The design characteristic of the hot blast valve and its effect on blast furnace temperature during the switching period of the air heaters

Abstract

The article considers the structure and characteristics of a hot blast valve which is traditionally installed on air heaters of blast furnaces of domestic metallurgical plants. The hot blast valve connects the heated air heater of the blast furnace to the hot blast pipeline, that is, it transfers the air heater from the heating mode to the blowing mode. It is a water-cooled gate valve with a round bore and a semicircular movable gate, which is moved by an electric actuator. The main characteristics of any valve are its constructive, throughput and working characteristics. Constructive characteristics establish the dependence of the flow area on the movement of its gate, and the working characteristics establish the dependence of the flow rate of the substance on the movement of its gate under operating conditions. The cold blast valve is installed at the inlet of the air heater and during the period of its opening the cold blast is supplied to both air heaters, cooled and hot. As this takes place, there is no blast pressure drop between the air heaters valves, since we have a parallel connection of the blast pipelines with fully open hot blast valves of the cooled and heated air heater. Under such operating conditions of the air heater valves, the design characteristic of the valve becomes its working characteristics and its area determines the flow rate of the blast through it. In this regard, in order to analyze the effect of the valve operation on the hot blast temperature during the air heater switching period, it is necessary to find its design characteristic. For this, an analytical method was used to find a mathematical expression for this characteristic, an analysis was made of the change in the flow rate of blast through the cold blast valve when it was opened and closed during the air heater switching period. In this case, in the process of opening the cold blast valve of the heated air heater, the ratio of the amount of blast, which passes through the heated and cooled air heater, changes, which causes an increase in the blast temperature and reaching a certain maximum of it. The availability of a mathematical description of the working characteristic of the cold blast valve makes it possible to further analyze the temperature change during the air heater switching period and prevent its uncontrolled change