Toluene is one of the most commonly used solvents in printing, coating and adhesive industries, with large dosage, moderate boiling point and considerable recovery value. Its recovery conditions are relatively friendly: insoluble in water, condensed condensate is easy to stratify; The boiling point is higher than that of low boiling point solvents such as ethyl acetate, and most of the vapors can be liquefied by conventional freezing water temperature. Therefore, the condensation-based recovery route has good applicability in the treatment of toluene waste gas.
The conventional configuration is two stages of condensation and membrane separation: the condensation section liquefies toluene vapor according to the temperature level, and the organic phase is taken for reuse after the condensate is standing and stratified; The membrane separation section is arranged after condensation to intercept the residual organic vapor to form an internal circulation, and the purified tail gas is discharged according to the emission management requirements. For printing and painting workshops with high concentration and medium gas volume, this skid-mounted configuration can cover it. Where the gas volume fluctuates greatly, a buffer tank shall be set up before condensation.
The lower the condensation temperature, the lower the residual concentration, the more thorough the recovery, and the corresponding increase in refrigeration energy consumption. Toluene has a moderate boiling point and is relatively easy to condense. Usually, the main part can be recovered by conventional freezing water temperature. The need for deep cooling should be determined according to the actual emission management requirements and the content of low boiling point components in the air source, so as to avoid overbearing refrigeration load for a long time in pursuit of lower outlet concentration.
| Comparison item | Toluene | Low-boiling solvents (such as ethyl acetate) |
|---|---|---|
| Boiling Point Level | Moderate, good condensing conditions | Lower, faster volatilization |
| Condensation temperature level | Conventional chilled water can be recycled to the main body | Need to lower the temperature level or increase the cryogenic section |
| Condensate separation | Insoluble in water, easy to stratify | Water solubility is complex and needs to be considered separately |
| respiratory loss | relatively mild | Low boiling point, breathing exhaust must be collected |
Focus on monitoring the condensate outlet temperature, condensate stratification and recovery trend. The unclear stratification is mostly related to the entrainment of moisture or emulsification in the gas source, and the upstream process needs to be checked. When the recovery amount decreases, priority is given to checking the bypass of the collection pipe network and scaling of the heat exchange surface. The recovery amount, investment amount and purchase amount are put together to make material balance, and the recovery effect is reflected by data.
Applicable. The toluene waste gas concentration in the printing and coating process is high and the gas volume is medium, which can be covered by the skid-mounted configuration of condensation and membrane separation, which is calculated according to the on-site gas source.
It is mostly related to moisture entrainment or emulsification in the air source. First check the water entrainment condition in the upstream process, and if necessary, set up a static setting or separation link in the condensate tank to improve stratification.
Condensate can be recycled to production according to the reuse standard after static stratification and sampling inspection. Distillation purification can be added in occasions with high purity requirements.
This article by LuoyangWohong PetrochemicalEquipment Co., Ltd. arranges that the company provides design, manufacturing and operation and maintenance services for condensation recovery, membrane separation recovery and complete solvent recovery devices for chemical and pharmaceutical enterprises. If you need process evaluation or scheme configuration, please contact and exchange.
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