JP5448419B2 - Vapor compression equipment - Google Patents

Description

  The present invention relates to a vapor compression apparatus.

  In a steam process in which steam is supplied from a boiler, low-pressure steam is discharged from a demand facility. Most of the steam discharged from the demand equipment is close to atmospheric pressure and difficult to secondary use. Although the heat of these low-pressure steam is recovered in boiler make-up water, most of the steam is still released into the atmosphere and a lot of energy is wasted.

  Patent Document 1 describes a technique for regenerating low-pressure steam with a desired pressure that can be used at low cost with less energy than by newly evaporating water with a boiler by compressing the low-pressure steam with a screw compressor. ing.

  In a positive displacement compressor such as a screw compressor, steam is discharged as superheated steam that has risen above the saturated steam temperature by adiabatic compression. Generally, since it is a saturated steam that is required in a demand facility, it is necessary to cool the discharged superheated steam to the saturated steam temperature, and the heat energy is wasted.

In addition, the service temperature of the screw compressor is about 250 ° C., and at most about 300 ° C. The excessive temperature rise of the steam may cause the casing to deform and cause troubles such as galling of the screw rotor. It was.
Japanese Examined Patent Publication No. 6-70540

  In view of the above problems, an object of the present invention is to provide a vapor compression apparatus in which the vapor temperature does not excessively increase without wasting waste of the compressor energy.

In order to solve the above problems, a vapor compression apparatus according to the present invention is a positive displacement compressor which discharges to the discharge flow path by compressing the vapor of the target fluid sucked to the working space from the suction passage, the discharge A compressor connected to a supply pipe for supplying the steam of the target fluid to the steam demand facility, a suction pressure detecting means for detecting a suction pressure of the compressor, and a suction pressure of the compressor is constant A rotation speed control means for controlling the rotation speed of the compressor, a discharge temperature detection means for detecting a discharge temperature of the compressor, and a discharge temperature of the compressor at the discharge pressure of the compressor. Liquid injection means for injecting the liquid of the target fluid only into the working space while adjusting the flow rate so as to be constant at a temperature equal to or higher than the saturated vapor temperature of the target fluid.

According to this configuration, since the liquid injected into the working space of the compressor is vaporized, latent heat of vaporization is consumed, so that the discharge temperature can be adjusted by adjusting the amount of liquid injected. Moreover, the ejected liquid evaporates, so that the discharge amount of steam can be increased. Thereby, the energy output from the compressor can be converted into the steam energy that can be effectively used. In addition, by reducing the suction pressure by controlling the rotation speed of the compressor, the suction pressure of the compressor becomes less than atmospheric pressure, especially when sucking in steam close to atmospheric pressure. This will not damage the shaft seal.

It said speed control means, as the suction pressure before Symbol compressor becomes constant at a more target-atmospheric pressure, Rukoto to control the rotational speed of the compressor is preferred.

  Further, the vapor compression apparatus of the present invention includes a discharge pressure detecting means for detecting a discharge pressure of the compressor, and a rotation speed control for controlling the rotation speed of the compressor so that the discharge pressure of the compressor becomes constant. And a means.

  According to this configuration, the steam compressor itself has the ability to make the discharge pressure constant, so that the steam compressor alone can supply the steam with the desired pressure to the demand facility without joining the steam to the header or the like whose pressure is controlled. Can supply.

  In the vapor compression apparatus of the present invention, the discharge temperature of the compressor may be slightly higher than the saturated vapor temperature at the discharge pressure of the compressor.

  If the discharge pressure is constant, even if the amount of liquid to be injected is increased, the compressor only discharges wet steam at the discharge pressure, and the discharge temperature does not become lower than the saturated steam temperature at the discharge pressure. For this reason, the control margin can be ensured by setting the discharge temperature of the compressor to a temperature slightly higher than the saturated steam temperature at the discharge pressure and performing control in a region where the temperature becomes slightly superheated steam.

According to the present invention, since the liquid is injected into the suction flow path or the working space of the compressor while adjusting the flow rate so that the discharge temperature of the compressor becomes constant, the surplus output of the compressor is It consumes to evaporate and can improve energy efficiency by increasing the amount of steam and prevent troubles caused by overheating of the compressor. In addition, by reducing the suction pressure by controlling the rotation speed of the compressor, the suction pressure of the compressor becomes less than atmospheric pressure, especially when sucking in steam close to atmospheric pressure. This will not damage the shaft seal.

Embodiments and reference examples of the present invention will now be described with reference to the drawings. FIG. 1 shows a configuration of a vapor compression apparatus 1 according to a reference example of the present invention.

The vapor compression apparatus 1 of the present reference example includes a screw compressor 6 that accommodates a pair of male and female screw rotors 5 driven by a motor 4 in a working space 3 of a housing 2. The screw compressor 6 sucks low-pressure steam from the suction flow path (suction pipe) 7 into the working space 3, compresses the pressure by the screw rotor 5, and discharges the high-pressure steam to the discharge flow path (discharge pipe) 8. It is a positive displacement compressor. The suction flow path 7 is supplied with low-pressure steam discharged from a steam demand facility (not shown). Further, the discharge flow path 8 is connected to a supply pipe for supplying saturated steam having a predetermined pressure to a demand facility from a boiler (not shown), whereby the internal pressure is kept constant.

  In addition, the vapor compression apparatus 1 includes a liquid ejecting unit 9 that ejects water into the suction channel 7. The liquid injection means 9 includes a regulating valve 10 for controlling the amount of water by restricting the flow path, and a spray tip 11 for injecting water in a mist form. Furthermore, the vapor compression apparatus 1 has a suction pressure detector 12 for detecting the suction pressure Ps in the suction flow path 7, and a discharge temperature detector 13 for detecting the discharge temperature Td in the discharge flow path 8. .

  The screw compressor 6 compresses the sucked low-pressure steam and the water jetted by the liquid jetting means 9 in the working space 3 to give thermal energy to the steam and water. Water is vaporized by the applied heat energy and becomes steam. At the moment when these vapors are discharged from the working space 3 to the discharge flow path 8, the pressure thereof becomes equal to the pressure of the discharge flow path 8. At this time, if the heat energy given from the screw compressor 6 is large and all the water is evaporated, the steam becomes superheated steam having a temperature higher than the saturated steam temperature at the discharge pressure.

The vapor compression apparatus 1 calculates a deviation between the discharge temperature Td of the screw compressor 6 detected by the discharge temperature detector 13 and a predetermined target temperature, and feeds back the opening degree of the control valve 10 of the liquid injection means 9. . That is, if the discharge temperature Td is higher than the target temperature, the opening degree of the control valve 10 is increased and the amount of water to be injected is increased, so that more heat energy given from the screw compressor 6 is consumed as latent heat of evaporation. As a result, the discharge temperature Td of the screw compressor 6 decreases and the flow rate of the discharged steam increases. On the other hand, if the discharge temperature Td is lower than the target temperature, the opening of the control valve is reduced, the discharge steam amount is reduced, and the heat energy consumed when water vaporizes is reduced, thereby increasing the discharge temperature Td. Let

  Thus, the steam compressor 1 can maximize the steam supply amount by converting all the thermal energy output from the screw compressor 6 into the steam energy at the target temperature. This also prevents the screw compressor 6 from overheating due to an excessive rise in the steam temperature, and the housing 2 to be deformed beyond the limit due to thermal expansion, thereby preventing the screw rotor 5 from rotating.

  Here, the target temperature is a temperature slightly higher than the saturated steam temperature (steam supply temperature from the boiler) in the pressure of the discharge flow path 8 (discharge pressure of the screw compressor 6). This is because the steam does not fall below the saturated steam temperature at that pressure, and partly condenses (liquefies) to release latent heat and maintain the whole at the saturated steam temperature, so that the output energy of the screw compressor 6 is reduced. This is because the shortage cannot be detected. For this reason, the target temperature is determined in consideration of the discharge temperature responsiveness by adjusting the opening degree of the control valve 10, so that the shortage of output energy of the screw compressor 6 is reliably detected, and appropriate opening degree control of the control valve 10 is performed. For example, the temperature may be set higher than the saturation vapor temperature at 5 ° C. and the discharge pressure as much as possible.

  The vapor compression apparatus 1 supplies superheated steam having a slightly high temperature, but the degree of superheat is low, and the amount of drainage due to heat loss of piping to the demand facility is reduced, and does not cause trouble in the demand facility. Therefore, there is no need to provide a cooling device or the like.

Moreover, the vapor compression apparatus 1 of this reference example adjusts the drive frequency of the motor 4 so that the suction pressure Ps of the screw compressor 6 detected by the suction pressure detector 12 is maintained at a predetermined target pressure that is equal to or higher than atmospheric pressure. Then, the rotational speed of the screw compressor 6 is controlled.

  This is because when the pressure of the steam supplied to the suction flow path 7 is close to the atmospheric pressure, the suction force of the screw compressor 6 is superior to the steam supply amount, and the suction flow path 7 and the suction side of the working chamber 3 are at the atmospheric pressure. By lowering, the sealing property of the pipe connection part and the shaft seal of the screw rotor 5 is impaired, the ambient air is sucked in and the quality of the steam is lowered, or the life of the shaft seal of the screw rotor 5 is shortened. This is to prevent problems.

  In addition, the water sprayed by the liquid spraying means 9 needs to use soft water with a small amount of minerals, steam condensate, or the like in order to prevent the occurrence of scale, as in the case of boiler water supply.

Next, FIG. 2 shows a vapor compression apparatus 1a according to one embodiment of the present invention. In the description of the present embodiment, the same components as those in the reference example are denoted by the same reference numerals, and redundant description is omitted.

  In the vapor compression apparatus 1a of the present embodiment, the supply amount (or supply pressure) of low-pressure steam is sufficiently large, and the suction pressure Ps does not become smaller than atmospheric pressure. Moreover, the vapor | steam compressor 1a of this embodiment does not add a vapor | steam to piping from a boiler etc., itself supplies a vapor | steam to a demand facility independently.

  Specifically, the vapor compression apparatus 1a has a discharge pressure detector 14 for detecting the discharge pressure Pd of the screw compressor 6 in the discharge flow path 8, and compresses the screw so that the detected discharge pressure Pd becomes constant. By controlling the rotation speed of the machine 6, the discharge pressure can be maintained at the target pressure alone.

  Moreover, in this embodiment, the liquid injection means 9 injects water not into the suction flow path 7 but into the working space 3 of the screw compressor 6.

  Also in the present embodiment, by increasing the amount of steam by evaporating the water supplied from the liquid ejecting means 9, it is possible to improve energy efficiency and prevent troubles caused by excessive temperature rise.

In the above embodiment and the reference example , the vapor compression apparatuses 1 and 1a that compress the water vapor while increasing the amount have been described. However, the present invention is not limited to the water vapor, and compresses the vapor of other fluid such as natural gas. It can also be applied to devices.

The figure which shows the structure of the vapor compression apparatus of the reference example of this invention. The figure which shows the structure of the vapor compression apparatus of one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a ... Steam compressor 2 ... Housing 3 ... Action chamber 4 ... Motor 5 ... Screw rotor 6 ... Screw compressor (positive displacement compressor)
DESCRIPTION OF SYMBOLS 7 ... Suction flow path 8 ... Discharge flow path 9 ... Liquid supply means 10 ... Control valve 11 ... Spray tip 12 ... Suction pressure detector 13 ... Discharge temperature detector 14 ... Discharge pressure detector

Claims (3)

A positive displacement compressor that compresses the vapor of the target fluid sucked into the working space from the suction flow path and discharges it to the discharge flow path so that the discharge flow path supplies the vapor of the target fluid to the steam demand facility A compressor connected to the supply piping of
A suction pressure detecting means for detecting a suction pressure of the compressor;
A rotational speed control means for controlling the rotational speed of the compressor so that the suction pressure of the compressor becomes constant;
A discharge temperature detecting means for detecting a discharge temperature of the compressor;
Liquid injection for injecting the liquid of the target fluid only into the working space while adjusting the flow rate so that the discharge temperature of the compressor becomes constant at a temperature equal to or higher than the saturated vapor temperature of the target fluid at the discharge pressure of the compressor Means for vapor compression. Said speed control means, the suction pressure before Symbol compressor to be constant in the above target pressure atmospheric pressure of claim 1, wherein the benzalkonium control the rotational speed of the compressor Vapor compression device. The steam compressor according to claim 1 or 2 , wherein the discharge temperature of the compressor is slightly higher than a saturated steam temperature at a discharge pressure of the compressor.

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