- •4. Purification, neutralization and recycling industrial waste products in technology of inorganic substances
- •4.1. Environmental problems of soda ash production
- •Control questions on the topic “Environmental problems of soda ash production”
- •4.2. Ways of processing the waste water and industrial waste formed at ammoniac saltpeter manufacture
- •Treatment and use of the waste water
- •Treatment of the vapour condensate by ion exchange method
- •Treatment of the vapours in gas washers
- •Control questions on the topic “Ways of processing of sewage and industrial wastes by ammoniac saltpeter manufacture”
- •4.3. Waste products formed at caustic soda manufacture and methods of their processing
- •Control questions on the topic “Waste products formed at caustic soda manufacture and methods of their processing”
- •4.4. Waste products of acid processing phosphate raw material. Removal of fluorine compounds. Waste water treatment. Processing solid waste products (phosphogypsum, limy sludge).
- •Possible ways of phosphogypsum processing
- •1. Manufacture of sulfuric acid and lime
- •2. Obtaining ammonium sulfate
- •Control questions on the topic “Waste products of phosphates acid processing”
- •4.5. Waste products of sulphuric acid manufacture. Methods of purification, processing and neutralization of solid waste products, sulphurous anhydride and waste water
- •Recycling of selenium sludge
- •Cleaning of departing gases from so2 and a fog of sulphuric acid
- •Sewage treatment
- •4.6. Waste products of phosphorus production. The characteristic of departing gases, dust, sludge and slag. Circuits of their clearing, neutralization and recycling.
- •Control questions on the topic Waste products of phosphorus production. The characteristic of departing gases, dust, sludge and slag. Circuits of their clearing, neutralization and recycling.
- •Literature
Control questions on the topic “Environmental problems of soda ash production”
1. Physicochemical properties and application field of soda ash.
2. Methods of soda ash production.
3. Stages of the soda ash production process.
4. What is the distiller liquid?
5. Kinds of waste products formed at soda ash production.
6. Explain the reduction ways of industrial waste amount at the manufacturing soda ash.
7. Which products can be obtained at cleaning and processing the distiller liquid?
8. The distiller liquid purification techniques.
9. Tell about methods of processing the sludge formed.
10. Call the stages of technical ammonium chloride production from the sludge.
4.2. Ways of processing the waste water and industrial waste formed at ammoniac saltpeter manufacture
Ammoniac saltpeter is one of the most widespread nitric fertilizers. In the chemical industry it is widely applied only a method of ammoniac saltpeter production from synthetic ammonia (or ammonia-containing gases) and diluted nitric acid.
The given process of ammoniac saltpeter production consists of the following stages:
1) Preparation of ammoniac saltpeter solutions by neutralization of nitric acid by gaseous ammonia or ammonia-containing gases;
2) Evaporation of ammoniac saltpeter solutions up to a melt;
3) Crystallization of the salt melt as granules, plates and fine crystals;
4) Cooling and drying of the salt;
5) Packing of a ready product.
Ammoniac saltpeter solutions are fed in an evaporation installation. The 65 % NH4NO3 solutions are evaporated in two stages. Main sources of polluted water are condensates of NHU apparatuses (neutralization heat utilization) and evaporating systems.
Kinds of the waste water formed at the ammoniac saltpeter manufacture: 1) waste water, which does not demand special purification – cooling water; 2) polluted waste water – vapour condensates and also the water from washing the equipment, floor, etc.
The waste water amount depends on the vapour condensation volume and way. Now many industrial enterprises use barometric condensers instead of surface ones. It allows to reduce considerably the formed waste water amount and to increase concentration of impurity in the water. So, at the vapour condensation in barometric condensers the ammonia concentration in the production water on the average makes 25 mg/l, ammoniac saltpeter concentration - 55 mg/l. At the replacement of these condensers on surface ones the NH3 concentration in the condensate grows up to 300-500 mg/l, and the NH4NO3 concentration – to 600-1800 mg/l. Total losses of ammonia and saltpeter with the waste water from barometric condensers make more than 90 % from the total shop losses. Usually NH3 loss on 1t of NH4NO3 makes 2-2,5 kg, HNO3 loss – 7-7,5 kg.
Treatment and use of the waste water
The most rational decision is use of the waste water of ammoniac saltpeter manufacture in nitric acid production for absorption of nitrogen oxides. However the presence of NH4NO3 in the waste water does not allow realizing this decision. For achievement of this goal it is necessary: 1) strongly to lower the amount of formed production water by replacement of barometric condensers on surface ones; 2) to purify the vapour condensate from NH3 and NH4NO3.
Now the vapour condensate is treated by ion exchange method or by washing the vapour in a plate type washer.