JPS60132055A - Waste-heat recovering apparatus for diesel engine - Google Patents

Abstract

PURPOSE:To efficiently recover waste heat by installing a preheater for heating condensed water on the downstream side of a supercharger installed into an air feeding pipe and branching a bypass passage from the upstream side of the preheater and connecting said bypass passage to the inlet side of the high- temperature heating part of a discharged-gas boiler. CONSTITUTION:A preheater 20 which constitutes a waste-heat recovery cycle system 6 is installed onto the downstream side of a supercharger 4 installed into an intake pipe 2. A circulation passage 21 for the condensed-water returned from the heat utilizing equipment 12 and a fuel-oil storage tank 13 is connected to the preheater 20, and the thermal energy of the inhaled air is recovered. The preheater 20 is connected to the low-temperature heating part 19 of a boiler 5 through a circulation passage 22. A bypass passage 23 is installed into the circulation passage 21 on the upstream side of the preheater 20, and the bypass passage 23 is connected to the inlet side of a high-temperature heating part 18, and the boiler inlet side is kept at the temperature over the acid dew point of SO3 portion by adjusting the bypass amount. The hot water obtained in the boiler 5 is converted to low-pressure steam and hot water in a multistage flasher tank 24 and utilized in the equipment 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an exhaust heat recovery device for a diesel engine used, for example, as a marine engine.

[Prior art]

In recent years, due to the sudden rise in the price of oil, there has been a push to save energy in all areas, and diesel engines that use heavy oil as fuel are no exception, and various improvements are being made to make them more efficient. In line with this, there is a desire to efficiently recover and reuse the thermal energy of exhaust gas, which was previously wasted. In particular, recovering waste heat and using it as an energy source for other equipment and equipment, as in the latter case, has a great effect in reducing unnecessary energy waste. be.

Various proposals have been made for this type of waste heat recovery device that recovers and reuses waste heat in a relatively high temperature range, but there is still room for improvement in terms of efficiency. Furthermore, there is no proposal yet that can efficiently recover and reuse waste heat in medium and low temperature ranges, and it is necessary to take some measures. has been done.

This can be briefly explained using the conventional example shown in Fig. 1.
In the figure, reference numeral 1 is a diesel engine, 2 and 3 are its intake and exhaust pipes, respectively, and an exhaust turbine type supercharger 4 is provided astride these intake and exhaust pipes 2 and 3. The supercharger 4 is used to pressurize the intake air in the intake pipe 2 using the exhaust gas in the exhaust pipe 3, and a part of the thermal energy of the exhaust gas is recovered and used for pressurizing the intake air.

Reference numeral 5 denotes an exhaust heat recovery boiler that recovers heat energy by introducing exhaust gas that has passed through the supercharger 4. Inside this boiler 5, there are an evaporation section T constituting an exhaust heat recovery cycle system 6;
A water heating section is provided. Then, in the evaporation section T and the water supply preheating section 8, the water is transferred from the water tank 9 to the water supply pump 1.
The water supplied as shown in FIG. It is extracted as steam. The extracted steam is used as an energy source for a heat utilization device 12 such as a steam turbine that drives a generator, and a portion of it is also used to heat a fuel oil storage tank 13. The heat-utilized steam is then condensed and returned to the tank 9 as return condensed water, and is again supplied to the boiler 5 side. The steam-water separator 11 is connected to the outlet side of the feed water preheating section 8 of the boiler 5, and the hot water introduced from the feed water preheating section 8 is circulated through a circulation path 14 connected to the evaporation section 7. The water is heated by sequentially flowing through the pump 14a, and steam and water are separated. Also, 1 in the figure
5 is a cooling water circulation path that cools each part of the diesel engine 1, and a cooling water circulation path 215 that cools the cooling water heated by seawater, etc.
a, and a pump 15b for circulation.

By the way, as mentioned above, in the diesel engine 1 using the supercharger 4, the intake air flowing through the intake pipe 2 is adiabatically compressed by the supercharger 4, so it generates heat, and its temperature reaches about 160℃.
The temperature would rise to about ℃. If this continues, the volume of air will increase too much and the density of the intake air will decrease, so an air cooler 16 is installed in the middle of the intake pipe 2 to lower the air temperature to about 60°C to achieve the desired engine temperature. Conventionally, it has been done to enable output to be obtained.

Here, 17 in the figure is a cooling water circulation path of this air cooler 16, and is provided with a pump 17a and a cooler 17b that performs indirect cooling using seawater or the like.

However, in such a configuration, the thermal energy of the pressurized intake air using exhaust gas is simply cooled and disposed of in the air cooler 16, which is not only wasteful but also wasteful. The air cooler 16 also needs to have a certain capacity, and improvements are being sought from the standpoint of energy conservation.

In addition, in the above-described configuration, the temperature of the exhaust gas on the inlet side of the boiler 5 is about 320°C, while the temperature on the outlet side is about 171°C.
℃, and it is desired to further improve the recovery efficiency, and it is also required to diversify the reuse of the recovered thermal energy.

4- However, on the other hand, it should be noted that sulfuric anhydride (S) due to oxidation of sulfur (S) contained in exhaust gas
03) is combined with moisture to form sulfuric acid (H2SO4), and the temperature of the tube wall is kept above the acid dew point (approximately 135° C.) so that dew does not form on the wall of the heat transfer tube of the boiler 5, etc.

In other words, if the 803 minutes of dew condensation mentioned above adheres to the tube wall of the heat exchanger tube of boiler 5, that part will corrode and be damaged, so it is necessary to take these points into consideration. It is said that

[Summary of the invention]

The present invention was made in view of these circumstances, and
The intake pipe of a diesel engine (supercharger) is also equipped with a preheater connected to the return condensation waterway of the exhaust heat recovery cycle system on the downstream side, and this preheater is connected to the high temperature temperature through the low temperature heating section of the exhaust heat recovery boiler. Connected to the inlet side of the heating section, and connected to the inlet side of the high-temperature heating section of the boiler, and connected to the inlet side of the high-temperature heating section of the boiler, and connected to the outlet side of the high-temperature heating section of the boiler. 7 The simple structure of installing a lattice tank allows us to efficiently recover and reuse the heat energy of the intake air, which was previously wasted, and reduce the temperature at the boiler heat exchanger tube wall to the 803 minute acid dew point. It is possible to maintain the above temperature and prevent corrosion, improve the recovery efficiency in the boiler, and furthermore, it is possible to obtain steam and hot water in the Francia tank and diversify its reuse. The present invention provides an exhaust heat recovery device for a sharp diesel engine.

〔Example〕

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

Fig. 2 shows an embodiment of the exhaust heat recovery device for a diesel engine according to the present invention. In the figure, the same or corresponding parts as in Fig. 1 are given the same numbers and their explanations are omitted. do.

Now, according to the present invention, the preheater 20 that intercepts the exhaust heat recovery cycle system 6 is provided downstream of the supercharger 4 in the engine intake pipe 2, and the heat utilization devices 12C12A and 12B are installed in the preheater 20.
, 120) and the return condensed water circulation path 21 from the fuel oil storage tank 13, the thermal energy from the intake air heated by the supercharger 4 can be efficiently recovered and reused. It is structured so that it can be achieved. This preheater 20 is connected to the low temperature heating section 19 of the boiler 5 via a circulation path 22, and this low temperature heating section 19
The outlet side of is connected to the inlet side of the high temperature heating section 1B, and is configured to heat the hot water preheated by the preheater 20 with exhaust gas to raise its temperature. Further, the preheater 20
In the middle of the circulation path 21 on the upstream side of the boiler 5, a bypass path 23 to which a portion of the return condensed water is guided is provided. It is connected. Therefore, according to such a configuration, the return condensed water in the circulation path 21 is transferred to the preheater 20.
The heat heated in the low-temperature heating section 19 of the boiler 5 and the heat guided through the bypass path 23 are combined at the inlet side of the high-temperature heating section 18 of the boiler 5 and introduced into the boiler 5. , will be heated by exhaust gas.

The reason for adopting such a configuration is to maintain the temperature of the heat exchanger tube wall, which is in a particularly low temperature region in the boiler 5, above the acid dew point of 803 minutes contained in the exhaust gas, and to This is to prevent corrosion due to dew condensation.

That is, the heat utilization equipment 12 (12A, 12B, 12C
) and the temperature of the return condensed water is about 70°C, and when the flow rate is large, if the entire amount is passed through the preheater 20, the temperature on the inlet side of the low temperature heating section 190 of the boiler 5 will be below the acid dew point mentioned above. It may become. For this reason, the present invention adjusts the amount of supply to the preheater 2O described above by bypassing a part of it, so that the temperature at the inlet side of the boiler 5 can be maintained at the acid dew point, about 135° C. or higher. At the same time, the bypassed low-temperature water (approximately 70 degrees Celsius) is merged with the high-temperature water (approximately 163 degrees Celsius) heated by the low-temperature heating 81B of boiler 5 to bring the overall temperature to about 140 degrees Celsius, which is above the acid dew point. The system is configured to be introduced within 5.

Note that the temperature of the intake air in the intake pipe 2 is the same as that of the preheater 2.
By providing 0, the temperature is reduced from about 160°C to about 85°C, and even if this temperature is cooled by the air cooler 16 to the 81 engine introduction temperature of about 60°C, the amount of heat disposed of is small, resulting in savings. This is effective for energy conservation, and also has the advantage that the air cooler 16 can be made smaller because the load on it is small. Of course, if the above-mentioned intake air can be reduced to the required temperature by the preheater 20, the air cooler 16 can be omitted. Furthermore, according to this embodiment, when the temperature at the inlet side of the exhaust gas in the boiler 5 is about 320°C, the temperature at the outlet side can be set at about 155°C, which increases the waste heat recovery efficiency compared to the conventional method. It is also possible.

Further, according to the present invention, the hot water of about 233° C. obtained in the boiler 5 described above is transferred to the multi-stage flasher tank 24 (
In this example, two types of low pressure steam and approximately 12
The system generates hot water at a temperature of about 0° C., and allows these steam and hot water to be reused by various types of heat utilization equipment 12, etc., in an effort to diversify them. Examples of the applications of steam include, for example, generating power by turning a turbine or generating electric power through a generator, as well as various other uses. In addition, as shown in the figure, hot water can be used for heating fuel oil storage tanks, cooling, heating, etc.
By also using hot water at 20°C, the overall system efficiency is greatly improved.

It should be noted that the present invention is not limited to the structure of the embodiments described above, and the shape and structure of each part may be modified and changed as appropriate. Also, the present invention is not limited to use in ships as a diesel engine, and can be applied to various types of engines. It is something.

〔Effect of the invention〕

As explained above, according to the exhaust heat recovery device for a diesel engine according to the present invention, a preheater is provided downstream of the supercharger in the intake pipe through which the return condensed water of the exhaust heat recovery cycle flows, and the preheater is While connected to the inlet side of the high temperature heating section of the heat recovery boiler via the low temperature heating section, a bypass path of return condensed water branched from the upstream side of the preheater is also connected to the inlet side of the high temperature heating section, In addition, a 7-lush tank is installed on the outlet side of this high-temperature heating section to obtain steam and hot water, so despite the simple structure, the thermal energy of the intake air, which was previously wasted, can be efficiently recovered. In addition to making effective use of the heat exchanger, the temperature at the boiler heat exchanger tube wall can be reduced by S.
It is possible to maintain the acid dew point above 0.3 minutes to prevent corrosion, improve the recovery efficiency in the original boiler, and reuse the thermal energy in the steam and hot water obtained in the flasher tank. It has various excellent effects, such as being able to diversify the market.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an outline of a conventional device, and FIG. 2 is a system diagram showing an embodiment of the exhaust heat recovery device for a diesel engine according to the present invention. 1...Diesel engine, 2,3...Q suction. Exhaust pipe, 4...Supercharger, 5...Exhaust heat recovery boiler, 6...Exhaust heat recovery cycle system, 12 (12A, 12
B, 12C) ... Heat utilization equipment, 13 ... Fuel oil storage tank, 16 Φ ... Air cooler, 18
...High temperature heating section, 19.....Low temperature heating section, 20.
...Preheater, 21.2211- ...Circulation path, 23...Nokuinokusu path, 24Φ
...flash tank. Patent applicant Ube Industries Co., Ltd. agent Masaki Yamakawa (and one other person) 12-

Claims (1)

[Claims] An exhaust heat recovery boiler that includes a supercharger that pressurizes the intake air in the intake pipe with exhaust gas from a diesel engine, and a high-temperature heating section and a low-temperature heating section that introduce the exhaust gas that has passed through the supercharger and recover its thermal energy. and a flash tank connected to the high-temperature heating section inlet side of the boiler to obtain steam and hot water and supply them to the heat utilization equipment, and the intake pipe downstream of the supercharger has the heat utilization equipment. A preheater for heating return condensed water from the boiler is provided, and this preheater is connected to the inlet side of the high temperature heating section of the boiler via the low temperature heating section, and is branched from the upstream side of the preheater. An exhaust heat recovery device for a diesel engine, characterized in that a bypass path is connected to an inlet side of a high-temperature heating section of the boiler.