The selection of activated carbon is not good, and the life expectancy is not long. Generally, it needs to be changed once every 6 months to 1 year. The cost of changing activated carbon is very high. The special activated carbon has an adsorption capacity of more than 100%, and has good desorption and stability. Therefore, the life is more than 2-3 years, which can save costs. The specific surface area and pore structure of activated carbon have a great relationship. Different organic solvents use activated carbon with different pore diameters, so as to ensure that the attenuation is not obvious, the gas pressure resistance is small, the adsorption capacity is strong, and the desorption is easy, so that the gas flow rate is fast. , to eliminate local temperature rise phenomenon. Organic waste gas treatment activated carbon has the advantages of reasonable pore size distribution, high adsorption capacity, fast adsorption speed, high mechanical strength, use in a fixed bed, low gas flow resistance, easy desorption and regeneration, and a large concentration range for most inorganic gases (such as sulfurization). Matter, nitrogen oxides, etc.) and most organic vapors, solutes have strong adsorption capacity.
Specific indicators:
Adsorption index: CTC better than 100% benzene adsorption: better than 50% acetone adsorption: more than 50%.
Strength: 70-90% or 95% later, see the specific application. The higher the better, the higher the strength, the lower the adsorption may be.
Specific gravity: The higher the specific gravity, the higher the cost, indicating that the smaller the specific surface area, the more realistic. The same the larger the cubic weight, the heavier.
Ash content: 6% or less, moisture <5% impurities too high will also affect adsorption and cost.
Fire point: > 450 degrees.
Material: The main choice is wood or coal. The coconut shell is not suitable because the organic solvent requires medium-porosity activated carbon. If the coal quality is higher than the wood, the above index cost is higher. Ordinary coal-based activated carbon CTC50-70% Benzene adsorption: 20-40% Wood chemical activated carbon: CTC: 100%-140% Benzene adsorption: 45-60% The specific gravity is only half of the coal quality.
Activated carbon (pictured)
Organic waste gas treatment:
Organic waste gas treatment refers to the use of various technical measures to reduce oil loss, reduce the amount of organic solvents or exhaust gas purification to eliminate organic waste gas pollution. Organic waste gas sources are widely distributed. In order to prevent pollution, in addition to reducing oil consumption and reducing the amount of organic solvents to reduce the production and emission of organic waste gas, exhaust gas purification is currently a practical approach. Commonly used methods include adsorption, absorption, catalytic combustion, and thermal combustion. When using the purification method, the county should select the method of low cost, low energy consumption and no secondary pollution according to the specific conditions, try to make harm to the benefit, and fully recycle the components and waste heat. In most cases, the petrochemical industry uses condensation, absorption, direct combustion and other methods due to high exhaust gas concentration; coatings, printing and other industries use adsorption, catalytic combustion and other methods due to low exhaust concentration.
Governance method:
1. Condensation recovery method: the organic waste gas is directly introduced into the condenser through adsorption, absorption, dissociation and separation, and valuable organic matter can be recovered. The method is applicable to the working conditions of high organic waste gas concentration, low temperature and small air volume, and needs to be attached. Refrigeration equipment is mainly used in the pharmaceutical and chemical industries, and is rarely used by printing companies.
2. Absorption method: Generally adopt physical absorption, that is, the exhaust gas is introduced into the absorption liquid for purification, and the absorption liquid is saturated, and then heated, analyzed, and condensed and recovered; the method is applicable to the air volume, low temperature, low concentration exhaust gas, but needs to be equipped with heating Analytical recovery device, large equipment and high investment.
Generally, the activated carbon adsorption method is adopted: the exhaust gas is adsorbed by the activated carbon, and when the adsorption is saturated, the activated carbon is desorbed and regenerated, the exhaust gas is blown off, catalytically combusted, and converted into harmless substances, and the activated carbon is continuously used. When the activated carbon is regenerated to a certain number of times, the adsorption capacity is significantly reduced, and it is necessary to regenerate or renew the activated carbon.
Activated carbon is currently the most used method for treating organic waste gas, and has good adsorption performance for benzene-based waste gas, but 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 adsorption of activated carbon is the most commonly used. Activated carbon is used up to: activated carbon granules and activated carbon fiber. The price of activated carbon granules is relatively cheap, but the effect is poor. Compared with activated carbon fiber, the price is relatively high, and the effect is better.
Activated carbon for organic gases:
(1) The specific surface area is large and the effective adsorption amount is high. Since the surface area of ​​Xinsen activated carbon of the same weight is nearly ten times that of coal-based activated carbon particles, the weight of Xinsen activated carbon that needs to be filled is very small, but the adsorption efficiency is very high, depending on the organic gas content and other physical properties of the treated exhaust gas. The adsorption efficiency is between 85% and 98%, and the multi-stage adsorption process can reach 99.99%, which is much higher than the highest adsorption rate of 88% for the common activated carbon particle adsorption method, and the volume and total weight are also small.
(2) The adsorption and desorption processes are short and the speed is fast; the desorption and regeneration energy consumption is low. Xinsen activated carbon adsorbs organic gas several times to several tens of times larger than ordinary granular activated carbon (GAC), and has good adsorption capacity for inorganic gases, and can maintain high adsorption and desorption speed and long service life. . If heated by steam for 10-30 minutes, it can be completely desorbed, and the heat resistance is good. In the inert gas, the high temperature is above 1000 °C, and the ignition point in the air is above 450 °C.
(3) The shape is variable and easy to use. It has columnar and spherical particles, so it is very convenient to replace and will not cause any harm to the human body.
(4) Special activated carbon with special properties can be produced according to needs; the strength is good and will not cause secondary pollution.
3. Direct combustion method: use auxiliary fuel such as gas or fuel to burn, and heat the mixed gas to decompose the harmful substances into harmless substances under the action of high temperature; the method is simple in process and small in investment, and is suitable for exhaust gas with high concentration and small air volume. However, the safety technology and operation requirements are high.
4. Catalytic combustion method: the exhaust gas is heated and converted into harmless and odorless carbon dioxide and water by catalytic combustion; the method has low ignition temperature, high energy saving, high purification rate, convenient operation, small floor space and large investment investment. Organic waste gas at high temperature or high concentration.
5. Adsorption method:
(1) Direct adsorption method: The organic waste gas is adsorbed by activated carbon, which can achieve a purification rate of more than 95%. The equipment is simple and the investment is small, but the activated carbon is frequently replaced, and the working procedures such as loading, unloading, transportation and replacement are increased, resulting in an increase in operating costs.
(2) Adsorption-recovery method: the organic waste gas is adsorbed by the fibrous activated carbon, and is degassed by backflushing with superheated steam after being nearly saturated; this method requires providing the necessary amount of steam.
(3) New adsorption-catalytic combustion method: This method combines the advantages of adsorption method and catalytic combustion method, adopts new adsorption material (honeycomb activated carbon) adsorption, introduces hot air near drinking and then desorbs, analyzes and desorbs The exhaust gas is introduced into the catalytic combustion bed for flameless combustion, which is thoroughly purified, and the hot gas is recycled in the system, thereby greatly reducing energy consumption. The method has the characteristics of stable and reliable operation, low investment, low operating cost and convenient maintenance. It is suitable for high air volume and low concentration of exhaust gas treatment. It is a mature and practical method for domestic treatment of organic waste gas.
Activated carbon price cost budget:
The activated carbon is made of hardwood or coconut shell, and the deep activation specific surface area is large. Therefore, the activated carbon has rich internal pores and light density. The internal honeycomb has many pores inside the sponge and has good adsorption. One ton of wood activated carbon is 2.7-3.5 m3. The coal-based activated carbon is less than 2m3, which means that the coal-carbon is not rich in internal pores, small in specific surface area, high in density and high in impurities. If the coal-based activated carbon is not cheap according to the cube, there is a huge gap between the adsorption amount and the service life. Therefore, the price of the activated carbon alone may not determine the cost, and it is necessary to calculate the volume of the activated carbon to know the cost performance. Such as 10m3 = 3 tons of wood activated carbon = 4.5 tons of coconut shell charcoal = 5.5 tons of coal-based activated carbon. Wood columnar activated carbon has higher specific surface area than traditional coal-type columnar charcoal, effective pores are rich in pores, low ash content, light specific gravity, gas phase adsorption The value of carbon tetrachloride adsorption CTC>110% is dominant. The pore size distribution of the product is reasonable, and the best adsorption and desorption are achieved, thereby greatly improving the service life of the product. The main applications are chemical, metallurgy, printing and dyeing and rubber industries: activated carbon is mainly used as a chemical catalyst and carrier in the chemical industry, gas purification, solvent Recycling, decolorization and refining of oils and fats. At present, the market demand is about 10,000 tons or more, basically based on coal-based columnar activated carbon, and wood high-end activated carbon accounts for about 10-15%, which is mainly caused by the imbalance of price gap. With the attention of national energy sources, coal resources Integration, resource tax levy, the cost of coal charcoal is rising, and the wood columnar activated carbon uses the “three remnants†of forestry chemical industry as the raw material to have the advantage of national policy support. On the other hand, the use of the enterprise to improve the requirements of activated carbon itself also determines The wooden columnar activated carbon will gradually replace the coal-based activated carbon.
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