Desulfurization slurry waste heat recovery system and method based on multistage flash evaporation and open type heat pump

Abstract

The invention provides a desulfurization slurry waste heat recovery system and method based on multistage flash evaporation and an open heat pump. A solution heater is used for heating a dilute solution through high-temperature flue gas; the desulfurization tower is used for heat and mass transfer between slurry and high-temperature flue gas; flash evaporation cavities of the multiple stages of flash evaporation absorbers are sequentially arranged from high pressure to low pressure, and absorption cavities of the multiple stages of flash evaporation absorbers are sequentially arranged from low pressure to high pressure; the flash condenser is used for flash concentration and cooling of the dilute solution; the solution heat exchanger is used for heat exchange between a dilute solution and a concentrated solution; the solution water heat exchanger is used for heat exchange between a concentrated solution and heat supply network return water; the solution heater, the multi-stage flash absorber, the flash condenser, the solution heat exchanger and the solution water heat exchanger form an open heat pump system, and high-temperature flue gas is used as driving force to recover waste heat. By means of multi-stage flash evaporation and utilization of the solution absorption capacity, the desulfurization slurry waste heat recovery efficiency is greatly improved, gradient utilization is conducted on high-temperature flue gas, heat energy is fully recovered, and the operation cost is reduced through an open type heat pump.

Description

Technical Field

[0001] The present invention relates to the technical field of energy recovery and utilization, and in particular to a desulfurization slurry waste heat recovery system and method based on multi-stage flash evaporation and open heat pump. Background Art

[0002] In industrial production processes such as coal-fired power plants and steel mills, flue gas desulfurization is a key step in achieving environmental protection requirements. The desulfurization tower slurry contains a large amount of waste heat resources, but this part of waste heat usually exists in the form of low-grade thermal energy. Direct emission not only wastes energy, but also causes environmental thermal pollution. In the existing technology, the waste heat recovery method is relatively simple, usually using direct heat exchange or single-stage flash evaporation, and the recovery efficiency is low.

[0003] In addition, the existing heat pump system is mainly a closed heat pump (such as an absorption heat pump and an electric compression heat pump). Although the efficiency is high, the layout flexibility is poor and the cost is high. Especially in the process of recovering the waste heat of the desulfurization tower slurry, the high dependence of the closed heat pump on external energy further limits its application. The low-pressure steam after the flash evaporation of the slurry can be recycled using an open heat pump (CN117928129A). Compared with the closed heat pump system, the layout of the open heat pump is more flexible, more adaptable and less expensive. However, the open heat pump still requires an external heat source as a driving energy source. In addition, the existing system form does not fully utilize the absorption capacity of the solution, resulting in energy efficiency waste. Therefore, there is an urgent need for an efficient, flexible and low-cost desulfurization slurry waste heat recovery system that can make full use of the heat energy in the slurry and flue gas, realize energy cascade utilization, and improve the overall energy efficiency of the system. Summary of the invention

[0004] The purpose of the present invention is to provide a desulfurization slurry waste heat recovery system and method based on multi-stage flash evaporation and open heat pump. By combining multi-stage flash evaporation absorption technology with an open heat pump, the heat in the desulfurization slurry and high-temperature flue gas can be fully recovered, the cascade utilization of heat can be achieved, the energy utilization efficiency of the system can be significantly improved, and the construction and operation costs of the system can be reduced.

[0005] According to one object of the present invention, the present invention provides a desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump, comprising:

[0006] A solution heater is used to heat the dilute solution by means of high temperature flue gas;

[0007] Desulfurization tower, used for heat and mass exchange between slurry and high-temperature flue gas;

[0008] The multi-stage flash absorber comprises a plurality of flash chambers and absorption chambers, wherein the flash chambers are arranged in sequence from high to low pressure and are used for multi-stage flash cooling of the slurry; the absorption chambers are arranged in sequence from low to high pressure and are used for multi-stage absorption of water vapor flashed from the slurry by the solution;

[0009] Flash condenser, used for flash concentration and cooling of dilute solutions;

[0010] Solution heat exchanger, used for heat exchange between dilute solution and concentrated solution;

[0011] Solution water heat exchanger, used for heat exchange between concentrated solution and heat network return water;

[0012] The solution heater, solution heat exchanger, flash condenser, solution water heat exchanger, and multi-stage flash absorber constitute an open heat pump system, which uses high-temperature flue gas as a driving force to recover waste heat;

[0013] The circulation piping system is used for the circulation of slurry and solution between the above components.

[0014] Furthermore, the high-temperature flue gas passes through the solution heater and the desulfurization tower in sequence, completes the heating of the dilute solution and the heat and mass exchange of the slurry, and is then discharged through a chimney.

[0015] Furthermore, the flash chambers of the multi-stage flash absorber are connected in series, and the slurry passes through the flash chambers of each stage in order from high to low pressure, and is cooled down step by step and releases water vapor.

[0016] Furthermore, the absorption chambers of the multi-stage flash absorber are connected in series, and the concentrated solution passes through the absorption chambers of each stage in order from low to high pressure to absorb the water vapor flashed from the slurry.

[0017] Furthermore, the absorption chambers of the multi-stage flash absorber adopt a parallel structure, and the concentrated solution enters the absorption chambers of each stage at the same time, absorbs the water vapor flashed from the slurry, and then flows out to become a dilute solution.

[0018] Furthermore, the solution water heat exchanger is used for heat exchange between concentrated solution and heat network return water. After heat exchange, the heat network return water enters the flash condenser, exchanges heat with the condensed water vapor, and then flows out as supply water.

[0019] Furthermore, the flash condenser is used for flash concentration of dilute solutions, and the generated water vapor releases heat through condensation for heating the heat network.

[0020] Furthermore, the open heat pump utilizes high-temperature flue gas as a driving force to recover the waste heat of low-pressure steam flashed from the slurry, and after further increasing the waste heat, transmits it to the heating network or other external heating systems.

[0021] According to another object of the present invention, the present invention provides a method for using the above-mentioned desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump, comprising the following steps:

[0022] The high-temperature flue gas enters the solution heater and desulfurization tower in sequence, heating the dilute solution and exchanging heat and mass with the slurry;

[0023] After the slurry is heated in the desulfurization tower, it enters the flash chamber of the multi-stage flash absorber in sequence, flashes to cool down step by step and releases water vapor;

[0024] The low-pressure steam flashed from the slurry enters the open heat pump to complete waste heat recovery;

[0025] The concentrated solution passes through the absorption chambers of each stage of the multi-stage flash absorber in sequence, absorbs the water vapor flashed from the slurry, and is converted into a dilute solution;

[0026] The dilute solution is heated by the solution heat exchanger and then enters the solution heater to complete the cycle;

[0027] After the concentrated solution passes through the solution water heat exchanger and the heat network return water, the heat network return water enters the flash condenser for heat exchange and temperature rise, and is output as supply water.

[0028] Furthermore, the multi-stage flash absorber is designed in a series mode or a parallel mode according to the operating conditions. In the series mode, the slurry and the solution pass through the flash chambers and the absorption chambers of each stage in sequence; in the parallel mode, the concentrated solution enters the absorption chambers of each stage at the same time, reducing the complexity of the system pipelines and the operating costs.

[0029] The technical solution of the present invention greatly improves the waste heat recovery efficiency of desulfurization slurry through the use of multi-stage flash evaporation technology and solution absorption capacity, and utilizes high-temperature flue gas in a cascade manner to fully recover its heat energy. The open heat pump has a flexible design and reduces the equipment cost and operating cost of the system. The system design is flexible and suitable for various types of desulfurization towers and high-temperature flue gas conditions, reducing the thermal pollution to the environment caused by direct waste heat emission and improving energy utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0032] Figure 2 FIG. 4 is another structural schematic diagram of an embodiment of the present invention.

[0033] In the figure: 1. Solution heater; 2. Flash condenser; 3. Solution heat exchanger; 4. Solution water heat exchanger; 5. Multi-stage flash absorber; 6. Desulfurization tower. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0036] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] Example 1

[0038] like Figure 1 and Figure 2 As shown,

[0039] A desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump, comprising:

[0040] A solution heater 1, used for heating the dilute solution by means of high temperature flue gas;

[0041] Desulfurization tower 6, used for heat and mass exchange between slurry and high-temperature flue gas;

[0042] The multi-stage flash absorber 5 comprises a plurality of flash chambers and absorption chambers. The flash chambers are arranged in order from high to low pressure, and are used for multi-stage flash cooling of the slurry; the absorption chambers are arranged in order from low to high pressure, and are used for multi-stage solution absorption of water vapor flashed from the slurry;

[0043] Flash condenser 2, used for flash concentration and cooling of dilute solutions

[0044] Solution heat exchanger 3, used for heat exchange between dilute solution and concentrated solution;

[0045] Solution water heat exchanger 4, used for heat exchange between concentrated solution and heat network return water;

[0046] The solution heater 1, the flash condenser 2, the solution heat exchanger 3, the solution water heat exchanger 4, and the multi-stage flash absorber 5 constitute an open heat pump system, which uses high-temperature flue gas as a driving force to recover waste heat;

[0047] Circulation piping system, used for circulation of slurry and solution between various components.

[0048] The high-temperature flue gas passes through the solution heater 1 and the desulfurization tower 6 in sequence, completes the heating of the dilute solution and the heat and mass exchange of the slurry, and is then discharged through the chimney.

[0049] The flash chambers of the multi-stage flash absorber 5 are connected in series, and the slurry passes through the flash chambers of each stage in order from high to low pressure.

[0050] The absorption chambers of the multi-stage flash absorber 5 are connected in series, and the concentrated solution passes through the absorption chambers of each stage in order from low to high pressure to absorb the water vapor flashed from the slurry.

[0051] like Figure 2 As shown, in this embodiment, the absorption chambers of the multi-stage flash absorber 5 can also adopt a parallel structure, and the concentrated solution enters the absorption chambers of each stage at the same time, absorbs the water vapor flashed from the slurry, and then flows out to become a dilute solution.

[0052] The solution water heat exchanger 4 is used for heat exchange between concentrated solution and heat network return water. After heat exchange, the heat network return water enters the condenser part of the flash condenser, condenses and releases heat with water vapor, and then flows out as supply water.

[0053] The flash condenser is used for flash concentration of dilute solutions, and the generated water vapor is condensed in the condenser part to release heat.

[0054] The open heat pump uses high-temperature flue gas as a driving force to recover the waste heat of low-pressure steam flashed from the slurry, further increasing the waste heat for use in the heating network or other external heating systems.

[0055] The above-mentioned desulfurization slurry waste heat recovery method based on multi-stage flash evaporation and open heat pump comprises the following steps:

[0056] 1. The high-temperature flue gas first enters the solution heater 1, heats the dilute solution and then enters the desulfurization tower 6;

[0057] 2. The slurry is heated up after heat exchange with the high-temperature flue gas in the desulfurization tower 6, and then enters the flash chambers of each stage of the multi-stage flash absorber 5 in sequence, and is cooled down by flash evaporation step by step;

[0058] 3. The low-pressure steam flashed from the slurry enters the open heat pump for waste heat recovery;

[0059] 4. The concentrated solution passes through the absorption chambers of each stage of the multi-stage flash absorber 5, absorbs the water vapor flashed from the slurry, and becomes a dilute solution;

[0060] 5. The dilute solution is heated by the solution heat exchanger 3 and then enters the solution heater 1 to complete the cycle;

[0061] 6. The concentrated solution is cooled by heat exchange with the return water of the heating network through the solution water heat exchanger 4. The return water of the heating network is heated by the flash condenser 2 and then flows out to be provided to the heat users as supply water.

[0062] The present invention adopts a series mode or a parallel mode to design a multi-stage flash absorber. In the series mode, the slurry and the solution pass through the flash chambers and the absorption chambers of each stage in sequence; in the parallel mode, the concentrated solution enters the absorption chambers of each stage at the same time, reducing the complexity of the system pipelines and the operating cost.

[0063] In this embodiment, the high-temperature flue gas in front of the desulfurization tower is used as the heat source for solution heating and concentration, and the waste heat of the desulfurized slurry is recovered at the same time, realizing the cascade utilization of flue gas heat and improving energy utilization efficiency. In addition, this embodiment adopts the form of multi-stage flash absorption to realize slurry flash evaporation, making full use of the absorption capacity of the concentrated solution and significantly improving the waste heat recovery efficiency.

[0064] At the same time, if Figure 2 As shown, in this embodiment, the concentrated solution flowing out of the solution water heat exchanger 4 does not pass through the absorption chambers of each stage of the multi-stage flash absorber 5 in sequence, but enters the absorption chambers of each stage of the multi-stage flash absorber 5 in parallel. Compared with the above technical solution, the complexity of the concentrated solution pipeline can be reduced and the system cost can be reduced.

[0065] In this embodiment, the following key steps are included:

[0066] Cascade utilization of high-temperature flue gas: The high-temperature flue gas first enters the solution heater 1 to heat the solution. After that, the flue gas enters the desulfurization tower 6 to exchange heat and mass with the desulfurized slurry, and is discharged through the chimney after the waste heat is utilized.

[0067] Desulfurization slurry flash cooling and circulation:

[0068] The slurry is heated after heat exchange with flue gas in the desulfurization tower 6, and then enters the multi-stage flash absorber 5, passing through each flash chamber in order from high to low pressure, releasing water vapor and cooling down step by step. The cooled slurry returns to the desulfurization tower 6 to continue the cycle.

[0069] Solution absorption cycle:

[0070] The dilute solution heated by the high-temperature flue gas through the solution heater 1 enters the flash condenser 2, and becomes a concentrated solution after being concentrated and cooled in the flash chamber. The concentrated solution enters the multi-stage flash absorber 5 after being cooled through the solution heat exchanger 3 and the solution water heat exchanger 4. The concentrated solution passes through the absorption chambers of each level in order from low to high pressure, absorbs the water vapor generated by the flash evaporation of the slurry, becomes a dilute solution, and then flows out, and finally returns to the solution heater to complete the cycle.

[0071] Open heat pump drive:

[0072] High-temperature flue gas is used as the driving force of the open heat pump, and the low-pressure steam waste heat generated by the flash evaporation of the slurry is recovered through the open heat pump system. Compared with the traditional closed heat pump, the design of the open heat pump is more flexible, more adaptable, and has lower cost. Multi-stage flash evaporation parallel and series design:

[0073] Series mode: The slurry passes through multiple flash chambers in sequence, and the concentrated solution passes through multiple absorption chambers in sequence.

[0074] Parallel mode: The concentrated solution enters each level of absorption cavity in parallel, effectively reducing pipeline complexity and system cost.

[0075] Specific process:

[0076] Heat exchange process between high-temperature flue gas and desulfurization slurry:

[0077] The high-temperature flue gas first enters the solution heater 1, heats the dilute solution and then cools it down. It then enters the desulfurization tower 6, exchanges heat and mass with the desulfurized slurry and is discharged through the chimney. The slurry increases in temperature after heat exchange with the flue gas and enters the multi-stage flash absorber 5 for flash cooling.

[0078] Slurry circulation and multi-stage flash evaporation process:

[0079] The heated slurry passes through the flash chambers of the multi-stage flash absorber 5 in order of working pressure from high to low, releasing water vapor and cooling down step by step. The slurry flowing out of the lowest pressure flash chamber is significantly cooled and then returns to the desulfurization tower 6, completing the slurry circulation.

[0080] Solution circulation process:

[0081] The dilute solution enters the flash condenser 2 and is cooled by flash evaporation to become a concentrated solution.

[0082] After the concentrated solution is further cooled by the solution heat exchanger 3 and the solution water heat exchanger 4, it enters the absorption chambers of each stage of the multi-stage flash absorber 5, absorbs the steam flashed by the slurry, and becomes a dilute solution and flows out.

[0083] The dilute solution enters solution heater 1 again to complete the cycle.

[0084] Waste heat heating process:

[0085] After the return water from the heat network is heated by heat exchange with the solution in the solution water heat exchanger 4, it enters the condenser part of the flash condenser 2, condenses and releases heat with the water vapor, and then flows out as water supply for heat users.

[0086] The present invention has high energy efficiency. Through the use of multi-stage flash evaporation technology and solution absorption capacity, the waste heat recovery efficiency of desulfurization slurry is greatly improved. The high-temperature flue gas is utilized in stages to fully recover its heat energy. The open heat pump has a flexible design, which reduces the equipment cost and operating cost of the system. The parallel mode reduces the complexity of the concentrated solution pipeline, further saving investment. The system design is flexible, and parallel or series mode can be selected according to different working conditions. It is suitable for various types of desulfurization towers and high-temperature flue gas conditions. It reduces the thermal pollution to the environment caused by direct discharge of waste heat and improves energy utilization.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump, characterized in that: include: A solution heater is used to heat the dilute solution by means of high temperature flue gas; Desulfurization tower, used for heat and mass exchange between slurry and high-temperature flue gas; The multi-stage flash absorber comprises a plurality of flash chambers and absorption chambers, wherein the flash chambers are arranged in sequence from high to low pressure and are used for multi-stage flash cooling of the slurry; the absorption chambers are arranged in sequence from low to high pressure and are used for multi-stage absorption of water vapor flashed from the slurry by the solution; Flash condenser, used for flash concentration and cooling of dilute solutions; Solution heat exchanger, used for heat exchange between dilute solution and concentrated solution; Solution water heat exchanger, used for heat exchange between concentrated solution and heat network return water; The solution heater, the multi-stage flash absorber, the flash condenser, the solution heat exchanger, and the solution-water heat exchanger constitute an open heat pump, which utilizes high-temperature flue gas as a driving force to recover waste heat.

2. The desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump according to claim 1 is characterized in that: The high-temperature flue gas passes through the solution heater and the desulfurization tower in sequence, completes the heating of the dilute solution and the heat and mass exchange of the slurry, and is then discharged through a chimney.

3. The desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump according to claim 1 is characterized in that: The flash chambers of the multi-stage flash absorber are connected in series, and the slurry passes through the flash chambers of each stage in order from high to low pressure, and is cooled down step by step and releases water vapor.

4. The desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump according to claim 1 is characterized in that: The absorption chambers of the multi-stage flash absorber are connected in series, and the concentrated solution passes through the absorption chambers of each stage in order from low to high pressure to absorb the water vapor flashed from the slurry.

5. The desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump according to claim 1 is characterized in that: The absorption chambers of the multi-stage flash absorber adopt a parallel structure, and the concentrated solution enters the absorption chambers of each stage at the same time, absorbs the water vapor flashed from the slurry, and then flows out to become a dilute solution.

6. The desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump according to claim 1 is characterized in that: The solution water heat exchanger is used for heat exchange between concentrated solution and heat network return water. After heat exchange, the heat network return water enters the flash condenser, exchanges heat with condensed water vapor, and then flows out as supply water.

7. The desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump according to claim 1 is characterized in that: The flash condenser is used for flash concentration of dilute solutions, and the generated water vapor releases heat through condensation for heating the heat network.

8. The desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump according to claim 1 is characterized in that: The open heat pump utilizes high-temperature flue gas as a driving force to recover the waste heat of low-pressure steam flashed from the slurry, and after further increasing the waste heat, transmits it to the heating network or other external heating systems.

9. The method for using the desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump according to claim 1, characterized in that: The following steps are involved: The high-temperature flue gas enters the solution heater and desulfurization tower in sequence, heating the dilute solution and exchanging heat and mass with the slurry; After the slurry is heated in the desulfurization tower, it enters the flash chamber of the multi-stage flash absorber in sequence, flashes to cool down step by step and releases water vapor; The low-pressure steam flashed from the slurry enters the open heat pump to complete waste heat recovery; The concentrated solution passes through the absorption chambers of each stage of the multi-stage flash absorber in sequence, absorbs the water vapor flashed from the slurry, and is converted into a dilute solution; The dilute solution is heated by the solution heat exchanger and then enters the solution heater to complete the cycle; After the concentrated solution passes through the solution water heat exchanger and the heat network return water, the heat network return water enters the flash condenser for heat exchange and temperature rise, and is output as supply water.

10. The method for using the desulfurization slurry waste heat recovery system based on multi-stage flash evaporation and open heat pump according to claim 9, characterized in that: The multi-stage flash absorber is designed in a series mode or a parallel mode according to the working conditions. In the series mode, the slurry and the solution pass through the flash chambers and the absorption chambers of each stage in sequence; in the parallel mode, the concentrated solution enters the absorption chambers of each stage at the same time, reducing the complexity of the system pipelines and the operating costs.

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