Oil content circulation system based on transcritical carbon dioxide combined cooling and heating unit

Abstract

The invention discloses an oil circulation system based on a transcritical carbon dioxide combined cooling and heating unit, and relates to the technical field of oil-liquid separation of combined cooling and heating units. The oil separation circulating system comprises an oil storage tank which is communicated with an oil way system of the compressor unit through an oil storage pipe, and low-pressure lubricating oil obtained after oil separation treatment is conducted through a low-pressure oil separation tank and a liquid separation tank in the system enters the oil storage pipe and returns to the oil way system of the compressor unit. High-pressure lubricating oil obtained after oil separation treatment is conducted through the high-pressure oil separation tank in the system enters the oil storage tank. The oil separation device is arranged on the oil generation link involved in the transcritical carbon dioxide combined cooling and heating unit system, so that the whole system runs smoothly and effectively, the low-pressure oil separation tank is arranged before compression, the high-pressure oil separation tank is arranged after compression, and the liquid separation tank is arranged after pressure reduction; and an oil storage container for supplying oil to the compressor is used for recovering and reusing oil to form a set of oil path circulation.

Description

Technical Field

[0001] The invention belongs to the technical field of oil separation in refrigeration systems, and in particular relates to an oil separation circulation system based on a transcritical carbon dioxide combined cooling and heating unit. Background Art

[0002] Transcritical CO2 heat pump combined heat and cooling technology is a new energy utilization technology developed on the basis of CO2 heat pump. Its working principle is to realize both low-temperature heating and high-temperature cooling by circulating the working fluid near the critical point of CO2, thus achieving the purpose of combined heat and cooling.

[0003] After the gaseous CO2 enters the heat exchanger (heat exchange with liquid CO2 is carried out inside the heat exchanger), the temperature and pressure of the gaseous CO2 after the heat exchange will rise, and the gaseous CO2 entering the compressor will be mixed with oil and dirt (the oil and dirt may enter through the transmission pipeline, and there is less oil; the carbon dioxide compressed by the compressor becomes high-temperature and high-pressure transcritical carbon dioxide, and the lubricating oil is carried along due to the solubility of supercritical CO2. At this time, the transcritical CO2 and the lubricating oil are mixed (the mixed lubricating oil is more).

[0004] When carbon dioxide is used as a refrigerant, the system pressure is very high. The saturation pressure of carbon dioxide at 0℃ is 7 times higher than that of R22. Its suction and exhaust pressures are 10MPa and 3MPa higher than those of R22 respectively. It has abnormal solubility under supercritical pressure and shows its acidic nature when water is present. Under supercritical conditions, carbon dioxide is an effective solvent for various types of hydrocarbons. Because the exhaust of the carbon dioxide compressor is in a supercritical state, lubricant carryover will occur under any conditions due to the solubility of supercritical carbon dioxide. Lubricant provides effective power for the compressor within the system working state and temperature range without affecting the system's operating capacity. From the above characteristics of carbon dioxide and lubricant, it can be seen that the compressor lubricant and refrigerant must be miscible; otherwise, the lubricant will be deposited in the heat exchanger to form an oil film, which will not only affect the heat exchange effect but also cause the compressor to lack oil, causing a series of problems; and because no matter what the case, the carbon dioxide refrigeration compressor will produce lubricant carryover due to the solubility of supercritical carbon dioxide under supercritical conditions, so in order not to hinder heat transfer, it is necessary to ensure that the lubricant can return to the compressor. This makes it necessary to achieve oil separation.

[0005] Transcritical carbon dioxide cannot be separated from lubricating oil during the compression process. It is necessary to ensure that the lubricating oil returns to the compressor in time, otherwise the compressor will lose power and cannot work. More importantly, the lubricating oil must not be allowed to enter the refrigeration and heating links, otherwise it will cause pipeline blockage and affect the normal operation of the entire unit. Summary of the invention

[0006] The object of the present invention is to provide an oil circulation system based on a transcritical carbon dioxide combined heat and cold plant, and the problem of lubricating oil recovery and recycling in the transcritical carbon dioxide combined heat and cold plant system is solved by arranging the oil circulation system.

[0007] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0008] The present invention is an oil circulation system based on a transcritical carbon dioxide combined cooling and heating unit, comprising a refrigeration equipment end, a heat exchanger group, a compressor group, an oil storage tank and a heating equipment end, wherein the mixed gaseous CO2 outputted from the refrigeration equipment end is outputted to the heat exchanger group, and the mixed gaseous CO2 after heat exchange is subjected to oil separation treatment through a low-pressure oil separation tank by the heat exchanger group and then enters the compressor group, and the obtained gaseous CO2 is converted into a high-temperature and high-pressure transcritical CO2 mixture by the compressor group, and the high-temperature and high-pressure transcritical CO2 after oil separation treatment of the high-temperature and high-pressure transcritical CO2 passes through a high-pressure oil separation tank and enters the heating equipment end; the sub-high-temperature and high-pressure liquid CO2 outputted from the heating equipment end is outputted to the heat exchanger group for heat exchange, and the liquid CO2 after heat exchange and temperature reduction and pressure reduction enters a pressure reducer group for pressure reduction and forms low-temperature and low-pressure liquid CO2, and the low-temperature and low-pressure liquid CO2 passes through a liquid separation tank and then enters the refrigeration equipment end after oil separation treatment;

[0009] The oil storage tank is connected to the oil circuit system of the compressor unit through an oil storage pipe. The low-pressure lubricating oil obtained after oil separation through the low-pressure oil separator and the liquid separator in the system enters the oil storage pipe and returns to the oil circuit system of the compressor unit. The high-pressure lubricating oil obtained after oil separation through the high-pressure oil separator in the system enters the oil storage tank.

[0010] Among them, the working environment pressure of the low-pressure oil separator tank is in the range of 2.0-3.0MPa; the working environment pressure of the high-pressure oil separator tank is in the range of 8-10MPa; the working environment pressure of the liquid separator tank is in the range of 3-4MPa.

[0011] Furthermore, the compressor unit is an array of several compressors consisting of series-connected transcritical carbon dioxide compressors.

[0012] Furthermore, the liquid separation tank includes a first tank body, and a first air outlet, a first liquid inlet, a first filter screen, a first liquid outlet and a first oil outlet are sequentially arranged from the top to the bottom of the first tank body; low-temperature and low-pressure liquid CO2 enters through the first liquid inlet, passes through the first filter screen located inside the first tank body, and is output to the refrigeration equipment end through the first liquid outlet, and the separated lubricating oil enters the oil storage pipe through the first oil outlet.

[0013] Furthermore, the high-pressure oil separator tank includes a second tank body, on which a second liquid outlet, a plurality of second liquid inlets, a first bell-mouth fluid structure located inside the second tank body, a second filter screen, a second oil outlet and a first sewage outlet are sequentially arranged from the top to the bottom of the second tank body, and one second liquid inlet corresponds to a group of compressor arrays; a high-temperature and high-pressure transcritical CO2 mixture enters through the second liquid inlet of the high-pressure oil separator tank, and the high-temperature and high-pressure transcritical CO2 formed in the second tank body is collected through the first bell-mouth fluid structure and flows out through the second liquid outlet, and the high-pressure lubricating oil in the second tank body enters the oil storage tank through the second oil outlet.

[0014] Furthermore, the low-pressure oil separation tank includes a third tank body, which is provided with a second air outlet, a second bell-mouth fluid structure located inside the third tank body, an air inlet, a third filter screen and a third oil outlet in sequence from the top to the bottom of the third tank body. The mixed gaseous CO2 enters the third tank body through the air inlet, the gaseous CO2 is collected through the second bell-mouth fluid structure, enters the compressor unit through the second air outlet, and the low-pressure lubricating oil inside the third tank body enters the oil storage tank through the third oil outlet.

[0015] Furthermore, the refrigeration equipment end includes an air cooler, and the air cooler adopts a carbon dioxide heat exchanger.

[0016] Furthermore, the heating equipment end includes a flash dryer or a flash water condenser.

[0017] Furthermore, the pressure reducer group is a capillary pressure reducer.

[0018] Furthermore, the heat exchanger group is a plate exchanger.

[0019] Furthermore, the working environment pressure of the oil storage tank is in the range of 3.5-6MPa.

[0020] The present invention has the following beneficial effects:

[0021] 1. The present invention installs an oil separation device at the link where oil appears in the transcritical carbon dioxide combined heat and cold supply unit system, so that the entire system can run smoothly and effectively. A low-pressure oil separation tank is set before compression, a high-pressure oil separation tank is set after compression, a liquid separation tank is set after decompression, and an oil storage container for supplying oil to the compressor is used to recover and reuse the oil to form an oil circuit circulation.

[0022] 2. The oil circulation system of the present invention makes it unnecessary to add new lubricating oil to the oil storage tank of the device system, thereby reducing the equipment maintenance of the device, avoiding system oil pollution, and improving the operating efficiency of the equipment.

[0023] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0025] Figure 1 This is a diagram of the oil circulation system based on the transcritical carbon dioxide combined cooling and heating unit of the present invention;

[0026] Figure 2 It is a structural schematic diagram of the liquid separation tank;

[0027] Figure 3 for Figure 2 Schematic diagram of the half-section structure in the transverse direction;

[0028] Figure 4 for Figure 2 Schematic diagram of the half-section structure in the longitudinal direction;

[0029] Figure 5 It is a structural schematic diagram of the high-pressure oil separator tank;

[0030] Figure 6 for Figure 5 Schematic diagram of the half-section structure;

[0031] Figure 7 It is a structural schematic diagram of the low-pressure oil separator tank;

[0032] Figure 8 for Figure 7 Schematic diagram of the half-section structure. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention / invention, rather than all 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.

[0034] During the operation of the entire system, it is necessary to know where the oil eventually flows. After a large number of experiments, it is known that most of the oil is concentrated in the oil separator tank, so an oil-liquid separation device is installed in the oil separator tank. Separation devices are also installed at the links where oil may appear, so that the entire system can run smoothly and effectively. Separation devices are installed in three places in the unit, a low-pressure oil separator tank before compression, a high-pressure oil separator tank after compression, a liquid separator tank after decompression, and an oil storage tank that supplies oil to the compressor.

[0035] All kinds of tank containers use vertical separation containers. The principle is to rely on gravity to precipitate liquid or separate liquid from gas. The so-called gravity separator is when the droplet is no longer accelerated, it falls at a steady speed, which is called the terminal velocity. At this speed, all forces acting on the droplet are in a state of equilibrium, that is, resistance and buoyancy balance gravity. The liquid that does not fall to the bottom of the separation container is like some stationary small droplets in the white clouds in the sky. The reason why they are suspended in the sky and do not fall down as raindrops is that their diameter is not large enough (not enough mass) to fall down, but is supported by the buoyancy of the air, and is not small enough to be evaporated by the sun or blown away by the wind. The diameter of this droplet is defined as the critical diameter of the droplet for the calculation separation of a certain refrigerant. In the refrigeration system, as the temperature drops, the mass of the refrigerant droplet of the same diameter will increase (the lower the temperature, the greater the density of the refrigerant), and the rising speed of the droplet can also increase. That is, the separation speed can be increased, and the separation capacity is also increased. This is why the separation capacity changes with the decrease of the evaporation temperature. The separation structure of the tank is designed based on the above principles.

[0036] like Figure 1 As shown, an oil separation circulation system based on a transcritical carbon dioxide combined heat and cold supply unit includes a refrigeration equipment end, a heat exchanger group, a compressor group, an oil storage tank and a heating equipment end. The mixed gaseous CO2 output from the refrigeration equipment end is output to the heat exchanger group. The mixed gaseous CO2 after heat exchange is processed by oil separation in a low-pressure oil separation tank through the heat exchanger group and then enters the compressor group. The obtained gaseous CO2 is converted into a high-temperature and high-pressure transcritical CO2 mixture through the compressor group. The high-temperature and high-pressure transcritical CO2 mixture is processed by oil separation in a high-pressure oil separation tank and then enters the heating equipment end; the sub-high-temperature and high-pressure liquid CO2 output from the heating equipment end is output to the heat exchanger group for heat exchange. The cooled and depressurized liquid CO2 after heat exchange enters a pressure reducer group for decompression and forms low-temperature and low-pressure liquid CO2. The low-temperature and low-pressure liquid CO2 enters the refrigeration equipment end after oil separation through a liquid separation tank.

[0037] The oil storage tank is connected to the oil circuit system of the compressor unit through an oil storage pipe. The low-pressure lubricating oil obtained after oil separation through the low-pressure oil separator and the liquid separator in the system enters the oil storage pipe and returns to the oil circuit system of the compressor unit. The high-pressure lubricating oil obtained after oil separation through the high-pressure oil separator in the system enters the oil storage tank.

[0038] Among them, the working environment pressure of the low-pressure oil separator is in the range of 2.0-3.0MPa; the working environment pressure of the high-pressure oil separator is in the range of 8-10MPa; the working environment pressure of the liquid separator is in the range of 3-4MPa, and the working environment pressure of the oil storage tank is in the range of 3.5-6MPa. Since the overall oil circuit system operates under the system pressure, the oil circuit of the oil storage tank can flow by relying on the pressure of the transcritical carbon dioxide combined cooling and heating unit system, without the need for additional oil pumps, which effectively reduces the equipment cost.

[0039] The compressor unit is an array of several compressors composed of series-connected transcritical carbon dioxide compressors, generally one compressor array or two compressor arrays, and the number of compressor arrays is increased or decreased according to the power of the equipment.

[0040] like Figure 2-4 As shown, the liquid separator tank includes a first tank body 1, and a first air outlet 103, a first liquid inlet 101, a first filter screen 106, a first liquid outlet 102 and a first oil outlet 104 are sequentially arranged from the top to the bottom of the first tank body 1; low-temperature and low-pressure liquid CO2 with lubricating oil enters through the first liquid inlet 101, passes through the first filter screen 106 located inside the first tank body 1, and is output to the refrigeration equipment end through the first liquid outlet 102, and the separated lubricating oil enters the oil storage pipe through the first oil outlet 104.

[0041] The first air outlet 103 is located at the top of the first tank body 1 , and the function of the first air outlet 103 is to adjust the pressure inside the first tank body 1 , so as to keep the pressure inside the first tank body 1 lower than the pressure of the first liquid inlet 101 and higher than the pressure of the liquid outlet.

[0042] A first observation mirror 105 is also provided on the side of the first tank body 1 for observing the position of the liquid carbon dioxide in the liquid separation tank container.

[0043] like Figure 5-6 As shown, the high-pressure oil separator tank includes a second tank body 2, on which a second liquid outlet 201, a plurality of second liquid inlets 202, a first bell-mouth fluid structure 205 located inside the second tank body 2, a second filter screen 206, a second oil outlet 207 and a first sewage outlet 204 are sequentially arranged from the top to the bottom of the second tank body 2, and one second liquid inlet 202 corresponds to a group of compressor arrays; a high-temperature and high-pressure transcritical CO2 mixture enters through the second liquid inlet 202 of the high-pressure oil separator tank, and the high-temperature and high-pressure transcritical CO2 formed in the second tank body 2 is collected through the first bell-mouth fluid structure 205 and flows out through the second liquid outlet 201, and the high-pressure lubricating oil in the second tank body 2 enters the oil storage tank through the second oil outlet 207.

[0044] The first bell-mouth fluid structure 205 is connected to the second liquid outlet 201. The first drain port 204 is at the bottom of the high-pressure oil separator tank to remove the accumulated oil impurities. At the same time, it is convenient to empty the oil and relieve the pressure of the unit during the later maintenance and repair. The second oil outlet 207 is at the bottom of the high-pressure oil separator tank. After separation, the lubricating oil returns from the oil outlet to the oil inlet of the oil storage tank to replenish the oil to the compressor unit. The second oil outlet 207 is connected to the oil inlet of the oil storage tank.

[0045] A second observation mirror 203 is also provided at the bottom of the second tank body 2 for observing the position of the lubricating oil, using the refractive surface of a prism.

[0046] The function of the second filter screen 206 is to completely separate transcritical carbon dioxide and lubricating oil.

[0047] The first bell-mouth fluid structure 205 is above the interior of the second tank body 2. Since the density of the compressed supercritical carbon dioxide is less than that of the lubricating oil, the oil-liquid mixture entering the second tank body 2, under the influence of gravity, has a speed of the lubricating oil greater than the falling speed of the supercritical CO2. Since the dynamic pressure of the gas flow is formed inside the second filter screen 206, its upward flow forms an upward thrust. Since the volume mass of the supercritical carbon dioxide is small, it will be deposited on the upper part of the second tank body 2. At this time, the upper part of the screen of the second tank body 2 is an upward gas flow, and the supercritical CO2 will be concentrated on the top of the second tank body 2. At the same time, the supercritical carbon dioxide enters from the side and flows along the wall. The contact area and volume are from large to small, forming a vortex, and the fluid will move upward. Since the fluid structure is similar to a trumpet-shaped mechanism, it has an effect similar to a vacuum cleaner. Therefore, according to the movement trajectory of the fluid, the separated transcritical carbon dioxide will come out from the top.

[0048] like Figure 7-8 As shown, the low-pressure oil separator includes a third tank body 3, on which a second air outlet 301, a second bell-mouth fluid structure 305 located inside the third tank body 3, an air inlet 302, a third filter screen 306 and a third oil outlet 304 are sequentially arranged from the top to the bottom of the third tank body 3. The mixed gaseous CO2 enters the third tank body 3 through the air inlet 302, the gaseous CO2 is collected through the second bell-mouth fluid structure 305, enters the compressor unit through the second air outlet 301, and the low-pressure lubricating oil inside the third tank body 3 enters the oil storage tank through the third oil outlet 304.

[0049] A third observation mirror 303 is also provided at the bottom of the third tank body 3 for observing the position of the lubricating oil, using the refractive surface of a prism.

[0050] The function of the third filter screen 306 is to completely separate the gaseous CO2 and the lubricating oil.

[0051] The refrigeration equipment end includes an air cooler, which is a carbon dioxide heat exchanger for cooling. The heating equipment end includes a flash dryer or a flash water condenser for heating. The pressure reducer group is a capillary pressure reducer. The heat exchanger group is a plate exchanger.

[0052] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0053] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An oil circulation system based on a transcritical carbon dioxide combined cooling and heating unit includes a refrigeration equipment end, a heat exchanger unit, a compressor unit, an oil storage tank and a heating equipment end, characterized in that: The mixed gaseous CO2 outputted from the refrigeration equipment end is outputted to the heat exchanger group, and the mixed gaseous CO2 after heat exchange is processed by oil separation in a low-pressure oil separator tank through the heat exchanger group and then enters the compressor group, and the obtained gaseous CO2 is converted into a high-temperature and high-pressure transcritical CO2 mixture through the compressor group, and the high-temperature and high-pressure transcritical CO2 mixture is processed by oil separation in a high-pressure oil separator tank and then enters the heating equipment end; The sub-high temperature and high pressure liquid CO2 outputted from the heating equipment end is outputted to the heat exchanger group for heat exchange, and the cooled and depressurized liquid CO2 after heat exchange enters a pressure reducer group for decompression and forms low temperature and low pressure liquid CO2, and the low temperature and low pressure liquid CO2 enters the refrigeration equipment end after oil separation treatment in the liquid separator tank; The oil storage tank is connected to the oil circuit system of the compressor unit through an oil storage pipe. The low-pressure lubricating oil obtained after oil separation through the low-pressure oil separator and the liquid separator in the system enters the oil storage pipe and returns to the oil circuit system of the compressor unit. The high-pressure lubricating oil obtained after oil separation through the high-pressure oil separator in the system enters the oil storage tank. Among them, the working environment pressure of the low-pressure oil separator tank is in the range of 2.0-3.0MPa; the working environment pressure of the high-pressure oil separator tank is in the range of 8-10MPa; the working environment pressure of the liquid separator tank is in the range of 3-4MPa.

2. The oil circulation system based on the transcritical carbon dioxide combined cooling and heating unit according to claim 1, characterized in that: The compressor unit is an array of several compressors consisting of series-connected transcritical carbon dioxide compressors.

3. The oil circulation system based on the transcritical carbon dioxide combined cooling and heating unit according to claim 1 or 2, characterized in that: The liquid separation tank comprises a first tank body (1), and a first gas outlet (103), a first liquid inlet (101), a first filter screen (106), a first liquid outlet (102) and a first oil outlet (104) are sequentially arranged from the top to the bottom of the first tank body (1); low-temperature and low-pressure liquid CO2 enters through the first liquid inlet (101), passes through the first filter screen (106) located inside the first tank body (1), and is output to the refrigeration equipment end through the first liquid outlet (102); the separated lubricating oil enters the oil storage pipe through the first oil outlet (104).

4. The oil circulation system based on the transcritical carbon dioxide combined cooling and heating unit according to claim 2, characterized in that: The high-pressure oil separator tank comprises a second tank body (2), wherein a second liquid outlet (201), a plurality of second liquid inlets (202), a first bell-mouth fluid structure (205) located inside the second tank body (2), a second filter screen (206), a second oil outlet (207) and a first sewage outlet (204) are sequentially arranged from the top to the bottom of the second tank body (2), and one second liquid inlet (202) corresponds to a group of compressor arrays; The high-temperature and high-pressure transcritical CO2 mixture enters through the second liquid inlet (202) of the high-pressure oil separator tank, the high-temperature and high-pressure transcritical CO2 formed in the second tank body (2) is collected through the first bell-mouth fluid structure (205) and flows out through the second liquid outlet (201), and the high-pressure lubricating oil in the second tank body (2) enters the oil storage tank through the second oil outlet (207).

5. The oil circulation system based on the transcritical carbon dioxide combined cooling and heating unit according to claim 1, characterized in that: The low-pressure oil separator tank comprises a third tank body (3), wherein a second air outlet (301), a second bell-mouth fluid structure (305) located inside the third tank body (3), an air inlet (302), a third filter screen (306) and a third oil outlet (304) are sequentially arranged from the top to the bottom of the third tank body (3); mixed gaseous CO2 enters the interior of the third tank body (3) through the air inlet (302); the gaseous CO2 is collected through the second bell-mouth fluid structure (305) and enters the compressor unit through the second air outlet (301); and the low-pressure lubricating oil located inside the third tank body (3) enters the oil storage tank through the third oil outlet (304).

6. The oil circulation system based on the transcritical carbon dioxide combined cooling and heating unit according to claim 1, characterized in that: The refrigeration equipment end includes an air cooler, and the air cooler adopts a carbon dioxide heat exchanger.

7. The oil circulation system based on the transcritical carbon dioxide combined cooling and heating unit according to claim 1, characterized in that: The heating equipment end includes a flash dryer or a flash water condenser.

8. The oil circulation system based on the transcritical carbon dioxide combined cooling and heating unit according to claim 1, characterized in that: The pressure reducer group is a capillary pressure reducer.

9. The oil circulation system based on the transcritical carbon dioxide combined cooling and heating unit according to claim 1, characterized in that: The heat exchanger group is a plate exchanger.

10. The oil circulation system based on the transcritical carbon dioxide combined cooling and heating unit according to claim 1, characterized in that: The working environment pressure of the oil storage tank is in the range of 3.5-6MPa.

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