The driving force of membrane separation oil and gas recovery comes from the vacuum on the permeation side: the vacuum degree is stable and unstable, which directly determines the permeation and recovery rate, and the vacuum pump is the heart of this driving force. The pump type is wrong, either the vacuum degree is not filled with membrane white, or the operation and maintenance cost is ridiculously high. Water ring pump, dry pump and rotary vane pump have their own positions in membrane recovery. Most of the differences in selection lie in the unclear understanding of working conditions. In this paper, the characteristics of the three types of pumps, applicable scenarios and configuration points of comparison clearly, selection and transformation projects can be used as a reference.
The water ring vacuum pump has simple structure, high pumping speed and low cost. The liquid ring has its own seal and is not delicate to dust and liquid droplets. The short board is that the working liquid should be continuously supplied, the waste liquid entrained by exhaust should be collected and treated, and there is also an antifreeze topic in winter. The dry vacuum pump has no working liquid, stable pumping speed, no pollution of the pumped components, high quality of recovered gas, high cost and high maintenance accuracy, and suitable for scenes requiring high cleanliness of medium; the rotary vane pump has high limit vacuum and small volume, which is suitable for small gas volume skid-mounted devices, but the oil mist emission and oil change cycle are the burden of operation and maintenance, and the atmospheric volume scene is not economical. There is no all-round type for the three types of pumps, and only when they match the working conditions can they have high and low performance.
The selection is based on four parameters: the pumping volume is matched according to the design permeability of the membrane module, leaving a margin; The limit vacuum is determined according to the osmotic side pressure required by the membrane process, and the membrane method recovery is mostly in the medium vacuum range, so it is not necessary to pursue a high limit. The pumped medium contains liquid and dust-the tail gas containing condensate is friendly to the water ring pump, and sufficient gas-liquid separation should be provided before the dry pump; operation and maintenance conditions-whether there is a site for drainage collection, whether there is antifreeze conditions in winter, and the skill reserve of operation and maintenance personnel. After the four parameters are matched, the pump type will naturally float out: water ring and dry type are the main types in large and medium-sized stations, and small skid-mounted rotary vane is common.
There are three ways to optimize the configuration: frequency conversion control automatically regulates speed according to vacuum degree, which not only protects vacuum but also saves electricity under load fluctuation; Gas-liquid separation and filtration in front of the pump are matched according to the sensitivity of the pump type-water ring pump can be a little rough, and this stage in front of dry pump cannot be saved; The standby and switching strategies are determined according to the importance. One for continuous production scenarios, one for one pump and one spare part for intermittent operation. The installation of the pump also has details: the pipeline is short and straight to reduce the loss along the way, the check valve prevents the pump from turning upside down, and the receiving and collecting system of the drain port is not directly discharged. These small items are fixed in the drawing stage, which is more convenient than rectification after putting into operation.
The operation and maintenance caliber goes with the pump type: the water ring pump stares at the water quality of the working fluid and the replenishment cycle, the dry pump stares at the gear box and the cooling system, and the rotary vane pump stares at the oil level and the oil mist separator. The spare parts package is listed according to the pump type, and the wearing parts are always kept. The maintenance rhythm of the pump is combined with the cleaning cycle of the membrane to reduce the number of shutdowns.
| Pump type | Advantage | Applicable scenarios |
|---|---|---|
| Liquid ring pump | Large pumping speed and low cost | Large and medium-sized liquid-containing conditions |
| dry pump | High working liquid and gas quality | High cleanliness requirements |
| rotary vane pump | High ultimate vacuum and small volume | Small skid |
| Selection parameters | Vacuum medium operation and maintenance | Four-item Pair Finished Pump Type |
| Configuration Optimization | Frequency conversion separation standby | The drawing stage is fixed |
| Operation rhythm | Combine with Membrane Wash Schedule | Spare parts stock |
According to the calibration curve of the membrane process, the set values of different membrane components and working conditions are different. Daily management looks at the stability of vacuum degree to the set value, not blindly pulling up.
First check cavitation and bearing: water ring pump is prone to cavitation due to insufficient water supply, and dry pump bearing wear and noise is gradual. Accompanied by vacuum fluctuation, check the pipeline seal and check valve simultaneously.
Check the three parameters: pumping capacity, limit vacuum and medium compatibility, and they can be used if they match. Before the old pump, it is suggested to separate and filter the supplementary gas and liquid, and re-calibrate the operating parameters.
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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