A waste heat utilization system for a carbonate production plant

Abstract

The utility model relates to carbonate solvent production device, concretely is a kind of waste heat utilization system for carbonate production device, including carbonate device, second type lithium bromide absorption heat pump unit, expansion compressor unit and hot water circulation system, and heat exchanger is provided in rectifying column top of carbonate device, after heat exchange with column top material steam in heat exchanger, circulating water enters second type lithium bromide absorption heat pump unit, and circulating water after cooling flows back to heat exchanger;Second type lithium bromide absorption heat pump unit uses the heat of circulating water to produce steam exhaust gas, steam exhaust gas enters expansion compressor unit and produces low-pressure steam;High-pressure steam of outside is connected into expansion compressor unit and produces medium-pressure steam.The application recovers the vaporization latent heat of carbonate production device top by high efficiency, not only reduces the additional energy demand, also reduces tower top cooling water consumption, achieves the energy-saving purpose of rectification process.

Description

Technical Field

[0001] This utility model relates to a carbonate solvent production apparatus, specifically a waste heat utilization system for a carbonate production apparatus. Background Technology

[0002] Carbonates are important solvents for battery electrolytes, and numerous research reports on their production processes have been published in recent years. Among these, the reactive distillation process via transesterification is a major research and development direction. Its reaction conditions are mild, and the production process is pollution-free and environmentally friendly, making it one of the advanced methods for synthesizing carbonates. With industry development and the implementation of policies related to "carbon peaking" and "carbon neutrality," carbonate plants within the industry are not only continuously improving quality but also actively upgrading their technology to enhance energy efficiency. With increasingly sound energy management systems, the petrochemical industry is moving towards a green and low-carbon direction, making accelerated energy-saving upgrades and emission reductions imperative.

[0003] Carbonate production units typically include reactive distillation columns and purification distillation columns, which require a large amount of steam. The energy consumed in the distillation process accounts for a high proportion of the total energy consumption of the entire chemical enterprise. At the same time, the large amount of latent heat of vaporization at the top of the column requires a large amount of circulating cooling water.

[0004] Therefore, there is an urgent need to develop a waste heat utilization system to efficiently recover the latent heat of vaporization of the steam at the top of the tower. Utility Model Content

[0005] To address the problems mentioned above, this utility model provides a waste heat recovery system for carbonate production equipment. By efficiently recovering the latent heat of vaporization at the top of the carbonate production tower, it not only reduces the demand for external energy but also lowers the consumption of cooling water at the top of the tower, thereby achieving energy saving in the distillation process.

[0006] The first objective of this invention is to provide a waste heat recovery system for a carbonate production plant, comprising a carbonate plant, a second-type lithium bromide absorption heat pump unit, an expansion compressor unit, and a hot water circulation system, wherein:

[0007] The distillation column of the carbonate unit is equipped with a heat exchanger at the top. The circulating water of the hot water circulation system exchanges heat with the steam of the material at the top of the column in the heat exchanger and then enters the second type of lithium bromide absorption heat pump unit through the water supply pipe. The cooled circulating water flows back to the heat exchanger through the return water pipe.

[0008] The second type of lithium bromide absorption heat pump unit includes a gas-liquid separator. The heat of the circulating water is transferred to the gas-liquid separator, which heats the feed water in the gas-liquid separator to generate steam exhaust gas. The steam exhaust gas enters the expansion compressor unit.

[0009] The expansion compressor unit includes a steam compressor, a steam expander, and a reducer. Waste steam enters the steam compressor to produce low-pressure steam. The steam compressor is connected to the steam expander via the reducer, and high-pressure steam from the outside enters the steam expander to produce medium-pressure steam.

[0010] Furthermore, the expansion compressor unit also includes a first separator and a second separator. Steam exhaust gas enters the steam compressor and then passes through the first separator to produce low-pressure steam; high-pressure steam from the outside enters the steam expander and then passes through the second separator to produce medium-pressure steam.

[0011] Furthermore, it also includes a constant pressure water supply device, the inlet of which is connected to the pure water pipeline network, and the outlet of which is connected to the return water pipeline of the circulating water through a pipe.

[0012] Furthermore, the hot water circulation system also includes a temperature sensor, which detects and provides feedback on the temperature of the circulating water, keeping the temperature of the circulating water between 85-100℃.

[0013] Furthermore, the second type of lithium bromide absorption heat pump unit also includes an evaporator, an absorber, a generator, and a condenser. The circulating water flowing out of the heat exchanger enters the evaporator to absorb the heat of the circulating water. The cooled circulating water enters the generator to heat and concentrate the dilute lithium bromide solution in the generator. The cooled circulating water then flows back to the heat exchanger.

[0014] Furthermore, the condenser contains condensate, and a condensation pump is also installed on the condenser, through which the condensate is sprayed out.

[0015] Condensate is sprayed onto the outer surface of the heat exchange tubes of the evaporator by a condensation pump, generating water vapor that enters the absorber; the concentrated lithium bromide solution in the generator is sprayed into the absorber by a solution pump to absorb the water vapor generated by the evaporator.

[0016] Furthermore, the heat exchanger is a fully welded plate heat exchanger.

[0017] Furthermore, the steam compressor is a screw compressor.

[0018] The second objective of this invention is to provide a method for waste heat recovery from a carbonate production plant, comprising the following steps:

[0019] S1: A heat exchanger is installed at the top of the distillation column of the carbonate unit, using water as the heat exchange medium to exchange heat with the steam of the material at the top of the column. The high-temperature hot water obtained from the exchange enters the second type of lithium bromide absorption heat pump unit to produce steam exhaust gas; the cooled water flows back into the heat exchanger.

[0020] S2: Pass the exhaust steam into the steam compressor for further heating and pressurization to the required pressure to form low-pressure steam, and then connect it to the low-pressure steam pipeline network;

[0021] S3: Connect the steam expander to the steam compressor via a reducer, and introduce high-pressure steam from the outside into the steam expander to generate medium-pressure steam, which is then fed into the medium-pressure steam pipeline network. The medium-pressure steam pipeline network is connected to the carbonate unit to provide driving force for the carbonate unit.

[0022] Furthermore, the steam pressure generated by the steam compressor ranges from 0.2 to 1.0 MPaG, and the steam pressure generated by the steam expander ranges from 0.5 to 1.5 MPaG.

[0023] Preferably, the steam pressure generated by the steam compressor is in the range of 0.3 to 0.5 MPaG, and the steam pressure generated by the steam expander is in the range of 0.7 to 1.1 MPaG.

[0024] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0025] (1) This utility model adopts a hot water circulation system. Hot water is used to exchange heat with high-temperature materials through a heat exchanger as the driving heat source. The second type of lithium bromide absorption heat pump unit is used to produce 0.2~0.22MPaG primary steam. The primary steam is then pressurized to the required steam by a steam compressor and supplied to the low-pressure steam network. At the same time, the steam expander is driven by high-pressure steam. The high-pressure steam is adiabatically expanded to medium-pressure steam in the steam expander and then supplied to the medium-pressure steam network. This is to meet the various types of steam required by the carbonate production unit. The waste heat recovery system of this utility model returns the steam prepared by the waste heat recovery of the process liquid of the carbonate production unit to the steam network, which can minimize the total steam consumption and reduce the consumption of cooling circulating water in the unit.

[0026] (2) This utility model has a short cost recovery cycle. The second type of lithium bromide absorption heat pump unit can produce steam without consuming high-grade energy. The steam, after being pressurized by the expansion compressor unit, can be directly used by the device, thus saving primary energy input and achieving significant energy-saving effect. Moreover, the second type of lithium bromide absorption heat pump unit and the expansion compressor unit basically do not consume electricity. Furthermore, the second type of lithium bromide absorption heat pump unit uses lithium bromide solution, and there is no pollution or waste during operation, so there is no need for a fuel waste storage site. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the overall structure of the waste heat recovery system for the carbonate production apparatus of this utility model;

[0029] Figure 2 This is a flow chart of the waste heat utilization system for the carbonate production apparatus of this utility model.

[0030] Figure 3 This is a schematic diagram of the overall structure of the expansion compressor unit of the waste heat utilization system for the carbonate production apparatus of this utility model.

[0031] Figure 4 This is a schematic diagram of the second type of lithium bromide absorption heat pump unit for the waste heat utilization system of the carbonate production plant of this utility model.

[0032] Among them: 1-carbonate unit, 11-heat exchanger, 2-second type lithium bromide absorption heat pump unit, 21-gas-liquid separator, 22-evaporator, 23-absorber, 24-generator, 25-condenser, 26-solution pump, 27-solution heat exchanger, 3-expansion compressor unit, 31-steam compressor, 32-steam expander, 33-reducer, 34-first separator, 35-second separator, 4-hot water circulation system, 41-water supply pipe, 42-water return pipe, 5-constant pressure water supply device. Detailed Implementation

[0033] The technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0034] The following is in conjunction with the appendix Figure 1 To be continued Figure 4 The present invention will be described in detail with specific embodiments.

[0035] like Figure 1-4As shown, this utility model provides a waste heat recovery system for a carbonate production unit, including a carbonate unit 1, a second-type lithium bromide absorption heat pump unit 2, an expansion compressor unit 3, and a hot water circulation system 4. The carbonate unit 1 has a heat exchanger 11 installed at the top of its distillation column. The circulating water in the hot water circulation system 4 exchanges heat with the steam from the top of the column in the heat exchanger 11 and then enters the second-type lithium bromide absorption heat pump unit 2 through a water supply pipe 41. The water supply pipe 41 is connected to a hot water circulation pump, which supplies the circulating water absorbing the waste heat from the top of the column to the second-type lithium bromide absorption heat pump unit 2. Inside the second-type lithium bromide absorption heat pump unit 2, the circulating water undergoes heat exchange and heat conduction, resulting in a temperature reduction. The circulating water returns to the heat exchanger 11 through the return water pipe 42; the second type of lithium bromide absorption heat pump unit 2 includes a gas-liquid separator 21. The circulating water transfers the steam heat of the material at the top of the distillation column to the gas-liquid separator 21, which raises the temperature of the feed water in the gas-liquid separator 21 to generate steam exhaust gas. The temperature of the steam exhaust gas is higher than that of the circulating water, and the generated steam exhaust gas enters the expansion compressor unit 3; the second type of lithium bromide absorption heat pump unit 2 of this application uses waste heat as a driving source. Through internal heat exchange and heat conduction, it raises the low-temperature waste heat to medium and high temperatures and outputs higher-grade heat energy. The hot water releases heat in the second type of lithium bromide absorption heat pump unit 2 and then cools down. The return water pipe sends the low-temperature water back to the heat exchanger 11 to form a closed loop.

[0036] The expansion compressor unit 3 includes a steam compressor 31, a steam expander 32, and a reducer 33. Waste steam enters the steam compressor 31 and is compressed to produce low-pressure steam, which is then connected to the low-pressure steam network for the company's own use. The steam compressor 31 is connected to the steam expander 32 via the reducer. High-pressure steam from the outside enters the steam expander 32 to drive it, producing medium-pressure steam. This medium-pressure steam is connected to the medium-pressure steam network, which is connected to the carbonate unit 1, providing driving force for it. This system enables the utilization rate of waste heat at the top of the tower to reach approximately 80%, and increases the steam self-sufficiency rate by 50%. This system, through the combination of heat exchanger 11 and a second-type lithium bromide absorption heat pump unit 2, achieves a closed loop of waste heat recovery → temperature increase → reuse, significantly improving energy utilization efficiency.

[0037] This application employs a hot water circulation system. The circulating water exchanges heat with high-temperature materials through heat exchanger 11. A second-type lithium bromide absorption heat pump unit 2 is used to produce 0.2~0.22 MPaG primary steam. This primary steam is then pressurized to the required steam level by steam compressor 31 and supplied to the enterprise's low-pressure steam network. Simultaneously, a steam expander 32, driven by high-pressure steam, adiabatically expands the high-pressure steam to medium-pressure steam within the expander 32 before being supplied to the enterprise's medium-pressure steam network. This satisfies the various steam requirements of the carbonate production unit. By employing the waste heat recovery system of this invention, steam prepared from the waste heat of the process liquids in the carbonate production unit is returned to the steam network, minimizing the total steam consumption and reducing the consumption of cooling circulating water in the unit.

[0038] This utility model's waste heat recovery system can directly produce steam with a pressure of 0.2–1.5 MPaG, and can directly output steam with stable pressure and reliable quality (steam dryness can reach over 98%). Utilizing the sensible heat of high-pressure steam, it replaces the original desuperheating and pressure-reducing device. Unlike ordinary compressors that are directly driven by electricity, this utility model uses steam expansion to drive the process, significantly saving users on cable laying costs for high-power electrical equipment. Furthermore, this utility model does not consume high-grade energy; the second type of lithium bromide absorption heat pump unit 2 consumes only low-grade waste heat, without sacrificing high-grade energy. At the same time, the range of usable low-grade waste heat is wide, including waste heat from waste water, waste process gases, and waste process liquids.

[0039] Furthermore, the waste heat recovery system of this invention has low recovery costs. The second-type lithium bromide absorption heat pump unit 2 can produce steam without consuming high-grade energy. The steam, after being pressurized by the expansion compressor unit 3, can be directly used by the device, thus saving primary energy input and achieving significant energy-saving effects. Moreover, the second-type lithium bromide absorption heat pump unit 2 and the expansion compressor unit 3 consume virtually no electrical energy. The second-type lithium bromide absorption heat pump unit 2 uses lithium bromide solution, and there is no pollution or waste during operation, eliminating the need for fuel waste storage sites.

[0040] In a specific embodiment, see Figure 2 and Figure 3The expansion compressor unit 3 also includes a first separator 34 and a second separator 35. Exhaust steam enters the steam compressor 31, and then passes through the first separator 34 to produce low-pressure steam. The first separator 34 can efficiently remove liquid water. High-pressure steam from the outside enters the steam expander 32, and then passes through the second separator 35 to produce medium-pressure steam. Because the expanded steam pressure may flash due to the sudden pressure drop, a two-phase flow of gas and liquid may occur. The second separator 35 can quickly separate the liquid phase, outputting medium-pressure steam with a dryness of ≥99%, which is then supplied to other process units. This application, through the configuration of the first separator 34 and the second separator 35, increases the steam dryness by over 99%, eliminates the heat exchange efficiency reduction caused by liquid phase carryover, and improves the overall system thermal efficiency by 12%.

[0041] This application connects the steam compressor 31 and the steam expander 32 via a speed reducer 33. The steam compressor 31 is driven by the work generated by the expansion of high-pressure steam, which reduces the consumption of external power supply and ensures efficient power transmission. At the same time, the speed reducer 33 can adjust the speed of the steam compressor 31 and the steam expander 32 to ensure that the two work in coordination. Through the linkage of the steam compressor 31 and the expansion compressor 32, the separated dry steam is redistributed to users with different pressure levels, achieving precise matching of energy quality.

[0042] Specifically, this embodiment also includes a constant pressure water supply device 5. The inlet of the constant pressure water supply device 5 is connected to the pure water pipeline network, and the outlet of the constant pressure water supply device 5 is connected to the return water pipeline 42 of the circulating water through a pipeline. Because hot water will be lost during the operation of the hot water circulation system 4 (such as volume loss of circulating water due to evaporation and leakage), it is necessary to replenish water through the constant pressure water supply device 5 to ensure the stable operation of the waste heat recovery system; at the same time, pure water supply can avoid the introduction of Ca²⁺, Mg²⁺ and other ions by industrial water supply, which can lead to scale formation in the heat exchanger and contamination of lithium bromide solution.

[0043] Specifically, the hot water circulation system 4 also includes a temperature sensor, which detects and provides feedback on the temperature of the circulating water, ensuring that the temperature of the circulating water entering the lithium bromide unit is controlled at 85-100℃, preferably 90-100℃. In this design, the outlet water temperature is controlled by adjusting the amount of circulating water used, and the temperature difference between the outlet and return water is generally set at 10℃.

[0044] For details, please refer to Figure 2 and Figure 4 In this embodiment of the application, the second type of lithium bromide absorption heat pump unit 2 also includes an evaporator 22, an absorber 23, a generator 24 and a condenser 25. The circulating water flowing out of the heat exchanger 11 enters the evaporator 22 to absorb the heat of the circulating water. After the initial cooling, the circulating water enters the generator 24 to heat and concentrate the dilute lithium bromide solution in the generator 24. The circulating water that is cooled again flows back to the heat exchanger 11.

[0045] Furthermore, the condenser 25 contains condensate, which is sprayed onto the outer surface of the heat exchange tubes of the evaporator 22 by a condensation pump, generating water vapor that enters the absorber 23. The concentrated lithium bromide solution in the generator 24 is sprayed into the absorber 23 by a solution pump 26, absorbing the water vapor generated by the evaporator 22 and releasing a large amount of condensation heat, which heats the feedwater in the gas-liquid separator 21. The concentrated solution (concentrated lithium bromide solution) in the generator 24 and the dilute solution (dilute lithium bromide solution) in the absorber 23 exchange heat through the solution heat exchanger 27. The second type of lithium bromide absorption heat pump unit 2 of this application has fewer moving parts, is simple and reliable to operate, has low maintenance costs, and a high degree of automatic control.

[0046] The working principle of the second type of lithium bromide absorption heat pump unit in this utility model is as follows:

[0047] (a) Extraction of waste heat

[0048] Inside the vacuum evaporator 22, the principle that the boiling point of water decreases under negative pressure is utilized. The condensed water from the condenser 25 is sprayed onto the outer surface of the heat exchange tubes of the evaporator 22. The condensed water absorbs the heat from the low-temperature waste heat flowing inside the heat exchange tubes, evaporates and vaporizes to generate steam, which enters the absorber 23 to complete the process of extracting waste heat.

[0049] (ii): Transfer of waste heat

[0050] Inside the absorber 23, utilizing the water absorption and heat release properties of the concentrated lithium bromide solution, the concentrated lithium bromide solution from the generator 24 is distributed outside the heat exchange tubes of the absorber 23, absorbing water vapor from the evaporator 22 and releasing a large amount of condensation heat. The condensation heat is used to heat the feed water in the heat exchange tubes of the gas-liquid separator 21 that needs to be heated, thus realizing the transfer of heat from the low-temperature heat source to the heated heat medium. At the same time, the lithium bromide solution changes from concentrated to dilute and no longer has water absorption properties, so it needs to be concentrated and recycled.

[0051] (III): Concentration of working fluid

[0052] The heat source water from the evaporator 22 enters the generator 24 to heat and concentrate the dilute lithium bromide solution from the absorber 23. The concentrated solution then returns to the absorber 23 to continue absorbing water vapor to heat the feed water. The refrigerant vapor generated from the solution concentration goes to the condenser 25.

[0053] (iv): Cooling water cooling

[0054] Inside the condenser 25, the low-temperature cooling water causes the refrigerant vapor to condense and release heat. The vapor condenses into condensate and is transported to the evaporator 22 to continue circulating evaporation. The cooling water is heated and then enters the cooling tower to cool down, and is recycled.

[0055] In some embodiments, heat exchanger 11 is a fully welded plate heat exchanger. In the waste heat recovery system of the carbonate production unit, the recovery efficiency of the waste heat from the top vapor phase of the distillation column directly depends on the performance of heat exchanger 11. Traditional shell-and-tube heat exchangers are difficult to meet the requirements of high recovery rates due to problems such as low heat transfer efficiency, easy fouling, and large size. Plate heat exchangers have a larger heat exchange area per unit volume, a compact structure, and a small equipment footprint, which can significantly improve heat exchange efficiency and fully recover the waste heat from the top vapor phase of the column.

[0056] In some embodiments, the steam compressor 31 is a screw compressor. Screw compressors employ a rotary motion design, which, unlike reciprocating components, results in less overall vibration and lower noise; their operational stability is superior to that of piston compressors, making them suitable for long-term continuous operation.

[0057] This utility model also provides a method for waste heat recovery from a carbonate production plant, comprising the following steps:

[0058] S1: A heat exchanger is installed at the top of the distillation column of the carbonate unit, using water as the heat exchange medium to exchange heat with the steam of the material at the top of the column. The high-temperature hot water obtained from the exchange enters the second type of lithium bromide absorption heat pump unit to produce steam exhaust gas; the cooled water flows back into the heat exchanger.

[0059] S2: Pass the exhaust steam into the steam compressor for further heating and pressurization to the required pressure to form low-pressure steam, and then connect it to the low-pressure steam pipeline network;

[0060] S3: Connect the steam expander to the steam compressor via a reducer, and introduce high-pressure steam from the outside into the steam expander to generate medium-pressure steam, which is then fed into the medium-pressure steam pipeline network. The medium-pressure steam pipeline network is connected to the carbonate unit to provide driving force for the carbonate unit.

[0061] Furthermore, the steam pressure generated by the steam compressor ranges from 0.2 to 1.0 MPaG, and the steam pressure generated by the steam expander ranges from 0.5 to 1.5 MPaG.

[0062] Preferably, the steam pressure generated by the steam compressor is in the range of 0.3 to 0.5 MPaG, and the steam pressure generated by the steam expander is in the range of 0.7 to 1.1 MPaG.

[0063] The effects achieved by the recycling method of this utility model are discussed below using two specific embodiments.

[0064] Example 1

[0065] A method for waste heat recovery from a carbonate production plant includes the following steps:

[0066] S1: The crude carbonate product is fed into a distillation column for refining. The top temperature of the distillation column is 100℃. A heat exchanger 11 is installed at the top of the distillation column of the carbonate unit 1. Water is used as the heat exchange medium to exchange heat with the steam of the material at the top of the column. The outlet temperature of the high-temperature hot water obtained by the exchange is 97℃. The high-temperature hot water enters the second type of lithium bromide absorption heat pump unit 2 to produce exhaust steam. The steam pressure of the exhaust steam is 0.21 MPaG. The circulating water is cooled to 87℃ and then flows back into the heat exchanger 11.

[0067] S2: The 0.21 MPaG steam exhaust gas is fed into the steam compressor 31 for further heating and pressurization to 0.45 MPaG, forming low-pressure steam, which is then fed into the low-pressure steam pipeline network;

[0068] S3: The steam expander 32 is connected to the steam compressor 31 through the reducer 33, and the high-pressure steam (steam pressure of 2.1 MPaG) from the outside is introduced into the steam expander 32 to generate medium-pressure steam. The steam pressure of the medium-pressure steam obtained after expansion is 0.9 MPaG, which is then connected to the medium-pressure steam pipeline network. The medium-pressure steam pipeline network is connected to the carbonate device 1 to provide driving force for the carbonate device 1.

[0069] Example 2

[0070] A method for waste heat recovery from a carbonate production plant includes the following steps:

[0071] S1: The crude carbonate product is fed into a distillation column for refining. The top temperature of the distillation column is 100℃. A heat exchanger 11 is installed at the top of the distillation column of the carbonate unit 1. Water is used as the heat exchange medium to exchange heat with the steam of the material at the top of the column. The outlet temperature of the high-temperature hot water obtained by the exchange is 100℃. The high-temperature hot water enters the second type of lithium bromide absorption heat pump unit 2 to produce exhaust steam. The steam pressure of the exhaust steam is 0.22 MPaG. The circulating water is cooled to 90℃ and then flows back into the heat exchanger 11.

[0072] S2: The 0.22 MPaG steam exhaust gas is fed into the steam compressor 31 for further heating and pressurization to 0.48 MPaG, forming low-pressure steam, which is then fed into the low-pressure steam pipeline network;

[0073] S3: The steam expander 32 is connected to the steam compressor 31 through the reducer 33, and the high-pressure steam (steam pressure of 2.2 MPaG) from the outside is introduced into the steam expander 32 to generate medium-pressure steam. The steam pressure of the medium-pressure steam obtained after expansion is 1.0 MPaG, and it is connected to the medium-pressure steam pipeline network. The medium-pressure steam pipeline network is connected to the carbonate device 1 to provide driving force for the carbonate device 1.

[0074] The specific data for Examples 1 and 2 are shown in the table below.

[0075] Comparison items Example 1 Example 2 Hot water recovery volume (t / h) 600 500 Waste heat recovery (GJ) 25.080 20.900 Waste heat recovery rate (%) 96.5 96.4 Steam production (t / h) 5.450 4.542 Cost savings (RMB / hour) 1386.3 1135.5

[0076] As can be seen from Examples 1 and 2, the method of this utility model can fully recover the waste heat of the device, reduce the cooling water load of the original device, and achieve a waste heat recovery rate of over 95%. At the same time, a large amount of low-pressure steam is generated and enters the pipeline network, which can save approximately 16 million yuan per year.

[0077] In summary, this waste heat recovery method recovers the energy that was wasted by the circulating water in the distillation column. With the supplement of a small amount of energy from the second type of lithium bromide heat pump unit and the compression-expansion unit, this part of the heat is converted into the steam heat source required by the distillation column. This saves the consumption of heat steam and reduces the use of cold circulating water.

[0078] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the substance and scope of the present invention. Various modifications made by those skilled in the art to the above embodiments after reading this specification are all within the scope of protection of the present invention.

Claims

1. A waste heat recovery system for a carbonate production plant, characterized in that, This includes a carbonate unit, a Class II lithium bromide absorption heat pump unit, an expansion compressor unit, and a hot water circulation system, wherein: The distillation column of the carbonate unit is equipped with a heat exchanger at the top of the column. The circulating water of the hot water circulation system exchanges heat with the steam of the material at the top of the column in the heat exchanger and then enters the second type of lithium bromide absorption heat pump unit through the water supply pipe. The cooled circulating water flows back to the heat exchanger through the return water pipe. The second type of lithium bromide absorption heat pump unit includes a gas-liquid separator. The heat of the circulating water is transferred to the gas-liquid separator, which heats the feed water in the gas-liquid separator to generate steam exhaust gas. The steam exhaust gas enters the expansion compressor unit. The expansion compressor unit includes a steam compressor, a steam expander, and a reducer. Waste steam enters the steam compressor to generate low-pressure steam. The steam compressor is connected to the steam expander via the reducer, and high-pressure steam from the outside enters the steam expander to generate medium-pressure steam.

2. The waste heat recovery system for a carbonate production unit according to claim 1, characterized in that, The expansion compressor unit also includes a first separator and a second separator. Waste steam enters the steam compressor and is then separated by the first separator to produce low-pressure steam. High-pressure steam from the outside enters the steam expander and is then separated by the second separator to produce medium-pressure steam.

3. The waste heat recovery system for a carbonate production unit according to claim 1, characterized in that, It also includes a constant pressure water supply device, the inlet of which is connected to the pure water pipeline network, and the outlet of which is connected to the return water pipeline of the circulating water through a pipeline.

4. The waste heat recovery system for a carbonate production unit according to claim 1, characterized in that, The hot water circulation system also includes a temperature sensor, which detects and provides feedback on the temperature of the circulating water, thereby controlling the temperature of the circulating water between 85-100℃.

5. The waste heat recovery system for a carbonate production unit according to claim 1, characterized in that, The second type of lithium bromide absorption heat pump unit also includes an evaporator, an absorber, a generator, and a condenser. The circulating water flowing out of the heat exchanger enters the evaporator to absorb the heat of the circulating water. The cooled circulating water enters the generator to heat and concentrate the dilute lithium bromide solution in the generator. The cooled circulating water flows back to the heat exchanger.

6. The waste heat recovery system for a carbonate production unit according to claim 5, characterized in that, The condenser contains condensate, and a condensation pump is also installed on the condenser, through which the condensate is sprayed out.

7. The waste heat recovery system for a carbonate production unit according to claim 1, characterized in that, The heat exchanger is a fully welded plate heat exchanger.

8. The waste heat recovery system for a carbonate production unit according to claim 1, characterized in that, The steam compressor is a screw compressor.

9. The waste heat recovery system for a carbonate production apparatus according to claim 1, characterized in that, The steam compressor produces steam with a pressure range of 0.3 to 0.5 MPaG, and the steam expander produces steam with a pressure range of 0.7 to 1.1 MPaG.

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