Mechanical thermal compression energy-saving device for efficiently recycling low-grade waste heat of steam

Abstract

The utility model discloses a mechanical thermal compression energy-saving device for efficiently recycling low-grade waste heat of steam, and aims to solve the problems of low utilization rate of heat energy of secondary steam, serious energy waste and high consumption of cooling water in the traditional evaporation and concentration process. According to the device, secondary steam separated by the evaporator is compressed through a mechanical vapor recompression (MVR) technology, the temperature, the pressure and the enthalpy of the secondary steam are increased, the secondary steam can serve as a high-quality heat source to enter a heating chamber of the evaporator again for condensation and heat release, and therefore efficient recycling of latent heat of the secondary steam is achieved. Meanwhile, heat released by the condensate water is used for preheating the brine, so that a secondary steam cooling water system is omitted, and the consumption of cooling water is reduced. The energy utilization efficiency is remarkably improved, the operation cost is reduced, and the device has the remarkable effects of environmental protection and emission reduction, is suitable for the industrial fields needing evaporation and concentration such as chemical industry, pharmacy and food, and has wide application prospects and market potential.

Description

Technical Field

[0001] The utility model relates to the technical field of energy saving, and in particular to a mechanical heat compression energy saving device for efficiently recovering and reusing low-grade waste heat of steam. Background Art

[0002] In the traditional evaporation and concentration process, the secondary steam separated from the evaporator is often regarded as low-grade waste heat, and its thermal energy utilization rate is low. These secondary steam usually contain a large amount of latent heat, but due to its low temperature and pressure, it cannot be directly and efficiently utilized. It is often directly condensed and discharged or cooled by a cooling water system, which not only wastes energy, but also increases the consumption and treatment costs of cooling water. In addition, the condensed water is often not fully recycled during the treatment process, further exacerbating the problem of resource waste and environmental pollution.

[0003] In response to the above problems, the industry has been exploring more efficient and energy-saving waste heat recovery technologies. Among them, Mechanical Vapor Recompression (MVR) technology, as an advanced energy-saving technology, has gradually attracted widespread attention. MVR technology compresses the secondary steam separated from the evaporator through a mechanical compressor, increasing its temperature, pressure and thermal enthalpy, so that it can re-enter the evaporator heating chamber as a high-quality heat source for condensation and heat release, thereby achieving efficient recovery and utilization of the latent heat of the secondary steam. This technology not only significantly reduces the demand for external energy, but also eliminates the traditional secondary steam cooling water system, achieving the dual goals of energy saving and consumption reduction and water saving and emission reduction.

[0004] However, the existing MVR technology still faces some challenges in practical applications, such as high equipment investment cost, large evaporator heat exchange area, easy scaling, etc. Therefore, further optimizing MVR technology and improving its economy and practicality has become one of the current research hotspots. Utility Model Content

[0005] The utility model aims to provide a mechanical heat compression energy-saving device for efficiently recovering and reusing low-grade waste heat of steam, so as to realize efficient recovery and utilization of secondary steam heat energy.

[0006] To achieve the above purpose, the technical solution adopted by the utility model is to provide a mechanical heat compression energy-saving device for efficiently recovering and reusing low-grade waste heat of steam, including:

[0007] The evaporation tank comprises a circulation pipe, a heating chamber and an evaporation chamber, wherein the brine is forced to circulate between the circulation pipe, the heating chamber and the evaporation chamber under the impetus of a circulation pump, the heating chamber heats the brine through the heating pipe therein, and the brine evaporates and concentrates in the evaporation chamber to precipitate sodium chloride crystals;

[0008] a steam scrubber connected to the evaporation tank through a pipeline, receiving secondary steam from the evaporation tank and scrubbing the steam with condensed water to remove salt-containing foam;

[0009] A steam compressor is connected to the steam scrubber through a pipeline, sucks in the steam after washing and pressurizes it, and then sends the pressurized steam back to the heating chamber of the evaporation tank for recycling. Two anti-surge valves are arranged in parallel at the outlet of the steam compressor, and the output end of the anti-surge valve is connected to the top of the steam scrubber;

[0010] A preheater, connected to the steam condensate system, is used to preheat the brine entering the evaporation tank and utilize the steam condensate for heat exchange;

[0011] a condensate bucket, which collects condensate from the heating chamber and the steam compressor, and delivers the condensate to the steam scrubber and the preheater for reuse through a condensate pump;

[0012] a defoamer, arranged on the pipeline between the evaporation tank and the steam scrubber, for removing salt-containing foam in the secondary steam;

[0013] A salt leg is arranged at the bottom of the evaporation tank, the salt leg is communicated with the evaporation chamber, and is used for collecting settled salt crystals.

[0014] In one embodiment, the evaporation tank further includes a separation section for discharging an appropriate amount of mother liquor to a purification process or directly recycling it to ensure product quality.

[0015] In one embodiment, the steam scrubber uses condensed water from a washing water pump for washing, and the steam after washing is pressurized by a steam compressor and then sent back to the heating chamber to achieve recycling of the steam.

[0016] In one embodiment, the preheater includes a plate heat exchanger and a shell and tube heat exchanger.

[0017] In one embodiment, a bypass with an automatic control butterfly valve is installed on the inlet and outlet connecting pipelines of the steam compressor to adjust the inlet and outlet compression ratio under different process conditions.

[0018] In one embodiment, the preheater utilizes high-temperature condensed water from the condensed water bucket for heat exchange to preheat the brine entering the evaporation tank, and cools the condensed water and sends it to the washing water bucket or to the power workshop for secondary utilization.

[0019] One or more of the above technical solutions in the embodiments of the present utility model have at least the following technical effects or advantages:

[0020] The mechanical heat compression energy-saving device for efficiently recovering and reusing low-grade waste heat of steam provided by the embodiment of the utility model compresses the secondary steam separated from the evaporator through the mechanical vapor recompression (MVR) technology, increases its temperature, pressure and thermal enthalpy, and enables it to re-enter the evaporator heating chamber as a high-quality heat source, thereby realizing efficient recovery and utilization of the latent heat of the secondary steam. And because the thermal energy of the secondary steam is efficiently recovered and utilized, the demand for external steam generation is significantly reduced, thereby improving the energy utilization efficiency of the entire evaporation system. In addition, the traditional secondary steam cooling water system is eliminated, and the heat released by the condensed water is used to preheat the brine, which not only saves the consumption of cooling water, but also realizes the reuse of the condensed water. Finally, an anti-surge valve is cleverly added to the steam compressor to make the steam compressor run more smoothly, safely and effectively to ensure the normal operation of the equipment.

[0021] To sum up, the mechanical heat compression energy-saving device for efficient recovery and reuse of low-grade waste heat of steam provided by the embodiment of the utility model realizes the efficient recovery and reuse of low-grade waste heat of steam, improves energy utilization efficiency, and saves cooling water consumption, and has significant technical effects and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A schematic diagram of a mechanical heat compression energy-saving device for efficiently recovering and reusing low-grade waste heat of steam provided in an embodiment of the utility model.

[0024] The respective reference numerals are as follows:

[0025] 1. Evaporation tank; 2. Steam scrubber; 3. Steam compressor; 4. Preheater; 5. Condensate bucket; 6. Defoamer; 7. Salt leg; 8. Washing water pump; 9. Condensate pump; 10. Brine pump; 11. Circulation pipe; 12. Heating chamber; 13. Evaporation chamber; 14. Compressor power part; 31. Anti-surge valve; 41. Plate heat exchanger; 42. Shell and tube heat exchanger. DETAILED DESCRIPTION

[0026] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0027] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship 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 device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0028] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. 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 utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0029] In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix" and the like 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 an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] See also Figure 1The embodiment of the present application provides a mechanical heat compression energy-saving device for efficient recovery and reuse of low-grade waste heat of steam, including an evaporation tank 1, a steam scrubber 2, a steam compressor 3, a preheater 4, a condensed water bucket 5, a defoamer 6, and a salt leg 7. The evaporation tank 1 includes a circulation pipe 11, a heating chamber 12, and an evaporation chamber 13, wherein the brine is forced to circulate between the circulation pipe 11, the heating chamber 12, and the evaporation chamber 13 under the promotion of a circulation pump, and the heating chamber 12 heats the brine through the heating pipe therein, and the brine evaporates and concentrates in the evaporation chamber 13 to precipitate sodium chloride crystals. The steam scrubber 2 is connected to the evaporation tank 1 through a pipeline, receives secondary steam from the evaporation tank 1, and washes the steam with condensed water to remove salt-containing foam. The steam compressor 3 is connected to the steam scrubber 2 through a pipeline, sucks in the washed steam and pressurizes it, and then sends the pressurized steam back to the heating chamber 12 of the evaporator 1 for recycling. Two anti-surge valves 31 (model DN500) are arranged in parallel at the outlet of the steam compressor 3, and the output end of the anti-surge valve 31 is connected to the top of the steam scrubber 2. The preheater 4 is connected to the steam condensate system, which is used to preheat the brine entering the evaporator 1 and use the steam condensate for heat exchange. The preheater 4 specifically includes a plate heat exchanger 41 and a shell and tube heat exchanger 42. The condensate bucket 5 collects the condensate from the heating chamber 12 and the steam compressor 3, and sends the condensate to the steam scrubber 2 and the preheater 4 through the condensate pump 9 for reuse. The defoamer 6 is arranged on the pipeline between the evaporator 1 and the steam scrubber 2, and is used to remove the salt-containing foam in the secondary steam. The salt leg 7 is arranged at the bottom of the evaporator 1, and the salt leg 7 is connected to the evaporation chamber 13 to collect the settled salt crystals.

[0031] Optionally, the model of the steam compressor 3 is EGV100-1, which not only meets the needs of single-effect salt production, but also has mature technology, stable operation, and is more environmentally friendly and energy-saving.

[0032] The steam compressor 3 is driven by a compressor power section 14, which includes a main motor, which is connected to the steam compressor 3 through a coupler and a gear box to provide power for the steam compressor 3. The compressor power section 14 also includes a wheel pulley system (such as a wheel pulley system) for lubricating the gear box. Figure 1 The main motor is also included in the cooling system.

[0033] The MVR system single-effect salt production process provided in this embodiment specifically includes the following processes:

[0034] Figure 1 In the figure, the blue line segment is the brine flow route, the red line segment is the steam flow route, and the green line segment is the condensate flow route.

[0035] 1. MVR evaporation tank 1 process flow

[0036] The brine in the saltpeter brine barrel is pumped to the preheater 4 for preheating by the brine pump 10. The brine preheated by the preheater 4 is sent to the evaporation chamber 13. Driven by the circulation pump, the brine in the evaporation tank 1 is forced to circulate between the circulation pipe 11, the heating chamber 12 and the evaporation chamber 13. The brine is heated in the heating pipe of the heating chamber 12, and the heated brine enters the evaporation chamber 13 to participate in the next cycle. During the continuous circulation of the brine, it continuously exchanges heat with steam through the pipe wall during the process of passing through the heating chamber 12, and the temperature continues to rise. When the temperature rises to the boiling point, the brine rises to near the liquid surface and is in a boiling state, and the water evaporates. The brine in the evaporation tank 1 continuously evaporates water and continuously concentrates. When the brine is concentrated to saturation, sodium chloride crystals are precipitated, water is continuously evaporated, and salt crystals are continuously precipitated. Salt crystals fall under the action of gravity, and small crystals grow in the process of falling, accelerating the sedimentation. When the crystals grow to a certain extent and can overcome the upward buoyancy of the washing brine in the salt leg 7, they settle to the salt leg 7. Under the action of the washing brine, the small crystals are brought back to the evaporation chamber 13 to continue growing.

[0037] The secondary steam generated by the boiling of the solution in the evaporator 1 passes through the demister 6 to remove the salt-containing foam and then enters the steam scrubber 2 for washing with condensed water. The washed steam is introduced into the steam compressor 3, and after being pressurized by the compressor, it returns to the heating chamber 12 to heat the brine, and the cycle repeats. (Note: During the startup phase of the MVR workshop, the brine in the evaporator 1 is directly heated with the raw steam from the power until it reaches the boiling temperature and the compressor is started). The salt crystals collected in the salt leg 7 are washed with brine: some impurities can be dissolved; fine particles can be brought back to the evaporator 1 to continue to grow; the salt crystals in the salt leg 7 can be fluidized; the salt slurry can be cooled, which is beneficial to the operation of the centrifuge. The heating chamber 12 is operated with a slight positive pressure, and the non-condensable gas is directly discharged into the atmosphere through a pipe with a limited flow orifice. In order to ensure the quality of the product, it is necessary to discharge an appropriate amount of mother liquor through the separation section to the purification process or directly recycle it.

[0038] 2. Steam scrubber 2 process flow

[0039] The secondary steam from the evaporation tank 1 is sent to the steam scrubber 2. Before the steam enters the steam scrubber 2, the salt-containing foam is removed by the demister 6. The secondary steam enters the steam scrubber 2 from the central tube of the steam scrubber 2 from top to bottom, and is washed with condensed water from the washing water pump 8 in the steam scrubber 2. After the washing water at the bottom of the steam scrubber 2 is pressurized by the washing water pump 8, most of it is sprayed through the nozzle to wash the secondary steam entering the scrubber, and the residual salt foam in the steam is removed; another part of the condensed water is sent to the demister 6 as the washing water of the demister 6, and the remaining part of the condensed water is sent to the preheater 4 as the brine preheating medium. The steam washed with condensed water enters the steam compressor 3. During the washing process, the steam scrubber 2 needs to be supplemented with condensed water from the condensed water pump 9 to maintain the water level.

[0040] 3. Compressor process flow

[0041] The steam from the steam scrubber 2 is sucked into the compressor and pressurized by the radial flow turbine of the compressor. The temperature and pressure of the compressed steam increase. Since the saturation temperature of the pressurized steam is higher than the liquid temperature of the evaporator 1, the liquid in the evaporator 1 can be heated by the compressed steam. After the pressurized steam exchanges heat with the brine flowing through the heating chamber 12, it condenses into water in the shell layer, and the condensed water flows into the condensate bucket 5, and then is sent to the steam scrubber 2 and the shell-and-tube heat exchanger 42 through the condensate pump 9. The inlet pipe and volute of the compressor need to be drained, and the condensed water enters the condensate bucket 5 through the drainage pipe. A bypass with an automatic control butterfly valve is installed on the compressor inlet and outlet connecting pipelines. The function of the bypass is to adjust the inlet and outlet compression ratio under different process conditions.

[0042] 4. Steam condensate process

[0043] The condensed water in the heating chamber 12 flows into the condensed water barrel 5, and after being pressurized by the condensed water pump 9, the water level of the steam scrubber 2 is replenished first. The remaining high-temperature condensed water is cooled by the preheater 4 and then sent to the washing water barrel or to the power workshop for secondary use.

[0044] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A mechanical heat compression energy-saving device for efficiently recovering and reusing low-grade waste heat of steam, characterized in that: The mechanical heat compression energy-saving device for efficiently recovering and reusing low-grade waste heat of steam comprises: The evaporation tank comprises a circulation pipe, a heating chamber and an evaporation chamber, wherein the brine is forced to circulate between the circulation pipe, the heating chamber and the evaporation chamber under the impetus of a circulation pump, the heating chamber heats the brine through the heating pipe therein, and the brine evaporates and concentrates in the evaporation chamber to precipitate sodium chloride crystals; a steam scrubber connected to the evaporation tank through a pipeline, receiving secondary steam from the evaporation tank and scrubbing the steam with condensed water to remove salt-containing foam; A steam compressor is connected to the steam scrubber through a pipeline, sucks in the steam after washing and pressurizes it, and then sends the pressurized steam back to the heating chamber of the evaporation tank for recycling. Two anti-surge valves are arranged in parallel at the outlet of the steam compressor, and the output end of the anti-surge valve is connected to the top of the steam scrubber; A preheater, connected to the steam condensate system, is used to preheat the brine entering the evaporation tank and utilize the steam condensate for heat exchange; a condensate bucket, which collects condensate from the heating chamber and the steam compressor, and delivers the condensate to the steam scrubber and the preheater for reuse through a condensate pump; a defoamer, arranged on the pipeline between the evaporation tank and the steam scrubber, for removing salt-containing foam in the secondary steam; A salt leg is arranged at the bottom of the evaporation tank, the salt leg is communicated with the evaporation chamber, and is used for collecting settled salt crystals.

2. The mechanical heat compression energy-saving device for efficiently recovering and reusing low-grade waste heat of steam according to claim 1 is characterized in that: The evaporation tank also includes a separation section for discharging an appropriate amount of mother liquor to a purification process or directly recycling it to ensure product quality.

3. The mechanical heat compression energy-saving device for efficiently recovering and reusing low-grade waste heat of steam according to claim 1 or 2 is characterized in that: The steam scrubber uses condensed water from a washing water pump for washing, and the steam after washing is pressurized by a steam compressor and then sent back to the heating chamber, thereby realizing the recycling of steam.

4. The mechanical heat compression energy-saving device for efficiently recovering and reusing low-grade waste heat of steam according to claim 3 is characterized in that: The preheater includes a plate heat exchanger and a shell and tube heat exchanger.

5. The mechanical heat compression energy-saving device for efficiently recovering and reusing low-grade waste heat of steam according to claim 1 is characterized in that: A bypass with an automatic control butterfly valve is installed on the inlet and outlet connecting pipelines of the steam compressor to adjust the inlet and outlet compression ratio under different process conditions.

6. The mechanical heat compression energy-saving device for efficiently recovering and reusing low-grade waste heat of steam according to claim 5 is characterized in that: The preheater utilizes the high-temperature condensed water from the condensed water bucket for heat exchange, preheats the brine entering the evaporation tank, and cools the condensed water and sends it to the washing water bucket or to the power workshop for secondary utilization.

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