling is achieved through the second and fourth circulation pipelines to maintain the adsorption temperature. Specifically, the low-temperature heat transfer oil in the low-temperature heat exchanger tank 2 is at 30~50℃, preferably 40℃. It is pumped out by the second oil pump 8. Then, after passing through the fourth valve 10-4, it enters the internal heat exchange tubes of the second adsorption tower 5, where the adsorption heat is removed through heat exchange, while simultaneously maintaining a constant adsorption bed temperature. The total flow rate of the low-temperature heat transfer oil is 15 m³ / s. 3 / h, after flowing out of the internal heat exchange tube of the second adsorption tower 5, it enters the cooler 12 for cooling after passing through the eighth valve 10-8, and the temperature of the low temperature heat transfer oil is reduced back to 40℃ before flowing back to the low temperature heat exchanger tank 2.

[0043] When the effective heat transfer area of ​​the first heat exchanger reaches 2.5m² 2 At this time, the heat transferred from the reactor outlet gas to the heat transfer oil can cover the heat loss of the high-temperature heat transfer oil and the heat transferred to the adsorption bed, so that the temperature of the high-temperature heat transfer oil entering the adsorption tower is still higher than the set value. Therefore, the electric heater 11 basically does not need to be started after the variable temperature adsorption system reaches a stable cycle. It only needs to be started during process abnormalities or start-up and shutdown phases to supplement heat and bring the system to a stable state. The system's heat comes entirely from the waste heat of the reactor outlet gas, without the need for external energy supplementation.

[0044] After the above process lasts for 1800 seconds, the first adsorption tower 4 switches to the adsorption stage, and the second adsorption tower 5 switches to the desorption stage. At this time, the opening and closing states of the variable temperature adsorption cycle switching valve group automatically switch as follows: valves 10-2, 10-3, 10-5, 10-10, and 10-11 are open; valves 10-1, 10-4, 10-6, 10-9, and 10-12 are closed; the flow direction of valve 10-7 is switched to: from the heat exchanger outlet of the first adsorption tower 4 to the low-temperature heat exchanger tank 2; the flow direction of valve 10-8 is switched to: from the heat exchanger outlet of the second adsorption tower 5 to the high-temperature heat exchanger tank 1. After another 1800 seconds, the process switches back to the state of the previous step, and the cycle continues.

[0045] This invention features a reasonable design, simple structure, and convenient operation. It utilizes the waste heat from the reactor outlet gas for adsorption operation, avoiding the increased overall energy consumption caused by introducing additional power consumption, thus greatly improving energy utilization efficiency and promoting energy conservation and environmental protection. Simultaneously, it allows for rapid switching between adsorption and desorption between the two adsorption towers, maintaining stability within their respective operating cycles. This significantly enhances the overall thermal efficiency and operational controllability of the adsorption-enhanced ammonia synthesis process.

[0046] All parts not covered in this invention are the same as or can be implemented using existing technologies.

Claims

1. A thermally coupled device suitable for adsorption-enhanced ammonia synthesis, comprising a reactor, a first adsorption tower, and a second adsorption tower, characterized in that, The reactor inlet is connected to a hydrogen-nitrogen mixed gas source; the first and second adsorption towers have the same structure, with their outlets simultaneously connected to the reactor inlet, their inlets simultaneously connected to the reactor outlet after passing through the tube side of the first heat exchanger, their heat exchanger inlets simultaneously connected to the liquid outlet of the high-temperature heat exchanger tank after passing through the shell side of the first heat exchanger, and their heat exchanger outlet simultaneously connected to the liquid return port of the high-temperature heat exchanger tank; the outlets of the first and second adsorption towers are also simultaneously connected to the liquid ammonia storage tank after passing through a condenser; valves are respectively provided at the inlet, outlet, heat exchanger inlet, and heat exchanger outlet so that the first and second adsorption towers can operate the adsorption and desorption processes at the same time.

2. The thermal coupling device for adsorption-enhanced ammonia synthesis according to claim 1, characterized in that, It also includes a low-temperature heat exchanger tank, which stores the low-temperature heat exchanger, and its outlet and return outlet are connected to the heat exchanger inlet and outlet of the first adsorption tower and the second adsorption tower, respectively.

3. The thermal coupling device for adsorption-enhanced ammonia synthesis according to claim 1, characterized in that, The heat exchanger is heat transfer oil; the oil temperature in the high-temperature heat exchanger tank is 150~300℃; the oil temperature in the low-temperature heat exchanger tank is 30~50℃.

4. The thermal coupling device for adsorption-enhanced ammonia synthesis according to claim 1, characterized in that, It also includes a second heat exchanger, the shell side of which is located on the inlet pipe of the reactor, and the tube side of which is located on the outlet pipe of the reactor after the first heat exchanger.

5. The thermal coupling device for adsorption-enhanced ammonia synthesis according to claim 1, characterized in that, It also includes a compressor, which is installed on the pipeline between the outlet of the first adsorption tower and the second adsorption tower and the first heat exchanger.

6. The thermal coupling device for adsorption-enhanced ammonia synthesis according to claim 1, characterized in that, It also includes a buffer tank, which is installed on the pipeline between the outlet of the first adsorption tower and the second adsorption tower and the condenser.

7. The thermal coupling device for adsorption-enhanced ammonia synthesis according to claim 2, characterized in that, It also includes a cooler, which is located in front of the reflux port of the cryogenic heat exchanger tank.

8. The thermal coupling device for adsorption-enhanced ammonia synthesis according to claim 2, characterized in that, The outlet of the high-temperature heat exchanger tank and the outlet of the low-temperature heat exchanger tank are respectively equipped with a first oil pump and a second oil pump.

9. The thermal coupling device for adsorption-enhanced ammonia synthesis according to claim 1, characterized in that, It also includes an electric heater, which is installed on the pipeline between the first heat exchanger and the heat exchanger inlet of the first adsorption tower and the second adsorption tower.

10. The thermal coupling device for adsorption-enhanced ammonia synthesis according to claim 1, characterized in that, It also includes a thermometer, which is located at the outlet of the electric heater and electrically connected to the electric heater, so as to sense the temperature of the heat exchanger at the outlet of the electric heater and control the operating state of the electric heater.

Images