JPH0319441B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering heat from tar or hot gas containing tar and dust.

The present invention recovers the heat of high-temperature gas containing tar or tar and dust in a fluidized bed waste heat boiler, and removes some of the solid fluid material in the waste heat boiler to which some of the tar or dust in the gas has adhered. Take out the
It is a combination of regenerating and recycling this solid fluid material and its regeneration method.

Traditionally, hot gases containing tar or tar and dust are produced from coke ovens or fixed bed coal gasifiers.

During normal coke oven operation, the high-temperature gas from the coke oven contains a large amount of tar vapor, naphthalene, etc., and although the amount varies depending on the type of coal charged into the coke oven and the carbonization temperature, it is generally Approximately 7 to 8% of the weight of the input coal becomes tar and is entrained in the generated gas. For this reason, if you attempt to recover heat from this high-temperature gas using a conventional smoke tube type waste heat boiler, tar or naphthalene in the gas condensed as the gas cools will adhere to the tube walls and cause blockages. Conventionally, high-temperature gas from a coke oven is collected in a collection pipe, and a gas liquid, which is a cooling condensate of coke oven gas, is sprayed directly onto this gas.
After cooling the gas to 80-90°C and removing most of the tar and dust in the gas, it is cooled to about 30°C in a condenser and sent to the refining process.

On the other hand, in a fixed bed gasifier, the coal supplied and the gasifying agent are brought into contact with each other in countercurrent flow within the furnace, so that the coal that enters the furnace is carbonized with the generated high-temperature gas, producing tar. The amount varies depending on the type of coal supplied and the carbonization temperature, but it is thought that about 3 to 5% of the weight of the supplied coal becomes tar and is entrained in the produced gas. For this reason, the same tar problem as in the case of coke oven gas occurs in the produced gas from a fixed bed gasifier, and in the past, the tar and dust in the gas was removed by spraying circulating water directly onto the produced gas. The temperature of the produced gas has dropped to about 200℃.

On the other hand, most of the tar in the gas is washed away by the cooling fluid in both coke ovens and fixed bed gasifiers, so the cleaning fluid is passed through a settler and the tar is recovered using the difference in specific gravity.

As you can see, in conventional coke oven gas, all the sensible heat of the high-temperature gas is discarded to the cooling water side, and even in the gas from the fixed bed gasifier, the sensible heat of the high-temperature gas up to about 200℃ is discarded into the cooling water.

Therefore, the present invention adopts a fluidized bed waste heat boiler to recover heat from these tars and high-temperature gases containing tar and dust, extracts the fluid material with tar attached continuously or intermittently, and converts the fluid material into a solvent. By washing and regenerating waste heat and recycling it in a fluidized bed waste heat boiler, it becomes possible to recover heat by rational means, which was previously thought to be impossible. It has its features.

(1) Since the tar in the gas adheres to the solid fluid material in the fluidized bed, there is no blockage of pipes caused by tar that occurs in conventional waste heat boilers.

(2) The high heat transfer coefficient, which is a feature of a fluidized bed, can be measured, so the heat transfer surface can be made smaller.

(3) Conventionally, waste heat boilers that use high-temperature gas that only contains dust have adopted a smoke tube type to prevent dust from accumulating in the boiler, and can only generate saturated steam, but fluidized bed waste heat boilers can only generate superheated steam. It is possible for this to occur.

(4) Continuous operation is possible because the solid fluid material with tar attached is regenerated and circulated.

(5) By using a desulfurizing agent such as dolomite or limestone in the solid fluid material, it is possible to simultaneously perform deflowing in the waste heat boiler.

Next, the method of the present invention will be explained using examples shown in the drawings.

The figure shows an example of a combination of a one-stage fluidized bed waste heat boiler and tar recovery equipment using a solvent.

In the figure, high-temperature gas containing tar or tar dust at normal pressure to several hundred atmospheres is line 1.
4, passes through a distributor 15, and is fed to the fluidized bed waste heat boiler 1 to fluidize the solid fluid material having a diameter of about 2 to 3 mm or less in the fluidized bed waste heat boiler 1. As the solid fluid material, silica sand, ash agglomerate, alumina balls, and when desulfurization is simultaneously performed in the waste heat boiler, solid desulfurization materials such as dolomite and limestone are used. The figure shows an example in which a large amount of debris is entrained in high-temperature gas.Agglomerate of debris is used as the solid fluid material, and the entrained debris is agglomerated and removed in the process of regenerating the solid fluid material with tar attached. It's on. Due to the action of the solid fluid material in the fluidized bed waste heat boiler 1, the sensible heat of the high temperature gas is uniformly transferred to the cooling pipe 16 with a high heat transfer coefficient. The cooling pipe 11 can be used for steam generation or air heater.

On the other hand, the high temperature gas is cooled in the fluidized bed waste heat boiler 1, and some of the condensed tar and dust adheres to the solid fluid material and is removed, leaving the waste heat boiler through the line 17. The solid fluid substance with tar and dust attached from the fluidized bed waste heat boiler 1 is extracted from the line 2 to the tar cleaning tank 3 at normal pressure to several hundred atmospheres, and is sent to the stirrer together with the solvent supplied from the line 4. 5 to wash off the tar and dust on the solid fluid material. The tar-containing solvent is extracted from line 6 and sent to a solvent and tar separation step or a purification step.

The solid fluid material and dust from which tar has been removed are extracted from the bottom of the cleaning tank 3, passed through a line 7, and separated into a solvent and solids by a filter 8. The separated solvent passes through line 9 and is combined with the solvent in line 6.

The solid fluid material and dust removed by the filter 8 are sent to the cyclone 12 through the line 11 by a carrier gas 10 such as air or preheated air, and the solid fluid material is extracted from the lower part of the cyclone 12 and transferred to the fluidized bed waste heat boiler 1. will be recycled. The carrier gas and fine dust enter the cyclone 13 from the upper part of the cyclone 12, and the fine dust in the carrier gas is removed.

[Brief explanation of the drawing]

The figure shows an example of an apparatus for carrying out the method of the present invention, and is an explanatory diagram of an apparatus that combines a fluidized bed waste heat boiler and tar recovery equipment. 1...Fluidized bed waste heat boiler, 2...Line, 3...
...Tar cleaning tank, 4...Solvent line, 5...Stirrer, 6, 7...Line, 8...Filter, 9...
... line, 10 ... carrier gas, 11 ... line,
12...Cyclone.

Claims (1)

[Claims] 1. Tar or high-temperature gas containing tar and dust at normal pressure to several hundreds of atmospheres is guided to a fluidized bed waste heat boiler that has a built-in cooling pipe for heat exchange. The heat of the gas is recovered, the tar and dust in the gas are made to adhere to the solid fluid material, the solid fluid material is led to the tar cleaning tank 2b, and the solid fluid material is stirred while adding a solvent to the tar cleaning tank. After washing off the tar and dust adhering to the gas and separating it from the solvent, the waste heat is recovered while being recycled to the fluidized bed waste heat boiler again. heat recovery method.