JPS58214606A - Two fluid cycle - Google Patents

Abstract

PURPOSE:To collect effectively the exhaust gas energy and thereby enhance the thermal efficiency of Rankin's cycle by combining the water Rankin cycle for processing of high temperature part of the heat source with the organic medium Rankin cycle for processing of the low temperature part of the heat source. CONSTITUTION:Steam generated at a water boiler 1 installed in the high temp. part makes his work at a turbine 3 to be then led to a condenser 5 and feed water heater 7. This feed water heater uses exhaust steam from a florinol 85 turbine 10 as heat source. Florinol 85 steam produced by a low temp. side boiler 2 makes his work at the florinol 85 turbine 10 to be then led to the feed water heater 7, where th steam heats the condensed water of the water cycle. Thus the cycle thermal efficiency can be enhanced throughout the two fluid cycle.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-fluid cycle that combines a water cycle and an organic medium cycle to effectively recover exhaust gas energy from boilers, processes, etc., and improves the thermal efficiency of the Rankine cycle.

Lowering the boiler exhaust gas temperature is effective in increasing boiler efficiency. In conventional boilers, due to the steam conditions (pressure), the boiler itself cannot sufficiently lower the exhaust gas temperature, and countermeasures have been taken to lower the exhaust gas temperature by installing energy savers and air preheaters. Exhaust gas temperature of about ~200°C remains.

In waste heat boilers that use process exhaust gas, the gas temperature at the inlet side is usually as low as 500°C, so the question is how to lower the temperature of this exhaust gas in the boiler with a low-temperature oven and effectively utilize its retained heat. The reality is that people are struggling with this.

The single-fluid Rankine cycle, which uses an organic medium such as fluorocarbons, has already been realized as a method of lowering the boiler exhaust gas temperature to a low temperature and effectively recovering the retained heat, and it can lower the exhaust gas temperature compared to the water cycle and has a certain level of efficiency. It has been effective. However, these media have drawbacks such as an upper limit to the temperature of the medium itself, and thermal decomposition occurs when the temperature exceeds a certain temperature, so when considering the Rankine cycle of the medium, it is important to take advantage of the high temperature part on the gas side. There are problems such as not having one.

In other words, in a normal water cycle, the pressure and temperature of steam can be raised to match the high temperature conditions of the heat source in order to increase cycle efficiency, but the temperature of the exhaust gas from the heat source cannot be lowered to a sufficiently low temperature. Although it is possible to increase the efficiency of the Rankine cycle, the amount of heat recovered from the low temperature side of the heat source is reduced, resulting in wasteful waste of exhaust gas energy, and the amount of power recovered is reduced. On the other hand, in a single-fluid cycle using an organic medium, heat recovery from the low-temperature side of the heat source can be made sufficient, but from the viewpoint of thermal decomposition of the organic medium itself, M: high i1! IN is regulated (approximately 300℃),
Since it cannot be used at higher temperatures, the Rankine cycle efficiency of the medium is limited by the temperature of this medium and is forced to a low level.

In the present invention, heat is recovered from the high-temperature part of the heat source by a conventional water Rankine cycle commensurate with the exhaust gas temperature, while heat is recovered from the low-temperature part of the heat source by an organic medium Rankine cycle that can efficiently recover low-temperature exhaust gas energy. By combining these two cycles, the heat amount of the heat source can be recovered to a sufficiently low temperature, and at the same time, the thermal efficiency of each cycle can be increased to the maximum that the heat source temperature allows, and the energy of the heat source can be used effectively to save energy. With the goal.

The gist of the present invention is to treat the high temperature part of the heat source with the water Rankine cycle, treat the low temperature part of the heat source with the organic medium Rankine cycle, and heat the feed water of the water cycle with the turbine exhaust of the organic medium cycle. It is a two-fluid cycle characterized by

The present invention will be explained below with reference to the drawings. FIG. 1 shows a system diagram of an embodiment of the present invention. In this example, Florinol 85 (hereinafter referred to as F-85) was used as the organic medium.

In the following explanation, F-85 will be used as an example, but the present invention is not limited to F-85 as an organic medium.

In FIG. 1, 1 is a boiler installed in the high temperature part of the heat source, which is a normal water cycle boiler, and 2 is a boiler installed in the low temperature part of the heat source, which is an F-85 boiler. Steam generated in the water boiler 1 is guided to the turbine 3 via the main steam pipe 14. The steam that has done work in the turbine 3 is led to the condenser 5 through the exhaust pipe 15, where it is converted into condensate. The water passes through the condensate drain and condensate pipe 16, is pressurized by the condensate pump 6, and is led to the water supply (3) water heater 7. This feed water heater 7 is F-85
The heating source is 1.11 steam from the turbine.

The condensate wetted by the feed water heater 7 is led to the deaerator 8 through the condensate pipe 16. Bleed air from the turbine 3 flows into the deaerator 8 through a bleed pipe 23 as heating steam for heating condensate. The condensate heated and degassed in the deaerator 8 becomes feed water, which is sealed under pressure by the water feed pump 9 and circulated to the boiler 1 via the water feed pipe 17. The above is the water cycle.

F-85 steam produced by the F-85 boiler 2 is guided to the l-1-85 turbine 10 through the main steam pipe 18. F
The F-85 steam that worked in -85 turbine 10 is F-8
5 is led to the feed water heater 7 through the turbine exhaust pipe 19,
Heating the condensate of the water cycle. The F-85 exhaust steam from which heat has been removed by the feedwater heater is led to the condenser 12 through the steam pipe 20 and condensed. The condensate passes through the condensate pipe 21 and the liquid supply pipe 22, is pressurized by the condensate and liquid supply pump 13, and is then transferred to F-8.
5 Circulate to boiler 2. The above is the F-85 cycle.

(4) Since the present invention combines the above-mentioned two-fluid cycle, the high-temperature part and the low-temperature part of the heat source can be divided into the most appropriate usage conditions. In other words, the water boiler 1 installed in the high-temperature part of the heat source can adopt steam conditions that match the temperature of the heat source, and there is no need to consider heat recovery in the low-temperature part of the heat source. of steam, increasing cycle efficiency.

Normally, if steam conditions of 30 atg and 350° C. or higher are adopted, the thermal efficiency will be higher than that of the F-85 cycle.

On the other hand, the F-85 boiler 2 is a boiler installed at a low heat source, and is designed to sufficiently recover heat from the low temperature portion of the heat source under the maximum usage conditions determined from the characteristics of F-85.

F-85 is trifluoroethanol (CFsCH20
It is an organic medium whose main component is H), which can generate high-pressure steam in the medium to low temperature range compared to other media such as chlorofluorocarbons, and has a small latent heat of vaporization, so the medium temperature can be adjusted to the heat source temperature drop curve. Since they can be placed close to each other and the temperature of the heat source can be significantly lowered, high power recovery is possible.

The maximum operating conditions for I'-85 are 50atg and 300℃, and for practical use, with a margin of 49atg.
, up to 283°C.

F-85 cycle 1. For example, if the condensate temperature is 30℃, this is 1. In the -85 cycle, the degree of vacuum is quite deep. Although it is a temporary value, the turbine exhaust The pressure is 0.126 ata.The main steam condition is 48a.
ta, 283℃ (2 If the turbine efficiency is 85chi, then from the characteristics of the turbine output "l:i I" -85, the turbine exhaust is not in the humid region and is in the overheating region, and the temperature is 7.
6℃, enthalpy 140K cag/kl! remains. This exhaust temperature of 76° C. has the ability to sufficiently transfer heat to the condensate of the water cycle. For example, the condensate temperature of water cycle is also 30℃ (saturation pressure 0.043 at
a), sufficient heat transfer is possible.

Since the F-85 liquid has a higher specific gravity than water, the F-85 turbine exhaust is planned to be dry steam in order to prevent erosion of the turbine node. Due to the characteristics of F-85, the turbine exhaust becomes completely superheated steam at normal exhaust pressure (Q, 1 ata or more), which is completely different from the water Rankine cycle.

As mentioned above, the F-85 cycle can effectively recover the amount of heat used for condensate heating in the water cycle, and the amount of heat discarded to the cooling water in the condenser is reduced, so it is possible to increase the cycle thermal efficiency of the entire two-fluid cycle. can.

Therefore, the volume of F-85 after turbine expansion is significantly smaller than that of water, and even after expansion it is still in the overheating region.
It is possible to downsize the turbine, and it is also highly safe and reliable.

In FIG. 1, the turbines and generators for the water cycle and the F-85 cycle are shown separately, but the steam turbine 3 and the F-85 turbine 10 are combined, and the generators 4 and 11 are It is of course possible to put them together on a stand, which is advantageous in terms of space.

Since the present invention is configured as described above, the high temperature part of the heat source is recovered by the highly efficient water Rankine cycle (7), the heat source heat is recovered to a sufficiently low temperature by the organic medium cycle, and both cycles are combined. , a large energy saving effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an embodiment of the two-fluid cycle of the present invention. 1...High temperature side boiler, 2...Low temperature side boiler, 3...
・Steam turbine, 4--generator, 5--condenser, 6-
... Condensate pump, 7... Feed water heater, 8... Deaerator, 9... Water feed pump, 10... F-85 turbine,
11... Generator, 12... Condenser, 13... Condenser/liquid supply tank 19.20... F-85 exhaust pipe, 21-...
・Recovery liquid pipe, 22...Liquid supply pipe, 23...Deaerator heating steam pipe-7? 1 8) (

Claims (1)

[Claims] ■ A two-fluid system characterized in that the high-temperature part of the heat source is treated with a water Rankine cycle, the low-temperature part of the heat source is treated with an organic medium Rankine cycle, and the feed water of the water cycle is heated by the turbine exhaust of the organic medium cycle. cycle.