WO2012096439A1

WO2012096439A1 - Cascade and multi-stage rankine cycle device for cold power generation

Info

Publication number: WO2012096439A1
Application number: PCT/KR2011/009002
Authority: WO
Inventors: 장대준; 김기홍
Original assignee: 한국과학기술원
Priority date: 2011-01-14
Filing date: 2011-11-24
Publication date: 2012-07-19
Also published as: KR101339777B1; KR20120082667A

Abstract

The present invention relates to a cascade and multi-stage Rankine cycle device for cold power generation, and the object of the present invention is to provide a cascade and multi-stage Rankine cycle device for cold power generation, wherein efficiency is increased through the use of an improved Rankine cycle device.

Description

Cascade and multi-stage Rankine cycle units for cold heat generation

The present invention relates to a cascade and a multi-stage Rankine cycle apparatus for cold heat generation, and more particularly to a cascade for cold heat generation, in which the configuration is further improved to increase the efficiency of a Rankine cycle apparatus used for cold heat generation or temperature difference generation. A multistage Rankine cycle apparatus.

Low-temperature heat source generated when vaporizing liquefied natural gas or liquid carbon dioxide, low-temperature heat source obtained from seawater temperature that gets deeper with deeper water, high-temperature heat source obtained from high temperature in the ground, high-temperature heat source obtained from exhaust gas of engine and turbine The Rankine cycle can be utilized when there is a heat source that is hotter or lower than a medium such as water, air, etc., which can be easily obtained from the surroundings.

1 illustrates various conventional forms of cold power generation. Figure 1 (A) shows the most basic Rankine cycle apparatus, such a simple Rankine cycle apparatus is generally used for the temperature difference generation of seawater, the vaporization process of low temperature liquid such as LNG, geothermal power generation. As shown in Fig. 1A, the simple Rankine cycle apparatus consists of a condenser, a pump, an evaporator, a turbine, and a working fluid to circulate each part. The working fluid is condensed by exchanging heat with the low temperature heat source (Q _L ) in the condenser. The working fluid introduced into the evaporator is evaporated by heat exchange with a high temperature heat source (Q _H , sea water or air) in the evaporator to become a gas state. The working fluid in the gaseous state circulates through the turbine to generate energy and then flow back into the condenser. Shown on the right side of FIG. 1A is a temperature-entropy plot of this simple Rankine cycle.

The Rankine cycle apparatus is a basic heat exchange cycle apparatus, which may be used for cooling by absorbing evaporation heat from the outside in the evaporator section and cooling the surroundings, or heating the surroundings by dissipating condensation heat from the condenser section to the outside. In some cases, in the case of cold heat power generation, power is generated by generating energy from the turbine portion.

FIG. 1 (B) shows a form of LNG cold heat generation, which is a form of cold heat generation using such a simple Rankine cycle apparatus. The LNG cold power plant shown in FIG. 1 (B) is similar in structure to a simple Rankine cycle unit (the working fluid circulates condenser-pump-evaporator-turbine in sequence), using seawater as a high temperature heat source. LNG cold heat is used as a low temperature heat source. In general, propane liquid is widely used as a working fluid for LNG cold heat generation. In the LNG cold heat generation, the evaporator is provided with a flow path through which seawater flows separately from the flow path through which the working fluid flows, and the condenser also has a flow path through which LNG passes separately from the flow path through which the working fluid flows. According to this configuration, in the evaporator, the working fluid exchanges heat with seawater to absorb evaporation heat from the seawater, and in the condenser, the working fluid exchanges heat with LNG to condense by dissipating heat of condensation with LNG. Of course, the seawater introduced into the evaporator is cooled by being deprived of the evaporation heat to the working fluid is cooled and discharged at low temperature, LNG is supplied to the condenser as a liquid state is supplied to the condensation heat emitted from the working fluid to be discharged into a gaseous state.

However, in such LNG cold power generation, there is a disadvantage in that efficiency is reduced by directly exchanging heat with seawater without using the cold heat of propane liquid, which is a working fluid. In addition, there is also a disadvantage in that the efficiency of the heat exchanger logarithmic temperature difference is further reduced because the cold heat of the LNG and the propane liquid heat exchange using a single condenser.

FIG. 1 (C) shows a form of seawater temperature differential power generation, which is similar to the LNG cold heat generating apparatus shown in FIG. 1 (B), but uses shallow water (shallow depth seawater) as a high temperature heat source and a low temperature heat source. The only difference is that they use deep sea water. In this case, the same problem as that of the LNG cold heat generating device was inferior in efficiency.

As described above, it has been pointed out among those skilled in the art that conventional cold heat generating apparatuses require many improvements in efficiency.

Accordingly, the present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to provide a cascade and a multi-stage Rankine cycle apparatus for cold heat generation, which has increased efficiency by using an improved Rankine cycle apparatus. In providing.

Cascade and multi-stage Rankine cycle apparatus for cold heat power generation of the present invention for achieving the object as described above, the working fluid is circulated therein to perform cold heat power generation using a high temperature heat source 210 and a low temperature heat source 220. Rankine cycle apparatus 100, comprising: an evaporator (110) for evaporating a working fluid by heat exchange with a high temperature heat source (210); An n-th turbine 12n that expands the working fluid discharged from the evaporator 110 to generate energy, and an n-th heat exchanger condenses the working fluid discharged from the n-th turbine 12n with the low temperature heat source 220. An n-circulating part including an n-condenser 13n and an n-pump 14n configured to compress the working fluid discharged from the n-th condenser 13n and then flow into the evaporator 110 to circulate the working fluid. 15n); It is made, including, the n-th circulation unit (15n) is provided with N, the low-temperature heat source 220 is N number of n-th circulation unit (15n) from the first circulation unit 151 to the N-th circulation unit ( It is characterized in that it is formed to pass sequentially up to 15N).

(Wherein n = 1,…, N and an integer greater than or equal to 2)

At this time, the Rankine cycle apparatus 100 is a cascade Rankine cycle apparatus 100A, in which the working fluid discharged from the nth pump 14n passes through the nth pump 14n and the n + 1 condenser 13n + 1. In order to be sequentially introduced into the end, it is characterized in that the working fluid circulation path is formed so that the working fluid discharged from the N-th condenser (13N) flows into the evaporator (110).

Alternatively, the Rankine cycle apparatus 100 is a multi-stage Rankine cycle apparatus 100B, in which working fluid discharged from the nth pump 14n flows into the evaporator 110 through the nth pump 14n, respectively. In the n-th circulation part 15n, a working fluid circulation path independent of each other is formed. At this time, the Rankine cycle device 100 is characterized in that the physical properties or operating conditions of the working fluid circulated in each of the n-th circulation unit (15n) is formed differently.

At this time, the multi-stage Rankine cycle apparatus 100B is a working fluid circulated in each of the n-th circulation portion 15n is the same material, n = 1, ... As it increases to N, it is characterized in that the operating pressure is formed to increase.

Alternatively, in the multi-stage Rankine cycle apparatus 100B, the working fluid circulated in each of the nth circulation units 15n may be different materials, and n = 1,... As it increases to N, it is characterized in that it is formed to have a high boiling point.

According to the present invention, by introducing a Rankine cycle apparatus employing a cascade system or a multi-stage system, there is a great effect that the efficiency in cold heat generation can be greatly increased than before. More specifically, in the case of applying the cascade method, according to the present invention, in addition to the existing low-temperature heat source, there is an advantage of using the low-temperature heat source of the working fluid used in the Rankine cycle apparatus to obtain more energy.

In addition, both the cascade method and the multi-stage method according to the present invention has the effect of obtaining a high efficiency by utilizing a low temperature heat source for each temperature band.

In addition, according to the present invention, in addition to propane, ammonia, which has been mainly used as a working fluid, there is a big advantage that various working fluids can be introduced to obtain higher efficiency for each temperature range.

1 is a Rankine cycle apparatus for conventional cold heat generation.

2 and 3 is a Rankine cycle device for cold heat generation of the present invention.

100: Rankine cycle apparatus 110 of the present invention evaporator

12n: n-th turbine 13n: n-th condenser

14n: nth pump 15n: nth circulation part

210: high temperature heat source 220: low temperature heat source

Hereinafter, a cascade and a multi-stage Rankine cycle apparatus for cold heat generation according to the present invention having the configuration as described above will be described in detail with reference to the accompanying drawings.

In the present invention, unlike the conventional heat generation using only a single Rankine cycle, the cold power generation is performed using a plurality of Rankine cycles, each Rankine cycle is to share the evaporator, each condenser Allow the low temperature heat source to pass sequentially.

Referring to Figure 3 in more detail as follows. In the cascade and multi-stage Rankine cycle apparatus for cold heat generation of the present invention, in the Rankine cycle apparatus 100 in which a working fluid circulates and performs cold heat generation using a high temperature heat source 210 and a low temperature heat source 220. An evaporator 110 for evaporating the working fluid by exchanging heat with the high temperature heat source 210; An n-th turbine 12n that expands the working fluid discharged from the evaporator 110 to generate energy, and an n-th heat exchanger condenses the working fluid discharged from the n-th turbine 12n with the low temperature heat source 220. An n-circulating part including an n-condenser 13n and an n-pump 14n configured to compress the working fluid discharged from the n-th condenser 13n and then flow into the evaporator 110 to circulate the working fluid. 15n); It is made, including, the n-th circulation unit (15n) is provided with N, the low-temperature heat source 220 is N number of n-th circulation unit (15n) from the first circulation unit 151 to the N-th circulation unit ( Up to 15N). At this time, n = 1,... , N, and an integer equal to or greater than N = 2, in the example of FIG. 2, the case where N is 3 is illustrated.

At this time, Fig. 3A shows the first embodiment to which the cascade method is applied, and Fig. 3B shows the second embodiment to which the multi-stage method is applied. Hereinafter, each method will be described in more detail with reference to FIGS. 2 and 3.

2 (A) and 3 (A) show a first embodiment of the Rankine cycle apparatus for cold heat generation of the present invention, to which the cascade method is applied. In the first embodiment, the working fluid, which is cooled by heat exchange with a low temperature heat source in the condenser and compressed by passing through a pump, is used as a low temperature heat source in another Rankine cycle condenser without directly flowing into the evaporator without directly flowing into the evaporator. .

In more detail, in the first embodiment, the Rankine cycle apparatus 100 is a cascade Rankine cycle apparatus 100A, and the working fluid discharged from the n-th pump 14n passes through the n-th pump 14n and n + 1 condenser (13n + 1) is sequentially introduced, and finally the working fluid circulation path is formed so that the working fluid discharged from the N-th condenser (13N) flows into the evaporator (110).

Referring to Figure 2 (A) sequentially as follows. First, the low temperature heat source 220 is introduced into the first condenser 131, discharged from the evaporator 110, and the first heat exchanger with the working fluid introduced into the first condenser 131 via the first turbine 121. Will be At this time, the working fluid is condensed by heat exchange to change into a liquid phase, and the low temperature heat source 220 absorbs the condensation heat emitted from the working fluid and discharges after the temperature rises slightly before entering the first condenser 131. Will be. The low temperature heat source 220 is then introduced into the second condenser 132 and discharged from the evaporator 110 to exchange heat with the working fluid introduced into the second condenser 132 via the second turbine 122. In this case, the working fluid is discharged from the first condenser 131 and heat exchanged with the working fluid introduced into the second condenser 132 via the first pump 141. That is, in the second condenser 132, the working fluid exchanges heat between the two fluids, the working fluid which has passed through the low temperature heat source 220 and the first condenser 131 (and the first pump 141). Will be done.

At this time, the working fluid is also condensed by heat exchange to change into a liquid phase and then flows into the third condenser 133 via the second pump 142. In addition, the low temperature heat source 220 is discharged from the first condenser 131 is discharged after the temperature rises a little more than before entering the second condenser 132. Finally, the low temperature heat source 220 is introduced into the third condenser 133 to perform the third heat exchange with the working fluid. In the third condenser 133, similar to the second condenser 132, the working fluid passes through the low temperature heat source 220, the first condenser 131 (and the first pump 141). The working fluid coming out, the working fluid coming out through the second condenser 132 (and the second pump 142), and the three fluids will exchange heat.

Referring to FIG. 3 (A), the generalization is as follows. The low temperature heat source 220 is the first condenser 131, the second condenser 132, ... The temperature rises step by step while passing sequentially. Of course, even if the temperature rises little by little, since the low temperature heat source 220 is a lower temperature than the working fluid, all the working fluids passing through the

respective condensers

131, 132, 133 (…) can be condensed properly. Will be. In addition, the working fluid passing through the n-th condenser 13n flows into the n + 1 condenser 13n + 1 through the n-th pump 14n, and together with the low temperature heat source 220, the n-th condenser 13n. Heat exchange with the working fluid circulating through). That is, in the second condenser 132, the working fluid exchanges heat with the working fluid, ie, two fluids that have passed through the low temperature heat source 220 and the first condenser 131, and in the third condenser 133, the working fluid is the low temperature heat source. (220), the working fluid that has passed through the first condenser (131), the working fluid that has passed through the second condenser (132), that is, heat exchanges with the three fluids,. In the Nth condenser 13N, the working fluid passes through the low temperature heat source 220, the first condenser 131, the working fluid that has passed through the second condenser 132,... In other words, the heat exchanged with the working fluid, that is, the N fluids that have passed through the N-1 condenser 13N-1.

As described above, in the Rankine cycle apparatus 100A to which the cascade method is applied, the working fluid circulating through each of the circulation portions 151 (...) 15N is discharged from the low temperature heat source 220 and the circulation portion at the front end thereof. By exchanging heat with the working fluids, it is possible to raise the power generation efficiency much more conventionally.

Figure 3 shows a second embodiment of the Rankine cycle apparatus for cold heat generation of the present invention, applying a multi-stage scheme. In the second embodiment, in utilizing the low temperature heat source, as the temperature of the low temperature heat source rises, the Rankine cycle suitable for each temperature is configured to increase the efficiency.

In more detail, in the second embodiment, the Rankine cycle apparatus 100 is a multi-stage Rankine cycle apparatus 100B, in which the working fluid discharged from the n-th pump 14n passes through the n-th pump 14n. 110, the working fluid circulation paths which are independent of each other are formed in each of the nth circulation part 15n.

A description with reference to FIG. 2 (B) is as follows. First, the low temperature heat source 220 is introduced into the first condenser 131, discharged from the evaporator 110, and the first heat exchanger with the working fluid introduced into the first condenser 131 via the first turbine 121. Will be At this time, the working fluid is condensed by heat exchange to change into a liquid phase, and the low temperature heat source 220 absorbs the condensation heat emitted from the working fluid and discharges after the temperature rises slightly before entering the first condenser 131. Will be. Unlike the cascade Rankine cycle apparatus 100A shown in FIG. 2 (A) (and FIG. 3 (A)), in the multi-stage Rankine cycle apparatus 100B, the working fluid passes through the first pump 141 to the evaporator 110. Flows directly into the loop, forming a circulation path independent of the other circulation sections.

The low temperature heat source 220 is then introduced into the second condenser 132 and discharged from the evaporator 110 to exchange heat with the working fluid introduced into the second condenser 132 via the second turbine 122. As in the first circulation part 151, the working fluid flows directly into the evaporator 110 through the second pump 142 after heat exchange. The same process occurs in the third circulation unit 153.

Referring to FIG. 3 (B), the generalization is as follows. Unlike the cascade Rankine cycle apparatus 100A, in which each of the circulation parts 15n exchanges heat with the working fluids passing through the low temperature heat source 220 and the front end of the circulation parts 15n, the multi-stage Rankine cycle device ( In 100B), the working fluid in each circulation section 15n forms an independent working fluid circulation path, and in each condenser 13n in each circulation section 15n, the working fluid is the low temperature heat source 220. Only heat exchange with). However, unlike the conventional Rankine cycle apparatus, the low temperature heat source 220 is gradually increased in temperature while passing through each circulation portion 15n sequentially, in this way, the temperature of the low temperature heat source 220 is slightly Even if it rises, it is possible to condense the working fluid by heat exchange with the working fluid, so that the multi-stage Rankine cycle apparatus 100B can also increase the power generation efficiency much more than the conventional Rankine cycle apparatus.

At this time, the Rankine cycle apparatus 100 can further increase the power generation efficiency by allowing the physical properties or operating conditions of the working fluid circulated in the n-th circulation unit 15n to be formed differently. In the first embodiment shown in FIGS. 2 (A) and 3 (A), that is, the cascade Rankine cycle apparatus 100A, a working fluid in each circulation section is brought through the low temperature heat source 220 and the previous circulation sections. In the second embodiment shown in FIGS. 2 (B) and 3 (B), that is, in the multistage Rankine cycle apparatus 100B, the working fluid is only at the low Heat exchange only with the heat source 220. However, in the second embodiment, since each circulation section forms a working fluid circulation path independent of each other, the efficiency can be increased by changing the physical properties or operating conditions of the working fluid in each circulation section.

For example, in the multi-stage Rankine cycle apparatus 100B, the working fluids circulated in each of the nth circulation units 15n are all the same material, and n = 1,... As the pressure increases to N, the operating pressure can be increased. Alternatively, in the multi-stage Rankine cycle apparatus 100B, the working fluid circulated in each of the nth circulation units 15n may be different materials, and n = 1,... As it increases to N, it can be formed to have a high boiling point.

The present invention is not limited to the above-described embodiments, and the scope of application of the present invention is not limited to those of ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention as claimed in the claims. Of course, various modifications can be made.

According to the present invention, it is possible to provide a cascade and a multi-stage Rankine cycle apparatus for cold heat generation, which have improved efficiency by using an improved Rankine cycle apparatus.

Claims

In the Rankine cycle device 100, the working fluid circulates therein and performs cold heat power generation using the high temperature heat source 210 and the low temperature heat source 220.

An evaporator 110 for evaporating the working fluid by exchanging heat with the high temperature heat source 210;

An n-th turbine 12n that expands the working fluid discharged from the evaporator 110 to generate energy, and an n-th heat exchanger condenses the working fluid discharged from the n-th turbine 12n with the low temperature heat source 220. An n-circulating part including an n-condenser 13n and an n-pump 14n configured to compress the working fluid discharged from the n-th condenser 13n and then flow into the evaporator 110 to circulate the working fluid. 15n);

Including but not limited to,

The nth circulation part 15n is provided, and the low temperature heat source 220 sequentially passes the Nth nth circulation parts 15n from the first circulation part 151 to the Nth circulation part 15N. Cascade and multi-stage Rankine cycle apparatus for cold heat generation, characterized in that it is formed to.

(Wherein n = 1,…, N and an integer greater than or equal to 2)
According to claim 1, wherein the Rankine cycle apparatus 100

As the cascade Rankine cycle apparatus 100A,

The working fluid discharged from the nth pump 14n is sequentially introduced into the n + 1 condenser 13n + 1 via the nth pump 14n, and finally, the working fluid discharged from the Nth condenser 13N Cascade and multi-stage Rankine cycle apparatus for cold heat power generation, characterized in that the working fluid circulation path is formed to enter the evaporator (110).
According to claim 1, wherein the Rankine cycle apparatus 100

As a multistage Rankine cycle apparatus 100B,

The working fluid discharged from the n-th pump 14n flows into the evaporator 110 through the n-th pump 14n to form a working fluid circulation path independent of each other in each of the n-th circulation parts 15n. Cascade and multi-stage Rankine cycle device for cold heat generation, characterized in that.
4. The multistage Rankine cycle apparatus 100B according to claim 3, wherein

Cascade and multi-stage Rankine cycle apparatus for cold heat generation, characterized in that the physical properties or operating conditions of the working fluid circulated in each of the n-th circulation unit (15n) is formed differently.
The multistage Rankine cycle apparatus 100B according to claim 4, wherein

The working fluids circulated in each of the nth circulation parts 15n are all the same material, and n = 1,. Cascade and multi-stage Rankine cycle apparatus for cold heat generation, characterized in that formed to increase the operating pressure as it increases to, N.
The multistage Rankine cycle apparatus 100B according to claim 4, wherein

The working fluid circulated in each of the nth circulation parts 15n is made of a different material, and n = 1,. Cascade and multi-stage Rankine cycle apparatus for cold heat generation, characterized in that it is formed to have a high boiling point as it increases to N.