This article is the second part of the previous article. The application effect shows that China silica brick is both economical and environmentally friendly.
Improve the heat transfer efficiency in the coke oven combustion process. The temperature of the vertical fire channel of the combustion chamber is 1300 °C, the central temperature of the coke cake at the time of coke pushing is 1050 °C, the thickness of the 7-meter coke oven wall is 95mm, and the thermal conductivity of the traditional China silica brick is 1.9W·m·k-1. The thermal conductivity of the thermal China silica brick is 2.4W·m·k-1 as the condition, and the heat flow per unit area of the furnace wall under the two China silica bricks is calculated. According to the calculation, under certain conditions of the furnace wall structure, the thermal conductivity of China silica brick is the “bottleneck” of heat transfer in the process of heat transfer from the combustion chamber flame to the furnace wall of the carbonization chamber, and the size of the heat transfer coefficient determines the final heat flow. Since the heat flow per unit time is improved, the heat transfer efficiency is improved, and the heat utilization rate is also improved, and the heat released by the combustion of a unit volume of gas can be transferred to the carbonization chamber more effectively.
The research shows that the dehydration time of the coke cake center of the high thermal conductivity China silica brick coke oven is about 10 hours, the traditional China silica brick coke oven is about 12 hours, and the dehydration time of the high thermal conductivity China silica brick coke oven is 2 hours shorter than that of the traditional coke oven; The heating rate of the high thermal conductivity China silica brick coke oven coke cake center temperature is higher than that of the traditional China silica brick coke oven coke cake center temperature heating rate, indicating that the heat transfer rate of the high thermal conductivity China silica brick is faster than that of the traditional China silica brick, and the thermal conductivity has advantages. Table 2 shows the comparison of Baosteel Phase I and Phase IV coke ovens under similar conditions of carbonization time, coal content, coal loading and heating methods.
Under the same working conditions, the coking heat consumption (7% water content) of the coke oven of the first stage using high thermal conductivity China silica bricks is similar to that of the fourth stage coke oven using traditional China silica bricks, but the direct running temperature of the coke oven with high thermal conductivity China silica bricks is similar. Compared with the traditional coke oven, the straight running temperature is 11℃ higher, and the fire fall time is shortened by 0.4 hours compared with the traditional coke oven. The high thermal conductivity China silica brick coke oven has a large cooling space; The furnace temperature is the same, and the heat consumption (7% water content) can be reduced by 7%. Calculated according to the coking time of 22 hours and the annual production time of 8760 hours, the high thermal conductivity China silica brick coke oven with 50 holes × 4 can save 124 million cubic meters of mixed gas per year compared with the traditional China silica brick coke oven, equivalent to 20682 tons of standard coal, and the energy saving effect is remarkable. .
Reduces NOx emissions during combustion. Relevant studies have shown that there are three types of formation mechanisms of nitrogen oxides during coke oven combustion: temperature thermal NO, fast hydrocarbon fuel NO, and N-containing fuel NO. The first two are collectively referred to as temperature NO. The NO generated in the coke oven combustion process is mainly of temperature thermal type. When heated with coke oven gas containing N components, the amount of NO generated will not exceed 5% at most. Thermodynamic NO.
The concentration of nitrogen oxides in coke oven exhaust gas is related to the temperature of the fire channel of the coke oven combustion chamber (actually related to the combustion temperature of the fuel). When the temperature of the fire tunnel is 1200℃～1250℃, the concentration of nitrogen oxides in the coke oven exhaust gas is not obvious, and when the temperature is higher than 1300℃, the NOx increases obviously. When the temperature of the fire channel rises from 1300°C to 1350°C, the temperature is ±10°C, and the NOx calculated as NO2 is ±30mg/m3. Therefore, under the condition that the temperature in the carbonization chamber remains unchanged, the flame temperature in the combustion chamber built with high thermal conductivity China silica bricks can be lower; reducing the temperature of the fire path is beneficial to reducing the NOx concentration. Table 3 shows the relationship between the temperature of the vertical fire channel of the high thermal conductivity China silica brick coke oven and the concentration of NOx in the flue gas.
Under the condition of the same coking time, it is beneficial to reduce the NOx emission by appropriately reducing the combustion chamber fire channel temperature. Comparing the nitrogen oxide emission concentrations of high thermal conductivity China silica brick coke ovens and traditional coke ovens under different operating rates, it can be seen that as the operating rate increases, the NOx emission concentrations of high thermal conductivity China silica brick coke ovens and traditional coke ovens also increase; Under the high thermal conductivity, the NOx emission of the high thermal conductivity China silica brick coke oven is lower than that of the traditional China silica brick coke oven. According to the calculation of 7 kg of oxides per ton of standard coal burned, a high thermal conductivity China silica brick coke oven with an annual output of 2.47 million tons of coke can reduce nitrogen oxide emissions by 430 tons per year compared with traditional China silica brick coke ovens. The effect is remarkable.
In summary, high thermal conductivity China silica bricks all inherit the advantages of traditional coke oven China silica bricks, and further highlight the characteristics of high thermal conductivity on this basis. The use of high thermal conductivity China silica bricks reduces the fuel consumption of coke ovens, reduces the emission of pollutants such as NOx, and has considerable economic and social benefits. It is a new technical direction for the use of refractory materials in coke ovens in the future.
