Waste heat refrigerating system suitable for dynamically synthesizing green ammonia

Abstract

The utility model relates to the technical field of energy conservation and emission reduction, in particular to a waste heat refrigerating system suitable for dynamically synthesizing green ammonia. A synthetic ammonia reaction system; a waste heat boiler; cooling the condenser system; a product recovery system; a waste heat refrigerating unit; and the connection relationship among the systems is limited. According to the waste heat refrigerating system suitable for dynamically synthesizing the green ammonia, the low-pressure steam waste heat refrigerating technology can be utilized, direct conversion between the cold end and the hot end is completed, coupling between fluctuating steam yield and fluctuating cold demand is achieved, and meanwhile the concept and the production principle of green hydrogen and green ammonia are met.

Description

Technical Field

[0001] The utility model relates to the technical field of energy conservation and emission reduction, in particular to a waste heat refrigeration system suitable for dynamically synthesizing green ammonia. Background Art

[0002] As one of the most widely produced and applied bulk chemicals in the world, ammonia is widely used in the fields of making nitric acid, chemical fertilizers, explosives, refrigerants, etc. Ammonia synthesis, as a typical exothermic reaction, requires continuous removal of reaction heat to maintain the optimal reaction temperature and ensure the activity of the catalyst. The typical ammonia synthesis process route includes four continuous processes of compression, preheating and reaction, waste heat recovery, and cooling and separation, as well as other auxiliary facilities. By setting a waste heat boiler at the outlet of the ammonia synthesis tower and producing steam through a steam drum, heat recovery can be achieved.

[0003] At present, renewable energy sources such as wind and light are developing rapidly, and the industrial application of electrolytic water hydrogen production technology is gradually being promoted. Limited by the timeliness of new energy sources such as wind and light, the power grid cannot digest and regulate a large amount of green electricity. Green ammonia synthesis relies on green hydrogen prepared from upstream new energy as raw materials. Limited by the timeliness of wind and photovoltaic power itself, the production load of raw material green hydrogen fluctuates. The fluctuation of the production load of raw material green hydrogen brings about the fluctuation of the green ammonia production load, and the by-product steam volume also fluctuates accordingly. At the same time, the liquefaction process of syngas requires an electric-driven ammonia ice machine to provide cooling capacity, and the cooling capacity required for cooling condensers (such as primary and secondary ammonia refrigeration) fluctuates.

[0004] Since the by-product steam volume of green ammonia is fluctuating, it needs to be consumed independently within the device boundary area. By-product steam can generally be used for waste heat power generation. The existing method is to use low-grade steam waste heat for power generation. According to research, the minimum operating load of waste heat utilization generator sets on the market must be greater than 30% of the rated load. When designing a generator set based on the steam production volume at 100% load of the ammonia synthesis device, when the load of the ammonia synthesis device drops below 30%, the generator set cannot meet the minimum load operation, and a steam accumulator needs to be added to ensure the normal operation of the generator set when the ammonia synthesis device is below 30% load during the low valley of new energy power generation. Designing the scale of the steam accumulator according to the power generation situation greatly increases the project investment and floor area. Content of the Utility Model

[0005] In view of this, the technical problem to be solved by the utility model is to provide a waste heat refrigeration system suitable for dynamically synthesizing green ammonia, which can utilize the low-pressure steam waste heat refrigeration technology to complete the direct conversion of the cold and hot ends, realize the coupling between the fluctuating steam output and the fluctuating cooling demand, and also conform to the concept and production principle of green hydrogen and green ammonia.

[0006] The utility model provides a waste heat refrigeration system suitable for dynamically synthesizing green ammonia, including:

[0007] Multi-stage cooler system;

[0008] An ammonia synthesis reaction system; the raw material compressed gas inlet of the ammonia synthesis reaction system is connected to the raw material compressed gas outlet of the multi-stage cooler system;

[0009] A waste heat boiler connected to the synthesis gas outlet of the ammonia synthesis reaction system; the synthesis gas inlet of the multi-stage cooler system is connected to the synthesis gas outlet of the waste heat boiler;

[0010] A cooling condenser system; the synthesis gas inlet of the cooling condenser system is connected to the synthesis gas outlet of the multi-stage cooler system;

[0011] A product recovery system; the synthesis gas inlet of the product recovery system is connected to the synthesis gas outlet of the cooling condenser system; the recycle gas outlet of the product recovery system is connected to the recycle gas inlet of the multi-stage cooler system;

[0012] A waste heat refrigeration unit; the low-pressure steam inlet of the waste heat refrigeration unit is connected to the low-pressure steam outlet of the waste heat boiler; the liquid ammonia outlet of the waste heat refrigeration unit is connected to the liquid ammonia inlet of the product recovery system; the gaseous ammonia inlet of the waste heat refrigeration unit is connected to the gaseous ammonia outlet of the cooling condenser system.

[0013] Preferably, the multi-stage cooler system includes a inlet and outlet heat exchanger, a water cooler and a cold exchanger connected in sequence;

[0014] The synthesis gas inlet of the water cooler is connected to the synthesis gas outlet of the inlet and outlet heat exchanger; the synthesis gas inlet of the cold exchanger is connected to the synthesis gas outlet of the water cooler; the recycle gas inlet of the cold exchanger is connected to the recycle gas outlet of the product recovery system.

[0015] Preferably, the ammonia synthesis reaction system includes an ammonia synthesis tower, a molten salt heater, a molten salt heat storage unit and an electric heater.

[0016] Preferably, the waste heat refrigeration system further includes: a waste heat boiler and a steam drum;

[0017] The synthesis gas inlet of the waste heat boiler is connected to the synthesis gas outlet of the ammonia synthesis tower; the synthesis gas inlet of the multi-stage cooler system is connected to the synthesis gas outlet of the waste heat boiler; the low-pressure steam outlet of the waste heat boiler is connected to the steam drum.

[0018] Preferably, the waste heat refrigeration system further includes a boiler feed water heater;

[0019] The syngas inlet of the boiler feedwater heater is connected to the syngas outlet of the waste heat boiler; the boiler feedwater outlet of the boiler feedwater heater is connected to the boiler feedwater inlet of the waste heat boiler; the syngas outlet of the boiler feedwater heater is connected to the syngas inlet of the inlet and outlet heat exchanger.

[0020] Preferably, the cooling and condensing system includes a first ammonia cooler and a second ammonia cooler connected in sequence;

[0021] The syngas inlet of the first ammonia cooler is connected to the syngas outlet of the cold exchanger, and the syngas inlet of the second ammonia cooler is connected to the syngas outlet of the first ammonia cooler.

[0022] Preferably, the product recovery system includes an ammonia separator and a cold recovery heat exchanger connected to the liquid ammonia outlet of the ammonia separator;

[0023] The syngas inlet of the ammonia separator is connected to the syngas outlet of the second ammonia cooler; the liquid ammonia inlet of the tube side of the cold recovery heat exchanger is connected to the liquid ammonia outlet of the ammonia separator, and the gas outlet of the ammonia separator is connected to the recycle gas inlet of the cold exchanger;

[0024] The liquid ammonia product discharged from the liquid ammonia outlet of the tube side of the cold recovery heat exchanger is sent to the product tank area.

[0025] Preferably, the waste heat refrigeration unit includes a first waste heat refrigeration unit and a second waste heat refrigeration unit;

[0026] The first waste heat refrigeration unit includes:

[0027] A first medium-pressure cylinder;

[0028] A first condenser; the ammonia vapor inlet of the first condenser is connected to the ammonia vapor outlet of the first medium-pressure cylinder; the liquid ammonia outlet pipeline of the first condenser is connected to the liquid ammonia inlet of the first ammonia cooler through the first shell side of the cold recovery heat exchanger;

[0029] A first low-pressure cylinder: the gaseous ammonia inlet of the first low-pressure cylinder is connected to the gaseous ammonia outlet of the first ammonia cooler;

[0030] A first rich and lean liquid heat exchanger; the rich liquid inlet of the first rich and lean liquid heat exchanger is connected to the rich liquid outlet of the first low-pressure cylinder, and the rich liquid outlet of the first rich and lean liquid heat exchanger is connected to the rich liquid inlet of the first medium-pressure cylinder; the lean liquid inlet of the first rich and lean liquid heat exchanger is connected to the lean liquid outlet of the first medium-pressure cylinder, and the lean liquid outlet of the first rich and lean liquid heat exchanger is connected to the lean liquid inlet of the first low-pressure cylinder;

[0031] The second waste heat refrigeration unit includes:

[0032] Second medium-pressure cylinder;

[0033] Second condenser; the ammonia vapor inlet of the second condenser is connected to the ammonia vapor outlet of the second medium-pressure cylinder; the liquid ammonia outlet pipe of the second condenser is connected to the liquid ammonia inlet of the second ammonia cooler through the second shell pass of the cold recovery heat exchanger;

[0034] Second low-pressure cylinder: the gaseous ammonia inlet of the second low-pressure cylinder is connected to the gaseous ammonia outlet of the second ammonia cooler;

[0035] Second rich and lean liquid heat exchanger; the rich liquid inlet of the second rich and lean liquid heat exchanger is connected to the rich liquid outlet of the second low-pressure cylinder, and the rich liquid outlet of the second rich and lean liquid heat exchanger is connected to the rich liquid inlet of the second medium-pressure cylinder; the lean liquid inlet of the second rich and lean liquid heat exchanger is connected to the lean liquid outlet of the second medium-pressure cylinder, and the lean liquid outlet of the second rich and lean liquid heat exchanger is connected to the lean liquid inlet of the second low-pressure cylinder.

[0036] Preferably, a first solution pump is provided on the pipeline between the first low-pressure cylinder and the first rich and lean liquid heat exchanger.

[0037] Preferably, a second solution pump is provided on the pipeline between the second low-pressure cylinder and the second rich and lean liquid heat exchanger.

[0038] The waste heat refrigeration system for adapting to dynamic synthesis of green ammonia provided by the present utility model can utilize the low-pressure steam waste heat refrigeration technology to complete the direct conversion between the cold and hot ends, realize the coupling between the fluctuating steam output and the fluctuating cooling demand, and also conform to the concept and production principle of green hydrogen and green ammonia. Brief Description of the Drawings

[0039] Figure 1 It is a simplified process flow diagram of the waste heat refrigeration for adapting to dynamic synthesis of green ammonia provided by an embodiment of the present application;

[0040] Figure 2 It is a process flow diagram of the waste heat refrigeration for adapting to dynamic synthesis of green ammonia provided by another embodiment of the present application; wherein, 1 is an inlet and outlet heat exchanger, 2 is a molten salt heater, 3 is a molten salt heat storage unit, 4 is an electric heater, 5 is an ammonia synthesis tower, 6 is a waste heat boiler, 7 is a steam drum, 8 is a water cooler, 9 is a cold exchanger, 10 is a first ammonia cooler, 11 is a second ammonia cooler, 12 is an ammonia separator, 13 is a cold recovery heat exchanger, 14 is a waste heat refrigeration unit, 15 is a boiler feed water heater; 16 is a flow control valve, 17 is a startup control valve, 18 is a hot standby control valve, 19 is a steam pressure regulating valve, 20 is a first ammonia cooling pressure reducing valve, 21 is a second ammonia cooling pressure reducing valve;

[0041] Figure 3 It is a system diagram of the first waste heat refrigeration unit provided by an embodiment of the present application;

[0042] Figure 4 System diagram of the second waste heat refrigeration unit provided for an embodiment of the present application;

[0043] Figure 5 Graph showing the relationship between the by - product low - pressure steam volume as the heat source and the ammonia synthesis production load in Embodiment 1 of the present application;

[0044] Figure 6 Graph showing the relationship between the cooling capacity required for the first ammonia cooler of the present application and the ammonia synthesis production load;

[0045] Figure 7 Graph showing the relationship between the cooling capacity required for the second ammonia cooler of the present application and the ammonia synthesis production load. Detailed implementation manners

[0046] Next, in combination with the embodiments of the present utility model, the technical solutions of the present utility model will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments in the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0047] The present utility model provides a waste heat refrigeration system adapted to dynamic synthesis of green ammonia, including:

[0048] A multi - stage cooler system, the multi - stage cooler system is provided with a raw material compressed gas inlet, a raw material compressed gas outlet, a synthesis gas inlet, a synthesis gas outlet, a recycle gas inlet and a recycle gas outlet;

[0049] An ammonia synthesis reaction system, the raw material compressed gas inlet of the ammonia synthesis reaction system is connected to the raw material compressed gas outlet of the multi - stage cooler system;

[0050] A waste heat boiler connected to the synthesis gas outlet of the ammonia synthesis reaction system; the waste heat boiler is provided with a synthesis gas inlet, a synthesis gas outlet, a low - pressure steam outlet, a boiler feed water inlet and a boiler blowdown water outlet; the synthesis gas inlet of the multi - stage cooler system is connected to the synthesis gas outlet of the waste heat boiler;

[0051] A cooling and condensing system, the cooling and condensing system is provided with a synthesis gas inlet, a synthesis gas outlet, a liquid ammonia inlet and a gaseous ammonia outlet; the synthesis gas inlet of the cooling and condensing system is connected to the synthesis gas outlet of the multi - stage cooler system;

[0052] A product recovery system, the product recovery system is provided with a synthesis gas inlet, a recycle gas outlet, a tube - side liquid ammonia outlet; the synthesis gas inlet of the product recovery system is connected to the synthesis gas outlet of the cooling and condensing system; the recycle gas outlet of the product recovery system is connected to the recycle gas inlet of the multi - stage cooler system;

[0053] Waste heat refrigeration unit; the waste heat refrigeration unit is provided with a low-pressure steam inlet, a liquid ammonia outlet and a gaseous ammonia inlet; the low-pressure steam inlet of the waste heat refrigeration unit is connected to the low-pressure steam outlet of the waste heat boiler; the liquid ammonia outlet of the waste heat refrigeration unit is connected to the liquid ammonia inlet of the product recovery system; the gaseous ammonia inlet of the waste heat refrigeration unit is connected to the gaseous ammonia outlet of the cooling and condenser system.

[0054] Figure 1 It is a simplified process flow diagram of waste heat refrigeration adapted to dynamic synthesis of green ammonia provided by an embodiment of the present invention.

[0055] Figure 2 It is a process flow chart of waste heat refrigeration adapted to dynamic synthesis of green ammonia provided by another embodiment of the present invention.

[0056] In some embodiments of the present invention, the multi-stage cooler system includes an inlet and outlet heat exchanger 1, a water cooler 8 and a cold exchanger 9 connected in sequence; the inlet and outlet heat exchanger 1 is provided with a raw material compressed gas inlet, a raw material compressed gas outlet, a synthesis gas inlet and a synthesis gas outlet. The synthesis gas inlet of the water cooler 8 is connected to the synthesis gas outlet of the inlet and outlet heat exchanger 1. The synthesis gas inlet of the cold exchanger 9 is connected to the synthesis gas outlet of the water cooler 8; the recycle gas inlet of the cold exchanger 9 is connected to the recycle gas outlet of the product recovery system. The inlet and outlet heat exchanger is a generally commercially available heat exchanger, the water cooler is a generally commercially available water cooler, and the cold exchanger is a generally commercially available cold exchanger.

[0057] In some embodiments of the present invention, the ammonia synthesis reaction system includes an ammonia synthesis tower 5, a molten salt heater 2, a molten salt heat storage unit 3 and an electric heater 4. The present invention has no special restrictions on the setting methods of the ammonia synthesis tower 5, the molten salt heater 2, the molten salt heat storage unit 3 and the electric heater 4. The molten salt heater is used to quickly supply heat to the ammonia synthesis tower 5 under low-load conditions; the molten salt heat storage unit 3 provides heat for the ammonia synthesis tower 5; the electric heater 4 is used to heat the raw material compressed gas entering the ammonia synthesis tower 5. The molten salt heat storage unit is a safe, energy-efficient and high-temperature heat energy-providing device quickly. It adopts a low-temperature binary molten salt mixture of potassium nitrate and sodium nitrite, with a molten salt melting temperature of 152°C, an operating temperature between 390 and 420°C, and a designed maximum heat load of 3500KW, providing heat for the ammonia synthesis reaction system. The ammonia synthesis tower is a generally commercially available ammonia synthesis tower, the molten salt heater is a generally commercially available molten salt heater, the molten salt heat storage unit is a generally commercially available molten salt heating skid, and the electric heater is a generally commercially available electric heater.

[0058] The present utility model further includes a waste heat boiler 6 connected to the synthesis gas outlet of the ammonia synthesis reaction system. The waste heat boiler 6 is provided with a synthesis gas inlet, a synthesis gas outlet, a low-pressure steam outlet, a boiler feed water inlet, and a boiler blowdown outlet; the synthesis gas inlet of the waste heat boiler 6 is connected to the synthesis gas outlet of the ammonia synthesis tower 5; the synthesis gas inlet of the multi-stage cooler system is connected to the synthesis gas outlet of the waste heat boiler 6. The low-pressure steam outlet of the waste heat boiler 6 is connected to a steam drum 7. The waste heat boiler is a generally commercially available waste heat boiler, and the steam drum is a generally commercially available steam drum.

[0059] In some embodiments of the present utility model, the waste heat refrigeration system further includes a boiler feed water heater 15. The boiler feed water heater 15 is provided with a boiler feed water inlet, a boiler feed water outlet, a synthesis gas inlet, and a synthesis gas outlet. The synthesis gas inlet of the boiler feed water heater 15 is connected to the synthesis gas outlet of the waste heat boiler 6, and the boiler feed water outlet of the boiler feed water heater 15 is connected to the boiler feed water inlet of the waste heat boiler 6; the synthesis gas outlet of the boiler feed water heater 15 is connected to the synthesis gas inlet of the inlet and outlet heat exchanger 1. The boiler feed water heater is a generally commercially available boiler feed water heater.

[0060] In some embodiments of the present utility model, the cooling and condensing system includes a first ammonia cooler 10 and a second ammonia cooler 11 connected in sequence. The synthesis gas inlet of the first ammonia cooler 10 is connected to the synthesis gas outlet of the cold exchanger 9, and the synthesis gas inlet of the second ammonia cooler 11 is connected to the synthesis gas outlet of the first ammonia cooler 10. The first ammonia cooler and the second ammonia cooler are generally commercially available ammonia coolers.

[0061] In some embodiments of the present utility model, the product recovery system includes an ammonia separator 12 and a cold recovery heat exchanger 13 connected to the liquid ammonia outlet of the ammonia separator 12. The synthesis gas inlet of the ammonia separator 12 is connected to the synthesis gas outlet of the second ammonia cooler 11; the liquid ammonia inlet of the tube side of the cold recovery heat exchanger 13 is connected to the liquid ammonia outlet of the ammonia separator 12. The gas outlet of the ammonia separator 12 is connected to the recycle gas inlet of the cold exchanger 9. The cold exchanger 9 is further provided with a recycle gas outlet. The ammonia separator is a generally commercially available ammonia separator, and the cold recovery heat exchanger is a generally commercially available cold recovery heat exchanger.

[0062] The liquid ammonia product discharged from the liquid ammonia outlet of the tube side of the cold recovery heat exchanger 13 is sent to the product tank area.

[0063] The waste heat refrigeration unit is a generally commercially available waste heat refrigeration unit.

[0064] In some embodiments of the present utility model, the number of the waste heat refrigeration units 14 matches the cooling capacity requirement of the cooling condenser system. In some specific embodiments, two waste heat refrigeration units 14 are provided, including a first waste heat refrigeration unit and a second waste heat refrigeration unit.

[0065] Regarding the first waste heat refrigeration unit, it includes:

[0066] A first medium-pressure cylinder, which is provided with a low-pressure steam inlet, an ammonia vapor outlet, a condensate outlet, a lean liquid outlet, and a rich liquid inlet;

[0067] A first condenser, which is provided with an ammonia vapor inlet and a liquid ammonia outlet; the ammonia vapor inlet of the first condenser is connected to the ammonia vapor outlet of the first medium-pressure cylinder; the liquid ammonia outlet pipeline of the first condenser is connected to the liquid ammonia inlet of the first ammonia cooler through the first shell pass of the cold recovery heat exchanger;

[0068] A first low-pressure cylinder, which is provided with a gaseous ammonia inlet, a lean liquid inlet, and a rich liquid outlet; the gaseous ammonia inlet of the first low-pressure cylinder is connected to the gaseous ammonia outlet of the first ammonia cooler;

[0069] A first rich-lean liquid heat exchanger (first GAX), which is provided with a rich liquid inlet, a rich liquid outlet, a lean liquid inlet, and a lean liquid outlet; the rich liquid inlet of the first rich-lean liquid heat exchanger is connected to the rich liquid outlet of the first low-pressure cylinder, and the rich liquid outlet of the first rich-lean liquid heat exchanger is connected to the rich liquid inlet of the first medium-pressure cylinder; the lean liquid inlet of the first rich-lean liquid heat exchanger is connected to the lean liquid outlet of the first medium-pressure cylinder, and the lean liquid outlet of the first rich-lean liquid heat exchanger is connected to the lean liquid inlet of the first low-pressure cylinder.

[0070] Figure 3 The system diagram of the first waste heat refrigeration unit provided for an embodiment of the present utility model. The structure of the second waste heat refrigeration unit is the same as that of the first waste heat refrigeration unit, except for the difference in the pipeline routing. Specifically, the second waste heat refrigeration unit includes:

[0071] A second medium-pressure cylinder, which is provided with a low-pressure steam inlet, an ammonia vapor outlet, a condensate outlet, a lean liquid outlet, and a rich liquid inlet;

[0072] A second condenser, which is provided with an ammonia vapor inlet and a liquid ammonia outlet; the ammonia vapor inlet of the second condenser is connected to the ammonia vapor outlet of the second medium-pressure cylinder; the liquid ammonia outlet pipeline of the second condenser is connected to the liquid ammonia inlet of the second ammonia cooler through the second shell pass of the cold recovery heat exchanger;

[0073] The second low-pressure cylinder is provided with an ammonia vapor inlet, a lean liquid inlet, and a rich liquid outlet; the ammonia vapor inlet of the second low-pressure cylinder is connected to the ammonia vapor outlet of the second ammonia cooler;

[0074] The second rich-lean liquid heat exchanger (the second GAX) is provided with a rich liquid inlet, a rich liquid outlet, a lean liquid inlet, and a lean liquid outlet; the rich liquid inlet of the second rich-lean liquid heat exchanger is connected to the rich liquid outlet of the second low-pressure cylinder, and the rich liquid outlet of the second rich-lean liquid heat exchanger is connected to the rich liquid inlet of the second medium-pressure cylinder; the lean liquid inlet of the second rich-lean liquid heat exchanger is connected to the lean liquid outlet of the second medium-pressure cylinder, and the lean liquid outlet of the second rich-lean liquid heat exchanger is connected to the lean liquid inlet of the second low-pressure cylinder.

[0075] In some embodiments of the present invention, two paths are provided on the pipeline of the low-pressure steam outlet of the steam drum 7. The first path is connected to the low-pressure steam inlet of the first medium-pressure cylinder, and the second path is connected to the low-pressure steam inlet of the second medium-pressure cylinder. The distribution of the low-pressure steam is determined according to the cooling loads required by the first ammonia cooler 10 and the second ammonia cooler 11.

[0076] In the present invention, low-pressure steam enters the medium-pressure cylinder to heat the TC multi-component working fluid in the medium-pressure cylinder (the commercially available medium-pressure cylinders are all filled with TC multi-component working fluid for heat transfer, and the present application has no special restrictions on the components of the TC multi-component working fluid), so that most of the low-boiling-point ammonia in the solution evaporates. The gaseous ammonia steam enters the condenser and is cooled by the circulating cooling water into saturated liquid ammonia.

[0077] The ammonia vapor outlet of the first ammonia cooler 10 is connected to the ammonia vapor inlet of the first low-pressure cylinder of the waste heat refrigeration unit, and the ammonia vapor outlet of the second ammonia cooler 11 is connected to the ammonia vapor inlet of the second low-pressure cylinder of the waste heat refrigeration unit.

[0078] The saturated liquid ammonia is sent out of the waste heat refrigeration boundary area, decompressed by a pressure reducing valve, and becomes low-temperature liquid ammonia and enters the cold recovery heat exchanger 13. After heat exchange and temperature reduction, it enters the first ammonia cooler 10 and the second ammonia cooler 11. The low-temperature liquid ammonia absorbs heat and evaporates into low-temperature ammonia vapor in the first ammonia cooler 10 and the second ammonia cooler 11, and is sent into the waste heat refrigeration boundary area and enters the low-pressure cylinder. The lean liquid in the low-pressure cylinder absorbs ammonia vapor, and the concentration increases to form a rich solution. The lean liquid remaining after partial ammonia evaporation in the medium-pressure cylinder enters the rich-lean liquid heat exchanger (GAX) to exchange heat with the rich solution in the low-pressure cylinder, and then throttles and depressurizes and enters the low-pressure cylinder to absorb the evaporated low-temperature ammonia vapor and restore the solution to the original concentration. The lean solution forms a rich solution due to the absorption of liquid ammonia, and after being boosted by the solution pump, it enters the rich-lean liquid heat exchanger to exchange heat with the lean solution, and then is sent into the medium-pressure cylinder to continue circulating.

[0079] In some embodiments of the present utility model, a first solution pump is provided on the pipeline between the first low-pressure cylinder and the first rich-lean liquid heat exchanger, for conveying the rich liquid in the first low-pressure cylinder to the first rich-lean liquid heat exchanger.

[0080] In some embodiments of the present utility model, a second solution pump is provided on the pipeline between the second low-pressure cylinder and the second rich-lean liquid heat exchanger, for conveying the rich liquid in the second low-pressure cylinder to the second rich-lean liquid heat exchanger.

[0081] In some embodiments of the present utility model, the condensate discharged from the condensate outlet of the first medium-pressure cylinder and the condensate discharged from the condensate outlet of the second medium-pressure cylinder can be cooled and sent to the desalinated water station as make-up water.

[0082] In the present utility model, the waste heat refrigeration system described above is adopted to implement a waste heat refrigeration method suitable for dynamic synthesis of green ammonia, including the following steps:

[0083] S1) Heat-exchange the raw material compressed gas with the synthesis gas after ammonia synthesis reaction in a multi-stage cooler system to achieve preheating;

[0084] S2) Carry out ammonia synthesis reaction on the preheated raw material compressed gas in an ammonia synthesis reaction system to obtain synthesis gas; the synthesis gas recovers reaction heat through a waste heat boiler and by-produces low-pressure steam;

[0085] S3) Cool down the synthesis gas processed in step S2) successively through a multi-stage cooler system and a cooling condenser system to liquefy ammonia, and separate liquid ammonia in a product recovery system;

[0086] The waste heat refrigeration unit dynamically matches the cooling capacity required by the cooling condenser system by using the low-pressure steam.

[0087] Step S1):

[0088] Heat-exchange the raw material compressed gas with the synthesis gas after ammonia synthesis reaction in a multi-stage cooler system to achieve preheating.

[0089] In certain embodiments of the present utility model, the pressure of the raw material compressed gas is 13 to 16 MPaG, such as 14.5 MPaG. The raw material compressed gas is obtained by compressing the raw material gas with a syngas compressor. The intake of the syngas compressor is mainly divided into two streams. One stream is fresh raw material gas (i.e., gas that has not been used and directly comes out of the gas storage tank, with a volume ratio of N2 to H2 of 1:3), and the intake pressure is 1.3 to 1.5 MPaG. The other stream is the recycle gas returned from the synthesis loop (i.e., the recycle gas discharged from the cold exchanger 9). The fresh gas compressor and the recycle gas compressor are separately arranged. The fresh gas compressor pressurizes the fresh raw material gas from 1.3 to 1.5 MPaG to the pressure required for ammonia synthesis reaction (for example, 13 to 14 MPaG, specifically 13.5 MPaG); the recycle gas compressor is used to compress the recycle gas. This application has no special restrictions on the types and sources of the fresh gas compressor and the recycle gas compressor, and they can be general commercially available gas compressors.

[0090] In certain embodiments of the present utility model, the multi-stage cooler system includes an inlet and outlet heat exchanger, a water cooler, and a cold exchanger connected in sequence. The raw material compressed gas is heat-exchanged with the syngas after ammonia synthesis reaction in the inlet and outlet heat exchanger to achieve preheating. The temperature of the preheated raw material compressed gas is 140 to 150 °C, such as 145 °C.

[0091] Step S2):

[0092] Perform ammonia synthesis reaction on the preheated raw material compressed gas in the ammonia synthesis reaction system to obtain syngas; the syngas recovers reaction heat through a waste heat boiler and by-produces low-pressure steam.

[0093] In certain embodiments of the present utility model, the ammonia synthesis reaction system includes an ammonia synthesis tower. The preheated raw material compressed gas undergoes ammonia synthesis reaction in the ammonia synthesis tower.

[0094] In certain embodiments of the present utility model, the ammonia synthesis reaction system further includes: a molten salt heater, a molten salt heat storage unit, and an electric heater. The molten salt heater is used to quickly supply heat to the ammonia synthesis tower under low-load conditions to ensure the heat balance of the catalyst bed layer in the ammonia synthesis tower. The molten salt heat storage unit is a safe, energy-efficient and high-energy-saving device that can quickly provide high-temperature heat energy. It uses a low-temperature binary molten salt mixture of potassium nitrate and sodium nitrite, with a molten salt melting temperature of 152 °C, an operating temperature between 390 and 420 °C, and a designed maximum heat load of 3500 KW, and provides heat for the ammonia synthesis reaction system. The electric heater is used to heat the raw material compressed gas entering the ammonia synthesis tower. The temperature of the heated raw material compressed gas is 350 to 500 °C (which is also the temperature of the ammonia synthesis reaction). The catalyst in the ammonia synthesis tower is an iron-based catalyst, such as Amomax-10 (oxidized catalyst) or Amomax-10H (pre-reduced catalyst).

[0095] The recovery of reaction heat from the syngas by the waste heat boiler specifically includes: the syngas is transported to the waste heat boiler to provide waste heat for the waste heat boiler, and low-pressure steam is by-produced in the waste heat boiler. The pressure regulation range of the low-pressure steam is 0.3 - 2.5 MPaG, such as 1 MPaG; the temperature of the low-pressure steam is 143.6 - 226 °C, such as 159 °C. The low-pressure steam enters the steam drum connected to the waste heat boiler.

[0096] In some embodiments of the present invention, after the reaction heat of the syngas is recovered by the waste heat boiler, it is cooled by the boiler feed water heater to obtain the cooled syngas, and the temperature is 160 - 170 °C, such as 165 °C. After the boiler feed water is preheated by the boiler feed water heater, it enters the waste heat boiler. The waste heat boiler is also provided with a boiler blowdown outlet for discharging boiler sewage.

[0097] Step S3):

[0098] The syngas processed in step S2) is sequentially cooled by a multi-stage cooler system and a cooling condenser system to liquefy ammonia, and liquid ammonia is separated in the product recovery system;

[0099] The waste heat refrigeration unit utilizes the low-pressure steam to dynamically match the cooling capacity required by the cooling condenser system.

[0100] In some embodiments of the present invention, the cooling of the syngas processed in step S2) by the multi-stage cooler system includes: the syngas processed in step S2) is sequentially cooled by an inlet and outlet heat exchanger, a water cooler and a cold exchanger. The temperature of the syngas after being cooled by the inlet and outlet heat exchanger is 70 - 80 °C, such as 76 °C. The temperature of the syngas after being cooled by the water cooler is 37 - 43 °C, such as 40 °C. The syngas after being cooled by the water cooler exchanges heat with the cold air in its shell side in the cold exchanger, and the temperature of the syngas after being cooled by the cold exchanger is 28 - 33 °C, such as 31 °C.

[0101] In some embodiments of the present invention, the cooling condenser system includes a first ammonia cooler and a second ammonia cooler connected in sequence. The syngas after being cooled by the cold exchanger is cooled to 10 - 14 °C, such as 12 °C, by the first ammonia cooler; and is cooled to -10 - -6 °C, such as -8 °C, by the second ammonia cooler; to liquefy ammonia, and liquid ammonia is separated in the product recovery system.

[0102] In some embodiments of the present invention, the product recovery system includes an ammonia separator for separating liquid ammonia. Specifically, the syngas after being cooled by the second ammonia cooler enters the ammonia separator to separate liquid ammonia.

[0103] The gas separated by the ammonia separator enters the shell side of the multi-stage cooler system (cold exchanger) to recover the cooling capacity, and then enters the recycle section of the syngas compressor (i.e., recycle gas) for the next cycle.

[0104] The liquid ammonia separated by the ammonia separator is depressurized to 1.4 - 1.8 MPaG, such as 1.6 MPaG. The flash gas (high-temperature and high-pressure gas, when the pressure drops rapidly, the flashed gas is the flash gas) goes to the low-pressure section of the fresh gas compressor for reuse.

[0105] In some embodiments of the present invention, the product recovery system further includes a cold recovery heat exchanger connected to the liquid ammonia outlet of the ammonia separator. The liquid ammonia separated by the ammonia separator is preheated to 0 - 3 °C, such as 0 °C, by the cold recovery heat exchanger and then sent to the product tank area.

[0106] In the present invention, the waste heat refrigeration unit dynamically matches the cooling capacity required by the cooling condenser system using the low-pressure steam.

[0107] The waste heat refrigeration unit is provided with a low-pressure steam inlet, which is connected to the low-pressure steam outlet of the steam drum. The low-pressure steam provides the heat source required for liquid ammonia evaporation in the waste heat refrigeration unit.

[0108] The liquid ammonia discharged from the waste heat refrigeration unit recovers the cooling capacity in the cold recovery heat exchanger, and then is transported to the first ammonia cooler and the second ammonia cooler for heat exchange and vaporization. The gaseous ammonia enters the waste heat refrigeration unit for recycling.

[0109] In order to further illustrate the present invention, the following takes an embodiment to describe in detail a waste heat refrigeration system for adapting to dynamic synthesis of green ammonia provided by the present invention, but it should not be understood as a limitation to the protection scope of the present invention.

[0110] Embodiment 1

[0111] Adopt the waste heat refrigeration system as Figure 2 shown, including:

[0112] A multi-stage cooler system;

[0113] The multi-stage cooler system includes an inlet and outlet heat exchanger 1, a water cooler 8, and a cold exchanger 9 connected in sequence; the synthesis gas inlet of the water cooler 8 is connected to the synthesis gas outlet of the inlet and outlet heat exchanger 1; the synthesis gas inlet of the cold exchanger 9 is connected to the synthesis gas outlet of the water cooler 8; the recycle gas inlet of the cold exchanger 9 is connected to the recycle gas outlet of the product recovery system.

[0114] A synthetic ammonia reaction system;

[0115] The ammonia synthesis reaction system includes an ammonia synthesis tower 5, a molten salt heater 2, a molten salt heat storage unit 3 (i.e., a molten salt heating skid), and an electric heater 4; the molten salt heater is used to quickly supply heat to the ammonia synthesis tower 5 under low-load conditions; the electric heater 4 is used to heat the raw material compressed gas entering the ammonia synthesis tower 5; the molten salt heat storage unit 3 provides heat for the ammonia synthesis tower 5.

[0116] Waste heat boiler 6;

[0117] The syngas inlet of the waste heat boiler 6 is connected to the syngas outlet of the ammonia synthesis tower 5; the low-pressure steam outlet of the waste heat boiler 6 is connected to the steam drum 7.

[0118] Boiler feed water heater 15;

[0119] The syngas inlet of the boiler feed water heater 15 is connected to the syngas outlet of the waste heat boiler 6, the boiler feed water outlet of the boiler feed water heater 15 is connected to the boiler feed water inlet of the waste heat boiler 6; the syngas outlet of the boiler feed water heater 15 is connected to the syngas inlet of the inlet and outlet heat exchanger 1.

[0120] Cooling and condensing system;

[0121] The cooling and condensing system includes a first ammonia cooler 10 and a second ammonia cooler 11 connected in sequence; the syngas inlet of the first ammonia cooler 10 is connected to the syngas outlet of the cold exchanger 9, and the syngas inlet of the second ammonia cooler 11 is connected to the syngas outlet of the first ammonia cooler 10.

[0122] Product recovery system;

[0123] The product recovery system includes an ammonia separator 12 and a cold recovery heat exchanger 13 connected to the liquid ammonia outlet of the ammonia separator 12; the syngas inlet of the ammonia separator 12 is connected to the syngas outlet of the second ammonia cooler 11; the liquid ammonia inlet of the tube side of the cold recovery heat exchanger 13 is connected to the liquid ammonia outlet of the ammonia separator 12; the gas outlet of the ammonia separator 12 is connected to the recycle gas inlet of the cold exchanger 9.

[0124] The liquid ammonia discharged from the liquid ammonia outlet of the tube side of the cold recovery heat exchanger 13 is sent to the product tank area.

[0125] Two waste heat refrigeration units 14 are provided, including a first waste heat refrigeration unit and a second waste heat refrigeration unit.

[0126] Regarding the first waste heat refrigeration unit (as Figure 3 shown), it includes:

[0127] A first medium-pressure cylinder, the first medium-pressure cylinder is provided with a low-pressure steam inlet, an ammonia steam outlet, a condensate outlet, a lean liquid outlet, and a rich liquid inlet;

[0128] A first condenser, the first condenser is provided with an ammonia vapor inlet and a liquid ammonia outlet; the ammonia vapor inlet of the first condenser is connected to the ammonia vapor outlet of the first intermediate pressure cylinder; the liquid ammonia outlet pipeline of the first condenser is connected to the liquid ammonia inlet of the first ammonia cooler through the first shell pass of the cold recovery heat exchanger.

[0129] A first low-pressure cylinder, the first low-pressure cylinder is provided with a gaseous ammonia inlet, a lean liquid inlet, and a rich liquid outlet; the gaseous ammonia inlet of the first low-pressure cylinder is connected to the gaseous ammonia outlet of the first ammonia cooler 10.

[0130] A first rich-lean liquid heat exchanger (first GAX), the first rich-lean liquid heat exchanger is provided with a rich liquid inlet, a rich liquid outlet, a lean liquid inlet, and a lean liquid outlet; the rich liquid inlet of the first rich-lean liquid heat exchanger is connected to the rich liquid outlet of the first low-pressure cylinder, and the rich liquid outlet of the first rich-lean liquid heat exchanger is connected to the rich liquid inlet of the first intermediate pressure cylinder; the lean liquid inlet of the first rich-lean liquid heat exchanger is connected to the lean liquid outlet of the first intermediate pressure cylinder, and the lean liquid outlet of the first rich-lean liquid heat exchanger is connected to the lean liquid inlet of the first low-pressure cylinder.

[0131] The second waste heat refrigeration unit (as Figure 4 shown) includes:

[0132] A second intermediate pressure cylinder, the second intermediate pressure cylinder is provided with a low-pressure steam inlet, an ammonia vapor outlet, a condensate outlet, a lean liquid outlet, and a rich liquid inlet.

[0133] A second condenser, the second condenser is provided with an ammonia vapor inlet and a liquid ammonia outlet; the ammonia vapor inlet of the second condenser is connected to the ammonia vapor outlet of the second intermediate pressure cylinder; the liquid ammonia outlet pipeline of the second condenser is connected to the liquid ammonia inlet of the second ammonia cooler through the second shell pass of the cold recovery heat exchanger.

[0134] A second low-pressure cylinder, the second low-pressure cylinder is provided with a gaseous ammonia inlet, a lean liquid inlet, and a rich liquid outlet; the liquid ammonia inlet of the second low-pressure cylinder is connected to the gaseous ammonia outlet of the second ammonia cooler 11.

[0135] A second rich-lean liquid heat exchanger (second GAX), the second rich-lean liquid heat exchanger is provided with a rich liquid inlet, a rich liquid outlet, a lean liquid inlet, and a lean liquid outlet; the rich liquid inlet of the second rich-lean liquid heat exchanger is connected to the rich liquid outlet of the second low-pressure cylinder, and the rich liquid outlet of the second rich-lean liquid heat exchanger is connected to the rich liquid inlet of the second intermediate pressure cylinder; the lean liquid inlet of the second rich-lean liquid heat exchanger is connected to the lean liquid outlet of the second intermediate pressure cylinder, and the lean liquid outlet of the second rich-lean liquid heat exchanger is connected to the lean liquid inlet of the second low-pressure cylinder.

[0136] A first solution pump is provided on the pipeline between the first low-pressure cylinder and the first rich / lean liquid heat exchanger for transporting the rich liquid in the first low-pressure cylinder to the first rich / lean liquid heat exchanger.

[0137] A second solution pump is provided on the pipeline between the second low-pressure cylinder and the second rich / lean liquid heat exchanger for transporting the rich liquid in the second low-pressure cylinder to the second rich / lean liquid heat exchanger.

[0138] Two pipelines are provided on the pipeline of the low-pressure steam outlet of the steam drum 7. The first pipeline is connected to the low-pressure steam inlet of the first medium-pressure cylinder, and the second pipeline is connected to the low-pressure steam inlet of the second medium-pressure cylinder. The distribution of the low-pressure steam is determined according to the cooling loads required by the first ammonia cooler 10 and the second ammonia cooler 11.

[0139] The gas ammonia outlet of the first ammonia cooler 10 is connected to the gas ammonia inlet of the first low-pressure cylinder of the waste heat refrigeration unit, and the gas ammonia outlet of the second ammonia cooler 11 is connected to the gas ammonia inlet of the second low-pressure cylinder of the waste heat refrigeration unit.

[0140] Adopt the waste heat refrigeration method for adapting to dynamic synthesis of green ammonia using the waste heat refrigeration system as Figure 2 shown:

[0141] 1) The raw material gas is pressurized to 14.5 MPaG by a compressor to obtain raw material compressed gas, which is preheated to 145 °C by the inlet / outlet heat exchanger 1 and then enters the ammonia synthesis tower 5 for ammonia synthesis reaction to obtain synthesis gas.

[0142] 2) The preheated raw material compressed gas undergoes an ammonia synthesis reaction in the ammonia synthesis tower to obtain synthesis gas; the catalyst in the ammonia synthesis tower is an iron-based catalyst Amomax-10.

[0143] The synthesis gas is transported to the waste heat boiler to provide waste heat for the waste heat boiler, and the waste heat boiler by-produces low-pressure steam; the pressure of the low-pressure steam is adjusted to 1 MPaG; the temperature of the low-pressure steam is 159 °C; the low-pressure steam enters the steam drum connected to the waste heat boiler.

[0144] After the synthesis gas recovers the reaction heat in the waste heat boiler, it is cooled by the boiler feed water heater to obtain cooled synthesis gas with a temperature of 165 °C; after the boiler feed water is preheated by the boiler feed water heater, it enters the waste heat boiler.

[0145] 3) Cool the synthesis gas processed in step 2) through a multi-stage cooler system:

[0146] The syngas after being processed in step 2) is cooled successively by an inlet and outlet heat exchanger, a water cooler and a cold exchanger; the temperature of the syngas after being cooled by the inlet and outlet heat exchanger is 76 °C; the temperature of the syngas after being cooled by the water cooler is 40 °C; the syngas after being cooled by the water cooler exchanges heat with the cold gas in its shell side in the cold exchanger, and the temperature of the syngas after being cooled by the cold exchanger is 31 °C;

[0147] Then it is cooled by a cooling and condensing system:

[0148] The syngas after being cooled by the cold exchanger is cooled to 12 °C by the first ammonia cooler and cooled to -8 °C (tube side outlet temperature) by the second ammonia cooler; ammonia is liquefied;

[0149] The syngas after being cooled by the second ammonia cooler enters an ammonia separator to separate liquid ammonia;

[0150] The gas separated by the ammonia separator enters the shell side of the cold exchanger to recover cold energy and then enters the recycle section of the syngas compressor (i.e., recycle gas) for the next round of cycle;

[0151] The liquid ammonia separated by the ammonia separator is depressurized to 1.6 MPaG, preheated to 0 °C by the cold recovery heat exchanger and sent to the product storage area; the flash gas (high-temperature and high-pressure gas, when the pressure drops rapidly, the flashed gas is the flash gas) goes to the low-pressure section of the fresh gas compressor for reuse;

[0152] The liquid ammonia discharged from the waste heat refrigeration unit recovers cold energy in the cold recovery heat exchanger, and then is transported to the first ammonia cooler and the second ammonia cooler for heat exchange and vaporization. The gaseous ammonia enters the waste heat refrigeration unit for recycling.

[0153] Taking 100% production load as an example, the first ammonia cooler cooling (primary ammonia cooling) requires a cooling capacity of 4331.5 kW and a refrigeration temperature of 7.3 °C. The second ammonia cooler cooling (secondary ammonia cooling) requires a cooling capacity of 3317.8 kW and a refrigeration temperature of -13 °C (shell side operating temperature); while at this time, the maximum by-product steam production of the process is 28.38 t / h and the average amount is 16.5 t / h. After adopting waste heat refrigeration, the first ammonia cooler cooling (primary ammonia cooling) requires a cooling capacity of 4331.5 kW and uses 9.2 t / h of waste heat. The second ammonia cooler cooling (secondary ammonia cooling) requires a cooling capacity of 3317.8 kW and uses 11.9 t / h of waste heat; for the maximum steam surplus, there is still 7.28 t / h more. Considering the operation safety of the unit, it can be used for the refrigeration output of the secondary ammonia cooling in summer or for winter heating.

[0154] The specific parameters are shown in Table 1.

[0155] Table 1 Specific parameters involved taking 100% production load as an example

[0156]

[0157]

[0158] The relationship between the amount of by-product low-pressure steam as a heat source and the ammonia synthesis production load is close to linear, specifically as Figure 5 shown. Figure 5 This is the relationship diagram between the amount of by-product low-pressure steam as a heat source and the ammonia synthesis production load in Embodiment 1 of the present utility model. From Figure 5 it can be seen that the by-product steam output and the production load basically show a linear relationship.

[0159] The relationship between the cooling capacity required for the first ammonia cooler and the ammonia synthesis production load is specifically as Figure 6 shown. Figure 6 This is the relationship diagram between the cooling capacity required for the first ammonia cooler of the present utility model and the ammonia synthesis production load. The relationship between the cooling capacity required for the second ammonia cooler and the ammonia synthesis production load is specifically as Figure 7 shown. Figure 7 This is the relationship diagram between the cooling capacity required for the second ammonia cooler of the present utility model and the ammonia synthesis production load. From Figure 6 and Figure 7 it can be seen that ammonia refrigeration also basically shows a linear relationship at low loads, but as the production load further increases, the growth rate of the required cooling capacity decreases and the curve tends to be flat.

[0160] Under different loads, the required amount and remaining amount of by-product low-pressure steam for the waste heat refrigeration unit are shown in Table 2.

[0161] Table 2 Steam relationship under different production loads

[0162]

[0163]

[0164] Note: The above takes into account a 10% cooling loss.

[0165] From Table 2, taking the 100% operating condition as an example, the total amount of by-product steam is 28.38 t / h, the first ammonia cooler requires a cooling capacity of 4331.5 kW, and the corresponding steam consumption is 9.2 t / h; the second ammonia cooler requires a cooling capacity of 3318 kW, and the corresponding steam consumption is 11.9 t / h; there is still 7.28 t / h remaining for winter heating or the whole plant process deaerator.

[0166] Although both the by-product steam and the required cooling capacity fluctuate according to the production load, the waste heat refrigeration technology can achieve the coupling of cooling capacity and heat quantity under different operating conditions, and there is still surplus steam, which is sufficient to support the safe operation of the unit.

[0167] The load of the synthetic green ammonia plant fluctuates strongly, and there is a working condition of continuous low-load operation for a long time. The waste heat refrigeration unit uses the by-product low-pressure steam to dynamically match the cooling capacity required by the cooling condenser system. The waste heat refrigeration unit replaces the ammonia ice machine. The annual electricity consumption required by the waste heat refrigeration unit is: (53 + 57.4) × 8000 × 0.4 = 353,300 yuan, and the operating cost is relatively low.

[0168] The green ammonia coupled with waste heat power generation technology in the prior art: When the synthetic ammonia production is at full load, the by-product steam volume is 23.26 t / h. Therefore, this steam volume needs to be used as the design benchmark for the rated load of the saturated steam generator set; when the synthetic ammonia production load in summer is 20%, the by-product steam volume is 4.65 t / h. At present, the minimum operating load requirement of the saturated steam generator set must be greater than 30% of the rated load, and the steam volume generated by the lowest load of the whole plant is 4.65 t / h ≤ 7 t / h (23.26 t / h × 30%), which cannot ensure that the saturated steam generator set can operate under the lowest working conditions. Therefore, it is necessary to add an accumulator as an auxiliary facility to help the saturated steam generator set to still operate normally under the lowest load conditions. In extreme cases, the steam generator set will no longer be able to operate normally, and the steam will be forced to be vented. If the accumulator is added (taking the shortest 18 hours as an example, 7 additional 100 m 3 accumulators) will greatly increase the investment and floor area.

[0169] Compared with the existing green ammonia coupled with waste heat power generation technology, the waste heat refrigeration technology adopted by the present utility model has the following advantages:

[0170] 1) Strong dynamic matching:

[0171] Combined with the new energy output curve, energy storage and hydrogen storage tank configuration, there are often thousands of hours of production load in the green ammonia synthesis plant under 20% operation throughout the year, among which there are continuous extreme low-load working conditions for dozens of hours. A single waste heat generator set cannot maintain normal operation, and it is necessary to add an additional steam accumulator to meet the normal operation of the unit when the production load is 20% for a long time.

[0172] Through the waste heat refrigeration technology, the by-product steam can be effectively utilized, the cooling capacity required for ammonia synthesis can be dynamically matched, the direct conversion of the cold and hot ends can be completed, and the fluctuation can be adapted to the fluctuation.

[0173] 2) Low operating cost:

[0174] Power generation using the above-mentioned green ammonia coupled with waste heat power generation technology: Considering that when the operating load of the ammonia synthesis plant is above 30%, the waste heat power generation unit can operate continuously, and the annual power generation capacity is: 10,506,000 KW; the annual power consumption required for two ammonia ice machines: (1400 + 1100) × 8000 = 20,000,000 KW; the annual electricity cost required is: (20,000,000 - 10,506,000) × 0.4 yuan / KW = 3.7976 million yuan;

[0175] Refrigeration using the system and method provided by the present invention: At this time, the waste heat refrigeration unit replaces the ammonia ice machine, and the annual power consumption required for the waste heat refrigeration unit is: (53 + 57.4) × 8000 × 0.4 = 353,300 yuan.

[0176] The annual electricity cost savings is 3.7976 - 0.3533 = 3.4443 million yuan.

[0177] In summary, fluctuations in upstream raw material input lead to changes in production load, resulting in different reaction heats. The waste heat after the reaction can by-produce saturated steam at 0.3 - 2.5 MPaG. The saturated steam output is basically linearly distributed with the production load. Although the total cooling demand is not linearly distributed with the production load, as the production load increases, the growth rate of the cooling demand decreases. The by-produced steam can fully meet the demand for waste heat refrigeration, and there is still a certain margin, which is sufficient to maintain the overall safe operation.

[0178] The present invention utilizes waste heat refrigeration technology to achieve the coupling between the fluctuating by-produced steam output and the fluctuating cooling demand in the green ammonia project, and completes the direct conversion of the cold and hot ends, which conforms to the concept and production principle of green hydrogen and green ammonia.

[0179] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A waste heat refrigeration system adapted to dynamically synthesize green ammonia, comprising: A multi-stage cooler system; A synthetic ammonia reaction system; the raw material compressed gas inlet of the synthetic ammonia reaction system is connected to the raw material compressed gas outlet of the multi-stage cooler system; A waste heat boiler connected to the synthetic gas outlet of the synthetic ammonia reaction system; the synthetic gas inlet of the multi-stage cooler system is connected to the synthetic gas outlet of the waste heat boiler; A cooling condenser system; the synthetic gas inlet of the cooling condenser system is connected to the synthetic gas outlet of the multi-stage cooler system; A product recovery system; the synthetic gas inlet of the product recovery system is connected to the synthetic gas outlet of the cooling condenser system; the recycle gas outlet of the product recovery system is connected to the recycle gas inlet of the multi-stage cooler system; A waste heat refrigeration unit; the low-pressure steam inlet of the waste heat refrigeration unit is connected to the low-pressure steam outlet of the waste heat boiler; the liquid ammonia outlet of the waste heat refrigeration unit is connected to the liquid ammonia inlet of the product recovery system; the gaseous ammonia inlet of the waste heat refrigeration unit is connected to the gaseous ammonia outlet of the cooling condenser system.

2. The waste heat refrigeration system according to claim 1, characterized in that, The multi-stage cooler system includes an inlet and outlet heat exchanger, a water cooler, and a cold exchanger connected in sequence; The synthetic gas inlet of the water cooler is connected to the synthetic gas outlet of the inlet and outlet heat exchanger; the synthetic gas inlet of the cold exchanger is connected to the synthetic gas outlet of the water cooler; the recycle gas inlet of the cold exchanger is connected to the recycle gas outlet of the product recovery system.

3. The waste heat refrigeration system according to claim 2, wherein, The synthetic ammonia reaction system includes an ammonia synthesis tower, a molten salt heater, a molten salt heat storage unit, and an electric heater.

4. The waste heat refrigeration system according to claim 3, characterized in that, The waste heat refrigeration system further includes: a waste heat boiler and a steam drum; The synthetic gas inlet of the waste heat boiler is connected to the synthetic gas outlet of the ammonia synthesis tower; the synthetic gas inlet of the multi-stage cooler system is connected to the synthetic gas outlet of the waste heat boiler; the low-pressure steam outlet of the waste heat boiler is connected to the steam drum.

5. The waste heat refrigeration system according to claim 4, wherein, The waste heat refrigeration system further includes a boiler feed water heater; The synthetic gas inlet of the boiler feed water heater is connected to the synthetic gas outlet of the waste heat boiler; the boiler feed water outlet of the boiler feed water heater is connected to the boiler feed water inlet of the waste heat boiler; the synthetic gas outlet of the boiler feed water heater is connected to the synthetic gas inlet of the inlet and outlet heat exchanger.

6. The waste heat refrigeration system according to claim 5, characterized in that, The cooling condenser system includes a first ammonia cooler and a second ammonia cooler connected in sequence; The synthetic gas inlet of the first ammonia cooler is connected to the synthetic gas outlet of the cold exchanger, and the synthetic gas inlet of the second ammonia cooler is connected to the synthetic gas outlet of the first ammonia cooler.

7. The waste heat refrigeration system according to claim 6, characterized in that, The product recovery system includes: an ammonia separator, and a cold recovery heat exchanger connected to the liquid ammonia outlet of the ammonia separator; The synthetic gas inlet of the ammonia separator is connected to the synthetic gas outlet of the second ammonia cooler; the tube-side liquid ammonia inlet of the cold recovery heat exchanger is connected to the liquid ammonia outlet of the ammonia separator; the gas outlet of the ammonia separator is connected to the recycle gas inlet of the cold exchanger; The liquid ammonia product discharged from the tube-side liquid ammonia outlet of the cold recovery heat exchanger is sent to the product tank area.

8. The waste heat refrigeration system according to claim 7, wherein, The waste heat refrigeration unit includes a first waste heat refrigeration unit and a second waste heat refrigeration unit; The first waste heat refrigeration unit includes: The first medium-pressure cylinder; The first condenser; the ammonia vapor inlet of the first condenser is connected to the ammonia vapor outlet of the first medium-pressure cylinder; the liquid ammonia outlet pipeline of the first condenser is connected to the liquid ammonia inlet of the first ammonia cooler through the first shell pass of the cold recovery heat exchanger; The first low-pressure cylinder: the ammonia gas inlet of the first low-pressure cylinder is connected to the ammonia gas outlet of the first ammonia cooler; The first rich and lean liquid heat exchanger; the rich liquid inlet of the first rich and lean liquid heat exchanger is connected to the rich liquid outlet of the first low-pressure cylinder, and the rich liquid outlet of the first rich and lean liquid heat exchanger is connected to the rich liquid inlet of the first medium-pressure cylinder; the lean liquid inlet of the first rich and lean liquid heat exchanger is connected to the lean liquid outlet of the first medium-pressure cylinder, and the lean liquid outlet of the first rich and lean liquid heat exchanger is connected to the lean liquid inlet of the first low-pressure cylinder; The second waste heat refrigeration unit includes: The second medium-pressure cylinder; The second condenser; the ammonia vapor inlet of the second condenser is connected to the ammonia vapor outlet of the second medium-pressure cylinder; the liquid ammonia outlet pipeline of the second condenser is connected to the liquid ammonia inlet of the second ammonia cooler through the second shell pass of the cold recovery heat exchanger; The second low-pressure cylinder: the ammonia gas inlet of the second low-pressure cylinder is connected to the ammonia gas outlet of the second ammonia cooler; The second rich and lean liquid heat exchanger; the rich liquid inlet of the second rich and lean liquid heat exchanger is connected to the rich liquid outlet of the second low-pressure cylinder, and the rich liquid outlet of the second rich and lean liquid heat exchanger is connected to the rich liquid inlet of the second medium-pressure cylinder; the lean liquid inlet of the second rich and lean liquid heat exchanger is connected to the lean liquid outlet of the second medium-pressure cylinder, and the lean liquid outlet of the second rich and lean liquid heat exchanger is connected to the lean liquid inlet of the second low-pressure cylinder.

9. The waste heat refrigeration system according to claim 8, wherein A first solution pump is provided on the pipeline between the first low-pressure cylinder and the first rich and lean liquid heat exchanger.

10. The waste heat refrigeration system according to claim 8, wherein A second solution pump is provided on the pipeline between the second low-pressure cylinder and the second rich and lean liquid heat exchanger.

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