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Analysis of Four Pollution Sources in Supercritical CO2 Extraction

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Pollution Sources 1#: Source of noise pollution

The main sources of noise pollution in supercritical CO2 extraction equipment can be divided into several parts: compressor, pump, water flow noise of water cooler, and gas throttling and venting noise.

Compressor Noise Sources

The noise level of the compressor is about 90m(A), mainly including the noise of the feed gas compressor and the noise of the compressor for cooling the condenser.

The noise of the feed gas compressor comes from the compression of the unit and the noise of the motor. When the gas finishes working in the compressor, the gas pressure pulsation will occur. The gas pressure fluctuation in the exhaust pipe will cause the pipeline pulsation. Exhaust noise with high energy and many components is generated.
Usually, the main component of the exhaust noise at the power end of the compressor is the periodic noise with the compressor suction and discharge frequency as the base frequency, and the noise caused by the wear of the valve plate is mixed in the middle.
The noise of the condenser refrigeration compressor mainly comes from the uncoordinated loading of the high-pressure end and the low-pressure end, such as too much loading on the high-pressure end and too little loading on the low-pressure end, which causes the vibration of the unit;
In addition, the noise of the air driven by the motor fan during the normal operation of the refrigeration compressor is also one of the sources of compressor noise.

Pump Noise Sources

The pumps of the supercritical CO2 fluid extraction device mainly include a cooling water circulation pump, Co-solvent pump, liquid material delivery pump (when the material is liquid) or solid material conveyor (when the material is solid), rotary vane vacuum pump, condensation Lubricating oil screw pump, etc.;
The noise of the lubricating oil screw pump of the refrigerator increases with the increase of the discharge pressure of the refrigerator, but because its position is close to the refrigerator, the overall noise level of the refrigeration unit is increased;
The noise level of the material pump and circulating water pump is relatively low in the device, but it will have a superimposed effect on the noise of the machine pump, which will increase the total noise level.

Water cooler water flow noise

The water cooler is mainly used for the initial cooling of the compressed carbon dioxide gas. The water flow noise of the water cooler comes from the noise generated when the cooling water column falls freely (the water pump is pressurized) and splashes on the water surface of the water cooler sump. Numerous “swirling vortices” are formed on the water’s surface. The continuous formation and rupture of these swirling vortices, as well as the sharp fluctuations in pressure, radiate energy in the form of sound waves. The greater the water column drop, the greater the noise.

Noise generated by gas throttling and venting

After the supercritical CO2 fluid flowing in the pipeline of the supercritical CO2 fluid extraction device enters the extraction kettle to extract the material, throttling will occur when it flows through the valve and the variable-diameter pipe enters the separator, etc., resulting in throttling noise. Gas flow noise is generated by safety valve opening, productive venting, etc.

Pollution Sources 2#: Source of air pollution

The main sources of gas pollution in supercritical CO2 fluid extraction equipment include: when Co-solvent is used, organic gas leakage caused by poor sealing of the equipment; in addition, there is also the odor emitted by the mixture of refrigerant and condenser oil, and the product during sampling Steam, the mixture of lye and water vapor used in cleaning equipment, etc.

Pollution Sources 3#: Sources of oil and water pollution

The oil pollution of the supercritical CO2 fluid extraction machine comes from a small number of raw materials scattered or discarded during the loading, unloading, and cleaning of the device, carbon dioxide compressor lubricating oil, condenser refrigeration oil, etc., of which lubricating oil occupies a large proportion. The water pollution of the device mainly comes from the flushing water and part of the cooling water of the equipment and site. In principle, the flushing water does not contain oil, but because a small amount of the above-mentioned oil is scattered or discarded in some places of the device, it enters the water body during flushing and causes water pollution.

Pollution Sources 4#: Solid source of pollution

The objects treated in the supercritical CO2 fluid extraction process are mostly plant or animal raw materials. Due to the particularity of processing raw materials and processing processes, there are three possible sources of solid pollutants in the production process: dust generated during the crushing process of solid extracts before feeding Scattered or discarded raw materials, and processed solid raffinate during the feeding process, among which the most important one is the processed solid raffinate because a large amount of raffinate will bring a series of difficulties to stacking and handling.

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