Ethyl acetate is one of the most widely used ester solvents in the chemical and pharmaceutical industries, with a boiling point of about 77 ℃, moderately low, volatility and solubility. It is widely used in extraction, crystallization, washing, coating and other processes. Its recovery route is more favorable: the boiling point is not low, and the condensation temperature does not need to be pressed too deeply; Partial miscibility with water is also controllable. The common practice is to collect the condensate after closed collection, and determine whether the recovered liquid needs further treatment according to its purpose.
The first is that the dosage is large and there are many points. Several processes of extraction, washing and crystallization are all used in one workshop. The source of tail gas is scattered but the components are consistent, which is suitable for combined collection. The second is the medium boiling point, which can be condensed by water cooling at normal temperature to a considerable proportion, and the deep cold temperature level is reserved for checking or high concentration occasions. The third is flammable. The anti-static and anti-accumulation of the collection and recovery system should be implemented according to the specifications.
It is also worth noting that ethyl acetate will slowly hydrolyze acetic acid in a humid environment, and the acidity of the recovered liquid will increase after long-term storage, which is corrosive to carbon steel equipment. This should be considered for temporary storage of the recovered liquid and pipeline material selection.
The volatilization of extraction and washing process is concentrated in the container opening and transfer link. In practice, the opening operation is changed to closed or semi-closed, and the closed pipeline is transferred away. The main collection points of crystallization centrifugation process are the exhaust port of centrifuge and the breathing port of mother liquor tank, which are connected to the recovery main pipe.
In the multi-process common scene of the pharmaceutical workshop, the operation time of each process is staggered, and the total air volume is taken according to the simultaneous use coefficient when merging and collecting, and it is not necessary to simply add the air volume at each point, otherwise the fan and the condensation section will be too large.
The boiling range of ethyl acetate determines that the temperature arrangement of the condensing section is relatively calm: first, the inlet air is reduced to close to normal temperature with circulating water to condense most of the solvent; Then use the low temperature section to collect the rest. In the process with high intake air temperature, such as drying exhaust gas, pre-cooling is done first, and the load and frosting speed of the low temperature section will be significantly improved.
If the tail gas is mixed with lower boiling point components such as ethanol and acetone, according to the idea of classifying the highest boiling point components first, ethyl acetate can be recovered in large quantities at the first stage, while the light components are left to the low temperature stage, and the two stages do their own work.
| Segment | Configuration considerations | Description |
|---|---|---|
| extraction washing | Closed or semi-closed operation | Reduce open volatilization and transit losses |
| crystallization centrifugation | Exhaust port and breathing port access supervisor | Two are the highest concentration points |
| Merge Collection | Take the air volume according to the simultaneous use coefficient | Avoid excessive matching of fan and condensing section |
| Condensation section | Water cooling and pre-coagulation first, and then the low temperature section is finished. | The temperature position is arranged calmly, and the energy consumption is friendly. |
| dry tail gas | Pre-cooling and cooling before entering the low temperature section | Reduce frost and load in low temperature section |
| Recovery liquid temporary storage | Acid resistant material, regular inspection | Hydrolyzed acid is corrosive to carbon steel |
Whether the recovered liquid obtained by condensation contains water or not depends on the humidity of the incoming gas. Extraction reuse usually has a certain tolerance for moisture, crystallization reuse is more demanding, the need to detect moisture and acidity. It is recommended to give priority to acid-resistant materials for the temporary storage tank of recovery liquid, or to regularly detect acidity and reuse it in time to reduce storage time.
The measurement record of the recovered liquid is the basis for daily judgment of the state of the recovery section: when the amount of solvent input in the process is stable and the amount of recovered liquid continues to decline, first check the state of the sealing and heat exchange surface of the collection point.
The recovery rate depends on the intake concentration, temperature level configuration and heat exchange area, and cannot be separated from the specific working conditions to a fixed number. The boiling point of ethyl acetate is moderate, the condensation conditions are relatively friendly, and the recovery effect is usually ideal under the premise that the intake concentration is guaranteed. The specific value is recommended to be calculated according to the measured intake conditions.
Look at the use. Extraction and other processes with high moisture tolerance can be reused directly after passing the test. Crystallization and other processes sensitive to moisture need to detect moisture and acidity, and reuse after dehydration if necessary.
Classification by boiling range: the boiling point of ethyl acetate is higher than that of ethanol, and the first stage of higher temperature is recovered in large quantities, and ethanol is left to the low temperature section. Separate can be treated separately, the quality of the recovery liquid is more guaranteed.
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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