How to recycle cyclohexanone waste gas? Condensation recovery and condensate stratification configuration of high boiling point ketones
Release date: 2026-10-02
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Cyclohexanone is a commonly used ketone solvent in the caprolactam, coating, ink, and leather finishing industries, with a boiling point of approximately 156℃, making it a high-boiling-point solvent among common solvents. High boiling point brings two direct configuration conveniences: firstly, the volatilization rate is slow at room temperature, resulting in a relatively mild exhaust gas concentration, which reduces the burden on the collection system; secondly, the condensation temperature requirement is relaxed, and two-stage water cooling condensation can recover most of the solvent, with the deep cooling link only being configured when necessary for quality control. Coupled with the property of partial solubility in water and the ability to separate into layers when the condensate is left to stand, the recovery route is generally smooth, and the operational economy is among the better in ketones.
Where does the cyclohexanone tail gas come from
The cyclohexanone tail gas in the chemical industry is mainly concentrated in the exhaust from the oxidation section, the non-condensable gas at the top of the distillation tower, and the breathing of storage tanks; in the coatings and ink industry, cyclohexanone is mostly used as a high-boiling point solvent and leveling agent, and it volatilizes during paint mixing, spraying, and drying processes; the exhaust from ovens in the leather and printing finishing processes is also a concentrated source. The concentration and volume of gas from different sources vary greatly: the concentration of non-condensable gas from distillation is high but the volume is small, the exhaust from ovens has a large volume but low concentration, and the breathing of storage tanks fluctuates with loading and unloading. In terms of collection and configuration, sources are grouped according to their concentration, with high and low concentration paths separated, ensuring a stable load on the treatment section.
The vapor of cyclohexanone has a mild irritating odor, and the sealing requirements for the collection system are higher than those for general solvents. The sealing components of the hood and enclosure should be included in regular inspections.
How to set up condensation configuration
The configuration of the condensation section is determined based on concentration grouping: the high-concentration branch (distillation non-condensable gas, tank breathing) is first pre-cooled to condense water vapor and some high-boiling components, and then enters the low-temperature section for finishing; the low-concentration high-airflow branch (oven, spraying) should first be concentrated to increase the inlet concentration, as directly deep-cooling the high-flow low-concentration exhaust gas is uneconomical. The temperature level is calculated based on the inlet dew point, and the high boiling point of cyclohexanone allows for a considerable recovery ratio with normal water cooling, reducing the burden on the low-temperature section and lowering the frequency of frost formation and defrosting.
When designing the pipeline, attention should be paid to the freezing point of cyclohexanone: when the ambient temperature is low, condensate will precipitate on the pipe wall. The pipeline insulation and slope should be checked according to winter operating conditions, and the location for low-point drainage should be properly arranged.
How to manage condensate and its reuse
Cyclohexanone is partially soluble in water, and the condensate can be layered after standing still. The oil phase and water phase should be treated separately: the oil phase is reused according to its purpose after testing for moisture and purity. For paint mixing and cleaning purposes, the threshold is low, and the proportion of direct reuse can be higher; the water phase is metered and then discharged into the sewage system. The condensate should be stored in a sealed manner. Cyclohexanone is not very hygroscopic, but open storage can still introduce impurities, affecting the quality of reuse.
The recovery accounts are compared monthly: the ratio of recovered liquid volume to solvent requisition volume. When the ratio continues to decline, inspect the heat exchange surface and collection seal. Most of the time, the problem lies in the collection end rather than the condensation end.
Configuration key points reference
| project | characteristic | Configuration considerations |
|---|---|---|
| boiling point | About 156℃ | A two-stage water-cooled condensation system is sufficient |
| volatility | Slow volatilization at room temperature | The collection burden is small, and the sealing is strict |
| water-soluble | Partially soluble and stratifiable | Static reuse of stratified tank |
| pour point | Precipitation on the wall of a low-temperature tube | The insulation slope is verified based on winter conditions |
| Low-concentration exhaust gas | The air volume of the oven is large | Concentrate first, then condense |
| Reuse classification | Determine depth based on usage | Cleaning and direct use distillation purification |
How to implement operation management
- The high-concentration and low-concentration branches are collected in groups, and the processing loads are accounted for separately;
- The condensation temperature level is set according to the measured dew point concentration, and the low temperature section is only used when necessary;
- The insulation and slope of the pipeline should be verified based on the winter freezing point conditions, and the low-point drainage should be included in the daily inspection;
- Condensate is recycled after stratification, and the purity of water in the oil phase is tested batch by batch;
- Regularly inspect the sealing components of the cover and enclosure. In case of odor complaints, first check the sealing;
- Compare the recycling quantity with the requisition quantity on a monthly basis. If the ratio is abnormal, first check the collection end.
Frequently Asked Questions
What is the difference in the recovery configuration between cyclohexanone and acetone?
Acetone has a boiling point of about 56℃ and is completely miscible with water. It has a deep condensation temperature range, and the condensate needs to be dehydrated. Cyclohexanone has a significantly higher boiling point, a wider temperature range, and the condensate can be stratified. The differences between the two are concentrated in the condensation section and the condensate side.
Why is the efficiency low when exhausting from the oven is directly condensed?
The high air volume dilutes the concentration, leading to a decrease in dew point, and the condensation ratio at the same temperature level drops significantly. To make the investment worthwhile, it is necessary to first concentrate and increase the inlet gas concentration before condensing.
What should I do if the condensed liquid stratification is slow?
Insufficient standing time or low temperature can slow down stratification. For stratified tanks, add insulation and extend the standing time. When emulsification is evident, check whether the incoming gas contains surface active substances such as cleaning agents. Collecting at the source separately is more convenient than demulsifying inside the tank.
This article is compiled by Luoyang Wohong Petrochemical Equipment Co., Ltd., which provides design, manufacturing, and operation and maintenance services for condensation recovery, membrane separation recovery, and complete solvent recovery equipment to chemical and pharmaceutical enterprises. If you need process evaluation or scheme configuration, please feel free to contact us for discussion.
