Gas compressor

Abstract

To provide a gas compressor which can adjust the temperature of a heat collection liquid discharged from a waste heat collection heat exchanger to a desired temperature at low cost without involving installation of a temperature adjustment valve or the like in a path of heat collection liquid.SOLUTION: A gas compressor comprises: a heat exchange liquid temperature sensor 34 for detecting a temperature of a heat exchange liquid discharged from a waste heat collection heat exchanger 11; and a path 21 through which at least part of a high-temperature fluid cooled by an air-cooling type cooler 20 flows into a compressor body 1. The gas compressor also comprises a heat exchange liquid temperature sensor 34 for detecting a temperature Tw2 of heat exchange liquid discharged from the waste heat collection heat exchanger 11. A controller 37 has a heat exchange liquid temperature adjustment function for controlling a rotational speed of a cooling fan 30 so that the temperature Tw2 detected by the heat exchange liquid temperature sensor 34 approaches a prescribed target heat exchange liquid temperature Tw2t.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a gas compressor.

Background Art

[0002] Generally, there is known a gas compressor having a waste heat recovery function for recovering heat from high-temperature compressed gas discharged from a gas compressor that compresses a gas such as air and the like, or from lubricating oil that has been injected for lubrication of internal mechanical components of the compressor and improvement of gas compression efficiency and taken out as hot water. For example, Patent Document 1 discloses an oil-cooled gas compressor with a waste heat recovery device that combines an oil-cooled gas compressor that actively injects lubricating oil into the operating space of the compressor body for lubrication of the internal mechanical components of the compressor and improvement of gas compression efficiency and a waste heat recovery device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When recovering waste heat from compressed air and lubricating oil to extract hot water, it is easier to use because a wider range of applications can effectively utilize the heat when the hot water temperature is higher. However, in the oil-cooled gas compressor with a waste heat recovery device of Patent Document 1, the rotational speed of the fan motor is controlled via an inverter so that the difference between the preset target discharge temperature of the compressed air and the current discharge temperature becomes small, and the temperature of the lubricating oil injected into the compressor body is kept within an appropriate range. However, there is no mention of controlling the operation of any rotating body or valve to increase the hot water temperature.

[0005] The present invention has been made in view of the above problems, and an object thereof is to adjust the temperature of the heat recovery liquid discharged from the heat exchanger for exhaust heat recovery to a desired temperature at low cost without providing a temperature control valve or the like in the path of the heat recovery liquid.

Means for Solving the Problems

[0006] In order to achieve the above object, Representative The present invention includes a compressor body that sucks, compresses, and discharges gas, a heat exchanger for exhaust heat recovery that exchanges heat between at least a part of the high-temperature fluid discharged from the compressor body and a heat exchange liquid as a low-temperature fluid, an air-cooled cooler that cools the high-temperature fluid, a cooling fan that blows air to the air-cooled cooler, a controller that controls the rotational speed of the cooling fan, a discharge gas temperature sensor that detects the discharge gas temperature which is the temperature of the compressed gas discharged from the compressor body, the temperature of the heat exchange liquid discharged from the heat exchanger for exhaust heat recovery which is the heat exchange fluid temperature a heat exchange liquid temperature sensor that detects, and a path for flowing at least a part of the high-temperature fluid cooled by the air-cooled cooler into the compressor body 、 and is configured such that the controller Store the correlation between the heat exchange fluid temperature and the discharged gas temperature, set the discharged gas temperature corresponding to a predetermined target heat exchange fluid temperature in the correlation as the target discharged gas temperature, and control the rotational speed of the cooling fan so that the discharged gas temperature approaches the target discharged gas temperature is of a certain type.

[0007] According to the present invention configured as described above, by adjusting the degree of cooling of the high-temperature fluid flowing into the compressor body with the cooling fan, it is possible to adjust the temperature of the high-temperature fluid flowing into the heat exchanger for exhaust heat recovery. As a result, it is possible to adjust the temperature of the heat recovery liquid discharged from the heat exchanger for exhaust heat recovery to a desired temperature at low cost without providing a temperature control valve or the like in the path of the heat recovery liquid.

Effects of the Invention

[0008] According to the gas compressor according to the present invention, it is possible to adjust the temperature of the heat recovery liquid discharged from the heat exchanger for exhaust heat recovery to a desired temperature at low cost without providing a temperature control valve or the like in the path of the heat recovery liquid.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, the same reference numerals are assigned to equivalent elements, and duplicate descriptions will be omitted as appropriate.

Example

[0011] FIG. 1 is a schematic diagram showing a schematic configuration of a gas compressor according to a first embodiment of the present invention. The gas compressor in the present embodiment is an oil-fed air compressor. The compressor main body 1 includes a pair of male and female screw rotors that mesh with each other while being in contact with each other and form an operating space for compressing air between the inner surface of the casing constituting the compressor main body 1. When performing a load operation of supplying compressed air to a demand destination, the compressor main body 1 is driven by the main motor 2, the suction valve 4 opens, and ambient air is sucked into the compressor main body 1 through the suction filter 3. The sucked air is filtered by the suction filter 3, sucked into the compressor main body 1 via the suction valve 4, and the volume of the operating space formed in the compressor main body 1 decreases as the screw rotors rotate, so that the air is compressed to a predetermined pressure and discharged. Lubricating oil is actively injected into the compressor main body 1 for the purpose of lubricating the screw rotors and mechanical components such as bearings (not shown), cooling the compression heat of air in the operating space, and suppressing the backflow of air from the internal minute gaps. The compressed air discharged from the compressor main body 1 flows into the oil primary separator 7 through the discharge air path 6, where a large amount of lubricating oil mixed in the compressed air is separated and stored in the lower part of the oil primary separator 7. The compressed air from which the oil has been primarily separated flows into the oil secondary separator 8, and most of the minute oil droplets and oil fumes remaining in the compressed air are separated. Thereafter, the compressed air after the oil has been secondarily separated flows into the aftercooler 13c through the pressure regulating check valve 9 and the discharge air path 10. The aftercooler 13c is an air-cooled cooler that cools the compressed air with the cooling air generated by the cooling fan 30. The compressed air finally cooled by the aftercooler 13c is supplied to the compressed air demand destination through the discharge air path 14.

[0012] The lubricating oil injected into the compressor body 1 is discharged together with the compressed air and separated by the primary oil separator 7 and the secondary oil separator 8, and then temporarily stored in the lower part of the primary oil separator 7. Due to the pressure inside the primary oil separator 7, the lubricating oil flows through the oil path 15 and the temperature control valve 16, and the total amount flows into the oil path 17, or the total amount flows into the oil bypass path 18, or the flow rate is distributed to the oil path 17 and the oil bypass path 18 respectively. Here, the temperature control valve 16 is a temperature control valve with a mechanical structure that can distribute the flow rate in two directions on the outlet side of the temperature control valve 16 by the expansion of the medium sealed inside according to the temperature of the lubricating oil. If the lubricating oil temperature is lower than a predetermined temperature, the total amount of the lubricating oil flows into the oil bypass path 18, so that the waste heat recovery heat exchanger 11 and the oil cooler 20 described later are bypassed. Therefore, the lubricating oil circulates between the compressor body 1, the primary oil separator 7, and the oil bypass path 18, quickly raising the lubricating oil temperature, preventing the saturated compressed air from being cooled by the cold lubricating oil and generating a large amount of condensed water in the primary oil separator 7, and preventing the viscosity of the oil from becoming too high and increasing the power consumption. On the other hand, when the lubricating oil temperature is higher than a predetermined temperature, the total amount flows into the oil flow path in the waste heat recovery heat exchanger 11 through the oil path 17, heats the water, which is a low-temperature fluid, to perform waste heat recovery. Then, the lubricating oil flows into the oil cooler 20 through the oil path 19. The oil cooler 20 is an air-cooled cooler similar to the aftercooler 13c. After the lubricating oil is cooled by the cooling air in the oil cooler 20, it is injected into the compressor body 1 again through the oil path 21 and the oil filter 22. Incidentally, the cooling fan 30, the aftercooler 13c, and the oil cooler 20 are installed inside the fan duct 46, or the opening of the fan duct 46 is connected to the ventilation parts of the aftercooler 13c and the oil cooler 20.

[0013] Regarding the heat exchanger 11 for heat recovery, as the low-temperature fluid, water flows from the water supply source through the water supply path 31 into the water flow path in the heat exchanger 11 for heat recovery. As the high-temperature fluid, the water is heated by the high-temperature lubricating oil flowing in the heat exchanger 11 for heat recovery, then flows out to the water supply path 32 and is supplied to the hot water demand destination. Thereby, the heat of the lubricating oil, which is the high-temperature fluid, can be taken out as hot water, and the taken-out hot water can be effectively used for various purposes such as preheating the boiler feed water and heat preservation, and it is possible to reduce the fuel and electricity that were conventionally required to produce hot water. The water temperature supplied from the water supply source is detected by the water inlet temperature sensor 33 provided on the water supply path 31 upstream of the water flow path inlet in the heat exchanger 11 for heat recovery as the water inlet temperature Tw1, and the hot water temperature heated and taken out by the heat exchanger 11 for heat recovery is detected by the water outlet temperature sensor 34 provided on the water supply path 32 downstream of the water flow path outlet in the heat exchanger 11 for heat recovery as the water outlet temperature Tw2.

[0014] The main motor 2 of this compressor can have its rotational speed controlled by the frequency output by the main motor inverter 35, and the rotational speed of the main motor 2 is controlled so that the unit outlet discharge air pressure Pd detected by the unit outlet discharge air pressure sensor 28 provided in the discharge air path 14 becomes a predetermined set pressure. When the amount of compressed air used decreases and the unit outlet discharge air pressure Pd exceeds the predetermined set pressure, this compressor switches from the previous load operation to no-load operation. At this time, the main motor inverter 35 outputs the lower limit frequency, decelerates the main motor 2 to the lower limit rotational speed, and closes the suction valve 4, so that air is sucked only from the minute gap formed between the valve box and the valve body of the suction valve 4, thereby reducing the amount of sucked air and reducing the power consumption of the compressor. During no-load operation, due to the function of the pressure regulating check valve 9, the upstream side thereof, that is, the upstream side from the oil primary separator 7, is maintained at the minimum pressure required to supply lubricating oil to the compressor body 1.

[0015] The cooling fan 30 can have its rotational speed controlled according to the frequency output by the inverter 36 for the cooling fan. The inverter 36 for the cooling fan changes the frequency it outputs so that the value of the discharge air temperature Td1 detected by the discharge air temperature sensor 25 provided in the discharge air path 6 becomes near a predetermined temperature, and the rotational speed of the cooling fan 30 is controlled. The main control board 37 (controller) controls the entire compressor, including the inverter 35 for the main motor, the inverter 36 for the cooling fan, and other sensors and valves.

[0016] Here, the discharge air temperature Td1 and the temperature of the lubricating oil are substantially the same. This is because the lubricating oil is supplied into the working chamber inside the compressor body 1 and cools the compression heat generated in the process of compressing air. Therefore, the temperature of the lubricating oil discharged together with the compressed air from the compressor body 1 is substantially the same as the discharge air temperature Td1. In an oil-cooled compressor, the lubricating oil temperature before flowing out of the compressor body 1 and before heat exchange with another fluid can be substituted by the discharge air temperature Td1.

[0017] Here, a method for taking out arbitrary warm water from the low-temperature fluid flow path outlet of the waste heat recovery heat exchanger 11 will be described. FIG. 3 is a diagram showing the inlet temperatures and outlet temperatures of the high-temperature fluid (lubricating oil) and the low-temperature fluid (water) of the waste heat recovery heat exchanger 11 in this embodiment. The waste heat recovery heat exchanger 11 is a counter-flow type heat exchanger, and the logarithmic mean temperature difference ΔTm at this time is generally expressed by the following formula. ΔTm = ((Td1 - Tw2) - (Td2 - Tw1)) / LN((Td1 - Tw2) / (Td2 - Tw1)) When the amount of water flowing into the heat exchanger 11 for waste heat recovery and the water inlet temperature Tw1 are constant, in order to raise the water outlet temperature Tw2 of the hot water flowing out after being heated by the waste heat recovery heat exchanger 11 to the target water outlet temperature Tw2t (assuming Tw2 < Tw2t), it is only necessary to raise the lubricating oil temperature on the high-temperature side. In an oil-cooled compressor, since the lubricating oil temperature is the same as the discharge air temperature Td1, the discharge air temperature Td1 is raised to the target discharge air temperature Td1t (assuming Td1 < Td1t). At this time, in order to obtain the target water outlet temperature Tw2t, if the target discharge air temperature Td1t is determined so that the logarithmic mean temperature difference ΔTm is constant, the characteristics shown in FIG. 3 can be obtained.

[0018] By calculating in advance the relationship between the target water outlet temperature Tw2t and the target discharge air temperature Td1t for the heat exchanger that has been adopted and preparing a characteristic curve, when the operator sets an arbitrary target water outlet temperature Tw2t, the corresponding target discharge air temperature Td1t can be easily obtained. Curve 1 in FIG. 4 is a characteristic curve representing the relationship between the target water outlet temperature Tw2t and the target discharge air temperature Td1t in this embodiment. When an arbitrary target water outlet temperature Tw2t is set, the cooling fan inverter output frequency Ff may be feedback-controlled so that the corresponding target discharge air temperature Td1t is obtained, and the discharge air temperature Td1 may be adjusted.

[0019] The gas compressor in this embodiment is provided with a hot water priority mode (waste heat recovery liquid temperature adjustment function) as an operation mode for controlling the rotational speed of the cooling fan 30 so that the water outlet temperature Tw2 is near the temperature of the hot water supplied to the demand destination (target water outlet temperature Tw2t). The switching operation of enabling or disabling the hot water priority mode can be arbitrarily performed by the operator of the compressor via the input and display device 38 (switching instruction device).

[0020] Figure 2 is a flowchart showing the control procedure when the hot water priority mode is set to be effective. Step 101 is the starting point of the control procedure in this embodiment. In step 102, it is a procedure to determine whether the hot water priority mode is effective. If it is effective, the process proceeds to step 103. If it is not effective, the process proceeds to step 112 and this flowchart ends. In step 103, the current discharged air temperature Td1, the water outlet temperature Tw2, and the cooling fan inverter output frequency Ff are obtained. Further, the hot water priority mode discharged air upper limit temperature Td1r, which is set slightly lower than the discharged air alarm temperature Td1A when the hot water priority mode is invalid, is enabled. Next, in step 104, it is determined whether the discharged air temperature Td1 is greater than or equal to the fan control start discharged air temperature Td1f. If Td1f ≤ Td1 holds, the process proceeds to step 105. If Td1f > Td1, the process proceeds to step 106 to stop the cooling fan so that the temperature of the lubricating oil does not become too low. In step 105, it is a procedure to determine whether the discharged air temperature Td1 is lower than the hot water priority mode discharged air upper limit temperature Td1r. If Td1 < Td1r holds, the process proceeds to step 107. If Td1r ≤ Td1, since the discharged air temperature Td1 is approaching the discharged air alarm temperature Td1A, the cooling fan inverter output frequency Ff is set to the cooling fan inverter maximum output frequency Ffmax, and the cooling fan is operated at full speed to quickly reduce the discharged air temperature Td1. Next, step 107 is a procedure to determine whether the water outlet temperature Tw2 is equal to the target water outlet temperature Tw2t. If Tw2 = Tw2t holds, the process proceeds to step 112 and this flowchart ends. If this does not hold, the process proceeds to step 109. Steps 109 to 111 are procedures for controlling so that the water outlet temperature Tw2 becomes equal to the target water outlet temperature Tw2t. First, in step 109, the target discharged air temperature Td1t is recalculated. Next, it is determined whether the current discharged air temperature Td1 is equal to the target discharged air temperature Td1t recalculated in step 109. That is, if Td1 = Td1t holds, the procedure returns to immediately before step 103.On the other hand, when Td1 = Td1t does not hold, the process proceeds to step 111, and the output frequency Ff of the cooling fan inverter is feedback-controlled in a loop until Td1 = Td1t holds. As a result of the control of the output frequency of the cooling fan inverter, when Td1 = Td1t, the procedure returns to immediately before step 103 as described above. Through this series of controls, warm water at Tw2 = Tw2t can be supplied to the warm water demand destination. However, in steps 107 and 110, it is not necessary to strictly make the current water outlet temperature Tw2 and the discharge air temperature Td1 equal to their respective target temperatures, and a certain tolerance range may be provided with respect to the target temperature. For example, if a tolerance range of a °C and b °C is ensured as (Tw2t - a)[°C] ≤ Tw2[°C] ≤ (Tw2t - a)[°C] and (Td1t - b)[°C] ≤ Td1[°C] ≤ (Td1t + b)[°C], chattering on the control flowchart can be prevented. By making the a °C and b °C of the tolerance range arbitrarily settable by the operator, it is useful for adjusting how much fluctuation in the case of a sudden temperature change in the ambient environment, etc. is absorbed.

[0021] In step 109, the target discharge air temperature Td1t corresponding to the target water outlet temperature Tw2t may be obtained from the characteristic curve of the heat exchanger 11 for waste heat recovery shown by curve 1 in FIG. 4. The data of curve 1 in FIG. 4 is stored in the main control board 37, and the target discharge air temperature Td1t obtained by inputting the target water outlet temperature Tw2t is used as the output value, and this is set as the target discharge air temperature in the warm water priority mode. Thereafter, by feedback-controlling the output frequency Ff of the cooling fan inverter so that the discharge air temperature Td1 becomes the target discharge air temperature Td1t in step 110, the water outlet temperature Tw2 can be controlled to become the target water outlet temperature Tw2t as a result.

[0022] As an effect of the above-described method for controlling the water outlet temperature Tw2, conventionally, it has been necessary to provide a temperature control valve on the water supply line to adjust the temperature of the hot water to be taken out, which has contributed to an increase in the number of construction man-hours and costs. Furthermore, in order to keep the hot water temperature constant, the flow rate has been restricted by adjusting the opening degree of the temperature control valve, and there has been a case where hot water with a constant flow rate cannot always be used at the hot water demand destination. In response to such problems, in this embodiment, by simply adding a water outlet temperature sensor 34 to the cooling fan 30, the inverter 36 for the cooling fan, and the discharge air temperature sensor 25, which are standard equipment in the compressor, hot water at a predetermined target temperature can be supplied easily and at low cost.

[0023] FIG. 5 is a flowchart showing a modified example of the control procedure (FIG. 2) for adjusting the water outlet temperature Tw2 to the target water outlet temperature Tw2t. Hereinafter, the description will focus on the differences from the flowchart of FIG. 2. In the flowchart of FIG. 5, when Td1 < Td1r holds in step 105, the process proceeds to step 107a. In step 107a, instead of the discharge air temperature Td1, which was the target value for controlling the rotational speed of the cooling fan, the water outlet temperature Tw2 is switched to be detected. Next, in step 107b, if the relationship Tw2 = Tw2t holds between the water outlet temperature Tw2 and the target water outlet temperature Tw2t, this flowchart ends. If it does not hold, the process proceeds to step 111, where the feedback control of the cooling fan inverter output frequency Ff is performed until Tw2 = Tw2t holds.

[0024] According to the flowchart of FIG. 5, the water outlet temperature Tw2 can be controlled more directly than the flowchart of FIG. 2, and it is easier to obtain the target water outlet temperature Tw2t.

[0025] An oil separator outlet air temperature sensor 48 is provided in the discharge air path 10, and it detects the oil separator outlet air temperature Tdsp. This is mainly provided for the purpose of prompting the operator to replace the oil secondary separator 8 or the lubricating oil when the discharge air temperature exceeds a predetermined temperature due to the heat generated by the oxidation over time of the collected oil fumes and oil droplets inside the oil secondary separator 8. Usually, the oil separator outlet air temperature Tdsp and the discharge air temperature Td1 are substantially the same, and the oil separator outlet air temperature Tdsp may be used instead of the discharge air temperature Td1 in the flowchart of FIG. 2.

[0026] (Summary) In this embodiment, a gas compressor includes a compressor main body 1 that sucks, compresses, and discharges gas, an exhaust heat recovery heat exchanger 11 that exchanges heat between at least a part (lubricating oil) of the high-temperature fluid (compressed air and lubricating oil) discharged from the compressor main body 1 and a heat exchange fluid as a low-temperature fluid, air-cooled coolers 13c, 20 that cool the high-temperature fluid, a cooling fan 30 that blows air to the air-cooled coolers 13c, 20, a controller 37 that controls the rotation speed of the cooling fan 30, and a discharge gas temperature sensor 25 that detects the discharge gas temperature which is the temperature of the compressed gas discharged from the compressor main body 1. The gas compressor further includes a heat exchange fluid temperature sensor 34 that detects the temperature of the heat exchange fluid discharged from the exhaust heat recovery heat exchanger 11, and a path (oil path 21) that allows at least a part (lubricating oil) of the high-temperature fluid (compressed air and lubricating oil) cooled by the air-cooled coolers 13c, 20 to flow into the compressor main body 1. The controller 37 has a heat exchange fluid temperature adjustment function of controlling the rotation speed of the cooling fan 30 so that the temperature Tw2 detected by the heat exchange fluid temperature sensor 34 approaches a predetermined target heat exchange fluid temperature Tw2t.

[0027] According to the present embodiment configured as described above, by adjusting the degree of cooling of the high-temperature fluid (lubricating oil) flowing into the compressor main body 1 with the cooling fan 30, it is possible to adjust the temperature of the high-temperature fluid (lubricating oil) flowing into the exhaust heat recovery heat exchanger 11. As a result, it is possible to adjust the temperature Tw2 of the heat recovery fluid discharged from the exhaust heat recovery heat exchanger 11 to a desired temperature Tw21 at low cost without providing a temperature adjustment valve or the like in the path of the heat recovery fluid.

[0028] Further, the controller 37 in this embodiment stores the correlation (curve 1 in FIG. 4) between the temperature Tw2 of the heat exchange liquid discharged from the heat exchanger 11 for exhaust heat recovery and the temperature Td1 of the compressed gas discharged from the compressor main body 1. In the correlation, the discharge gas temperature Td1 corresponding to the temperature Tw2 of the heat exchange liquid that coincides with the predetermined temperature is set as the target discharge gas temperature Td1t, and the rotation speed of the cooling fan 30 is controlled so that the temperature detected by the discharge gas temperature sensor 25 approaches the target discharge gas temperature Td1t. Thereby, it becomes possible to adjust the temperature Tw2 of the heat exchange liquid based on the discharge gas temperature Td1.

[0029] Also, the gas compressor in this embodiment includes a switching instruction device 38 that instructs activation or deactivation of the heat recovery liquid temperature adjustment function. When the controller 37 is instructed to activate the heat recovery liquid temperature adjustment function from the switching instruction device 38, the rotation speed of the cooling fan 30 is controlled so that the temperature Tw2 detected by the heat exchange liquid temperature sensor 34 approaches a predetermined target heat exchange liquid temperature Tw2t. When the controller 37 is instructed to deactivate the heat recovery liquid temperature adjustment function from the switching instruction device 38, the rotation speed of the cooling fan 30 is controlled so that the discharge gas temperature Td1 approaches a predetermined target discharge gas temperature Td1t. Thereby, it becomes possible to activate or deactivate the heat recovery liquid temperature adjustment function as needed.

[0030] Further, the compressor main body 1 in this embodiment is a liquid supply type in which a lubricating liquid is injected into the internal operating chamber, and the high-temperature fluid flowing into the heat exchanger 11 for exhaust heat recovery contains the lubricating liquid (lubricating oil) discharged from the compressor main body 1. Thereby, in a liquid supply type compressor, it is possible to adjust the temperature Tw2 of the heat recovery liquid discharged from the heat exchanger 11 for exhaust heat recovery to a desired temperature Tw2t at low cost without providing a temperature adjustment valve or the like in the path of the heat recovery liquid.

Embodiment

[0031] FIG. 6 is a schematic diagram showing a schematic configuration of the gas compressor in the second embodiment of the present invention. Hereinafter, the description will focus on the differences from the first embodiment.

[0032] The gas compressor in this embodiment is provided with a lubricating oil inlet temperature sensor 27 in the oil path 17. Instead of the discharge air temperature Td1 detected by the discharge air temperature sensor 25, the lubricating oil inlet temperature To1 detected by the lubricating oil inlet temperature sensor 27 is used to adjust the water outlet temperature Tw2. The flowchart for adjusting the water outlet temperature Tw2 of the main control board 37 in this embodiment corresponds to the one obtained by replacing the discharge air temperature Td1 in the flowchart of the first embodiment (shown in FIG. 2) with the lubricating oil inlet temperature To1. Also, as the characteristic curve showing the relationship between the target water outlet temperature Tw2t and the target lubricating oil inlet temperature To1t, the curve 1 in FIG. 4 may be used, or a dedicated characteristic curve of the target water outlet temperature Tw2t and the target lubricating oil inlet temperature To1t may be created in advance, stored, and used.

[0033] (Summary) The gas compressor in this embodiment adjusts the temperature Tw2 of the heat exchange liquid based on the lubricating oil inlet temperature To1.

[0034] Also in this embodiment configured as described above, similar to the first embodiment, without providing a temperature control valve or the like in the path of the heat recovery liquid, it is possible to adjust the temperature of the heat recovery liquid discharged from the heat exchanger 11 for waste heat recovery to a desired temperature at low cost.

Embodiment

[0035] FIG. 7 is a schematic diagram showing the schematic configuration of the gas compressor in the third embodiment of the present invention. Hereinafter, the description will focus on the differences from the first embodiment.

[0036] The heat exchanger 11A for waste heat recovery in this embodiment is equipped with two systems for high-temperature fluid flow paths, one for gas and one for liquid. After most of the oil has been separated through the oil primary separator 7 and the oil secondary separator 8, the compressed air flows into the gas-side high-temperature fluid flow path of the heat exchanger 11A for waste heat recovery via the discharge air path 10. The lubricating oil flows into the liquid-side high-temperature fluid flow path of the heat exchanger 11A for waste heat recovery via the oil path 17, similar to FIG. 1. At this time, by exchanging heat with the high-temperature compressed air and lubricating oil as the high-temperature fluid and water as the low-temperature fluid, waste heat recovery from the compressed air is carried out. Thereafter, the compressed air flows into the aftercooler 13c via the discharge air path 12.

[0037] (Summary) The compressor main body 1 in this embodiment is a liquid supply type in which lubricating liquid is injected into the internal operating chamber. The high-temperature fluid flowing into the heat exchanger 11A for waste heat recovery includes the compressed gas and the lubricating liquid discharged from the compressor main body 1.

[0038] According to this embodiment configured as described above, since heat exchange can be performed between both the compressed air and oil, which are high-temperature fluids, and water, which is a low-temperature fluid, it is possible to make the amount of recoverable heat larger than that in the first embodiment.

Embodiment

[0039] FIG. 8 is a schematic diagram showing the schematic configuration of the gas compressor in the fourth embodiment of the present invention. Hereinafter, the description will focus on the differences from the first embodiment.

[0040] The compressor bodies 1L and 1H in this embodiment adopt a two-stage compression method with a low-pressure stage compressor body 1L and a high-pressure stage compressor body 1H. The low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H are attached to the gear case 39, and a low-pressure stage pinion 41 and a high-pressure stage pinion 42 are attached to the driven shaft ends of the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H respectively. A bull gear 40 is attached to the drive shaft of the main motor 2, and the low-pressure stage pinion 41 and the high-pressure stage pinion 42 mesh with the bull gear 40. When the main motor 2 rotates, the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H are driven. An oil pump 45 is connected to the driven shaft end side of the low-pressure stage compressor body 1L via a shaft coupling or a transmission gear (not shown) and is driven by the rotation of the driven shaft of the low-pressure stage compressor body 1L.

[0041] The air sucked in through the suction filter 3, the suction valve 4, and the intake passage 5 flows into the low-pressure stage compressor body 1L. The compressed air boosted to a predetermined low-pressure stage discharge pressure flows into the high-pressure stage compressor body 1H via the discharge air passage 6a. Here, the compressed air boosted to a predetermined discharge pressure flows into the oil primary separator 7 via the discharge air passage 6b. The subsequent discharge air system is the same as that in FIG. 1.

[0042] Regarding the oil passage, the configuration from the oil primary separator 7 to the oil filter 22 is the same as that in FIG. 1. However, the lubricating oil after passing through the oil filter 22 is supplied to each gear inside the gear case 39, shaft sealing parts (not shown), bearings, etc., and is also supplied to the screw rotors, bearings, etc. inside the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H to lubricate these driving parts. Also, the oil pump 45 sucks the lubricating oil staying at the lower part of the gear case 39 through the oil passage 15a, then pumps it through the oil passage 15b and injects it into the intake passage 5. The oil flows into the low-pressure stage compressor body 1L together with the sucked air to seal the air in the working chamber and lubricate the screw rotors.

[0043] The basic configurations of the heat exchanger 11 for heat recovery, the oil cooler 20 that finally cools lubricating oil and compressed air, the aftercooler 13c, and the water supply path, oil path, and discharge air path connected thereto are the same as those in FIG. 1. Also, the configuration of the cooling fan 30, the inverter 36 for the cooling fan that controls it, and various temperature and pressure sensors is the same as that in the first embodiment (FIG. 1). Therefore, the flowchart of the first embodiment (FIG. 2 or FIG. 5) can be executed in the same manner, and in calculating the target discharge air temperature Td1t corresponding to the target water outlet temperature Tw2t, the characteristic curve corresponding to curve 1 in FIG. 4 can be used.

[0044] Also, as in this embodiment, regardless of the number of compressor bodies and the drive method, it is possible to configure a function for recovering waste heat from lubricating oil, which is a high-temperature fluid, and a function for supplying warm water at the target water outlet temperature Tw2t. Generally, an oil-cooled compressor incorporating a plurality of compressor bodies is equipped with a high-output motor, and the amount of circulating lubricating oil also increases. Therefore, the amount of recovered heat from waste heat becomes relatively large, and the amount of warm water that can be supplied also increases, resulting in a higher energy-saving effect. Since the amount of warm water is large, a large water temperature regulating valve that was necessary in the prior art is no longer required, and the effect of reducing installation costs is also significant.

[0045] (Summary) The compressor bodies 1L and 1H in this embodiment are multi-stage.

[0046] According to this embodiment configured as described above, in a multi-stage gas compressor, it is possible to adjust the temperature of the heat recovery liquid discharged from the heat exchanger for heat recovery to a desired temperature at low cost without providing a temperature regulating valve or the like in the path of the heat recovery liquid.

Embodiment

[0047] FIG. 9 is a schematic diagram showing a schematic configuration of a gas compressor in the fifth embodiment of the present invention. Hereinafter, the description will focus on the differences from the first embodiment.

[0048] The gas compressor in this embodiment is an oil-free (liquid-free) type that does not inject coolant or lubricating oil into the working chamber of the compressor body, and is a two-stage compression method including a low-pressure stage compressor body 1L and a high-pressure stage compressor body 1H. The low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H contain a pair of male and female screw rotors (not shown) inside, and can rotate non-contact while maintaining a minute gap with each other by means of synchronous gears provided at the shaft ends of the screw rotors.

[0049] The low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H are attached to the gear case 39, and a low-pressure stage pinion 41 and a high-pressure stage pinion 42 are attached to the driven shaft ends of the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H respectively. A bull gear 40 is attached to the drive shaft of the main motor 2, and the low-pressure stage pinion 41 and the high-pressure stage pinion 42 mesh with the bull gear 40, and the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H are driven by the rotation of the main motor 2. An oil pump pinion 43 is provided at the drive shaft end of the main motor 2, and the oil pump pinion 43 meshes with an oil pump gear 44 provided on the driven shaft of the oil pump 45, and the oil pump 45 is driven by the main motor 2.

[0050] The compressed air discharged from the low-pressure stage compressor body 1L flows through the discharge air path 6a into the high-temperature fluid flow path of the low-pressure stage exhaust heat recovery heat exchanger 11L, and exchanges heat with the water passing through the low-temperature fluid flow path. Then, it is cooled to a predetermined temperature by the intercooler 13a via the discharge air path 6b. Thereafter, the compressed air is separated from the condensed water by the condensed water separator 7a provided on the discharge air path 6c and then flows into the high-pressure stage compressor body 1H. That is, the discharge air path 6c is a path for allowing the high-temperature fluid (compressed air) cooled by the air-cooled cooler (intercooler 13a) to flow into the compressor body (high-pressure stage compressor body 1H). The compressed air boosted to a predetermined pressure by the high-pressure stage compressor body 1H flows through the discharge air path 10a into the high-temperature fluid flow path of the high-pressure stage exhaust heat recovery heat exchanger 11H, and exchanges heat with the water passing through the low-temperature fluid flow path. Then, it flows out to the discharge air path 12, is precooled by the cooling air generated by the cooling fan 30 in the air-cooled pre-cooler 13b provided on the discharge air path 12, passes through the check valve 9a, and flows into the after-cooler 13c. After the compressed air is cooled by the cooling air in the after-cooler 13c, it is supplied to the demand destination via the discharge air path 14.

[0051] On the other hand, even in an oil-free compressor that does not supply oil to the operating chamber of the compressor body, lubricating oil is required for lubricating drive parts such as gears and bearings (not shown) and for cooling the compressor body casing that becomes hot due to the compression heat of air. An oil pump is necessary to circulate the lubricating oil. The oil pump 45 driven by the main motor 2 sucks the lubricating oil stored in the lower part of the gear case 39 through the oil path 15a and pumps it through the oil path 15b. A temperature control valve 16 is provided on the oil path 15b. When the lubricating oil temperature is lower than a predetermined temperature, the entire amount of the lubricating oil bypasses the oil cooler 20 by passing through the oil bypass path 18, passes through the oil path 21, the oil filter 22, and the oil path 23a, and is supplied to the low-pressure stage compressor body 1L through the oil path 23b branched from the oil path 23a and to the high-pressure stage compressor body 1H through the oil path 23a. In addition to being used for lubricating bearings (not shown) inside the compressor body and synchronous gears for rotating a pair of male and female screw rotors in a non-contact manner, the lubricating oil also flows through a coolant flow path (a flow path separated so as not to mix with compressed air, not shown) formed in the casing constituting the compressor body, and is also used for cooling the compressor body. Further, the lubricating oil is also supplied to drive parts such as each gear and bearing inside the gear case 39 through other branched oil paths (not shown). When the lubricating oil temperature becomes higher than the predetermined temperature, the temperature control valve 16 adjusts the distribution of the oil volume to the oil bypass path 18 and the oil path 17 according to the lubricating oil temperature. The lubricating oil flows into the oil cooler 20 through the oil path 17, is cooled by the cooling air, and finally is supplied to the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H through the oil path 21. That is, the oil path 21 is a path for allowing the high-temperature fluid (lubricating oil) cooled by the air-cooled cooler (oil cooler 20) to flow into the compressor body (low-pressure stage compressor body 1L and high-pressure stage compressor body 1H).

[0052] In this embodiment, the configuration is such that water and compressed air are heat-exchanged in series, first with the low-pressure stage exhaust heat recovery heat exchanger 11L and then with the high-pressure stage exhaust heat recovery heat exchanger 11H. To explain in detail, the water that has passed through the water supply path 31a flows into the low-temperature fluid flow path of the low-pressure stage exhaust heat recovery heat exchanger 11L and is heated by the high-temperature compressed air discharged from the low-pressure stage compressor body 1L. Thereafter, the water flows into the low-temperature fluid flow path of the high-pressure stage exhaust heat recovery heat exchanger 11H via the water supply path 31b, is heated by the high-temperature compressed air discharged from the high-pressure stage compressor body 1H, and is finally supplied from the water supply path 32 to the hot water demand destination. Here, in this embodiment, it is assumed that the compression ratio, which is the ratio of the suction pressure to the discharge pressure, is smaller for the low-pressure stage compressor body 1L than for the high-pressure stage compressor body 1H, and since the discharge air temperature at the outlet of the low-pressure stage compressor body 1L is lower, in order to make the heat exchange amount as large as possible, it is more preferable to heat-exchange the coldest water supplied from the water supply source first with the low-pressure stage discharge air. However, if the compression ratio of the high-pressure stage compressor body 1H is designed to be smaller than that of the low-pressure stage compressor body 1L, the connection order of the exhaust heat recovery heat exchangers may be the high-pressure stage exhaust heat recovery heat exchanger 11H first and then the low-pressure stage exhaust heat recovery heat exchanger 11L.

[0053] In the case of an oil-free compressor, most of the generated heat exists as the sensible heat of the compressed air, and as in this embodiment, heat exchange with water is often performed for exhaust heat recovery from the compressed air. Although there is no exhaust heat recovery from oil in this embodiment, similar to the flowchart of the first embodiment (Figure 2), the rotation of the cooling fan 30 may be controlled so that the water outlet temperature Tw2 becomes the target water outlet temperature Tw2t.

[0054] FIG. 10 is a flowchart showing a control procedure for adjusting the water outlet temperature Tw2 to the target water outlet temperature Tw2t in the gas compressor according to this embodiment. In this embodiment, instead of the discharge air temperature Td1 in the first embodiment, the high-pressure stage discharge air temperature TdH1 is used. Also, instead of the discharge air alarm temperature Td1A, the high-pressure stage discharge air temperature TdH1A is used. Further, when the hot water priority mode is effective, instead of the discharge air upper limit temperature Td1r in the hot water priority mode, the high-pressure stage discharge air upper limit temperature TdH1r in the hot water priority mode is used. Also, instead of the fan control start discharge air temperature Td1f, the fan control start high-pressure stage discharge air temperature TdH1f is used. Further, instead of the target discharge air temperature Td1t, the target high-pressure stage discharge air temperature TdH1t is used. Although the parameters used for condition judgment are changed as described above, the processing of each step in FIG. 10 is the same as that in the first embodiment (FIG. 2).

[0055] FIG. 11 is a diagram showing the inlet temperatures and outlet temperatures of the high-temperature fluid (compressed air) and the low-temperature fluid (water) in the low-pressure stage exhaust heat recovery heat exchanger 11L and the high-pressure stage exhaust heat recovery heat exchanger 11H in this embodiment. Both the low-pressure stage exhaust heat recovery heat exchanger 11L and the high-pressure stage exhaust heat recovery heat exchanger 11H are counterflow type heat exchangers. At this time, the low-pressure stage logarithmic mean temperature difference ΔTmL of the low-pressure stage exhaust heat recovery heat exchanger 11L is ΔTmL = ((TdL1 - TwL2) - (TdL2 - TwL1)) / LN((TdL1 - TwL2) / (TdL2 - TwL1)) represented by. On the other hand, the high-pressure stage logarithmic mean temperature difference ΔTmH of the high-pressure stage exhaust heat recovery heat exchanger 11H is ΔTmH = ((TdH1 - TwH2) - (TdH2 - TwH1)) / LN((TdH1 - TwH2) / (TdH2 - TwH1)) represented by.

[0056] Since the low-pressure stage heat recovery heat exchanger 11L and the high-pressure stage heat recovery heat exchanger 11H are connected in series, the amount of water flowing into each is the same. Assuming that this amount of water is constant at all times and the water inlet temperature (= low-pressure stage low-temperature fluid inlet temperature) TwL1 is also constant, the low-pressure stage low-temperature fluid outlet temperature TwL2 of the low-pressure stage heat recovery heat exchanger 11L and the high-pressure stage low-temperature fluid inlet temperature TwH1 of the high-pressure stage heat recovery heat exchanger 11H are the same temperature, and the relationship is TwH1 = TwL2 (here, it is assumed that the water supply passage 31b is protected by a heat insulating material or the like and there is no heat transfer).

[0057] The low-pressure stage high-temperature fluid outlet temperature TdL2 of the compressed air cooled and flowing out from the low-pressure stage high-temperature fluid outlet after heat exchange with water in the low-pressure stage heat recovery heat exchanger 11L is further cooled to around the atmospheric temperature + 15°C in the intercooler 13a. Then, it is compressed by the high-pressure stage compressor main body 1H and flows into the high-pressure stage heat recovery heat exchanger 11H at the high-pressure stage discharge air temperature (= high-pressure stage high-temperature fluid inlet temperature) TdH1. Therefore, usually, even though the low-pressure stage high-temperature fluid outlet temperature TdL2 and the high-pressure stage high-temperature fluid inlet temperature TdH1 are connected in series, they do not match like the low-pressure stage low-temperature fluid outlet temperature TwL2 and the high-pressure stage low-temperature fluid inlet temperature TwH1.

[0058] In a general oil-free compressor, the discharge air temperature (absolute temperature) immediately after compression [K] is obtained by (suction air absolute temperature) × ((discharge air absolute pressure / suction air absolute pressure)^((κ - 1) / (m·κ))). Here, κ is the specific heat ratio of air (= 1.4), and m is the number of compression stages. Although it depends on the discharge pressure specification of the compressor, when the discharge air pressure specification is 0.7 MPa (gauge pressure), since it is common to design so that the compression ratios of the low-pressure stage and the high-pressure stage (=(discharge air absolute pressure / suction air absolute pressure)) are of the same degree, when the discharge air temperatures of the low-pressure stage compressor main body 1L and the high-pressure stage compressor main body 1H are calculated individually with m = 1, the low-pressure stage and high-pressure stage compressor main body outlet temperatures, that is, the low-pressure stage discharge air temperature (= low-pressure stage high-temperature fluid inlet temperature) TdL1 and the high-pressure stage discharge air temperature (= high-pressure stage high-temperature fluid inlet temperature) TdH1 are around 180 - 210°C.

[0059] Similar to the first embodiment, in order to increase the high-pressure stage low-temperature fluid outlet temperature of the heat exchanger 11H for high-pressure stage exhaust heat recovery, that is, the water outlet temperature TwH2, to the target water outlet temperature TwH2t (TwH2 < TwH2t), it is only necessary to increase the low-pressure stage high-temperature fluid inlet temperature TdL1 and the high-pressure stage high-temperature fluid inlet temperature TdH1. Unlike the oil-cooled compressor, the oil-free compressor does not inject lubricating oil into the operating chamber of the compressor body. However, by reducing the rotational speed of the cooling fan 30, the lubricating oil temperature at the outlet of the oil cooler 20 increases, resulting in a decrease in the cooling capacity of the lubricating oil flowing through the coolant flow paths (not shown) of the low-pressure stage compressor body 1L and the high-pressure stage compressor body 1H. At the same time, the cooling capacity of the intercooler 13a also decreases due to the reduction in the rotational speed of the cooling fan 30. As a result, the low-pressure stage discharge air temperature (= low-pressure stage high-temperature fluid inlet temperature) TdL1 of the low-pressure stage compressor body 1L and the high-pressure stage discharge air temperature (= high-pressure stage high-temperature fluid inlet temperature) TdH1 of the high-pressure stage compressor body 1H increase, thereby making it possible to increase the water outlet temperature TwH2.

[0060] When the low-pressure stage water inlet temperature TwL1 is given and the high-pressure stage water outlet temperature TwH2 = TwH2t is set, if the target high-pressure stage discharge air temperature TdH1t is determined such that the low-pressure stage logarithmic mean temperature difference ΔTmL and the high-pressure stage logarithmic mean temperature difference ΔTmH remain the same before and after the setting of the high-pressure stage water outlet temperature TwH2, the characteristics shown in FIG. 11 can be obtained.

[0061] Similar to the first embodiment, in advance, the relationship between the target high-pressure stage water outlet temperature TwH2t and the target high-pressure stage discharge air temperature TdH1t is calculated using the combination of the low-pressure stage exhaust heat recovery heat exchanger 11L and the high-pressure stage exhaust heat recovery heat exchanger 11H that are employed, and a characteristic curve is prepared. By doing so, when the operator sets an arbitrary target high-pressure stage water outlet temperature TwH2t, the corresponding target high-pressure stage discharge air temperature TdH1t can be easily obtained. Curve 2 in FIG. 4 is a characteristic curve representing the relationship between the target high-pressure stage water outlet temperature TwH2t and the target high-pressure stage discharge air temperature TdH1t in this embodiment. When an arbitrary target high-pressure stage water outlet temperature TwH2t is set, according to the flowchart in FIG. 10, the cooling fan inverter output frequency Ff is feedback-controlled so that the corresponding target high-pressure stage discharge air temperature TdH1t can be obtained, and the high-pressure stage discharge air temperature TdH1 can be adjusted.

[0062] However, even if an attempt is made to set the target high-pressure stage water outlet temperature TwH2t to a temperature significantly lower than normal, since the low-pressure stage discharge air temperature TdL1 and the high-pressure stage discharge air temperature TdH1 are physically determined by the suction air temperature and the compression ratio, as a result of the feedback control of the cooling fan inverter output frequency Ff, when the cooling fan 30 operates at full speed, that is, when the cooling fan inverter reaches the maximum output frequency Ffmax, if the unit outlet discharge air pressure Pd is constant, there is also a lower limit for the target high-pressure stage discharge air temperature TdH1t. For example, when the atmospheric temperature is 20°C, the lower limit value of the target high-pressure stage discharge air temperature TdH1t is expected to be around 170°C.

[0063] FIG. 12 is a flowchart showing a modified example of the control procedure (FIG. 10) for adjusting the water outlet temperature Tw2 to the target water outlet temperature Tw2t in the gas compressor in this embodiment. The parameters used in the flowchart of FIG. 12 are the same as those in the flowchart of FIG. 10. Furthermore, the processing of each step in FIG. 12 is the same as that in the first embodiment (FIG. 5).

[0064] (Summary) In this embodiment, the compressor bodies 1L and 1H are self-priming types in which coolant or lubricating fluid is not injected into the internal working chamber, and the high-temperature fluid flowing into the heat exchangers 11L and 11H for exhaust heat recovery contains the compressed gas discharged from the compressor bodies 1L and 1H.

[0065] According to this embodiment configured as described above, in a self-priming type gas compressor, it is possible to adjust the temperature of the heat recovery liquid discharged from the heat exchangers 11L and 11H for exhaust heat recovery to a desired temperature at low cost without providing a temperature control valve or the like in the path of the heat recovery liquid.

[0066] Further, the compressor bodies 1L and 1H in this embodiment include a low-pressure stage compressor body 1L and a high-pressure stage compressor body 1H. The heat exchangers 11L and 11H for exhaust heat recovery include a low-pressure stage exhaust heat recovery heat exchanger 11L that exchanges heat using the compressed gas discharged from the low-pressure stage compressor body 1L as the high-temperature fluid and the heat recovery liquid as the low-temperature fluid, and a high-pressure stage exhaust heat recovery heat exchanger 11H that exchanges heat using the compressed gas discharged from the high-pressure stage compressor body 1H as the high-temperature fluid and the heat recovery liquid as the low-temperature fluid. The low-temperature fluid flow paths of the low-pressure stage exhaust heat recovery heat exchanger 11L and the high-pressure stage exhaust heat recovery heat exchanger 11H are connected in series. Thereby, since the heat recovery liquid is heated by the compressed gas discharged from the low-pressure stage compressor body 1L and the high-pressure stage exhaust heat recovery heat exchanger 11H, it is possible to increase the temperature of the heat recovery liquid.

Embodiment

[0067] FIG. 13 is a schematic diagram showing a schematic configuration of a gas compressor according to a sixth embodiment of the present invention. Hereinafter, the description will focus on the differences from the fifth embodiment.

[0068] In the fifth embodiment (FIG. 9), the low-temperature fluid flow paths of the low-pressure stage exhaust heat recovery heat exchanger 11L and the high-pressure stage exhaust heat recovery heat exchanger 11H are connected in series, whereas in this embodiment, the low-temperature fluid flow paths of the low-pressure stage exhaust heat recovery heat exchanger 11L and the high-pressure stage exhaust heat recovery heat exchanger 11H are connected in parallel.

[0069] The water supply line 31a for introducing water from the water supply source branches into the water supply line 31b midway. The water supply line 31a is connected to the low-pressure stage waste heat recovery heat exchanger 11L, while the water supply line 31b is connected to the high-pressure stage waste heat recovery heat exchanger 11H. The water heated by the low-pressure stage waste heat recovery heat exchanger 11L flows out into the water supply line 32a, and the water heated by the high-pressure stage waste heat recovery heat exchanger 11H flows out into the water supply line 32b. The water supply line 32b merges into the water supply line 32a and is supplied to the hot water demand destination. The water inlet temperature is detected by a water inlet temperature sensor 33 installed upstream of the branch point between the water supply line 31a and the water supply line 31b, and the water outlet temperature is detected by a water outlet temperature sensor 34 installed downstream of the confluence point between the water supply line 32a and the water supply line 32b.

[0070] According to this configuration, by connecting the low-temperature fluid flow paths of the low-pressure stage waste heat recovery heat exchanger 11L and the high-pressure stage waste heat recovery heat exchanger 11H in parallel, compared with connecting the low-temperature fluid flow paths of the low-pressure stage waste heat recovery heat exchanger 11L and the high-pressure stage waste heat recovery heat exchanger 11H in series as in the fifth embodiment (FIG. 9), the difference between the water inlet temperature Tw1 on the low-temperature side and the low-pressure stage discharge air temperature TdL1 or the high-pressure stage discharge air temperature TdH1 on the high-temperature side can be ensured to be larger. Therefore, a larger amount of heat can be exchanged, and the energy-saving effect is increased. On the other hand, the high-pressure stage water outlet temperature TwH2 is lower than that when the low-temperature fluid flow paths of the low-pressure stage waste heat recovery heat exchanger 11L and the high-pressure stage waste heat recovery heat exchanger 11H are connected in series as in the fifth embodiment.

[0071] Also, the group of heat exchangers connected in parallel can be regarded as a large single heat exchanger, and the characteristic curve in this case corresponds to curve 1 in FIG. 4.

[0072] (Summary) In this embodiment, the compressor bodies 1L and 1H include a low-pressure stage compressor body 1L and a high-pressure stage compressor body 1H. The exhaust heat recovery heat exchangers 11L and 11H include a low-pressure stage exhaust heat recovery heat exchanger 11L that exchanges heat with the compressed gas discharged from the low-pressure stage compressor body 1L as a high-temperature fluid and the heat recovery liquid as a low-temperature fluid, and a high-pressure stage exhaust heat recovery heat exchanger 11H that exchanges heat with the compressed gas discharged from the high-pressure stage compressor body 1H as a high-temperature fluid and the heat recovery liquid as a low-temperature fluid. Each low-temperature fluid flow path of the low-pressure stage exhaust heat recovery heat exchanger 11L and the high-pressure stage exhaust heat recovery heat exchanger 11H is connected in parallel.

[0073] According to this embodiment configured as described above, by connecting each low-temperature fluid flow path of the low-pressure stage exhaust heat recovery heat exchanger 11L and the high-pressure stage exhaust heat recovery heat exchanger 11H in parallel, a large difference is ensured between the water inlet temperature Tw1 on the low-temperature side and the low-pressure stage discharge air temperature TdL1 or the high-pressure stage discharge air temperature TdH1 on the high-temperature side, and the amount of exchanged heat increases. Therefore, the energy-saving effect can be improved.

Embodiment

[0074] FIG. 14 is a schematic diagram showing a schematic configuration of a gas compressor according to a seventh embodiment of the present invention. Hereinafter, the description will focus on the differences from the fifth embodiment.

[0075] In addition to the configuration of the fifth embodiment (FIG. 9), the gas compressor in this embodiment further includes a lubricating oil exhaust heat recovery heat exchanger 11o for recovering exhaust heat from the lubricating oil. Specifically, one of the two outlets on the outlet side of the temperature control valve 16 is connected to an oil path 17a at the outlet on the side passing through the oil cooler 20, and the oil path 17a is connected to the inlet of the high-temperature fluid flow path of the lubricating oil exhaust heat recovery heat exchanger 11o. An oil path 17b is connected to the outlet of the high-temperature fluid flow path of the lubricating oil exhaust heat recovery heat exchanger 11o and communicates with the oil cooler 20. The configuration downstream therefrom is the same as that of the fifth embodiment.

[0076] The order of water flow into the low-temperature fluid flow path side of the heat exchanger for waste heat recovery is as follows: First, the water supply path 31a that introduces water from the water supply source with the lowest water temperature is connected to the low-temperature fluid flow path inlet of the lubricating oil waste heat recovery heat exchanger 11o, and the water is first heated by the heat of the lubricating oil. The reason for passing through the lubricating oil waste heat recovery heat exchanger 11o first is to ensure a temperature difference between the lubricating oil and water, since for an oil-free compressor, the lubricating oil temperature is significantly lower than the discharge air temperature in the low-pressure stage or high-pressure stage. After passing through the lubricating oil waste heat recovery heat exchanger 11o, the water flows into the low-pressure stage waste heat recovery heat exchanger 11L via the water supply path 31b, as in the fifth embodiment. After being heated by the heat of the low-pressure stage discharge air here, it flows into the high-pressure stage waste heat recovery heat exchanger 11H via the water supply path 31c, where it is further heated by the higher-temperature high-pressure stage discharge air and then supplied to the hot water demand destination.

[0077] Also, in this embodiment, since the low-temperature fluid flow paths of the three waste heat recovery heat exchangers 11o, 11L, and 11H are connected in series, the characteristic curve corresponds to curve 2 in FIG. 4. However, due to the waste heat recovery from the lubricating oil, the target high-pressure stage discharge air temperature TdH1t and the target water outlet temperature TwH2t can be increased, so in reality, it becomes a curve that has moved slightly to the upper right of curve 2 in FIG. 4.

[0078] (Summary) The gas compressor in this embodiment includes a lubricating oil waste heat recovery heat exchanger 11o that exchanges heat with the lubricating liquid discharged from the compressor main bodies 1L and 1H, using the lubricating liquid as the high-temperature fluid and the heat recovery liquid as the low-temperature fluid. The low-temperature fluid flow path of the lubricating oil waste heat recovery heat exchanger 11o is located upstream of the low-temperature fluid flow paths of the low-pressure stage waste heat recovery heat exchanger 11L and the high-pressure stage waste heat recovery heat exchanger 11H.

[0079] According to this embodiment configured as above, since waste heat recovery is also possible from the lubricating liquid, in addition to an increase in the heat exchange amount and an enhancement of the energy-saving effect, after preheating the heat recovery liquid with the lubricating liquid, it can be heated by the low-pressure stage discharge air and the high-pressure stage discharge air respectively, so it is possible to supply a heat recovery liquid at a higher temperature than in the fifth embodiment.

Embodiment

[0080] FIG. 15 is a schematic diagram showing a schematic configuration of a gas compressor according to an eighth embodiment of the present invention. Hereinafter, the description will focus on the differences from the fifth embodiment.

[0081] The gas compressor in the present embodiment separately includes a fan duct 46 for an intercooler and a fan duct 47 for an aftercooler, and cooling fans 30a and 30b are respectively provided in the fan ducts 46 and 47.

[0082] The intercooler 13a and the oil cooler 20a are installed inside the fan duct 46 containing the cooling fan 30a or in a form connected to an opening thereof, and these coolers cool the internal fluid by the cooling air generated by the cooling fan 30a.

[0083] On the other hand, the pre-cooler 13b, the aftercooler 13c, and the oil cooler 20b are installed inside the fan duct 47 containing the cooling fan 30b or in a form connected to an opening thereof, and these coolers cool the internal fluid by the cooling air generated by the cooling fan 30a.

[0084] The oil cooler 20a is provided at the tip of an oil path 17a downstream of a temperature control valve 16 connected to an oil path 15c branched from the oil path 15b. The lubricating oil cooled by the oil cooler 20a passes through the oil path 21a, merges with the oil path 21b, and is filtered by the oil filter 22.

[0085] The oil cooler 20b is provided at the tip of an oil path 17b downstream of the temperature control valve 16 connected to the tip of the oil path 15b. The lubricating oil cooled by the oil cooler 20b passes through the oil path 21b, merges with the oil path 21a, and is filtered by the oil filter 22.

[0086] The cooling fan 30a and the cooling fan 30b are respectively driven and rotationally controlled by an inverter 36a for the cooling fan and an inverter 36b for the cooling fan, and the main control board 37 issues operation commands and control commands to the inverter 36a for the cooling fan and the inverter 36b for the cooling fan.

[0087] (Summary) The compressor bodies 1L and 1H in this embodiment include a low-pressure stage compressor body 1L and a high-pressure stage compressor body 1H. The air-cooled coolers 13a and 13c include an intercooler 13a for cooling the compressed gas discharged from the low-pressure stage compressor body 1L and an aftercooler 13c for cooling the compressed gas discharged from the high-pressure stage compressor body 1H. The cooling fans 30a and 30b include a first cooling fan 30a for blowing air to the intercooler 13a and a second cooling fan 30b for blowing air to the aftercooler 13b. The gas compressor includes a first fan duct 46 that encloses the first cooling fan 30a and the intercooler 13a, or in which the ventilation part of the intercooler 13a is connected to the opening, and a second fan duct 47 that encloses the second cooling fan 30b and the aftercooler 13c, or in which the ventilation part of the aftercooler 13c is connected to the opening.

[0088] According to this embodiment configured as described above, when the hot water priority mode is valid, the second cooling fan 30b remains at full speed operation, and only the first cooling fan 30a is decelerated and rotation speed controlled. By reducing the cooling capacity of the intercooler 13a and increasing the high-pressure stage suction air temperature, the high-pressure stage discharge air temperature TdH1 can be increased, and as a result, the water outlet temperature TwH2 can be increased. At this time, since the second cooling fan 30b is at full speed operation, the cooling capacity of the aftercooler 13b can be maximally exerted, compressed air that is sufficiently cooled can be supplied to the compressed air demand destination, and the load on the compressed air dehumidifying device that can be installed downstream of the compressor can be reduced.

[0089] Also, by sharing the cooling of the lubricating oil between the two oil coolers 20a and 20b, even when the first cooling fan 30a is operating at a reduced speed, the second cooling fan 30b that can operate at full speed can continue to cool the lubricating oil in the oil cooler 20b, so the rise in the lubricating oil temperature is limited to a certain extent. Thereby, it becomes possible to improve the reliability of operation in an environment where the ambient atmosphere is at a high temperature.

[0090] Although the embodiments have been described above, the present invention is not limited to the above-described embodiments and includes various modifications. For example, although an example in which the present invention is applied to a screw compressor has been described, it is not limited to this, and it can be similarly applied to a scroll compressor, a turbo compressor, a roots blower, etc. Further, in the above-described embodiment, an example of a screw compressor having a pair of male and female screw rotors in the rotor chamber has been described, but the present invention can be similarly applied to a single screw compressor having one screw rotor. Further, in the above embodiment, an example in which water is used as the low-temperature fluid of the waste heat recovery heat exchanger 11, the low-pressure stage waste heat recovery heat exchanger 11L, and the high-pressure stage waste heat recovery heat exchanger 11H has been shown, but other coolant liquids containing antifreeze components such as alcohols, solutions, and even cases where oil is used can also be assumed, and it is not limited to only water as the low-temperature fluid. Further, although the structure of the drive system directly connects and drives the compressor main body 1 with one main motor 2, the main motor 2 and the compressor main body 1 may be driven by a speed increasing gear, or may be driven by a coupling or a belt. Further, it can also be applied to a multi-stage compressor having a plurality of compressor main bodies and compressing the compressed gas in several stages. Further, the low-pressure stage compressor main body and the high-pressure stage compressor main body may be driven by separate motors. Further, a plurality of cooling fans and inverters for the cooling fans may be provided respectively. For example, out of two cooling fans, one may be an inverter for the cooling fan, and the other cooling fan may be driven at a constant speed according to the power supply frequency.

[0091] In addition, in the second embodiment, a plate type heat exchanger in which the three systems of compressed air, lubricating oil, and water of the waste heat recovery heat exchanger are provided in one heat exchanger has been assumed, but heat exchange may be performed separately in two types of heat exchangers between compressed air - water and lubricating oil - water. Further, in all embodiments, the heat exchanger may be a shell and tube type heat exchanger. The connection methods on the high-temperature fluid side and the low-temperature fluid side are not in the order shown in each embodiment, and the connection order may be changed respectively. For example, in each waste heat recovery heat exchanger, the high-temperature fluid and the low-temperature fluid are connected so as to be in a countercurrent flow, but this may be changed to a parallel flow.

[0092] In addition, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. For example, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Also, with respect to a part of the configuration of each embodiment, addition, deletion, or replacement with other configurations is possible.

Description of Reference Numerals

[0093] 1…Compressor body, 1L…Low-pressure stage compressor body, 1H…High-pressure stage compressor body, 2…Main motor, 3…Suction filter, 4…Suction valve, 5…Suction air passage, 6, 6a, 6b, 6c, 10, 10a, 12, 14…Discharge air passage, 7…Oil primary separator, 7a…Condensed water separator, 8…Oil secondary separator, 9…Pressure regulating check valve, 9a…Check valve, 10, 10a…Discharge air passage, 11, 11A…Heat exchanger for exhaust heat recovery, 11L…Low-pressure stage heat exchanger for exhaust heat recovery, 11H…High-pressure stage heat exchanger for exhaust heat recovery, 11o…Heat exchanger for lubricating oil exhaust heat recovery (heat exchanger for lubricating fluid exhaust heat recovery), 13a…Intercooler (air-cooled cooler), 13b…Precooler (air-cooled cooler), 13c…Aftercooler (air-cooled cooler), 15, 15a, 15b, 15c, 17, 17a, 17b, 19, 21, 21a, 21b, 23, 23a…Oil passage, 16…Temperature control valve, 18, 18a, 18b…Oil bypass path, 20, 20a, 20b…Oil cooler (air-cooled cooler), 22…Oil filter, 24…Suction pressure sensor, 25…Discharge air temperature sensor (discharge gas temperature sensor), 25a…Low-pressure stage discharge air temperature sensor, 25b…High-pressure stage suction air temperature sensor, 25c…High-pressure stage discharge air temperature sensor, 26…Discharge air pressure sensor, 26a…High-pressure stage suction air pressure sensor, 27…Lubricating oil inlet temperature sensor, 28…Unit outlet discharge air pressure sensor, 29…Oil supply pressure sensor, 30…Cooling fan, 30a…Cooling fan (first cooling fan), 30b…Cooling fan (second cooling fan), 31, 31a, 31b, 31c, 32…Water supply path, 33…Water inlet temperature sensor, 34…Water outlet temperature sensor (heat exchange fluid temperature sensor), 35…Inverter for main motor, 36, 36a,36b… Inverter for cooling fan, 37… Main control board (controller), 38… Input and display device (switching instruction device), 39… Gear case, 45… Oil pump, 46… Fan duct (first fan duct), 47… Fan duct (second fan duct), 48… Oil separator outlet air temperature sensor, Td1… Discharge air temperature, TdL1… Low-pressure stage discharge air temperature (low-pressure stage high-temperature fluid inlet temperature), TdH1… High-pressure stage discharge air temperature (high-pressure stage high-temperature fluid inlet temperature), Td1t… Target discharge air temperature, TdH1t… Target high-pressure stage discharge air temperature, Td1f… Fan control start discharge air temperature, TdH1f… Fan control start high-pressure stage discharge air temperature, Td1A… Discharge air alarm temperature, TdH1A… High-pressure stage discharge air alarm temperature, Td1r… Discharge air upper limit temperature in hot water priority mode, TdH1r… Discharge air upper limit temperature in hot water priority mode, Tdsp… Oil separator outlet air temperature, Tw1… Water inlet temperature, TwL1… Low-pressure stage water inlet temperature, Tw2… Water outlet temperature (heat exchange fluid temperature), TwH2… High-pressure stage water outlet temperature, Tw2t… Target water outlet temperature (target heat exchange fluid temperature), TwH2t… Target high-pressure stage water outlet temperature, ΔTm: Logarithmic mean temperature difference, ΔTmL… Low-pressure stage logarithmic mean temperature difference, ΔTmH… High-pressure stage logarithmic mean temperature difference, Ps… Suction pressure, Pd… Unit outlet discharge air pressure, PsH… High-pressure stage suction air pressure, Po… Oil supply pressure, Ff… Cooling fan inverter output frequency, Ffmax… Cooling fan inverter maximum output frequency.,

Claims

1. A compressor body that sucks in, compresses, and discharges gas, A waste heat recovery heat exchanger that exchanges heat between at least a part of the high-temperature fluid discharged from the compressor body and a heat exchange fluid as a low-temperature fluid, An air-cooled cooler that cools the high-temperature fluid, A cooling fan that blows air to the air-cooled cooler, A controller that controls the rotational speed of the cooling fan, A discharge gas temperature sensor that detects the discharge gas temperature, which is the temperature of the compressed gas discharged from the compressor body, A heat exchange fluid temperature sensor that detects the heat exchange fluid temperature, which is the temperature of the heat exchange fluid discharged from the waste heat recovery heat exchanger, A path for allowing at least a part of the high-temperature fluid cooled by the air-cooled cooler to flow into the compressor body, and is provided with, The controller, Stores the correlation between the heat exchange fluid temperature and the discharge gas temperature, sets the discharge gas temperature corresponding to a predetermined target heat exchange fluid temperature in the correlation as the target discharge gas temperature, and controls the rotational speed of the cooling fan so that the discharge gas temperature approaches the target discharge gas temperature A gas compressor characterized by that.

2. A compressor body that sucks in, compresses, and discharges gas, A waste heat recovery heat exchanger that exchanges heat between at least a part of the high-temperature fluid discharged from the compressor body and a heat exchange fluid as a low-temperature fluid, An air-cooled cooler that cools the high-temperature fluid, A cooling fan that blows air to the air-cooled cooler, A controller that controls the rotational speed of the cooling fan, A discharge gas temperature sensor that detects the discharge gas temperature, which is the temperature of the compressed gas discharged from the compressor body, A heat exchange fluid temperature sensor that detects the heat exchange fluid temperature, which is the temperature of the heat exchange fluid discharged from the waste heat recovery heat exchanger, A path for allowing at least a part of the high-temperature fluid cooled by the air-cooled cooler to flow into the compressor body, A switching instruction device that instructs activation or deactivation of the heat recovery liquid temperature adjustment function, and is provided with, The controller, When instructed to activate the heat recovery liquid temperature adjustment function from the switching instruction device, controls the rotational speed of the cooling fan so that the heat exchange fluid temperature approaches a predetermined target heat exchange fluid temperature, When instructed to deactivate the heat recovery liquid temperature adjustment function from the switching instruction device, controls the rotational speed of the cooling fan so that the discharge gas temperature approaches a predetermined target discharge gas temperature A gas compressor characterized by that.

3. In the gas compressor according to claim 1, The compressor body is a liquid supply type in which a lubricating liquid is injected into the internal working chamber, and the high-temperature fluid flowing into the heat exchanger for exhaust heat recovery contains the lubricating liquid discharged from the compressor body. A gas compressor characterized by this.

4. In the gas compressor according to claim 1, the compressor body is a non-liquid supply type in which a coolant or a lubricating liquid is not injected into the internal working chamber, and the high-temperature fluid flowing into the heat exchanger for exhaust heat recovery contains the compressed gas discharged from the compressor body. A gas compressor characterized by this.

5. In the gas compressor according to claim 1, the compressor body is a multi-stage type. A gas compressor characterized by this.

6. In the gas compressor according to claim 5, the compressor body has a low-pressure stage compressor body and a high-pressure stage compressor body, the heat exchanger for exhaust heat recovery has a low-pressure stage exhaust heat recovery heat exchanger that exchanges heat with the compressed gas discharged from the low-pressure stage compressor body as the high-temperature fluid and the heat recovery liquid as the low-temperature fluid, and a high-pressure stage exhaust heat recovery heat exchanger that exchanges heat with the compressed gas discharged from the high-pressure stage compressor body as the high-temperature fluid and the heat recovery liquid as the low-temperature fluid, and the low-temperature fluid flow paths of the low-pressure stage exhaust heat recovery heat exchanger and the high-pressure stage exhaust heat recovery heat exchanger are connected in series. A gas compressor characterized by this.

7. In the gas compressor according to claim 6, it is provided with a lubricating liquid exhaust heat recovery heat exchanger that exchanges heat with the lubricating liquid discharged from the compressor body as the high-temperature fluid and the heat recovery liquid as the low-temperature fluid, and the low-temperature fluid flow path of the lubricating liquid exhaust heat recovery heat exchanger is located upstream of the low-temperature fluid flow paths of the low-pressure stage exhaust heat recovery heat exchanger and the high-pressure stage exhaust heat recovery heat exchanger. A gas compressor characterized by this.

8. In the gas compressor according to claim 5, the compressor body has a low-pressure stage compressor body and a high-pressure stage compressor body, the heat exchanger for exhaust heat recovery has a low-pressure stage exhaust heat recovery heat exchanger that exchanges heat with the compressed gas discharged from the low-pressure stage compressor body as the high-temperature fluid and the heat recovery liquid as the low-temperature fluid, and a high-pressure stage exhaust heat recovery heat exchanger that exchanges heat with the compressed gas discharged from the high-pressure stage compressor body as the high-temperature fluid and the heat recovery liquid as the low-temperature fluid, and the low-temperature fluid flow paths of the low-pressure stage exhaust heat recovery heat exchanger and the high-pressure stage exhaust heat recovery heat exchanger are connected in parallel. A gas compressor characterized by this.

9. In the gas compressor according to claim 5, The compressor body has a low-pressure stage compressor body and a high-pressure stage compressor body. The air-cooled cooler has an intercooler that cools the compressed gas discharged from the low-pressure stage compressor body and an aftercooler that cools the compressed gas discharged from the high-pressure stage compressor body. The cooling fan has a first cooling fan that blows air to the intercooler and a second cooling fan that blows air to the aftercooler. The gas compressor includes a first fan duct that encloses the first cooling fan and the intercooler, or in which the ventilation section of the intercooler is connected to the opening, and a second fan duct that encloses the second cooling fan and the aftercooler, or in which the ventilation section of the aftercooler is connected to the opening. A gas compressor characterized by the above.

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