JPH0757305B2 - Treatment method of exhaust gas containing hydrogen chloride - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating combustion exhaust gas containing hydrogen chloride gas and the like by using a filter dust collecting type exhaust gas treatment device, and more specifically, it reduces chlorine by backwashing the bag filter as much as possible. The present invention relates to a method capable of removing hydrogen with high efficiency.

[0002]

2. Description of the Related Art Generally, wet, semi-dry and dry alkali methods are used as methods for treating acidic exhaust gas such as hydrogen chloride-containing exhaust gas. The basic reaction of these methods is to blow an alkaline compound such as slaked lime into exhaust gas to neutralize an acidic substance such as hydrogen chloride, and proceed as shown in the following formula.

The reaction rate of the above reaction is low only by blowing Ca (OH) ₂ + 2HCl → CaCl ₂ + 2H ₂ O slaked lime. As shown in Fig. 2, dust containing unreacted slaked lime is deposited on the upstream surface of the bag filter (21), and exhaust gas is allowed to pass through this dust accumulation layer (22) to remove slaked lime and the exhaust gas in the accumulated layer. The hydrogen chloride removal rate is improved by the reaction with hydrogen chloride.

In the above-mentioned method, the reaction rate increases as the layer thickness of the dust accumulation layer increases, but if the accumulation layer becomes too thick, the ventilation resistance increases and it becomes impossible to suck the exhaust gas in the wake. Therefore, the bag filter is usually backwashed at any time to maintain the ventilation resistance of the deposited layer at a certain value or more.

[0005]

However, the exhaust gas treatment is inevitably stopped while the bag filter is backwashed, and frequent backwashing causes a reduction in exhaust gas treatment efficiency.

In view of the above points, an object of the present invention is to provide a method capable of removing hydrogen chloride with high efficiency by reducing the number of backwashing of a bag filter as much as possible.

[0007]

The present invention has been devised in order to achieve the above-mentioned object. When a mixture of slaked lime and calcium carbonate having a nonuniform particle size is used, even if the dust accumulation layer becomes thick, aeration can be achieved. It was completed with the knowledge that the resistance does not increase so much and therefore the number of backwashing can be reduced.

That is, the method for treating exhaust gas containing hydrogen chloride according to the present invention is obtained by mixing slaked lime as a neutralizing agent with calcium carbonate having a non-uniform particle size in exhaust gas treatment using a filter dust collecting type exhaust gas treatment machine. It is characterized in that the obtained mixture is blown into the exhaust gas in the upstream of the processing machine.

The particle size of slaked lime for neutralization is usually about 5 μm. Calcium carbonate having a nonuniform particle size is composed of particles having a nonuniform particle size of 5 μm or more.

[0010]

According to the method for treating exhaust gas containing hydrogen chloride of the present invention, in the exhaust gas treatment using the filter dust collecting type exhaust gas treatment machine, slaked lime as a neutralizing agent is obtained by mixing calcium carbonate having a nonuniform particle size. Since the resulting mixture is blown into the exhaust gas in the upstream of the processor, dust containing unreacted slaked lime particles and calcium carbonate particles of non-uniform particle size is deposited on the filter upstream surface of the filter dust collecting type exhaust gas processor. By passing exhaust gas through the dust deposit layer and reacting slaked lime in the deposit layer with hydrogen chloride in the exhaust gas, the contact area between slaked lime and hydrogen chloride in the exhaust gas is large, and as a result, a high reaction rate is obtained. Therefore, even if the dust accumulation layer is thick, the ventilation resistance is not so large, and the number of backwashing can be reduced.

[0011]

EXAMPLES Examples of the present invention will be shown below to specifically explain the present invention.

Neutralizing slaked lime particles (3) having a particle size of 5 μ are mixed with calcium carbonate particles (4) having an uneven particle size of 8 to 12 μ,
The resulting mixture was blown into the exhaust gas. As shown in FIG. 1, due to the bag filter installed downstream of the blowing section, unreacted slaked lime particles (3) and a non-uniform particle size of 8-12
Dust containing μ calcium carbonate particles (4) was deposited on the upstream surface of the bag filter (1). Exhaust gas was passed through the thus-formed dust deposition layer (2) to react slaked lime in the deposition layer with hydrogen chloride in the exhaust gas. This dust layer
In (2), the contact area between slaked lime and hydrogen chloride in the exhaust gas was large because the particle size of the calcium carbonate particles (4) in the sedimentary layer was non-uniform, resulting in a high reaction rate.

FIG. 3 shows the relationship between the layer thickness (z) of the deposited layer (2) and the ventilation resistance (ΔP). When the equivalent ratio is constant and the ventilation resistance (ΔP) is the same, the deposited layer (2) is shown. Is to see how much increases. From the figure, it can be seen that in the method of the present invention, the deposition layer (2) was increased under the above conditions as compared with the conventional method, and as a result, the contact area between slaked lime and hydrogen chloride in the exhaust gas was large and the reaction rate was improved. .

FIG. 4 shows the relationship between the equivalence ratio and the HCl removal rate. From the same figure, the HCl removal rate in the conventional method leveled off at 95% at the equivalence ratio of 3 or more, but due to the improvement of the reaction rate by the method of the present invention, it was almost the same as the conventional method at the equivalence ratio of 2.5 or more. It can be seen that an equivalent HCl removal rate of 95% is obtained.

Thus, in the method of the embodiment, even if the dust accumulation layer becomes thick, the ventilation resistance does not become so large, and therefore the number of backwashing can be reduced.

[0016]

According to the method for treating exhaust gas containing hydrogen chloride of the present invention, the ventilation resistance does not become so large even if the dust deposition layer becomes thick, and therefore the number of backwashing is reduced as much as possible to achieve high efficiency of hydrogen chloride. Can be removed with.

By thus improving the reaction rate, the supply amount of slaked lime can be reduced.

Further, the durability of the filter can be improved by reducing the number of backwashing.

[Brief description of drawings]

FIG. 1 is a sectional view of a bag filter showing a method according to an embodiment of the present invention.

FIG. 2 is a sectional view of a bag filter showing a conventional method.

FIG. 3 is a graph showing a relationship between a layer thickness (z) of a deposited layer and a ventilation resistance (ΔP).

FIG. 4 is a graph showing the relationship between the equivalence ratio and the HCl removal rate.

[Explanation of symbols]

 1 Bag filter 2 Dust accumulation layer 3 Unreacted slaked lime particles 4 Non-uniform particle size calcium carbonate particles

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Kono 5-3-8 Nishi-Kujo, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd. (56) Reference JP-A-1-155936 (JP, A) Kai 60-90028 (JP, A)

Claims (1)

[Claims] 1. In exhaust gas treatment using a filter dust collecting type exhaust gas treatment machine, a mixture obtained by mixing slaked lime as a neutralizing agent with calcium carbonate having a non-uniform particle size is used as an exhaust gas in the upstream of the treatment machine. A method for treating hydrogen chloride-containing exhaust gas, which comprises blowing into the interior.