TWI682808B - Acid gas treatment agent and acid gas treatment method - Google Patents

Abstract

The present invention provides an acid gas treatment agent using sodium bicarbonate as a neutralizing agent for acid gas, which is not easily consolidated and is excellent in peelability. The present invention is an acid gas treatment agent containing sodium bicarbonate and a sodium bicarbonate solidification inhibitor, which is carbon black and/or hydrophobic silica. The content of the anti-consolidation agent is preferably 0.1 to 2.0% by weight. The average particle size of the hydrophobic silica is 1-20 μm, and the average particle size of carbon black is preferably 0.1-10 μm.

Description

Acid gas treatment agent and acid gas treatment method

The present invention relates to an acid gas treatment agent and an acid gas treatment method for neutralizing acid gas such as hydrogen chloride or sulfur oxide in combustion exhaust gas discharged from a waste treatment device or a power generation boiler.

As a treatment agent for acid gases such as hydrogen chloride or sulfur oxides in the combustion exhaust gas discharged from waste treatment equipment or power generation boilers, a calcium-based exhaust gas treatment agent such as calcium hydroxide or sodium such as sodium bicarbonate is used Department of exhaust gas treatment agent.

When using calcium hydroxide as an exhaust gas treatment agent, it is necessary to use an excess of 3 to 4 times the equivalent amount of acid gas, so the amount of dust generated is large. Although sodium bicarbonate needs to be used in a smaller amount than calcium hydroxide, particulate sodium bicarbonate-based particles are easily aggregated and consolidated.

As a method for preventing this consolidation, the following method is proposed.

A method of adding fine particles of fumed silica (hydrophilic consolidation preventive agent) to fine powder sodium bicarbonate (Patent Documents 1 and 2).

Wet wet silica is used as the anti-consolidation agent, and a metal soap is added and mixed at an appropriate ratio to the peeling enhancer of sodium bicarbonate formed on the filter cloth surface of the bag filter (Patent Literature 3).

In Patent Document 4, there is proposed an acid gas treatment agent containing zeolite and sodium bicarbonate and further blended with synthetic silica. In Patent Document 4, hydrophilic synthetic silica is also used as synthetic silica.

In Patent Document 5, there is proposed an exhaust gas treatment agent using activated carbon as an anti-consolidation agent.

[Patent Document 1] Japanese Patent Laid-Open No. 2000-218128

[Patent Document 2] Japanese Patent Laid-Open No. 2001-314757

[Patent Document 3] Japanese Unexamined Patent Publication No. 2005-186037

[Patent Document 4] Japanese Patent Application Publication No. 2013-193005

[Patent Document 5] Japanese Patent Laid-Open No. 2004-141718

For example, dry silica with a small average particle size of gas-phase silica is generally expensive, which increases the cost of the anti-consolidation agent. Wet silica or hydrophilic synthetic silica is cheap and has a large effect of preventing consolidation. On the other hand, its hydrophilicity leads to poor fluidity. Therefore, the peelability of the filter cloth surface of the bag filter is not good, which lowers the air permeability of the filter cloth and increases the pressure loss. If the blending ratio of activated carbon is not enough, a sufficient effect of preventing consolidation cannot be obtained.

Use wet silica for the prevention of sodium bicarbonate consolidation As a peeling enhancer of sodium bicarbonate formed on the filter cloth surface of the bag filter, a method of adding and mixing metal soap at an appropriate ratio is a consumption of two agents, namely, a consolidation preventive agent and a peeling enhancer. The cost is higher.

As mentioned above, a highly effective drug that has both the function of preventing the consolidation and the function of improving the peelability is sought.

The present invention aims to provide an acid gas treatment agent that uses sodium bicarbonate as a neutralizing agent for acid gas, and is an acid gas treatment agent that is not easily consolidated and has excellent peelability. The present invention also aims to provide an acid gas treatment method using the acid gas treatment agent.

The inventors found that the carbon black and the hydrophobic silica have both the function of preventing consolidation and the improvement of peelability, and can solve the above problems.

The present invention focuses on the following.

[1] An acid gas treatment agent containing a sodium bicarbonate and a sodium bicarbonate consolidation inhibitor, characterized in that the consolidation inhibitor is carbon black and/or hydrophobic silica.

[2] The acid gas treatment agent according to [1], wherein the content of the anti-consolidation agent is 0.1 to 2.0% by weight.

[3] The acid gas treatment agent according to [1] or [2], wherein the average particle diameter of the hydrophobic silica is 1 to 20 μm.

[4] The acid gas treatment agent according to any one of [1] to [3], wherein the average particle size of the carbon black is 0.1 to 10 μm.

[5] The acid gas treatment agent according to any one of [1] to [4], wherein the average particle diameter of the sodium bicarbonate is 5 to 30 μm.

[6] An acid gas treatment method characterized by adding the acid gas treatment agent according to any one of [1] to [5] to an exhaust gas containing an acid gas.

[7] A sodium bicarbonate consolidation inhibitor made of carbon black and/or hydrophobic silica.

According to the acid gas treatment agent of the present invention, the carbon black and/or hydrophobic silica mixed as a consolidation inhibitor not only prevents the consolidation of sodium bicarbonate, but also functions as an adhesion to the filter cloth surface of the bag filter, etc. Function to improve peelability. Therefore, the acid gas treatment can be efficiently performed with the following effects.

(1) Since it is not easy to consolidate and has excellent fluidity, it has excellent operability during storage and transportation or acid gas treatment.

(2) The consolidation system is prevented and can be added to the acid gas in a fine powder state, so the reactivity with the acid gas and the treatment efficiency are high.

(3) It is not easy to adhere to the filter cloth surface of the bag filter, and is easy to peel, so it is possible to suppress the increase of the pressure loss of the bag filter and continue the treatment stably.

(4) Only a small amount of carbon black and/or hydrophobic silicon dioxide can fully obtain the effect of preventing consolidation and peeling. Therefore, it is possible to increase the mixing ratio of sodium bicarbonate used for acid gas neutralization in the acid gas treatment agent, and to be an acid gas treatment agent excellent in the treatment efficiency of acid gas.

(5) Carbon black and hydrophobic silica require only a small amount of additive concentration, so the blending of carbon black and hydrophobic silica can provide an inexpensive acid gas treatment agent.

1‧‧‧ case

2‧‧‧ Acid gas treatment agent

3‧‧‧load

11‧‧‧heater

13‧‧‧Pharmaceutical dosing machine

15‧‧‧Bag filter

17‧‧‧cooling tower

18‧‧‧ Neutralization Tower

19‧‧‧Induced draft fan

[Fig. 1] A cross-sectional view showing a load test device in Examples.

[Fig. 2] A system diagram showing a bag filter test device in Examples.

The present invention will be described in detail below.

In the present invention, the average particle diameter of the drug refers to the weight median diameter D ₅₀ measured by the laser diffraction and scattering method (“SALD-7500nano” manufactured by Shimadzu Corporation).

<sodium bicarbonate>

The acid gas treatment agent of the present invention uses sodium bicarbonate as a neutralizing agent for acid gas. As the sodium bicarbonate, it is preferable to use one in which crude sodium bicarbonate is crushed to an average particle diameter of 5 to 30 μm.

If the average particle size of sodium bicarbonate exceeds 30 μm, the reactivity with the acid gas such as hydrogen chloride or sulfur oxides in the exhaust gas and the removal rate will be extremely low. Therefore, it is preferable to use fine powder sodium bicarbonate having an average particle diameter of 30 μm or less as sodium bicarbonate.

To effectively obtain the consolidation prevention effect caused by the present invention as The premise is that sodium bicarbonate is preferably a fine powder with an average particle diameter of 20 μm or less that is particularly easy to consolidate.

The acid gas treatment agent of the present invention is a carbon black and/or hydrophobic silica blended as an anti-consolidation agent, and a small amount of the additive can achieve high anti-consolidation and peeling enhancement effects. Therefore, the blending of carbon black and/or hydrophobic silica is relatively low, and the blending of sodium bicarbonate as an acid gas processing component is relatively high, and it can be an acid gas processing agent excellent in acid gas processing efficiency .

The acid gas treatment agent of the present invention preferably contains an anti-consolidation agent in a later-described preferred content, and the content of sodium bicarbonate is preferably 95% by weight or more, particularly preferably 98% by weight or more.

<Consolidation preventive agent>

In the present invention, carbon black and/or hydrophobic silica are used as the anti-consolidation agent having both the anti-consolidation function and the peelability improvement function.

As the carbon black, those having an average particle size of 0.1 to 10 μm, particularly 0.1 to 1 μm are preferred. If the average particle size of the carbon black is too large, the effect of preventing consolidation becomes low. Carbon black with an excessively small average particle size is not practical from the viewpoint of operability and cost, and the effect of improving the peelability is low, which tends to increase the pressure loss of the bag filter.

As the hydrophobic silica, a silica surface-treated with a hydrophobic treatment agent such as silicone oil or silazane compound on the particle surface can be used. The average particle size of the hydrophobic silica is 1-20 μm, particularly preferably 1-5 μm. If the average particle size of hydrophobic silica If the diameter is too large, the effect of preventing consolidation becomes low. If the average particle size of the hydrophobic silica is less than 1 μm, a sufficient peelability improvement effect cannot be obtained, and the pressure loss of the bag filter is likely to increase.

The content of the carbon black or hydrophobic silica used as the anti-consolidation agent in the acid gas treatment agent is preferably 0.1 to 2.0% by weight, particularly 0.1 to 1.0% by weight. If the content of the anti-consolidation agent is too small, a sufficient anti-consolidation effect cannot be obtained. If the content of the anti-consolidation agent is too large, the effect of improving the peelability cannot be obtained, and the pressure loss of the bag filter is likely to increase.

As an anti-consolidation agent, carbon black and hydrophobic silica may be used together. At this time, the total content of carbon black and hydrophobic silica in the acid gas treatment agent is still preferably 0.1 to 2.0% by weight, particularly 0.1 to 1.0% by weight. In particular, it is preferable to achieve the above-mentioned total content within the range of 0.1 to 1.0% by weight of carbon black and 0.1 to 1.0% by weight of hydrophobic silica.

<Preparation of acid gas treatment agent>

The acid gas treatment agent of the present invention is, for example, a crude sodium bicarbonate pulverized to an average particle size of 5 to 30 μm and carbon black and/or hydrophobic silica at a predetermined ratio by a ribbon blender (ribbon blender) or A nauta mixer and the like are uniformly mixed to prepare.

For the preparation of the acid gas treatment agent of the present invention, other agents other than sodium bicarbonate and carbon black and/or hydrophobic silica may be mixed.

Although the acid gas treatment agent of the present invention may also contain chemicals other than sodium bicarbonate and carbon black and/or hydrophobic silica, the carbonic acid caused by carbon black and/or hydrophobic silica can be effectively obtained The effect of the prevention of the consolidation of sodium bicarbonate and the improvement of the peeling property is premised. The acid gas treatment agent of the present invention is preferably composed of sodium bicarbonate, carbon black and/or hydrophobic silica.

<Acid gas treatment method>

The acid gas treatment method of the present invention is one in which the acid gas treating agent of the present invention is added to an exhaust gas containing an acid gas to perform exhaust gas treatment.

The exhaust gas treated by the acid gas treatment agent and acid gas treatment method of the present invention is, for example, the discharge of acid gas containing hydrogen chloride or sulfur oxides from waste treatment facilities, power boilers such as coal boilers and biomass boilers gas.

The addition amount of the exhaust gas by the acid gas treatment agent of the present invention is not particularly limited, and it may be appropriately determined depending on the concentration of the acid gas and the like in the range of the exhaust gas amount of 0.1 to 10 g/m ³ . As described above, the acid gas treatment agent of the present invention can increase the blending ratio of sodium bicarbonate, which is an effective component of acid gas treatment, so that the necessary addition amount can be suppressed and efficient treatment can be performed.

The exhaust gas containing acid gas is generally subjected to dust removal treatment with a bag filter after adding the acid gas treatment agent of the present invention. The acid gas treatment agent of the present invention improves the releasability by carbon black and/or hydrophobic silica, so that the pressure loss of the bag filter can be suppressed to continue stable treatment.

[Example]

The following examples are given to illustrate the present invention more specifically.

[Pharmacy]

In the following examples, comparative examples, and reference examples, the following were used as treatment agents.

Sodium bicarbonate: Crushed crude sodium bicarbonate to an average particle size of 10 μm (hereinafter referred to as “crushed sodium bicarbonate”).

Carbon black: carbon black with an average particle size of 0.25 μm

Hydrophobic silica: Hydrophobic silica with an average particle size of 1.55 μm, treated with silicone oil on the surface of the particles

Wet silica: Wet silica with an average particle size of 13.85μm

Calcium stearate: calcium stearate with an average particle size of 4.22 μm

Natural zeolite: natural zeolite with an average particle size of 8.10 μm

[Examples 1 to 5, Comparative Examples 1, 2, Reference Examples 1 to 4]

The acid gas treatment agent was prepared by blending the chemicals shown in Table 1. For each acid gas treatment agent, the following load test and bag filter test are performed. The results are shown in Table 1.

<Load Test>

Using the load test device shown in Fig. 1, the fixability was evaluated as follows.

A 100 mm×100 mm frame-shaped box 1 is filled with 100 g of acid gas treatment agent 2 and a load 3 of 10 kg is applied for 3 hours. After that, the acid gas treatment agent was placed on a stainless steel sieve with a mesh size of 355 μm, the fine powder was partially dropped, and the weight of the coarse particles remaining on the sieve was measured to calculate the ratio (weight %) to the weight for the test . The smaller the ratio on the sieve, the more it is possible to prevent consolidation, and the fine powder part falls.

A 10g sample was dropped from a glass cylinder with a height of 600mm and dropped to the lower watch glass, and the weight Mg remaining on the watch glass was weighed, and the dispersion degree (10g sample) was calculated by the following formula The proportion of the weight that has been scattered). The greater the degree of dispersion, the higher the dispersibility and the prevention of consolidation.

Dispersion (%)={(10-M)/10}×100

<bag filter test>

Using the bag filter test device shown in FIG. 2, the bag filter inlet/outlet pressure was measured, whereby the pressure loss of the bag filter caused by the acid gas treatment agent was increased to evaluate the peelability.

In Figure 2, the 11 series heater. The high-temperature acid gas system from the heater 11 is sent to the bag filter 15 through the pipe 12. In the acid gas piping 12, the acid gas treatment agent is supplied from the chemical metering machine 13 via the piping 14. A pressure gauge P1 is provided at the inlet of the bag filter of the pipe 12, and the inlet pressure is measured. The gas subjected to the dust collection treatment by the bag filter 15 passes through the piping 16 and is sequentially treated by the cooling tower 17 and the neutralization tower 18, and is passed through the piping by an induced draft fan 19 20, 21 are discharged. A pressure gauge P2 is installed at the outlet of the bag filter 15 of the piping 16, and the outlet pressure is measured.

The test conditions are as follows.

Air volume: 0.43m ³ /min

Bag filter filtration area: 0.43m ²

Filter speed of bag filter: 1m/min

Bag filter dust collection room temperature: 180℃

Addition amount of medicine: 116g/m ³

Pressure setting: 0.5kPa

(When the pressure loss of the bag filter reaches 0.5kPa, it will be automatically backwashed)

Test time: 70 minutes

The less the number of backwashes during the test period, the better the peelability and the increase in pressure loss of the bag filter is prevented.

Table 1 shows the following items.

Example 1 was shown in a load test and exhibited a more excellent effect of preventing consolidation than the comparative example, but the pressure loss of the bag filter was higher than that of the comparative example.

In Example 2, the blending ratio of the anti-consolidation agent was lower than that in Example 1, but it showed the same junction prevention effect and pressure loss as the comparative example. Compared with the comparative example, the mixing ratio of the anti-consolidation agent is smaller, and the mixing ratio of the crushed sodium bicarbonate as an acid gas treatment component is improved.

In Example 3 and Example 4, the load test showed a superior effect of prevention of consolidation compared to the comparative example, and the pressure loss of the bag filter was the same as the comparative example. Compared with the comparative example, it has a blending ratio of the anti-consolidation agent which is smaller, and is a blend of crushed sodium bicarbonate as an acid gas treatment component Than the advantage of being improved.

Example 5 was the result of using two kinds of anti-consolidation agents, but showed the same anti-consolidation effect and pressure loss as the comparative example. Compared with the comparative example, the mixing ratio of the anti-consolidation agent is smaller, and the mixing ratio of the crushed sodium bicarbonate as an acid gas treatment component is improved.

Refer to Examples 1 and 3. The amount of carbon black or hydrophobic silica is small, and the effect of preventing consolidation is poor but the pressure loss is small.

Reference examples 2 and 4 are based on a large amount of carbon black or hydrophobic silica, which has a very high effect of preventing consolidation but a large pressure loss.

Although the present invention will be described in detail in a specific manner, various changes can be made without departing from the intention and scope of the present invention, and it is obvious to those having ordinary knowledge in the technical field to which they belong.

This application is based on the Japanese invention patent application 2015-228838 filed on November 24, 2015, and the entire application is cited and used in this application.

11‧‧‧heater

12‧‧‧Piping

13‧‧‧Pharmaceutical dosing machine

14‧‧‧Piping

15‧‧‧Bag filter

16‧‧‧Piping

17‧‧‧cooling tower

18‧‧‧ Neutralization Tower

19‧‧‧Induced draft fan

20‧‧‧Piping

21‧‧‧Piping

P1‧‧‧pressure gauge

P2‧‧‧pressure gauge

Claims (7)

An acid gas treatment agent composed of sodium bicarbonate and a powder mixture of sodium bicarbonate and a solidification inhibitor, characterized in that the solidification inhibitor is carbon black, or carbon black and hydrophobic silica. The acid gas treatment agent as described in item 1 of the patent application range, wherein the average particle diameter of the carbon black is 0.1 to 10 μm. The acid gas treatment agent as described in item 1 or 2 of the patent application range, wherein the average particle size of the sodium bicarbonate is 5 to 30 μm. The acid gas treatment agent according to item 1 or 2 of the patent application scope, wherein the content of the anti-consolidation agent is 0.1 to 2.0% by weight. The acid gas treatment agent as described in item 3 of the patent application scope, wherein the content of the anti-consolidation agent is 0.1 to 2.0% by weight. An acid gas treatment method, characterized by adding the acid gas treatment agent described in any one of claims 1 to 5 to exhaust gas containing acid gas. An anti-consolidation agent of sodium bicarbonate is made of carbon black, or carbon black and hydrophobic silica.

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