Flash evaporation device and method for twice cooling of liquid ammonia in liquid ammonia refrigeration process

Abstract

The invention belongs to the technical field of liquid ammonia refrigeration, and particularly relates to a flash evaporation device and method for twice cooling of liquid ammonia in a liquid ammonia refrigeration process. According to a flash tank disclosed in the prior art, through pressure reduction, liquid ammonia is subjected to flash vaporization and heat absorption at the liquid ammonia liquid level in the flash tank, heat exchange between the liquid ammonia and gaseous ammonia occurs at the liquid ammonia liquid level, and the flash vaporization refrigeration effect is poor; according to the invention, the atomization device is arranged, so that flash gas ammonia and atomized liquid ammonia are in full contact in a space above the liquid level of liquid ammonia in the flash tank for heat exchange; compared with a flash tank disclosed in the prior art, heat exchange between liquid ammonia and gas ammonia exists in the space above the liquid level of the liquid ammonia in the flash tank, the heat exchange area is larger, the flash refrigeration effect is better, and therefore the temperature of the liquid ammonia can be efficiently reduced. According to the invention, the heat exchanger is arranged, and the liquid ammonia is cooled by utilizing the low-temperature gas ammonia gasified by flash evaporation, so that the cooling capacity in the gas ammonia can be effectively utilized, and the waste of the cooling capacity in the gas ammonia is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid ammonia refrigeration, and in particular to a flash evaporation device and method for twice cooling liquid ammonia in a liquid ammonia refrigeration process. Background Art

[0002] As a refrigerant, liquid ammonia has the advantages of low boiling point, moderate pressure, large refrigeration capacity per unit volume, small throttling loss, easy to detect dissolved water and leakage, and low price. The application of liquid ammonia in the refrigeration process achieves the refrigeration effect through a series of physical changes, that is, the compressor compresses the low-pressure ammonia vapor into high-pressure gas, the high-pressure gas enters the condenser and is cooled and converted into liquid ammonia, the liquid ammonia is depressurized by the throttle valve, and then enters the evaporator, absorbing heat in the process, thereby reducing the temperature of the surrounding environment, and the evaporated gaseous ammonia is sucked into the compressor again to complete the refrigeration cycle. Due to the different refrigeration methods adopted by the ammonia refrigeration system according to different application fields, such as direct evaporation refrigeration system or refrigerant indirect refrigeration system. Among them, direct evaporation refrigeration is that the liquid ammonia is depressurized and enters the flash tank, and the liquid ammonia is depressurized and vaporized in the flash tank to absorb heat and transform into gaseous ammonia flowing out of the flash tank. The liquid ammonia that has not been vaporized is reduced in temperature and then used as a refrigerant. However, in the process of flash evaporation, the liquid ammonia only relies on the pressure reduction to make part of the liquid ammonia vaporize and absorb heat to reduce the temperature of the liquid ammonia, and the refrigeration efficiency is not high. In addition, the ammonia gas after flash evaporation directly enters the compressor for compression. Since the temperature of this part of the ammonia gas is lowered, this part of the cooling capacity is not effectively utilized, resulting in a waste of cooling capacity. Summary of the invention

[0003] Based on the problems of the prior art, the present invention provides a flash evaporation device and method for twice cooling liquid ammonia in a liquid ammonia refrigeration process. The method greatly exerts the effect of liquid ammonia flash refrigeration, making the temperature of liquid ammonia obtained by flash evaporation lower, and also fully utilizes the cooling capacity of gaseous ammonia obtained by flash evaporation.

[0004] In order to solve the above technical problems, the technical solution of the present invention is as follows: A flash evaporation device for twice cooling liquid ammonia in a liquid ammonia refrigeration process comprises a flash tank and a heat exchanger, wherein the heat exchanger is arranged above the flash tank, and the heat exchanger is provided with a liquid ammonia inlet a, a liquid ammonia outlet a, a gaseous ammonia inlet a, and a gaseous ammonia outlet a; the liquid ammonia inlet b of the flash tank is connected to the liquid ammonia outlet a of the heat exchanger, and the gaseous ammonia outlet b of the flash tank is connected to the gaseous ammonia inlet a of the heat exchanger; the liquid ammonia outlet b is arranged at the bottom of the flash tank; a plurality of atomizing devices are arranged inside the flash tank, and the plurality of atomizing devices are connected to the liquid ammonia inlet b of the flash tank through pipelines.

[0005] Furthermore, a regulating valve is arranged on the branch pipeline connecting the plurality of atomizing devices and the liquid ammonia inlet b, and the regulating valve is arranged outside the flash tank shell.

[0006] Furthermore, the atomizing device is a rectangular shell structure or a cylindrical shell structure with a hollow interior or a combination structure with a plurality of branch pipes arranged on the main pipe. The upper shell of the atomizing device is provided with a liquid ammonia inlet, which is connected to the liquid ammonia inlet b, and the lower shell of the atomizing device is provided with a plurality of circular holes.

[0007] Furthermore, a plurality of circular holes are arranged on the lower shell of the atomizing device, and atomizing nozzles are arranged on the plurality of circular holes.

[0008] Furthermore, the heat exchanger is a plate heat exchanger or a shell and tube heat exchanger.

[0009] Furthermore, a liquid level meter is provided on the flash tank.

[0010] A method for twice cooling liquid ammonia in a liquid ammonia refrigeration process. The method is implemented on a flash evaporation device for twice cooling liquid ammonia. Liquid ammonia first enters a heat exchanger, and is cooled by gaseous ammonia flashed out of a flash evaporation tank in the heat exchanger. The liquid ammonia cooled in the heat exchanger enters the flash evaporation tank, and is atomized and flashed by an atomizing device in the flash evaporation tank. A part of the liquid ammonia is flashed and converted into gaseous ammonia, flows out of the flash evaporation tank and enters the heat exchanger, and the other part of the liquid ammonia is cooled and collected in the flash evaporation tank; the gaseous ammonia is heated in the heat exchanger and flows out of the heat exchanger.

[0011] Furthermore, the liquid level of liquid ammonia in the flash tank is lower than that of the atomizing device. Beneficial Effects

[0012] 1. In the flash tank disclosed in the prior art, liquid ammonia enters the flash tank, and the pressure is reduced, and the liquid ammonia flashes and vaporizes at the liquid ammonia surface to absorb heat. The heat exchange between liquid ammonia and gaseous ammonia occurs at the liquid ammonia surface, and the flash vaporization refrigeration effect is poor. The present invention provides an atomizing device to allow the flashed gaseous ammonia and the atomized liquid ammonia to fully contact and exchange heat in the space above the liquid ammonia surface inside the flash tank; compared with the flash tank disclosed in the prior art, the present invention has heat exchange between liquid ammonia and gaseous ammonia in the space above the liquid ammonia surface in the flash tank, a larger heat exchange area, and a better flash refrigeration effect, thereby being able to efficiently reduce the temperature of the liquid ammonia.

[0013] 2. The present invention provides a heat exchanger to utilize the low-temperature gaseous ammonia vaporized by flash gas to cool liquid ammonia, thereby effectively utilizing the cold energy in the gaseous ammonia and avoiding the waste of cold energy in the gaseous ammonia.

[0014] 3. The present invention realizes flow regulation of liquid ammonia atomization by arranging regulating valves on branch pipes connecting a plurality of atomizing devices with the liquid ammonia inlet b, flexibly adjusts the number of operating atomizing devices, and avoids poor atomization effect when the liquid ammonia flow is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A is a perspective schematic diagram of the internal structure of the flash tank of the present invention; Figure 2 b is a schematic diagram of the main structure of the flash tank of the present invention; Figure 3 c is a schematic diagram of the main structure of the flash tank of the present invention; Figure 4 The left side structural schematic diagram of the internal structure of the flash tank of the present invention is perspective; Figure 5 It is a bottom view structural schematic diagram of the atomizing device with a rectangular shell structure of the present invention; Figure 6 It is a bottom view structural schematic diagram of the atomizing device with a cylindrical shell structure of the present invention; Figure 7 It is a bottom view structural schematic diagram of a combined structure atomization device of the present invention in which a plurality of branch pipes are arranged on a main pipe; In the figure: 1-flash tank; 2-heat exchanger; 3-liquid ammonia inlet a; 4-gas ammonia outlet a; 5-liquid ammonia outlet a; 6-liquid ammonia inlet b; 7-gas ammonia outlet b; 8-gas ammonia inlet a; 9-atomizing device; 10-liquid ammonia outlet b; 11-circular small hole. DETAILED DESCRIPTION Example 1

[0016] Reference Figure 1 , Figure 4 , Figure 5 In order to make the flash evaporation of liquid ammonia achieve a better refrigeration effect and reduce the cooling loss caused by the flash evaporation of liquid ammonia as much as possible, the present invention provides a flash evaporation device for twice cooling liquid ammonia in a liquid ammonia refrigeration process, comprising a flash tank 1 and a heat exchanger 2, wherein the heat exchanger 2 is arranged above the flash tank 1, and the heat exchanger 2 is a shell and tube heat exchanger 2, wherein the heat exchanger 2 is provided with a liquid ammonia inlet a3, a liquid ammonia outlet a5, a gas ammonia inlet a8, and a gas ammonia outlet a4, wherein the liquid ammonia is passed through the tube side through the liquid ammonia inlet a3 and the liquid ammonia outlet a5, and the gas ammonia is passed through the shell side through the gas ammonia inlet a8 and the gas ammonia outlet a4, wherein the liquid ammonia inlet b6 of the flash tank 1 is connected to the liquid ammonia outlet a5 of the heat exchanger 2, and the gas ammonia outlet b7 of the flash tank 1 is connected to the gas ammonia inlet a8 of the heat exchanger 2; a liquid ammonia outlet b10 is arranged at the bottom of the flash tank 1; an atomizing device 9 is arranged inside the flash tank 1, and the atomizing device 9 is connected to the liquid ammonia inlet b6 of the flash tank 1 through a pipeline; The atomizing device 9 is a rectangular shell structure with a hollow interior. The upper shell of the atomizing device 9 is provided with a liquid ammonia inlet, which is connected to the liquid ammonia inlet b6. A plurality of circular holes 11 are provided on the lower shell of the atomizing device 9, through which the liquid ammonia is sprayed out and atomized. A liquid level gauge is provided on the flash tank 1 to detect the liquid level in the flash tank 1 to prevent the liquid level from being too high and submerging the atomizing device 9, thereby losing the atomizing effect.

[0017] A method for twice cooling liquid ammonia in a liquid ammonia refrigeration process. The method is implemented on a flash evaporation device for twice cooling liquid ammonia. Liquid ammonia first enters a heat exchanger 2, and is cooled by gaseous ammonia flashed out of a flash tank 1 in the heat exchanger 2. The liquid ammonia cooled in the heat exchanger 2 enters the flash tank 1, and is atomized and flashed by an atomizing device 9 in the flash tank 1. A part of the liquid ammonia is flashed and converted into gaseous ammonia, flows out of the flash tank 1 and enters the heat exchanger 2, and the other part of the liquid ammonia is cooled and collected in the flash tank 1; the gaseous ammonia is heated in the heat exchanger 2 and flows out of the heat exchanger 2; during operation, the liquid level in the flash tank 1 is controlled to be lower than the atomizing device 9. Example 2

[0018] Reference Figure 2 , Figure 4 , Figure 6 In order to achieve better refrigeration effect by flash evaporation of liquid ammonia and reduce the cooling loss caused by flash evaporation of liquid ammonia as much as possible, the present invention provides a flash evaporation device for twice cooling liquid ammonia in a liquid ammonia refrigeration process, comprising a flash tank 1 and a heat exchanger 2, wherein the heat exchanger 2 is arranged above the flash tank 1, and the heat exchanger 2 is a shell and tube heat exchanger 2, wherein the heat exchanger 2 is provided with a liquid ammonia inlet a3, a liquid ammonia outlet a5, a gaseous ammonia inlet a8, and a gaseous ammonia outlet a4, wherein the liquid ammonia is passed through the tube side through the liquid ammonia inlet a3 and the liquid ammonia outlet a5, and the gaseous ammonia is passed through the shell side through the gaseous ammonia inlet a8 and the gaseous ammonia outlet a4, and the liquid ammonia inlet b6 of the flash tank 1 and the heat exchanger 2 are connected to each other. The liquid ammonia outlet a5 is connected, and the gas ammonia outlet b7 of the flash tank 1 is connected to the gas ammonia inlet a8 of the heat exchanger 2; a liquid ammonia outlet b10 is arranged at the bottom of the flash tank 1; three atomizing devices 9 are arranged inside the flash tank 1, and the three atomizing devices 9 are connected with the liquid ammonia inlet b6 of the flash tank 1 through pipelines; a regulating valve is arranged on the branch pipeline connecting the three atomizing devices 9 with the liquid ammonia inlet b6, and the regulating valve is arranged outside the shell of the flash tank 1, and the atomizing effect of the atomizing device 9 is adjusted by the regulating valve to avoid poor atomization effect when the liquid ammonia flow rate is small. When the liquid ammonia flow rate is small, one atomizing device 9 is stopped and two atomizing devices 9 are operated.

[0019] The atomizing device 9 is a cylindrical shell structure with a hollow interior. The upper shell of the atomizing device 9 is provided with a liquid ammonia inlet, which is connected to the liquid ammonia inlet b6. A plurality of circular holes 11 are provided on the lower shell of the atomizing device 9, through which the liquid ammonia is sprayed out and atomized. A liquid level gauge is provided on the flash tank 1 to detect the liquid level in the flash tank 1 to prevent the liquid level from being too high to submerge the atomizing device 9 and thus lose the atomizing effect.

[0020] A method for twice cooling liquid ammonia in a liquid ammonia refrigeration process. The method is implemented on a flash evaporation device for twice cooling liquid ammonia. Liquid ammonia first enters a heat exchanger 2, and is cooled by gaseous ammonia flashed out of a flash tank 1 in the heat exchanger 2. The liquid ammonia cooled in the heat exchanger 2 enters the flash tank 1, and is atomized and flashed by an atomizing device 9 in the flash tank 1. A part of the liquid ammonia is flashed and converted into gaseous ammonia, flows out of the flash tank 1 and enters the heat exchanger 2, and the other part of the liquid ammonia is cooled and collected in the flash tank 1; the gaseous ammonia is heated in the heat exchanger 2 and flows out of the heat exchanger 2; during operation, the liquid level in the flash tank 1 is controlled to be lower than the atomizing device 9. Example 3

[0021] refer to Figure 3 , Figure 4 , Figure 7 In order to make the flash evaporation of liquid ammonia achieve a better refrigeration effect and reduce the cooling loss caused by the flash evaporation of liquid ammonia as much as possible, the present invention provides a flash evaporation device for twice cooling liquid ammonia in a liquid ammonia refrigeration process, comprising a flash tank 1 and a heat exchanger 2, wherein the heat exchanger 2 is arranged above the flash tank 1, and the heat exchanger 2 is a shell and tube heat exchanger 2, wherein the heat exchanger 2 is provided with a liquid ammonia inlet a3, a liquid ammonia outlet a5, a gaseous ammonia inlet a8, and a gaseous ammonia outlet a4, wherein the liquid ammonia is passed through the tube side through the liquid ammonia inlet a3 and the liquid ammonia outlet a5, and the gaseous ammonia is passed through the shell side through the gaseous ammonia inlet a8 and the gaseous ammonia outlet a4, and the liquid ammonia inlet b6 of the flash tank 1 and the liquid ammonia outlet b7 of the heat exchanger 2 are connected to each other. The ammonia outlet a5 is connected, and the gas ammonia outlet b7 of the flash tank 1 is connected to the gas ammonia inlet a8 of the heat exchanger 2; a liquid ammonia outlet b10 is arranged at the bottom of the flash tank 1; three atomizing devices 9 are arranged inside the flash tank 1, and the three atomizing devices 9 are connected with the liquid ammonia inlet b6 of the flash tank 1 through pipelines; a regulating valve is arranged on the branch pipeline connecting the three atomizing devices 9 with the liquid ammonia inlet b6, and the regulating valve is arranged outside the shell of the flash tank 1, and the atomizing effect of the atomizing device 9 is adjusted by the regulating valve to avoid poor atomization effect when the liquid ammonia flow rate is small. When the liquid ammonia flow rate is too small, two atomizing devices 9 are stopped and only one atomizing device 9 is operated.

[0022] The atomizing device 9 is a combination structure in which a plurality of branch pipes are arranged on a main pipe. A liquid ammonia inlet is arranged on the upper main pipe of the atomizing device 9, and the liquid ammonia inlet is connected with the liquid ammonia inlet b6. A plurality of circular holes 11 are arranged at the lower part of the branch pipe of the atomizing device 9, and liquid ammonia is sprayed out and atomized through the circular holes 11. A liquid level gauge is arranged on the flash tank 1 to detect the liquid level in the flash tank 1 to prevent the liquid level from being too high to submerge the atomizing device 9 and lose the atomizing effect.

[0023] A method for twice cooling liquid ammonia in a liquid ammonia refrigeration process. The method is implemented on a flash evaporation device for twice cooling liquid ammonia. Liquid ammonia first enters a heat exchanger 2, and is cooled by gaseous ammonia flashed out of a flash tank 1 in the heat exchanger 2. The liquid ammonia cooled in the heat exchanger 2 enters the flash tank 1, and is atomized and flashed by an atomizing device 9 in the flash tank 1. A part of the liquid ammonia is flashed and converted into gaseous ammonia, flows out of the flash tank 1 and enters the heat exchanger 2, and the other part of the liquid ammonia is cooled and collected in the flash tank 1; the gaseous ammonia is heated in the heat exchanger 2 and flows out of the heat exchanger 2; during operation, the liquid level in the flash tank 1 is controlled to be lower than the atomizing device 9.

[0024] Another embodiment is different from Embodiment 3 in that: the heat exchanger 2 is a plate heat exchanger 2; the atomizing device 9 is a combination structure in which a plurality of branch pipes are arranged on a main pipe; a liquid ammonia inlet is arranged on the upper main pipe of the atomizing device 9, and the liquid ammonia inlet is connected to the liquid ammonia inlet b6; a plurality of circular holes are arranged at the lower part of the branch pipe of the atomizing device 9, and atomizing nozzles are arranged on the plurality of circular holes, and the liquid ammonia is atomized by the atomizing nozzles.

[0025] The working principle of the present invention is: due to the flash tank 1 disclosed in the prior art, liquid ammonia enters the flash tank 1, and through the pressure reduction, the liquid ammonia flashes and vaporizes at the liquid ammonia surface to absorb heat, and the heat exchange between the liquid ammonia and the gaseous ammonia occurs at the liquid ammonia surface, and such flash vaporization refrigeration effect is poor. The present invention sets an atomizing device 9 so that the flashed gaseous ammonia and the atomized liquid ammonia are fully in contact with each other in the space above the liquid ammonia surface inside the flash tank 1 for heat exchange. Compared with the flash tank 1 disclosed in the prior art, the present invention has heat exchange between liquid ammonia and gaseous ammonia in the space above the liquid ammonia surface in the flash tank 1, and the heat exchange area is larger, and the flash refrigeration effect is better, so that the temperature of the liquid ammonia can be efficiently reduced; in addition, the present invention sets a heat exchanger 2 to use the low-temperature gaseous ammonia vaporized by flash vapor to cool the liquid ammonia, so that the cold in the gaseous ammonia can be effectively utilized, avoiding the waste of cold in the gaseous ammonia.

[0026] Modifications and changes to the present invention made by the inventors familiar with the present invention are all within the patent scope of the present invention and are not limited to the embodiments.

Claims

1. A flash evaporation device for twice cooling liquid ammonia in a liquid ammonia refrigeration process, characterized in that: The invention comprises a flash tank and a heat exchanger, wherein the heat exchanger is arranged above the flash tank, and is provided with a liquid ammonia inlet a, a liquid ammonia outlet a, a gaseous ammonia inlet a, and a gaseous ammonia outlet a. The liquid ammonia inlet b of the flash tank is connected to the liquid ammonia outlet a of the heat exchanger, and the gaseous ammonia outlet b of the flash tank is connected to the gaseous ammonia inlet a of the heat exchanger; the liquid ammonia outlet b is arranged at the bottom of the flash tank; a plurality of atomizing devices are arranged inside the flash tank, and the plurality of atomizing devices are connected to the liquid ammonia inlet b of the flash tank through pipelines.

2. The flash evaporation device for twice cooling liquid ammonia in a liquid ammonia refrigeration process according to claim 1, characterized in that: A regulating valve is arranged on the branch pipeline connecting the plurality of atomizing devices and the liquid ammonia inlet b, and the regulating valve is arranged outside the flash tank shell.

3. The flash evaporation device for twice cooling liquid ammonia in a liquid ammonia refrigeration process according to claim 1, characterized in that: The atomizing device is a rectangular shell structure with a hollow interior or a cylindrical shell structure or a combination structure in which a plurality of branch pipes are arranged on a main pipe; a liquid ammonia inlet is arranged on the upper shell of the atomizing device, the liquid ammonia inlet is connected to the liquid ammonia inlet b, and a plurality of circular small holes are arranged on the lower shell of the atomizing device.

4. The flash evaporation device for twice cooling liquid ammonia in a liquid ammonia refrigeration process according to claim 1, characterized in that: A plurality of circular holes are arranged on the lower shell of the atomizing device, and atomizing nozzles are arranged on the plurality of circular holes.

5. A flash evaporation device for twice cooling liquid ammonia in a liquid ammonia refrigeration process according to any one of claims 1 to 4, characterized in that: The heat exchanger is a plate heat exchanger or a shell and tube heat exchanger.

6. A flash evaporation device for twice cooling liquid ammonia in a liquid ammonia refrigeration process according to any one of claims 1 to 4, characterized in that: A liquid level meter is arranged on the flash tank.

7. A method for twice cooling liquid ammonia in a liquid ammonia refrigeration process, the method being implemented on a flash evaporation device for twice cooling liquid ammonia, characterized in that: Liquid ammonia first enters the heat exchanger, where it is cooled by the gaseous ammonia flashed out of the flash tank. The cooled liquid ammonia enters the flash tank, where it is atomized and flashed by an atomizing device. A portion of the liquid ammonia is flashed and converted into gaseous ammonia, which flows out of the flash tank and into the heat exchanger. The other portion of the liquid ammonia is cooled and collected in the flash tank. The gaseous ammonia is heated in the heat exchanger and flows out of the heat exchanger.

8. The method for twice cooling liquid ammonia in a liquid ammonia refrigeration process according to claim 7, characterized in that: The liquid level of the liquid ammonia in the flash tank is lower than that of the atomizing device.

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