JPH02219905A - Soot blow method of waste heat boiler - Google Patents

Abstract

PURPOSE:To sufficiently remove soot which adheres to a heating surface by spraying and mixing high temperature water in soot blow steam, making a soot blow medium of a steam and water mixture and jetting it in the same direction as a flow of an exhaust gas during operation of a waste heat boiler. CONSTITUTION:When operating time reaches the time necessary for soot blow, by the instruction of an automatic soot blow controller 7 a steam close valve 3 and a high temperature water close valve 4 are opened to inject high temperature water into soot blow steam from a high temperature spray nozzle 5 with proper quantity spray injection to mix steam with sprayed and injected high temperature water and the steam is jetted in the downstream direction of an exhaust gas passage from a plurality of a steam and water mixture jetting nozzle 6 arranged in the upstream side of a heating body exhaust gas passage as a steam and water mixed soot blow medium to blow off soot on the whole heating surface passage. When a jet time of the steam and water mixed soot blow medium reaches a set time, the spray of the high temperature water into the soot blow steam is stopped by closing the high temperature water close valve 4 with the use of the instruction of the automatic soot controller 7.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a soot blowing method for removing soot adhering to the exhaust gas flow path of a heat transfer body of a waste heat boiler during operation of the waste heat boiler. .

(Prior art) When exhaust gas passes through the fluid flow path of the heat transfer body of an exhaust heat boiler, soot in the wandering gas, which is composed of unburned oil, sulfur oxides, and ash, adheres to the heat transfer surface and deteriorates the boiler performance. Not only does this cause a decrease in the flow rate, but it also causes problems such as fluid flow path blockage as the operation continues.

In this case, vapor waves or compressed air were injected by a soot blower to remove soot adhering to the heat transfer surface. If soot cannot be removed sufficiently by blowing soot with steam or air, remove the waste heat boiler from the plant operating system by bypassing the exhaust gas passing through it, or shut down the plant. , waste heat boilers were flushed with large amounts of low-pressure or high-pressure water.

(Problem M to be solved by the invention) When the amount of soot on the heat transfer surface is small and the adhesion is weak, or when the amount of soot blowing medium supplied is large and the injection pressure is high, use of a soot blowing device using steam or air. However, if the amount of soot is large and the adhesion is strong, or if the amount of soot blowing medium supplied is small and the injection pressure is low, the above method may not be sufficient to remove soot. It becomes impossible to do so, and you have no choice but to wash it with water.

Soot blowing by water spraying injects a large amount of water, and if you flush while the waste heat boiler is operating, there is a risk of giving a thermal shock to the waste heat boiler, and the water washing water will stagnate at the bottom of the exhaust gas flow path of the heat transfer body. In such cases, washing with water while the waste heat boiler is in operation has not been put into practical use, as there is a concern that the lower material of the heat transfer body may corrode, and there is also a risk that soot may re-adhere to the full surface of the heat transfer body after washing. is the current situation.

Therefore, when washing the waste heat boiler with water, there is a problem in that the exhaust gas passing through the waste heat boiler must be bypassed and the waste heat boiler must be separated from the plant operation system, or the plant must be stopped. Furthermore, if water washing is performed, wastewater treatment becomes a problem.

(Objective of the Invention) The present invention aims to improve the problems pointed out in the above section of problems to be solved by the invention, and is aimed at improving the problems pointed out in the section of problems to be solved by the invention. Moreover, there is no corrosion damage to the lower material of the heat transfer body, no soot re-adhesions to the wet surface of the heat transfer body after soot blowing, and no need for water washing and wastewater treatment facilities. It is an object of the present invention to provide a method for blowing soot for an exhaust heat boiler that can sufficiently remove soot attached to a heat transfer surface with a small amount of steam.

(Means for achieving the objective) During the operation of the waste heat boiler, high-temperature water is mixed into the soot-blowing steam by a high-temperature water spray nozzle placed in the soot-blowing steam piping, and the steam-water mixture is The soot blowing medium is injected from a fixed or movable injection nozzle disposed upstream of the exhaust gas flow of the waste heat boiler heat transfer element. Furthermore, after the injection of the steam-water mixture is completed, the mixing of high-temperature water into the soot-blowing steam is stopped, and only the steam is injected from the injection nozzle.

(Function) In the present invention, by the above means, the high temperature water mixed into the soot blowing steam weakens the adhesion of soot on the heat transfer surface, and in combination with the peeling effect of the injection, the soot blowing effect increases. is obtained. Furthermore, injection using only steam after the injection using a steam/water mixture is completed removes moisture stagnant in the exhaust gas flow path of the heat transfer surface, and causes rapid drying of the heat transfer surface due to the exhaust gas passing therethrough. Combined, this provides the effect of preventing soot, which tends to adhere to wet surfaces, from re-adhering.

In the above means, the reason why water is injected into the steam is by spraying high-temperature water in order to prevent water hammer from occurring.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a flow sheet showing an embodiment of the soot blowing method for an exhaust heat boiler according to the present invention.

In the operating state of the exhaust heat boiler 1, when the operating time reaches the required soot blowing time, the automatic soot blowing control device 7 instructs the
The steam on-off valve 3 and the high-temperature water on-off valve 4 are opened, and an appropriate amount of high-temperature water is injected into the soot-blowing steam from the high-temperature water spray nozzle 5, and the steam is mixed with the injected high-temperature water to form a mixture of air and water temperatures. The blowing medium is injected in the downstream direction of the exhaust gas passage from a plurality of air/water mixture injection nozzles 6 arranged upstream of the heat transfer body exhaust gas passage, and blows soot over the entire surface of the heat transfer surface passage. When the injection time of the soot-blowing medium reaches the set time, the high-temperature water on-off valve 4 is closed according to the instructions from the automatic soot-blowing control device 7, and the spraying of high-temperature water into the soot-blowing steam is stopped. Only steam is injected from the water mixture injection nozzle 6 as a soot blowing medium.

Furthermore, when this injection reaches the set time, the steam on-off valve 3 is closed according to an instruction from the automatic soot blowing control device 7, and the soot blowing is completed.

In the above embodiment, canned water from the exhaust heat boiler 1 is used as the high-temperature water, and steam generated from the exhaust heat boiler 1 and supplied from the steam separator 2 of the boiler is used as the soot-blowing steam. In both cases, the internal pressure of waste heat boiler 1 (6
~10kgr/aa).

(Effect of the invention) During the operation of a waste heat boiler, soot that could not be removed sufficiently by injection using only steam or air as a soot-blowing medium is injected using a mixture of steam and an appropriate amount of high-temperature water as a soot-blowing medium. It was confirmed by measuring the exhaust gas pressure loss before and after the soot blowing operation that by doing so, sufficient removal could be achieved with a small amount of steam.

Furthermore, by injecting only steam after injecting the steam/water mixture, it has become possible to minimize the re-adhesion of soot to the wet surface of the heat transfer body after soot blowing.

As a result, it is possible to avoid the draft rise caused by the blockage of the exhaust gas flow path of the heat transfer body, which previously occurred, and the exhaust heat It became possible to maintain boiler performance.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing one embodiment of the present invention. Incidentally, the symbols of the main parts in the figure are as follows. 1...Exhaust heat boiler 2...Exhaust heat boiler steam water separator 3...Steam on-off valve 4...High temperature water on/off valve 5...High temperature water spray nozzle 6...Air-water mixture injection nozzle 7...Automatic soot blower control device Figure ″L

Claims (1)

[Claims] In a soot blowing method that removes soot adhering to the heat transfer surface of an exhaust heat boiler by spraying steam, high-temperature water is sprayed into the soot blowing steam, and the steam/water mixture is used as a soot blowing medium to blow the soot out of the exhaust heat boiler. A method of blowing soot for an exhaust heat boiler, which is characterized by injecting soot in the same direction as the flow of exhaust gas during operation.