Background
The well-known mud phosphorus treatment methods are roughly divided into two categories. One is treatment during the production process, that is, the yellow phosphorus steam is passed through an electrostatic precipitator to remove impurities in the yellow phosphorus steam, so that the yellow phosphorus steam is purified. This way no mud phosphorus will be produced. However, this method is only suitable for large-scale yellow phosphorus enterprises, because the investment in electrostatic precipitator equipment is large, the technology is complex, and the operating costs are high, which is one of the main reasons why large-scale yellow phosphorus production enterprises currently suffer losses. The second is post-processing during the production process, that is, further evaporating mud phosphorus to obtain yellow phosphorus. Now almost all yellow phosphorus enterprises in the country use this method, processing about 70,000 to 80,000 tons of mud phosphorus every year. These mud phosphorus treatment methods generally adopt open heating and evaporation methods, and the operating temperature is 800-1000°C. Since the system is open, low-quality coal is used for open heating in order to reduce costs, causing soot-type environmental pollution. The open operation of the yellow phosphorus evaporation system causes phosphorus elements to be lost and re-oxidized into phosphorus pentoxide, forming acidic substance sedimentation. , destroying large areas of nearby vegetation, not only causing environmental disasters, but also causing resource loss (phosphorus recovery rate is only about 50%).
The purpose of this invention is to recover yellow phosphorus in mud phosphorus by using closed oxygen-free normal temperature drying, medium temperature purification and closed cooling. The recovery rate of elemental phosphorus reaches more than 90%, saving energy, reducing costs, and not causing environmental pollution.
Figure 1 is a process flow chart of the present invention. The raw material mud phosphorus with an elemental phosphorus content of 30-90% is added with the additive calcium salt, stirred evenly under sealed conditions, dried under vacuum conditions, and then purified in a medium temperature vacuum furnace. , the phosphorus steam enters the wet and dry two-stage cooling and recovery, and finally the finished yellow phosphorus is obtained. Most of the residue is silicate, which can be made into cement.
The purpose of adding the additive calcium salt before drying is to prevent harmful impurities such as arsenic from volatilizing along with the phosphorus element. During the vacuum purification process, no chemical reaction occurs. It is a physical process. The melting point of yellow phosphorus is 100°C. When the temperature of the vacuum furnace is -500°C, elemental phosphorus sublimates from mud phosphorus into gas, and the remainder is residue. Cooling recovery uses hot water circulation to cool the phosphorus vapor so that it can be recovered in a liquid state. 2. Process conditions 1. Drying: normal temperature, residual pressure -500mmHg;
2. Medium temperature vacuum purification: control temperature -500℃, residual pressure -500mmHg; 3. Cooling recovery: yellow phosphorus steam enters the cooling box and is cooled by indirect circulation with hot water. The yellow phosphorus is cooled into liquid and recovered, and the tail gas is passed through water A ring pump recovers residual yellow phosphorus.
Fig. 1 is a process flow chart of the present invention, and Fig. 2 is an equipment flow chart. In the figure, 1 is a drying box, 2 is a purification vacuum furnace, 3 is a cooling box, 4 is a water ring pump (2 units), and 5 is AC power supply, 6 is the inlet of raw materials and additives, 7 is the residue outlet chain extender, 8 is the outlet of finished yellow phosphorus, 9 is the cooling water inlet, and 10 is the cooling water outlet.
Compared to existing technology. This invention uses closed room temperature vacuum drying, medium temperature purification, and closed cooling to recover yellow phosphorus in mud phosphorus, so the recovery rate is high (up to more than 90%); the equipment is simple, energy consumption is low, and production costs are low. Environmental pollution is reduced.
Extraction method
The raw material is mud phosphorus from a certain factory containing 30% elemental phosphorus.
1. Technical conditions 1) Drying: filled with nitrogen, room temperature, residual pressure -500mmHg, dry until the mud phosphorus water content is less than or equal to 5%; 2) Purification: temperature 500°C, residual alcohol pressure -500mmHg; 3) recovery : 80°C hot water circulation indirect dry recovery section, the tail gas enters the water ring pump to wet recover the residual yellow phosphorus; 4) Add 0.5% calcium silicate by weight of the raw material as an additive before the raw material is put into drying, and stir evenly.
2. Equipment 1) Intermittent low-temperature drying oven, with a drying capacity of 2-3 tons per time; 2) Intermittent vertical medium-temperature yellow phosphorus purification vacuum furnace, with a material processing capacity of 2.5 tons per time; 3) Two-stage cooling box One.
4) Two water ring pumps, the maximum air pumping capacity is 5.4m3/S when the ultimate vacuum degree (residual pressure) is 450-710mmHg; the water is filtered and recycled.
