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How To Handle Fume Hood Exhaust

May 03, 2018

How to deal with the exhaust fumes from the fume hood, the following is the organic waste gas treatment.

The treatment of organic waste gas refers to the elimination of organic waste gas pollution by using a variety of technical measures to reduce oil loss, reduce the use of organic solvents, or purify exhaust gas through various means. Organic waste gas sources are widely distributed. In order to prevent pollution, in addition to reducing oil loss, reducing the amount of organic solvents used to reduce the generation and emission of organic waste gas, exhaust purification is a practical and feasible way of governance. Commonly used methods are adsorption, absorption, catalytic combustion, thermal combustion and so on. When the purification method is selected, the county shall select the method of low cost, low energy consumption, and no secondary pollution according to the specific circumstances, and strive to achieve as much as possible the benefits of harm, and the full use of recycled components and waste heat. In most cases, the petrochemical industry adopts methods such as condensation, absorption, and direct combustion due to high exhaust gas concentrations; in the paint construction and printing industries, adsorption and catalytic combustion methods are used due to low exhaust gas concentrations.

Governance method

  1. Condensation recovery method: The organic waste gas is directly introduced into the condenser and adsorbed, absorbed, decomposed and separated to recover valuable organic matter. The method is applicable to the conditions of high concentration of organic waste gas, low temperature, and small air volume. Refrigeration equipment is mainly used in the pharmaceutical and chemical industries, and printing companies are less used.

  2. Absorption method: generally adopts physical absorption, that is, the exhaust gas is introduced into the absorption liquid to be purified; after the absorption liquid is saturated, it is heated, analyzed and condensed and recovered; this method is applicable to the atmospheric air, low temperature, low concentration exhaust gas, but needs to be equipped with heating Analytical recovery device, large equipment, high investment.

    Activated carbon adsorption method is generally adopted: Adsorption of exhaust gas by activated carbon, when the adsorption is saturated, activated carbon desorption regeneration, the exhaust gas is blown off after catalytic combustion, converted into harmless substances, renewable activated carbon continues to be used. When the activated carbon is regenerated to a certain number of times, the adsorption capacity is significantly decreased, and it is necessary to regenerate or renew the activated carbon.

    Activated carbon is the most commonly used method for treating organic waste gas. It has good adsorption performance for benzene waste gas, but it has poor adsorption to hydrocarbon waste gas. The main disadvantage is that the operating cost is high and it is not suitable for the environment with high humidity. However, for the current market application, the adoption of activated carbon adsorption is most commonly used. Activated carbon used at most: activated carbon particles and activated carbon fiber, the use of activated carbon particles is relatively cheap, but the effect is worse, compared to the use of activated carbon fiber prices are relatively higher, the effect is better.

    Organic gas special activated carbon

    A. Large specific surface area, high effective adsorption. Since the surface area of activated carbon of the same weight is nearly ten times that of coal activated carbon, the weight of activated carbon that needs to be filled is very small, but the adsorption efficiency is very high. According to the difference in the organic gas content and other physical properties of the treated exhaust gas, adsorption The efficiency is between 85% and 98%, and the multi-stage adsorption process can reach 99.99%, which is far higher than the maximum adsorption rate of 88% for the ordinary activated carbon particle adsorption method, and the volume and total weight are also very small.

    B. Adsorption and desorption strokes are short and fast; desorption and regeneration are low in energy consumption. The adsorption capacity of activated carbon for organic gases is several to several tens of times larger than that of common granular activated carbon (GAC), and it also has good adsorption capacity for inorganic gases, and can maintain a high adsorption desorption rate and a long service life. If it is heated with water vapor for 10-30 minutes, it can be completely desorbed, with good heat resistance, high temperature resistance above 1000°C in inert gas, and ignition point above 450°C in air.

    C. Variable shape and easy to use. Columnar, spherical particles, easy to replace, will not cause any harm to the human body.

    D. According to the need to produce special activated carbon with special properties; good strength, will not cause secondary pollution.

  3. direct combustion method: the use of fuel gas or fuel and other auxiliary fuel combustion, the mixed gas heating, so that harmful substances decomposed under high temperature into harmless substances; this method is simple, low investment, suitable for high concentration, small amount of air exhaust , but the safety technology and operational requirements are high.

  4. Catalytic combustion method: The exhaust gas is heated by catalytic combustion to convert into harmless and odorless carbon dioxide and water; this method has low ignition temperature, energy saving, high purification rate, convenient operation, small area, and large investment investment. At high temperature or high concentration of organic waste gas.

  5. adsorption method:

    (1) Direct adsorption method: After the organic waste gas is adsorbed on activated carbon, the purification rate can reach more than 95%. The equipment is simple and the investment is small. However, the activated carbon is replaced frequently, and the working procedures such as loading and unloading, transportation, and replacement are increased, resulting in an increase in operating costs.

    (2) Adsorption-recovery method: The use of fiber activated carbon to adsorb organic waste gas, near saturation with superheated steam backflush, desorption regeneration; this Act requires the provision of the necessary amount of steam.

    (3) Novel Adsorption-Catalytic Combustion Method: This method combines the advantages of adsorption method and catalytic combustion method. It adopts new adsorption material (honeycomb activated charcoal) for adsorption. It is introduced into the hot air after desorption and subsequent introduction to desorption, analysis and desorption. After the exhaust gas is introduced into the catalytic combustion bed for flameless combustion, it is thoroughly purified, and the hot gas is recycled in the system, which greatly reduces energy consumption. This method has the characteristics of stable and reliable operation, low investment, low operating cost, convenient maintenance, etc. It is applicable to the treatment of large amounts of wind and low concentrations of exhaust gas. It is a mature and practical method for domestic treatment of organic exhaust gas.