How to recycle the solvent tail gas discharged intermittently from the workshop? Direct answer: the difficulty of intermittent working condition recovery is not in the treatment process, but in the collection and buffer-discharge for a while, the concentration and gas volume fluctuate greatly, and the device cannot follow the discharge. the solution is centralized collection and buffer configuration of negative pressure pipe network: each discharge point is connected to a closed collection pipe network, a buffer tank or buffer space is set at the end to iron out the fluctuating gas volume, and the device is automatically started and stopped according to the buffer tank pressure, conversion of intermittent emissions into quasi-continuous operation on the device side. The reaction, distillation, drying, and tank breathing links in fine chemical and pharmaceutical workshops are mostly intermittent emissions. This configuration idea is the mainstream practice for such conditions. This article clearly explains the key points regarding data collection methods, buffer design, and the coordination of start-up and shutdown procedures.
Collection is a precondition for intermittent working conditions: the emission points are scattered, the time periods are staggered, and the single-point single-machine matching device is uneconomical. The common practice is to lay a closed negative pressure pipe network in the workshop to connect the reaction tail gas, distilled non-condensable gas, vacuum pump exhaust and storage tank respiration in a unified way. The key point of pipe network design is pressure balance-the back pressure of each discharge point should be coordinated, the import sequence of high concentration point and low concentration point affects the end concentration level, and the design stage is calculated point by point according to the discharge list. The open discharge point is changed to closed feeding and closed transportation first. The amount of air leaked by the open itself is more than that recovered by the pipe network. The collection source is not closed. No matter how large the back-end device is, it is useless. This account should be counted in front.
The function of buffer is to cut the peak and fill the valley: the air volume during the peak emission period is stored in the buffer space first, the device is eaten at a constant speed according to its own processing capacity, and the buffer is vacated during the trough period to wait for the next wave. The buffer volume is calculated according to the emission rhythm-the larger the single emission and the shorter the interval, the greater the buffer required; the symptoms of insufficient buffer are frequent start-up and stop of the device, tank pressure limit, and the excessive cost is investment and land occupation. The liquid level and condensate discharge of the buffer tank are included in the daily inspection. The liquid accumulation in the tank accounts for the volume, and the buffer capacity shrinks quietly. The operation rhythm of the device is disorderly. Such problems are more obvious in rainy season and high humidity conditions. The inspection list should be listed separately.
The start-stop value of the device is set according to the buffer tank pressure, the pressure starts at the upper limit and stops at the lower limit, which is logically the same as the tank pressure recovered three times at the gas station. The number of start-stop times under intermittent working conditions is naturally large. The selection of electrical and pump valves is checked according to frequent start-up working conditions. The frequency conversion configuration can suppress the start-stop impact. Interlock protection shall be matched according to the medium characteristics: alarm and cut-off of concentration, temperature and pressure exceeding the limit, and electricity in explosion-proof area shall be selected according to the grade of dangerous area. The start and stop records are written into the operation ledger. Abnormal frequency changes are often due to changes in the working conditions on the collection side. Check the source first and then move the device. The order is not reversed.
| Segment | key points | FAQ |
|---|---|---|
| Emission inventory | Point by point registration concentration gas period | Missing intermittent point |
| Confined collection | Open to closed feeding transfer | Source open air leakage |
| Negative pressure pipe network | Accounting for back pressure balance at each point | High and low concentration into disorder |
| Buffer Configuration | Volume according to discharge rhythm | Accumulated fluid volume buffer shrinkage |
| Start-stop setting | Automatic start and stop of upper and lower pressure limits | Frequent start-stop damage pump valve |
| Interlock protection | Overtemperature and overpressure concentration cut-off | Explosion-proof type selection mismatch |
Buffering and automatic start-up and stop are the common practice: the device specifications are selected according to the average gas volume instead of the peak value, thus saving investment; Special high-concentration high-risk emission points, separate small processing units are directly connected, and do not enter the public pipe network.
Calculate according to the difference between the single maximum emission and the processing capacity of the device, and then leave a safety margin.
The membrane module itself is not afraid of intermittent operation, and replacement and protection shall be done during start-up and stop to avoid long-term contact with high-concentration static gas on the membrane surface. The buffer configuration itself is the protection of the membrane module, and the gas volume is stable only when the working condition of the membrane is stable.
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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