JPS6234147Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention is a multistage compressor that heats a heat medium to a high temperature to recover heat energy given to air etc. during the compression process of the multistage compressor. The present invention relates to an exhaust heat recovery device.

[Prior Art] It is well known that when air is compressed by a compressor, the air reaches a high temperature, for example, about 130°C, or as high as nearly 200°C depending on the model. If this high-temperature compressed air cannot be used as it is, the air is cooled and then supplied to the utilization device. Even if the compressor is a multi-stage type, the preceding stage produces high-temperature compressed air as described above, so the high-temperature compressed air is cooled and sent to the next stage, taking into account the thermal design conditions of the next stage. It is configured as follows.

That is, if the intake air temperature of the next-stage compressor increases significantly above the set value, not only will compression efficiency decrease, but a surging phenomenon may occur, and in the worst case, the compressor may be destroyed. Therefore, it is necessary to cool the high-temperature compressed gas to a temperature suitable for the suction port side of the next or subsequent stage compressor.

The means used for such cooling consists of a heat exchanger installed on the discharge side and connected to a cooling tower, and therefore the amount of heat given to the cooling medium by the heat exchanger is All of this is released into the atmosphere without being put to good use.

Considering that the thermal energy given to the compressed air accounts for about 90% or more of the compressor drive energy, the above-mentioned release into the atmosphere is extremely undesirable from the viewpoint of energy conservation.

[Problems to be Solved by the Invention] Taking this into consideration, the applicant has proposed a device for recovering waste heat. The purpose of this waste heat recovery device is to increase the total amount of waste heat that can be recovered, and therefore the temperature of the heat medium that conveys the waste heat is relatively low and not constant. In the case of such low-temperature recovery, there are restrictions on the use of the recovered heat, and the demand for using the recovered waste heat for multiple purposes cannot be met.

Therefore, it is possible to obtain high-temperature refrigerant by reducing the refrigerant flow rate, but in this case, when load fluctuations occur in the system using high-temperature refrigerant, the compressed gas cannot be sufficiently cooled, resulting in continuous stable operation of the compressor. There is a fear that this will not be possible.

[Purpose of the invention] The present invention has been devised to focus on the above-mentioned problems and to effectively solve them.

The purpose of the present invention is to provide an exhaust heat recovery device for a multi-stage compressor that can obtain high-temperature heat medium (hot water) while ensuring cooling performance of compressed gas and stable operation of the multi-stage compressor. be.

[Summary of the invention] In order to achieve the above object, the present invention is a multi-stage system in which at least three or more compressors are connected in multiple stages by connecting the discharge port of the previous stage compressor to the suction port of the subsequent stage compressor. In the compressor, each compressed gas passage connecting the discharge port of the front-stage compressor and the suction port of the rear-stage compressor is equipped with a system for exchanging heat with the compressed gas flowing through these passages and recovering high-temperature sensible heat. A first heat exchanger is provided, and the compressed gas heat-exchanged by the first heat exchanger is supplied from the cooling tower to the downstream side of the first heat exchanger. A second heat exchanger is provided for cooling the compressed gas by exchanging heat with the cooling water, and the first heat exchanger absorbs as much thermal energy as possible in the compressed gas, A high temperature heat medium (sensible heat) is obtained from the heat exchanger, and the heat medium (sensible heat) is transferred to the second heat exchanger provided on the downstream side of the first heat exchanger, after the heat is absorbed by the first heat exchanger. By applying a cooling capacity equivalent to the remaining amount to be absorbed, the compressed gas is cooled to a temperature suitable for the suction side of the compressor in the latter stage, and high-temperature medium is obtained while ensuring continuous and stable operation of the compressor. The summary is what we did.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an exhaust heat recovery device 1 for a three-stage compressor embodying the present invention. C1, C2, and C3 are the first, second, and third stages of a three-stage compressor, respectively. The compressed gas feed paths (hereinafter referred to as connection paths) C12 and C23 that communicate the discharge port at the front stage of each compressor and the suction port of the compressor at the rear stage are used to recover high-temperature sensible heat. first heat exchangers (heat exchangers for heating medium) E1 and E2 are interposed, respectively, and a second heat exchanger (intercooler )E11 and E12 are respectively provided. In addition, a compressed gas passage (hereinafter referred to as a discharge pipe) from the final stage C
30 as well, a first heat exchanger E3 and a second heat exchanger E13 as an aftercooler are interposed when it is necessary to limit the temperature of the discharged compressed gas to below a certain limit. The first heat exchanger is, for example, a heat exchanger for producing hot water, as will become clear from what will be described later. In addition, the second heat exchangers E11 and E1
Reference numeral 2 acts as a cooler that cools the compressed gas passing through these to a temperature suitable for the suction ports of the compressors C2 and C3 located in the subsequent stages.

Here, the temperature suitable for the suction port side refers to a temperature that is below the suction side temperature limit value so that the compressor can operate efficiently without causing surging or the like.

The heat medium supply pipe (the water supply pipe will be explained below) W1 is connected to the inlet of the hot water production heat exchanger E1, and its outlet is connected to the inlet of the heat exchanger E2 via the relay pipe W2. , its outlet is connected to the inlet of the heat exchanger E3 via a relay pipe W3.

The outlet of the heat exchanger E3 is communicated with high temperature water utilization equipment (not shown) via a hot water supply pipe W4 and a high temperature water flow rate control valve V. Also, hot water supply pipe W4
An orifice RO is interposed in the pipe W5 branched from the pipe W5, and the outlet of this orifice is communicated with a water supply tank or a heat recovery tank (not shown).

A temperature measuring element TE is interposed in the hot water supply pipe W4, and a signal converter TT is connected to the output thereof as necessary. The output of the thermometer or signal converter is a temperature controller.
Connected to TIC, its output is high temperature water flow control valve V
connected to the control input of the

The cooling water pump CWP is connected to the inlet of interlarks E11, E12 and an aftercooler E13 provided as necessary via a cooling water supply pipe CW1, and the outlet of each cooler is connected via a cooling water supply pipe CW2. cooling tower
The cooling capacity of the CT is the cooling capacity required in the absence of the first heat exchanger.

The operation of the exhaust heat recovery device 1 of the present invention configured as described above will be explained below.

Water supplied to the hot water production heat exchanger E1 via the water supply pipe W1 is heated by thermal energy given to the air during the compression process in the first stage C1 of the compressor. The air on the discharge side of the heat exchanger E1 passes through the second heat exchanger E11 to the compressor second stage C2.
It is cooled to a temperature suitable for the inlet side.

The water heated in the heat exchanger E1 is transferred to the relay pipe W.
2 to the heat exchanger E2 where it is further heated by hotter compressed air from the second compressor stage C2. Thermal energy given to the hot water in this heat exchange is transferred from the compressed air from the first stage C1 of the compressor to a higher pressure in the second stage C2 of the compressor. It is thermal energy. The higher-pressure compressed air that has been converted into heat energy and hot water is cooled again in the second heat exchanger E12 and then transferred to the third stage of the compressor C3.
The temperature is lowered to a temperature suitable for the inlet side of the compressor, and the air is supplied from the outlet of the heat exchanger E12 to the third stage C3 of the compressor via the compressed gas passage C23.

The hot water whose temperature has been raised in the heat exchanger E2 is supplied to the heat exchanger E3 through the relay pipe W3, where it is raised to the high temperature maximum pressure from the third stage C3 of the compressor, that is, the required discharge pressure of the three-stage compressor. The temperature is further increased by compressed air. The heat source in this heat exchange is the same as the heat source generated in the first stage C1 and second stage C2 of the compressor. The compressed air at the required discharge pressure, which has undergone heat exchange and whose temperature has been lowered to the required temperature, is supplied to a compressed air utilization device (not shown) via the discharge pipe C30.

The high-temperature water from the heat exchanger E3, e.g. 80°C, has means for keeping its temperature at a predetermined value, e.g. 80°C or higher, namely a thermometer TE, a signal converter TT, a temperature indicator controller TIC,
Under the control of the high temperature water flow rate control valve V, the hot water supply pipe W
4, the water is supplied to the high temperature water utilization device.

The temperature of the high temperature water supplied via the hot water supply pipe W4 is maintained at a set temperature in the following manner. That is, the temperature of the high temperature water flowing through the hot water supply pipe W4 is determined by the temperature measuring element TE.
The output is measured directly or, if necessary, is converted to the input signal level required by the temperature indication control system by a signal converter TT and then sent to the temperature indication controller.
Given to TIC. The temperature value is compared with a preset value and calculated by the temperature indicating controller TIC, and the valve opening degree of the high temperature water flow rate control valve V is adjusted by the output from the temperature indicating controller TIC. Through this adjustment, the supply water temperature will be set to a predetermined value (temperature indicator controller).
TIC setting value) or higher.

In parallel with such adjustment, the minimum required flow rate of hot water is constantly flowed from the orifice RO to the water supply tank or the like. This minimum required flow rate is a flow rate that can prevent the hot water temperature from rising abnormally and evaporating in the heat exchanger when the amount of high-temperature water used decreases. This orifice can eliminate the adverse effect on the heat exchanger due to steam generated when the amount of high-temperature water used is reduced.

In addition, the amount of high-temperature water used is eliminated, and orifice RO
The flow rate flowing only from the first heat exchanger E1, E
2 and E3, the heat exchange capacity of the first heat exchangers E1, E2, and E3 decreases,
Therefore, the outlet air temperature of the first heat exchangers E1, E2 and E3 rises above the temperature limit value suitable for the suction side of the respective downstream compressors. In such a case, the second heat exchanger E11, E1
The heat exchange capacity, that is, the cooling capacity of the second heat exchangers E11, E12, and E13 is increased to keep the outlet air temperature of the second heat exchangers E11, E12, and E13 below the limit value, and the temperature is suitable for the suction side of the compressor.

After that, when the amount of high-temperature water usage increases again,
The amount of heat exchanged in the first heat exchangers E1, E2 and E3 increases. Therefore, the second heat exchanger E11,E
In order to bring the outlet air temperatures at E12 and E13 below the limit value, the amount of heat exchanged in these heat exchangers may be reduced. In this way, the outlet air temperature of the second heat exchanger is always kept below the limit value, that is, at a temperature suitable for the suction side of the compressor. In this way, in the compressed gas passage of the multistage compressor, two
By installing a heat exchanger in the system, the main objective is to maintain the cooling performance of the compressed gas and ensure stable operation of the compressor, while also obtaining high-temperature hot water, that is, high-temperature sensible heat that could not be obtained conventionally. Can be done.

That is, such operation of the exhaust heat recovery device does not have any influence on the operating conditions of the compressor. Since it is possible to attach the first heat exchanger with almost no effect on the compressor performance, the usefulness of the present device can be greatly enhanced by installing it in an existing compressor.

In the above embodiment, the second heat exchangers (intercoolers) E11 and E12 and the aftercooler E
The cooled water heated by heat exchange in step 13 is sent to the cooling tower CT and cooled, but before this warmed cooling water is sent to the cooling tower CT, heat is recovered from the cooling water as follows. Doing so will reduce the load on the cooling tower and reduce its power costs.

If the temperature of the water supplied to the first heat exchangers E1, E2, and E3 is lower than the cooling water temperature at the outlet of the intercooler and aftercooler by a certain value, for example, several tens of degrees, As shown in Figure 2, the warmed cooling water from the intercooler and aftercooler passes through the cooling water supply pipe CW2 to the heat exchanger E.
Water is supplied to the heat exchanger E1 through the water supply pipe W1.
This warms the water at a lower temperature than the cooling water flowing through the cooling water. This warmed water is sent to the first heat exchanger E1 via the water supply pipe W1. In this way, heat recovery is also performed in the heat exchanger E10.

In the above embodiment, the first heat exchangers are connected in series, but they may be connected in parallel-series or in parallel, as shown in FIGS. 3A and 3B. In these cases, if you want to obtain water at the same temperature as in the series type shown in Figure 1, the flow rate of water passed through each heat exchanger in the parallel section will be the same as in the series type shown in Figure 1. It is necessary to reduce the amount compared to the case of .

In the above embodiment, the first heat exchanger and the second heat exchanger are of separate and independent type, but a heat exchanger in which two sets of finch tubes are housed in the same shell and formed integrally is also used. good.

Next, an embodiment will be described in which exhaust heat is recovered using an integrated type heat converter having a structure as shown in FIG.

In FIG. 4, E2 is a two-cooling water system heat exchanger. 10 is an outer shell of the heat exchanger E2, and a high temperature fluid passage S is formed in the outer shell 10. Si
indicates its entrance, and So indicates its exit.

The high-temperature fluid passage S is, for example, a passage through which high-temperature air (gas) from a compressor flows. A first endothermic heat medium passage W21 is formed upstream of this high temperature air passage, and a second endothermic heat medium passage W22 is formed downstream of this first heat medium passage W21.
These first and second heat medium passages W21 and W2
The partition wall for 2 is 11.

The left side of the partition wall 11, that is, the upstream side is the primary cooler E2.
1, and the right side, that is, the downstream side is the secondary cooler E22.
It is.

The first heat medium passage (the cooling water passage will be described below) E21 is connected from the cooling water inlet 21i to the inflow water chamber E211 of the primary cooler, and then to the water pipe WP.
From the outflow water chamber W212 through the cooling water outlet W21
It is formed into o.

The second heat medium passage (the cooling water passage will be explained below) W22 is from the cooling water inlet W22i to the inflow water chamber W221 of the secondary cooler, and then to the water pipe.
Cooling water outlet 2 from outflow water chamber W222 via WP'
It is formed into 2o.

Further, in order to form a water return chamber between the inflow water chamber and the outflow water chamber of each cooler, a horizontal partition wall P is provided at the center of the heat exchanger E2.

The number of cooling water passes for both the primary cooler E21 is configured to be four passes or more as shown in the figure. This is to compensate for the decrease in the heat transfer coefficient of the water pipe WP wall due to the decrease in the cooling water flow rate and to prevent the accumulation of foreign matter within the water pipe.

The heat transfer area of the primary cooler is the first cooling water passage W
Depending on the velocity of the water flowing through the heat exchanger E2
The size is determined such that a predetermined proportion, for example, about half, of the total heat energy that is heat exchanged in the primary cooler is heat exchanged in the primary cooler. This corresponds to approximately 30% of the heat transfer area of a conventional single cooling water system heat exchanger with the same cooling capacity.

Further, the heat transfer area of the secondary cooler is set to a predetermined ratio, for example 80%, of the heat transfer area of a conventional single cooling water system type heat exchanger having the same cooling capacity. Here, the same cooling capacity means the same inlet temperature and the same flow rate of high-temperature air (gas).
This means that the outlet temperature will be cooled to the same temperature when it passes through.

A case will be described in which the two-cooling water system heat exchanger E2 integrally formed as described above is used, for example, for heat exchange of thermal energy possessed by high-temperature compressed air compressed by a compressor.

Let the cooling water inlet temperature of a conventionally known cooling water system type heat exchanger be TW1, and the outlet temperature TW2,
If the inlet air temperature is Ta1 and the outlet air temperature is Ta2, the logarithmic average temperature difference Δt in this heat exchanger is It is expressed as

The relationship in Equation 1 above also applies to the primary cooler in the dual cooling water system heat exchanger shown in FIG. The cooling water inlet temperature of the primary cooler is Tw1′,
If the outlet temperature is Tw2′, the inlet air temperature to the primary cooler is Ta1′, and the outlet temperature is Ta2′, then the logarithmic average temperature difference Δt′ at the primary cooler is It is expressed as

In equations (1) and (2), since Ta2'>Ta2, Δt'>Δt. The heat transfer area of the primary cooler is made as large as described above, and a relatively small amount of water is required to be supplied to the primary cooler, for example, in a single cooling water system heat exchanger having the same cooling capacity as described above. If approximately 8% of the cooling water volume is used, hot water at a temperature that is highly utilized, for example 80°C, will be used in the primary cooler E21.
obtained from.

In addition, the air (gas) cooled by the primary cooler that increases such high-temperature hot water is transferred to the secondary cooler E22.
The air having the same outlet air temperature as this outlet air temperature is transferred to the one-cooling water system heat exchanger having the same cooling capacity as described above to the two-cooling water system heat exchanger E2 in FIG. In order to obtain the cooling water flow rate from the outlet of the secondary cooler having a thermal area, the flow rate of cooling water to be passed to the secondary cooler E22 is required by a primary cooling water system type heat exchanger having the same cooling capacity as described above. Approximately 50% of the cooling water flow rate was sufficient.

Therefore, high temperature hot water is obtained from the heat exchanger E2,
However, in order to maintain the outlet temperature at the same level as a conventional equivalent heat exchanger, only about 60% of the cooling water flow rate required by this conventional heat exchanger is required.

The present invention can also be applied to waste heat recovery from compressor oil coolers, electric motors, etc., and brine, fluorocarbon, etc. may be used as the heat medium.

[Effects of the invention] In summary, according to the present invention, the following excellent effects can be achieved.

(1) In the compressed gas passage of the multi-stage compressor, the first and second
The first heat exchanger recovers high-temperature sensible heat, and the second heat exchanger cools the compressed air to a temperature suitable for the suction side of the compressor located in the subsequent stage. As a result, while ensuring the cooling performance of the compressed gas and ensuring stable operation of the compressor, it is possible to obtain high-temperature hot water, that is, high-temperature sensible heat that could not be obtained conventionally. It is possible to prevent changes in the usage amount from affecting the operating conditions of the compressor and the like.

(2) As mentioned above, hot water at a relatively high temperature, for example, 80°C, can be obtained as a water system completely independent of cooling water, so hot water can be used for multiple purposes.

For example, it can be used as a heat source for cleaning processed products in factories, for heating, in kitchens, etc.

(3) The installation of means for producing high-temperature water has little effect on compressor performance.

(4) As long as the effect of (3) can be obtained, it can also be installed on an existing compressor.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the exhaust heat recovery device of the present invention in a three-stage compressor, Fig. 2 is a diagram showing means for recovering heat from cooling water, and Figs. 3A and B are respectively,
FIG. 4 is a diagram showing another connection type of the first heat exchanger, and FIG. 4 is a diagram showing the structure of the heat exchanger formed in an integral structure. In the figure, C1, C2, and C3 are the first
stage, second stage and third stage, E1, E2, E3 are the first
heat exchanger, E11, E12, E13 second heat exchanger, TE is temperature measuring element, TIC is temperature indicating controller,
V is the high temperature water control valve, RO is the orifice, and CT is the cooling tower.

Claims (1)

[Scope of utility model registration request] In a multistage compressor in which at least three or more compressors are connected in multiple stages by connecting the discharge port of the first stage compressor to the suction port of the second stage compressor, the discharge port of the first stage compressor and the second stage compressor A first heat exchanger for recovering high-temperature sensible heat by exchanging heat with the compressed gas flowing through these passages is provided in each compressed gas passage connecting the suction port of the first heat exchanger. On the downstream side of the exchanger, a second heat exchanger is connected to a cooling tower to cool the compressed gas heat-exchanged by the first heat exchanger by exchanging heat with cooling water supplied from the cooling tower. An exhaust heat recovery device for a multi-stage compressor, characterized in that each stage is equipped with a heat exchanger.