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

Classification and advantages and disadvantages of asphalt flue gas recovery and treatment methods
Asphalt smoke 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. There are four organic waste gas treatment methods that can be applied to this low concentration and highly dispersed asphalt smoke. The following is a brief description:
1、 Combustion method.
The combustion method has two main factors: the higher the concentration of asphalt smoke, the more favorable it is for combustion, and the control of combustion temperature and time.
The combustion method is the combustion of hydrocarbons, combustible carbon powder, and tar droplets in flue gas, which are decomposed into carbon dioxide and water. However, this method requires high combustion temperature, a certain concentration of combustion materials, strict control of combustion time, and is prone to incomplete combustion and secondary pollution, resulting in high investment and operating costs.
2、 Electric capture method.
This method is based on some properties of the electrostatic field. Asphalt smoke comes into direct contact with organic liquids (washing oil), causing tar particles and smoke to condense, achieving the goal of purifying asphalt smoke.
（1） Advantages:
1. Recycled asphalt is tar like, soluble in benzene or cyclohexane, and can be returned to the production system or used as fuel;
2. The system has low resistance, low energy consumption, and low operating costs.
（2） Disadvantages:
1. High smoke temperature requirements;
2. The capture efficiency of dry electrostatic precipitators for gas-phase components is almost zero, while wet electrostatic precipitators can capture gaseous asphalt, but they increase the cost of sewage treatment equipment and maintenance;
3. Asphalt is flammable and not suitable for purifying mixtures of carbon dust and asphalt smoke;
4. Long term operation reduces purification efficiency;
5. Large one-time investment and large land area.
3、 Adsorption method.
This method utilizes high-voltage electrostatic capture of tar, and applies direct current high voltage between the corona electrode (negative electrode) and the precipitation electrode to discharge the corona electrode. The flue gas ionizes and produces a large number of positive and negative ions. When the positive and negative ions move towards the corona electrode and precipitation electrode, they encounter tar droplets and make them charged. The droplets are attracted by the electrode and removed. The electric capture method has certain requirements for smoke concentration and smoke to dust specific resistance, and is widely used in asphalt smoke treatment.
（1） Advantages
1. Simple process;
2. High purification efficiency, adsorbent does not require regeneration and can be directly returned to the production system;
3. Low investment and low operating costs;
4. Easy to operate, no secondary pollution.
（2） Disadvantages
1. The system resistance is too high, up to 2000Pa;
2. Large footprint and long adsorption tubes;
3. The bag dust removal area for recycling adsorbents is large.
4、 Absorption method.
Using various powder materials with high porosity and large specific area (such as coke powder, alumina, activated carbon, dolomite powder, etc.) as adsorbents for purifying asphalt flue gas, the method is to mix the adsorbent with the flue gas and purify harmful components in the gas phase through the molecular absorption of the adsorbent.
（1） Advantages
1. The equipment is simple and easy to maintain;
2. Low system resistance;
3. Low energy consumption;
4. Low operating costs.
（2） Disadvantages
1. Secondary pollution;
2. The purification efficiency is not high.