A refrigeration system, refrigeration method and application based on absorption-type composite ammonia carrier

Abstract

The present invention provides a refrigeration system, a refrigeration method and an application based on an absorption-type composite ammonia carrier, belonging to the field of refrigeration technology. The refrigeration system comprises: a generator, to which a composite ammonia carrier is added; an ammonia liquefier, connected and communicated with the generator; an evaporator, connected and communicated with the ammonia liquefier, and connected to a refrigerant circulation pipeline at a refrigeration user end; an ammonia recovery reactor, the ammonia recovery reactor is connected and communicated with the evaporator, and is connected and communicated with the generator to form a circulation loop; a cooling water system, the cooling water system comprising a cooling water supply pipeline and a cooling water return pipeline, for converting the ammonia liquid in the ammonia liquefier into liquid ammonia and discharging the heat of dissolution in the ammonia recovery reactor and the heat of liquefaction of the ammonia in the ammonia liquefier; the refrigeration system with a sodium thiocyanate-based absorption-type composite ammonia carrier provided by the present invention can achieve refrigeration in a wide temperature range of -50°C to 10°C, filling the technical gap of absorption refrigeration in the field of industrial deep cooling.

Description

Technical Field

[0001] The present invention belongs to the field of refrigeration technology, and specifically relates to a refrigeration system, a refrigeration method and an application thereof based on an absorption-type composite ammonia carrier. Background Art

[0002] In energy-intensive industries, the operational efficiency and energy utilization of thermal power plants have always been a focus of industry attention. Traditional thermal power plants often face the problem of low-load operation during the off-season due to reduced heat demand. This results in a large amount of low-grade thermal energy (such as exhaust heat) being underutilized, resulting in energy waste and reduced economic benefits. Furthermore, while existing compression refrigeration technology is mature, it relies on high-grade electricity or medium- and high-pressure steam as a power source, which not only increases energy consumption but also increases operating costs and carbon emissions.

[0003] While absorption refrigeration technology can currently utilize low-grade thermal energy for cooling, its core working fluids have limitations. For example, ethylenediamine-water tends to crystallize at low temperatures and has a limited cooling depth. While traditional ammonia-water working fluids offer good cooling performance, ammonia's solubility in these fluids is often low, and its corrosive nature places higher demands on system safety. Furthermore, existing absorption refrigeration systems still have room for improvement in terms of working fluid stability, energy efficiency, and load regulation range.

[0004] To address the above problems, there is an urgent need to develop a new type of absorption refrigeration system that can not only efficiently utilize the low-grade waste heat of thermal power plants, but also improve refrigeration efficiency, safety and environmental friendliness by optimizing the working fluid formula and system design. Summary of the Invention

[0005] To address the above technical issues, the present invention proposes a sodium thiocyanate-based absorption composite ammonia carrier refrigeration system. Through innovative working fluid formulation and cycle design, it solves the technical difficulties of efficient utilization of low-grade waste heat and deep refrigeration, and provides a feasible technical path for the trigeneration of heat, cooling and power in thermal power plants. The details are as follows:

[0006] In a first aspect, the present invention provides a refrigeration system of a sodium thiocyanate-based absorption composite ammonia carrier, comprising:

[0007] A generator is added to the generator, wherein the composite ammonia carrier absorbs the refrigerant-ammonia; the composite ammonia carrier absorbs the refrigerant-ammonia to form an ammonia composite rich solution; the generator is used to heat the ammonia composite rich solution and release ammonia gas, at which point the ammonia composite rich solution is converted into an ammonia composite lean solution;

[0008] an ammonia liquefier, used to convert the ammonia gas released by the generator into liquid ammonia;

[0009] Evaporator, used to evaporate liquid ammonia into ammonia gas for refrigeration;

[0010] Ammonia recovery reactor, used to redissolve the ammonia output from the evaporator into the ammonia composite lean solution;

[0011] Cooling water system, used to provide cooling medium for ammonia liquefier and ammonia recovery reactor;

[0012] The generator, ammonia liquefier, evaporator, and ammonia recovery reactor are connected and communicated in sequence to form a circulation loop; the cooling water system is connected and communicated with the ammonia liquefier and ammonia recovery reactor.

[0013] Furthermore, the refrigeration system comprises:

[0014] A generator, wherein a composite ammonia carrier is added to the generator, and the composite ammonia carrier absorbs the refrigerant-ammonia; the composite ammonia carrier absorbs the refrigerant-ammonia to form an ammonia composite rich solution; the generator is used to heat the ammonia composite rich solution by an external heat source to release gaseous refrigerant-ammonia, i.e., ammonia gas, at which point the ammonia composite rich solution is converted into an ammonia composite lean solution;

[0015] an ammonia liquefier, one end of which is connected to and communicates with the generator, and is used to convert the ammonia gas released by the generator into liquid ammonia;

[0016] an evaporator connected to and in communication with the other end of the ammonia liquefier, and configured to evaporate liquid ammonia into ammonia gas for refrigeration;

[0017] A throttle valve is connected between the ammonia liquefier and the evaporator;

[0018] The evaporator is connected to the secondary refrigerant circulation pipeline of the refrigeration user end, and the secondary refrigerant circulation pipeline is isolated from the refrigerant-ammonia. The secondary refrigerant exchanges heat with the refrigerant-ammonia through a partition heat exchange method in the evaporator. The secondary refrigerant temperature decreases as the liquid ammonia evaporates into ammonia gas, absorbs heat, and is then transported to the refrigeration user end to achieve cooling for the user;

[0019] The coolant remains in liquid form throughout the entire process without undergoing phase change, and its heat absorption process is driven by the evaporation phase change of liquid ammonia;

[0020] The heat exchange tube side and shell side of the evaporator are strictly isolated to ensure that ammonia (R717) has no direct contact with the brine. The brine exchanges heat with the refrigerant-ammonia through the tube wall in the evaporator without vaporizing itself.

[0021] The brine circulation pipeline is physically isolated from the ammonia circulation channel inside the evaporator by a metal wall, forming a partition-type heat exchange structure; the brine flows in the shell side of the evaporator and performs non-contact heat exchange with the liquid ammonia in the tube side. After absorbing the latent heat of evaporation of ammonia, the temperature of the brine is reduced. The cooled brine is transported to the refrigeration user end through a closed pipeline. After completing the refrigeration, the brine with a higher temperature returns to the evaporator to form an independent closed cycle;

[0022] an ammonia recovery reactor, one end of which is connected and communicated with the evaporator, and the other end of which is connected and communicated with the generator to form a circulation loop;

[0023] The ammonia recovery reactor is used to redissolve the evaporated ammonia in the ammonia compound lean solution from the generator to form an ammonia compound rich solution, which is then refluxed to the generator for recycling;

[0024] A cooling water system comprising a cooling water supply line (CWS) and a cooling water return line (CWR);

[0025] The cooling water supply pipeline (CWS) is connected to the cooling water inlet of the ammonia recovery reactor and the ammonia liquefier to provide cooling medium for both.

[0026] The cooling water return line (CWR) returns from the cooling water outlet of the ammonia recovery reactor and the ammonia liquefier to form a closed loop, and removes the absorption heat and condensation heat from the system;

[0027] The cooling water system is used to convert the ammonia gas in the ammonia liquefier into liquid ammonia and discharge the heat of dissolution in the ammonia recovery reactor and the heat of liquefaction of the ammonia gas in the ammonia liquefier.

[0028] Furthermore, the composite ammonia carrier comprises the following components in terms of mass ratio:

[0029] Sodium thiocyanate (NaSCN) 50-55 parts;

[0030] Ethylenediamine (EDA) 8-10 parts;

[0031] 3-5 parts of ionic liquid [BMIM][BF4];

[0032] Cerium nitrate (Ce(NO3)3) 0.2-0.5 parts;

[0033] Benzotriazole (BTA) 0.1-0.2 parts;

[0034] Nano silicon dioxide (nano SiO2) 0.1-0.2 parts;

[0035] Octanol (C8H 17 OH) 2-3 parts;

[0036] The rest is ionized water; the total salt concentration of the composite ammonia carrier is 50-60%.

[0037] The amino groups in EDA molecules can form strong hydrogen bond complexes with ammonia, increasing the solubility of ammonia from 20-25% in traditional NaSCN solution to 35-40%. + With SCN- The hydrogen bonds between ammonia molecules are destroyed, and EDA captures free ammonia through hydrogen bonds, forming a "dissolution-complexation" dual mechanism; the hydrophobic imidazole ring of [BMIM][BF4] can reduce the competitive adsorption of ammonia by water, further improving the ammonia loading efficiency; the use of this composite ammonia carrier can reduce the solution circulation volume, reduce pump power consumption, and improve the system COP by 10-15%.

[0038] At the same time, EDA forms a low-melting eutectic mixture with water and ammonia, inhibiting the crystallization of ice and salt. Traditional NaSCN solutions crystallize at -10°C, while this composite ammonia carrier remains a uniform liquid without crystallization at -50°C to -60°C. [BMIM][BF4] reduces the viscosity of the solution, improves fluidity below -50°C, and avoids pipeline blockage, making it suitable for industrial cryogenic scenarios such as cold chain logistics or chemical refrigeration.

[0039] The preparation method is as follows:

[0040] Step 1: Heat deionized water to 70±2°C, slowly add sodium thiocyanate under nitrogen protection, and stir at 80-120 rpm until completely dissolved;

[0041] Step 2: Cool the solution to 35 ± 2 °C and add ethylenediamine dropwise at a rate of 1 mL / min. Disperse the solution with ultrasound assistance (40 kHz, 10 min).

[0042] Step 3: Maintaining 35 ± 2 °C, add ionic liquid [BMIM][BF4] and nano-SiO2 (particle size 20 nm), and disperse with ultrasound (40 kHz) for 15 min;

[0043] Step 4: Dissolve cerium nitrate in 5 mL of deionized water, filter, add to the main solution, and introduce CO2 (0.1 MPa, 30 minutes) to form a cerium carbonate Ce2(CO3)3 anticorrosion film;

[0044] Step 5: Dissolve benzotriazole in 5 mL of ethanol and add to the system. Stir for 10 minutes, then add octanol dropwise and stir until there is no foam.

[0045] Step 6: Add deionized water to a total salt concentration of 50-60% to obtain a composite ammonia carrier.

[0046] Furthermore, the generator and the ammonia recovery reactor are also connected and communicated with a GAX heat exchanger, and the GAX heat exchanger is used to recover the waste heat of the ammonia compound lean solution to preheat the ammonia compound rich solution;

[0047] A solution pump is further connected between the GAX heat exchanger and the ammonia recovery reactor, and the solution pump is used to transport the ammonia composite rich solution in the ammonia recovery reactor to the GAX heat exchanger and the generator.

[0048] Furthermore, the GAX heat exchanger forms a pipeline loop with the generator, and the GAX heat exchanger forms a pipeline loop with the ammonia recovery reactor; the ammonia compound rich solution and the ammonia compound lean solution undergo a wall-to-wall heat exchange in the GAX heat exchanger, thereby achieving uniform heat release in the pipeline and more efficient heat utilization.

[0049] The ammonia compound rich solution is heated in the generator to release part of the low-boiling point ammonia and then becomes an ammonia compound lean solution. It then exchanges heat with the ammonia compound rich solution from the ammonia recovery reactor through the GAX heat exchanger and returns to the ammonia recovery reactor. It contacts and dissolves with the gaseous ammonia from the evaporator to increase the solution concentration. The heat generated during the dissolution process is removed by the cooling water system. The ammonia compound rich solution that has been fully dissolved with ammonia is then transported by the solution pump, exchanges heat in the GAX, and then returns to the generator, completing the solution circulation process.

[0050] Furthermore, the external heat source used by the generator is the waste heat steam carried by the high-temperature and high-pressure wastewater discharged through the continuous sewage discharge system during the actual operation of the thermal power plant, with a temperature of 80-150°C.

[0051] Furthermore, the waste heat steam releases heat in the generator to form condensate which flows back to the boiler system for recycling and / or is heated again by the waste heat steam to form an external heat source which enters the generator for recycling.

[0052] Furthermore, the refrigerant is ammonia (Refrigerant 717, R717).

[0053] In a second aspect, the present invention provides a refrigeration method for a refrigeration system using a sodium thiocyanate-based absorption-type composite ammonia carrier, comprising the following steps:

[0054] S1, thermal drive release:

[0055] The composite ammonia carrier is introduced into the generator and then absorbs the refrigerant-ammonia to form an ammonia composite rich solution. The low-grade waste heat of 80-150°C from the thermal power plant is used as an external heat source to heat the ammonia in the ammonia composite rich solution to release ammonia gas, thereby obtaining an ammonia composite lean solution and ammonia gas.

[0056] S2. Ammonia liquefaction:

[0057] The ammonia gas released in step S1 is introduced into an ammonia liquefier, and the ammonia gas is cooled by a cooling water system to liquefy into liquid ammonia;

[0058] S3, deep cooling:

[0059] Liquid ammonia is depressurized by the throttle valve and then enters the evaporator for evaporation and refrigeration;

[0060] S4, coolant circulation:

[0061] The refrigerant circulates in the refrigerant channel of the evaporator through an independent refrigerant circulation pipeline, and is transported to the refrigeration user end to provide cooling for the user after cooling.

[0062] S5. Ammonia absorption:

[0063] The evaporated ammonia enters the ammonia recovery reactor, where it comes into contact with and absorbs the ammonia compound lean solution from the generator, re-forming an ammonia compound rich solution;

[0064] S6, GAX heat exchange:

[0065] At the same time, the ammonia compound lean solution from the generator and the ammonia compound lean solution from the ammonia recovery reactor are subjected to inter-wall heat exchange through the GAX heat exchanger to achieve uniform heat release in the pipeline and more efficient use of heat;

[0066] S7, solution circulation:

[0067] The ammonia-rich composite solution after heat exchange is transported by the solution pump and returned to the generator to complete the cycle.

[0068] Alternatively, a refrigeration method for a refrigeration system using a sodium thiocyanate-based absorption-type composite ammonia carrier comprises the following steps:

[0069] S1, thermal drive release:

[0070] The composite ammonia carrier is introduced into the generator and then absorbs the refrigerant-ammonia to form an ammonia composite rich solution. The low-grade waste heat of 80-150°C from the thermal power plant is used as an external heat source to heat the ammonia in the ammonia composite rich solution to release ammonia gas, thereby obtaining an ammonia composite lean solution and ammonia gas.

[0071] S2. Ammonia liquefaction:

[0072] The ammonia gas released in step S1 is introduced into an ammonia liquefier, and the ammonia gas is cooled by a cooling water system to liquefy into liquid ammonia;

[0073] S3, deep cooling:

[0074] Liquid ammonia is depressurized by the throttle valve and then enters the evaporator for evaporation and refrigeration;

[0075] S4, coolant circulation:

[0076] The refrigerant circulates in the refrigerant channel of the evaporator through an independent refrigerant circulation pipeline, and is transported to the refrigeration user end to provide cooling for the user after cooling.

[0077] S5. Ammonia absorption:

[0078] The evaporated ammonia enters the ammonia recovery reactor, where it comes into contact with and absorbs the ammonia compound lean solution from the generator, re-forming an ammonia compound rich solution;

[0079] S6, solution circulation:

[0080] The ammonia-rich solution is transported by the solution pump and returned to the generator to complete the cycle.

[0081] In a third aspect, the present invention provides an application of a sodium thiocyanate-based absorption-type composite ammonia carrier in a refrigeration system for industrial refrigeration and freezing or civil air conditioning refrigeration.

[0082] Compared with the prior art, the present invention has the following beneficial effects:

[0083] 1. The existing ethylenediamine-water working fluid is easy to crystallize and has a limited refrigeration depth. The refrigeration system of the sodium thiocyanate-based absorption composite ammonia carrier provided by the present invention can achieve refrigeration in a wide temperature range of -50°C to 10°C, filling the technical gap of absorption refrigeration in the field of industrial deep refrigeration.

[0084] 2. In the non-heating season, traditional thermal power plants experience reduced demand for heat and lower unit loads, resulting in a large amount of low-grade thermal energy (such as continuous exhaust heat) not being fully utilized. The present invention uses a sodium thiocyanate-based absorption composite ammonia carrier refrigeration system and uses 80-150°C waste heat steam discharged from the thermal power plant's continuous sewage discharge system as a driving heat source to achieve the conversion of low-grade thermal energy into cold energy. This solves the problem of energy waste during low-load operation in the non-heating season of traditional thermal power plants, achieves cascade energy utilization, and recovers the waste heat of the lean solution through the GAX heat exchanger for preheating the rich solution. The system's comprehensive energy efficiency ratio (COP) can reach 0.7-0.8, which is more than 30% higher than that of the traditional single-effect absorption system.

[0085] 3. The sodium thiocyanate-based absorption-type composite ammonia carrier refrigeration system provided by the present invention adopts a closed-loop design of "generator-liquefier-evaporator-GAX heat exchanger-recovery reactor" with an ammonia recovery rate of >99%. During the entire refrigeration process, there is no need to continue adding refrigerant and carrier. Circular refrigeration can be achieved by only continuously inputting waste heat recovery, which saves a lot of costs. At the same time, the refrigerant used in the present invention is independently closed-circulated, and the refrigeration user end does not need to handle ammonia, which significantly reduces safety risks.

[0086] 4. The refrigeration system of the sodium thiocyanate-based absorption-type composite ammonia carrier provided by the present invention uses the sodium thiocyanate-based absorption-type composite ammonia carrier as the absorbent of the refrigerant. The traditional NaSCN aqueous solution has a low solubility of ammonia, about 20-25% by mass, resulting in a small refrigeration capacity of the system and the need for a larger volume of solution circulation. The sodium thiocyanate-based absorption-type composite ammonia carrier provided by the present invention has a significantly increased ammonia loading capacity, which can be as high as 38-42% by mass, saving a large amount of resources and floor space.

[0087] 5. The present invention achieves efficient heat utilization and stable system operation through a dual-circulation design (ammonia circulation and solution circulation) and a GAX heat exchanger:

[0088] Ammonia cycle: After liquefaction, throttling and pressure reduction, ammonia enters the evaporator for refrigeration. The evaporated ammonia is absorbed by the ammonia compound lean solution, forming a rich solution that flows back to the generator, completing a closed cycle.

[0089] Solution circulation: The ammonia-compounded rich solution exchanges heat with the lean solution in the GAX heat exchanger, preheating the rich solution and cooling the lean solution, reducing the demand for external heat sources. The lean solution after heat exchange returns to the absorber, contacts and dissolves with ammonia gas to form a rich solution for continued circulation.

[0090] GAX heat exchanger: Through inter-wall heat exchange, heat is evenly released in the pipeline, which improves heat recovery efficiency and reduces energy consumption.

[0091] 6. The composite ammonia carrier provided by the present invention comprises the following components by weight: 50-55 parts of sodium thiocyanate (NaSCN); 8-10 parts of ethylenediamine (EDA); 3-5 parts of ionic liquid [BMIM][BF4]; 0.2-0.5 parts of cerium nitrate (Ce(NO3)3); 0.1-0.2 parts of benzotriazole (BTA); 0.1-0.2 parts of nano-silicon dioxide (nano-SiO2); 0.1-0.2 parts of octanol (C8H 17 OH) 2-3 parts; the rest is ionized water, the total salt concentration of the composite ammonia carrier is 50-60%; the amino group in the EDA molecule can form a strong hydrogen bond complex with ammonia, increasing the ammonia solubility from 20-25% of the traditional NaSCN solution to 35-40%, Na + With SCN - The EDA destroys hydrogen bonds between ammonia molecules, while the EDA captures free ammonia through hydrogen bonds, forming a dual "dissolution-complexation" mechanism. The hydrophobic imidazole ring of [BMIM][BF4] reduces competitive adsorption of ammonia by water, further improving ammonia loading efficiency. Nano-silica prevents organic amine volatilization and solution stratification, improving cycle stability and reducing working fluid loss. The use of this composite ammonia carrier can reduce solution circulation volume, reduce pump power consumption, and improve system COP by 10-15%. EDA forms a low-melting eutectic mixture with water and ammonia, inhibiting ice and salt crystallization. Conventional NaSCN solutions crystallize at -10°C, while this composite ammonia carrier remains a homogeneous liquid without crystals at -50°C to -60°C. [BMIM][BF4] reduces solution viscosity, improves fluidity below -50°C, and avoids pipeline blockage, making it suitable for industrial cryogenic applications such as cold chain logistics and chemical refrigeration. Furthermore, this carrier prevents the evaporation of ammonia carried by the water solvent during NaSCN heating, which can lead to working fluid loss. It effectively inhibits ammonia corrosion on pipelines and ensures ammonia desorption efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Figure 1 This is a schematic diagram of the refrigeration system flow of the sodium thiocyanate-based absorption-type composite ammonia carrier provided by the present invention. DETAILED DESCRIPTION

[0093] Example 1

[0094] A composite ammonia carrier, comprising the following components in mass ratio:

[0095] Sodium thiocyanate (NaSCN) 50-55 parts;

[0096] Ethylenediamine (EDA) 8-10 parts;

[0097] 3-5 parts of ionic liquid [BMIM][BF4];

[0098] Cerium nitrate (Ce(NO3)3) 0.2-0.5 parts;

[0099] Benzotriazole (BTA) 0.1-0.2 parts;

[0100] Nano silicon dioxide (nano SiO2) 0.1-0.2 parts;

[0101] Octanol (C8H 17 OH) 2-3 parts;

[0102] The rest is ionized water; the total salt concentration of the composite ammonia carrier is 50-60%.

[0103] The preparation method of the composite ammonia carrier is as follows:

[0104] Step 1: Heat deionized water to 70±2°C, slowly add sodium thiocyanate under nitrogen protection, and stir at 80-120 rpm until completely dissolved;

[0105] Step 2: Cool the solution to 35 ± 2 °C and add ethylenediamine dropwise at a rate of 1 mL / min. Disperse the solution with ultrasound assistance (40 kHz, 10 min).

[0106] Step 3: Maintaining 35 ± 2 °C, add ionic liquid [BMIM][BF4] and nano-SiO2 (particle size 20 nm), and disperse with ultrasound (40 kHz) for 15 min;

[0107] Step 4: Dissolve cerium nitrate in 5 mL of deionized water, filter, add to the main solution, and introduce CO2 (0.1 MPa, 30 minutes) to form a cerium carbonate Ce2(CO3)3 anticorrosion film;

[0108] Step 5: Dissolve benzotriazole in 5 mL of ethanol and add to the system. Stir for 10 minutes, then add octanol dropwise and stir until there is no foam.

[0109] Step 6: Add deionized water to a total salt concentration of 50-60% to obtain a composite ammonia carrier.

[0110] Example 2

[0111] A refrigeration system for a sodium thiocyanate-based absorption composite ammonia carrier, comprising:

[0112] A generator, wherein the composite ammonia carrier provided in Example 1 is added to the generator, wherein the composite ammonia carrier absorbs the refrigerant-ammonia; after the composite ammonia carrier absorbs the refrigerant-ammonia, it becomes an ammonia composite rich solution; the generator is used to heat the ammonia composite rich solution by an external heat source to release gaseous refrigerant-ammonia, i.e., ammonia gas, at which point the ammonia composite rich solution is converted into an ammonia composite lean solution;

[0113] an ammonia liquefier, one end of which is connected to and communicates with the generator, and is used to convert the ammonia gas released by the generator into liquid ammonia;

[0114] an evaporator connected to and in communication with the other end of the ammonia liquefier, and configured to evaporate liquid ammonia into ammonia gas for refrigeration;

[0115] A throttle valve is connected between the ammonia liquefier and the evaporator;

[0116] The evaporator is connected to the secondary refrigerant circulation pipeline of the refrigeration user end, and the secondary refrigerant circulation pipeline is isolated from the refrigerant-ammonia. The secondary refrigerant exchanges heat with the refrigerant-ammonia through a partition heat exchange method in the evaporator. The secondary refrigerant temperature decreases as the liquid ammonia evaporates into ammonia gas, absorbs heat, and is then transported to the refrigeration user end to achieve cooling for the user;

[0117] an ammonia recovery reactor, one end of which is connected and communicated with the evaporator, and the other end of which is connected and communicated with the generator to form a circulation loop;

[0118] The ammonia recovery reactor is used to redissolve the evaporated ammonia in the ammonia compound lean solution from the generator to form an ammonia compound rich solution, which is then refluxed to the generator for recycling;

[0119] A cooling water system comprising a cooling water supply pipeline and a cooling water return pipeline; the cooling water supply pipeline is connected to the cooling water inlet of the ammonia recovery reactor and the ammonia liquefier to provide cooling medium for both;

[0120] The cooling water return pipeline returns from the cooling water outlet of the ammonia recovery reactor and the ammonia liquefier to form a closed loop, and the absorption heat and condensation heat are discharged from the system;

[0121] The cooling water system is used to convert the ammonia gas in the ammonia liquefier into liquid ammonia and discharge the heat of dissolution in the ammonia recovery reactor and the heat of liquefaction of the ammonia gas in the ammonia liquefier;

[0122] Moreover, the generator and the ammonia recovery reactor are also connected and communicated with a GAX heat exchanger, and the GAX heat exchanger is used to recover the waste heat of the ammonia compound lean solution to preheat the ammonia compound rich solution.

[0123] Moreover, a solution pump is connected between the GAX heat exchanger and the ammonia recovery reactor, and the solution pump is used to transport the ammonia composite rich solution in the ammonia recovery reactor to the GAX heat exchanger and the generator.

[0124] Moreover, the GAX heat exchanger and the generator form a pipeline cycle, and the GAX heat exchanger and the ammonia recovery reactor form a pipeline cycle; the ammonia compound rich solution and the ammonia compound lean solution perform inter-wall heat exchange in the GAX heat exchanger.

[0125] Moreover, the external heat source used by the generator is the waste heat steam carried by the high-temperature and high-pressure wastewater discharged through the continuous sewage discharge system during the actual operation of the thermal power plant, with a temperature of 80-150°C.

[0126] Moreover, the waste heat steam forms condensate after releasing heat in the generator and flows back to the boiler system for recycling and / or is heated again by the waste heat steam to form an external heat source and enter the generator for recycling.

[0127] Furthermore, the refrigerant used was ammonia (Refrigerant 717, R717).

[0128] Example 3

[0129] A refrigeration method for a refrigeration system using a sodium thiocyanate-based absorption-type composite ammonia carrier comprises the following steps:

[0130] S1, thermal drive release:

[0131] The composite ammonia carrier provided in Example 1 is introduced into a generator and then absorbs refrigerant-ammonia to form an ammonia composite rich solution. The low-grade waste heat of 80-150°C from a thermal power plant is used as an external heat source to heat the ammonia in the ammonia composite rich solution to release ammonia gas, thereby obtaining an ammonia composite lean solution and ammonia gas.

[0132] S2. Ammonia liquefaction:

[0133] The ammonia gas released in step S1 is introduced into an ammonia liquefier, and the ammonia gas is cooled by a cooling water system to liquefy into liquid ammonia;

[0134] S3, deep cooling:

[0135] Liquid ammonia is depressurized by the throttle valve and then enters the evaporator for evaporation and refrigeration;

[0136] S4, coolant circulation:

[0137] The refrigerant circulates in the refrigerant channel of the evaporator through an independent refrigerant circulation pipeline, and is transported to the refrigeration user end to provide cooling for the user after cooling.

[0138] S5. Ammonia absorption:

[0139] The evaporated ammonia enters the ammonia recovery reactor, where it comes into contact with and absorbs the ammonia compound lean solution from the generator, re-forming an ammonia compound rich solution;

[0140] S6, GAX heat exchange:

[0141] At the same time, the ammonia compound lean solution from the generator and the ammonia compound lean solution from the ammonia recovery reactor pass through the GAX heat exchanger for inter-wall heat exchange to achieve uniform heat release in the pipeline;

[0142] S7, solution circulation:

[0143] The ammonia-rich composite solution after heat exchange is transported by the solution pump and returned to the generator to complete the cycle.

[0144] Example 4

[0145] A refrigeration method for a refrigeration system using a sodium thiocyanate-based absorption-type composite ammonia carrier comprises the following steps:

[0146] S1, thermal drive release:

[0147] The composite ammonia carrier provided in Example 1 is introduced into a generator and then absorbs refrigerant-ammonia to form an ammonia composite rich solution. The low-grade waste heat of 80-150°C from a thermal power plant is used as an external heat source to heat the ammonia in the ammonia composite rich solution to release ammonia gas, thereby obtaining an ammonia composite lean solution and ammonia gas.

[0148] S2. Ammonia liquefaction:

[0149] The ammonia gas released in step S1 is introduced into an ammonia liquefier, and the ammonia gas is cooled by a cooling water system to liquefy into liquid ammonia;

[0150] S3, deep cooling:

[0151] Liquid ammonia is depressurized by the throttle valve and then enters the evaporator for evaporation and refrigeration;

[0152] S4, coolant circulation:

[0153] The refrigerant circulates in the refrigerant channel of the evaporator through an independent refrigerant circulation pipeline, and is transported to the refrigeration user end to provide cooling for the user after cooling.

[0154] S5. Ammonia absorption:

[0155] The evaporated ammonia enters the ammonia recovery reactor, where it comes into contact with and absorbs the ammonia compound lean solution from the generator, re-forming an ammonia compound rich solution;

[0156] S6, solution circulation:

[0157] The ammonia-rich solution is transported by the solution pump and returned to the generator to complete the cycle.

[0158] Comparative Example 1

[0159] The difference between this comparative example and Example 1 is that no ethylenediamine is added to the composite ammonia carrier.

[0160] Comparative Example 2

[0161] The difference between this comparative example and Example 1 is that the composite ammonia carrier does not contain the ionic liquid [BMIM][BF4].

[0162] Comparative Example 3

[0163] The difference between this comparative example and Example 1 is that no cerium nitrate is added to the composite ammonia carrier.

[0164] Comparative Example 4

[0165] The difference between this comparative example and Example 1 is that no nanosilica is added to the composite ammonia carrier.

[0166] Comparative Example 5

[0167] The difference between this comparative example and Example 1 is that when preparing the composite ammonia carrier, CO2 is not introduced in step 4.

[0168] Experimental part

[0169] Experiment 1

[0170] The refrigeration system provided in Example 2 of the present invention has been applied in some projects. The specific benefits are shown in Table 1 below (Note: due to the owner's confidentiality requirements, the owner's name is not disclosed). As can be seen from Table 1, the use of the refrigeration system of the present invention can save a large amount of natural resources and significantly reduce costs.

[0171] Table 1 Refrigeration system application cases

[0172]

[0173] Experiment 2

[0174] The composite ammonia carriers provided in Example 1 and Comparative Examples 1-5 were placed in a sealed container, and ammonia gas was introduced to an equilibrium pressure (0.5 MPa). The ammonia solubility at different pressures was recorded. The saturated ammonia solutions were then placed in separate groups at -10°C, -20°C, -30°C, -40°C, and -50°C for 24 hours, and the presence of crystallization or precipitation was recorded. Subsequently, carbon steel and copper sheets were immersed in each of the saturated ammonia solutions (60°C for 7 days), and the corrosion rates were calculated using the weight loss method. The results are shown in Table 2.

[0175] As shown in Table 2, the ammonia composite ammonia carrier provided by the present invention achieves an ammonia solubility of 41.5% at 0.5 MPa, significantly higher than that of the comparative example. Furthermore, the ammonia composite ammonia carrier provided by the present invention remains a homogeneous liquid at -50°C, making it suitable for cryogenic applications. It also exhibits reduced corrosion to pipelines compared to the comparative example.

[0176] Table 2 Comparison of composite ammonia carrier performance

[0177]

Claims

1. A refrigeration system of sodium thiocyanate-based absorption composite ammonia carrier, characterized in that: include: A generator, wherein a composite ammonia carrier is added to the generator, and a refrigerant-ammonia is absorbed in the composite ammonia carrier; The composite ammonia carrier absorbs the refrigerant ammonia to form an ammonia composite rich solution; the generator is used to heat the ammonia composite rich solution and release ammonia gas. At this time, the ammonia composite rich solution is converted into an ammonia composite lean solution; an ammonia liquefier, used to convert the ammonia gas released by the generator into liquid ammonia; Evaporator, used to evaporate liquid ammonia into ammonia gas for refrigeration; The ammonia recovery reactor is used to redissolve the ammonia output from the evaporator in the ammonia compound lean solution and convert it into an ammonia compound rich solution again; Cooling water system, used to provide cooling medium for ammonia liquefier and ammonia recovery reactor; The generator, ammonia liquefier, evaporator, and ammonia recovery reactor are sequentially connected and communicated to form a circulation loop; the cooling water system is connected and communicated with the ammonia liquefier and ammonia recovery reactor; The composite ammonia carrier comprises the following components in terms of mass ratio: 50-55 parts of sodium thiocyanate; 8-10 parts of ethylenediamine; 3-5 parts of ionic liquid [BMIM][BF4]; 0.2-0.5 parts of cerium nitrate; 0.1-0.2 parts of benzotriazole; Nano silicon dioxide 0.1-0.2 parts; 2-3 parts of octanol; The rest is ionized water; the total salt concentration of the composite ammonia carrier is 50-60%.

2. A refrigeration system of a sodium thiocyanate-based absorption composite ammonia carrier according to claim 1, characterized in that: include: A generator, wherein a composite ammonia carrier is added to the generator, and a refrigerant-ammonia is absorbed in the composite ammonia carrier; The composite ammonia carrier absorbs the refrigerant-ammonia to form an ammonia composite rich solution; the generator is used to heat the ammonia composite rich solution through an external heat source to release gaseous refrigerant-ammonia, i.e., ammonia gas. At this point, the ammonia composite rich solution is converted into an ammonia composite lean solution; an ammonia liquefier, one end of which is connected to and communicates with the generator, and is used to convert the ammonia gas released by the generator into liquid ammonia; an evaporator connected to and in communication with the other end of the ammonia liquefier, and configured to evaporate liquid ammonia into ammonia gas for refrigeration; A throttle valve is connected between the ammonia liquefier and the evaporator; The evaporator is connected to the secondary refrigerant circulation pipeline of the refrigeration user end, and the secondary refrigerant circulation pipeline is isolated from the refrigerant-ammonia. The secondary refrigerant exchanges heat with the refrigerant-ammonia through a partition heat exchange method in the evaporator. The secondary refrigerant temperature decreases as the liquid ammonia evaporates into ammonia gas, absorbs heat, and is then transported to the refrigeration user end to achieve cooling for the user; an ammonia recovery reactor, one end of which is connected and communicated with the evaporator, and the other end of which is connected and communicated with the generator to form a circulation loop; The ammonia recovery reactor is used to redissolve the evaporated ammonia in the ammonia compound lean solution from the generator to form an ammonia compound rich solution, which is then refluxed to the generator for recycling; A cooling water system comprising a cooling water supply pipeline and a cooling water return pipeline; the cooling water supply pipeline is connected to the cooling water inlet of the ammonia recovery reactor and the ammonia liquefier to provide cooling medium for both; The cooling water return pipeline returns from the cooling water outlet of the ammonia recovery reactor and the ammonia liquefier to form a closed loop, and the absorption heat and condensation heat are discharged from the system; The cooling water system is used to convert the ammonia gas in the ammonia liquefier into liquid ammonia and discharge the heat of dissolution in the ammonia recovery reactor and the heat of liquefaction of the ammonia gas in the ammonia liquefier.

3. A refrigeration system of a sodium thiocyanate-based absorption composite ammonia carrier according to claim 2, characterized in that: The generator and the ammonia recovery reactor are also connected and communicated with a GAX heat exchanger, and the GAX heat exchanger is used to recover the waste heat of the ammonia compound lean solution to preheat the ammonia compound rich solution.

4. A refrigeration system of a sodium thiocyanate-based absorption composite ammonia carrier according to claim 3, characterized in that: A solution pump is also connected between the GAX heat exchanger and the ammonia recovery reactor, and the solution pump is used to transport the ammonia composite rich solution in the ammonia recovery reactor to the GAX heat exchanger and the generator; The GAX heat exchanger and the generator form a pipeline cycle, and the GAX heat exchanger and the ammonia recovery reactor form a pipeline cycle; the ammonia compound rich solution and the ammonia compound lean solution perform inter-wall heat exchange in the GAX heat exchanger.

5. A sodium thiocyanate-based absorption composite ammonia carrier refrigeration system according to claim 4, characterized in that: The external heat source used by the generator is the waste heat steam carried by the high-temperature and high-pressure wastewater discharged through the continuous sewage discharge system during the operation of the thermal power plant, with a temperature of 80-150°C.

6. A sodium thiocyanate-based absorption composite ammonia carrier refrigeration system according to claim 5, characterized in that: The waste heat steam releases heat in the generator to form condensate which flows back to the boiler system for recycling and / or is heated again by the waste heat steam to form an external heat source which enters the generator for recycling.

7. A refrigeration system of a sodium thiocyanate-based absorption composite ammonia carrier according to claim 1, characterized in that: The refrigerant used is ammonia (Refrigerant 717, R717).

8. A refrigeration method for a refrigeration system using a sodium thiocyanate-based absorption-type composite ammonia carrier according to claim 5, characterized in that: The steps include: S1, thermal drive release: The composite ammonia carrier is introduced into the generator and then absorbs the refrigerant-ammonia to form an ammonia composite rich solution. The low-grade waste heat of 80-150°C from the thermal power plant is used as an external heat source to heat the ammonia in the ammonia composite rich solution to release ammonia gas, thereby obtaining an ammonia composite lean solution and ammonia gas. S2. Ammonia liquefaction: The ammonia gas released in step S1 is introduced into an ammonia liquefier, and the ammonia gas is cooled by a cooling water system to liquefy into liquid ammonia; S3, deep cooling: Liquid ammonia is depressurized by the throttle valve and then enters the evaporator for evaporation and refrigeration; S4, coolant circulation: The refrigerant circulates in the refrigerant channel of the evaporator through an independent refrigerant circulation pipeline, and is transported to the refrigeration user end to provide cooling for the user after cooling. S5. Ammonia absorption: The evaporated ammonia enters the ammonia recovery reactor, where it comes into contact with and absorbs the ammonia compound lean solution from the generator, re-forming an ammonia compound rich solution; S6, GAX heat exchange: At the same time, the ammonia compound lean solution from the generator and the ammonia compound lean solution from the ammonia recovery reactor pass through the GAX heat exchanger for inter-wall heat exchange to achieve uniform heat release in the pipeline; S7, solution circulation: The ammonia-rich composite solution after heat exchange is transported by the solution pump and returned to the generator to complete the cycle.

9. A refrigeration method for a refrigeration system using a sodium thiocyanate-based absorption-type composite ammonia carrier as claimed in claim 2, characterized in that: The steps include: S1, thermal drive release: The composite ammonia carrier is introduced into the generator and then absorbs the refrigerant-ammonia to form an ammonia composite rich solution. The low-grade waste heat of 80-150°C from the thermal power plant is used as an external heat source to heat the ammonia in the ammonia composite rich solution to release ammonia gas, thereby obtaining an ammonia composite lean solution and ammonia gas. S2. Ammonia liquefaction: The ammonia gas released in step S1 is introduced into an ammonia liquefier, and the ammonia gas is cooled by a cooling water system to liquefy into liquid ammonia; S3, deep cooling: Liquid ammonia is depressurized by the throttle valve and then enters the evaporator for evaporation and refrigeration; S4, coolant circulation: The refrigerant circulates in the refrigerant channel of the evaporator through an independent refrigerant circulation pipeline, and is transported to the refrigeration user end to provide cooling for the user after cooling. S5. Ammonia absorption: The evaporated ammonia enters the ammonia recovery reactor, where it comes into contact with and absorbs the ammonia compound lean solution from the generator, re-forming an ammonia compound rich solution; S6, solution circulation: The ammonia-rich solution is transported by the solution pump and returned to the generator to complete the cycle.

10. An application of a sodium thiocyanate-based absorption-type composite ammonia carrier in a refrigeration system according to any one of claims 1 to 7, characterized in that: Used for industrial refrigeration and refrigeration or civil air conditioning and refrigeration.

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