About phosphorus trichloride production and technology

Preparation or source】Pour dry chlorine gas into the mixed solution of phosphorus and phosphorus trichloride, and then refine it through distillation. [Use] Used in the preparation of pesticides trichlorfon, phosphorus sulfur chloride, * * , phosphorous acid, phosphite ester, also used as chlorinating agent, catalyst, solvent, etc.

2# river2058 Which domestic design institutes are capable of engineering design of phosphorus trichloride? Who are the manufacturers?

The technology is already very mature. Just find an experienced engineer to be responsible for the design, and then go to the design institute to get it stamped.

It is best for phosphorus trichloride production to be supported by chlor-alkali production, otherwise the market competition will not be strong.

I agree with what you said above. For example, in Jiangsu and Zhejiang, many factories either have their own supporting chlor-alkali, or they set up factories around chlor-alkali production plants. In short, they need to have a source of raw materials. In addition, the transportation of yellow phosphorus is also important. Dry chlorine gas is passed into a mixed solution of phosphorus and phosphorus trichloride, and then refined through distillation. raw material: Yellow phosphorus, liquid chlorine safety in the manufacture of phosphorus trichloride. After the yellow phosphorus is heated and melted, a special reciprocating pump under the yellow phosphorus liquid is input into the reactor where an appropriate amount of phosphorus trichloride has been added as the mother liquor. The chlorine is passed through to carry out an exothermic reaction. The generated phosphorus trichloride vapor enters the distillation tower for distillation, and the phosphorus trichloride flows into the storage tank (see Figure 5-3). Reaction formula 2P + 3Cl2→ 2PCl3+ 313.95kJ/mol (yellow phosphorus) (chlorine) (phosphorus trichloride) The process flow is shown in Figure 5-3. Figure 5-3 Process flow chart of phosphorus trichloride (1) Melting phosphorus Put yellow phosphorus into the melting tank to heat and melt. Yellow phosphorus is a self-igniting substance and needs to be stored in water. It is easy to spontaneously ignite when it leaves the water. Therefore, the molten phosphorus tank must be filled with nitrogen or carbon dioxide to drive out the air before feeding. When feeding, move quickly to prevent spontaneous combustion. The melting point of yellow phosphorus is very low, and the heating temperature does not need to be too high. It can be heated with interlayer hot water. (2) Reaction Yellow phosphorus reacts with chlorine in the reactor to generate phosphorus trichloride. It reacts quickly and releases a lot of heat, which is very dangerous. ①During the reaction, an appropriate amount of phosphorus trichloride, which is called "base phosphorus" in production, must be added first. After the yellow phosphorus and phosphorus trichloride are mixed, chlorine gas is introduced for the reaction. This is safer. The content of "bottom phosphorus" must also be measured regularly during production to avoid making it too little. ②The ratio of yellow phosphorus to chlorine must be appropriate. If the amount of yellow phosphorus is insufficient, the chlorine gas will interact with phosphorus trichloride to form phosphorus pentachloride. The latter is a white solid that sublimates easily and often blocks pipes, causing accidents. If the amount of phosphorus pentachloride is already large, when yellow phosphorus is added, it will immediately react violently with the yellow phosphorus and reduce to a large amount of phosphorus trichloride. The reaction is as follows: 3PCl5 +2p → 5PCl3 (phosphorus pentachloride) (phosphorus trichloride) During the reaction process, due to the high temperature generated, a large amount of phosphorus trichloride vaporizes, causing the pressure to rise and flushing to occur easily. After punching, yellow phosphorus will be ejected together. Yellow phosphorus will spontaneously ignite when exposed to air, easily causing a fire. ； Sometimes an explosion occurs before the material is flushed, and the consequences are extremely serious. There have been lessons learned from accidents in production and we must be fully vigilant. Therefore, a special submersible reciprocating pump is used to transport molten yellow phosphorus. Using this kind of pump to transport yellow phosphorus can prevent the added amount of phosphorus from being too much at one time, and can prevent violent reactions with phosphorus pentachloride causing explosions or material flushing. ③The reaction generates a lot of heat and must be cooled in time. The cooling method should be to spray cold water along all sides of the reactor wall. It is not advisable to use the method of passing cold water through the interlayer. In case the wall leaks, the pressure of the interlayer cooling water will cause the water to enter the reactor and react violently with phosphorus trichloride to cause an explosion. PCl3 + 3H2O → H3PO3+3HCl↑ (phosphorous acid) (hydrogen chloride) Even if the spray method is used, the reactor must be inspected frequently to prevent leakage. The same goes for condensers. ④The chlorine gas pipe must be inserted into the bottom of the reaction solution. If the pipe is broken, chlorine reacts with phosphorus trichloride on the liquid surface to form phosphorus pentachloride: PCl3+Cl2→PCl5 (phosphorus pentachloride) is prone to explosion or charge when adding molten phosphorus. ⑤To control the "bottom phosphorus" liquid level in the reactor, a bottom phosphorus float instrument, or "bottom phosphorus float" can be used. “"Bottom phosphorus float" can generally be made based on the mixing proportion of yellow phosphorus and phosphorus trichloride at a certain temperature in the reaction tank. An iron rod is installed on the upper end of the buoy, and a solenoid transformer is wrapped around it, and then connected to the instrument for indication. Depending on the height of the buoy and the current generated, the height of the "bottom phosphorus" liquid level can be determined. (3) Distillation The hot vaporized phosphorus trichloride coming out of the reactor is rectified in the distillation tower to obtain the phosphorus trichloride condensate and enter the storage tank. If phosphorus trichloride contains high levels of free phosphorus, spontaneous combustion of yellow phosphorus will cause a combustion explosion during deacidification and the next step of the chemical reaction. Therefore, the quality of phosphorus trichloride should be strictly controlled.

Just find someone with experience. The technology is quite mature, but it is still difficult to do it well.

The fourth floor said it very well. The key to this product is not the technology. This product is a substance in the international list of hazardous chemical weapons. There are certain problems in project approval. In addition, the transportation of this substance is too dangerous, so ordinary manufacturers use their downstream products as projects for supporting production and generally do not take out. If you really want to take out, if there is a problem with such a dangerous substance during transportation, the company's top leaders will face a lot of safety pressure. It is not worth it to face jail for a small amount of money.

The production process of phosphorus trichloride is very mature and the investment is not large. However, this product is controlled by the International Convention on the Prohibition of Chemical Weapons. Obtaining evidence is very difficult and the control is very strict. Relocation of some original devices is very troublesome, let alone new projects! This product is indeed a great product for balancing chlor-alkali businesses.

This post was last edited by Hengshan Tumbler on 2010-3-26 09:15.: “"This product is indeed a good product for balancing chlor-alkali companies." I don't think so. In fact, the chlor-alkali industry should be considered a basic large-scale chemical industry. Small-scale products may not necessarily have competitive advantages. For large-scale basic chemical industries, it may be better to make downstream vinyl chloride to balance chlorine. This is how Hengyang Jiantao achieved balance and embarked on a vinyl chloride project of hundreds of thousands of tons. For the product phosphorus trichloride, most of the technical manufacturers of organophosphorus pesticides are already very mature, and the technical threshold is very low. The production equipment is not complicated, and it has the characteristics of low investment and high output.

Technology is easy to handle, but the connection between products and industries is difficult.