Classification, advantages and disadvantages of asphalt flue gas recovery and treatment methods

Classification, advantages and disadvantages of asphalt flue gas recovery and treatment methods
Asphalt fume is mainly composed of gas and liquid phases. The liquid phase is a very fine volatile condensate with different particle sizes, and the gas phase is a mixture of different gases. For this low concentration and very dispersed asphalt smoke, there are four organic waste gas treatment methods that can be applied. The following is a brief description:
1、 Combustion method.
There are two main factors in the combustion method. The higher the concentration of asphalt smoke, the better the combustion, and the control of combustion temperature and time.
The combustion method is to burn the hydrocarbons, combustible carbon powder and tar droplets in the flue gas and decompose them into carbon dioxide and water. However, this method has high combustion temperature, requires certain concentration of combustor, strict control of combustion time, and is easy to cause incomplete combustion and secondary pollution, and high investment and operation costs.
2、 Electric capture method.
This method is based on some properties of electrostatic field. The asphalt fume directly contacts with the organic liquid (washing oil) to condense the tar particles and soot, so as to purify the asphalt fume.
（1） Advantages:
1. The recovered asphalt is tar-like, soluble in benzene or cyclohexane, and can be returned to the production system or used as fuel;
2. Low system resistance, low energy consumption and low operation cost.
（2） Disadvantages:
1. High smoke temperature requirements;
2. The capture efficiency of dry electrostatic precipitator for gaseous components is almost zero, while wet electrostatic precipitator can capture gaseous asphalt, but it increases the cost of sewage treatment equipment and maintenance;
3. Asphalt is flammable and not suitable for purification of carbon dust and asphalt fume mixture;
4. The purification efficiency of long-term operation is reduced;
5. Large one-time investment and large floor area.
3、 Adsorption method.
This method uses high voltage static electricity to capture tar, and applies DC high voltage between the corona electrode (negative electrode) and the precipitation electrode to make the corona electrode discharge, and the flue gas ionization generates a large number of positive and negative ions. When the positive and negative ions move towards the corona electrode and the precipitation electrode, they encounter tar droplets and make them charged, and the droplets are attracted by the electrode and removed. The electric capture method has certain requirements for flue gas concentration and specific resistance of smoke and dust, and is widely used in asphalt flue gas treatment.
（1） Benefits
1. Simple process;
2. With high purification efficiency, the adsorbent can be directly returned to the production system without regeneration;
3. Low investment and low operating cost;
4. It is easy to operate without secondary pollution.
（2） Disadvantages
1. The system resistance is too large, up to 2000Pa;
2. Large floor area and long adsorption pipe;
3. The bag dust removal area for recovering adsorbent is large.
4、 Absorption method.
Various powder materials with high porosity and large specific area (coke powder, alumina, activated carbon, dolomite powder, etc.) are used as adsorbent for purifying asphalt flue gas. The method is to mix the adsorbent with the flue gas and purify the harmful components in the gas phase through the molecular absorption of the adsorbent.
（1） Benefits
1. Simple equipment and convenient maintenance;
2. Low system resistance;
3. Low energy consumption;
4. Low operating costs.
（2） Disadvantages
1. Secondary pollution;
2. The purification efficiency is not high.

——Author：EBICO