Brief discussion on rotary kiln process management

Date: 2019-09-24 Views:

  China's current cement production capacity is seriously excessive, the market is unstable, regional coordination, environmental protection and other factors resulting in the single clinker production line as in the past annual turnover rate of more than 80% of the situation is difficult to appear.

  In the past, the era of increasing profits by continuous operation of kilns and increasing clinker and cement sales has passed. How to maintain profits with limited operation time and reduced output and sales has become a theme of the current cement industry.

  Our company for the actual production of specific problems to analyze, through the internal grasp, internal control to reduce energy consumption.

  1. Existing problems

  A certain company has a 5 000 t/d clinker production line put into operation in 2010. The following problems restrict the stability and comprehensive benefits of the kiln system.

  (1) the limestone resources in the mine are poor,         

         And the content of CaO in limestone is low and fluctuates greatly, with CaO content ranging from 30% to 51%, and MgO, R2O and other harmful components in limestone are high (see figure 1), which makes the raw material ingredients fluctuate greatly. The proportion of limestone is about 90% (see table 1), and the highest can reach 99%.

  The instability of raw material seriously restricts the stability of kiln system.

  (2) the environmental protection situation is severe,

        And the environmental protection cost of tons of clinker is relatively high. The average monthly environmental protection cost is shown in table 2.

  (3) high power consumption and coal consumption.

  In the first half of 2016, unit clinker physical coal consumption was 130.88kg /t, standard coal consumption was 104.89kg /t, and comprehensive electricity consumption was 49.7kwh /t.

  (4) low power generation.

  In the first half of 2016, the average power generated by waste heat generation is less than 7,400 kW(full load is 9,000 kW).

  2. Measures taken

  2.1 stable raw material ingredients

  In view of the poor limestone resources, the company sent special personnel to carefully compare and analyze the limestone of each ore point, and make a reasonable match according to the requirements from the quality and quantity (see figure 1).

  Send a special person to be responsible for the implementation of matching situation in the mine (grasp and monitor the proportion of vehicle feeding in each mine point), match the limestone proportion according to the limestone quality of different mine points (ensure that the CaO content in limestone is 44.5%~45.5%).

  The mixing results and limestone proportion were monitored and assessed to ensure that the limestone proportion fluctuated within 2%.

  At the same time for the raw material batching broken material increase assessment and adhere to clearance to ensure the stability of raw material.

  2.2 save environmental protection costs

  (1) excessive emission of sulfur dioxide is mainly caused by excessive sulfur introduced into the system by raw and combustible materials and low desulfurization efficiency of the system.

  To this end, the company on the one hand, with low sulphur, burning materials (see table 3), on the other hand, choose suitable desulfurizer from birth is expected to homogenize the library into four chute to hoist in mixed with the material of the valve, to solve the problem of high sulfur in preheater, through market research to mixed with carbide slag in the raw ingredients, desulfurization in the raw mill system.

  The above measures can ensure that SO2 emission is below 75 mg/m3.

  (2) nitrogen oxide production is mainly in the kiln, our company mainly USES ammonia water to denitrify.

  To control nox emission values conform to the requirements, on the one hand, a stable into four ingredients and improve the decomposition rate (95%), ensure the material is easy to burn in the stove, at the same time adjust head coal and with the wind, the kiln head the flame has plenty of strength and do not make temperature is too high, reduce the formation of nox (ensure furnace reducing atmosphere in micro);

  On the other hand, strictly control the outlet temperature of the decomposition furnace at (880±5)℃ to ensure the optimal temperature of denitrification reaction, and strengthen the quality inspection of ammonia water and the inspection of denitrification system.

  (3) in respect of dust control,

       on the premise of strengthening the inspection of compressed air and on-site equipment management to ensure the normal operation of the equipment, high-quality glass fiber coated filter bags are used in the dust collector of kiln head and kiln tail bag, which can reduce the pressure difference by more than 200 Pa after use, and ensure that the smoke emission is controlled below 10 mg/m3.

  2.3 control power consumption and coal consumption

  (1) strengthen the treatment of site sealing and plugging, organize professional personnel to spot check the treatment of site air leakage every day and record and archive, and form a closed loop management system → inspection → treatment → assessment.

  (2) stable raw material batching and reasonable control of raw material fineness.

  Through the reasonable matching of the mine at the source and the later batch management, a good foundation was laid for the stability of raw materials. When the fluorescent automatic batch system was introduced, the close relationship between the quality control department and the central control was strengthened, and the automatic batch system was timely corrected based on the change of working conditions. The qualified rate of raw materials per month could be above 95%.

  Combined with the kiln conditions, the burnability of raw materials was compared when the 0.2mm screen residue was 1.0%, 2.0%, 3.0% and 4.0%, respectively, and it was found that the burnability of raw materials was better when the 0.2mm screen residue was 1.0% and 2.0%, and the difference between f-cao was within 0.2%. Therefore, the burnability of raw materials was determined to be within 2.0%.

  (3) to optimize the system's use of air, conduct smoke analysis and comparison on the flue gas of the flue gas chamber, the decomposition furnace and the flue gas chimney of the flue gas analyzer, and make corresponding adjustments according to the current actual working conditions. In the case that the shrink port size of the flue gas chamber is 2.25 m×2.25 m, make fine adjustment on the opening of the three times air gate in a timely manner within the range of 65%~70%.

  It can be seen from figure 2 that the kiln skin is smooth and stable after fine adjustment.

  It can be seen from table 4 that under the condition of poor limestone resources, the quality of clinker from kiln is relatively stable by adopting the above control measures.

  (4) reasonably control the raw material output at the time of the raw material table. Through comparative analysis, it can be concluded that 400 t/h is the output at the time of the most economic table for the final grinding system of the raw material roller press. When the output at the time of the table is too high, the raw material power consumption is much higher than that at the time of the economic table.

  Of course, the specific value of economic production in addition to the equipment reason is also related to the grinding and brittleness coefficient of raw materials, so the raw material roll press system in economic production is an important measure to reduce the power consumption.

  2.4 increase waste heat generation

  (1) improve the operation quality and maintenance quality of waste heat power generation equipment.

  (2) adopt new high-efficiency vacuum pumping device to ensure the vacuum degree above 0.093mpa.

  (3) strengthen the cooling tower cooling efficiency, ensure the cooling tower temperature in the range of 25~30 ℃.

  (4) increase the air volume of grate cooler to improve the heat recovery while cooling the clinker.

  (5) strengthen the correlation analysis of clinker ingredients, clinker granulation and power generation, improve the specific heat of clinker, and adjust even granulation to ensure the hot air quality of waste heat power generation.

  2.5 balanced and stable production

  Give full play to the rotary kiln's potential high and stable yield, and find the optimal balance between the quality, output and indexes that are suitable for the working conditions of the kiln system. Through system optimization, our company can maintain the average daily output above 6 050 t/d in the effective operation time, laying a foundation for the completion of energy saving and consumption reduction indexes.

  3 the effect

  From July to December 2016, our company achieved the average standard coal consumption per unit of clinker 98.6kg /t, physical coal consumption 124.5kg /t, comprehensive power consumption of 47.8kwh /t, comprehensive environmental protection cost of 2.98 yuan /t, waste heat power generation power from August to December averaged over 8,800kw, basically reaching the rated power generation of 9 MW units.

  Energy saving, consumption reduction and comprehensive benefit improvement will be the subject of internal management and internal control in the company's production management for a period of time. In addition to certain achievements, our company will continue to exchange and study with peers in the industry to find and solve its own shortcomings and further improve the level of internal management and internal control.

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