Cement has become the most important building material in various construction projects because of its excellent engineering performance and relatively low production cost. But in the process of cement manufacturing, there is a problem that can’t be ignored, that is, the serious consumption of natural resources and energy and the emission of greenhouse gases. Therefore, with the rapid development of the economy, the cement industry is bound to be impacted by the shortage of non-renewable resources and energy and the pressure of environmental protection. What measures should the cement industry take to significantly improve the utilization rate of energy and gradually become the focus of recycling economy industry?
|Cement Production Line||Rotary Kiln Size (m)||Design Capacity (t/d)||Actual Capacity (t/d)||Material Consumption||Heat Loss (kJ/kg)||Heat Efficiency (%)||Heat Efficiency Of Cooler (%)||Cooling Air Volume (m3/kg)||Output (kg/m3)|
|Wet process cement production line||φ4.0/3.5×145||816||878.4||1.651||5191||34.2||64.29||2.85||27.77|
|New dry process cement production line1||φ4.0×60||2500||2814.2||1.628||3076||57.58||71.94||1.99||200.82|
|New dry process cement production line 2||φ4.3×60||3200||3768.2||1.622||3185||54.16||71.27||1.82||230.86|
|New dry process cement production line 3||φ5.2×70||6000||6889.9||1.595||2856||57.92||63.1||1.84||230.48|
Clinker calcination is the most important stage in the cement making process, and it is also a stage with high energy consumption and large gas emission. To produce one ton of cement clinker, it needs to consume 1.58 to 1.621 tons of raw materials, 0.10-0.12 tons of coal, and emit about 1 ton of carbon dioxide. Therefore, the energy saving and consumption reduction in the clinker calcination process is crucial for the whole cement production line. The above is the thermal performance test data of clinker production lines with different production processes and production scales. Through analysis, we can summarize the following methods to help us achieve energy conservation and consumption reduction in the cement making process.
Replace the Traditional Cement Equipment
The comparison data between the wet process cement production line and the new dry process cement production line shows that with the same rotary kiln size (diameter), the production capacity of the cement kiln which adopts the pre-decomposition production process increases more than 200%, the output rises from 27.77kg /m3 to 200.82kg /m3, and the unit heat consumption reduces 40%. In addition, the thermal efficiency of the calcination system increased from 34.20% to 57.58%. The reason why these data have changed greatly includes:
- In the dry method cement production process, the water content of raw materials is less than 1% so the heat consumption required to evaporate the water is greatly reduced.
- The mode of heat transfer has changed. In traditional wet method cement kilns and dry method cement kilns, the materials preheating and decomposition process is carried out under a stacking state, while in the new cement pre-decomposition kiln system, this process is carried out under a suspension state. Studies have shown that materials in suspension can be fully in contact with the hot gas flow, and its heat transfer area is a thousand times greater than that in the rotary kiln. It accelerates the heat transfer rate so that the preheating and partial decomposition process that originally required for 1 hour can be completed within 30s. Even after a further heat transfer in calciner, the decomposition rate of materials can reach more than 90% within 60s.
- In the cement pre-decomposition system, the material particles are all in a suspension state. So there is a lack of close contact between particles, which makes it difficult for CaO to produce solid-state reaction with other minerals. After these high-temperature raw materials entering the cement rotary kiln, they will be in a state of accumulation, and the mineral particles will be in close contact with each other so that the solid-state reaction can take place at many points and proceed rapidly, thus forming a relatively concentrated solid-phase reaction zone. The exothermic phenomena produced by these reactions are beneficial to the heating and sintering of materials.
Large Scale Main Cement Equipment & Matching Auxiliary Equipment
According to the data in the table, we can find that the production capacity of the new dry process cement production line increases significantly with the enlargement of the rotary kiln size. When the size of rotary kiln is increased from 4.0m to 5.2m, its capacity has more than doubled and the unit heat consumption is reduced from 3100 kJ / kg to 2850 kJ / kg, while the output and system thermal efficiency are relatively stable. The reason for the high heat consumption of new dry process cement production line 3 is that after the actual capacity is increased by more than 17% compared with the designed capacity, the surface temperature of the calcination system is on the high side, but the capacity of the clinker cooler is not matched, which leads to a high temperature of clinker. This shows that the production capacity of the auxiliary equipment must be matched with the main cement equipment, which can not only increase the output but also ensure the minimum energy consumption.
AGICO is a professional EPC cement plant manufacturer in China. We offer cement projects with various capacities and production purposes, such as large scale cement production lines, mini cement plants, cement grinding units, stone crushing plants, etc. We apply the advanced pre-decomposition technique in our dry method cement production lines, which reduces the energy consumption in the cement making process.