JPS6075318A - Treating apparatus of waste gas - Google Patents

Abstract

PURPOSE:To increase the efficiency of treatment by furnishing a moving-bed type packed layer of granular materials such as crushed stones at the upstream position of an electrical dust collector of the waste gas treating apparatus. CONSTITUTION:In the waste gas treating apparatus, fine powder contg. >=1 kind among calcium hydroxide, calcium oxide, and calcium carbonate is fluidized in a waste gas duct 2 to adsorb an acidic gas. Thereafter the solid fine powder in the waste gas is removed with an electrical dust collector 3. A moving-bed type packed layer 6 of granular materials such as crushed stones is furnished to an appropriate position on the upstream side of the electrical dust collector 3 after the fluidization of said fine powder.

Description

[Detailed description of the invention] Technical field The present invention relates to an exhaust gas treatment device for removing exhaust gas.

Conventional technology and its problems The exhaust gas from garbage incinerators contains HCl gas from the decomposition of chlorine-containing substances such as polyvinyl chloride, and in general, when sulfur-containing substances are burned, SOx is produced in the combustion gas. It is widely known that it is included. Conventionally, a wet absorption method using an alkaline aqueous solution or slurry as an absorbent was often used as a removal method, but a dry method was developed and gradually replaced the dry method because it requires less equipment and operating costs. .

Among the dry methods, dry absorption methods that use calcium oxide, calcium hydroxide, calcium carbonate, etc. are often used for economic reasons.For example, fine powder of calcium hydroxide is injected into the upstream duct of an electric dust collector. There is a device that reacts and absorbs these acidic gases and then removes the fine particles using a drowsiness dust collector. Furthermore, when treating boiler exhaust gas, there is also an apparatus in which fine powder of calcium carbonate is blown into the combustion chamber, decomposed, and converted into calcium oxide, which reacts with the acidic gas.

Figure 4 illustrates a process diagram for a waste incinerator. Exhaust gas containing HCl and SOx gas generated by combustion in the waste incinerator (1) enters the electric dust eliminator (3) through the duct (2). Calcium hydroxide fine powder is blown into the duct (2) at an appropriate position (8γ) along with air through a number of small holes provided on the periphery of the duct. so that the Reynolds number is several tens,0
Calcium hydroxide, which has been pulverized to a size of, for example, 200 mesh or more, flows into the exhaust gas and reacts with acidic gas on its surface, producing CaC/2, Ca5O, s and unreacted Ca (0
Solids such as 1() and 2 reach the electrostatic precipitator (3) together with the soot and dust in the exhaust gas, where they are electrically removed, and the removed exhaust gas is sucked in by the exhaust fan (4) and released from the stack (5). Ru.

When removing acidic gases such as general K HCl, 80X, etc. with a solid reactive absorbent, it is not sufficient to use only the chemical equivalent of the acidic gas.

FIG. 2 shows the relationship between the equivalent ratio of calcium hydroxide to acidic gas and the acidic gas removal rate when calcium hydroxide fine powder is used as the solid absorbent. However, the test conditions are gas temperature 2
50'O; Processing gas t 50 nf/m H in exhaust gas
C1g degree average 1000 ppm, SOx concentration average 1
0 (l ppm; average soot and dust concentration 4 f/N, packed bed volume 1 ft, this exhaust gas is a branched part of a 30 t/16 h garbage incinerator.

As shown by curve (1) (dotted chain line) in the figure, in the actual device, even if 7 times the chemical equivalent to acidic gas (equivalence ratio 7) is used, the HC1 removal rate is only 90%. Moreover, even if the equivalence ratio is further increased, it is hardly expected that the removal rate will increase.

OBJECTS OF THE INVENTION An object of the present invention is to provide an exhaust gas treatment device with a higher acid gas removal rate.

Structure of the Invention The exhaust gas treatment device of the present invention injects fine powder (referred to as calcium fine powder for simplicity) containing one or more of calcium hydroxide, calcium oxide, and calcium carbonate into an exhaust gas duct to flow into the exhaust gas. and acid gas (HCl
, 80X), crushed stone,
A moving bed-type packed bed of granular materials such as porcelain, silica sand, and perlite (referred to as granular materials such as crushed stone for simplicity) is installed to filter and capture calcium powder after reaction and absorption, and an electric collector is further downstream. A feature is that a duster is provided to electrically capture the solid fine powder that has passed through the packed bed (the distinction between upstream and downstream is based on the flow of gas).

Granular materials such as crushed stone that form a moving bed type packed bed hardly become finer due to movement, so it is desirable to use it repeatedly from an economic point of view, but it is desirable to use it repeatedly, but it is not a necessary condition. .

Calcium carbonate is different from calcium hydroxide and calcium oxide in the calcium fine powder of the reaction absorbent, and is in the form of a salt, but as mentioned above, when heated, it decomposes into calcium oxide and carbon dioxide. Therefore, by blowing into the combustion furnace or into the high temperature of the duct,
Shows the same reaction and absorption effect as calcium oxide.

It goes without saying that the exhaust gas generating device includes all devices that generate exhaust gas containing acidic gas, such as garbage incinerators, boilers, and general heating furnaces.

Effect of the invention In the exhaust gas injected with calcium fine powder, acidic gas is
It is the same as the conventional method (for example, the one shown in FIG. 4) that it reacts with fine calcium powder to solidify (react and absorb) and is removed.

However, if a packed bed of granular materials such as crushed stone is installed in the duct and exhaust gas containing fine calcium powder is passed through the bed, most of the calcium powder is captured and fixed in the packed bed. As a result, in the packed bed section, a fixed bed reaction takes place instead of a so-called fluidized bed reaction, and in this part, reaction absorption occurs due to the scrubbing effect due to the speed difference between the calcium fine powder and the waste gas to be treated. promoted.

In other words, in the device of the present invention, flow! ! The reaction absorption is performed using the II layer and the fixed NO, increasing the absorption rate, and the effect is shown by the curve ([)C in Figure 2.
Ca(OH)2 fine powder (chemical) k ti ijJ reuse L fx case], curve (110CCa(OR)2
When approximately half of the fine powder is recycled and reused, blown new Ca (O
H) 2 The amount of fine powder is the same as in (Ill). ], Curve (IV) shows the SOX removal efficiency in the case of (011). ] is oshi. (As is clear from the figure, there is no significant difference in the absorption rates of HCl and SOX.) As mentioned above, the removal efficiency of acid gas is improved by using a moving bed type packed bed, but this packing The installation of the layer reduces the load on the electrostatic precipitator and makes it possible to save expensive electricity.

Note that when the moving speed of particles in the packed layer is increased, the efficiency of removing acid gas increases, but the efficiency of removing soot and dust decreases (Figure 3). However, soot and dust can be removed with an electric dust remover.

Embodiment In FIG. 1, when the exhaust gas generated from the waste incinerator (not shown) passes through the duct (2), the peripheral part (8
The calcium powder is taken out from the silo through the plurality of calcium powder blowing ports (8a) provided in b), and then put into the blowing blower.
It is the same as the conventional method up to the point where calcium hydroxide fine powder fluidized by a gas filter (not shown) is blown in, and the calcium hydroxide fine powder and acidic gas in the exhaust gas move downstream while reacting in a fluidized state. be. In the present invention, a moving bed type photoreceptor layer (6) shown in FIG. The generated exhaust gas enters the moving bed-type packed bed section (6a) filled with particulate matter through the upstream gaps (6b) provided horizontally and outwardly upward, passes through it, and passes through the downstream gaps (6b). escape through.

Most of the reacted and unreacted calcium fine powder flowing in the exhaust gas and the soot dust contained in the exhaust gas are contained in this filling h#1.
'r(1 (6a)) captures and removes most of the fine powder that passes through this, is further captured and removed by the electrostatic precipitator (3), and is discharged outside the system via the conveyor (9) etc. of exhaust gas is released from the stack into the atmosphere.

The moving bed type packed layer (6) is filled with granular materials such as the aforementioned crushed stones, but these are not absorbed by the upper part of the layer (6).
The filling layer part (6a) is passed through the star-shaped gate valve (6d).
The particles are supplied to the hopper and discharged through the star-shaped sluice valve (6e) in the bottom section, and are separated into particles and fine powder by the vibrating sieve (7), and the particle portion is returned to the hopper for reuse.

The fine powder that has been passed through the sieve screen (7a) for 11 hours usually contains more than half of the unreacted calcium (the rest is Ca
These include C4j11CaSOB and soot. ), the use of calcium fines can be reduced by recycling when there are no other suitable uses.

Effect of the Invention In Fig. 2, in the conventional method, Ca
Even if the (OH)2 equivalent ratio is set to 7, the removal efficiency is only about 90%, but when the method of the present invention is used, the removal efficiency is about 90% at the equivalent ratio of 4 even when no InoI'I loading of calcium fine powder is performed. Removal rate of 1~ (approx. 98% at modern ratio 7) is reached, and when 50 ti of calcium-containing fine powder is reduced to 7,1'X1, Ca(0)L) 2 equivalent ratio 3.5 It is possible to achieve a removal efficiency of 90%. These relationships are 1-JCe
It is almost the same for both SOX and SOX.

[Brief explanation of the drawing]

Is Figure 1 an example of implementing the method of the present invention? C boss, schematic diagram,
Is Fig. 2 the conventional method or the present invention? When IJH did not circulate the 50 parts of the food products and when IJH did not circulate the 50 parts of the food products, I got stuck.
1) Chart showing the 14':I relationship between the ratio and the removal efficiency, Figures 71 to 3 show the relationship between the filter bed moving speed ratio, the 1ick removal rate, and the -LCe removal rate. Figure, 4th
The figure is a process diagram of the conventional method. ■... Garbage incinerator 2... Duct 3... Tortoise filler 4... Ventilator 5... Stack 6... Moving bed type photonic layer 7... Vibrating sieve 8a... Calcium fine powder injection hole 9... Competition V
Ko1-11 -1-,,,. 1. , -1 Question knee 1. ．． 1 Fig. 2 α(Ql()21-1) Fig. 3

Claims (1)

[Claims] 1. A fine powder containing one or more selected from the group including calcium hydroxide, calcium oxide, and calcium carbonate is caused to flow in an exhaust gas duct to react and absorb acidic gas, and then an electrostatic precipitator is used. In an exhaust gas treatment device for removing solid fine powder from exhaust gas: After the fine powder has been fluidized into the exhaust gas, and at an appropriate position upstream of the front We electrostatic precipitator, a moving bed type of particulate material such as crushed stone is placed. An exhaust gas treatment device characterized by filtering exhaust gas by interposing a packed bed. 2. The exhaust gas treatment device according to claim 1, wherein the granular material such as crushed stone includes a granular material obtained by removing the solid fine powder from the granular material containing the solid fine powder and taken out of the system. 3. A claim in which the fine powder containing one or more of the group consisting of calcium hydroxide, calcium oxide, and calcium carbonate includes a solid fine powder removed from the granules taken out of the system according to claim 1. The exhaust gas treatment device according to item 1 or 2.