Ethyl acetate is the largest ester solvent in the printing, coating and pharmaceutical industries, with a boiling point of about 77 ℃ and strong volatility. The dosage is concentrated in the ingredients and coating links. The exhaust gas of this kind of workshop is characterized by large air volume and wide concentration span: the oven emission concentration is high and stable, and the overall exhaust concentration of the workshop is low and the flow is large. Only by configuring the recycling routes based on concentration gradients can operating costs be kept under control.
Ethyl acetate and water are partially miscible, the condensate is not completely layered, and the dehydration link before the recovery liquid is reused should be arranged, which is obviously different from the configuration of alkane solvent. The allocation scheme accounts for these two lines separately, so that there is a benchmark for comparison between investment and operating costs.
The exhaust gas concentration of the oven and the concentration section is high and the air volume is concentrated. Most of the solvent can be recovered by primary condensation, which is the most economical part of recovery. The overall exhaust air concentration of the workshop is low, the air volume is large, and the temperature cost of direct condensation is high. After condensation, membrane separation or adsorption is connected in series to check, and the condensation is collected at the top and the back section is covered at the bottom. The two branches are configured separately, which is lower than the total cost of unified processing after mixing.
The realization of diversion depends on the collection system: the high concentration point is connected separately, and there is no air mixing with the low concentration main pipe. After the mixed air, the high concentration is diluted, and the temperature utilization of the condensation section becomes poor, which is equivalent to diluting the well-collected solvent. Another advantage of diversion is in operation regulation: during the concentrated period of high concentration section of batch production, the condensation of high concentration branch is full load, the low concentration branch can bypass and reduce the amount, and the two branches are adjusted according to their respective concentrations, which is much more free than the adjustment of a single mixing system.
After standing, the condensate is not completely stratified, and there is an emulsified layer between the aqueous phase and the ester phase. The treatment is divided into three streams: the ester phase is filtered and tested for reuse; The aqueous phase contains a small amount of dissolved ester, which is treated by waste water and the chemical oxygen demand load is measured; The emulsified layer is collected centrally, and the next batch of condensate is re-separated or commissioned for treatment. Recycled liquid used for ingredients, purity, moisture and distillation range detection, according to the batch mixing.
Pre-cooling and dehumidification with wet incoming gas is especially important for ester recovery: after water vapor is condensed into condensate, the burden of stratification and dehydration is increased, and the water vapor is collected first in the pre-cooling section, benefiting both the quality of condensate and the back-end load. The storage of the recovered liquid is also exquisite: esters will slowly hydrolyze after long-term contact with water, and the recovery liquid tank will set aside the time arrangement for testing and turnover, and will be reused after the overdue batch is stored and rechecked.
| Segment | Features | Configuration Schedule |
|---|---|---|
| Oven discharge | high concentration stability | Primary Condensate Priority Recovery |
| Workshop exhaust | Low concentration and large air volume | Condensation plus membrane separation series |
| Pre-cooling section | Dehumidification | Condensate drain |
| Condensate separation | Layering is not thorough | Three-strand split plus emulsion layer treatment |
| Recovery liquid | partial mutual solubility | Testing Purity Moisture Distillation Range |
| Back section check | low concentration tail gas | Periodic inspection of the discharge port |
According to the water tolerance of the coating system, the purity of most ingredients is required to be above 99%, within a few thousandths of water, and the distillation range meets the industrial grade index. After batch testing, the index system is consistent with the supplier's incoming materials, and no additional adjustment is required at the end of use.
No need. When the exhaust concentration is low to close to the emission limit, it will be discharged directly to the standard, and the recovery device will start and stop or adjust the bypass according to the concentration threshold. For very low concentrations of the period of hard open device, electricity costs exceed the value of the solvent.
Accounting for incremental recovery and power consumption in the latter section: incremental recovery brought about by membrane separation control mostly occurs in low-concentration branch roads, and the increment of workshops with large air volume is considerable. Under the working conditions with small air volume and low concentration, the increment is limited. It is also a safe path to condense and run separately, and then leave the interface in the latter section and then go up.
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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