VOC Waste Gas Treatment Solution
2024-10-30
Details of the VOC Waste Gas Treatment System Solution
With the rapid development of economy, a large number of organic volatile compounds VOCs, in recent years, volatile organic compounds (VOCs) has become one of the main sources of air pollutants, which has caused a great threat to human health and the balance of the ecosystem, the end of the governance of VOCs has attracted wide attention from the society.
On the basis of the existing single terminal air treatment technology, the principle, process flow, research status and development prospect of the combined adsorption concentration-catalytic combustion technology suitable for large waste air volume and low concentration of VOCs are discussed in detail.
VOCs Gas mainly cause harm to the atmosphere:
(1) Some are toxic and carcinogenic and endanger human health;
(2) Hydrocarbons and nitrogen oxides in VOCs react to generate ozone under the action of ultraviolet light, which can lead to atmospheric photochemical smog events and endanger human health and plant growth;
(3) Participate in the formation of secondary aerosols in the atmosphere. Most of the secondary aerosols are fine particles, which are not easy to settle. They can remain in the atmosphere for a longer time and have strong scattering force to light, which can significantly reduce atmospheric visibility;
At present, many urban atmospheric environment has shown regional haze pollution, ozone and acid rain and other three complex air pollution characteristics, and VOCs is one of the most important booster agents.
VOCs gas common treatment technology:
VOCs governance has been urgent, the current VOCs gas treatment technology is mainly divided into two categories:
(1) Control at the source, specifically refers to the measures to prevent or reduce VOCs as emissions in the production link, which is the best method to control organic waste gas pollution. However, due to the limitation of the technical level, it will inevitably discharge and leak different concentrations of organic exhaust gas to the environment, which is difficult to achieve.
(2) The governance method of controlling and eliminating VOCs gas at the end of production can be divided into two categories: recycling technology and destruction technology.
Recovery technology: is the use of physical methods to recover VOCs gas non-destructive methods, mainly activated carbon adsorption method, condensation method, membrane treatment method and so on. This kind of method can not only effectively control the emission of VOCs, but also recycling can save resources and bring economic benefits, so it is getting more and more attention.
Destruction technology: that is, through chemical or biological reaction process to make VOCs waste gas oxidation decomposition into non-toxic or low-toxic substances of destructive methods, the main technologies are combustion, photocatalytic degradation, plasma technology, biodegradation and so on.
The VOCs waste gas treatment technology is a single treatment process, according to the specific situation and requirements of VOCs waste gas emissions, select the appropriate process; Because of the wide variety of VOCs, complex components, different properties, in many cases, the use of a purification technology is often difficult to meet the governance requirements, and very uneconomic. Using the advantages of different unit treatment technologies, the combined treatment process can not only meet the emission requirements, but also reduce the operating cost of the equipment.
Principle technology of Zeolite Rotor Concentration + Catalytic Combustion Systems :
The first technology used to deal with VOCs gas is adsorption method, among which the most commonly used and more typical is activated carbon adsorption, activated carbon adsorption method for adsorption and treatment of halogen smoke and benzene series of technology has been very common in the industry. The main principle of adsorption method is to use porous materials with large specific surface area as adsorbent. When VOCs gas flows through the adsorbent, due to the large specific surface area of the adsorbent, VOCs molecules are trapped on the inner surface of the micropore by the adsorbent, so as to achieve the effect of gas purification. As a new combination and efficient VOCs adsorption treatment technology, zeolite wheel Rotor Concentrator + catalytic combustion technology has been widely used in foreign countries.
(1) Type of adsorbent
Adsorption material is the core of the wheel technology, commonly used activated carbon and zeolite molecular sieve two. Activated carbon has rich micropores, large specific surface area, strong adsorption capacity, fast speed, is widely used in the wheel technology. Activated carbon as an adsorbent to treat waste gas, its adsorption capacity is large, low cost, but its pore is easy to plug, and activated carbon itself has a certain flammability, easy to catch fire when desorption, will constitute a certain safety hazard, does not meet the requirements of safety production, will be affected in practical application.
Zeolite molecular sieve is a kind of hydrate material with a specific skeleton structure of crystalline aluminum silicate metal salt. The general chemical formula is as follows:
[ (A102) x - (SiO2)y] - zH20o
Where M represents cation, m represents the number of valence states, z represents the number of hydration, x and ten thousand are integers, after the structure is activated, A. The water in the head will disappear, and the remaining components will move to form a cage structure with an aperture of 3~10Å.
The selective adsorption capacity of zeolite molecular sieve is mainly due to the regular structure. Zeolite molecular sieve aperture arrangement rules, uniform distribution, the selection of adsorption is mainly because different zeolite aperture size is different, under normal circumstances, only molecular dynamic diameter less than the molecular sieve aperture molecules will be adsorbed by the molecular sieve.
There are also large differences in the skeleton structure and pore size of different types of molecular sieves, and the skeleton structure of molecular sieves has variability within the range of degrees, so some molecules with molecular dynamic diameter slightly greater than the pore size can also be adsorbed by it, but the adsorption rate and adsorption capacity will be significantly reduced.
Because there are cations in the structure and the skeleton structure is negatively charged, it is the molecular sieve itself with polarity. The cation of zeolite molecular sieve will generate a strong positive electric field, in order to attract the negative center of polar molecules, or polarizable molecules by zeolite molecular sieve electrostatic induction after polarization.
Therefore, zeolite molecular sieves can adsorb molecules with strong polarity or easy polarization but kinetic diameter slightly larger than their pore size. Because the molecular sieve has a special pore structure so that it has special performance, under the condition of high temperature and low pressure can also play its adsorption capacity. At present, the types of molecular sieve often used for adsorption are 13X, NaY, mercerite and ZSM-5.
Introduction of zeolite wheel principle
The study concluded that: if the processed corrugated and flat ceramic fiber paper using inorganic bonding way to make a honeycomb wheel, and then the zeolite with water absorption on the channel of the wheel, the wheel will become an absorbent wheel, after experiments proved that the adsorption wheel for VOCs purification treatment is very effective.
The concentration zone of zeolite runner can be divided into three parts: treatment zone, regeneration zone and cooling zone. The concentration runner runs continuously in each zone. VOCs organic waste gas is filtered through the pre-filter, and then through the treatment area of the concentration runner device.
VOCs in the treatment area are removed by adsorption of adsorbent, and the purified air is discharged from the treatment area of the concentration runner. The organic waste gas VOCs adsorbed in the concentration runner are desorbed and concentrated to 5~15 times by hot air treatment in the regeneration area.
The concentrated runner is cooled in the cooling zone, and the air through the cooling zone is heated and used as recycled air to achieve the effect of purification and energy saving.
Catalytic oxidation process:
The catalytic combustion process is carried out in a catalytic combustion unit. The organic waste gas is preheated to 200-400 °C through the heat exchanger, and then enters the combustion chamber. When passing through the catalyst bed, the molecules of hydrocarbons and the oxygen molecules in the gas mixture are adsorbed on the surface of the catalyst and activated respectively. Because surface adsorption reduces the activation energy of the reaction, hydrocarbons are rapidly oxidized with oxygen molecules at lower temperatures to produce carbon dioxide and water.
Zeolite Rotor adsorption concentration - catalytic combustion process:
The basic idea of zeolite wheel concentration catalytic combustion technology, the VOCs in the industrial waste gas with low concentration and large air volume are separated and concentrated by adsorption separation method, and the polluted air with high concentration and small air volume after concentration is decomposed and purified by combustion method, commonly known as adsorption separation concentration + combustion decomposition and purification method.
The adsorption runner with honeycomb structure is installed in the shell divided into adsorption, regeneration and cooling zones, and rotates slowly at a speed of 3 ~8 revolutions per hour under the drive of the speed regulating motor.
The three zones of adsorption, regeneration and cooling are respectively connected with the air passages of treatment air, cooling air and regeneration air. Moreover, in order to prevent the air leakage between the wind channeling and the circumference of the adsorption runner and the shell between each zone, the partition plate and the adsorption runner, the circumference of the adsorption runner and the shell are equipped with high temperature resistant, solvent resistant fluoro rubber sealing material.
No. 1 fan drives VOCs containing exhaust gas through area a of the runner, which is the adsorption area. Different adsorption materials can be filled in the runner according to different targets. The a region of VOCs adsorbed comes to the b region for desorption with the rotation of the runner. The high temperature air flow through heat transfer 1 will desorb the VOCs adsorbed on the runner, and reach the ignition temperature through heat transfer 2, and then enter the catalytic combustion chamber for catalytic oxidation reaction. Since the runner needs to be adsorbed after desorption, a cooling area c is set next to the desorption area to be cooled by air, and the cooled warm air becomes hot air for desorption through heat transfer 1.
For the current chip manufacturing, LCD panel industry, semiconductor industry, printing industry, coating industry and other industrial production fields. Its fixed production method must use a large number of organic solvents, used as cleaning agent, photoresist, stripping liquid, diluent, etc., in this process will produce a large number of organic waste gas, these organic waste gas are large air volume, low concentration of waste gas, so in order to efficiently treat this kind of waste gas containing VOCs components, Zeolite rotor adsorption and concentration method is the most effective treatment method at present.
Application Range of Zeolite Rotary Concentration + Catalytic Combustion Systems:
Zeolite rotary concentration and catalytic combustion systems have a wide range of applications, covering a wide range of industries and exhaust gas treatment conditions. This innovative technology is mainly used in waste gas treatment conditions with low concentration and large air volume, and is suitable for a variety of industrial applications.
One of the main advantages of the zeolite rotor concentrator is its ability to treat waste gases that do not contain halogens such as S, N, Cl, F, etc. If these components are present, they can be treated in the pretreatment stage before combustion to ensure that no new exhaust gas components are produced after the combustion process.
In addition, the boiling point of the exhaust gas cannot be too high in order to be effectively treated using this system. If the boiling point exceeds 300°C and is exposed to hot air, the organic waste gas adsorbed on the zeolite molecular sieve will not be desorbed for a long time, affecting the efficiency of the treatment process.
This advanced technology is suitable for a variety of industries, including chemical plants, painting facilities, pharmaceutical companies, electronics factories, furniture manufacturers, packaging and printing companies, and painting facilities. It effectively treats organic solvents and organic waste gas emissions from these diverse industries, making it a versatile and valuable solution for companies looking to improve their waste gas treatment processes.
Notably, waste gases can be adsorbed and then desorbed by zeolites, making them suitable candidates for treatment. However, if the exhaust gas contains S, N, Cl, F and other components, secondary pollutants will be produced after combustion, and it is not suitable for catalytic combustion treatment.
In summary, zeolite rotary concentration and catalytic combustion systems have a wide range of applications and provide reliable and efficient solutions for VOCs waste gas treatment in various industries. Its ability to handle high air volumes and low concentrations makes it a valuable asset when looking to improve exhaust treatment processes.