How to choose the process of organic waste gas treatment?

The treatment project of industrial organic waste gas adsorption method consists of main works and auxiliary works. The main project includes waste gas collection, pretreatment, adsorption, adsorbent regeneration and desorption gas post-treatment unit. If the secondary pollutants are produced in the treatment process, the secondary pollutant treatment facilities shall also be included. Auxiliary engineering mainly includes detection and process control, electrical instruments, water supply and drainage and other units.
The site selection and general layout of waste gas treatment facilities shall refer to gb50187 code for general layout design of industrial enterprises. The site selection shall comply with the principles of reducing environmental impact, facilitating construction, operation and maintenance, and reserve fire access and safety protection distance in accordance with fire protection requirements. The arrangement of control equipment shall consider the influence of dominant wind direction to reduce the impact of harmful gas, noise, etc. on the environment.
How to select a routing
Before the selection of process route, the recovery process shall be selected preferentially according to the recovery value and treatment cost of organics in waste gas. The treatment capacity of the treatment project shall be determined according to the treatment capacity of the waste gas, and the design air volume shall be designed according to 120% of the maximum exhaust gas emission. The purification efficiency of the adsorption device shall not be less than 90%.
The process route shall be selected based on the comprehensive analysis of the source, property (temperature, pressure, component) and flow of waste gas. According to the difference between the regeneration mode of adsorbent and the post-treatment mode of desorption gas, typical treatment processes can be selected as follows:
Water vapor regeneration condensation recovery process;
Hot gas (air or inert gas) regeneration condensation recovery process;
Hot air regeneration - catalytic combustion or high temperature incineration process;
Depressurization desorption regeneration - liquid absorption process.
Fixed bed, moving bed (including runner adsorption device) and fluidized bed adsorption device can be used for continuous and stable waste gas, while fixed bed adsorption device should be used for discontinuous or unstable waste gas. When fixed bed adsorption device is used, in-situ regeneration process of adsorbent should be adopted.
When the organic matter in the waste gas has recovery value, the regeneration process of water vapor, hot gas flow (air or inert gas) or pressure reduction desorption can be selected according to the situation. The high concentration gas produced after desorption can be recovered by cooling condensation or liquid absorption process according to the situation.
When the organic matter in the waste gas is not suitable for recovery, the hot gas flow regeneration process should be adopted. The high concentration organic gas produced by desorption is destroyed by catalytic combustion or high temperature incineration process.
When the concentration of organics in the waste gas is high and easy to condense, the condensation process should be used to partially recover the organics in the waste gas before adsorption purification.
Several basic elements of the waste gas treatment scheme are selected: the treatment scheme is selected according to the waste gas composition (whether it contains moisture, solid matter, oil matter, and the treatment difficulty), concentration (high, low), and emission form (continuous or intermittent emission).
The following conditions are suitable for the selection of incineration treatment scheme: high organic content, complex composition, flammable and explosive (butadiene, etc.), more difficult to decompose substances such as carbon disulfide, containing particles, oil like substances, continuous large-dose industrial waste gas. Such as gravure printing, plastic printing, painting, chemical synthesis, petrochemical, flavor, spice and other industries.
The following situations need to increase the cyclone dedusting device: industrial waste gas containing particles, such as waste gas from coating industry.
The following conditions need to increase the condenser: the exhaust gas temperature is more than 70 ℃ and contains a lot of water, so the condenser needs to be added.
Gas and liquid (oil) separation devices shall be added in the following cases:
Industrial waste gas containing oil, such as tail gas from waste incineration plant, contains a lot of water.
Explosion proof flame arrester (natural gas explosion-proof flame arrester), explosion-proof well and bursting disc are required in the following situations: the waste gas contains flammable and explosive components, and all explosion-proof requirements of the workplace.
Process design requirements
1 waste gas collection
The design of exhaust gas collection system shall comply with gb50019 code for design of heating ventilation and air conditioning of industrial buildings.
The gas collection system of the main production unit itself shall be used for collection as far as possible. The configuration of the gas collecting hood shall be coordinated with the production process without affecting the process operation. On the premise of ensuring the collection capacity, it shall be simple in structure and convenient for installation and maintenance management.
When the position, structure and wind speed of the suction port of the gas collecting hood are determined, the hood port shall be in the state of micro negative pressure, and the negative pressure in the hood shall be uniform.
The suction direction of the gas collecting hood shall be consistent with the movement direction of the polluted air flow as far as possible, so as to prevent the air flow around the gas collecting hood from being disordered, and avoid or weaken the influence of disturbing the air flow and air supply on the suction air flow.
When there are many waste gas generating points and long distance from each other, multiple collection systems shall be set up properly.
2 pretreatment
The pretreatment equipment shall be selected according to the composition and nature of the waste gas and the nature and content of the substances that affect the adsorption process. When the content of particles in the waste gas is more than 1mg / m3, the pretreatment shall be carried out by means of filtration or washing.
When the waste gas contains components that are difficult to desorb or cause adsorbent poisoning after adsorption, the pretreatment methods such as washing or pre adsorption shall be used.
When the concentration of organics in the exhaust gas is high, it shall be adjusted to meet the requirements by means of condensation or dilution. When the temperature of exhaust gas is high, heat exchange or dilution shall be used to adjust it to meet the requirements.
3 concentration and temperature requirements
Requirements for organic matter concentration: in addition to solvent and oil and gas storage and marketing devices