JPS5820913A - Recovery plant of waste heat - Google Patents

Abstract

PURPOSE:To keep output constant always and to maintain waste heat recovery efficiency favourably, by installing a heat accumulator upstream exhaust gas of a vaporizer, in a waste heat recovery plant wherein a low boiling point medium is heated and vaporized by waste heat gas. CONSTITUTION:A low boiling point medium is boiled and evaporated by a vaporizer 1 through a preheater 2, power is recovered by a turbine 3 and the medium is returned to the preheater 2 through condenser 5 and a medium pump 6. Exhaust gas is supplied to a heat accumulator 20 and is led to the vaporizer 1 and the preheater 2. A heat accumulating material having a melting point at about indentical temperature with that for a rated design exhaust gas is applied to the heat accumulator 20. The heat accumulator 20 absorbs variation of a temperature of the exhaust gas instantaneously for adjustment to a fixed temperature, then output can be kept constant always. Waste heat recovery efficiency can be made favourable in this manner.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a waste heat recovery power generation plant, and in particular provides a waste heat recovery power generation plant with good waste heat recovery power generation efficiency, taking into account fluctuations in waste gas temperature.

BACKGROUND OF THE INVENTION Since it is predicted that oil resources will soon be depleted, various methods have been attempted to utilize energy effectively.

For example, devices have been proposed for recovering electrical power from waste heat of mining and industrial production systems (hereinafter referred to as production systems). Figure 1 shows the system of a conventional waste heat recovery power generation plant, where 1 is an evaporator, 2 is a preheater, 3 is a turbine, 4 is a generator, 5 is a condenser, and 6 is a medium. It's a pump. Water-steam can be used as the working medium in such waste heat recovery plants if the waste gas temperature is high enough, but usually water-steam is used as the working medium in the production system, which is the waste gas source. Since the temperature has decreased to , from the viewpoint of waste heat recovery power generation efficiency, trichlorotrifluoroethane is supplied to the evaporator 1, and the waste gas after heat exchange is further led to the preheater 2 through the exhaust gas cylinder 12. The medium is preheated in the preheater 2 to near the saturation temperature of its supply pressure, and further boiled and evaporated in the evaporator 1. The generated medium steam is supplied to the turbine 3 to recover power and return to the condenser 5, medium pump 6, and preheater 2, forming a closed cycle.

Such conventional waste heat recovery power generation plants have the disadvantage that the efficiency of waste heat recovery and power generation is low when the temperature of the waste gas fluctuates. In other words, when designing a waste heat recovery power generation plant, the design heat source temperature is compared with the waste gas conditions of the production system and set to approximately the average temperature. Temperature fluctuates constantly. In this way, the operating status of the conventional plant when the exhaust gas temperature fluctuates,
Shown in Figure 2. The waste gas filling degree T is shown as a solid line and the rated design waste gas temperature T is shown as a broken line. When the amount exceeds 100, a part of the waste gas is discharged to the outside by adjusting the damper 15 of the waste gas cylinder 11 and the bypass damper 16 of the bypass discharge cylinder 14. The amount of evaporation of the medium is adjusted by reducing the amount of waste gas supplied to the rated output, which is shown by the solid line and the rated output shown by the dashed line. I'm holding it down.

As described above, in conventional heat generating plants, when the temperature of the waste gas rises above the rated design waste gas temperature, the waste gas is discharged without utilizing effective thermal energy. Note that the waste gas depth T is the rated design waste gas depth T.

If it falls below, the amount of medium evaporation in the evaporator 1 will decrease and the power generation output will also be less than the rated output. It is natural that it will drop below.

An object of the present invention is to provide a waste heat recovery plant that effectively utilizes high-temperature energy and maintains good waste heat recovery efficiency even when the waste gas filling level changes.

A feature of the present invention is that when the exhaust gas temperature rises above the rated design exhaust gas temperature, a heat storage device is installed to store the thermal energy of the temperature change, and when the waste gas temperature decreases, the heat storage device is installed. The stored heat is released to heat the waste gas to the rated design gas filling temperature, and the temperature is adjusted to the rated design waste gas temperature.
This is a waste heat recovery plant that increases power generation output by making it possible to obtain approximately the rated power generation output at all times.

A waste heat recovery power generation plant that is an embodiment of the present invention is shown in FIGS. 3 and 4, and the effects of the above embodiment are shown in FIGS.
This will be explained with reference to FIG. FIG. 3 shows a system of a waste heat recovery power generation plant in which the present invention is implemented. In FIG. 3, components that are the same as those of the prior art are designated by the same numbers as in FIG. 1, and 20 is a heat storage device. The waste gas is first supplied to the heat storage device and then led to the evaporator 1 and preheater 2.

An example of the structure of the heat storage device 20 is shown in FIG. The length of the heat storage device consists of a duct 21 and a heat storage body 22, and the heat storage body 22 is composed of a container 23 and a heat storage material 24 filled therein, and a space 25 is provided to absorb volume changes of the heat storage material 24. Heat storage material 24 KMzNaOH-KOH (41-59
W%, melting point 158°, latent heat of fusion 37.3 kaa7/
kg), AtC1,-KCl-LiC/=(63,0
-35,3-1,7W%, melting point 249C, latent heat of fusion 59
．． 5kcat/kg), KCt-L i c4 (41
,5-s s, smoz%, melting point 325C1 latent heat of fusion 5
7.25 kcat/kg), etc., which utilizes the latent heat of fusion associated with a solid-liquid phase change, a material with a temperature K11 that is approximately equal to the rated design exhaust gas temperature is used.

In this plant as well, the operating method of the power plant main body, such as the preheater 2, evaporator 1, and turbine 3, is the same as that of the conventional plant. The functions and effects of the embodiments of the present invention appear when the temperature T of the waste gas 10 fluctuates due to changes in the production status of the production system' which is the heat source. That is, FIG. 5 shows the operating state of the waste heat recovery plant according to the embodiment of the present invention.

That is, the temperature T1 of the waste gas entering the heat storage device 20 is guided to the heat storage device 20.
When the waste gas mixture becomes equal to or higher than the rated design waste gas mixture T0, the waste gas gives heat to the heat storage material 24 while passing through the heat storage device, so the temperature of the gas exiting from the heat storage device T after passing through the heat storage device 20 is almost equal to the heat storage temperature. The material is lowered to its melting point and then supplied to the evaporator 1. on the other hand,
When the heat storage inlet waste gas temperature T1 falls below the rated design waste gas temperature T0, while the waste gas 10 passes through the heat storage device telegram, it absorbs heat and is heated to almost the melting point of the heat storage material 24, The outlet gas temperature T2 is led to the evaporator. As explained above, the heat storage material 24 has a rated design gas temperature T. Because it uses a substance with a melting point close to
Due to the large latent heat of fusion, the temperature of the folding gas flowing down the heat storage device 20 and guided to the evaporator 1 can be kept constant at almost the same temperature as the melting point of the heat storage material (i.e., the rated design gas temperature). The power generation output cam always outputs the rated output.

It can be operated under the rated design condition. That is, in the present invention, the thermal energy of the high-water content waste gas can be transferred to the low-water content waste gas and used effectively. Therefore, the fifth
In the power generation output diagram shown in the figure, the diagonal lines represent the magnitude at which reduction in power generation output is prevented by this embodiment.

Next, the effect of one embodiment of the present invention was confirmed by calculation. As a comparison confirmation method, first, the rated design exhaust gas temperature is 250r,
Waste gas amount: 4 soooo Nm"/h1 Using the above trichlorotrifluoroethane as the heat recovery medium, medium evaporation pressure: 10.4 kg/cm", evaporator pinch point) 24C, medium condensing pressure: 083 kg/cm" Turbine internal efficiency Design a waste heat recovery plant by setting conditions such as 0.7, and calculate the power generation output per cycle of waste gas fluctuation of the conventional plant and the plant implementing the present invention when the waste gas temperature fluctuates in a sin shape at ±30C. Calculated and compared.

According to the design conditions, a waste heat recovery power generation plant with a rated power output of about 3000 kW is designed. When the exhaust gas temperature fluctuates in a sinusoidal manner with a width of ±300 in a one-hour cycle, the power generation output for one cycle, that is, for one hour, is approximately 25,318 kW-h in the conventional plant. In a plant in which the present invention is implemented, the heat storage material has a melting point of 249C, which is close to the rated design waste gas temperature of 250C.
g, the power generation output per cycle or hour is approximately 2997 kW-h, which is approximately 1 kW-h compared to the conventional method.
An 8.4% increase in power generation output is expected.

The rate of increase t'i varies depending on the fluctuation range of the exhaust gas temperature, and the calculation results are shown in FIG. In Fig. 6, the power generation output according to the present invention is shown by a solid line, and the power generation output L' of the conventional example is shown by a broken line.

Further, the output increase rate compared to the conventional example is shown as ΔL. According to FIG. 6, when the exhaust gas temperature fluctuates by ±30c, ±4Or, and ±50r with respect to the rated design gas temperature of 250r, the fluctuations are approximately 18%, 23%, and 23%, respectively, compared to the conventional design.
A 29% increase in power generation is expected.

As described above, according to the embodiments of the present invention, fluctuations in waste gas temperature caused by changes in the production status of the production system are immediately absorbed and adjusted to a constant temperature, and waste gas at high temperature, which was conventionally discarded, is removed. It is possible to provide a single heat recovery power generation plant that can increase power generation output by using thermal energy and has good waste heat recovery power generation efficiency. Moreover, the present invention is an extremely easy-to-implement invention that has no moving parts in the heat storage section, does not require a control system, and can achieve its purpose simply by installing the heat storage device. Furthermore, the damper, its control device, etc., which conventionally controlled the amount of waste gas depending on the temperature of the waste gas, become unnecessary. In order to explain the effects of the embodiments of the present invention, trial calculations were made using trichlorotrifluoroethane as a medium and htct, -KCt-t, and ict as heat storage materials. However, the present invention may be applied to other low boiling point media and other heat storage materials depending on the exhaust gas filling level.

Further, in this embodiment, a case has been described in which the heat storage material utilizes the latent heat of fusion of a substance, but it is a thermal theory that the heat storage material may also utilize the sensible heat of oil, concrete, brick, etc. Further, in the trial calculation of the effects of the embodiment of the present invention shown in FIG. 6, the fluctuating gas temperature cycle was set to one hour, but the effects of the invention are the same even if other time lengths are used. In this case,
It is necessary to set the heat storage capacity of the heat storage device to an amount commensurate with the cycle time and the θ temperature fluctuation range. □ According to the present invention, it is possible to provide a waste heat recovery plant with excellent waste heat recovery efficiency that can always maintain a constant output even if the waste gas temperature varies by 1111iE.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a conventional waste heat recovery power generation plant, Figure 2 is a diagram of the operating state of the conventional plant when the waste gas temperature fluctuates, and Figure 3 is a waste heat recovery power generation plant that is an embodiment of the present invention. 4 is a structural diagram of the heat storage device installed in the waste heat recovery power generation plant shown in FIG. The operating state diagram, FIG. 6, is an explanatory diagram showing the effects of the embodiment of the present invention in comparison with the conventional example. 1... Evaporator, 2... Preheater, 3... Turbine,
4... Generator, 5... Condenser, 6... Medium pump, 10... Waste gas, 11, 12.13... Waste gas cylinder, 14... Bypass waste dregs D1.15 ... Damper, 16... Pie pasta 7 par, 20. ,,thermal storage device,
21...Duct, 22...Heat storage body, 23...Container, 24...Heat storage material, 25...Space - Agent Patent attorney Akio Takaki 1 Figure 1 Figure 2 Stopper Ka-Gin r4 (season figure 6

Claims (1)

[Claims] 1. A preheater that uses a low boiling point medium and heats the medium to approximately the saturation temperature of the supply pressure, an evaporator that vaporizes the medium, a turbine driven by the low boiling point medium, and a medium vapor A condenser that cools and liquefies the medium and a medium pump that supplies the condensed medium to a preheater are installed, and the low boiling point medium is heated and evaporated by the preheater and evaporator using waste heat gas as a heat source, and the generated steam drives the turbine. In a waste heat recovery plant that recovers power from waste heat, a heat storage device using a heat storage material that utilizes the heat capacity of substances is installed upstream of the waste gas of the evaporator, and the waste gas is evaporated through the heat storage device. This is a waste heat recovery plant that is characterized by circulating heat in the order of heat exchanger and preheater. 2. As the heat storage material, a solid-liquid phase change substance having a melting point near the average temperature of the waste gas is used, and heat is stored by its latent heat of fusion.
Waste heat recovery plant described in Section.