JPH03267601A - Method and device for starting waste heat recovery heat exchanger - Google Patents

Abstract

PURPOSE:To prevent corrosion and deterioration of material constituting a heat exchange system and greatly shorten the time required for starting a waste heat recovery heat exchanger by providing a first and second circulation line, through a circulation pump, from an evaporator to the feed water inlet side of a preheater and to the steam outlet of a superheater. CONSTITUTION:For effecting a hot start, when feed water of nearly normal temperature is supplied into a feed water line 15, a main steam valve 11 is opened and a superheater feed valve 10, a preheater feed valve 9 and a boiler water circulation line main valve 8 are closed so that a boiler water circulation pump 4 is started to circulate boiler water between an evaporator 1 and a preheater 3, while the temperature therein is adjusted to prevent the moisture in waste gas from condensing on the heat transfer surface of the preheater 3. And for effecting a cold start, the valves 10 9 and 8 are opened and a feed water main valve 12 and the valve 11 are closed. And the pump 4 provided in a boiler water circulation line 5 is started to feed water into a superheater 1 and the preheater 3 to cause the superheater 1 and preheater 3 to act as effective heat transfer surfaces of a heat exchange system.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides high-temperature power discharged from power generation devices using gas turbines, diesel engines, fuel cells, etc., steel plants, garbage incineration plants, etc. The present invention relates to a method for starting an exhaust heat recovery heat exchange device that recovers heat from industrial exhaust gas and generates steam, and the device.

(Conventional technology) Conventionally, the evaporator of a relatively small exhaust heat recovery heat exchange device has a
Fire tube boilers are often used. In addition, when the saturated steam generated in the boiler body is further heated to create superheated steam, a superheater is attached. On the other hand, in a smoke tube boiler, if the feed water temperature is lower than the saturation temperature, a preheater may be installed to recover heat from the exhaust gas that has passed through the evaporator and raise the feed water supplied to the evaporator to near the saturation temperature. It's supposed to warm you up. That is, as shown in FIG. 4, in the conventional exhaust heat recovery heat exchange device, a superheater 1, an evaporator 2, and a preheater 3 are arranged in this order from the exhaust gas supply upstream side, and water is supplied from a water supply source valve 12. The saturated steam generated there enters the evaporator 2 through the water supply piping system (pipe line) 15 passing through the preheater 3, and is converted into superheated steam through the steam piping system (pipe line) 16 passing through the superheater 1 and the main steam valve 11. It is designed to be supplied to predetermined locations as Further, exhaust gas is supplied to the evaporator 2 by an exhaust gas piping system 14 that passes through the superheater 1, and after performing thermal work, is discharged to the outside of the system through the preheater 3.

(Problem to be Solved by the Invention) However, in the conventional exhaust heat recovery heat exchange device having the above-mentioned configuration, when recovering heat from industrial exhaust gas, it is common that the exhaust gas as a heat source is already contaminated. There were many. In particular, when supply water at a temperature close to room temperature is passed through the preheater, the following problems occur. In other words, (1) During normal operation (hot start), when supply water at a temperature close to room temperature is passed through the preheater, the moisture contained in the exhaust gas condenses on the heat transfer surface such as the heat transfer tube on the exhaust gas side. Furthermore, sulfur dioxide gas or the like dissolves into the droplets to generate acid, which significantly corrodes the heat transfer surface, which is likely to cause so-called "sulfuric acid corrosion."

(2) On the other hand, at the time of a cold start, there is no net steam generation, so there is almost no fluid flow between the water supply side and the water supply side in the superheater and preheater of the exhaust heat recovery heat exchange device. Therefore, the only effective heat transfer part of the heat exchange system is the evaporator, and it takes a considerable amount of time to complete startup.

(3) Furthermore, since no steam is generated during a cold start, the temperature of the heat transfer surface of the superheater is close to the temperature of the high-temperature exhaust gas. This results in material deterioration.

The present invention was made to solve these problems, and in addition to the water supply piping system and steam piping system of the conventional waste heat recovery heat exchange device, it also uses the supply water stored in the evaporator (boiler water). ) to the preheater and superheater simultaneously or sequentially to the preheater and superheater and return it to the evaporator. It is said that

[Structure of the invention]

(Means and effects for solving the problems) The present invention has a superheater, an evaporator, and a preheater that are sequentially provided along the flow direction of exhaust gas, and feed water is sequentially passed from the preheater to the evaporator and superheater. A method for starting an exhaust heat recovery heat exchange device that generates steam by contacting flowing exhaust gas separated by a heat transfer surface, and in the device, from the evaporator to the water supply inlet side of the preheater and the superheater. First and second circulation pipes are provided to the steam outlet side of the evaporator via a circulation pump, and when starting up the device, firstly, the feed water stored in the evaporator is passed through the first and second circulation pipes, and one is The water is made to flow from the preheater to the evaporator and from the superheater to the evaporator to raise the temperature to a predetermined temperature, and then the feed water is made to flow sequentially from the preheater to the superheater according to a determined path to generate steam. It is characterized by the following.

(Example) An example of the exhaust heat recovery heat exchange device of the present invention will be described with reference to FIG.

FIG. 1 shows a system configuration diagram of the exhaust heat recovery heat exchange device, in which a superheater 1, an evaporator 2, and a preheater 3 are arranged in this order from the upstream side of the exhaust gas, and water is supplied to the preheater via the water supply source valve 12. 3
The saturated steam generated here enters the evaporator 2 through a water supply piping system (pipe line) 15 that flows to the superheater 1 and the main steam valve 11.
The steam is supplied as superheated steam to a predetermined location through a steam piping system (pipe line) 16 that passes through. Also, evaporator 2
Industrial exhaust gas is supplied to the system through an exhaust gas piping system (pipe line) 14 passing through a superheater 1, and after performing the work of generating steam, is discharged outside the system through a preheater 3.

In the exhaust heat recovery heat exchange device of the present invention, in addition to these water supply piping system (pipe line) 15, steam piping system (pipe line) 16, and exhaust gas piping system (pipe line) 14, the boiler water circulation piping system (pipe line)
5 will be placed. That is, as shown in FIG. 1, this boiler water circulation piping system (pipe line) 5 includes, in order from the side connected to the evaporator 2, a boiler water circulation piping system main valve 8, a boiler water circulation pump 4, and a flow Jl control valve. 6. A flow path consisting of a superheater supply valve 10 that joins the steam piping system 16 on the downstream side of the superheater 1, and a flow path that branches downstream of the flow control valve 6 and passes through the preheater supply valve 9 to the water supply side upstream of the preheater 3. It consists of a flow path that joins the water supply piping system 15 at. Here, the piping system from the evaporator 2 to the water supply inlet side of the preheater 3 is referred to as a first circulation piping, and the piping system from the steam outlet side of the superheater 1 is referred to as a second circulation piping. Also,
A temperature detector 7 is disposed in the water supply piping system 15 on the upstream side of the preheater 3 and on the downstream side of the confluence with the branch flow path of the boiler water circulation piping system 5 in order to measure the temperature of the water supply at the inlet of the preheater. , in conjunction with the flow control valve 6 to adjust its valve opening.

Boiler water circulation piping system (pipe line) configured in this way
The effect of No. 5 will be explained below. First, during normal operation (hot start), if the water supply source valve 12 is opened and water at a temperature close to room temperature is supplied to the water supply piping system 15, the main steam valve 11 is opened and the superheater The supply valve 10 is closed, the preheater supply valve 9 and the boiler water circulation piping system main valve 8 are opened, the boiler water circulation pump 4 is started, and the boiler water is circulated between the evaporator 2 and the preheater 3. let Furthermore, the preheater inlet water supply temperature is measured by a temperature detector 7,
The circulating flow rate of the boiler water is adjusted so that the temperature is such that the moisture contained in the exhaust gas does not condense on the heat transfer surface of the preheater 3.
The opening degree of the fi control valve 6 is adjusted to mix the feed water and boiler water at the confluence point downstream of the preheater supply valve 9.

Further, at the time of a cold start, the superheater supply valve 10, the preheater supply valve 9, and the boiler water circulation piping system main valve 8 are opened, and the water supply main valve 12 and the main steam valve 11 are closed. Then, the boiler water circulation pump 4 installed in the boiler water circulation piping system 5 is started, and the boiler water is passed through the superheater 1 and the preheater 3, and the superheater 1 and the preheater 3 are also used for effective transfer of the heat exchange system. The exhaust heat recovery heat exchange device can be activated without acting as a heating surface and circulating the boiler water in the boiler water circulation piping system 5.

According to this embodiment, during normal operation (hot start) of the device, the temperature of the feed water flowing into the preheater can be maintained above its dew condensation point, thereby preventing corrosion of the heat transfer surface of the preheater. As a result, it is possible to significantly extend the life of the device. Furthermore, at the time of a cold start of this device, the superheater and preheater act as effective heat transfer surfaces of the heat exchange system, so the time required to complete startup of the device is significantly shortened.

Another embodiment of the exhaust heat recovery heat exchange device of the present invention is shown in FIG. In FIG. 2, components that are basically the same as those in the embodiment shown in FIG. 1 will be omitted here using the same reference numerals, and only the differences will be explained. In this embodiment, when viewed from the connection side to the evaporator 2, the boiler water circulation piping system main valve 8, the boiler water circulation pump 4
A boiler water circulation piping system 5 consisting of a flow rate control valve 6 and a preheater supply valve 9 is joined to a water supply piping system 15 upstream of the water supply side of the preheater 3. In addition, as in the embodiment shown in FIG.
to measure the temperature of the preheater inlet water supply.

Further, an evaporator supply valve 13 is disposed in the water supply piping system 15 downstream of the water supply side of the heater 3, and a branch pipe is branched from the pipe on the upstream side of the evaporator supply valve 13. the steam piping system 1 downstream of the superheater 1 via the superheater supply valve 10
Merge into 6. Here, the piping system from the evaporator 2 to the water supply inlet side of the preheater 3 is called a first circulation pipe, and the piping system from the water supply outlet side of the preheater 3 to the steam outlet side of the superheater 1 is called a second circulation pipe. shall be. Almost the same as the embodiment shown in FIG. 1, during normal operation (hot start), the water supply source valve 12 and the main steam valve 11 are opened, the superheater supply valve 10 is closed, and , Boiler water circulation piping system main valve 8
, the preheater supply valve 9 and the evaporator supply valve 13 are opened, the boiler water circulation pump 4 is started, and the opening of the flow rate control valve 6 is adjusted to mix the boiler water and the feed water while flowing the water to the preheater 3. Water is supplied to the evaporator 2. In addition, at the time of a cold start, the main valve 8, the flow rate control valve 6, the preheater supply valve 9, and the superheater supply valve 10 are opened, and the main steam valve 11 and the water supply source valve 1 are opened.
2 and the evaporator supply valve 13 are kept closed. Then, the boiler water circulation pump 4 is started to circulate the boiler water through the pump water circulation piping system 5, and the water is sequentially passed through the superheater 1 and the preheater 3 before starting the apparatus. This prevents dew condensation on the heat transfer surface of the preheater, and significantly shortens the time required to complete startup of the exhaust heat recovery heat exchange device during a cold start.

Still another embodiment of the exhaust heat recovery heat exchange device of the present invention is shown in the third embodiment.
As shown in the figure. In FIG. 3, components that are basically the same as those in the embodiment of FIG. 1 will be omitted here using the same reference numerals, and only the differences will be explained. In this embodiment, a boiler water circulation piping system 5 consisting of a boiler water circulation piping system main valve 8, a boiler water circulation pump 4, a flow control valve 6, and a preheater supply valve 9 when viewed from the connection side to the evaporator 2 is used to supply water to the preheater 3. Water supply piping system 1 on the side upstream
Merge into 5. Further, as in the embodiment shown in FIG. 1, a temperature detector 7 is provided to measure the temperature of the water supply at the inlet of the preheater. With this configuration, during normal operation (hot start), the water supply source valve 12 and the main steam valve 11 are opened, the boiler water circulation piping system source valve 8 and the preheater supply valve 9 are opened, and the boiler is closed. The water circulation pump 4 is started, and while adjusting the opening degree of the flow rate control valve 6, the boiler water and the feed water are mixed, and the water is passed through the preheater 3 and supplied to the evaporator 2. Further, at the time of a cold start, the main valve 8, the flow rate control valve 6, and the preheater supply valve 9 are opened, and the main steam valve 11 and the water supply valve 12 are closed. Then, the boiler water circulation pump 4 is started to circulate the boiler water through the pump water circulation piping system 5, while the water is not passed through the preheater 3 before starting the apparatus. This results in
Condensation on the heat transfer surface of the preheater 3 is prevented, and the time required to complete startup of the exhaust heat recovery heat exchange device during a cold start is significantly shortened.

〔Effect of the invention〕

According to the present invention, since the boiler water circulation piping system is provided in the exhaust heat recovery heat exchange device, corrosion and deterioration of the materials of the devices constituting the heat exchange system are prevented, and the exhaust heat recovery heat exchange device This brings about remarkable effects such as a significant reduction in the required startup time.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram of one embodiment of the exhaust heat recovery heat exchange device of the present invention, and FIGS. 2 and 3 are system configuration diagrams of other embodiments of the exhaust heat recovery heat exchange device of the present invention. Figure 4 shows a system configuration diagram of a conventional exhaust heat recovery heat exchange device. 1... Superheater, 2... Evaporator, 3... Preheater, 4
...Boiler water circulation pump, 5...Boiler water circulation piping system (pipe line), 6...Flow rate control valve, 7...Temperature detector, 8...Boiler water circulation piping system main valve, 9...・Preheater supply valve, 10... Superheater supply valve, 11... Main steam valve,
12... Water supply source valve, 14... Exhaust gas piping system (pipe line)
, 15... Water supply piping system (pipe line), 16... Steam piping system (pipe line).

Claims (1)

[Claims] 1. A superheater, a generator, and a preheater are provided in sequence along the flow direction of the exhaust gas, and supply water is made to flow sequentially from the preheater to the evaporator and the superheater to transfer heat. In a method for starting an exhaust heat recovery heat exchange device that generates steam by contacting flowing exhaust gas separated by a surface, a first First and second circulation pipes are provided via a circulation pump, and when starting up the apparatus, firstly, the supply water stored in the evaporator is passed through the first and second circulation pipes, and one is supplied from the preheater to the above. The water is made to flow through the evaporator and from the superheater to the evaporator to raise the temperature to a predetermined temperature, and then the feed water is made to flow sequentially from the preheater to the superheater according to a determined path to generate steam. A method for starting an exhaust heat recovery and exchange device, characterized in that: 2. A superheater, an evaporator, and a preheater are provided sequentially along the flow direction of the exhaust gas, and the feed water flows sequentially from the preheater to the evaporator and superheater, separated by a heat transfer surface. In a starting device for an exhaust heat recovery heat exchange device that is brought into contact with exhaust gas to generate steam, first and second circulations are carried out from the evaporator to the water supply inlet side of the preheater and the steam outlet side of the superheater. A starting device for an exhaust heat recovery heat exchange device, characterized in that piping is provided via a circulation pump. 3. A superheater, an evaporator, and a preheater are provided sequentially along the flow direction of the exhaust gas, and the feed water flows sequentially from the preheater to the evaporator and superheater, separated by a heat transfer surface. In a method for starting an exhaust heat recovery heat exchange device that is brought into contact with exhaust gas and generates steam, from the evaporator to the water supply inlet side of the preheater and from the water supply outlet side of the preheater to the steam outlet side of the superheater. First and second circulation pipes are installed via a circulation pump, and when starting up the device, first the feed water stored in the evaporator is passed through the first circulation pipe, and then the second circulation pipe is passed through. The feed water is made to flow sequentially from the preheater to the superheater to raise the temperature to a predetermined temperature, and then the feed water is made to flow sequentially from the preheater to the superheater according to a predetermined path to generate steam. A method for starting an exhaust heat recovery heat exchange device characterized by: 4. A superheater, an evaporator, and a preheater are provided sequentially along the flow direction of the exhaust gas, and the feed water flows sequentially from the preheater to the evaporator and superheater, separated by a heat transfer surface. In a starting device for an exhaust heat recovery heat exchange device that is brought into contact with exhaust gas and generates steam, from the evaporator to the water supply inlet side of the preheater and from the water supply outlet side of the preheater to the steam outlet side of the superheater. 1. A starting device for an exhaust heat recovery heat exchange device, characterized in that first and second circulation pipes are provided through a circulation pump.