Reheating Furnace

Reheating furnace for steel rolling mill line is a device (an industrial furnace) that heats a material or a workpiece (generally a metal) to rolling forging temperature in the metallurgical industry.

Structure and composition

According to the distribution of furnace temperature, the furnace is divided into preheating section, heating section and heating section along the length direction.

The lower temperature of the feed end is the preheating section, and its function is to utilize the heat of the furnace gas to improve the thermal efficiency of the furnace.

The heating section is the main heating section, and the furnace gas temperature is high to facilitate rapid heating.

The soaking section is located at the discharge end, and the difference between the temperature of the furnace gas and the temperature of the metal material is very small, so as to ensure that the temperature of the section of the burden billet is uniform.

Technique Data

1. Heat load of reheating furnace, the heat transfer capacity of each heating furnace to the medium in the unit time, which indicates the production capacity of the reheating furnace.
2. Furnace temperature. The commonname is the wall temperature, refers to the temperature when the flue gas moves away from the radiation chamber into the convection chamber. The higher the temperature, the greater the heat transfer of the radiant tube, and the greater the amount of heat entering the convection chamber. But if the temperature is too high, it is easy to burn the furnace tube and the intermediate pipe rack.
3. Furnace heat intensity. That is, the total calorific value of fuel combustion in the furnace per unit volume per unit time, W/m2. Ifthe furnace size is certain, burning more fuel will inevitably increase the heat intensity of the furnace, and the furnace temperature will increase correspondingly. The heat of the furnace tube in the furnace will also increase. Generally, the furnace heat intensity of the general tube furnace is 8.14~11.63W/m3 (7 ~10kcal/m3·h).
4. The heat of the furnace tube surface. The heat per unit area and the heat transferred per unit time are called the surface heat intensity of the furnace tubes. The higher the thermal intensity of the furnace tube surface is, the less the furnace tube will be required for a certain heat load. The furnace can be reduced and investment reduced, but there is a limit to the improvement.
5. Heat efficiency of the furnace. The percentage of the total heat released by the heating furnace when the fuel is burned is called the thermal efficiency of the furnace. The higher the thermal efficiency, the more saving of the fuel. It indicates whether the furnace is advanced.
6. The flow rate in the tube. The smaller the flow rate is, the smaller the heat transfer coefficient is, the longer the retention time in the furnace is, the more easy the medium is to focus in the tube, the more easily the tube is damaged, but the flow rate is too high and the pressure drop in the tube is increased and the power consumption is increased. Therefore, the flow velocity in the tube is suitable.

Working principle

The furnace used for heating small broken fabric billets is only preheating section and heating section.

It is customary to divide the furnace section according to the heating belt with the burner in the furnace. According to the number of tropics, the furnace is called the one section, the two section, and the five section and the six section. In the 50~60 years, due to the increasing capacity of the rolling mill, the length of the push steel furnace was not too long to be limited by the length of the push steel. Therefore, it began to increase the supply of the tropics at the feeding end and cancel the non heating preheating section to improve the productivity of the floor area of the unit. Using this furnace to heat the slab, the output per unit area of the furnace bottom reaches 900~1000 kg / M (2 m), and the heat consumption is about 0.5 ~ 0.65 x 106 thousand cal / ton. Since 70s, due to the need of energy saving and the increase of the length of the furnace by the new step furnace, the preheating section of non heating is added. The best unit area per unit area of the furnace is 600~650 kg / (2 m), and the heat consumption is about (0.3 ~ 0.5) x 106 thousand cards / tons.

Continuous furnaces usually use gas fuel, heavy oil or pulverized coal, and some uses lump coal. In order to use the waste heat effectively, a heat exchanger for preheating air and gas is installed in the flue or a waste heat boiler is installed.