How to prevent explosions when using toluene as a solvent
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Our company uses toluene as a solvent to wash a chemical raw material. The raw material is added to the toluene solvent in a certain proportion, heated to dissolve it, and then cooled to induce crystallization for separation. How can safety be ensured during the production process, and what type of separation equipment is suitable for use during this separation step? Thank you!
Explosion limit of toluene (%): 1.2–7.0. It is a flammable and explosive substance as well as toxic; therefore, explosion-proof equipment must be used in production. It is necessary to prevent the formation of explosive mixtures during production, and equipment and pipelines should be properly grounded. Copper wires should be used for bonding between flanges (note: copper has a high resistivity, which can lead to the generation of static electricity). Regarding the separation process, I’m not aware of the properties of the other chemical ingredient used by your company. However, since the toluene you use is employed as a solvent, and if the product can be washed with water in the end, based on my experience, I think vacuum filtration might be a better option after the material has cooled down. Of course, the volatile toluene vapor should also be condensed before it is sent into the vacuum pump for removal.
Toluene is a flammable and explosive substance as well as toxic; explosive gas mixtures should be avoided during its production.
The washed chemical raw material is a pesticide fungicide; it is added to toluene in a certain proportion, heated to dissolve, kept at that temperature for a while, and then cooled to allow crystallization. Since this product contains certain amounts of chloride ions, it cannot be washed with water after centrifugation. Filtration under vacuum was previously used, but it had low production capacity, high levels of toluene in the raw materials, and high toluene consumption.
Organic solvent separation is generally done by suction filtration
It can’t be washed with water; what about rinsing it with toluene? Or use plate and frame filtration, cardboard filtration, or filter rod filtration?
The only solid-liquid separation method is filtration; suction filtration is carried out under vacuum, which results in significant losses of toluene. Personally, I think pressure filtration could be considered, but plate and frame filtration is not very suitable; a sealed filter press might be worth considering.
Use a closed-type explosion-proof centrifuge
The toluene storage tank should be properly grounded to prevent static electricity, equipped with a spray system, and fitted with a flame arrester or breather valve; if necessary, it should be sealed with nitrogen, ensuring that the resistance of the static grounding system is no more than 10 ohms； During feeding, ensure proper static electricity bonding at the pipeline transitions, with the bonding resistance not exceeding 0.03 ohms ； When the tank truck feeds material in, the resistance at the loading/unloading point should not exceed 100 ohms, and the resistance of the pipeline itself should not exceed 30 ohms ； A centrifuge is used for solid-liquid separation, with nitrogen protection during the centrifugation process