What is the thermal system of the hot galvanizing preheating furnace?
For ease of control, the preheating furnace should be designed with three control degrees.Different kinds of steel have different recrystallization temperature, and the higher recrystallization temperature is, the higher the strip temperature of preheating furnace should be.According to the experience, the combustion gas intake, heat consumption and unit productivity are closely related to the temperature of the strip.It has been proved that when recrystallization temperature is high, the unit productivity will decrease, and the heat consumption and combustion gas intake will increase accordingly.
It can be seen that the preheating furnace mainly controls the furnace temperature in the production process to meet the demand of certain strip temperature.In order to control the temperature of strip steel accurately, the intake quantity of combustion gas must be selected.
About the intake quantity of combustion gas in preheating furnace,
The following formula can be calculated:
V = WCs (Ti)/hr x1000
Where: Vs- amount of combustion gas to be connected to preheating furnace (NM/h)
W-1 productivity (T/h)
Specific heat of cs-1 steel (0.13 kcal /kg. Degree)
T, a preheating furnace of strip temperature (℃)
A combustion gas calorific value 12 h at room temperature (℃)
Thermal efficiency of furnace n (%)
How to control the combustion atmosphere of preheating furnace?Why is it important?
In the modified sensemir hot-dip galvanizing preheating furnace, there is no oxidation heating furnace.In this way, the combustion in the furnace is required to be an incomplete combustion without oxygen, and the waste gas composition is CO2,H0,CO,H, CHI, N2, etc., which is theoretically a reducing atmosphere.However, because of H0 content in exhaust gas is often high, its dew point often can be up to + 20 ℃, so steel plate heat in the atmosphere, in fact, there has been a slight oxidation.Only when <0.6 can a reducing atmosphere be obtained.Reasonable control of combustion atmosphere of preheating furnace:
(1) improve furnace temperature, can reduce furnace oxidizing atmosphere so the preheating furnace temperature up to 1100 ~ 1300 ℃.
(2) combined with fe-fe0 equilibrium curve, the partial pressure of CO2, CO,H0 and H in waste gas was measured, and the ratio of Prz/Pr and Poo/Po was calculated. The input value was selected from fe-fe0 equilibrium curve.In actual production, the reduction zone of fe-fe0 balance curve is not necessarily emphasized, because the weak oxidizing atmosphere in the preheating furnace is enough to reduce in the reduction furnace.