JPH11344231A - Waste heat energy converting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a heat utilization factor of a waste heat fluid by using a non-azeotropic fluid having a lower boiling point than that of a water as a medium for generating the vapor by heat exchanging with the fluid in the case of generating a vapor by a vapor generator using a waste heat as a heat source and heat exchanging its thermal energy to be used. SOLUTION: In the case of using, for example, an aqueous ammonia solution having a concentration of 45% as a medium (non-azeotropic fluid) for generating a vapor by heat exchanging with a waste heat fluid, the ammonia solution starts evaporating at about 50 deg.C and becomes a vapor phase area at about 135 deg.C. Then, a vapor generator 1 such as a boiler or the like is installed in a vapor generating area, the waste heat fluid from a thermal power plant or the like is supplied via a piping (a), heat exchanged with the ammonia solution flowing in a heat transfer tube to evaporate the solution. The generated vapor is supplied to a plurality of heat exchangers 2 such as air handling units or the like via a piping (g). A drain after its condensation is circulated to the generator 1 via a drain recovery unit 3 and a pump 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste heat energy conversion system that generates steam using a waste heat fluid such as hot water or hot water in a power plant as a heat source and uses the heat energy.

[0002]

2. Description of the Related Art In recent years, systems for utilizing waste heat energy generated in facilities such as subways, general industries or thermal power plants as an energy source for cooling, heating and greenhouse cultivation have been actively developed. Such waste heat utilization systems can effectively use waste heat energy that has been wasted previously, and also contribute to energy saving and suppression of carbon dioxide gas generation. It is also considered important for global warming countermeasures. As a conventional waste heat energy conversion system, waste heat fluid such as hot water or hot water is supplied to a steam generator such as a boiler or a steam converter, where the water is heated to generate steam, which is sent to the steam utilization area. What transfers and heat-exchanges is known. This system has the advantages of being able to convert the thermal energy of the waste heat fluid into high-value steam energy, and that relatively long-distance transfer can be performed relatively easily because power for transferring steam is generally not required.

[0003] However, when steam is generated using water as the medium to be heated, the pressure and pressure are determined uniquely.
Since boiling and evaporation progress at a temperature, in order to generate a large amount of steam, the steam outlet temperature must be kept considerably lower than the inlet side temperature of the waste heat fluid as a heating medium.
Also, when trying to keep the steam temperature high, when the thermal energy is supplied by the sensible heat of the waste heat fluid due to the large latent heat of evaporation of water, most of the thermal energy is supplied to this latent heat, so the water temperature reaches the boiling temperature. The heat energy which raises is small.

FIG. 5 is a diagram showing the temperature change of the waste heat fluid on the heating side and the temperature of the water on the heated side using the distance of the heat transfer tube in the steam generator as a parameter. The heat fluid (e) is subjected to heat exchange with water (f) and drops in temperature and flows out at a temperature of 139 ° C. On the other hand, water (f) is supplied to a steam generator at, for example, 35 ° C.
It starts to boil at a temperature of about 0 ° C., and is further heated before flowing out of the steam generating device to become steam of about 140 ° C. having almost no wetness. As is apparent from FIG. 5, the waste heat fluid is 200 ° C. due to the generation of steam in which the boiling point of water is 140 ° C.
While a sensible heat of 50 ° C. is consumed from a liquid temperature of 35 ° C. to a boiling point, the waste heat fluid is 11 ° C. from 150 ° C. to 139 ° C.
Consumes only ℃ of sensible heat. That is, when heating water at 35 ° C. to generate steam at 140 ° C., the waste heat fluid at 200 ° C. can be used only up to 139 ° C. Therefore, there is a problem that the amount of generated steam is reduced and the heat utilization rate is extremely reduced.

[0005]

As described above, in the conventional waste heat energy conversion system, there is a problem that the heat utilization rate becomes extremely low when the steam temperature is raised, and there has been a strong demand for solving the problem. Accordingly, an object of the present invention is to solve such a problem and to provide a new waste heat energy conversion system capable of achieving a high heat utilization rate of waste heat fluid even when the steam temperature is increased.

[0006]

According to the first aspect of the present invention, waste heat energy is generated by generating steam in a steam generator using waste heat as a heat source and exchanging the heat energy with a heat exchange device. It is a conversion system. This system is characterized in that the medium that generates steam by exchanging heat with the waste heat fluid is a non-azeotropic mixed fluid having a lower boiling point than water. The invention according to claim 2 is a preferred embodiment of the waste heat energy conversion system according to claim 1, wherein the steam generator is installed in the steam generation area, and the generated steam is separated from the steam generation area. The non-azeotropic mixed fluid liquefied by the heat exchange is transferred to the steam generator by the pipe installed with the pump. And

[0007] Further, the invention according to claim 3 is based on claim 2.
In a more preferred embodiment of the waste heat energy conversion system according to the above, wherein the liquefied non-azeotropic mixed fluid is recovered in a drain recovery unit installed below the heat exchange device, the recovered non-azeotropic The mixed fluid is transferred to a steam generator. Next, the invention according to claim 4 is a more preferred embodiment of the waste heat energy conversion system according to claim 3, wherein the liquid level of the drain recovery section is controlled to a preset value. Features.

The invention according to claim 5 is a more preferred embodiment of the waste heat energy conversion system according to claim 4, wherein the liquid level is preset by changing the rotation speed of the pump. It is characterized by being controlled so as to obtain a value. Further, the invention according to claim 6 is a more preferable embodiment of the waste heat energy conversion system according to claim 5, wherein a liquid level detection unit that detects a liquid level of the drain recovery unit, and the liquid level detection A control unit that outputs a control signal so that the detection value of the unit matches a preset value; and an inverter device that adjusts the speed of an AC motor that drives the pump based on the control signal.

The invention described in claim 7 is the first invention.
Another preferred embodiment of the waste heat energy conversion system according to any one of claims to 6, wherein the temperature of the steam flowing out of the steam generator is controlled to a predetermined value. Next, an eighth aspect of the present invention is a more preferable embodiment of the waste heat energy conversion system according to the seventh aspect, wherein a part of the waste heat fluid supplied to the steam generator is bypassed. The steam temperature is controlled.

A ninth aspect of the present invention is a preferred embodiment of the waste heat energy conversion system according to any one of the first to eighth aspects, wherein the non-azeotropic mixed fluid is an aqueous ammonia solution or an alcohol-based fluid. It is characterized by being an aqueous solution or a CFC-based solution. Further, the invention according to claim 10 is a preferred embodiment of the waste heat energy conversion system according to any one of claims 1 to 9, wherein the concentration of the low boiling point component of the non-azeotropic mixed fluid is reduced. It is characterized in that it is configured to be adjusted.

An eleventh aspect of the present invention is a preferred embodiment of the waste heat energy conversion system according to the tenth aspect, wherein a mixture of steam and liquid is supplied from a heat transfer tube near a steam outlet of a steam generator. A part is extracted, and a separation tank for separating at least a part of the extracted air as a liquid component is provided, and a steam component discharged from the separation tank is mixed with steam transferred to a heat exchange device, so It is characterized in that the concentration of the low boiling point component of the boiling mixed fluid is increased. Next, the invention described in claim 12 is the first invention.
Another preferred embodiment of the waste heat energy conversion system according to claim 0, wherein a part of the mixture of steam and liquid is bled from a heat transfer tube close to the inlet of the non-azeotropic mixed fluid of the steam generator, A separation tank for separating at least a part of the extracted gas as a vapor component is provided, and the liquid component discharged from the separation tank is returned to the non-azeotropic mixed fluid side, whereby the concentration of the low boiling point component of the non-azeotropic mixed fluid is reduced. Is reduced.

[0012]

Next, embodiments of the present invention will be described with reference to the drawings. First, the action of the non-azeotropic mixed fluid will be described using an aqueous ammonia solution as an example. FIG. 2 is a gas-liquid equilibrium diagram at a pressure of 550 kPa using the mass fraction of ammonia as a parameter.
5 (concentration 45%) ammonia aqueous solution, 50 ℃
At about the temperature, evaporation starts, and at about 135 ° C., a vapor phase region is formed. The reason why the evaporation is started in the relatively low temperature range is due to the characteristics of ammonia and the reason that the aqueous solution thereof is a non-azeotropic mixed fluid.

When a steam generator generates heat by exchanging an aqueous ammonia solution having a mass fraction of 0.45 with a waste heat fluid, the temperature relationship is as shown in FIG. FIG. 3 shows the temperature change between the waste heat fluid and the aqueous ammonia solution using the distance of the heat transfer tube in the steam generator as a parameter.
The waste heat fluid (a) supplied to the steam generator at 0 ° C. undergoes heat exchange with the aqueous ammonia solution (b), and its temperature drops.
Elutes at about ° C. On the other hand, an aqueous ammonia solution (b) is supplied to a steam generator at, for example, 35 ° C.
Evaporation starts at about 135 ° C., continues to about 135 ° C., and is further heated to about 140 ° C. before flowing out of the steam generator. Since the aqueous ammonia solution is in a vaporized state in most of the region of the heat transfer tube, the heat transfer coefficient can be kept sufficiently high. In addition, the boiling region is 50 to 1
Since it is as wide as 35 ° C., the waste heat fluid side temperature can be used in a wide range of 200 to 50 ° C., and more heat can be used. Therefore, the thermal energy of the waste heat fluid can be effectively used.

FIG. 4 shows a temperature relationship when the ammonia water vapor generated as described above is supplied to a heat exchange device of a load facility to exchange heat with air. FIG. 4 shows the temperature change between ammonia water vapor and air using the distance of the heat transfer tube in the heat exchange device as a parameter. Ammonia water vapor (c) at about 140 ° C. enters the steam inlet of the heat exchange device and exchanges heat with air in countercurrent. Then, the condensation immediately starts, and the liquid whose temperature has dropped to about 35 ° C. flows out of the outlet. On the other hand, the air supplied to the heat exchanger at about 20 ° C. is heated to about 55 ° C. and discharged from the heat exchanger. As can be seen from FIG.
Since most of the heat transfer tubes in the heat exchange device are in the condensing region, the heat exchange device can be operated with a high heat transfer coefficient.

The type of the non-azeotropic mixed fluid used in the present invention is not particularly limited as long as it has a boiling point lower than that of water. Preferred non-azeotropic mixed fluids include an aqueous alcoholic solution and a fluorocarbon solution in addition to an aqueous ammonia solution. When an alcohol-based aqueous solution is used, it is necessary to select a component that does not cause azeotropy with water. Such alcohols include, for example, methanol and low concentration ethanol.

FIG. 1 is a process flow chart showing one example of the waste heat energy conversion system of the present invention. A steam generating device 1 such as a boiler or a steam converter is installed in a steam generating area, and waste heat fluid such as hot water or hot water discharged and transferred from a facility such as a thermal power plant is sent from a pipe a to a pipe b via a pipe b. The heat is exchanged countercurrently with the non-azeotropic mixed fluid supplied to the generator 1 and flowing through the heat transfer tube, and is circulated to the facility from the pipe c to the pipe d. The non-azeotropic mixed fluid supplied from the pipe f enters the heat transfer pipe from the inlet A of the steam generator 1, is heated and becomes steam, and flows out from the steam outlet B to the pipe g. The steam is transferred to a steam use area separated from the steam generation area by a pipe g, and is supplied to each of a plurality of heat exchangers 2 such as an air handling unit installed in each of the pipes h. If it is inconvenient to transfer the non-azeotropic mixed fluid to the steam area, install a new heat exchanger in the steam generation area, and use the heat exchanger to remove water with the steam of the non-azeotropic mixed fluid. Heating may be used to generate steam or hot water, which may be transferred to an area where steam or hot water is used.

The non-azeotropic mixed fluid liquefied by exchanging heat with air in the heat exchange device 2 is collected from a pipe i through a pipe j to a drain recovery section 3 installed at a position below the heat exchange device 2. You. The non-azeotropic mixed fluid in the drain recovery section 3 is circulated to the steam generator 1 by each pipe f provided with the pump 4. A liquid level detecting section 5 for detecting a liquid level is provided in the drain collecting section 3.
Is provided, and the detection signal is input to the control unit 6. The control unit 6 outputs a control signal to the inverter device 8 so that the detection value of the liquid level detection unit 5 matches a value set in advance by the setting unit 7. That is, if the detected value of the liquid level is higher than the set value, a control signal for lowering the liquid level is output to the inverter device 8, and if the detected value of the liquid level is lower than the set value, the control for raising the liquid level is performed. The signal is output to the inverter device 8. In response to a control signal from the control unit 6, the inverter device 8 controls the phase of the AC to the AC motor that drives the pump 4, changes the power, and adjusts the speed. As the AC motor, a three-phase induction motor or the like can be used. By controlling the liquid level of the drain recovery unit 3 in this manner, the amount of steam supply (or the amount of generated steam) can be adjusted according to the load change in the steam use area.

A bleed pipe k is branched from a heat transfer pipe near the steam outlet B of the steam generator 1, and a mixture of steam and liquid extracted by the bleed pipe k passes through a valve 9 into a separation tank 10.
, Where the liquid component which is almost water is separated by gravity and discharged from the pipe 1 and stored in the recovery tank 12 via the valve 11. On the other hand, steam having a high concentration of a component other than water (for example, an ammonia component) forming a non-azeotropic mixed fluid flowing out of the separation tank 10 flows into the pipe g. Therefore, by adjusting the opening degree and opening time of the valve 9, the concentration of the non-azeotropic mixed fluid circulating in the system can be increased accordingly.

An extraction pipe m is branched from a heat transfer pipe near the inlet portion A of the non-azeotropic mixed fluid of the steam generator 1, and the extraction pipe m
The mixture of vapor and liquid extracted by the above is introduced into a separation tank 14 through a valve 13, where a gravity-separated liquid component close to water is discharged from a pipe n, and is passed through a valve 15 to a pipe f by a return pump 16. Will be returned. on the other hand,
The vapor having a high concentration of a component other than water (for example, an ammonia component) forming a non-azeotropic mixed fluid flowing out of the separation tank 14 is introduced from a pipe o into a condenser 17 where it is condensed and liquefied to form a pipe p. After that, it is stored in the recovery tank 18. Therefore, by adjusting the opening degree and the opening time of the valve 13, the concentration of the non-azeotropic mixed fluid circulating in the system can be reduced correspondingly. A refrigerant such as ammonia is circulated through the condenser 17 from a refrigerator (not shown). Supply water is supplied to the collection tank 12 from a pipe q.
A component other than water that forms a non-azeotropic mixed fluid is supplied from a pipe r. To supply the non-azeotropic mixed fluid in the system, the valve 20 of the pipe s connecting the collection tank 18 and the pipe of the return pump 16 or the valve 21 of the pipe t connecting the collection tank 12 and the pipe of the return pump 16 is opened. This is done by:

Between the pipes c and d for returning the waste heat fluid to the facility, 3
A direction valve 22 is provided. Further, a temperature detector 23 for detecting a steam temperature is provided in a pipe g connected to the outlet B of the steam generator 1, and the detection signal is input to the controller 24. The control unit 24 sets the detection value of the temperature detection unit 23
To match the value set in advance
Control. That is, when the steam temperature of the pipe g is higher than a preset temperature, a part of the waste heat fluid supplied from the pipe a to the steam generator 1 is returned to the pipe d by bypassing the pipe e, and vice versa. Is controlled to stop or reduce the return to the pipe d by bypass. In this way, the waste heat fluid supplied to the steam generator 1 changes according to the amount of steam generated.

[0021]

As described above, the waste heat energy conversion system according to the first aspect uses a non-azeotropic mixed fluid having a boiling point lower than that of water as a medium for exchanging heat with the waste heat fluid to generate steam. Therefore, the heat transfer coefficient with the waste heat fluid can be kept sufficiently high, and the heat energy of the waste heat fluid can be effectively and efficiently used even when a high steam temperature is obtained. Further, in the waste heat energy conversion system according to claim 2, in the above system, the steam generation device is installed in the steam generation area, and the generated steam is transferred to the steam use area separated from the steam generation area by piping and installed there. The non-azeotropic mixed fluid that has been heat-exchanged by the heat exchange device that has been liquefied by the heat exchange is transferred to the steam generator by a pipe provided with a pump, so that the non-azeotropic mixed fluid can be efficiently used without waste. To increase operating efficiency.

Further, in the waste heat energy conversion system according to the third aspect, in the above system, the liquefied non-azeotropic mixed fluid is recovered in a drain recovery section provided below the heat exchange device, and the recovered non-azeotropic fluid is recovered. Since the azeotropic mixed fluid is transferred to the steam generator, the steam used in the steam use area can be efficiently recovered as a non-azeotropic mixed fluid and circulated to the steam generator. Next, in the waste heat energy conversion system according to the fourth aspect, the liquid level in the drain recovery section is controlled to a preset value, so that the non-azeotropic mixed fluid is recovered and circulated to the steam generator. Can be performed more stably.

Further, in the waste heat energy conversion system according to the present invention, since the rotation speed of the pump for transferring the liquid level of the drain recovery section to the steam generator is changed and controlled, the energy cost is low. A non-azeotropic mixed fluid can be circulated to the steam generator. Further, the waste heat energy conversion system according to claim 6, wherein the liquid level detection unit for detecting the liquid level of the drain recovery unit, and a control signal to match the detection value of the liquid level detection unit to a preset value. It has a control unit that outputs and an inverter that adjusts the speed of the AC motor that drives the pump with control signals, so that the liquid level in the drain recovery unit can be controlled with high accuracy and the generation of non-azeotropic mixed fluid vapor Circulation to the device can be performed more stably.

In the waste heat energy conversion system according to the present invention, the temperature of the steam flowing out of the steam generator is controlled to a predetermined value, so that constant and stable steam is supplied to load equipment such as a heat exchanger. Can be supplied. Next, in the waste heat energy conversion system according to claim 8, since the temperature control of the steam is performed by bypassing a part of the waste heat fluid supplied to the steam generator, the waste heat energy is proportional to the amount of the generated steam. Fluid can be supplied to the steam generator. Therefore, the waste heat fluid can be used efficiently without waste.

A waste heat energy conversion system according to a ninth aspect is characterized in that the non-azeotropic mixed fluid used in each of the above systems is an aqueous ammonia solution, an aqueous alcohol solution or a chlorofluorocarbon solution. Can maintain the system stable and operate efficiently. Next, the waste heat energy conversion system according to claim 10 is configured such that the concentration of the low boiling point component of the non-azeotropic mixed fluid can be adjusted in each of the above systems. Can occur freely.

[0026] In the waste heat energy conversion system according to the eleventh aspect, a part of the mixture of steam and liquid is extracted from the heat transfer tube near the steam outlet of the steam generator, and at least a part of the extraction is performed. Is provided as a liquid component, and the steam component discharged from the separation tank is mixed with the steam transferred to the heat exchange device, so that the concentration of the low boiling component of the non-azeotropic mixed fluid can be efficiently reduced. Can be ascended. Further, in the waste heat energy conversion system according to claim 12, a part of the mixture of steam and liquid is extracted from the heat transfer tube near the inlet of the non-azeotropic mixed fluid of the steam generator in the system, and during the extraction, A separation tank that separates at least a part as a vapor component is provided, and the liquid component discharged from the separation tank is configured to return to the non-azeotropic mixed fluid side. Can be efficiently reduced.

[Brief description of the drawings]

FIG. 1 is a process flow diagram of a waste heat energy conversion system of the present invention.

FIG. 2 shows that the mass fraction of ammonia is 55
Vapor-liquid equilibrium diagram of the aqueous ammonia solution at a pressure of 0 kPa.

FIG. 3 is a diagram showing a temperature relationship in a case where steam is generated by exchanging heat with waste heat fluid in a steam generator using the aqueous ammonia solution of FIG. 2;

FIG. 4 is a diagram showing a temperature relationship when heat is exchanged with air by a heat exchange device as a load facility using ammonia water vapor.

FIG. 5 is a diagram showing a temperature relationship when steam obtained by evaporating water is used to generate steam by exchanging heat with waste heat fluid in a steam generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steam generator 2 Heat exchange device 3 Drain recovery part 4 Pump 5 Liquid level detection part 6 Control part 7 Setting device 8 Inverter device 9 Valve 10 Separation tank 11 Valve 12 Recovery tank 13 Valve 14 Separation tank 15 Valve 16 Return pump 17 Condensation Container 18 Recovery tank 20 Valve 21 Valve 22 Three-way valve 23 Temperature detection unit 24 Control unit 25 Setting unit at to piping

Claims (12)

[Claims] 1. A waste heat energy conversion system in which steam is generated by a steam generator 1 using waste heat as a heat source, and heat energy of the steam is exchanged by a heat exchange device 2 for heat exchange with a waste heat fluid. A waste heat energy conversion system, wherein the medium for generating steam is a non-azeotropic mixed fluid having a lower boiling point than water. 2. A steam generating device 1 is installed in a steam generating area, and the generated steam is transferred by piping to a steam using area remote from the steam generating area, and heat is exchanged by a heat exchanging device 2 installed there. The waste heat energy conversion system according to claim 1, wherein the non-azeotropic mixed fluid liquefied by the heat exchange is transferred to the steam generator 1 by a pipe provided with a pump 4. 3. A liquefied non-azeotropic mixed fluid is recovered in a drain recovery unit 3 installed below the heat exchange device 2, and the recovered non-azeotropic mixed fluid is transferred to the steam generator 1. The waste heat energy conversion system according to claim 2. 4. The waste heat energy conversion system according to claim 3, wherein the liquid level of the drain recovery unit 3 is controlled to a preset value. 5. The waste heat energy conversion system according to claim 4, wherein the liquid level of the drain recovery unit 3 is controlled to be a preset value by changing the rotation speed of the pump 4. 6. A liquid level detecting section 5 for detecting a liquid level of the drain collecting section 3, and a control section 6 for outputting a control signal so that a detected value of the liquid level detecting section 5 coincides with a preset value. The waste heat energy conversion system according to claim 5, further comprising an inverter device (8) for adjusting a speed of an AC motor that drives the pump (4) according to the control signal. 7. The waste heat energy conversion system according to claim 1, wherein the temperature of the steam flowing out of the steam generator 1 is controlled to a predetermined value. 8. The waste heat energy conversion system according to claim 7, wherein the temperature of the steam is controlled by bypassing a part of the waste heat fluid supplied to the steam generator 1. 9. The non-azeotropic fluid is an aqueous ammonia solution, an aqueous alcohol solution or a fluorocarbon solution.
A waste heat energy conversion system according to claim 8. 10. The waste heat energy conversion system according to claim 1, wherein the concentration of the low boiling point component of the non-azeotropic mixed fluid is adjustable. 11. A separation tank 10 for extracting a part of a mixture of steam and liquid from a heat transfer tube near a steam outlet B of a steam generator 1 and separating at least a part of the extracted air as a liquid component is provided. By mixing the steam component discharged from the separation tank 10 with the steam transferred to the heat exchange device 2,
The waste heat energy conversion system according to claim 10, wherein the concentration of the low boiling point component of the non-azeotropic mixed fluid is increased. 12. A separation for extracting a part of a mixture of steam and liquid from a heat transfer tube near an inlet portion A of a non-azeotropic mixed fluid of a steam generator 1, and separating at least a part of the extracted air as a vapor component. A tank 14 is provided, and the liquid component discharged from the separation tank 14 is returned to the non-azeotropic mixed fluid side,
The waste heat energy conversion system according to claim 10, wherein a concentration of the low boiling point component of the non-azeotropic mixed fluid is reduced.