Disposing Hydrogen Chloride in Ammonium Paratungstate Production

In the process of producing ammonium paratungstate, the classical method to decompose the sodium tungstate is using hydrochloric acid (HCl). Hydrochloric acid coming from HCl gas dissolved in water, a strong acid with prosperities of transparent (the high concentration of hydrochloric acid presents yellow), irritating odor and strong corrosion. Hydrochloric acid is highly volatile, when concentration of HCl in the water more than 20.22%, a small quantity of water containing hydrogen chloride volatile; when concentration of HCl in the water more than 37%, HCl gas volatiles. HCl gas will quickly combine with water vapor in the air which is called the white mist. In the industrial APT production, a large number of hydrogen chloride gas volatile and went into atmosphere, forming acid rain which is causing serious harm to humans, animals, plants, buildings and so on. For the requirements of environmental protection and recycling, we need to deal with HCl waste gas.

Acid decomposition is an exothermic process, in the production of APT, a large number of heat released with the continuous reaction, then HCl gas will continue to volatile with the raising temperature. Disposing hydrogen chloride need to consider the economic, social, environmental benefits, analyze with the following three methods.
1.    Cleaning process
Consider to change the production process, use the minimum input to adjust the process route, in order to avoid the production of HCl. For the traditional preparation of APT process, the production of HCl gas is inevitable, because hydrochloric acid is a main material. However, we can control reaction speed and reaction temperature, and then achieve the purpose of reducing the amount of HCl volatilization;
2.    Acid-base neutralization
HCl is an acid gas. The simple, Acid-base neutralization is the direct and effective way to dealing. A large number of low concentration alkaline waste water is discharged in tungsten alkali decomposition process; so we can use them for washing HCl gas to eliminate HCl waste gas.
3. Solidification
MH3 and HCl are both generated in the APT production, and these two gases are very easy to produce solid ammonium chloride, also achieve the goal of disposing hydrogen chloride.

• < Prev
• Next >