Waste gas treatment technology?

In recent years, the field of air pollution control by the attention of the industry, especially the VOCs (volatile organic compounds) governance, the provinces have introduced the relevant policies, Powder coating equipment will introduce 7 kinds of VOCs waste gas treatment technology, are as follows:

First, VOCs waste gas treatment technology - thermal destruction method

The thermal destruction method refers to the organic gas directly and auxiliary combustion, also known as VOC, or by using a suitable catalyst to accelerate chemical reactions of VOC, to reduce the concentration of organic matter, which is no longer a process hazard.

The heat destruction method is better for the lower concentration of organic waste gas, so it has been widely used in the treatment of low concentration exhaust gas. This method can be divided into two kinds, direct flame combustion and catalytic combustion.

The heat treatment efficiency of direct flame combustion on organic waste gas is relatively high, which can reach 99% in general. Catalytic combustion means accelerating the rate of chemical reaction of organic waste gas under the action of catalytic bed. This method is less than direct combustion. It is the first choice for high concentration and small flow purification of organic waste gas.

Two, VOCs waste gas treatment technology - adsorption method

The adsorption method in organic waste gas is mainly applicable to low concentration and high flux organic waste gas. At this stage, this method of organic waste gas treatment has been quite mature, energy consumption is relatively small, but the processing efficiency is very high, but also can thoroughly purify harmful organic waste gas. Practice has proved that this method is worthy of popularization and application.

However, this method also has some defects, it requires a relatively large volume of equipment, and the process is more complex; if there are a lot of impurities in the exhaust, it is easy to cause poisoning of staff. Therefore, the key to the treatment of exhaust gas with this method is adsorbent. At present, the adsorption method for the treatment of organic waste gases, and the use of activated carbon, mainly because of the fine pore structure of activated carbon, adsorption is relatively strong.

In addition, after the treatment of iron oxide or ozone, the adsorption capacity of activated carbon will be better, and the treatment of organic waste gas will be more safe and effective.

Three, VOCs waste gas treatment technology - biological treatment

From the basic principle of the treatment of speaking, using biological treatment of organic waste gas, is a physiological process of using microorganisms to convert organic harmful substances in exhaust gas into simple inorganic compounds, such as CO2, H2O and other simple inorganic compounds etc.. This is a harmless way to treat organic waste gases.

In general, a complete biological treatment of organic waste gas processes consists of 3 basic steps:

(a) organic pollutants in organic waste gases are first contacted with water and dissolved rapidly in water;

(b) dissolved organic matter in a liquid membrane can be gradually diffused into the biofilm in the case of low liquid concentration, and then absorbed by microorganisms on the biofilm;

(c) organic waste gases absorbed by microorganisms will degrade in their own physiological metabolism and eventually turn into chemical compounds that do not harm the environment.

Four, VOCs waste gas treatment technology PSA adsorption separation and purification technology

Technology and purification of PSA is characteristic points can be adsorbed on the solid materials by gas group, and in the organic waste gas separation purification device, gas pressure there will be some changes, the pressure changes to the treatment of organic waste gas.

The main application of PSA technology is physical method, through the physical method to achieve the purification of organic waste gas, the use of materials is mainly zeolite molecular sieve. Zeolite has some advantages in two aspects: adsorption selectivity and adsorption capacity. Under certain temperature and pressure, the zeolite can adsorb organic components in organic waste gas, and then transfer the remaining gas to the next link.

In the adsorption of organic waste gas, through a certain process will be transformed, keep and improve the regeneration capacity of the adsorbent, and the adsorbent can make again put into use, and then repeat the process steps, the cycle repeated, until the organic waste gas purification.

In recent years, this technology has been applied in industrial production and has a good effect on gas separation. The main advantages of the technology are:

Low energy consumption, low cost, automation of process operation and high purity of the mixture after separation and purification, environmental pollution and so on. The technology has a good effect on the recovery and treatment of gas with a certain value, and has a broad market prospect. It will become the direction of the development of organic waste gas treatment technology in the future.

Five, VOCs waste gas treatment technology - oxidation method

Thermal oxidation is the most suitable treatment technique for toxic, harmful, and VOC free recycling. The basic principle of oxidation process: VOC and O2 oxidation reaction, the formation of CO2 and H2O, the chemical equation is as follows:

From the chemical reaction equation, the oxidation reaction is similar to the chemical process of combustion, but because of the low concentration of VOC, no visible flame can be produced in the chemical reaction. In general, the oxidation process ensures a smooth operation of the oxidation by two methods:

A) heating. The organic waste gas containing VOC reaches the reaction temperature;

B) use catalyst. If the temperature is relatively low, the oxidation reaction can be carried out on the catalyst surface.

Therefore, the oxidation process for organic waste gas treatment is divided into the following two methods:

A) catalytic oxidation process. At this stage, there are two kinds of catalysts used in catalytic oxidation process, namely noble metal catalysts and non noble metal catalysts. Noble metal catalysts including Pt, Pd and so on, they are attached to the fine particles in the form of catalyst carrier and catalyst carrier, usually metal or ceramic honeycomb, or bulk filler; non noble metal catalyst is mainly composed of transition metal oxides, such as MnO2, and the adhesive after a certain proportion, and then made the catalyst.

In order to effectively prevent catalytic loss of catalytic activity after the catalyst, the catalyst poisoning substances must be thoroughly removed, such as Pb, Zn and Hg. The catalytic oxidation process shall not be used if the catalyst, poison, and cover substance in organic waste gases cannot be removed. VOC.

B) thermal oxidation process. There are three kinds of heat oxidation method: thermal combustion type, inter wall type and regenerative type. The main difference between the three methods is heat recovery. These three methods can catalyze the combination of chemical reactions and reduce the reaction temperature.

A thermal combustion type heat oxidizer usually refers to a gas incinerator. The gas incinerator is composed of three parts: a combustion supporting agent, a mixing zone and a combustion chamber. Among them, accelerant, such as natural gas and oil, is the auxiliary fuel in the combustion process, combustion heat generated within the mixing zone furnace can preheat the VOC exhaust gas, after preheating can provide enough space for treatment of organic waste of time, and ultimately harmless treatment of organic waste gas.

Under the oxygen supply sufficient condition, the reaction degree of oxidation - VOC removal rate mainly depends on the "three T conditions": reaction temperature (Temperat), time (Time) and turbulent mixing (Turbulence). The three T conditions are interrelated, and within a certain range, the improvement of one condition can reduce the other two conditions. The disadvantage of the thermal combustion heat oxidizer is that the auxiliary fuel price is high, which leads to higher operating cost.

Recuperative thermal oxidizer refers to the thermal oxidation device, adding recuperative heat exchanger, and the gas temperature at the heat transfer chamber of the exhaust gas to oxidation device import is relatively low, preheating can facilitate the oxidation reaction after the completion. At this stage, the wall type heat exchanger heat recovery rate of up to 85%, so the auxiliary fuel consumption significantly reduced.

In general, surface type heat exchanger has three forms: tube, shell and plate. Because the heat oxidation temperature must be controlled within the range of 800 DEG C to 1000 DEG C, therefore, the