The valve for the hot blast stove should be sturdy, can withstand a certain temperature, ensure good sealing under high pressure, minimize leakage, flexible switch, easy to use, easy to repair and operate.
(1) Valve classification
The valves of the hot blast stove system can be divided into three basic forms according to the working principle:
1 gate valve. The opening and closing direction of the gate of the gate valve is perpendicular to the direction of gas flow, and the structure is complicated, but the airtightness is good, and is suitable for cutting of clean gas.
2-disc valve. The moving direction of the disc valve disc is parallel to the airflow direction. The structure is relatively simple. It is mostly used to cut off dusty gas, and the sealing performance is poor. When the airflow passes through the valve, the direction is turned 90°, so the resistance is large.
3 butterfly valve. The butterfly valve is a flap with a shaft that can rotate freely in the middle, and its opening degree can adjust the gas flow. It is flexible and accurate, but it has poor sealing properties and cannot be used for cutting.
Valves can be divided into combustion system valves and air supply system valves according to their applications. There are gas regulating valves, gas shut-off valves and flue valves belonging to the combustion system valves; there are venting valves, hot blast valves, cold air valves, mixed air valves, and exhaust gas (wind) valves belonging to the air supply system.
(2) Gas regulating valve. A butterfly valve that regulates gas flow. When the combustion is automatically controlled, the gas regulating valve is driven by an electric actuator.
(3) Gas shut-off valve. The tie type valve is used to cut off the gas during the air supply period.
(4) Flue valve. The disc-type valve is used for opening the hot blast stove during the combustion period to discharge the exhaust gas into the flue; in the air supply period, it is closed to block the connection between the hot blast stove and the flue.
(5) Combustion valve. Water-cooled gate valve, which is only used on blast furnaces using sleeve burners. It is used to feed gas into the burner during the combustion period, and cut off the gas pipeline and hot blast stove during the air supply period. Contact.
(6) Cold air valve. The brake valve is a gate of cold air entering the hot blast stove, installed on the cold air branch pipe, closed during the combustion period, and opened during the air supply period. There is a small valve for pressure equalization on the big gate. This is due to the hot air stove. Before and after closing the flue valve, the furnace is at the same level of the negative pressure of the flue. The pressure on the cold air branch is the blast pressure. The pressure difference between the plate and the plate is very large, and it is impossible to directly open the ram. Therefore, the main valve has a small pressure equalizing valve hole, which is easy to open, so that the cold air is first poured from the small hole, and after the pressure on both sides of the ram is equal, The main valve is easy to open.
(7) Hot air valve. The brake valve is opened during the air supply period and closed during the combustion period, and is used for the connection between the hot air furnace and the hot air duct during the combustion period.
(8) Exhaust valve. Also known as waste air valve, bypass valve, disc valve. Its role is two: first, when the blast furnace needs emergency air release, and the venting valve fails or the furnace is unable to perform the air blowing operation, the wind can be released through the waste valve; second, when the hot blast stove is changed from the air supply period to the combustion period When the furnace is filled with high-pressure air, and the underside of the flue valve disc is the flue negative pressure, the upper and lower pressure difference of the flue valve disc is very large, and another small valve must be used to introduce the high-pressure waste wind into the flue. Reduce the pressure inside the furnace. Although the temperature of the exhaust gas is high, since the action time is short, cooling is not required. For large high-pressure blast furnaces, there is a small pressure equalizing valve in the center of the exhaust valve disc. The working principle is the same as that of the cold air valve.
(9) Mixing valve. The function of the mixed air valve is to infiltrate a certain amount of cold air into the hot air furnace main pipe to keep the hot air temperature stable. It consists of a mixed air regulating valve and a mixed air blocking valve. The mixed air regulating valve is a butterfly valve, and its opening degree is used to control the amount of cold air mixed. The mixed air shut-off valve is a gate valve, which is designed to prevent hot air or blast furnace heart gas from entering the cold air duct when the pressure of the cold air duct is lowered (such as blast furnace rest). When the blast furnace is off, the valve is closed to cut off the connection between the blast furnace and the cold air duct, so the valve is also called a mixed air protection valve.
(10) Air release valve and silencer. The venting valve is installed on the cold air duct between the blower and the hot blast stove group, and the blower is used to discharge some or all of the blast to the atmosphere by the venting valve without stopping the operation of the blower.
By learning the hot blast stove process and its valve principle, the difference between the valve airflow direction and the bearing direction should be recognized. As long as we master the valve performance requirements, familiar with each valve manual, apply the construction specifications to correctly install the valve, so that the installation project meets various technical indicators and requirements, it can reduce unnecessary losses caused by rework.