JP2009112957A - Method for treating soot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating soot which can effectively remove soot containing minute solids produced by an incomplete combustion reaction. <P>SOLUTION: In the method for treating the soot, the soot is contacted with solid particles which are suspended in a suspension and has a number average particle size of 5-40 μm. The soot is contacted with the solid particles in the suspension by supplying the soot-containing gas into the suspension or spraying the soot-containing gas with the suspension. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for treating soot, and more particularly to a method for treating soot that removes soot containing fine solids generated by incomplete combustion reaction.

  Various methods have been used for the soot treatment method for removing soot containing solid matter generated by an incomplete combustion reaction. As a soot treatment method, a wet soot treatment method is used together with a dry soot treatment method using a bag filter, an electrostatic precipitator, etc. In the wet treatment method, a chemical reaction by contact with a chemical solution or adsorption by activated carbon or the like is used. The processing method is common.

For example, as a wet processing method, a method of adsorbing and removing soot by spraying carbon-containing water in a mist from a nozzle having a diameter of about 0.001 mm into a flue has been proposed (for example, see Patent Document 1).
Although this method utilizes the adsorption performance of fine carbon particles, the performance of removing smoke has not been sufficient.
JP 2006-198458 A

  The present invention provides a soot treatment method that has a large soot treatment performance compared to the case of using fine particles having adsorption characteristics such as activated carbon as solid particles suspended in a liquid in the soot treatment method. This is a problem.

The present invention is a soot treatment method in which soot is treated by bringing it into contact with solid particles having a number average particle size of 5 to 40 μm suspended in the suspension.
In the method for treating soot, the contact with the solid particles in the suspension is performed by supplying the gas to be treated containing smoke into the suspension or by injecting the suspension into the gas to be treated.
Further, in the above smoke treatment method, the solid particles are at least one kind of particles selected from calcium carbonate, calcium hydroxide, aluminum oxide, and carbon.

    By adopting the method of the present invention, it is possible to effectively carry out the smoke removal treatment, which has been difficult to process by a wet method such as a gas-liquid contact gas processing apparatus.

The inventors pay attention to a phenomenon in which the smoke becomes more transparent as time passes if the smoke is left in a sealed container. This is thought to be due to the fact that the dust loses kinetic energy due to collision with the wall of the container and cannot float.
Therefore, by using a suspension in which solid particles are suspended in a liquid instead of a vessel wall on which soot particles collide, efficient collision of soot particles by fine solid particles in the suspension It has been found that it is possible to quickly remove soot particles that can achieve the above.

  In the present invention, since smoke particles are removed by collision with the solid particles in the suspension, the higher the concentration of the solid particles suspended in the suspension in contact with the smoke, the higher the concentration. A smoke effect can be obtained.

 In addition, when smoke is introduced into a suspension in which solid particles are suspended and the smoke bubbles are brought into contact with the solid particles, the smaller the bubbles and the higher the liquid column of the suspension, the more the gas and liquid. The interfacial area and the contact time are increased, and the contact efficiency can be increased.

In the present invention, water that is easy to handle can be used as the suspension. Moreover, various solid particles can be used as the solid particles suspended in water. Specifically, particles such as calcium carbonate, calcium hydroxide, aluminum oxide, silicon oxide, and sand that have low solubility in water, are easily available, and are easy to handle can be used.
Of these particles, calcium carbonate has an excellent effect, but when the pH is lowered due to absorption of carbon dioxide contained in the smoke and the suspension is acidified, the calcium carbonate dissolves and suspends the particles. The effect cannot be obtained. Therefore, when operating for a long time, it is necessary to manage the pH and replace the suspension.

The particle size of the solid particles is preferably 5 to 40 μm in terms of number average particle size, and if it is smaller than 5 μm or larger than 40 μm, the effect of removing soot is reduced.
The concentration of the suspension is preferably 2% by mass to 20% by mass, and if it is less than 2% by mass, the effect of smoke suppression is small, and if it is greater than 20% by mass, it is difficult to circulate the suspension. Become.

  The method for removing smoke from smoke according to the present invention can be effectively used when removing smoke generated by burning or incomplete combustion of a fuel or a combustible substance in a wet manner. In addition to the combustion of fuel, it is also useful for removing soot generated by cutting a combustible member such as a synthetic resin.

The soot removal method of the present invention can be carried out by various methods as long as the suspension and the soot-containing gas can be brought into contact with each other.
For example, it can be realized by a method of introducing smoke into a suspension in which solid particles are suspended, a method of using a device in which a suspension in which solid particles are suspended in smoke is dropped and brought into contact.
In addition, when the suspension is dropped into a shower and brought into contact with the smoke, the smaller the amount of droplets to be showered, the greater the amount of the droplets to be showered, the greater the interface area and contact time between the smoke and the solid particles, and the higher the contact efficiency. Becomes higher.

The present invention will be described below by showing experimental examples and comparative examples.
Example 1
FIG. 1 illustrates a method for collecting soot used for soot removal.
In the generation chamber 2 of the soot generation device 1, 5 g of smoke smoke chip 3 made of raw material is placed and heated by the electric heater 4 provided at the lower part to be flamelessly combusted. The soot was circulated until the soot was made uniform in the path of the soot generating device including the 500 ml capacity collecting container 7, and soot was collected.

FIG. 2 shows a method for testing the smoke removal process.
Smoke 6 was supplied from the collection container 7 into the suspension 11 of the gas-liquid contact container 10 through the circulation pump 8 and the flow meter 9. In addition, a bypass pipe 12 is provided on the outlet side of the circulation pump 8 to vent the spectrophotometer 13, and the outlet side of the spectrophotometer is connected to the inlet side of the circulation pump 8 to change the concentration of soot over time. Was measured.

100 ml of a calcium hydroxide suspension having a number average particle diameter of 16.5 μm and a concentration of 5% by mass is placed as a suspension in a 250 ml gas-liquid contact container, and the aeration flow rate is 250 ml / min from the soot collection container. The optical density at a wavelength of 550 nm was measured with a spectrophotometer (UV-8000 manufactured by Tosoh Corporation). The particle size was measured with a laser particle size distribution measuring device (SALD-2000 manufactured by Shimadzu Corporation).
The optical density at the start of the gas-liquid contact time is normalized as 10, and the optical density for the elapsed time from the start of contact is shown in FIG.
Moreover, it measured similarly to Example 1 except having replaced the calcium hydroxide with the number average average particle diameter of 7.9 micrometer calcium carbonate, and the result is shown in FIG.

Comparative Example 1
Instead of the suspension of the gas-liquid contact container of Example 1, only water was put into the gas-liquid contact container for comparison with the smoke removal effect by water, and the measurement was performed in the same manner as in Example 1. 3 shows.
Moreover, in order to compare with the smoke removal effect by a lipophilic substance, only the 5 mass% aqueous solution of polyethyleneglycol (PEG-12) was put, it measured like Example 1, and the result is shown in FIG.

In addition, in order to compare the smoke removal effect by the liquid having high affinity for the oily component in the smoke, only a 5% by mass aqueous solution of a water-soluble cutting oil (S-3985, manufactured by Sakiru) was added, and Example 1 The same measurement is performed and the result is shown in FIG.
Moreover, in order to compare with the smoke removal effect by alkaline aqueous solution, only 5 mass% sodium carbonate aqueous solution was put, it measured like Example 1, and the result is shown in FIG.

Example 2
From FIG. 3 showing the measurement results of Example 1 and Comparative Example 1, it can be seen that the smoke extinguishment of smoke has a primary reaction type appearance.
That is, when the initial concentration of smoke is A (t = 0) and the smoke extinction concentration is x, the smoke concentration at an arbitrary time t is A−x. This can be expressed as a velocity equation.
dx / dt = −d [A−x] / dt (1)
And k = 1 / t · ln [d / [A−x]] (2) where k is a smoke extinction constant.
When equation (1) is integrated with t, equation (3) is obtained.
dx = k · ln [A−x] t (3)

  The natural logarithm of the vertical axis of FIG. 3 was used to determine the smoke extinguishing rate constant (k) with the slope of each point with respect to the time axis. Table 1 shows (k).

table 1
Gas-liquid contact liquid smoke extinction rate constant (k)
Calcium hydroxide suspension -0.051
Calcium carbonate suspension water -0.027
Sodium carbonate aqueous solution -0.006
Water-soluble cutting oil -0.012
Polyethylene glycol aqueous solution -0.005
Water -0.002
From the above results, it was confirmed that excellent smoke removal effect can be obtained by contacting smoke with a suspension in which fine particles are suspended.

Example 3
The particle diameter of the calcium carbonate particles in the suspension was measured in the same manner as in Example 1 except that the number average particle diameters were 6.3 μm, 13.9 μm, 32.8 μm, and 79 μm, and the results are shown in FIG. Show.
In addition, Table 2 shows the smoke extinguishing rate constants obtained in the same manner as in Example 2.

Table 2
Average particle size of calcium carbonate (μm) Smoke-free rate constant (k)
6.3 -0.024
13.9 -0.019
32.8 -0.026
79 -0.012

Example 4
The optical density was measured in the same manner as in Example 1 except that calcium carbonate having a number average particle size of 8.7 μm was used as the suspended particles and the concentration in the suspension was changed, and the results are shown in FIG.
Further, FIG. 6 shows the change in the smoke eliminating rate constant with respect to the concentration change obtained in the same manner as in Example 1.

Example 5
Calcium carbonate and calcium hydroxide dispersed in the suspension used in the above examples are particles that may cause a chemical reaction with smoke components. It was confirmed that smoke removal was possible in the same manner when particles that did not wake were suspended.
That is, water, suspended water containing 5% by mass of calcium carbonate particles having a number average particle size of 7.9 μm, suspended water containing 5% by mass of bamboo charcoal particles having a number average particle size of 6.5 μm, and aluminum oxide particles having a number average particle size of 6.5 μm. About each 5 mass% containing suspension water, it carried out similarly to Example 1, and tested the smoke-removal effect. The result is shown in FIG.

Example 6
In the examples so far, smoke smoke chips made of raw materials, that is, smoke is prepared with a cellulosic material, but in addition to the pyrolyzate of the cellulosic material, the pyrolyzate of synthetic resins and natural fats and oils is also dusty. The smoke removal effect was confirmed for the case of the configuration.
As a synthetic resin, a smoke resin was prepared in the same manner as in Example 5 using a polystyrene resin, and a smoke extinguishing test was performed in the same manner as in Example 5. The result is shown in FIG.

Example 7
Next, protein-derived soot was prepared in the same manner as in Example 1 using wool as a material, and a smoke-removal test was conducted in the same manner as in Example 5. The results are shown in FIG.

Example 8
Then, using a material impregnated with glass fiber with mineral machine oil as a material, a soot derived from oil was prepared in the same manner as in Example 5, and a smoke extinguishing test was conducted in the same manner as in Example 5. As shown in FIG.
From the above results, it was shown that the soot removal method of the present invention has a smoke eliminating effect without depending on the type of the soot raw material.

Example 9
Smoke generated by flameless combustion of the structural plywood by the electric heater is supplied at a flow rate of 13 m ³ / min from the lower smoke inlet 21 of the gas-liquid contact device 20 shown in FIG. The apparatus 23 causes a suspension of calcium carbonate particles having a number average particle diameter of 13.89 μm supplied from the storage tank 24 by the circulation pump 25 to fall in a shower form at a flow rate of 115 L / min. The treated smoke was discharged from the upper exhaust port 26 of the contact device 20, and the suspension discharged from the lower portion of the gas-liquid contact device 20 was collected in the storage tank 24 by the circulation pump 27.
Also, a rayon nonwoven fabric (Kuraray Laurex ZR-1000-30) is attached to the exhaust port 26 as a filter, and the filter after venting the exhaust gas for 1 minute is referred to the non-vented filter. Spectral reflectance was measured by Minolta CM-2002), and the result is shown in FIG.
Further, for comparison, the same measurement was performed for the case where only water was dropped in a shower shape, and the result was shown in FIG.

  By bringing the suspension in which the fine particles are dispersed into contact with the smoke containing smoke, the smoke can be removed into the suspension by causing the smoke to collide with the fine particles. In a wet method such as a gas-liquid contact processing apparatus, It becomes possible to effectively perform the smoke removal treatment of the soot that has been considered difficult.

FIG. 1 is a diagram for explaining a method for collecting soot used in a soot removal test. FIG. 2 is a diagram for explaining a test method for smoke removal processing of smoke. FIG. 3 is a diagram for explaining the smoke removal effect when the suspended particles and solute are changed. FIG. 4 is a diagram for explaining the smoke removal effect when the particle size of the calcium carbonate particles as suspended particles is changed. FIG. 5 is a diagram for explaining the smoke removal effect when the concentration of calcium carbonate particles as suspended particles is changed. FIG. 6 is a diagram for explaining the change of the smoke extinguishing rate constant with respect to the change in the concentration of calcium carbonate particles as suspended particles. FIG. 7 is a diagram for explaining the smoke-extinguishing effect when particles that do not cause chemical reaction with suspended particles are used. FIG. 8 is a diagram for explaining the smoke eliminating effect of smoke generated from plastics. FIG. 9 is a diagram for explaining the smoke eliminating effect of soot generated from protein. FIG. 10 is a diagram for explaining the smoke eliminating effect of soot generated from oil. FIG. 11 is a diagram for explaining the smoke eliminating effect when a gas-liquid contact device having a packed bed is used. FIG. 12 is a diagram for explaining the smoke evacuation speed by the apparatus of FIG.

Explanation of symbols

 1 ... Smoke generator, 2 ... Generation chamber, 3 ... Smoked smoke chip, 4 ... Electric heater, 5 ... Circulation pump, 6 ... Smoke, 7 ... Collection container, 8 ... Circulation pump, 9 ... Flow meter, 10 ... Gas-liquid contact container, 11 ... suspension, 12 ... bypass, 13 ... spectrophotometer, 20 ... gas-liquid contact device, 21 ... smoke inlet, 22 ... packed bed, 23 ... injection device, 24 ... storage tank, 25 ... circulation pump, 26 ... exhaust port, 27 ... circulation pump

Claims (2)

  A soot treatment method comprising treating soot by bringing solid particles having a number average particle diameter of 5 to 40 μm suspended in a suspension into contact with the soot.   The contact with solid particles in the suspension is performed by supplying a gas containing smoke to be treated into the suspension or by injecting the suspension into the gas containing smoke to be treated. 2. The method for treating smoke according to 2.

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