Atmospheric pressure low temperature waste heat evaporation crystallization system

Abstract

The present invention discloses a normal-pressure, low-temperature waste heat evaporation crystallization system, which relates to the technical field of evaporation crystallization and includes an evaporation tower, a centrifugal fan, an air scrubbing purification tower, a steam-water heat exchanger, and an air preheater connected end to end via an air duct; the bottom end of the evaporation tower is connected in sequence to a concentrate pump, a flash tank, and a crystallization kettle via a liquid pipe; the air preheater is connected to an air inlet filter and the evaporation tower; the bottom end of the evaporation tower is also connected in sequence to an evaporation circulation pump and the steam-water heat exchanger via a liquid pipe, the solute output end of the steam-water heat exchanger is connected to a waste heat utilization device via a pipeline, and the output end of the waste heat utilization device is connected to an evaporation spray device in the evaporation tower via a pipeline. The normal-pressure, low-temperature waste heat evaporation crystallization system provided by the present invention does not use a multi-stage evaporation device or a steam compressor. After heating the solute to a certain temperature, it is allowed to evaporate naturally, thereby achieving low-temperature operation under normal pressure conditions. The system can fully utilize waste heat and waste heat to achieve a significant reduction in energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of evaporation and crystallization, and in particular to a normal-pressure and low-temperature waste-heat evaporation and crystallization system. Background Art

[0002] The evaporation crystallization process is widely used in various fields. For example, in the chemical industry, it is used to concentrate materials and recover solutes; in the environmental protection field, it is used to treat sewage so that sewage meets discharge standards.

[0003] Existing evaporation crystallization equipment is mainly divided into two types, one is a multiple-effect evaporator and the other is a mechanical recompression evaporator.

[0004] A multi-effect evaporator is a device that connects multiple evaporation devices in series. The secondary steam generated by the first evaporation device is used as the heat source for the next evaporation device. Although this device achieves multiple utilization of the steam heat source, the heat transfer temperature difference decreases as the number of effects increases, which limits the number of equipment effects. In addition, its investment cost increases rapidly as the number of equipment effects increases.

[0005] A mechanical recompression evaporator recycles the secondary steam generated by evaporation, raising its saturation temperature and pressure via a steam compressor before returning it to the evaporator for continued use as a heat source. However, the increased boiling point of the concentrated liquid significantly reduces the efficiency of the steam compressor. Furthermore, contact between the volatile substances produced during evaporation and the steam compressor can cause corrosion and wear, making equipment maintenance difficult. Furthermore, the high cost of steam compressors increases the investment cost of mechanical recompression evaporators.

[0006] Both multi-effect evaporation and mechanical recompression evaporation operate at the boiling point of the solute. Reaching this boiling point often requires vacuum decompression equipment, further increasing equipment investment costs. Therefore, providing a low-temperature, atmospheric-pressure waste heat evaporation crystallization system that achieves low-temperature, atmospheric-pressure operation and reduces equipment investment and maintenance costs has become a pressing challenge for those skilled in the art. Summary of the Invention

[0007] The purpose of the present invention is to provide a normal pressure low temperature waste heat evaporation crystallization system to solve the problems of high investment cost and equipment maintenance cost of existing evaporation crystallization equipment.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] The present invention discloses a normal pressure low temperature waste heat evaporation crystallization system, comprising an evaporation tower, a centrifugal fan, an air washing purification tower, a steam-water heat exchanger, and an air preheater, which are sequentially connected end to end through an air duct;

[0010] The bottom end of the evaporation tower is sequentially connected to a concentrate pump, a flash tank and a crystallization kettle through a liquid pipe;

[0011] The air inlet end of the air preheater is connected to an air inlet filter, and the air outlet end of the air preheater is additionally provided with an air duct connected to the side wall of the evaporation tower, and an anemometer is installed on the air duct;

[0012] The bottom end of the evaporation tower is also connected to an evaporation circulation pump and the steam-water heat exchanger in sequence through a liquid pipe. The solute output end of the steam-water heat exchanger is connected to a waste heat utilization device through a pipeline. The output end of the waste heat utilization device is connected to the evaporation spray device in the evaporation tower through a pipeline.

[0013] Preferably, the evaporation spray device is located at the top of the evaporation tower, a convection heat and mass exchange filling area is provided below the evaporation spray device, an evaporation air inlet is provided on the side wall of the evaporation tower, the evaporation air inlet is located below the convection heat and mass exchange filling area, and the evaporation air inlet is connected to the output end of the air preheater through an air duct;

[0014] The side wall of the evaporation tower is also provided with an evaporation liquid outlet, a water retaining weir is provided at the evaporation liquid outlet, and the evaporation liquid outlet is connected to the evaporation circulation pump through a liquid pipe;

[0015] The top of the evaporation tower is provided with an evaporation air outlet, and the evaporation air outlet is connected to the centrifugal fan through an air duct;

[0016] A concentrated liquid outlet is provided at the bottom of the evaporation tower, and the concentrated liquid outlet is connected to the concentrated liquid pump through a liquid pipe. A density monitoring control device and an automatic valve are sequentially provided on the liquid pipe connected to the concentrated liquid outlet, and the density monitoring control device and the automatic valve are electrically connected.

[0017] Preferably, a scrubbing air inlet is provided on the side wall of the scrubbing purification tower, and the scrubbing air inlet is connected to the output end of the centrifugal fan through an air duct. A scrubbing air outlet is provided on the top of the scrubbing purification tower, and the scrubbing air outlet is connected to the steam-water heat exchanger through an air duct. A scrubbing spray device and a gas-liquid contact filling area are provided inside the scrubbing purification tower, and the scrubbing spray device is located at the top of the scrubbing purification tower, and the gas-liquid contact filling area is located between the scrubbing spray device and the scrubbing air inlet.

[0018] The scrubbing and purification tower is further provided with a constant temperature heating device, which is located below the gas-liquid contact filler area; the constant temperature heating device is connected to a temperature monitoring and control device, which is located outside the scrubbing and purification tower;

[0019] A washing absorption liquid outlet is also provided at the bottom of the washing purification tower, and a washing circulation pump is connected to the washing absorption liquid outlet through a pipeline. The output end of the washing circulation pump is connected to the washing spray device through a pipeline.

[0020] Preferably, the convective heat and mass exchange filler area uses high-efficiency random or structured packing.

[0021] Preferably, the evaporation spray device adopts a conical nozzle.

[0022] Preferably, the water retaining weir is semicircular, and the bottom end of the water retaining weir is inserted to a preset depth below the liquid surface.

[0023] Preferably, the density monitoring and control device uses a tuning fork or conductivity densitometer to detect the medium density.

[0024] Preferably, the constant temperature heating device adopts a corrosion-resistant electric heater, and the temperature monitoring and control device adopts a platinum resistance temperature sensor to detect the temperature of the scrubbing absorption liquid.

[0025] Preferably, the steam-water heat exchanger is a heat pipe steam-water heat exchanger, which is used to recover the latent heat of vaporization in the hot and humid air; the air preheater is a heat pipe air heat exchanger, which is used to preheat the dry air entering through the air inlet filter.

[0026] Preferably, the waste heat utilization device adopts a plate heat exchanger, a steam pipe heat exchanger, a finned tube flue gas heat exchanger or a normal pressure hot water boiler.

[0027] Compared with the prior art, the present invention has the following beneficial technical effects:

[0028] The atmospheric-pressure, low-temperature waste heat evaporation crystallization system provided by the present invention does not use a multi-stage evaporation device or a steam compressor. Instead, it heats the solute to a certain temperature and then evaporates it naturally, achieving low-temperature operation under atmospheric pressure. This system can fully utilize waste heat and significantly reduce energy consumption.

[0029] An air washing and purification tower is added at the end of the evaporation tower to ensure that the exhausted air is odorless and avoid secondary pollution caused by the exhausted air.

[0030] Low temperature and normal pressure operation makes the equipment operation and maintenance simple and easy. The equipment can be manufactured using a large amount of non-metallic materials, which has low cost, high reliability, good corrosion resistance, no secondary pollution, and significantly improved technical and economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below with reference to the accompanying drawings.

[0032] Figure 1 This is a schematic diagram of the principle of the atmospheric pressure and low temperature waste heat evaporation crystallization system of the present invention.

[0033] Description of reference numerals: 1. evaporation tower; 2. gas washing and purification tower; 8. waste heat utilization device;

[0034] 11. Evaporation spray device; 12. Water retaining weir; 13. Convective heat and mass exchange filling area; 15. Density monitoring and control device; 16. Automatic valve; 17. Evaporation circulation pump;

[0035] 21. Air washing spray device; 22. Air washing circulation pump; 23. Constant temperature heating device; 24. Temperature monitoring and control device; 25. Gas-liquid contact filler area;

[0036] 31. Concentrate pump; 32. Flash tank; 33. Crystallization kettle;

[0037] 41. Air inlet filter; 42. Anemometer; 43. Centrifugal fan;

[0038] 61. Steam-water heat exchanger; 62. Air preheater. DETAILED DESCRIPTION

[0039] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] like Figure 1 As shown, a normal pressure low temperature waste heat evaporation crystallization system includes an evaporation tower 1, a centrifugal fan 43, an air scrubbing tower 2, a steam-water heat exchanger 61, and an air preheater 62 connected end to end through an air duct;

[0041] The bottom end of the evaporation tower 1 is connected to a concentrate pump 31, a flash tank 32 and a crystallization kettle 33 in sequence through liquid pipes;

[0042] The air inlet end of the air preheater 62 is connected to the air inlet filter 41, and the air outlet end of the air preheater 62 is additionally provided with an air duct connected to the side wall of the evaporation tower 1 and an anemometer 42 is installed on the air duct;

[0043] The bottom end of the evaporation tower 1 is also connected to the evaporation circulation pump 17 and the steam-water heat exchanger 61 in sequence through a liquid pipe. The solute output end of the steam-water heat exchanger 61 is connected to the waste heat utilization device 8 through a pipeline. The output end of the waste heat utilization device 8 is connected to the evaporation spray device 11 in the evaporation tower 1 through a pipeline.

[0044] Specifically, the evaporation spray device 11 is located at the top of the evaporation tower 1, and a convection heat and mass exchange filling area 13 is provided below the evaporation spray device 11. An evaporation air inlet is provided on the side wall of the evaporation tower 1. The evaporation air inlet is located below the convection heat and mass exchange filling area 13. The evaporation air inlet is connected to the output end of the air preheater 62 through an air duct.

[0045] The side wall of the evaporation tower 1 is also provided with an evaporation liquid outlet, a water retaining weir 12 is provided at the evaporation liquid outlet, and the evaporation liquid outlet is connected to the evaporation circulation pump 17 through a liquid pipe;

[0046] The top of the evaporation tower 1 is provided with an evaporation air outlet, which is connected to the centrifugal fan 43 through an air duct;

[0047] A concentrated liquid outlet is provided at the bottom of the evaporation tower 1, and the concentrated liquid outlet is connected to the concentrated liquid pump 31 through a liquid pipe. A density monitoring control device 15 and an automatic valve 16 are sequentially provided on the liquid pipe connected to the concentrated liquid outlet, and the density monitoring control device 15 and the automatic valve 16 are electrically connected.

[0048] Specifically, a scrubbing air inlet is provided on the side wall of the scrubbing purification tower 2, and the scrubbing air inlet is connected to the output end of the centrifugal fan 43 through an air duct. A scrubbing air outlet is provided on the top of the scrubbing purification tower 2, and the scrubbing air outlet is connected to the steam-water heat exchanger 61 through an air duct. A scrubbing spray device 21 and a gas-liquid contact filler area 25 are provided inside the scrubbing purification tower 2. The scrubbing spray device 21 is located at the top of the scrubbing purification tower 2, and the gas-liquid contact filler area 25 is located between the scrubbing spray device 21 and the scrubbing air inlet.

[0049] The scrubbing and purification tower 2 is further provided with a constant temperature heating device 23, which is located below the gas-liquid contact filler area 25; the constant temperature heating device 23 is connected to a temperature monitoring and control device 24, which is located outside the scrubbing and purification tower 2;

[0050] A washing absorption liquid outlet is also provided at the bottom of the washing purification tower 2, and a washing circulation pump 22 is connected to the washing absorption liquid outlet through a pipeline. The output end of the washing circulation pump 22 is connected to the washing spray device 21 through a pipeline.

[0051] Specifically, the convective heat and mass exchange filler area 13 uses high-efficiency random packing or structured packing.

[0052] In a specific implementation, the convective heat and mass exchange filler area 13 uses high-efficiency random packing or structured packing made of metal or plastic.

[0053] Specifically, the evaporation spray device 11 adopts a conical nozzle.

[0054] Specifically, the water retaining weir 12 is semicircular, and the bottom end of the water retaining weir 12 is inserted into a preset depth below the liquid surface.

[0055] Specifically, the density monitoring and control device 15 uses a tuning fork type or conductivity type densitometer to detect the medium density.

[0056] Specifically, the constant temperature heating device 23 adopts a corrosion-resistant electric heater, and the temperature monitoring and control device 24 adopts a platinum resistance temperature sensor to detect the temperature of the scrubbing absorption liquid.

[0057] Specifically, the steam-water heat exchanger 61 is a heat pipe steam-water heat exchanger, and the steam-water heat exchanger 61 is used to recover the latent heat of vaporization in the hot and humid air; the air preheater 62 is a heat pipe air heat exchanger, and is used to preheat the dry air entering through the air inlet filter 41.

[0058] Specifically, the waste heat utilization device 8 adopts a plate heat exchanger, a steam pipe heat exchanger, a finned tube flue gas heat exchanger or a normal pressure hot water boiler.

[0059] The use process of the present invention is as follows:

[0060] The evaporation medium enters the evaporation tower 1 through a pipeline and is evenly sprayed onto the convective heat and mass exchange packing area 13 by the evaporation spray device 11 at the top of the evaporation tower 1, exchanging heat and mass with the dry air entering the evaporation tower 1 through the evaporation air inlet. Afterwards, the moisture content of the dry air increases, and the enthalpy value increases to form humid and hot air. Under the suction of the centrifugal fan 43, the humid and hot air enters the scrubbing purification tower 2 through the air duct. In the gas-liquid contact packing area 25, it contacts and purifies the scrubbing absorbent, obtaining purified air. The purified air is discharged from the scrubbing purification tower 2 through the scrubbing air outlet. Among them, the convective heat and mass exchange packing area 13 is used to achieve droplet distribution or thin liquid film uniform distribution of the evaporation medium. At the evaporation air inlet, when the dry air enters the narrow flow channel horizontally and is sprayed into the large space of the convective heat and mass exchange packing area 13, a local micro-negative pressure is formed around the flow channel, which increases the pressure difference between the liquid surface vapor partial pressure and the gas phase vapor partial pressure, thereby enhancing the diffusion of solutes from the liquid phase to the gas phase.

[0061] After the evaporation medium evaporates and cools down in the evaporation tower 1, it falls to the bottom of the evaporation tower 1, enters the liquid pipe through the evaporation liquid outlet, and is pumped into the steam-water heat exchanger 61 by the evaporation circulation pump 17. At the same time, the purified air discharged from the scrubbing outlet of the scrubbing purification tower 2 also enters the steam-water heat exchanger 61. The evaporation medium absorbs the latent heat of vaporization of the purified air and enters the waste heat utilization device 8. The evaporation medium is further heated by heat exchange and utilization of waste heat. After reaching the preset evaporation temperature, it is sprayed into the convection heat and mass exchange filler area 13 in the evaporation tower 1 through the evaporation spray device 11, thereby achieving continuous evaporation and concentration.

[0062] During the continuous evaporation and concentration process, at the bottom of the evaporation tower 1, the concentrated liquid with a higher specific gravity sinks, while the concentrated liquid with a lower specific gravity rises and flows out of the evaporation tower 1 from the bottom of the water retaining weir 12, thereby achieving the separation of the concentrated liquid. The concentrated liquid with a lower specific gravity enters the circulating evaporation and concentration. When the density monitoring and control device 15 detects that the concentrated liquid at the bottom of the evaporation tower 1 reaches a preset value, it controls the automatic valve 16 and the concentrated liquid pump 31 to open, and the concentrated liquid is pumped into the flash tank 32.

[0063] The flash tank 32 is maintained in a negative pressure state. After the evaporation medium enters the flash tank 32, it flash evaporates and is further concentrated to form a supersaturated solution. The solution is discharged from the bottom of the flash tank 32 and enters the crystallization kettle 33. The supersaturation is released in the crystallization kettle 33, and crystals are formed and discharged from the bottom of the crystallization kettle 33.

[0064] The enthalpy value of the purified air discharged through the steam-water heat exchanger 61 is greatly reduced. After passing through the air preheater 62, the purified air is discharged from the low-temperature, normal-pressure waste heat evaporation and crystallization system. In the air preheater 62, the purified air exchanges heat and mass with the dry air entering through the air inlet filter 41. The dry air is heated and the centrifugal fan 43 is controlled by the anemometer 42, thereby controlling the air volume of the dry air entering the evaporation tower 1.

[0065] A constant-temperature heating device 23 and a temperature monitoring and control device 24 are installed at the bottom of the scrubbing and purification tower to maintain the circulating scrubbing and absorption liquid at a set temperature, preventing condensation of the hot and humid air entering the scrubbing and purification tower and diluting the scrubbing and absorption liquid. The scrubbing and absorption liquid absorbs corrosive and toxic gases from the hot and humid air.

[0066] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0067] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A normal pressure low temperature waste heat evaporation crystallization system, characterized by: It includes an evaporation tower (1), a centrifugal fan (43), an air scrubber (2), a steam-water heat exchanger (61), and an air preheater (62) which are sequentially connected end to end through an air duct; The bottom end of the evaporation tower (1) is connected to a concentrate pump (31), a flash tank (32) and a crystallization kettle (33) in sequence through liquid pipes; The air inlet end of the air preheater (62) is connected to an air inlet filter (41), and the air outlet end of the air preheater (62) is additionally provided with an air duct connected to the side wall of the evaporation tower (1), and an anemometer (42) is installed on the air duct; The bottom end of the evaporation tower (1) is also connected to an evaporation circulation pump (17) and the steam-water heat exchanger (61) in sequence through a liquid pipe, the solute output end of the steam-water heat exchanger (61) is connected to a waste heat utilization device (8) through a pipeline, and the output end of the waste heat utilization device (8) is connected to an evaporation spray device (11) in the evaporation tower (1) through a pipeline; The evaporation spray device (11) is located at the top of the evaporation tower (1), a convection heat and mass exchange filling area (13) is provided below the evaporation spray device (11), an evaporation air inlet is provided on the side wall of the evaporation tower (1), the evaporation air inlet is located below the convection heat and mass exchange filling area (13), and the evaporation air inlet is connected to the output end of the air preheater (62) through an air duct; An evaporation liquid outlet is also provided on the side wall of the evaporation tower (1), a water retaining weir (12) is provided at the evaporation liquid outlet, and the evaporation liquid outlet is connected to the evaporation circulation pump (17) through a liquid pipe; An evaporation air outlet is provided at the top of the evaporation tower (1), and the evaporation air outlet is connected to the centrifugal fan (43) through an air duct; A concentrated liquid outlet is provided at the bottom of the evaporation tower (1), the concentrated liquid outlet is connected to the concentrated liquid pump (31) via a liquid pipe, a density monitoring control device (15) and an automatic valve (16) are sequentially provided on the liquid pipe connected to the concentrated liquid outlet, and the density monitoring control device (15) and the automatic valve (16) are electrically connected; A scrubbing air inlet is provided on the side wall of the scrubbing purification tower (2), and the scrubbing air inlet is connected to the output end of the centrifugal fan (43) through an air duct. A scrubbing air outlet is provided on the top of the scrubbing purification tower (2), and the scrubbing air outlet is connected to the steam-water heat exchanger (61) through an air duct. A scrubbing spray device (21) and a gas-liquid contact filler area (25) are provided inside the scrubbing purification tower (2), and the scrubbing spray device (21) is located at the top of the scrubbing purification tower (2), and the gas-liquid contact filler area (25) is located between the scrubbing spray device (21) and the scrubbing air inlet.

2. The atmospheric pressure low temperature waste heat evaporation crystallization system according to claim 1, characterized in that: The scrubbing and purification tower (2) is further provided with a constant temperature heating device (23), and the constant temperature heating device (23) is located below the gas-liquid contact filler area (25); the constant temperature heating device (23) is connected to a temperature monitoring and control device (24), and the temperature monitoring and control device (24) is located outside the scrubbing and purification tower (2); A washing absorption liquid outlet is also provided at the bottom of the washing purification tower (2), and a washing circulation pump (22) is connected to the washing absorption liquid outlet via a pipeline. The output end of the washing circulation pump (22) is connected to the washing spray device (21) via a pipeline.

3. The atmospheric pressure low temperature waste heat evaporation crystallization system according to claim 1, characterized in that: The convective heat and mass exchange packing area (13) uses high-efficiency random packing or structured packing.

4. The atmospheric pressure low temperature waste heat evaporation crystallization system according to claim 1, characterized in that: The evaporation spray device (11) adopts a conical nozzle.

5. The atmospheric pressure low temperature waste heat evaporation crystallization system according to claim 1, characterized in that: The water retaining weir (12) is semicircular in shape, and the bottom end of the water retaining weir (12) is inserted to a preset depth below the liquid surface.

6. The atmospheric pressure low temperature waste heat evaporation crystallization system according to claim 1, characterized in that: The density monitoring and control device (15) uses a tuning fork type or conductivity type densitometer to detect the density of the medium.

7. The atmospheric pressure low temperature waste heat evaporation crystallization system according to claim 2, characterized in that: The constant temperature heating device (23) adopts a corrosion-resistant electric heater, and the temperature monitoring and control device (24) adopts a platinum resistance temperature sensor to detect the temperature of the scrubbing absorption liquid.

8. The atmospheric pressure low temperature waste heat evaporation crystallization system according to claim 1, characterized in that: The steam-water heat exchanger (61) is a heat pipe type steam-water heat exchanger, and the steam-water heat exchanger (61) is used to recover the latent heat of vaporization in the hot and humid air; the air preheater (62) is a heat pipe type air heat exchanger, and is used to preheat the dry air entering through the air inlet filter (41).

9. The atmospheric pressure low temperature waste heat evaporation crystallization system according to claim 1, characterized in that: The waste heat utilization device (8) adopts a plate heat exchanger, a steam pipe heat exchanger, a finned tube flue gas heat exchanger or a normal pressure hot water boiler.

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