5. Clearing of industrial emissions of gases and forming pairs impurity.

Methods of clearing of industrial emissions on character of course of physical and chemical processes can be divided into 5 basic groups:

1. Washing of impurity by solvents (absorption);

2. Washing of impurity by the substances connecting impurity chemically (hemosorption);

3. Absorption of gaseous impurity by firm active substances (adsorption);

4 Thermal neutralization of entering gases and absorption of impurity by каталитического transformations;

5. Division of a газо-air mix into components by absorption of one or several components.

Washing of impurity by solvents (absorption). Motive power is the gradient of concentration on border of environments. The component of a gas-air mix dissolved in a liquid owing to diffusion gets into internal layers of an absorbent. Process proceeds the more quickly, than it is more interface of environments factor of diffusion. For removal from technological emissions of such gases as ammonia, fluoric and chloride hydrogen expediently as absorbers to use water since thus high solubility of harmful substances is reached.

The method of adsorption is based on physical properties of some firm bodies with ultramicroscopic structure actively to take and concentrate on the surface separate components from the gas environment. It is subdivided into physical adsorption and hemosorption. At physical adsorption of a molecule of gas stick to a surface of a firm body under action of molecular forces of an attraction. Heat liberated at it depends on forces of an attraction and on size coincides with heat of condensation of gas. Advantage of physical adsorption - convertibility of process.

Hemosorption. In a basis hemosorption chemical interaction between adsorbent and adsorbed substance lays. Forces of coupling operating at it it is much more than at physical adsorption. As adsorbents apply the substances having a greater surface on a mass unit. So, the specific surface of the activated coal reaches 10⁵ - 10⁶ м²/kg. It is applied to clearing gases of organic substances, with removals of unpleasant smells.

Thermal neutralization. It is based on ability of substances to be oxidized up to nontoxical at presence of a heat and free oxygen. There are three schemes of thermal neutralization of gases: 1) direct burning in a flame; 2) thermal oxidation; 3) каталитическое burning. Direct burning and thermal oxidation proceed at temperatures 600-800°С, and каталитическое burning - 300-400°С.

Direct burning should be used when departing gases have the significant energy necessary for burning. At проектировке devices of such type it is necessary to know limits of completion of burnt solutions for maintenance of burning without additional heat. Other problem complicating direct burning is connected by that at temperature 1800°С and surplus О₂ other source pollution - NO² is formed. An example of direct burning is burning the hydrocarbons containing toxic gases directly in a torch of a torch.

Thermal oxidation is used when departing gases have a heat, but in them insufficient quantity О₂. The important factors which should be considered at designing such devices are time, the temperature, turbulence. Time should be sufficient for full combustion of all components and reach 0,8 with. Turbulence characterizes a degree of mechanical hashing of the gas necessary for effective contact with О₂ and combustible substances.

Каталитический the method is used for transformation of toxic components of industrial emissions into substances harmless and less harmful to an environment by introduction in system of the catalyst. Каталитические methods are based on interaction of deleted substances with one of components present in gas. The catalyst cooperating with one of reacting substances forms intermediate substance which breaks up to harmless components.

Biochemical methods. Are based on ability of microorganisms to destroy and transform various connections. Destruction occurs under action of the enzymes developed by microorganisms.

Methods of clearing of exact waters. In sewage treatment from firm particles depending on their properties, concentration and a solution is carried out by methods: filtering, upholding, branch of firm particles in a floor of action of centrifugal forces, a filtration.

Filtering - a primary stage - sewage treatment which is intended for allocation from sewage of insoluble impurity in the size up to 25мм, and also fibrous pollution. Filtering is carried out пропусканием sewage through lattices and волокноулавливатели. Lattices are made of metal cores or armature with a backlash between them of 5-20 mm and established under a corner 60°to horizon. Lattices more often mechanically by means of a rotary raker and less often manually are cleared. Thus the impurity which have been removed from a lattice are crushed and dumped back in sewage, than quality of the air and water environment worsens. For elimination of this lack use lattices - crushers which crush impurity, not taking them from sewage.

Upholding is based on feature of sedimentation of firm substances in a liquid. Sewage treatment is carried out in песколовках and sediment bowls. Depending on a direction of movement of sewage песколовки happen horizontal to rectilinear and circular movement of water aerated.

Filtration of sewage it is intended for their clearing from it is thin dispersive firm impurity. Process is used after physical and biological methods of clearing. For sewage treatment 2 kinds of filters are used: granular in which the liquid proceeds through nozzles of porous materials (sand), and microfilters, which elements are made of the connected porous materials.

Clearing from oil products depending on structure and concentration is carried out by upholding, processing in hydrocyclones, a filtration and flotation.