EFFICIENCY IMPROVEMENT OF VENTILATION IN TANKS WITH OIL-PRODUCTS

Technical modernization and reconstruction of industrial enterprises are fast always connected with performance of repair works, anti-rusting coating and performance of hot works on tanks. Each year the quantity of accidents on tanks increases. The main reason for such growth is the fact, that large percentage of the tanks is overaged. The aging of the operated upright steel tanks amounts to 60–80 %. This article set out the main reasons for breakdown of the steel tanks. The fires, happened in tanks from 2001 to 2012, and their courses have been analyzed. Cleaning of the tanks from oil residues at preparation for hot works is a complex and explosion/fire hazardous process step. In the present time, as a matter of practice, cleaning of the tanks by means of forced ventilation is widely spread. The article is devoted to efficiency improvement of ventilation in the tanks with oil-products. In order to find and study new ways of cleaning (degassing) of the tanks with oil residues, a number of experiments for forced ventilation with air of combustible gases in an experimental tank and experimental pilot stand. Experimental researches of the mass exchanging processes at ventilation inside the experimental tank and experimental stand were carried out under conditions of fixed capacity of the ventilator according to the following inlet-air circuits: no. 1 — air-stream feed “innovative”; no. 2 — air-stream feed “counterflowing”; no. 3 — air-stream feed “traditional”; no. 4 — air feed “mixed”. In the course of processing of the outcomes of the experiments the following common factors of changes in various hydrodynamic conditions have been recognized: concentration, mass flow density, supply-air motion inside the tank and emission rate at ventilation of the tank. Basing on the experimental-theoretical research engineering approaches for estimation of evaporation rate of oil-products at the bottom of the ventilated tank were developed. The main efficiency criterion of the considered approach for preparation of the tanks for hot works is ventilation time. The duration of ventilation depends on ventilator capacity, temperature of the incoming air, evaporation surface, type of oil product and method of incoming-air feed to the inside of the tank. Efficiency ratio is taken as the quantitative value for comparison of different inlet-air circuits. On the basis of the resulting data concerning efficiency estimation of the investigated approaches for preparation of the oil-and-gas complex tanks for repair, by means of forced ventilation, it may concluded, that most intensively evaporation progresses at organization of air exchange according to circuit no. 1. For this approach on 04.03.2014 the decision on grant was obtained at the Federal Service for Intellectual Property (Rospatent). The article presents estimation and efficiency ratio is determined in the estimation formula of the evaporation rate.