When the furnace is designed, the highest temperature range of the furnace is the actual combustion temperature, and the temperature of the preheating section and the soaking section are lower than the actual combustion temperature.
Carbon dioxide and water vapor are thermally decomposed at high temperatures, complicating the calculation of the theoretical combustion temperature. However, when the temperature does not exceed 100 ° C and air is used as the combustion improver, the influence of thermal decomposition can be neglected. The calculation formula of the theoretical combustion temperature can be simplified as:
When calculating the theoretical combustion temperature in the project, the approximate calculation is carried out by the graphic method. After determining i cp , according to the percentage of excess air in the combustion products. The actual combustion temperature can be determined by finding the value of t th from the figure below. If the calculated actual combustion temperature is higher than the required temperature in the furnace working space, the fuel and combustion conditions can meet the temperature requirements of the production. Otherwise, it is necessary to change the fuel type or change the combustion conditions (lower the air consumption coefficient or increase the preheating temperature). Meet the temperature requirements in production.
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(2) Air consumption coefficient and smoke atmosphere
The air consumption coefficient n is the ratio of the actual air demand Ln to the theoretical air demand amount Lo when the fuel is burned.
During the roasting process of mineral raw materials, the air consumption coefficient (or excess air coefficient) has a great influence on the thermal work of the roaster and the atmosphere in the furnace. The air consumption and the volume of combustion products increase in proportion to the air consumption coefficient. The content of carbon dioxide, water vapor and carbon monoxide in the flue gas decreases as the air consumption coefficient increases. Therefore, under the premise of ensuring maximum complete combustion of the fuel, the smaller the value of n, the smaller the oxidation of the flue gas and the greater the reduction. Undoubtedly, the choice of n value is related to the fuel type and the thermal requirements of the roasting process.
The calculation of the value of n can be performed by an oxygen balance method or a nitrogen balance method. The calculation formula of the oxygen balance method is:
Wherein O' 2 H 2 O'--the percentage of oxygen and water vapor in the flue gas;
RO' 2 - the sum of the volumes of carbon oxide and sulfur dioxide in the flue gas,
a, b———The oxygen demand of 1 m 3 RO 2 and H 2 O is generated.
Where K—the ratio of the theoretical oxygen demand in the combustion of the unit fuel to the RO and volume in the combustion product.
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