Cyclohexane is used as a solvent and reaction medium in the chemical and pharmaceutical industries, with concentrated dosage and stable volatilization. Compared with common ester alcohol solvents, cyclohexane has a boiling point of about 81 ℃ and is completely immiscible with water. The idea of recovery configuration is close to alkanes: the condensation temperature is determined by dew point, the oil phase is directly reused after the condensate is stratified, and the treatment process is relatively simple.
The source of cyclohexane tail gas is concentrated in the tank breathing, feeding and distillation process: the concentration of the tank breathing gas fluctuates with the receiving and sending materials, and the emission concentration of the distillation process is high and stable. The recovery configuration is divided by source, and the high concentration part is preferentially recovered.
The storage and transportation management matched with recovery should also keep up with: the saturated vapor pressure of cyclohexane changes obviously with temperature, the respiration of storage tanks in summer is large, and the recovery load follows the season. In the configuration stage, both summer and winter working conditions are checked again. The adaptability of the device is better than that designed according to single-point working conditions, and the operation adjustment is less.
Storage tank respiration is a continuous volatilization source: large respiration of material receiving, small temperature difference between day and night, and the period when the concentration of respiratory gas is close to saturation is concentrated in the period of material receiving and high temperature. Distillation and reaction processes have high emission concentration and single component, which is the best part of recovery economy. The intermittent volatilization of feeding and cleaning links is small, and it can be incorporated into the main pipe after collection.
The lower explosive limit of cyclohexane is low and its volatility is strong. The coordination between the collection pipeline and the nitrogen seal of the storage tank should be checked: the storage tank with nitrogen seal in place has low oxygen content in respiratory gas and better safety of the recovery system.
Set the condensation temperature level according to the dew point of cyclohexane and the concentration of intake air: most of the exhaust gas from the process with high concentration can be recovered by primary condensation; The concentration of respiratory gas in the storage tank fluctuates greatly. Check the temperature level according to the low concentration period to ensure the lower limit of the recovery rate throughout the day. The immiscible characteristic of cyclohexane and water makes the condensate treatment simple: the condensate is standing for stratification, the oil phase is filtered and recycled, and the water phase is treated separately with a small amount.
The frost prevention arrangement in the low temperature section is not economical: when the moisture content of the incoming gas is low, the frost layer grows slowly, but the respiratory gas of the storage tank brings more water in the wet season. The dehumidification in the pre-cooling section should be carried out first, and the defrosting cycle in the low temperature section can be lengthened.
The impurities in the cyclohexane recovery liquid are mainly water and a small amount of high boiling substances. After layered filtration, the purity and water are tested according to batches, and the ingredients are directly reused. For the batch used for the reaction medium, increase the distillation range of the test items to confirm that the light component content does not affect the reaction system.
| Segment | Features | Configuration Schedule |
|---|---|---|
| Tank Breathing | Fluctuating and wet seasonality | Nitrogen sealing coordination, pre-cooling and dehumidification first |
| Distillation discharge | High and stable concentration | Primary Condensate Priority Recovery |
| Feeding cleaning | Small intermittent volume | Consolidated into the supervisor for centralized processing |
| Condensate separation | immiscible with water | Static stratification, oil phase reuse |
| Low temperature section | Anti-frost management | The defrosting cycle is seasonally adjusted |
| Detection of reuse | By Batch | Batch-by-batch inspection of purity, moisture and distillation range |
The main risk of the recovered liquid after layered filtration is the distribution of moisture and light and heavy components, and the purity, moisture and distillation range are tested by batch, which meets the requirements of the reaction system and then reused. When used for low-demand purposes such as cleaning, inspection items can be simplified.
The concentration of respiratory gas fluctuates greatly, and the combination will dilute the stable high concentration of process exhaust gas. Separate branches, respiratory gas is incorporated after pre-cooling, or treated at a separate time period, and the recovery rate is more stable.
The unit price and recovery difficulty of cyclohexane are moderate, and the recovery period of process exhaust gas with high concentration is short. The economy of recovery of respiratory gas in storage tanks depends on the frequency of receiving and sending materials, and it is usually cost-effective to calculate the tank area with frequent receiving and sending.
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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