JPH09250730A - Cooler for screw conveyor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust the temperature of cooling water in a water collecting tank tank and avoid hydrochloric acid dew point corrosion by attaching the water collecting tank to a water cooled screw conveyor for exhausting dust, which is arranged below a waste heat boiler and forming a circulating water channel between a cooling tower and a heat exchanger pipe in the water collecting tank. SOLUTION: In a waste heat boiler 1 using exhaust gas including corrosive gas and dust as a heat source, the dust dropping from the waste heat boiler 1 is conveyed by a water cooled screw conveyor 2, cooled, guided to a dust exhaust device in a downstream side from the inside of a system and exhaust outside the system. A water collecting tank 9 adjusts the quantity of cooling water circulated between a heat exchanger pipe 11 and a cooling tower by a control valve 12, so that the cooling water is cooled at about 80 deg.C. The cooling water is supplied to the conveyor 2 by a circulating water pump 10, and distributed to a system including a caging and a shaft by the conveyor 2. The cooling water whose temperature rises by the heat exchanging of the exhaust gas and the dust is returned to the water collecting tank 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device for a screw conveyor for discharging dust, which is installed below a heat exchanger for cooling exhaust gas containing corrosive gas and dust.

[0002]

2. Description of the Related Art Generally, a dust discharging device installed in a lower part of a waste heat boiler is a water-cooled screw conveyor in which a casing and a shaft are water-cooled in order to protect the dust from high-temperature exhaust gas and dust and to cool the dust. Has been adopted. Explaining the conventional embodiment with reference to FIG. 2, dust falls from the waste heat boiler (1) and is collected in the water-cooled screw conveyor (2). Dust whose temperature was 600-800 ° C just above the water-cooled screw conveyor was cooled down to about 300 ° C while being conveyed by the water-cooled screw conveyor, and was passed through a double damper (6) that discharges while sealing the system pressure. It is guided to the dust discharge device and discharged outside the system.

On the other hand, the cooling water is cooled to about 30 ° C. by the cooling tower (7) and then supplied to the water cooling screw conveyor (2) by the cooling water pump (8). The water-cooled screw conveyor is distributed and supplied to the system of the casing (3) and the shaft (4), and the cooling water rises by about 10 ° C. due to heat exchange with the exhaust gas and dust, and is returned to the cooling tower. still,
The amount of cooling water commensurate with the amount of water evaporated from the cooling tower is automatically replenished.

[0004]

The conventional method has the following problems. Exhaust gas and dust contain corrosive gases SO _X and HCL, and the shell temperature of the casing and the shaft is its dew point temperature (about 130 ° C, respectively).
If the temperature is lower than about 60 ° C., especially the water dew point temperature (about 50 ° C.), the steel skin corrodes early. In the case of the conventional method, since the cooling water supplied to the water-cooled screw conveyor is at a temperature close to room temperature, the temperature of the casing of the water-cooled screw conveyor and the iron shell temperature of the shaft have a much higher heat transfer coefficient on the water side than on the dust side. Since it is high, the temperature becomes equivalent to the cooling water temperature, and the temperature is lower than the above dew point temperature. Also, if the cooling water temperature is circulated above the above dew point temperature, the cooling tower will have special specifications due to heat resistance, and since the cooling tower is generally installed as a common equipment, it will interfere with cooling of other equipment, so it is not practically applicable. .

[0005]

[Means for Solving the Problems] In a facility equipped with a water-cooled screw conveyor for discharging dust falling from a waste heat boiler at a lower part of a waste heat boiler for cooling exhaust gas containing corrosive gas and dust to generate steam, The cooling water system of the water-cooled screw conveyor is provided with a water collecting tank having a heat exchanger tube built therein to form a water passage for circulating the cooling water in the water collecting tank by a circulating water pump, while the cooling tower and the water collecting tank are provided. (EN) A screw conveyor cooling device characterized in that a circulating water passage is formed between the heat exchanger pipe and a cooling water temperature inside a water collecting tank.

Explaining with reference to FIG. 1, the cooling water having a temperature of about 80 ° C. at the inlet of the water-cooled screw conveyor (2) rises by about 10 ° C. due to heat exchange with exhaust gas and dust, and rises to about 90 ° C.
Then, it is returned to the water collection tank (9) containing the heat exchanger tube (11). Here, the amount of cooling water to the heat exchanger tube is adjusted by the control valve (12), cooled to about 80 ° C., and then recirculated to the water cooling screw conveyor.

That is, a feature of the present invention is that the temperature of the cooling water supply of the water-cooled screw conveyor itself is raised by the heat received by the water-cooled screw conveyor itself. Therefore, it is not necessary to continuously heat with another heat source such as steam injection. However, when heat is received by the water-cooled screw conveyor at the time of startup, it is necessary to inject steam into the water collection tank to heat it. On the other hand, the original purpose of thermally protecting the device from high-temperature exhaust gas and dust and cooling the dust can be achieved with almost no difference even if the cooling water temperature rises to 80 ° C.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIG. In the figure, (1) is a waste heat boiler, which is provided with a water-cooled screw conveyor (2) at the bottom, and dust is exchanged with the casing (3) and the shaft (4) while being transported to the water-cooled screw conveyor, It is designed to cool the dust. Now, in the present invention, the cooling water system to the water cooling screw conveyor is made into a circulation system independently of the conventional cooling water system, and the heat exchanger pipe (11) is provided in the circulation system.
A water collecting tank (9) with a built-in is provided, and the water in the water collecting tank is circulated and supplied to the water-cooled screw conveyor by the circulating water pump (10), where the heat of the exhaust gas and dust is removed. It is designed to return warm water to the water collection tank and adjust it to an appropriate temperature.

Explaining the flow of dust and cooling water of the present invention having such a structure, the dust falls from the waste heat boiler (1) and is collected in the water cooling screw conveyor (2). The dust whose temperature was 600-800 ° C just above the water-cooled screw conveyor was cooled down to about 350 ° C while being conveyed by the water-cooled screw conveyor, and was passed through a double damper (6) that discharges while sealing the system pressure. It is guided to the dust discharge device and discharged outside the system.

On the other hand, as for the cooling water, the amount of cooling water to the heat exchanger pipe (11) built in the water collection tank (9) is adjusted by the control valve (12).
After adjusting the temperature with 80 ℃ and circulating water pump (10)
Is supplied to the water-cooled screw conveyor (2). Water-cooled screw conveyor has casing (3) and shaft (4)
The cooling water rises by about 10 ° C. due to heat exchange with exhaust gas and dust, and is returned to the water collection tank.
In addition, the amount of cooling water corresponding to the amount of water evaporated from the water collection tank is automatically replenished. Also, in consideration of the case where the heat received by the water-cooled screw conveyor is small at the time of startup, steam can be injected into the water collection tank.

[0011]

As described above, according to the present invention, the following effects are exhibited. (1) Hydrochloric acid dew point corrosion can be avoided, and sulfuric acid dew point corrosion can be suppressed to a slight level. (2) It is more economical than using high-grade materials. (3) The dust can be appropriately cooled while avoiding early corrosion.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a screw conveyor cooling device incorporating the device of the present invention,

FIG. 2 is a diagram showing an example of a conventional screw conveyor cooling device.

[Explanation of symbols]

 1 Waste Heat Boiler 2 Water Cooling Screw Conveyor 3 Casing 4 Shaft 5 Screw 6 Double Damper 7 Cooling Tower 8 Cooling Water Pump 9 Water Collection Tank 10 Circulating Water Pump 11 Heat Exchanger Pipe 12 Control Valve

Claims (1)

[Claims] 1. A facility provided with a water-cooled screw conveyor for discharging dust falling from the waste-heat boiler under a waste-heat boiler for cooling exhaust gas containing corrosive gas and dust to generate steam. A cooling water system is provided with a water collecting tank having a heat exchanger tube built therein, and a water channel for circulating cooling water in the water collecting tank by a circulating water pump is formed, while a cooling tower and the heat exchanger tube in the water collecting tank are formed. A screw conveyor cooling device, characterized in that a circulating water passage is formed between the circulating water and the cooling water temperature in the water collecting tank.