How to control the gas of asphalt mixing plant

Firstly, the exhaust source:

After stirring the asphalt, the flue gas through the bag filter to remove dust, soot after the purification of asphalt flue gas.

Secondly, the exhaust characteristics:

1. The exhaust composition:

Flue gas contains a variety of organic compounds, including carbocyclic hydrocarbons, cyclic hydrocarbon derivatives and other compounds. The particle size is mainly between 0.1 and 1.0 μm, the smallest is only 0.01 μm, and the maximum is about 10.0 μm. The main way to harm human health is attached to the 8 um below the dust, through the respiratory tract inhalation. Therefore, the asphalt flue gas purification treatment, so that emissions meet the atmospheric environmental standards, is very necessary.

2. The harm to the human body:

Asphalt and its flue gas on the skin and mucous membranes are irritating, phototoxic effect and cause tumor effect. The body inhaled asphalt smoke will feel dizzy, head swelling, headache, chest tightness, fatigue, loss of appetite, systemic symptoms and eye, nose, throat irritation symptoms.

3. Flue gas characteristics:

1) Small particle size: Asphalt flue gas is mainly 0.1 ~ 1.0 um tar fine mist in the form of the existence of the smallest only 0.xn--01m-yyc.

2) higher flue gas temperature: asphalt flue gas temperature is generally higher than 100 ℃;

3) have a fire, explosion and other unsafe risks.

Thirdly, the commonly used processing technology:

Asphalt flue gas treatment methods are many kinds of commonly used asphalt flue gas purification methods are the following.

1. Mechanical separation method:

When the asphalt flue gas contains dust, spray it with steam or water mist to increase the diameter of the flue gas particles, and then in the settling chamber or cyclone dust and particles separated, so as to achieve the purpose of purifying asphalt flue gas. As the dust particle size is too small, even if the use of collision to increase it, but still less than the appropriate diameter of cyclone dust collection, dust collection effect is poor, so the mechanical separation method less.

2. Condensation method:

Condensation is used as an auxiliary means for the treatment of asphalt flue gas with other purification methods (eg adsorption, absorption, etc.). Asphalt flue gas through the condensation, can increase the particle size of fumes in the flue gas, which is conducive to the purification of asphalt flue gas.

3. Absorption and purification method:

Absorption and purification method commonly known as washing method, is a commonly used industrial waste gas treatment methods. It is the use of exhaust gas in the mixed components in the selected absorbent (gasoline, diesel, etc.) in the solubility of different, or a component and the active component of the reaction react to achieve a way to purify the exhaust gas.

Absorption and purification method used in the treatment of asphalt flue gas, is the flue gas in the gaseous pollutants (actually 0.1 ~ 1.0 um tar fine mist particles) transferred to the liquid phase (absorbent), so as to achieve the purification of flue gas the goal of. For the asphalt concrete mixing station through the dry bag after the dust is relatively small amount of asphalt flue gas treatment, water as the absorbent is the most cost-effective absorbent.

Asphalt flue gas in the fine mist particles are adsorbed by water, the basic insoluble in water, nor will the reaction produce a large number of new compounds, the vast majority of the formation of floating oil floating in the water, accumulated to a certain extent can be collected after the incorporation Coal as fuel. After repeated cycles, the concentration of emulsion in the water increases, will reduce the treatment effect.

4. Filtration:

Filtration is the use of porous media, and asphalt flue gas fog particles in the collision of flue gas tar fine particles adsorbed down, so that the asphalt flue gas purification method. In principle, it should belong to the adsorption method is one of the most widely used asphalt flue gas treatment methods.

Bag filter is one of the commonly used methods. But for the asphalt flue gas purification, need to filter bag with oil, water, heat, corrosion resistance. Although the high efficiency of purification, but can not filter the dust below 0.5 microns.

5. Adsorption purification method:

The adsorption purification method is the use of porous solid (adsorption filter) will fluid (gas or liquid) mixture of one or more components accumulated or condensed on the surface, to achieve the purpose of separation operations, according to the adsorption filter surface and adsorbent Between the different forces, divided into physical adsorption and chemical adsorption of two categories.

Adsorption purification for asphalt flue gas treatment is physical adsorption. Physical adsorption is caused by intermolecular gravitational pull, commonly referred to as "van der Waals force", which is the general term for directional, induced and dispersive forces. Which is characterized by the adsorbent and the adsorbate does not occur between the chemical action, is a reversible process, that is, adsorption and desorption. Physical adsorption is generally not affected by temperature, but the adsorption capacity decreases with increasing temperature, so the pretreatment and purification of the asphalt flue gas before the condensation treatment can improve the purification effect.

Selection of the appropriate adsorption filter is one of the key to adsorption purification method. As the adsorption filter should generally have the following characteristics: a larger adsorption capacity, that is, adsorption filter should be loose solid foam; has a good selectivity in order to achieve the purpose of purifying one or several pollutants; Regeneration characteristics and wear resistance, there is acid, alkali, water, high temperature adaptability.

Asphalt flue gas adsorption purification of the main equipment for the fixed bed adsorber, generally cylindrical vertical structure, built-in grid or orifice plate, which placed filter, asphalt smoke from the container through, through the filter gap, After adsorption or discharge into the next process. The design and calculation of fixed bed adsorber are mainly considered from the aspects of adsorption equilibrium and adsorption rate. The factors affecting the adsorption equilibrium and adsorption rate of fixed bed are mainly reflected in the mass transfer area, The time to reach the break point and break the point when the bed of the filter material saturation and other aspects of the data, more complex.

6. Electrostatic capture method:

Due to the specific resistance of asphalt. No corrosive effect on metal. After the capture was liquid, electrostatic trapping purification of asphalt flue gas has a good effect.

7. Combustion method:

It's the direct introduction of asphalt flue gas furnace dedicated furnace incineration, after a certain period of high temperature incineration, can be more thorough purification of asphalt flue gas. This treatment is used more in the tail gas treatment of the oxidized asphalt plant, but the equipment has a large investment and high operating costs. And has a great security risk.

8. Low temperature plasma dust removal technology:

Low temperature plasma technology as an efficient and new dust removal technology to achieve the dust, desulfurization, denitrification integration, dust purification rate can reach 98%, organic volatile VOCS removal rate: ≥ 85%. Can be collected 0.001 ~ 0.xn--01m-yyc ultra-fine dust particles.