JPH0231764B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a power generation device that uses exhaust gas from an internal combustion engine to improve the thermal efficiency of primary energy.

(Conventional technology) As the price of crude oil rises, energy alternatives to petroleum are being actively developed. At the same time, improvements in the thermal efficiency of conventional power generation systems are also being considered. is being done. Even if these high-efficiency power generation devices utilize exhaust heat to the maximum extent possible, the thermal efficiency is limited to about 80-85%, and the temperature of the exhaust gas finally released into the atmosphere is a medium temperature of about 150 degrees Celsius. is not used.

Figure 1 shows an example of a combined heat and power generation device that has recently been put into practical use. That is, a generator 2 directly connected to an internal combustion engine 1 such as a diesel engine, a gas turbine, or a gas engine supplies the required electric power 2a, and the cooling water of the internal combustion engine 1, which was previously wasted, is transferred to the heat exchanger 3. At the same time, the exhaust gas of about 500°C from the internal combustion engine 1 is introduced into an absorption type water cooler/heater 4, and the thermal energy of the exhaust gas is utilized. It produces cold and hot water and uses it for air conditioning and heating 4a. This combined heat and power generation device is more efficient than generating electricity and thermal energy separately when electrical loads and thermal loads are required at the same time, such as in offices, buildings, department stores, hospitals, and residences, with a thermal efficiency of 80%. ~85%, making a large contribution to energy conservation.

(Problems to be Solved by the Invention) However, the absorption type water cooler/heater 4 can only use the thermal energy of the exhaust gas of the internal combustion engine 1 in the range of 500-150°C. In other words, in order to reduce the exhaust gas emission temperature to 150°C or less, the absorption type water cooler/heater 4 must be made larger, which is also disadvantageous in terms of cost, so it can only be used within the above-mentioned temperature range. , Normally, medium-temperature heat below 250°C and above 100°C is discarded because it is unused.

The purpose of the present invention is to improve the efficiency of the entire system by effectively utilizing medium-temperature waste heat in the exhaust gas of an internal combustion engine and using the cooling water of the internal combustion engine as a low-temperature heat source without increasing the size of equipment. The purpose of the present invention is to provide a power generation device designed to save energy.

[Structure of the invention]

(Means for Solving the Problems) As shown in FIG. 2, the power generation device according to the present invention includes an evaporator 6 that preheats and evaporates a working medium under constant pressure, and an evaporator 6 that preheats and evaporates a working medium. A turbine 8 driven by the adiabatic expansion energy of a working medium, a condenser 5 that cools and liquefies the working medium that drove the turbine 8 under equal pressure by a low-temperature heat source 3b, and a condenser 5 that liquefies the liquefied working medium into the evaporator 6. The turbine 8 drives a generator 9, and the evaporator 6 is fed with medium-temperature exhaust gas from the internal combustion engine that has been recovered at high temperature. Introduced as a heat source 4b, the working medium is preheated and evaporated by the gas heat, and
The condenser 5 is provided downstream of the heat exchanger 3 in the cooling water circulation system of the internal combustion engine 1, as shown in FIG. The low temperature heat source 3b in
It is characterized by being used as

(Function) In the present invention, after recovering high-temperature gas, which is relatively easy to recover, from the exhaust gas of an internal combustion engine, the intermediate-temperature exhaust gas is directly used as a heat source for the evaporator in the Rankine cycle. The medium temperature of the exhaust gas can be used without Additionally, the condenser in the Rankine cycle requires a large amount of low-temperature heat source, but since it uses the circulating cooling water of the internal combustion engine, there is no need to prepare a separate low-temperature heat source, which also contributes greatly to energy savings. .

As mentioned above, the present invention attempts to generate electricity by utilizing the temperature difference between the heat of medium-temperature exhaust gas of an internal combustion engine and the cooling water, and uses a closed cycle system as shown in Figs. 2 and 3. Make use of it. This closed cycle system uses a working medium such as ammonia, R-22, etc.

The operation of this system will be explained with reference to FIG.
In the evaporator 6, heat is taken in from the medium-temperature exhaust gas 4b, and the working medium is preheated 11 (point D in Fig. 3) and evaporated 12 under constant pressure, and the working medium vaporized at point A is transferred to the turbine. 8 and turbine 8
Adiabatic expansion 13 occurs inside the . This turbine 8
The energy of the adiabatic expansion 13 inside the turbine rotates an impeller (not shown) of the turbine 8, and drives the generator 9 via the shaft 8a. The working medium that has undergone adiabatic expansion 13 in the turbine 8 is cooled from point B to point C in the condenser 5 under equal pressure by the low-temperature heat source 3b, and is condensed 14 and liquefied. At point C the medium has liquefied. This liquefied medium is adiabatically pressurized 15 to point E by the pump 7 and returned to the evaporator 6 to form a Rankine cycle.

(Example) Next, a fourth example of the present invention using the closed cycle system based on the Rankine cycle will be described.
This will be explained using figures. Approximately 500℃ exhaust gas 1a from internal combustion engine 1 is used as a medium-temperature heat source (exhaust gas) at approximately 150℃ after a part of the thermal energy is utilized in absorption type water cooler/heater 4.
4b, which is introduced into the evaporator 6 and then released into the atmosphere. On the other hand, the cooling water 1b of the internal combustion engine 1 is approximately
Although the temperature is about 80°C, heat is exchanged with a heat exchanger 3 for hot water supply, etc., and it becomes a low-temperature heat source 3b of about 65°C. This low-temperature heat source 3b is supplied to the condenser 5 by a pump 10, absorbs condensation heat there, and is then circulated and used for cooling the internal combustion engine 1. That is, in a closed cycle system, the temperature of the medium temperature heat source 4b which is exhaust gas is 150°C, and the low temperature heat source 3b which is cooling water.
A Rankine cycle is performed due to the temperature difference of 65° C., the working medium operates the turbine 8, and the temperature difference energy is converted into electrical energy by the generator 9. The generators 2 and 9 are operated in parallel by a device not shown.

Note that the cooling water 3 has passed through the condenser 5.
The temperature of c will rise slightly above 65℃, or internal combustion engine 1
This does not pose any particular problem when driving.

In this way, in the system shown in Fig. 4, since the cooling water of the internal combustion engine 1 is used as the low-temperature heat source 3b, there is no need to supply it from the outside, and the existing cooling water circulation system can be applied as is, which improves the effective use of equipment. It is effective and saves energy.

The exhaust gas 4c after passing through the evaporator 6 has a temperature of approximately 80℃
It is also possible to use it more effectively. In this case, as shown in FIG.
A heat source of about 80°C emitted from the heat source is introduced into another Rankine cycle evaporator 6a, and water at a temperature lower than this heat source, for example, 20 to 30°C, is introduced into the condenser 5a by a pump 10.
supplied by a. As a result, further exhaust heat can be recovered by the turbine 8b and the generator 9a.

In other words, in conventional power generation equipment that uses an internal combustion engine, approximately 35% of the primary energy is converted into electricity, but the remaining 65% is wasted, but as mentioned above, waste heat can be used effectively. By doing so, it can greatly contribute to saving primary energy.

[Effects of the Invention] As described above, according to the present invention, exhaust gas heat from an internal combustion engine can be used up to a medium temperature range without the need to increase the size of equipment, and it can also be used for circulation in the condenser. Since the cooling water of the internal combustion engine is used, there is no need to provide a separate low-temperature heat source, which improves the thermal efficiency of the entire system and greatly contributes to energy savings.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a general power/heat cogeneration system using an internal combustion engine, Fig. 2 is a flow diagram illustrating the concept of a power generation system using a temperature difference according to the present invention, and Fig. FIG. 2 is a curve diagram for explaining, FIG. 4 is a block explanatory diagram showing one embodiment of the present invention, and FIG. 5 is a block explanatory diagram showing another embodiment of the present invention. 1... Internal combustion engine, 2... Generator, 3... Heat exchanger, 3b... Low temperature heat source, 4b... Medium temperature exhaust gas,
5... Condenser, 6... Evaporator, 7... Pump, 8
...turbine, 9...generator.

Claims (1)

[Scope of Claims] 1. An evaporator that preheats and evaporates a working medium under constant pressure, a turbine that is driven by the adiabatic expansion energy of the vaporized working medium that is evaporated by the evaporator, and an operation that drives this turbine. A closed loop system based on the Rankine cycle is configured by a condenser that cools and liquefies the medium under constant pressure using a low-temperature heat source and a pump that pumps the liquefied working medium to the evaporator, and the turbine drives the generator. In the power generation device, the exhaust gas of the internal combustion engine that has been recovered at high temperature and has become intermediate temperature is introduced into the evaporator, and the working medium is preheated and evaporated by the heat of the gas, and the condenser is connected to the cooling water circulation of the internal combustion engine. 1. A power generating apparatus, characterized in that the power generating apparatus is provided at a downstream side of a heat exchanger in the system, and uses cooling water whose temperature has been reduced by recovering heat by the heat exchanger as the low-temperature heat source in the condenser.