How to recycle n-pentane exhaust gas? The core is "closed collection and deep condensation": the pentane-containing exhaust gas in the foaming process and storage and transportation links is first collected by a closed system, and then the low-boiling point vapor is condensed and recycled by more than two stages of condensation. The boiling point of n-pentane is about 36 ℃, and it volatilizes very fast at normal temperature. The condensation depth and the tightness of the system directly determine the recovery effect. It is not miscible with water and also makes the separation of condensate relatively simple.
The first is low boiling point, volatile fast. The boiling point of about 36 ℃ belongs to the lowest level in common solvents, and the normal temperature exposure means a large amount of volatilization. The emission of the size of the storage tank in summer is obviously increased. The collection system should be approved according to the peak working condition.
The second is immiscible with water. The condensate can be stratified after standing, the oil phase is recycled and reused, the water phase is conventionally treated, and the separation link is less trouble than ether alcohol medium.
The third is highly flammable. The exhaust system shall be protected according to flammable medium, fan and electrical selection, anti-static grounding and fire retardant facilities shall be implemented, and the pipeline shall be connected to ground.
The breathing port of the storage tank and the loading and unloading port are the two main discharge points: the breathing exhaust of the storage tank is introduced into the collection branch pipe, and the loading and unloading truck adopts the bottom loading and refueling gas recovery joint; The mold exhaust and curing warehouse exhaust in the foaming process are collected by point enclosure. The simultaneous use coefficient shall be approved before the multi-strand branch is merged into the main pipe, and the pipeline shall maintain the slope and set a low point for drainage.
The boiling point of n-pentane is low, and the recovery rate is limited under conventional cooling water temperature, which requires more than two stages of condensation: the front stage is precooled and dehumidified to cool down, and the rear stage is cryogenic to condense most of the pentane vapor. Cold energy recovery between the two stages is carried out to reduce energy consumption, and the pipeline valves in the low temperature section are checked according to the medium compatibility and heat preservation is strengthened.
The condensation depth is determined by the balance between the emission limit and the recovery value: the lower the recovery rate, the higher the recovery rate, but the refrigeration energy consumption and the risk of frosting rise simultaneously, and there is no unfounded limit low temperature.
After the condensate is allowed to stand and stratify, the oil phase, I .e. the recovered n-pentane, is reused in the foaming process or the backspray storage tank according to the quality; the separated water phase is treated according to the conventional wastewater path. Its recovery comparison with other low boiling point media is shown in the following table:
| comparison dimension | n-Pentane | Common ester and ketone solvents |
|---|---|---|
| Boiling point range | About 36 ℃, very fast volatilization at room temperature | More than 56 ℃ |
| Condensation requirements | More than two stages of deep condensation required | Two-stage condensation is dominant |
| Condensate separation | Insoluble with water, easy to stratify after standing | Some varieties are miscible with water |
| Security Defense | Extremely flammable, the entire system is designed to withstand flammable media | Fortify according to flash point classification |
After layered dehydration and quality verification, the condensate can be recycled to foaming process or backspray storage tank. If the purity does not meet the requirements, it will be sent to the refining unit for treatment, which will be determined according to the measured quality.
Its boiling point is only about 36 ℃, and its saturated vapor pressure is high at normal temperature. When the condensation is not deep enough, a large amount of vapor still remains in the gas phase, and the recovery rate cannot be increased. Therefore, it is more secure to match more than two stages of condensation.
The collected air volume shall be approved according to the peak value of the process, and the branch and regulating valve shall be switched according to the working conditions to avoid the high condensation load due to the dilution concentration of the large air volume. Buffers can be added at points with large fluctuations to make the condensation working conditions run smoothly.
LuoyangWohong PetrochemicalEquipment Co., Ltd. provides design, manufacture, installation, commissioning and operation and maintenance services for low boiling point medium recovery devices such as n-pentane for foaming and chemical enterprises. Welcome to contact and exchange.
This article is organized by Luoyang wohong petrochemical equipment co., ltd. if you need to evaluate the recovery scheme of n-pentane and other media or conduct on-site investigation, please contact and exchange.
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