Air compressor waste heat comprehensive utilization system and operation method thereof

Abstract

The embodiment of the present invention discloses a system for comprehensive utilization of waste heat of an air compressor and its operation method. The system for comprehensive utilization of waste heat of an air compressor comprises: an air compressor, which generates heat during operation; a heat recovery unit, which is connected to the air compressor through a pipeline, and the heat recovery unit is used to recover the heat generated by the air compressor and heat softened circulating water; a first heat exchanger, which is connected to the heat recovery unit through a pipeline, and the first heat exchanger uses the softened circulating water to produce hot water for bathing; a fresh air unit, which is connected to the heat recovery unit through a pipeline, and the fresh air unit uses the softened circulating water to heat fresh air; a heating water pipeline, which is connected to the heat recovery unit, and the heating water pipeline uses the softened circulating water for building heating. Compared with the prior art, the embodiment of the present invention reduces the energy consumption of key energy-consuming enterprises such as coal enterprises and achieves energy conservation and emission reduction.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of mining energy-saving technology, and in particular to an air compressor waste heat comprehensive utilization system and an operation method thereof. Background Art

[0002] How to reduce energy consumption of key energy-consuming enterprises such as coal enterprises and achieve energy conservation and emission reduction has become an urgent problem to be solved. Summary of the invention

[0003] The embodiment of the present invention provides an air compressor waste heat comprehensive utilization system and an operation method thereof, so as to reduce the energy consumption of key energy-consuming enterprises such as coal enterprises and achieve energy conservation and emission reduction.

[0004] In a first aspect, an embodiment of the present invention provides an air compressor waste heat comprehensive utilization system, comprising:

[0005] An air compressor that generates heat during operation;

[0006] A heat recovery unit is connected to the air compressor through a pipeline, and is used to recover the heat generated by the air compressor to heat and soften circulating water;

[0007] A first heat exchanger is connected to the heat recovery unit through a pipeline, and the first heat exchanger uses the softened circulating water to produce hot water for bathing;

[0008] A fresh air unit is connected to the heat recovery unit through a pipeline, and the fresh air unit uses the softened circulating water to heat the fresh air;

[0009] A heating water pipeline is connected to the heat recovery unit, and the heating water pipeline utilizes the softened circulating water for building heating.

[0010] Optionally, the air compressor waste heat comprehensive utilization system also includes: an air source heat pump, which is connected to the heat recovery unit through a pipeline; the air source heat pump is a backup heat source for the heat recovery unit.

[0011] Optionally, the air compressor is an oil-injected screw air compressor; the air compressor includes a filter, a motor, a body, an oil-gas separator, a thermostat, an oil filter, an oil cooler, an air cooler, a lubricating oil pipeline, an oil-gas mixture pipeline, and a compressed air pipeline;

[0012] Wherein, the motor and the machine body are connected via a drive shaft;

[0013] The filter is fixedly connected to the body, and the filter is used to filter air and draw the air into the body;

[0014] The engine body and the oil-gas separator are connected via the oil-gas mixture pipeline; the oil-gas separator is used to separate oil and gas from the oil-gas mixture generated by the engine body;

[0015] The oil-gas separator and the heat recovery unit are connected via the lubricating oil pipeline; the heat recovery unit is used to recover the heat in the lubricating oil and heat the softened circulating water;

[0016] The thermostat and the heat recovery unit are connected via the lubricating oil pipeline; the thermostat is used to detect the temperature of the lubricating oil;

[0017] The oil cooler and the temperature controller are connected via the lubricating oil pipeline; the oil cooler is used to cool the lubricating oil exceeding a preset temperature;

[0018] The oil filter and the oil cooler are connected via the lubricating oil pipeline, and the oil filter and the thermostat are connected via the lubricating oil pipeline; the oil filter is used to filter the lubricating oil cooled by the oil cooler and the lubricating oil not cooled by the oil cooler;

[0019] The engine body and the oil filter are connected via the lubricating oil pipeline;

[0020] The air cooler and the oil-gas separator are connected via the compressed air pipeline; the air cooler is used to generate compressed air.

[0021] Optionally, the air compressor further includes: a gate valve connected between the oil-gas separator and the temperature controller.

[0022] Optionally, the air compressor waste heat comprehensive utilization system also includes a tap water tank and a hot water tank, the tap water tank and the hot water tank are connected by a pipeline, and the first heat exchanger is arranged in the hot water tank.

[0023] Optionally, the air compressor waste heat comprehensive utilization system also includes: a thermocouple and a bathing circulating water pump; the bathing circulating water pump is arranged in the pipeline between the hot water tank and the heat recovery unit, and the bathing circulating water pump is used to control the heat exchange amount of the hot water tank; the thermocouple is arranged in the hot water tank, and the thermocouple is used to control the working state of the bathing circulating water pump according to the temperature of the hot water.

[0024] Optionally, the air compressor waste heat comprehensive utilization system further includes: a drying circulation water pump, the drying circulation water pump is arranged in a pipeline between the fresh air unit and the heat recovery unit, and the drying circulation water pump is used to control the heat exchange amount of the fresh air unit;

[0025] Optionally, the fresh air unit includes:

[0026] A surface cooler is connected to the heat recovery unit through a pipeline, and the surface cooler uses the heat recovered by the heat recovery unit to heat the fresh air;

[0027] A blower, located at the air outlet of the fresh air unit, and used to send out fresh air;

[0028] An exhaust fan is located at the return air outlet of the fresh air unit, and is used to send out the return air;

[0029] The return air heat recovery device is located between the exhaust fan and the return air duct, and the return air heat recovery device uses the heat of the return air to heat the fresh air.

[0030] In a second aspect, an embodiment of the present invention further provides an operation method of an air compressor waste heat comprehensive utilization system as described in any embodiment of the present invention, comprising:

[0031] Determine boundary conditions; the boundary conditions include: waste heat resources of the air compressor and external application load conditions;

[0032] Determine a configuration and operation model; the configuration and operation model includes: a cost objective function and equipment operation constraints;

[0033] Solving the equipment operation mode includes solving the operation mode of each device in the air compressor waste heat comprehensive utilization system according to the determined boundary conditions and the configuration and operation model.

[0034] Optionally, the waste heat resources of the air compressor include: parameters of the air compressor, the number of the air compressors and the operating rules of the air compressors;

[0035] The external application load conditions include: building heating heat load, bathing water heat load and hanging basket clothes drying heat load. Optionally, the total heat that can be recycled by the air compressor is calculated by the following formula:

[0036] W=W s +Q ds

[0037] Where, W is the power of the motor; W s is the shaft work required for the actual compression process; Q ds The heat loss is caused by the mechanical friction of the motor;

[0038] Q ds =W×(1-η D )

[0039] Among them, η D is the mechanical efficiency of the motor;

[0040] W s =Q bs +Qks +Q kq +Q ys

[0041] Among them, Q bs Q is the heat dissipation of the equipment’s outer surface; ks The heat carried away by the circulating cooling water in the air cooler; Q kq The heat brought by the air itself; Q ys It is the heat taken away by the circulating cooling water in the oil cooler;

[0042] Q bs =Q jt +Q yt +Q yl +Q kl

[0043] Among them, Q jt Q is the heat dissipation of the outer surface of the machine; yt Q is the heat dissipation of the oil-gas separator and its outer surface of the pipeline; yl is the heat dissipation of the outer surface of the oil cooler; Q kl The heat dissipation of the outer surface of the air cooler;

[0044] Q=k×A×ΔT

[0045] Where Q is the heat dissipation of the component's outer surface; k is the component's surface heat transfer coefficient / (m 2 ·K); A is the heat dissipation area of ​​the component's outer surface; ΔT is the average temperature difference between the hot and cold fluids on the inside and outside of the component's surface;

[0046] m a (h B -h C )=Q kl +Q ks +Q ln

[0047] Among them, m a is the mass flow rate of dry air in wet air; h B is the enthalpy of the wet air at the air cooler inlet; h C is the enthalpy of wet air at the air cooler outlet; Q ln The heat released by the condensation of water vapor in the humid air in the air cooler;

[0048] h=1.01×T+d×(2501+1.85×T)

[0049] Where, h is the enthalpy of moist air; T is the temperature of moist air; d is the moisture content of moist air;

[0050]

[0051] in, is the relative humidity of moist air; p s is the saturated partial pressure of water vapor; p is the absolute pressure of moist air;

[0052] Q ln =m a ×(d B -d C )×γ

[0053] Among them, d B is the humidity content of the wet air at the air cooler inlet; d C is the humidity content of the wet air at the outlet of the air cooler; γ is the latent heat of vaporization of saturated water;

[0054] Q ks =m a (h B -h C )-Q bs,kl -Q ln

[0055] Q kq =m a ×[1.01×(T C -T A )+1.85×d C ×(T C -T A )]

[0056] Among them, T C is the wet air temperature at the air cooler outlet; T A is the filter inlet wet air temperature;

[0057] Q ys =WQ ds -Q bs -Q ks -Q kq

[0058] Q hs =Q ks +Q ys +Q ln

[0059] Among them, Q hs It is the total heat that can be recovered by the air compressor.

[0060] Optionally, the building heating load is calculated by the following formula:

[0061] Q cn =S×q×10 -3

[0062] Among them, Q cnis the building heating heat load; S is the building area of ​​the heating building; q is the building heating heat index;

[0063] The bathing water heat load is calculated by the following formula:

[0064] Q xy =c xs ×m xs ×(T sh -T sq )

[0065] Among them, Q xy is the heat load of bathing water; c xs is the specific heat capacity of tap water at constant pressure; m xs is the amount of bath water; T sh is the bathing water supply temperature; T sq The temperature of tap water before heating;

[0066] The heat load of the hanging basket clothes drying is calculated by the following formula:

[0067] Q hg =c xf ×ρ xf ×V xf ×(T xh -T xq )

[0068] Among them, Q hg Heat load for clothes drying; c xf is the constant pressure specific heat capacity of fresh air; ρ xf is the fresh air density; V xf is the fresh air volume flow rate; T xh The temperature of the fresh air after heating; T xq The temperature of fresh air before heating.

[0069] Optionally, the cost objective function includes: annual electricity cost, annual maintenance cost, annual equivalent cost of initial investment and annual labor cost;

[0070] The equipment operation constraint conditions include: equipment capacity constraint, equipment operation characteristic constraint and system energy flow balance constraint.

[0071] Optionally, the cost objective function is calculated by the following formula:

[0072]

[0073] Among them, Z is the total annual cost of the system; i is the main type of equipment; k is the time period, and the whole year is divided into K time periods in total; is the electricity price; D is the duration of each period throughout the year; x KR is the input electrical power of the air source heat pump; xFZ is the input power of power-consuming auxiliary equipment including water pumps and fans; α is the ratio of annual maintenance fee to the annual equivalent fee of initial investment; β is the ratio of annual labor cost to the annual equivalent fee of initial investment; γ is the ratio of engineering cost to equipment cost; τ is the ratio of auxiliary equipment cost to main equipment cost; R is the capital investment recovery coefficient; c is the unit capacity cost of main equipment; M is the total capacity of main equipment.

[0074] Optionally, the device capacity constraint is calculated using the following formula:

[0075]

[0076] in, is the theoretical capacity of a single heat recovery unit; η ys is the heat exchange efficiency of the air compressor oil cooler; η rh is the heat exchange efficiency of the heat recovery unit; m rh is the capacity of a single heat recovery unit; ξ rh is the long-term output attenuation coefficient of the heat recovery unit; n rh The number of heat recovery units installed; n ky The number of air compressors installed; M rh is the total capacity of the heat recovery unit;

[0077]

[0078] in, is the theoretical total capacity of the air source heat pump; L ky is the average annual operating load rate of the air compressor; is the number of air compressors in operation; m kr is the capacity of a single air source heat pump on the market; n kr The number of air source heat pumps installed; M kr is the total capacity of the air source heat pump;

[0079]

[0080] in, is the theoretical total capacity of the fresh air unit; M xf is the total capacity of the fresh air unit; xf is the long-term output attenuation coefficient of the fresh air unit; m xf is the capacity of a single fresh air unit; n xf The number of fresh air units installed;

[0081]

[0082] in, is the theoretical total capacity of the closed self-cleaning heat exchanger; M bhis the total capacity of the closed self-cleaning heat exchanger; bh m is the long-term operation output attenuation coefficient of the closed self-cleaning heat exchanger; bh is the capacity of a single closed self-cleaning heat exchanger; n bh The number of closed self-cleaning heat exchangers installed;

[0083] The equipment operating characteristic constraints are calculated by the following formula:

[0084]

[0085] Among them, y is the output energy power of the equipment; p and q are the performance parameters of the equipment; x is the input energy power of the main equipment; δ is an integer variable, indicating the number of equipment in operation; x is the upper and lower limits of the energy power input of a single device; n is the number of devices installed;

[0086] The energy flow balance constraints of the system include heat balance of air compressor lubricating oil, heat balance of softening circulating water, heat balance of hanging basket clothes drying and heat balance of bathing water;

[0087] The heat balance of the air compressor lubricating oil is calculated by the following formula:

[0088]

[0089] Among them, x rh is the input heat power of the heat recovery unit;

[0090] The softening circulating water heat balance is calculated by the following formula:

[0091]

[0092] Among them, y kr is the output heat power of the air source heat pump; rh is the output heat power of the heat recovery unit; x xf is the input heat power of the fresh air unit; x bh is the input heat power of the closed self-cleaning heat exchanger;

[0093] The heat balance of the hanging basket clothes drying is calculated by the following formula:

[0094]

[0095] Among them, y xf is the output heat power of the fresh air unit;

[0096] The bath water heat balance is calculated by the following formula:

[0097]

[0098] Among them, y bh It is the output heat power of closed self-cleaning heat exchanger.

[0099] Optionally, the operation mode of the equipment includes: the type of operating equipment, the number of operating equipment, the capacity of the operating equipment and the operation law of the equipment.

[0100] The embodiment of the present invention considers using the waste heat of the air compressor to meet the heat needs of bathing water production, building heating, hanging basket clothes drying, etc., and there are rich ways to utilize the waste heat, which is conducive to the comprehensive utilization of the waste heat of the air compressor. The embodiment of the present invention does not need to consume primary energy such as natural gas and coal, has no direct pollutant emissions, and has the advantages of high degree of automation and good clothes drying effect. In addition, the embodiment of the present invention can reduce the use of boilers, which is conducive to avoiding the problems of low thermal efficiency, direct pollutant emissions, and waste of resources in coal-fired boilers; it is conducive to avoiding the problems of high nitrogen oxide emissions, high operating costs, explosion accidents during the start-up and shutdown of the furnace, and difficulty in ensuring stable supply in gas boilers; it is conducive to avoiding the application of electric boilers being limited by the power capacity of coal mines and high operating costs. Therefore, the embodiment of the present invention reduces the energy consumption of key energy-consuming enterprises such as coal enterprises, and is conducive to achieving energy conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Figure 1 A structural schematic diagram of an air compressor waste heat comprehensive utilization system provided by an embodiment of the present invention;

[0102] Figure 2 A schematic diagram of the structure of the connection between an air compressor and a heat recovery unit provided in an embodiment of the present invention;

[0103] Figure 3 A structural schematic diagram of another air compressor waste heat comprehensive utilization system provided by an embodiment of the present invention;

[0104] Figure 4 A schematic flow chart of an operation method of an air compressor waste heat comprehensive utilization system provided by an embodiment of the present invention;

[0105] Figure 5 A line graph of the output of an air source heat pump during each period of operation throughout the year provided by an embodiment of the present invention;

[0106] Figure 6 A line graph of the number of air source heat pumps that are turned on and running throughout the year provided by an embodiment of the present invention;

[0107] Figure 7 A line graph of the load rate of an air source heat pump running throughout the year provided by an embodiment of the present invention;

[0108] Figure 8A line graph of the annual power output of a fresh air unit provided by an embodiment of the present invention;

[0109] Fig. 9 A line graph of the annual startup load rate of a fresh air unit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0110] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0111] As described in the background technology, existing coal enterprises have high energy consumption. The inventors have found through research that the reasons for this problem are as follows.

[0112] In addition to the year-round demand for electricity, bathing water, and clothes drying, existing coal companies also have demands for building heating and shaft antifreeze in winter, and building cooling and shaft cooling in summer. At present, most of the heat used in coal mines is met by boilers (including coal-fired, gas-fired, or electric-fired). However, coal-fired boilers have problems such as low thermal efficiency, direct emissions of pollutants, and waste of resources. Gas-fired boilers have problems such as high nitrogen oxide emissions and high operating costs. Explosion accidents also occur from time to time during the start-up and shutdown of the furnace. In addition, in countries with scarce natural gas resources, a stable supply of natural gas is difficult to guarantee. Although electric boilers are relatively safe to operate, their application is limited by the power capacity of coal mines, and their operating costs are also high.

[0113] Coal mines are rich in waste heat resources, which are characterized by many types, large volume, low grade, stability and reliability. The types of waste heat that can be utilized include return air, mine water, equipment (gas extraction pumps, reducers, etc.) cooling water, air compressor (hereinafter referred to as "air compressor") waste heat, gas generator exhaust and cylinder liner cooling water, etc. The use of waste heat can generally solve at least 50% of the heat demand of coal mines, and for coal mines with high water inflow, it can even solve the heat demand of the entire mining area. Taking a coal mine in Jincheng City, Shanxi Province and a coal mine in Yongcheng City as examples, the former has a heat demand of 20MW, although the water inflow is only 12m 3 / h, but the total amount of equipment cooling water, return air, gas generator waste heat, and air compressor waste heat reaches 14MW; the latter heat demand is 12MW, and the mine water waste heat alone is as high as 10.2MW (the water inflow reaches 625m 3 / h), plus the waste heat from return air, air compressor lubricating oil, and equipment cooling water, the total waste heat reaches 20MW. It can be seen that the development of waste heat recovery and utilization technology is an effective way for coal mines to use energy rationally and achieve energy conservation and emission reduction.

[0114] Among them, the air compressor is the main equipment of the coal mine compressed air system, providing air power for production and air supply for the compressed air self-rescue system of the gas outburst mine. It is an important guarantee for the safe production of coal mines, and the waste heat generated by the air compressor is large. Therefore, the utilization of the waste heat of the air compressor is of great significance to reduce the energy consumption of key energy-consuming enterprises such as coal enterprises and achieve energy conservation and emission reduction.

[0115] In view of this, an embodiment of the present invention provides an air compressor waste heat comprehensive utilization system, which can be applicable to coal enterprises. Figure 1 This is a schematic diagram of the structure of an air compressor waste heat comprehensive utilization system provided by an embodiment of the present invention. Figure 1 The air compressor waste heat comprehensive utilization system includes: an air compressor 100, a heat recovery unit 200, a first heat exchanger 300, a fresh air unit 400 and a heating water pipeline 500. The air compressor 100 generates heat during operation. The heat recovery unit 200 is connected to the air compressor 100 through a pipeline, and the heat recovery unit 200 is used to recover the heat generated by the air compressor 100 and heat and soften the circulating water. The first heat exchanger 300 is connected to the heat recovery unit 200 through a pipeline, and the first heat exchanger 300 uses softened circulating water to produce hot water for bathing. The fresh air unit 400 is connected to the heat recovery unit 200 through a pipeline, and the fresh air unit 400 uses softened circulating water to heat the fresh air. The heating water pipeline 500 is connected to the heat recovery unit 200, and the heating water pipeline 500 uses softened circulating water for building heating.

[0116] Among them, the first heat exchanger 300 can be, for example, a closed self-cleaning heat exchanger as part of the bathing water subsystem; the fresh air unit 400 is part of the hanging basket drying subsystem; the heating water pipeline is part of the heating subsystem. Exemplarily, the working principle of the air compressor waste heat comprehensive utilization system is: the heat recovery unit 200 recovers the heat of the lubricating oil of the air compressor 100 to produce 45°C to 60°C softened circulating water, a part of which is passed into the first heat exchanger 300 to heat tap water and produce 42°C tap water for employees to bathe; a part is passed into the fresh air unit 400 to heat fresh air and produce 40°C fresh air, which is passed into the hanging basket area through the air duct to dry employees' clothes; a part is used as heating water for building heating.

[0117] It can be seen that the embodiment of the present invention considers using the waste heat of the air compressor to meet the heat needs of bathing water production, building heating, hanging basket clothes drying, etc., and there are rich ways to utilize the waste heat, which is conducive to the comprehensive utilization of the waste heat of the air compressor. The embodiment of the present invention does not need to consume primary energy such as natural gas and coal, has no direct pollutant emissions, and has the advantages of high degree of automation and good clothes drying effect. In addition, the embodiment of the present invention can reduce the use of boilers, which is conducive to avoiding the problems of low thermal efficiency, direct pollutant emissions, and waste of resources in coal-fired boilers; it is conducive to avoiding the problems of high nitrogen oxide emissions, high operating costs, explosion accidents during the start-up and shutdown of the furnace, and difficulty in ensuring stable supply in gas boilers; it is conducive to avoiding the application of electric boilers being limited by the power capacity of coal mines and high operating costs. Therefore, the embodiment of the present invention reduces the energy consumption of key energy-consuming enterprises such as coal enterprises, and is conducive to achieving energy conservation and emission reduction.

[0118] Continue to see Figure 1 On the basis of the above-mentioned embodiment, optionally, the air compressor waste heat comprehensive utilization system also includes: an air source heat pump 600, the air source heat pump 600 is connected to the heat recovery unit 200 through a pipeline; the air source heat pump 600 is a backup heat source for the heat recovery unit 200. Among them, the air source heat pump 600, the air compressor 100, the heat recovery unit 200, etc. constitute a heat source subsystem. The air source heat pump 600 uses electricity as a driving energy source and uses the atmosphere as a low-temperature heat source to produce 45-60°C softened circulating water, which is used as a supplementary and backup heat source. The embodiment of the present invention is configured in this way, and the renewable energy utilization technology is used to supplement and ensure the heat source, which further reduces the energy consumption of key energy-consuming enterprises such as coal enterprises and is conducive to achieving energy conservation and emission reduction.

[0119] Based on the above embodiments, there are many types of air compressors 100. The following is an explanation of a water-cooled oil-injected screw air compressor, but this is not intended to limit the present invention.

[0120] Figure 2 A schematic diagram of the structure of an air compressor and a heat recovery unit connected to each other according to an embodiment of the present invention. Figure 2 In one embodiment of the present invention, optionally, the air compressor 100 is an oil-injected screw air compressor; the air compressor 100 includes a filter 110, a motor 120, a body 130, an oil-gas separator 140, a thermostat 150, an oil filter 160, an oil cooler 170, an air cooler 180, a lubricating oil pipeline, an oil-gas mixture pipeline, and a compressed air pipeline.

[0121] The motor 120 and the body 130 are connected via a drive shaft. Specifically, the body 130 is composed of two mutually meshing rotors (a female rotor and a male rotor) with helical gears, and the male rotor is connected to the motor 120 via a drive shaft.

[0122] The filter 110 is fixedly connected to the body 130, and the filter 110 is used to filter the air and suck the air into the body 130. Optionally, a control valve 190 is provided between the filter 110 and the body 130 to control the amount of air sucked.

[0123] The engine body 130 and the oil-gas separator 140 are connected via an oil-gas mixture pipeline; the oil-gas separator 140 is used to separate oil and gas from the oil-gas mixture generated by the engine body 130. Optionally, the oil-gas separator 140 includes a safety valve 141 and a pressure maintaining valve 142.

[0124] The oil-gas separator 140 and the heat recovery unit 200 are connected via a lubricating oil pipeline; the heat recovery unit 200 is used to recover the heat in the lubricating oil and heat and soften the circulating water.

[0125] The thermostat 150 and the heat recovery unit 200 are connected via a lubricating oil pipeline; the thermostat 150 is used to detect the temperature of the lubricating oil to determine whether the lubricating oil flows directly into the oil filter 160 or flows into the oil filter 160 after passing through the oil cooler 170. It can be seen that the heat recovery unit 200 is connected in series between the oil-gas separator 140 and the cooling system of the air compressor 100 in the embodiment of the present invention.

[0126] The oil cooler 170 and the temperature controller 150 are connected via a lubricating oil pipeline; the oil cooler 170 is used to cool the lubricating oil exceeding a preset temperature.

[0127] The oil filter 160 and the oil cooler 170 are connected through a lubricating oil pipeline, and the oil filter 160 and the thermostat 150 are connected through a lubricating oil pipeline; the oil filter 160 is used to filter the lubricating oil cooled by the oil cooler 170 and filter the lubricating oil not cooled by the oil cooler 170. Exemplarily, if the temperature of the lubricating oil exceeds a preset temperature, the oil filter 160 filters the lubricating oil cooled by the oil cooler 170; if the temperature of the lubricating oil does not exceed the preset temperature, the lubricating oil does not need to be cooled, and the oil filter 160 filters the lubricating oil not cooled by the oil cooler 170.

[0128] The body 130 and the oil filter 160 are connected via a lubricating oil pipeline to achieve the recycling of the lubricating oil.

[0129] The air cooler 180 and the oil-gas separator 140 are connected via a compressed air pipeline; the air cooler 180 is used to generate compressed air.

[0130] Exemplarily, the working principle of the air compressor 100 is as follows: the air around the air compressor 100 is filtered by the filter 110 and then sucked into the body 130. The male rotor in the body 130 rotates under the drive of the motor 120, and the female rotor follows the rotational motion, completing the suction, compression, and exhaust processes by periodically changing the volume between each pair of tooth slots. At the same time, oil is continuously sprayed into the body 130 to lubricate and cool the rotor, thereby generating a high-temperature and high-pressure oil-gas mixture composed of lubricating oil and compressed air. The temperature of the oil-gas mixture is usually between 80 and 100°C. If the heat is not discharged in time, the lubricating oil will be emulsified by heat and lose its lubricating effect, causing the internal temperature of the air compressor 100 to rise sharply and shut down. In more serious cases, the lubricating oil will carbonize, causing the male and female rotors to be unable to be lubricated and wear.

[0131] After the oil-gas mixture flows out of the machine body 130, it enters the oil-gas separator 140 through the check valve for oil-gas separation. The separated lubricating oil enters the recovery unit 200. After the lubricating oil is cooled in the heat recovery unit 200, it enters the thermostat 150 to detect the oil temperature using a temperature sensing element. If the oil temperature is higher than the first preset temperature (e.g. 60°C), the lubricating oil should first enter the oil cooler 170 for further cooling, and then enter the oil filter 160 for filtration before passing to the machine body 130; if the oil temperature is lower than the first preset temperature (e.g. 60°C), the lubricating oil does not need to be further cooled, and directly enters the oil filter 160 for filtration before passing to the machine body 130.

[0132] The lubricating oil in the oil cooler 170 transfers heat to the circulating cooling water, and finally radiates to the atmosphere through the cooling tower. The cooled lubricating oil enters the oil filter 160 for filtration, and then returns to the body 130 for recycling.

[0133] When the air pressure in the oil-gas separator 140 reaches the set value, the pressure maintaining valve 142 opens, and the compressed air enters the air cooler 180 for cooling. The cooled compressed air is separated by the condensate separator, discharged through the exhaust device, and finally sent to the underground for use through the pipeline.

[0134] The embodiment of the present invention connects the heat recovery unit 200 in series between the oil-gas separator 140 and the cooling system of the air compressor 100, which is not only conducive to the waste heat utilization of the air compressor, but also has a high safety factor. The inventor has found through research that this connection method is the most cost-effective heat recovery method for the air compressor 100, and the heat recovered from the high-temperature lubricating oil can be used to heat the circulating water.

[0135] Continue to see Figure 2 On the basis of the above embodiments, optionally, the air compressor 100 further includes: a gate valve 1A0, the gate valve 1A0 is connected between the oil-gas separator 140 and the thermostat 150 to control the amount of high-temperature lubricating oil entering the heat recovery unit 200.

[0136] Continue to see Figure 2 , analyzing the waste heat generated by the air compressor 100: In addition to the mechanical friction loss, the electrical energy consumed by the motor 120 is completely converted into the mechanical energy of the drive shaft (also called shaft work), that is, formula (1):

[0137] W=W s +Q ds (1)

[0138] Where: W is the power of the motor 120, kW; W s is the shaft work required for the actual compression process, kW; Q ds is the mechanical friction loss heat of the motor 120, kW.

[0139] The mechanical friction loss of the motor 120 is characterized by the mechanical efficiency, that is, formula (2):

[0140] Q ds =W×(1-η D ) (2)

[0141] Where: η D is the mechanical efficiency of the motor 120 .

[0142] During the operation of the air compressor 100 (without considering the effect of the heat recovery unit 200), the shaft work eventually goes to four destinations: first, the heat dissipated from the outer surface of the equipment; second, the heat removed by the circulating cooling water in the air cooler 180; third, the heat removed by the air itself; and fourth, the heat removed by the circulating cooling water in the oil cooler 170, that is, formula (3):

[0143] W s =Q bs +Q ks +Q kq +Q ys (3)

[0144] Where: Q bs is the heat dissipation of the equipment outer surface, kW; Q ks is the heat taken away by the circulating cooling water in the air cooler 180, kW; Q kq is the heat brought by the air itself, kW; Q ys The heat carried away by the circulating cooling water in the oil cooler 170, kW.

[0145] The heat dissipation of the equipment's outer surface mainly includes the heat dissipation of the outer surfaces of four major components, namely, the machine body 130, the oil-gas separator 140 and its pipelines, the oil cooler 170, and the air cooler 180, that is, formula (4):

[0146] Q bs =Q jt +Qyt +Q yl +Q kl (4)

[0147] Where: Q jt is the heat dissipation of the outer surface of the body 130, kW; Q yt is the heat dissipation of the oil-gas separator 140 and its outer surface of the pipeline, kW; Q yl is the heat dissipation of the outer surface of the oil cooler 170, kW; Q kl is the heat dissipated from the outer surface of the air cooler 180, kW.

[0148] The heat dissipation of the component surface belongs to the heat transfer process, and the heat dissipation can be determined according to the heat transfer equation, that is, formula (5):

[0149] Q=k×A×ΔT (5)

[0150] Where: Q is the heat dissipation of the component's outer surface, kW; k is the component's surface heat transfer coefficient, kW / (m 2 ·K); A is the heat dissipation area of ​​the component's outer surface, m 2 ; ΔT is the average temperature difference between the hot and cold fluids on the inside and outside of the component surface, K.

[0151] The air actually sucked in by the air compressor 100 during operation contains water vapor, that is, wet air. Except for the air cooler 180, the amount of water vapor condensed in other components can be ignored. Applying the law of conservation of energy to the air cooler 180, we have formula (6):

[0152] m a (h B -h C )=Q kl +Q ks +Q ln (6)

[0153] Where: m a is the mass flow rate of dry air in wet air, kg dry air / s; h B The inlet of air cooler 180 ( Figure 2 Enthalpy of moist air (point B), kJ / kg dry air; h C For the outlet of air cooler 180 ( Figure 2 Point C shown) Enthalpy of moist air, kJ / kg dry air; Q ln The heat released by condensation of water vapor in the humid air in the air cooler 180, kW.

[0154] The enthalpy of moist air is the sum of the enthalpy of dry air and the enthalpy of water vapor, that is, formula (7):

[0155] h=1.01×T+d×(2501+1.85×T) (7)

[0156] Where: h is the enthalpy of moist air, kJ / kg dry air; 1.01 is the average specific heat of dry air at constant pressure, kJ / (kg dry air·K); T is the temperature of moist air, K; d is the moisture content of moist air, kg water vapor / kg dry air; 2501 is the latent heat of vaporization of water at 0°C, kJ / kg water vapor; 1.85 is the average specific heat of water vapor at constant pressure, kJ / (kg water vapor·K).

[0157] The humidity content of moist air is given by formula (8):

[0158]

[0159] in: is the relative humidity of moist air, %; p s is the saturated partial pressure of water vapor, Pa; p is the absolute pressure of humid air, Pa.

[0160] The temperature of the wet air in the air cooler 180 is generally between 40°C and 80°C, and the heat released by the condensation of water vapor is given by formula (9):

[0161] Q ln =m a ×(d B -d C )×γ (9)

[0162] Where: d B is the moisture content of the wet air at the inlet of the air cooler 180, kg water vapor / kg dry air; d C is the moisture content of the wet air at the outlet of the air cooler 180, kg water vapor / kg dry air; γ is the latent heat of vaporization of saturated water, which is 2407 at 40℃ and 2309 at 80℃, kJ / kg water vapor.

[0163] From formula (8), it can be concluded that the heat removed by the circulating cooling water in the air cooler 180 is given by formula (10):

[0164] Q ks =m a (h B -h C )-Q bs,kl -Q ln (10)

[0165] The heat carried away by the air itself is Figure 2 The sensible heat increase at point C relative to point D is shown in formula (11):

[0166] Q kq =m a ×[1.01×(T C -T A )+1.85×dC ×(T C -T A )] (11)

[0167] Where: T C is the wet air temperature at point C, K; T A is the wet air temperature at point D, K.

[0168] From formula (1) and formula (5), it can be concluded that the heat removed by the circulating cooling water in the oil cooler 170 is formula (12):

[0169] Q ys =WQ ds -Q bs -Q ks -Q kq (12)

[0170] The heat that can be recycled by the air compressor 100 includes three parts: first, the heat carried away by the circulating cooling water in the air cooler 180; second, the heat carried away by the circulating cooling water in the oil cooler 170; third, the heat released by the condensation of water vapor in the humid air in the air cooler 180, that is, formula (13):

[0171] Q hs =Q ks +Q ys +Q ln (13)

[0172] Where: Q hs is the total heat that can be recovered by the air compressor 100, kW.

[0173] After calculation, it is found that the air compressor has abundant waste heat that can be used to meet the heat needs of bathing water preparation, building heating, hanging basket clothes drying, etc.

[0174] Based on the above embodiments, there are many ways to set up the bathing water subsystem, the hanging basket drying subsystem and the heating subsystem. Several of them are described below, but they are not intended to limit the present invention.

[0175] Figure 3 This is a schematic diagram of another air compressor waste heat comprehensive utilization system provided by an embodiment of the present invention. Figure 3In one embodiment of the present invention, optionally, the bathing water subsystem also includes a tap water tank 1 and a hot water tank 4, and the tap water tank 1 and the hot water tank 4 are connected by a pipeline, and the first heat exchanger 300 is arranged in the hot water tank 4 to realize the heat exchange between normal temperature tap water and softened circulating water. Among them, the first heat exchanger 300 can be a closed self-cleaning heat exchanger, for example. The heat exchange coil of the closed self-cleaning heat exchanger is spiral in shape and made of stainless steel. The medium inside the tube is softened water, and the medium outside the tube is tap water. When the system is running, the coil will vibrate due to the change in the temperature of the medium inside and outside the tube. Due to the different expansion coefficients of scale and stainless steel, the scale formed on the outer surface of the coil will fall off by itself, thereby effectively avoiding the accumulation of scale.

[0176] Continue to see Figure 3 In one embodiment of the present invention, optionally, the bathing water subsystem also includes: a thermocouple 5 and a bathing circulating water pump 8; the bathing circulating water pump 8 is arranged in the pipeline between the hot water tank 4 and the heat recovery unit 200, and the bathing circulating water pump 8 is used to control the heat exchange amount of the hot water tank 4; the thermocouple 5 is arranged in the hot water tank 4, and the thermocouple 5 is used to control the working state of the bathing circulating water pump 8 according to the temperature of the hot water.

[0177] Continue to see Figure 3 In one embodiment of the present invention, optionally, the bathing water subsystem further includes: a cable float 2, a solenoid valve 3, a temperature control proportional regulating valve 9 and a bathing water supply pump 10. Among them, a cable float 2 is located at the top of the tap water tank 1, a solenoid valve 3 is located on the water supply pipe of the tap water tank 1, the water supply pipe of the tap water tank 1 is connected to the tap water pipe 6, and the electric circuit of the cable float 2 is connected in series with the solenoid valve 3. The cable float 2 controls the water level of the tap water tank 1 through the solenoid valve 3, realizes automatic water replenishment of the tap water tank 1, and controls the water level of the tap water tank 1 within a certain range; a cable float 2 is located at the top of the hot water tank 4, a solenoid valve 3 is located on the water supply pipe of the hot water tank 4, the water supply pipe of the hot water tank 4 is connected to the tap water pipe 6, and the electric circuit of the cable float 2 is connected in series with the solenoid valve 3. The cable float 2 controls the water level of the hot water tank 4 through the solenoid valve 3, realizes automatic water replenishment of the hot water tank 4, and controls the water level of the hot water tank 4 within a certain range.

[0178] The temperature control proportional regulating valve 9 is a three-way valve, one interface is connected to the tap water tank 1, one interface is connected to the hot water tank 4, and one interface is connected to the bathing water supply pipeline 11. The bathing water supply pump 10 is connected to the bathing water supply pipeline 11 to provide bathing water. The temperature control proportional regulating valve 9 is arranged at the front end of the bathing water supply pipeline 11 to control the mixing ratio of the hot water in the hot water tank 4 and the normal temperature water in the tap water tank 1, and maintain the bathing water supply temperature at a constant value.

[0179] Continue to see Figure 3In one embodiment of the present invention, optionally, a thermocouple 5 is arranged on the top of the hot water tank 4, and its electrical circuit is connected in series with the bathing circulating water pump 8. The automatic start and stop of the circulating water pump is controlled by the water temperature in the hot water tank 4, and the water temperature in the hot water tank 4 is controlled in a second preset temperature range (for example, 44-46°C).

[0180] Among them, the first heat exchanger 300, the hot water tank 4, the tap water tank 1, the thermocouple 5, the cable float 2, the solenoid valve 3, the temperature control proportional regulating valve 9, etc. constitute the bathing water subsystem. In the prior art, the bathing water system is generally composed of a two-stage plate heat exchanger. The first-stage plate heat exchanger is used to return the heat in the high-temperature lubricating oil to produce circulating water at about 60°C. The circulating water is transported to the second-stage plate heat exchanger through a water pump, which is used to heat the tap water to produce bathing water at about 42°C. The bathing water is then transported to the hot water tank 4 through a water pump for employees to bathe. It can be seen from this that the existing bathing water system needs to install two sets of water pumps, resulting in a complex structure and high power consumption. In addition, there is a certain degree of water flow short circuit and eddy current at the inlet and outlet of the traditional plate heat exchanger, which leads to uneven heating and affects the heat exchange efficiency. In addition, the water quality of coal mines is poor and the hardness is high. The second-stage plate heat exchanger is prone to scaling, which seriously affects the heat exchange efficiency and hot water preparation time. The bathing water subsystem provided in the embodiment of the present invention includes a first heat exchanger 300, a hot water tank 4, a tap water tank 1, a thermocouple 5, a cable float 2, a solenoid valve 3, a temperature control proportional regulating valve 9, etc., and does not need to adopt a two-stage plate heat exchanger. It has a simple structure, uniform heating, and is not easy to scale. It uses softened circulating water as a heat exchange energy source, has low power consumption, high heat exchange efficiency, and short hot water preparation time, which is conducive to reducing energy consumption and achieving energy conservation and emission reduction.

[0181] Continue to see Figure 3 In one embodiment of the present invention, optionally, the hanging basket drying subsystem also includes: a drying circulation water pump 17, which is arranged in the pipeline between the fresh air unit 400 and the heat recovery unit 200, and the drying circulation water pump 17 is used to control the heat exchange amount of the fresh air unit 400.

[0182] Continue to see Figure 3 In one embodiment of the present invention, optionally, the fresh air unit 400 includes: a surface cooler 421, a blower 422, an exhaust fan 419 and a return air heat recovery device 420. The surface cooler 421 is connected to the heat recovery unit 200 through a pipeline, and the surface cooler 421 uses the heat recovered by the heat recovery unit 200 to heat the fresh air. The blower 422 is located at the air supply port of the fresh air unit 400, and the blower 422 is used to send out the fresh air. The exhaust fan 419 is located at the return air port of the fresh air unit 400, and the exhaust fan 419 is used to send out the return air. The return air heat recovery device 420 is located between the exhaust fan 419 and the return air duct, and the return air heat recovery device 420 uses the heat of the return air to heat the fresh air.

[0183] Continue to see Figure 3 Optionally, the fresh air unit 400 further includes a primary filter 418, which is used to filter the air entering the fresh air unit 400. The primary filter 418, the exhaust fan 419, the return air heat recovery device 420, the surface cooler 421, the air supply fan 422, etc. constitute the fresh air unit 400, and the fresh air unit 400, the fresh air duct, the return air duct, etc. constitute the hanging basket drying subsystem.

[0184] Exemplarily, the working principle of the fresh air unit 400 is as follows: the fresh air is heated by the return air and the heat source circulating water in the fresh air unit 400 in turn; then, the fresh air is evenly introduced into the hanging basket area through the fresh air duct, filling the entire space, achieving 360° drying of wet clothes without dead ends; finally, the return air is collected by the return air duct, and discharged into the atmosphere after exchanging heat with the fresh air in the fresh air unit 400.

[0185] Continue to see Figure 3 Optionally, the heating circulation water pump 23 and the water supply and return pipes constitute a heating subsystem.

[0186] Continue to see Figure 3 Optionally, a circulating water return pipe 12 is connected between the air source heat pump 600 and the heat recovery unit 200, and a circulating water supply pipe 13 is connected therebetween to enable heat exchange circulation between the air source heat pump 600 and the heat recovery unit 200.

[0187] Continue to see Figure 3 Optionally, the air compressor waste heat comprehensive utilization system also includes: a butterfly valve 24, a rubber flexible joint 25 and a filter 26, and the butterfly valve 24, the rubber flexible joint 25 and the filter 26 are connected to each pipeline (for example, the tap water pipeline 6, the circulating water return pipeline 12, the circulating water supply pipeline 13, the water supply pipeline, etc.).

[0188] It can be seen that the embodiment of the present invention considers using the waste heat of the air compressor to meet the heat needs of bathing water preparation, building heating, hanging basket clothes drying, etc., and the waste heat utilization methods are rich, which is conducive to the comprehensive utilization of the waste heat of the air compressor. The embodiment of the present invention does not need to consume primary energy such as natural gas and coal, only consumes a small amount of electricity, has no direct pollutant emissions, and has the advantages of high degree of automation, constant and controllable bathing water temperature, efficient heat exchange and anti-scaling, and good clothes drying effect. In addition, the embodiment of the present invention can reduce the use of boilers, which is conducive to avoiding the problems of low thermal efficiency, direct pollutant emissions, and waste of resources in coal-fired boilers; it is conducive to avoiding the problems of high nitrogen oxide emissions, high operating costs, explosion accidents during the start-up and shutdown of the furnace, and difficulty in ensuring stable supply in gas boilers; it is conducive to avoiding the application of electric boilers being limited by the power capacity of coal mines and high operating costs. Therefore, the embodiment of the present invention reduces the energy consumption of key energy-consuming enterprises such as coal enterprises, which is conducive to achieving energy conservation and emission reduction.

[0189] The embodiment of the present invention also provides an operation method of an air compressor waste heat comprehensive utilization system. The operation method can be applied to the air compressor waste heat comprehensive utilization system provided by any embodiment of the present invention, and has corresponding functions and beneficial effects. Specifically:

[0190] Figure 4 A schematic diagram of a flow chart of an operation method of an air compressor waste heat comprehensive utilization system provided by an embodiment of the present invention. Figure 4 The operation method of the air compressor waste heat comprehensive utilization system includes the following steps.

[0191] Step 1. Determine the boundary conditions.

[0192] Specifically include: Step 11, determine the external application load conditions, including: building heating heat load, bathing water heat load and hanging basket clothes drying heat load.

[0193] The building heating heat load is calculated based on the type and building area of ​​the heating building. The specific calculation formula is formula (14):

[0194] Q cn =S×q×10 -3 (14)

[0195] Where: Q cn is the building heating heat load, kW, and this value is 0 during the period without building heating heat load; S is the building area of ​​the heating building, m 2 ; q is the building heating heat index, W / m 2 .

[0196] The heat load of bathing water can be calculated based on the amount and temperature of bathing water, and can also be combined with local climate characteristics and temperature. The specific calculation formula is formula (15):

[0197] Q xy =c xs ×m xs ×(T sh -T sq ) (15)

[0198] Where: Q xy is the bathing water heat load, kW, and this value is 0 during the period without bathing water heat load; c xs is the constant pressure specific heat capacity of tap water, which is 4.186 kJ / (kg·℃); m xs is the amount of bathing water, kg / s; T sh is the bathing water supply temperature, ℃; T sq is the temperature of tap water before heating, ℃.

[0199] The heat load of clothes drying in hanging baskets can be calculated based on the number of hanging baskets and can also be combined with local climate characteristics and temperature. The specific calculation formula is formula (16):

[0200] Q hg =c xf ×ρ xf ×V xf ×(T xh -T xq ) (16)

[0201] Where: Q hg is the heat load of clothes drying, kW, and this value is 0 during the period without heat load of clothes drying; c xf is the constant pressure specific heat capacity of fresh air, which is taken as 1kJ / (kg·℃); ρ xf is the fresh air density, which is calculated based on the density corresponding to the average temperature before and after the fresh air is heated, kg / m 3 ; V xf is the fresh air volume flow rate, m 3 / s, according to operating experience, each hanging basket needs 3.5m 3 / hFresh air volume; T xh is the temperature of the fresh air after heating, ℃; T xq It is the temperature of fresh air before heating, ℃.

[0202] Step 12. Determine the waste heat resources of the air compressor, including: air compressor parameters, number of air compressors and operating rules of the air compressor.

[0203] The method for determining the waste heat resources of the air compressor has been described in detail in the above embodiments and will not be repeated here.

[0204] Step 2. Determine the configuration and run the model.

[0205] Specifically include: Step 21, determine the cost objective function, including: annual electricity fee, annual maintenance fee, annual equivalent fee of initial investment and annual labor cost.

[0206] Among them, from the perspective of economic optimization, the cost objective function is to minimize the total annual cost, as shown in formula (17):

[0207]

[0208] Among them: Z is the total annual cost of the system, RMB / year, a continuous variable; i is the type of main equipment, there are I (for example, I=4) main equipment in the system, including air source heat pump, represented by the letter KR; fresh air unit, represented by the letter XF; heat recovery unit, represented by the letter RH; closed self-cleaning heat exchanger, represented by the letter BH; other equipment are defined as auxiliary equipment; k is the time period, and the whole year is divided into K time periods in total; is the electricity price, RMB / kWh; D is the duration of each period throughout the year, h / year; x KR is the input power of the air source heat pump, kW, continuous variable; x FZ is the input power of power-consuming auxiliary equipment including water pumps and fans, kW, which is related to the total heat load (i.e. the sum of building heating heat load, bathing water heat load, and hanging basket clothes drying heat load). Optionally, 0.05kW / kW heat load is taken according to engineering experience; α is the ratio of annual maintenance fee to annual equivalent cost of initial investment, and optionally, 30% is taken according to operating experience; β is the ratio of annual labor cost to annual equivalent cost of initial investment, and optionally, 60% is taken according to operating experience; γ is the ratio of engineering cost to equipment cost, and optionally, 60% is taken according to engineering experience; τ is the ratio of auxiliary equipment (including installation) cost to main equipment (including installation) cost, and optionally, 40% is taken according to engineering experience; R is the capital investment recovery coefficient, R=r(1+r) τ / ((1+r) τ -1), r is the annual loan interest rate, τ is the service life of the equipment, the values ​​of r and τ are 5% and 15 years respectively; c is the unit capacity cost of the main equipment (including installation), RMB / kW; M is the total capacity of the main equipment, kW, a continuous variable.

[0209] Step 22. Determine the equipment operation constraints, including: equipment capacity constraints, equipment operation characteristic constraints and system energy flow balance constraints.

[0210] Among them, in determining the equipment capacity constraint, since the investment and operating costs of air source heat pumps are higher than those of heat recovery units, priority should be given to configuring heat recovery units. The number and capacity of heat recovery units depend on the number, performance and operating rules of air compressors. Each air compressor is equipped with a heat recovery unit, and the capacity depends on the heat dissipated by the high-temperature lubricating oil in the oil cooler. In addition, the output attenuation caused by surface scaling and bubbling after long-term operation of the unit is also considered, as shown in formula (18):

[0211]

[0212] in: is the theoretical capacity of a single heat recovery unit, kW / unit; η ys is the heat exchange efficiency of the air compressor oil cooler, %; η rh is the heat exchange efficiency of the heat recovery unit, %; m rh is the capacity of a single heat recovery unit, kW / unit; ξ rh is the output attenuation coefficient of the heat recovery unit in long-term operation, generally 20%; n rh The number of heat recovery units installed, units, integer variable; n ky The number of air compressors installed, M rhis the total capacity of the heat recovery unit, kW.

[0213] If the total capacity of the heat recovery unit is higher than the total heat load of all periods, there is no need to install an air source heat pump. Otherwise, an air source heat pump needs to be installed. Its capacity depends on the highest total heat load of each period. Since it is a standard equipment, the capacity and number of units need to consider the existing capacity in the market, and try to ensure that the equipment operates at a high load rate. In addition, the air source heat pump contains power components, and equipment maintenance and overhaul must also be considered. One to two units should be kept in reserve. As shown in formula (19):

[0214]

[0215] in: is the theoretical total capacity of the air source heat pump, kW; L ky is the average annual operating load rate of the air compressor, %; is the number of air compressors in operation, m kr is the capacity of a single air source heat pump on the market, kW / unit; n kr The number of air source heat pumps installed, unit, integer variable; M kr is the total capacity of the air source heat pump, kW.

[0216] The fresh air unit is a non-standard device and can be designed and manufactured by yourself. Its capacity is determined according to the heat load of the hanging basket clothes drying. The number of units does not need to consider the backup. Optionally, there is 1 fresh air unit. In addition, the output attenuation caused by surface scaling and bubbling after long-term operation of the unit is also considered, as shown in formula (20):

[0217]

[0218] in: is the theoretical total capacity of the fresh air unit, kW; M xf is the total capacity of the fresh air unit, kW; ξ xf is the long-term output attenuation coefficient of the fresh air unit, optionally, ξ xf Take 20%; m xf is the capacity of a single fresh air unit, kW / unit; n xf The number of fresh air units installed, units, integer variable.

[0219] The closed self-cleaning heat exchanger is a non-standard device and can also be designed and manufactured by itself. Its capacity is determined according to the heat load of the bathing water. The number of units does not need to be considered as a backup, but the maintenance and repair of the water supply valve must be considered. Optionally, there are 2 closed self-cleaning heat exchangers. In addition, the output attenuation caused by surface scaling and bubbling after long-term operation of the heat exchanger is also considered, as shown in formula (21):

[0220]

[0221] in: is the theoretical total capacity of the closed self-cleaning heat exchanger, kW; M bh is the total capacity of the closed self-cleaning heat exchanger, kW; ξ bh is the long-term operation output attenuation coefficient of the closed self-cleaning heat exchanger, optionally, ξ bh Take 20%; m bh is the capacity of a single closed self-cleaning heat exchanger, kW / unit; n bh The number of closed self-cleaning heat exchangers installed, units, integer variable.

[0222] In the constraints of equipment operation characteristics, the output (output energy power) of thermal equipment is approximately linearly related to the input energy power. In order to fully ensure the equipment operation efficiency, all operating units of the same type of equipment should share the output (that is, the load rate of all operating units of the same type of equipment at any time is the same), as shown in formula (22):

[0223]

[0224] Among them: y is the output energy power of the equipment, kW; p and q are the performance parameters of the equipment; x is the input energy power of the main equipment, kW, a continuous variable; δ is an integer variable, indicating the number of equipment in operation; x is the upper and lower limits of the energy power input of a single device, kW; n is the number of devices installed, units.

[0225] The system energy flow balance includes the heat balance of air compressor lubricating oil, the heat balance of softening circulating water, the heat balance of hanging basket clothes drying, and the heat balance of bathing water.

[0226] The heat balance of air compressor lubricating oil is shown in formula (23):

[0227]

[0228] Where: x rh is the input heat power of the heat recovery unit, kW, continuous variable.

[0229] The heat balance of softening circulating water is shown in formula (24):

[0230]

[0231] Where: y kr is the output heat power of the air source heat pump, kW; y rh is the output heat power of the heat recovery unit, kW; x xf is the input heat power of the fresh air unit, kW, continuous variable; x bhis the input heat power of the closed self-cleaning heat exchanger, kW, continuous variable.

[0232] The heat balance of hanging basket clothes drying is shown in formula 25:

[0233]

[0234] Among them: Among them: y xf is the output heat power of the fresh air unit, kW.

[0235] The heat balance of bathing water is shown in formula (26):

[0236]

[0237] Where: y bh is the output heat power of the closed self-cleaning heat exchanger, kW.

[0238] The constraint conditions (18) to (26) and the objective function (17) constitute the optimization configuration and operation model, which is a mixed integer nonlinear programming model.

[0239] Step 3, solve the equipment operation mode; specifically, solve the operation mode of each device in the air compressor waste heat comprehensive utilization system according to the determined boundary conditions and configuration and operation model.

[0240] Among them, general optimization solvers such as LINGO, AIMMS, and MATLAB can be used to solve the model and obtain the final solution set. The operation mode of the equipment includes: the type of operating equipment, the number of operating equipment, the capacity of the operating equipment, and the operating law of the equipment.

[0241] In order to give full play to the energy advantages of the air compressor waste heat comprehensive utilization system, the embodiment of the present invention has carried out reasonable optimization design, configuration and operation of the system operation, and optimized the capacity, number and operation rules of the main equipment. Specifically, on the first aspect, the embodiment of the present invention has made a clear analysis of the heat recovery principle of the air compressor, and fully studied the energy conversion mechanism during the working process of the air compressor, which is conducive to the reasonable selection of the heat recovery unit, thereby improving the system operation efficiency and economy. On the second aspect, the embodiment of the present invention takes into account the system operation optimization problem, and the advantages of the system economy, energy saving, and emission reduction are fully utilized.

[0242] On the basis of the above embodiments, the embodiment of the present invention further provides a detailed embodiment. Taking a coal mine with a production capacity of 3 million tons / year as an example, the coal mine has 4 water-cooled oil-injected screw air compressors, two for use and two for backup, with an average annual operating load rate of 80%. The air compressor parameters and heat calculation results are shown in Table 1 and Table 2 respectively.

[0243] Table 1

[0244]

[0245] Table 2

[0246]

[0247] The heat ratio is the ratio of the heat to the power of the motor 120 .

[0248] It can be seen from the table that the total recyclable heat is 337.2 kW, accounting for 89.9% of the power of the motor 120; among the three types of recyclable heat, the heat dissipated by cooling the high-temperature lubricating oil in the oil cooler 170 accounts for the highest proportion, accounting for 82.3% of the total recyclable heat.

[0249] From the above analysis, it can be seen that the air compressor has abundant waste heat that can be utilized to meet the heat needs of bathing water preparation, building heating, hanging basket clothes drying, etc.

[0250] The air compressor waste heat comprehensive utilization system provided by the embodiment of the present invention is used to replace the 4t / h coal-fired boiler to complete: ① bath water production, with a daily consumption of 350 tons (4.05kg / s), which is supplied 365 days a year; ② bathroom heating, with a construction area of ​​2824m 2 , the heating time is from October 1st to March 31st of the following year, 24 hours a day; ③ Hanging basket clothing drying, a total of 3,500 hanging baskets, the drying time is 365 days a year, 24 hours a day.

[0251] The bathroom heating heat index is 70W / m 2 , then the heating heat load is 198kW. The tap water temperature before heating is 10℃, and the bathing water supply temperature is 42℃, then the bathing water heat load is 543kW. The fresh air volume flow rate is 12250m 3 / h. The fresh air parameters and heat load of hanging basket clothes drying in different seasons are shown in Table 3.

[0252] Table 3

[0253]

[0254] According to the energy consumption characteristics of coal mines, the whole year is divided into six periods: Spring I (April and May), Spring II (March), Summer (June, July and August), Autumn I (September), Autumn II (October and November), and Winter (December, January and February). The duration and heat load of each period throughout the year are shown in Table 4.

[0255] Table 4

[0256]

[0257] The heat exchange efficiency of the oil cooler is 92%, and the calculation parameters of the main equipment are shown in Table 5. In addition, the electricity price is 0.56 yuan / kWh.

[0258] Table 5

[0259]

[0260] The system optimization configuration and operation calculation are carried out, and the number and capacity of the main equipment are shown in Table 6. Among them: 6 air source heat pumps are installed with a total capacity of 540kW, and the total capacities of the fresh air unit, heat recovery unit, and closed self-cleaning heat exchanger are 125kW, 1148kW, and 544kW respectively.

[0261] Table 6

[0262]

[0263]

[0264] Figure 5 This is a line chart of the output of an air source heat pump during the whole year of operation provided by the embodiment of the present invention. Figure 5 The air source heat pump is turned on and running all year round, with an output between 130kW and 411kW, the lowest in Autumn I and the highest in Spring II, and the average output throughout the year is 270kW.

[0265] Figure 6 A line chart showing the number of air source heat pumps running throughout the year provided by an embodiment of the present invention. Figure 6 The air source heat pump is turned on and operated throughout the year, with 2 to 5 units in operation, 2 units in summer and autumn I, 3 units in spring I, 4 units in autumn II, and 5 units in spring II and winter.

[0266] Figure 7 A line chart of the load rate of an air source heat pump running throughout the year provided by an embodiment of the present invention. Figure 7 The air source heat pump is turned on and operated throughout the year, with an operating load rate between 72% and 92%, the lowest in autumn I and the highest in spring II. The average operating load rate throughout the year is 84%.

[0267] Figure 8 A line chart of the annual power output of a fresh air unit provided by an embodiment of the present invention. Figure 8 The fresh air unit is turned on and running all year round. The output depends on the heat load of the hanging basket clothes drying. The output is between 45kW and 128kW. It is lowest in autumn I and autumn II and highest in spring I and spring II. The average output throughout the year is 87kW.

[0268] Fig. 9 A line chart of the annual startup load rate of a fresh air unit provided by an embodiment of the present invention. Fig. 9The fresh air unit is turned on and running all year round. The operating load rate depends on the heat load of the hanging basket clothes drying. The operating load rate is between 28% and 80%, and the annual average operating load rate is 54%.

[0269] The operation rules of the heat recovery unit depend on the operation rules of the air compressor. Two heat recovery units are in operation throughout the year, with an output of 459kW and an operating load rate of 64%.

[0270] The operation law of the closed self-cleaning heat exchanger depends on the heat load of the bathing water. Two closed self-cleaning heat exchangers are operated throughout the year, with an output of 543kW and an operating load rate of 80%.

[0271] By optimizing the configuration and running calculation of the embodiment of the present invention, the initial investment and annual total cost of the system can be obtained at the same time. After calculation, the initial investment of the system is 3.92 million yuan, including: 1.75 million yuan for main equipment, 700,000 yuan for auxiliary equipment, and 1.47 million yuan for engineering. The annual total cost of the system is 1.356 million yuan, and the specific details are shown in Table 7, among which: the electricity fee accounts for the highest proportion, reaching 47.3%; followed by the annual equivalent cost of the initial investment, accounting for 27.7%.

[0272] Table 7

[0273]

[0274] Compared with the embodiment of the present invention, the energy supply scheme of the prior art is a coal-fired boiler, and the hanging basket clothes drying is not considered. According to actual statistical data (in years), 4,163 tons of coal are consumed for bathing water production and 518 tons of coal are consumed for bathroom heating. According to the heat load conversion, if the hanging basket clothes drying is considered, another 443 tons of coal will be consumed. The coal price is calculated at 700 yuan / ton, and the total annual cost of the coal-fired boiler solution is 4.675 million yuan. See Table 8 for specific details.

[0275] Table 8

[0276]

[0277] Among them, the various costs of hanging basket clothes drying are calculated based on the heat load.

[0278] In summary, compared with the coal-fired boiler solution in the prior art, the air compressor waste heat comprehensive utilization system has significant advantages in terms of economy, energy saving and emission reduction, as follows:

[0279] (1) The initial investment increased by RMB 3.26 million, but the operating expenses (the annual equivalent of the initial investment minus the annual total expenses) saved RMB 3.631 million each year, which means that the increased initial investment can be recovered within one year.

[0280] (2) Make full use of the waste heat in the air compressor lubricating oil, consume only a small amount of electricity, and do not consume primary energy such as natural gas and coal, saving 4,758 tons of standard coal per year.

[0281] (3) There are no direct pollutant emissions. Based on the calculation that one ton of standard coal produces 2.62 tons of carbon dioxide, 8.5 kilograms of sulfur dioxide, and 7.4 kilograms of nitrogen oxides, the annual carbon dioxide emissions are reduced by 12,466 tons, sulfur dioxide emissions by 40 tons, and nitrogen oxide emissions by 35 tons.

[0282] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An operating method of an air compressor waste heat comprehensive utilization system, characterized in that: The air compressor waste heat comprehensive utilization system comprises: An air compressor that generates heat during operation; A heat recovery unit is connected to the air compressor through a pipeline, and is used to recover the heat generated by the air compressor to heat and soften circulating water; A first heat exchanger is connected to the heat recovery unit through a pipeline, and the first heat exchanger uses the softened circulating water to produce hot water for bathing; A fresh air unit is connected to the heat recovery unit through a pipeline, and the fresh air unit uses the softened circulating water to heat the fresh air; A heating water pipeline is connected to the heat recovery unit, and the heating water pipeline utilizes the softened circulating water for building heating; The operating method of the air compressor waste heat comprehensive utilization system includes: determining boundary conditions; the boundary conditions include: waste heat resources of the air compressor and external application load conditions; Determine a configuration and operation model; the configuration and operation model includes: a cost objective function and equipment operation constraints; Solving the operation mode of the equipment, including solving the operation mode of each equipment in the air compressor waste heat comprehensive utilization system according to the determined boundary conditions and the configuration and operation model; The cost objective function includes: annual electricity cost, annual maintenance cost, annual equivalent cost of initial investment and annual labor cost; The equipment operation constraints include: equipment capacity constraints, equipment operation characteristic constraints and system energy flow balance constraints; The cost objective function is calculated by the following formula: Among them, Z is the total annual cost of the system; i is the main equipment type; k is the time period, and the whole year is divided into K time periods in total; is the electricity price; D is the duration of each period throughout the year; x KR is the input electrical power of the air source heat pump; x FZ is the input power of power-consuming auxiliary equipment including water pumps and fans; α is the ratio of annual maintenance fee to the annual equivalent fee of initial investment; β is the ratio of annual labor cost to the annual equivalent fee of initial investment; γ is the ratio of engineering cost to equipment cost; τ is the ratio of auxiliary equipment cost to main equipment cost; R is the capital investment recovery coefficient; c is the unit capacity cost of main equipment; M is the total capacity of main equipment.

2. The operating method of the air compressor waste heat comprehensive utilization system according to claim 1 is characterized in that: The air compressor waste heat comprehensive utilization system also includes: an air source heat pump, which is connected to the heat recovery unit through a pipeline; the air source heat pump is a backup heat source for the heat recovery unit.

3. The operating method of the air compressor waste heat comprehensive utilization system according to claim 1, characterized in that: The air compressor in the air compressor waste heat comprehensive utilization system is an oil-injected screw air compressor; the air compressor includes a filter, a motor, a body, an oil-gas separator, a thermostat, an oil filter, an oil cooler, an air cooler, a lubricating oil pipeline, an oil-gas mixture pipeline, and a compressed air pipeline; Wherein, the motor and the machine body are connected via a drive shaft; The filter is fixedly connected to the body, and the filter is used to filter air and draw the air into the body; The engine body and the oil-gas separator are connected via the oil-gas mixture pipeline; the oil-gas separator is used to separate oil and gas from the oil-gas mixture generated by the engine body; The oil-gas separator and the heat recovery unit are connected via the lubricating oil pipeline; the heat recovery unit is used to recover the heat in the lubricating oil and heat the softened circulating water; The thermostat and the heat recovery unit are connected via the lubricating oil pipeline; the thermostat is used to detect the temperature of the lubricating oil; The oil cooler and the temperature controller are connected via the lubricating oil pipeline; the oil cooler is used to cool the lubricating oil exceeding a preset temperature; The oil filter and the oil cooler are connected via the lubricating oil pipeline, and the oil filter and the thermostat are connected via the lubricating oil pipeline; the oil filter is used to filter the lubricating oil cooled by the oil cooler and the lubricating oil not cooled by the oil cooler; The engine body and the oil filter are connected via the lubricating oil pipeline; The air cooler and the oil-gas separator are connected via the compressed air pipeline; the air cooler is used to generate compressed air.

4. The operating method of the air compressor waste heat comprehensive utilization system according to claim 3 is characterized in that: The air compressor in the air compressor waste heat comprehensive utilization system further includes: a gate valve, which is connected between the oil-gas separator and the temperature controller.

5. The operating method of the air compressor waste heat comprehensive utilization system according to claim 1, characterized in that: The air compressor waste heat comprehensive utilization system also includes a tap water tank and a hot water tank. The tap water tank and the hot water tank are connected by a pipeline, and the first heat exchanger is arranged in the hot water tank.

6. The operating method of the air compressor waste heat comprehensive utilization system according to claim 5, characterized in that: The air compressor waste heat comprehensive utilization system also includes: a thermocouple and a bathing circulating water pump; the bathing circulating water pump is arranged in the pipeline between the hot water tank and the heat recovery unit, and the bathing circulating water pump is used to control the heat exchange amount of the hot water tank; the thermocouple is arranged in the hot water tank, and the thermocouple is used to control the working state of the bathing circulating water pump according to the temperature of the hot water.

7. The operating method of the air compressor waste heat comprehensive utilization system according to claim 1, characterized in that: The air compressor waste heat comprehensive utilization system also includes: a drying circulation water pump, which is arranged in the pipeline between the fresh air unit and the heat recovery unit, and the drying circulation water pump is used to control the heat exchange amount of the fresh air unit.

8. The operating method of the air compressor waste heat comprehensive utilization system according to claim 1, characterized in that: The fresh air unit in the air compressor waste heat comprehensive utilization system includes: A surface cooler is connected to the heat recovery unit through a pipeline, and the surface cooler uses the heat recovered by the heat recovery unit to heat the fresh air; A blower, located at the air outlet of the fresh air unit, and used to send out fresh air; An exhaust fan is located at the return air outlet of the fresh air unit, and is used to send out the return air; The return air heat recovery device is located between the exhaust fan and the return air duct, and the return air heat recovery device uses the heat of the return air to heat the fresh air.

9. The operating method of the air compressor waste heat comprehensive utilization system according to claim 1, characterized in that: The waste heat resources of the air compressor include: parameters of the air compressor, the number of the air compressors and the operating rules of the air compressors; The external applied load conditions include: building heating heat load, bathing water heat load and hanging basket clothes drying heat load.

10. The operating method of the air compressor waste heat comprehensive utilization system according to claim 9, characterized in that: The total heat that can be recovered by the air compressor is calculated by the following formula: W=W s +Q ds Where, W is the power of the motor; W s is the shaft work required for the actual compression process; Q ds The heat loss is caused by the mechanical friction of the motor; Q ds =W×(1-η D ) Among them, η D is the mechanical efficiency of the motor; W s =Q bs +Q ks +Q kq +Q ys Among them, Q bs Q is the heat dissipation of the equipment’s outer surface; ks The heat carried away by the circulating cooling water in the air cooler; Q kq The heat brought by the air itself; Q ys It is the heat taken away by the circulating cooling water in the oil cooler; Q bs =Q jt +Q yt +Q yl +Q kl Among them, Q jt Q is the heat dissipation of the outer surface of the body; yt Q is the heat dissipation of the oil-gas separator and its outer surface of the pipeline; yl is the heat dissipation of the outer surface of the oil cooler; Q kl The heat dissipation of the outer surface of the air cooler; Q=k×A×ΔT Where Q is the heat dissipation of the component's outer surface; k is the component's surface heat transfer coefficient / (m 2 ·K); A is the heat dissipation area of ​​the component's outer surface; ΔT is the average temperature difference between the hot and cold fluids on the inside and outside of the component's surface; m a (h B -h C )=Q kl +Q ks +Q ln Among them, m a is the mass flow rate of dry air in wet air; h B is the enthalpy of the wet air at the air cooler inlet; h C is the enthalpy of wet air at the air cooler outlet; Q ln The heat released by the condensation of water vapor in the humid air in the air cooler; h=1.01×T+d×(2501+1.85×T) Where, h is the enthalpy of moist air; T is the temperature of moist air; d is the moisture content of moist air; in, is the relative humidity of moist air; p s is the saturated partial pressure of water vapor; p is the absolute pressure of moist air; Q ln =m a ×(d B -d C )×γ Among them, d B is the humidity content of the wet air at the air cooler inlet; d C is the humidity content of the wet air at the outlet of the air cooler; γ is the latent heat of vaporization of saturated water; Q ks =m a (h B -h C )-Q bs,kl -Q ln Q kq =m a ×[1.01×(T C -T A )+1.85×d C ×(T C -T A )] Among them, T C is the wet air temperature at the air cooler outlet; T A is the filter inlet wet air temperature; Q ys =W-Q ds -Q bs -Q ks -Q kq Q hs =Q ks +Q ys +Q ln Among them, Q hs It is the total heat that can be recovered by the air compressor.

11. The operating method of the air compressor waste heat comprehensive utilization system according to claim 9, characterized in that: The building heating heat load is calculated by the following formula: Q cn =S×q×10 -3 Among them, Q cn is the building heating heat load; S is the building area of ​​the heating building; q is the building heating heat index; The bathing water heat load is calculated by the following formula: Q xy =c xs ×m xs ×(T sh -T sq ) Among them, Q xy is the heat load of bathing water; c xs is the specific heat capacity of tap water at constant pressure; m xs is the amount of bath water; T sh is the bathing water supply temperature; T sq The temperature of tap water before heating; The heat load of the hanging basket clothes drying is calculated by the following formula: Q hg =c xf ×ρ xf ×V xf ×(T xh -T xq ) Among them, Q hg Heat load for clothes drying; c xf is the constant pressure specific heat capacity of fresh air; ρ xf is the fresh air density; V xf is the fresh air volume flow rate; T xh The temperature of the fresh air after heating; T xq The temperature of fresh air before heating.

12. The operating method of the air compressor waste heat comprehensive utilization system according to claim 1, characterized in that: The equipment capacity constraint is calculated by the following formula: in, is the theoretical capacity of a single heat recovery unit; η ys is the heat exchange efficiency of the air compressor oil cooler; η rh is the heat exchange efficiency of the heat recovery unit; m rh is the capacity of a single heat recovery unit; ξ rh is the long-term output attenuation coefficient of the heat recovery unit; n rh The number of heat recovery units installed; n ky The number of air compressors installed; M rh is the total capacity of the heat recovery unit, Q ys It is the heat taken away by the circulating cooling water in the oil cooler; in, is the theoretical total capacity of the air source heat pump; L ky is the average annual operating load rate of the air compressor; is the number of air compressors in operation; m kr is the capacity of a single air source heat pump on the market; n kr The number of air source heat pumps installed; M kr is the total capacity of the air source heat pump, Q cn is the building heating load, Q xy is the bath water heat load, Q hg Drying heat load for clothes; in, is the theoretical total capacity of the fresh air unit; M xf is the total capacity of the fresh air unit; xf is the long-term output attenuation coefficient of the fresh air unit; m xf is the capacity of a single fresh air unit; n xf The number of fresh air units installed; in, is the theoretical total capacity of the closed self-cleaning heat exchanger; M bh is the total capacity of the closed self-cleaning heat exchanger; bh m is the long-term operation output attenuation coefficient of the closed self-cleaning heat exchanger; bh is the capacity of a single closed self-cleaning heat exchanger; n bh The number of closed self-cleaning heat exchangers installed; The equipment operating characteristic constraints are calculated by the following formula: Among them, y is the output energy power of the equipment; p and q are the performance parameters of the equipment; x is the input energy power of the main equipment; δ is an integer variable, indicating the number of equipment in operation; x is the upper and lower limits of the energy power input of a single device; n is the number of devices installed; The energy flow balance constraints of the system include heat balance of air compressor lubricating oil, heat balance of softening circulating water, heat balance of hanging basket clothes drying and heat balance of bathing water; The heat balance of the air compressor lubricating oil is calculated by the following formula: Among them, x rh is the input heat power of the heat recovery unit; The softening circulating water heat balance is calculated by the following formula: Among them, y kr is the output heat power of the air source heat pump; rh is the output heat power of the heat recovery unit; x xf is the input heat power of the fresh air unit; x bh is the input heat power of the closed self-cleaning heat exchanger; The heat balance of the hanging basket clothes drying is calculated by the following formula: Among them, y xf is the output heat power of the fresh air unit; The bath water heat balance is calculated by the following formula: Among them, y bh It is the output heat power of closed self-cleaning heat exchanger.

13. The operating method of the air compressor waste heat comprehensive utilization system according to claim 1, characterized in that: The equipment operation mode includes: the type of operating equipment, the number of operating equipment, the capacity of the operating equipment and the operating rules of the equipment.

Images