JPS6125997B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating furnace exhaust heat recovery device for effectively utilizing the heat retained in the skid cooling water of a heating furnace having a water-cooled skid and the exhaust heat of exhaust gas.

Up until now, skid cooling water for heating furnaces has often been kept at low temperature and low pressure, taking into account the compressive strength, thermal expansion, operation, and maintenance of the skid. FIG. 1 shows an example of a conventional skid cooling water system. The skid cooler 2 of the heating furnace 1 is supplied with cooling water, usually at about 30°C, from the water tank 3 by the pump 4, and the cooling water, which has risen to about 40°C due to the heat absorbed by the skid cooler 2, is sent to the cooler 5. It has a one-cycle cycle in which it is cooled and returned to the water tank 3. In this example, the heat retained in the skid cooling water is discarded, but methods to recover this as steam are already in practical use.
FIG. 2 shows an example.

The cooling water heated by the skid cooler 2 is introduced into the flash tank 6, and the generated steam is passed through the steam pipe 7.
The remaining water is circulated and used as skid cooling water by a pump 4. In this case, the pressure is increased to about 10 kg/cm ² in order to extract and use the steam, so the skid cooler 2 is treated as a boiler and requires an annual government inspection.
During this time, the heating furnace will not be able to operate. Additionally, boiler engineers are required, and maintenance and inspections must be rigorous. When heat is recovered as steam in this way, a major limitation is that the heating furnace is regarded as a boiler.On the other hand, recovering heat from hot water as hot water has the disadvantage that the temperature is low.

In order to eliminate such problems and effectively utilize the heat retained in the skid cooling water, the temperature level of the circulating water is set to the atmospheric pressure saturation temperature of 100°C in Figure 1.
A patent application has already been filed (Japanese Patent Application No. 54-141701, filing date 54-10) to utilize the heat absorbed by the skid cooler for power generation by raising the temperature to a slightly lower temperature, for example, around 98℃.・It is done in 31).

FIG. 3 shows a simple example of this outline. In the figure, reference numeral 21 denotes a low boiling point medium evaporator, and the low boiling point medium is evaporated in the evaporator 21 by the heat retained in the skid cooling water led from the skid cooler 2, and then introduced into the turbine 24. A closed circuit cycle is performed in which the fluid is concentrated in the condenser 25, and then returned to the low boiling point medium evaporator 21 by the pump 27 to be vaporized. However, in the method shown in Figure 3, the amount of heat absorbed by the skid is quite small, so the power generated is also small.
The drawback is that it is difficult to achieve profitability.

The present invention was made to eliminate this drawback in the system shown in FIG. 3, and FIG. 4 shows an arrangement system of one embodiment thereof. In the figure,
The skid cooling water heated by the skid cooler 2 of the heating furnace 1 is preheated by entering the feed water preheater 11 through the pipe 12 that forms a part of the pipe A, and then passes through the pipe 13 that also forms a part of the pipe A. through the exhaust gas hot water heater 10, and the exhaust gas hot water heater 1
The hot water drawn out from the pipe B is introduced into the water supply preheater 11 through a pipe 14 that forms a part of the pipe B, and is taken out from a pipe 15 that also forms a part of the pipe B. If a recuperator 9 is already installed in the exhaust gas duct 8, the exhaust gas hot water heater 10 can be placed downstream of the exhaust gas duct 8 as shown. The exhaust gas contains corrosive substances such as sulfur dioxide gas, so if the water supply temperature is low, the exhaust gas hot water heater 1
Corrosion due to condensation occurs on the surface of the 0 pipe, so it is necessary to maintain the supply water temperature above the minimum temperature to prevent this. Therefore, a water supply temperature detection device 17 is provided in the water supply pipe 13, and the signal is used to operate the flow rate control valve 18 provided in the water supply pipe 12 and the flow rate control valve 19 provided in the bypass pipe 16.
The amount of water supplied to the water supply preheater 11 and the exhaust gas hot water heater 10 is adjusted to maintain the temperature of the water supply at the inlet of the exhaust gas hot water heater at a predetermined value. That is, when the feed water temperature decreases, the flow control valve 18 is throttled and the flow control valve 19 is opened to bypass the feed water and reduce the flow rate of water feed to the exhaust gas hot water heater 10, and conversely, when the feed water temperature becomes excessive, Throttle the flow rate control valve 19,
The flow control valve 18 is opened to increase the amount of water supplied to the exhaust gas hot water heater 10, and the temperature of the inlet water supplied to the exhaust gas hot water heater 10 is maintained at a predetermined value. That is, compared to the conventional method shown in FIG. 3, which makes it possible to raise the temperature level of the cooling water, the method of the present invention makes it possible to recover hot water at an even higher temperature level, and the exhaust gas hot water heater 10 The amount of heat absorbed from the exhaust gas is
Added to the amount of heat absorbed by the skid cooler 2, this total amount of heat can be used for power generation, etc., making it possible to generate a large amount of electricity. This also has the advantage of avoiding corrosion caused by corrosive substances such as gas. In addition, piping 20
is for refluxing or replenishing skid cooling water.

When there is no sulfur dioxide gas in the heating furnace exhaust gas, or when the exhaust gas temperature can be lowered to a level below the skid outlet feed water temperature, the feed water preheater 11 and flow rate control valve 1 are used.
8 and 19 may not be provided.

Next, FIG. 5 and FIG. 6 show an embodiment equipped with a power generation system that utilizes the amount of heat recovered by the method of the present invention.

FIG. 5 shows an example including a power recovery system using a low boiling point medium. After heating the low boiling point medium evaporator 21, the hot water is passed through the pipe 20 by the pump 4'.
After that, it is returned to tank 3. Low boiling point medium vapor is controlled by control valve 2
2, the exhaust gas enters the turbine 24 through expansion work and drives the generator 26, and the exhaust gas becomes condensate in the condenser 25, and is transferred to the low boiling point medium evaporator 21 by the pump 27.
Supply liquid to. When the pressure of the low boiling point medium vapor becomes excessive, such as when the turbine is stopped, the bypass valve 23 is opened and the low boiling point medium vapor enters the condenser 25, and the low boiling point medium evaporator 21 always functions as a hot water cooler. In this way, this system can recover electricity from waste heat without interfering with the operation of the heating furnace. Note that this system is suitable when the hot water temperature is relatively low.

FIG. 6 shows another example equipped with a power recovery device using a hot water expander and a low pressure turbine. The hot water passes through the control valve 28 and enters the hot water expander 30 for expansion work, the exhaust air enters the steam-water separator 31, and the separated steam enters the low-pressure turbine 32 for expansion work. The generator 33 is driven. The turbine exhaust gas is condensed in a condenser 34 and returned to the water tank 3 via a pump 36 and a pipe 38. In addition, the hot water drain from the steam separator is returned to the water tank 3 via a pipe 37 using a pump 35. When the turbine is stopped, the bypass valve 29
The hot water from the exhaust gas hot water heater 10 can be constantly cooled and circulated as skid cooling water by opening the condenser 34 and filling the condenser 34 with hot water. This system is suitable when the hot water temperature is relatively high.

Since the heating furnace exhaust heat recovery device according to the present invention is configured as described above, the exhaust gas hot water heater and the feed water preheater are used to recover the exhaust gas from the low-temperature skid cooling water, which was conventionally considered difficult to use. By imparting retained heat within the maximum allowable range, it is possible to utilize the heat of the skid cooling water for power generation and other purposes, and prevents sulfuric acid corrosion in the exhaust gas hot water heater. In addition, it has the advantage that the skid cooler can be located outside of the boiler.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are layout diagrams showing different aspects of the conventional device, and Figure 4
The figure is a layout diagram of an embodiment of the device of the present invention.
5 and 6 are arrangement diagrams of different embodiments of the device of the present invention. 1... heating furnace, 2... skid cooler, 3...
Water tank, 4, 4', 27, 35, 36...pump,
5... Cooler, 6... Flash tank, 7...
...Steam pipe, 8...Exhaust gas duct, 9...Requiperator, 10...Exhaust gas hot water heater, 11...Feed water preheater, 12, 13, 14, 15, 20, 3
7, 38, A, B... Piping, 16... Bypass piping, 17... Water supply temperature detection device, 18, 19...
Flow rate control valve, 21...Low boiling point medium evaporator, 22,
28...Adjustment valve, 23, 29...Bypass valve, 2
4... Turbine, 25... Condenser, 26, 33...
... Generator, 30 ... Hot water expander, 31 ... Steam water separator, 32 ... Low pressure turbine, 34 ... Condenser.

Claims (1)

[Claims] 1 In a heating furnace with a water-cooled skid,
An exhaust gas hot water heater is provided in the exhaust gas duct, and piping A is used to guide the cooling water taken out from the skid to the exhaust gas hot water heater, and the hot water heated by the exhaust gas hot water heater is led out from the heater. A water supply preheater is provided in the middle of both pipes to exchange heat between the fluids in both pipes, and a water supply water preheater is provided along pipe A from the water supply preheater to the exhaust gas hot water heater. A feed water temperature detection device is installed between the upstream side of pipe A and pipe B to bypass the feed water preheater and exhaust gas hot water heater.
Bypass piping is provided that short-circuits the downstream side of the pipe A, and the signal from the feed water temperature detection device is provided on the pipe A from the branch point of the bypass pipe to the feed water preheater, as well as in the middle of the bypass pipe. A heating furnace exhaust heat recovery device each equipped with a flow rate control valve that controls the flow rate to adjust the temperature of the feed water.