Catalytic purification of gas emissions

Increasing pollution of the atmosphere is a serious concern, and therefore the cleaning of gas emissions every year becomes more urgent. The largest source of emissions of harmful gases into the atmosphere are energy enterprises and road transport.

Purification of gas emissions is carried out in various ways, among which the most effective in many cases is the catalytic method of neutralizing and reducing the concentration of pollutants to the maximum permissible level. Catalytic purification is also preferable for economic reasons.

As a rule, catalytic methods are universal and can be used for deep cleaning of various process gases. With this method, industrial gases can be purified from nitrogen oxides and sulfur, carbon monoxide, harmful organic compounds and other toxic impurities. At the same time harmful impurities are transformed into less harmful and harmless, and sometimes even useful. The same method is used to purify the exhaust gases. In fact, this method consists in realizing the processes of chemical interaction of substances in the presence of catalysts, which leads to the conversion of impurities to be rendered harmless to other products.

Special catalysts accelerate chemical reactions, but do not affect the energy level of the interacting molecules and do not shift the equilibrium of simple reactions. Catalytic purification is promising for multi-component mixtures of effluent gas streams. For the purification of gases in industry, iron, copper, chromium, cobalt, zinc, platinum and other oxides are used as catalysts. These substances are treated with a catalyst carrier placed inside the reactor apparatus. It is necessary to monitor the integrity of the outer layer of the catalyst, otherwise the catalytic purification will not be carried out in full, and the emission of harmful substances can exceed the permissible standards.

The main requirement for the catalyst is the stability of the structure during the reaction. The search and manufacture of catalysts, not only suitable for long-term use, but also cheap enough, presents some difficulty that limits the application of the catalytic method. Modern catalysts must have selectivity and activity, resistance to temperature and mechanical strength.

Industrial catalysts are manufactured in the form of blocks and rings of honeycomb structure. They have a small hydrodynamic resistance and a high external specific surface. Catalytic purification of gases in a fixed catalyst is most often used.

In the industry it is possible to use two fundamentally different methods for the implementation of gas purification processes - a stationary and artificially created non-stationary regime. The transition to the preferential application of the non-stationary method is due to the higher processibility of the process, the increase in the rate of reactions, the increase in selectivity, the decrease in the energy intensity of the processes, the reduction of the capital costs for installation, and the reduction in operating costs.

The main direction of the development of catalytic methods is the creation of cheap catalysts that can work at low temperatures and be resistant to various substances. For concentrations below 1 g / m³ and for large volumes of cleaned gases, the thermocatalytic method requires high energy inputs and a huge amount of catalyst, so it becomes necessary to develop the most energy-efficient technological processes and equipment requiring low capital costs.