JPS6365818B2 - - Google Patents

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 repeated rises in oil prices, there has been a demand for energy conservation in various fields, and diesel engines that use heavy oil as fuel are no exception, and various efforts are being made to improve their efficiency. As improvements are being made, 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 devices, as in the latter case,
This is highly effective in eliminating excess energy waste and reducing energy consumption.

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, no method has yet been proposed that can efficiently recover and reuse waste heat in medium to low temperature ranges, and it is necessary to take some measures. ing.

To briefly explain this using a conventional example shown in FIG. 1, reference numeral 1 in the figure indicates a diesel engine,
are the intake and exhaust pipes respectively, and an exhaust turbine type supercharger 4 is installed astride these intake and exhaust pipes 2 and 3.
is provided. The supercharger 4 is used to pressurize the intake air in the intake pipe 2 using the exhaust gas in the exhaust pipe 3, so that 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 thermal energy by introducing exhaust gas that has passed through the supercharger 4. Inside this boiler 5, an exhaust heat recovery cycle system 6 is installed.
An evaporating section 7 and a water supply preheating section 8 are provided. The water supplied from the water tank 9 by the water pump 10 in the evaporator 7 and the water supply preheating section 8 recovers the thermal energy of the exhaust gas and evaporates in sequence. It is separated in a steam separator 11 provided on the downstream side of 8 and taken out as steam. This 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 for heating a fuel oil storage tank 13 and the like. This 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 water and steam are separated. In addition, 15 in the figure is a cooling water circulation path that cools each part of the diesel engine 1, and a cooler 15a that cools the cooling water heated by seawater or the like.
and a pump 15b for circulation.

By the way, as mentioned above, in the case of the diesel engine 1 using the supercharger 4, the intake air flowing through the intake pipe 2 is adiabatically compressed by the supercharger 4, which generates heat, and the temperature is about 160°C. It was something that would rise to . If this continues, the volume of air will increase too much and the density of the intake air will decrease.
Conventionally, an air cooler 16 is provided in the middle of the intake pipe 2 to lower the air temperature to about 60° C. so that a desired engine output can 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 its improvement is required from the viewpoint of energy saving.

In addition, in the above 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. There is a need to diversify energy when it comes to reusing energy.

However, on the other hand, it should be noted that due to the oxidation of the sulfur (S) contained in the exhaust gas, sulfuric anhydride (SO ₃ ) combines with moisture and becomes sulfuric acid (H ₂ SO ₄ ), which is released into boilers 5, etc. To prevent condensation on the heat transfer tube walls, the temperature of the tube walls should be adjusted to the acid dew point (approximately
temperature (135℃) or higher. In other words, if the condensation of SO ₃ as mentioned above adheres to the tube wall of the heat exchanger tube of the boiler 5, that part will corrode and be damaged, so it is necessary to take this point into consideration. ing.

[Summary of the invention]

The present invention has been made in view of these circumstances, and includes a preheater connected to a return condensation waterway of an exhaust heat recovery cycle system on the downstream side of the supercharger in the intake pipe of a diesel engine. The boiler is connected to the inlet side of the high temperature heating section of the waste heat recovery boiler via the low temperature heating section, and the return condensed water bypass path branched from the upstream side of the preheater is connected to the inlet of the high temperature heating section of the boiler. With a simple structure that connects to the side and provides a flash tank on the outlet side of this high-temperature heating section, the thermal energy of the intake air, which was previously wasted, can be efficiently recovered and reused. At the same time, it is possible to maintain the temperature on the boiler heat exchanger tube wall above the acid dew point of SO ₃ minutes, preventing corrosion, and improving the recovery efficiency in the boiler. The present invention provides an exhaust heat recovery device for a diesel engine that makes it possible to obtain hot water and diversify its reuse.

〔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, and in the figure, the same or corresponding parts as in Fig. 1 are given the same numbers and their explanations are omitted. .

Now, according to the present invention, the preheater 20 constituting the exhaust heat recovery cycle system 6 is provided downstream of the supercharger 4 in the engine intake pipe 2, and the heat utilization equipment 1 is connected to the preheater 20.
2 (12A, 12B, 12C) 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. The structure is designed so that it can be reused. The preheater 20 is connected to the low temperature heating section 19 of the boiler 5 via the circulation path 22, and the outlet side of the low temperature heating section 19 is connected to the inlet side of the high temperature heating section 18. The system is configured to heat the hot water preheated by the exhaust gas to raise its temperature. Further, the circulation path 2 on the upstream side of the preheater 20
1, a bypass passage 23 is branched in the middle, through which a portion of the return condensed water is guided, and this bypass passage 23 is connected to the inlet side of the high-temperature heating section 18 of the boiler 5. Therefore, according to such a configuration, the return condensed water in the circulation path 21 is heated by the preheater 20 and the low-temperature heating section 19 of the boiler 5, and is guided through the bypass path 23. These are combined at the inlet side of the high-temperature heating section 18 of the boiler 5, introduced into the boiler 5, and heated by the exhaust gas.

The reason for adopting this 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 SO contained in the exhaust gas, and to prevent dew condensation on the tube wall. This is to prevent corrosion. That is, the heat utilization equipment 12 (12A, 12
When the temperature of the return condensed water from (B, 12C) is about 70°C and 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 19 of the boiler 5 will rise to the above level. The acid dew point may drop below the specified acid dew point. For this reason, the present invention adjusts the amount of supply to the preheater 20 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°C) is merged with the high-temperature water (approximately 163°C) heated in the low-temperature heating section 19 of the boiler 5 to bring the overall temperature to approximately 140°C, which is above the acid dew point. It is configured to be introduced into the boiler 5.

The intake air temperature in the intake pipe 2 can be reduced from about 160°C to about 85°C by providing the preheater 20.
℃, and even if this is cooled down to the engine introduction temperature of approximately 60℃ using the air cooler 16, the amount of heat discarded is small, resulting in energy savings.
Moreover, since the load on the air cooler 16 is small, it also has the advantage of being able to be made smaller. 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 improves the efficiency of exhaust heat recovery 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 converted into two types of low-pressure steam and heated water of about 120°C using the multi-stage flush tank 24 (two stages in this embodiment). generate hot water,
These steam and hot water are used in various heat utilization equipment 1
2, etc., in order to make it reusable and diversify its use. 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 diagram, hot water can be used for heating, cooling, and space heating of fuel oil storage tanks, and by using such 120°C hot water, the overall system efficiency can be greatly increased. improves.

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, and 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 flusher tank is installed on the outlet side of this high-temperature heating section so that steam and hot water can be obtained, so despite the simple configuration, the thermal energy of the intake air, which was previously wasted, can be efficiently recovered. In addition to making effective use of SO, it is possible to maintain the temperature at the boiler heat exchanger tube wall above the acid dew point of SO ₃ minutes, preventing corrosion, and improving the recovery efficiency in the boiler. In addition, there are various excellent effects such as being able to diversify the reuse of thermal energy from the steam and hot water obtained in the flasher tank.

[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... Suction and exhaust pipes, 4... Supercharger, 5... Exhaust heat recovery boiler, 6...
...Exhaust heat recovery cycle system, 12 (12A, 12B,
12C) ... heat utilization equipment, 13 ... fuel oil storage tank, 16 ... air cooler, 18 ... high temperature heating section, 19 ... low temperature heating section, 20 ... preheater,
21, 22...Circulation path, 23...Bypass path, 2
4...Flush tank.

Claims (1)

[Claims] 1 An exhaust heat recovery boiler that has 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 outlet side of the high-temperature heating section of the boiler to obtain steam and hot water and supply them to 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.