The wastewater in cellulose ether industry is mainly organic solvents such as toluene, oliticol, isopate, and acetone. Reducing organic solvents in production and reducing carbon emissions is an inevitable requirement for clean production. As a responsible enterprise, reducing exhaust emissions is also environmental protection requirements and should be fulfilled. Research on solvent loss and recycling in the cellulose ether industry is a meaningful theme. The author has explored a certain exploration of solvent loss and recycling in the production of fibrin ether, and achieved good results in actual work.
Keywords: cellulose ether: solvent recycling: exhaust gas; safety
Organic solvents are industries with large amounts of oil chemical industry, pharmaceutical chemical, pharmaceuticals and other industries. Organic solvents are generally not involved in the reaction during the production process of cellulose ether. During the use process, solvents in the process of recycling the chemical process through the recycling device can be used to achieve rebate. The solvent is discharged into the atmosphere in the form of exhaust gas (collectively referred to as VOC). VOC causes direct damage to people’s health, preventing these solvents from volatilizing during use, recycling Conditions to achieve low -carbon and environmentally friendly clean production.
1. The harm and common recycling method of organic solvents
1.1 The harm of commonly used organic solvents
The main organic solvents in the production of cellulose ether include toluene, isopropanol, olite, acetone, etc. The above are toxic organic solvents, such as dermopine. Long -term contact can occur in neurasthenia syndrome, hepatoblasty, and female workers’ menstrual abnormalities. It is easy to cause dry skin, cracking, dermatitis. It is irritating to the skin and mucous membranes, and has anesthesia for the central nervous system. The isopropanol vapor has a significant anesthesia effect, which has a stimulating effect on the mucosa of the eye and respiratory tract, and can damage the retina and the optic nerve. The anesthesia effect of acetone on the central nervous system has fatigue, nausea, and dizziness. In severe cases, vomiting, spasm, and even coma. It is irritating to the eyes, nose, and throat. Long -term contact with dizziness, burning sensation, pharyngitis, bronchitis, fatigue, and excitement.
1.2 Common recycling methods for organic solvents exhaust gas
The best way to treat solvent exhaust gas is to reduce the discharge of solvents from the source. The inevitable loss can only be recovered by the most likely solvents. At present, the chemical solvent recovery method is mature and reliable. The current commonly used organic solvents in waste gas are: Concretion method, absorption method, adsorption method.
The condensation method is the simplest recycling technology. The basic principle is to cool the exhaust gas to make the temperature lower than the dew point temperature of the organic matter, condense the organic matter into a droplet, directly separate from the exhaust gas, and recycle it.
The absorption method is to use the liquid absorbent to directly contact the exhaust gas to remove the organic matter from the exhaust gas. The absorption is divided into physical absorption and chemical absorption. Solvent recovery is physical absorption, and the commonly used absorbers are water, diesel, kerosene or other solvents. Any organic matter that is soluble in the absorbent can be transferred from the gas phase to the liquid phase, and the absorption liquid can be further treated. Usually, refined distillation is used to refine the solvent.
The adsorption method is currently using extensive solvent recovery technology. The principle is to capture organic matter in the exhaust gas by using the porous structure of active carbon or activated carbon fiber. When the exhaust gas is adsorbed by an adsorption bed, the organic matter is adsorbed in the bed, and the exhaust gas is purified. When the adsorbent adsorption reaches full, the water vapor (or hot air) is passed to heating the absorbent bed, regenerating the adsorbent, the organic matter is blown away and released, and the vapor mixture is formed with the water vapor (or hot air). Essence Cool the steam mixture with a condenser to condense it into a liquid. The solvents are separated by the use of psychological distillation or separators according to the water solution.
2. The production and recycling of organic solvent exhaust gas in the production of cellulose ether
2.1 Organic solvent exhaust gas generation
The solvent loss in the production of cellulose ether is mainly due to the form of wastewater and waste gas. The solid residues are less, and the water phase loss is mainly a wastewater clip. Low -boiling point solvents are very easy to lose in water phase, but the loss of low -boiling point solvents in general should be based on gas phase. Vitality loss is mainly decompression distillation, reaction, centrifugal, vacuum, etc. details as follows:
(1) The solvent causes “breathing” loss when stored in the storage tank.
(2) Low -boiling solvents have a greater loss during vacuum, the higher the vacuum, the longer the time, the greater the loss; the use of water pumps, W -type vacuum pumps or liquid ring systems will cause great waste due to vacuum exhaust gas.
(3) Losses in the process of centrifugation, a large amount of solvent exhaust gas enters the environment during centrifugal filter separation.
(4) Losses caused by reducing decompression distillation.
(5) In the case of residual liquid or concentrated to very sticky, some solvents in the distillation residue are not recycled.
(6) Insufficient peak gas recovery caused by improper use of recycling systems.
2.2 Recycling method of organic solvent exhaust gas
(1) Solvent such as storage tank storage tanks. Take heat preservation to reduce breathing, and connect nitrogen seals with the same solvent to avoid tank solvent loss. After the condensation of the tail gas enters the recycling system after condensing, it effectively avoids losses during high -concentration solvent storage.
(2) Vacuum system cyclic aeration and recycling waste gas in the vacuum system. Vacuum exhaust is recycled by condenser and recovered by the three -way recyclers.
(3) In the process of chemical production, the solvent that is closed to reduce the process has no tissue emissions. The wastewater containing a relatively high wastewater containing a high amount of wastewater is poured and recycled the exhaust gas. Varcation solvent.
(4) Strict control of recycling process conditions, or adopt secondary adsorption tank design to avoid peak exhaust gas loss.
2.3 Introduction to activated carbon recycling of low -concentration organic solvent exhaust gas
The above -mentioned tail gas and low -concentration gas exhaust gas meridian pipes are first entered into the activated carbon bed after the pre -installation. The solvent is attached to the activated carbon, and the purified gas is discharged through the bottom of the adsorption bed. The carbon bed with adsorption saturation is undertaken with low -pressure steam. The steam enters from the bottom of the bed. Crossing the activated carbon, the adsorbent solvent is attached and brought out of the carbon bed to enter the condenser: in the condenser, the solvent and water steam mixture are condensed and flowed into the storage tank. The concentration is about 25 o / O to 50 %, after the distillation or separator is separated. After the charcoal bed is associated and regenerates through drying, the switching back adsorption state is used to complete a operating cycle. The entire process runs continuously. In order to improve the recovery rate, the three cans of the second -level tandem can be used.
2.4 Safety Rules of Organic exhaust gas recycling
(1) The design, manufacturing, and use of the activated carbon attachment and tube condenser with steam should meet the relevant provisions of the GBL50. The top of the active carbon suction container should be set up with pressure gauge, safety discharge device (safety valve or blasting tablets Device). The design, manufacturing, operation, and inspection of the safety leakage device shall comply with the provisions of “the design and calculation of the design calculation of the design and calculation of the security attachment and the design of the five security valves and the blasting tablet” of the pressure vessel safety technical supervision regulations. “
(2) A automatic cooling device should be provided in the activated carbon absorbing attachment. The activated carbon suction attachment gas inlet and export and the adsorbent should have multiple temperature measurement points and the corresponding temperature display regulator, which displays the temperature at any time. When the temperature exceeds the setting of the highest temperature, immediately issue alarm signal and automatically turn on the cooling device. The I’HJPE of the two temperature test points is not more than 1 m, and the distance between the test point and the outer wall of the device should be greater than 60 cm.
(3) The gas concentration detector of the activated carbon suction attachment gas should be set to detect the gas concentration of gas regularly. When the concentration of organic gas export exceeds the maximum set value, it should be stopped: adsorption and striking. When the steam is striped, the safety exhaust pipe should be set up on the equipment such as condenser, gas liquid separator, and liquid storage tank. Activated carbon absorbers should be set on the air duct at the entrance and export of gas inlet and exports to determine the air flow resistance (pressure drop) of the adsorbent to prevent the gas string of gas stringing from poor air exhaust.
(4) The solvents should be assaulted by the air pipe and the air -phase concentration alarm in the air pipe in the air. Waste activated carbon is treated according to hazardous waste. Electrical and equipment take out explosion -proof design.
(5) The solvent is called the three -way access to the fire blocking unit to add a fresh air when connected with each recycling unit.
(6) The solvent recovers the pipelines of each pipeline to access the exhaust gas of low -concentration dilute liquid phases as much as possible to avoid direct access to high concentration exhaust gas.
(7) The pipelines of the solvent recovery are used for electrostatic exporting design, and the chain stop nitrogen is charged and the system cutting is cut with the workshop alarm system.
3. Conclusion
In summary, reducing solvent exhaust loss in the production of cellulose ether beef is a reduction in costs, and it is also a necessary measure to serve the society’s pursuit of environmental protection and maintain employees’ occupational health. By refining the analysis of the production solvent consumption analysis, the corresponding measures to maximize the solvent emissions; then the recycling efficiency of the recovery efficiency is improved by optimizing the design of the activated carbon recycling device: Security Risk. So as to maximize the benefits on the basis of security.