Regarding the methods of unloading vinyl chloride monomer
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The methods used for unloading vinyl chloride monomer (in tank trucks) currently include unloading under pressure using a vaporizer or compressor, or by pumping. Each of these methods has its own advantages and disadvantages. It is said that unloading under pressure using a vaporizer or compressor is not permitted according to regulations; I’m not sure if this is indeed the case. However, if pump unloading is used, phenomena such as pump cavitation and air locking can occur, affecting its performance. Please share your insights; thank you! This post was last edited by yhpsxj on 2009-4-26 21:23]
If unloading is done using a pump, an intermediate tank is placed between the pump and the tank truck; the material in the tank truck flows into the intermediate tank due to gravity, and then the pump is used to transport the material away. What regulations prohibit the use of compressors? Nowadays, compressors are used for unloading in many places
Unloading is done using a pump, with the gas phase being pressurized; the pressure only needs to be higher than the saturated vapor pressure of vinyl chloride at room temperature. Generally, 0.3 megapascals in winter and 0.4 megapascals in summer is sufficient. It can be pressurized with nitrogen, or by compressing vinyl chloride gas and then applying pressure.
A shielded pump or an explosion-proof gas compressor should be used
Agreed; we also encountered the problem of air locking when using a pump for unloading back then, but it worked fine after using N2 to apply pressure during unloading.
For the daily unloading of monomers, we use the pressure from behind the compressor to directly pressurize the gas phase in the container for unloading; however, with this method, it takes about 90 minutes to unload a container containing around 28 tons of monomer. If the pressure relief valve on the monomer tank is opened to relieve pressure into the gas holder without any flow rate control device at the liquid outlet of the individual tank, the unloading time can be nearly doubled. Unloading with a pump is not very effective, as pumping a large volume of fluid requires the operator to stay by the pump at all times; otherwise, the pump may experience vacuum conditions, emptying, or air entrapment. This leads to the pump running out of fluid and damaging the mechanical seal.
Too high a flow rate generates static electricity; don’t pursue speed too much. Also, ensure that the anti-static measures are properly in place
It is best to use a pump for unloading to save energy consumption.
Hello, regarding the Haiyou unit on the second floor: according to the regulations, it is not allowed to use compressors for unloading. Which regulation specifies this? Could you let me know? Thank you! But currently, the unloading of liquefied petroleum gas still relies mainly on compression for pressurized unloading.
Our successful unloading method: 1. Add a discharge pipe at the automatic discharge valve of the individual storage tank (next to the valve assembly for easy control), and add a balance pipe to the original tank’s balance pipe； Pipeline 1 leads to the unit pump (LPG pump) and then to the unloading platform, while pipeline 2 directly leads to the unloading platform ； Finally, remember to add a recovery pipeline after connecting the pipelines with valves, to facilitate conservation and environmental protection. Note: Contact the vehicle in advance to find out what type of connector is used (prepare a flexible metal hose for connection).