KR830001094B1 - How to reduce the dust in the exhaust gas of rotary kilns - Google Patents

Abstract

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Description

How to reduce the dust in the exhaust gas of rotary kilns

The present invention relates to a rotary kiln plant operating method for sending exhaust gas generated when the pulverized mineral in the rotary kiln is treated with a solid fuel to an electrostatic precipitator.

The process of depositing dust from dust-gas into rotary kiln plants has been known to be very difficult.

In general, electrostatic precipitator is used to clean the gas, and various additives are used to control the gas, and the intrinsic resistance of the dust is reduced to increase the function of the electrostatic precipitator having a dust cleaning efficiency of more than 99%. It is well known to control the gas flow by injecting water or steam with or without chemicals, and as a result, the resistivity of the dust is reduced to an acceptable level.

It is known from the prior art to regulate the exhaust gas flow from the rotary kiln for the burning of ore, especially when one or more water-soluble alkali metal compounds are injected into the gas stream before passing through the dust collector as a regulator, the cement raw material is converted into cement binder. do.

This control is effective for the resistivity of the dust, which reduces the resistivity below 10 ¹⁰ ohm cm and allows for increased filter flow and efficiency of the dust collector.

When using solid fuel in rotary kilns, a large amount of bonsai is produced and discharged to the dust collector. The particle size distribution of dust in the exhaust gas stream has a particle diameter of 10 to 20 microns.

These particles are difficult to collect and their resistivity sometimes exceeds a threshold of 10 ¹⁰ ohm cm and low sulfur is preferred to remove air pollution with sulfur oxides.

Recent investigations have reduced the resistance of bonsai to low-sulphur coal, which is below the dark threshold of sodium present in the ash of about 2% Na ₂ O.

It is well known to inject the water-soluble alkali metal compound into the exhaust gas stream before passing it through the settler as a regulator and the method reduces the resistance of the bonsai in the exhaust gas stream. In addition, when the regulator is injected into the exhaust gas stream, the regulator passes through the dust collector, so that the bonsai particles are extremely small and remain in suspension, resulting in irregular distribution of additives.

To achieve good control effect, the multistage injection nozzle and injection chamber must be used, which complicates the settler system.

According to the present invention, a rotary kiln operating method with a dust collector burns a solid fuel containing an alkali-metal compound before using the solid fuel in a rotary kiln to reduce the resistance of dust-exhaust gas.

The solid alkali-metal compound added to the solid fuel is combusted with the solid fuel to be properly distributed in the gas stream and react with the bonsai particles.

It is preferable to add a modifier (alkali-metal compound, or compound) to the solid fuel before grinding the solid fuel.

If the fuel and regulator are mixed well, the chemical composition of the bonsai will have a resistance below the threshold mentioned above by the regulator.

In another method, the alkali-metal compound is added by a solid solution compound by solid-fuel sparging.

Injecting a water-soluble alkali-metal compound containing sea water or water into the fuel results in a suitable regulator.

The regulator is preferably added in an amount equal to or greater than 2% Na ₂ O calculated on the basis of dust in the exhaust gas.

Preferred modifiers are added sodium solids to the solid fuel in a ratio of at least 1: 200 corresponding to the sodium content of the exhaust gas in an amount equal to Na ₂ O 2%.

This method worked very well.

Lime combustion plant has a daily output of 260 tons and the dust collector is partially burned by adding solid fuel with 3.5% sodium chloride calculated on the amount of dust rising from solid fuel burning (gas temperature is 40 ℃) before grinding the solid fuel. The efficiency was increased from 99.1% to 99.9%.

Yes

To improve the progress of the precipitator, a clean with a dry control of 260ts / 24hr was used in a Danish lime plant in June 1978. Clean fires oil / coal in proportion to 40/60% oil / coal equivalent to 40ts / 24hr coal.

Sodium chloride is separated directly from the coal while moving the conveyor belt before grinding in a coal mill.

The content of sodium chloride is 0.43% of coal.

The amount of Na ₂ O in the dust collected in the dust collector is 0.21% to 0.30%.

The results show a close relationship between the distribution of sodium chloride and the progress of the settler. The resistivity of the dust is reduced from 3.5 × 10 ¹² ohm × cm to 1.5 × 10 ¹¹ ohm × cm, and as a result, the dust concentration is reduced in the stack from 517 mg / Nm 3 dry gas to 64 mg / Nm 3 dry gas.

The feed rate is increased from 8.47 dm / sec to 12.73 cm / sec.

Claims (1)

In a rotary kiln plant with an electrostatic precipitator, a control method for reducing the specific resistance of the exhaust gases generated during the combustion process is characterized in that sodium chloride is added to the pulverized fuel in a ratio of 1: 200 before the solid fuel is combusted in the rotary kiln plant. A method for reducing dust by reducing the resistivity of exhaust gas.