01 Existing problems
A company 5000t/d clinker production line, put into production in March 2008, the production is relatively stable. Since production, we have used NC-15 type three-channel burner, four-channel burner and otong burner, and the best comprehensive use effect is NC-15 type three-channel burner. The burner has the advantages of simple structure, easy adjustment, powerful flame combustion and good adaptability to material, because the primary air volume is slightly larger and the coal consumption is slightly higher.
On September 13, a new NJ-15 type four-channel burner was replaced when the kiln was stopped and fixed. The end structure of the burner is arranged from the outside to the inside in order of axial air, coal air, rotary air and central air duct. The axial air duct adopts 40 circular nozzles with uniform distribution, the cyclone is a 39° cyclone, and the center air duct is a orifice plate small mouth. After ignition and feeding, the kiln condition is normal, and the secondary air temperature is lower at about 1050 ~ 1120℃. Sand flying material is much, granulation is fine, clinker appearance is not beautiful, material composition control is low, the condition drops obviously when the composition is high, the production at the stage is lower than 20t/h; MGO content is always on the high side, about 4.8%, and the secondary kiln skin is easy to grow at 40-45m of the kiln tail.
2.1 Adjustment measures taken in the process
(1) Increase the combustion intensity of the burner, increase the internal wind from 80% to 100%, and close the central wind from 50% to 10%.
(2) on the ingredients to improve the burning of raw materials, KH and SM partial lower limit control, due to the high content of MGO, appropriate to reduce the content of FE ₂O ₂, improve the content of AI₂O, IM control between 1.55 ~ 1.65, and strengthen the clinker in the control of MGO, will clinker in the MGO reduced to 4.8% below.
(3) In order to prevent the position of the trolley of the coal injection pipe from +200 to -200 at the tail of the long auxiliary kiln, the coal injection pipe should move once every 3 hours.
(4) To strengthen the cleaning of the constriction of the smoke chamber to prevent the large amount of crust in the kiln tail system caused by the low temperature in the front of the kiln and the high temperature at the end of the kiln, which will affect the ventilation in the kiln.
(5) Adjust the proportion of air used in the kiln, raise the three-time air valve by 10cm, properly reduce the ventilation in the kiln, and prevent the phenomenon of burning after the low temperature in front of the kiln.
(6) Strengthen the operation control of grate cooler material thickness, reduce the fluctuation range of secondary air temperature, and control the lower grate pressure within 7500 ~ 7800Pa.
(7) Strengthen the quality control of pulverized coal into the kiln. The quality of the coal used in this stage is good. The ash content of pulverized coal into the kiln is 15%-18%, the volatile content is 27%-29%, and the fineness of pulverized coal out of grinding is controlled below 10%.
Through the above adjustment of air coal material and operation, the kiln condition has improved but not reached the expected normal working condition. The system’s adaptability to incoming material is still not good. When the composition is slightly higher, the kiln condition drops, and the fluctuation of secondary air temperature is large. Judging from the adjusted situation, the air coal material and operation factors are not the main reasons for the decline of working conditions.
2.2 Adjustment of coal pipe cyclone
After the above analysis and treatment, the root cause of the problem is finally focused on the newly replaced burner. The swirl Angle of the burner is 3° larger than the previous one, which is increased from 36° to 39°. Theoretically, the swirl effect should be stronger and the combustion condition will be better. On analysis was found, the original NC three-channel and four-channel coal burner is the most fundamental difference between handedness has changed, the original three-channel spiral NC – 15 hydrocyclone to rotary and rotary kiln to buck, use effect is good, but the NJ – 15 of four-channel hydrocyclone rotate to the same as the rotary steering, combined with the use of the original three-channel, cyclone spin to arrest by opposite rotary kiln instead, cyclone other structure parameters constant, observe its effect.
The kiln condition has been significantly improved after replacement, and the chemical composition of kiln clinker is shown in Table 1. The secondary air temperature was increased by more than 50℃, reaching more than 1170℃ on average. The clinker granulator was uniform, which greatly reduced the occurrence of flying sand and fine powder. The clinker Kh was controlled in the range of 0.91 ~ 0.92, Sm in the range of 2.85 ~ 3.05, the yield was increased to 400t/h, and the quality was qualified. The changes of main operating parameters are shown in Table 2. Generally speaking, the consequent easier to provide higher temperature, but the adjustment effect shows that the plant coal injection pipe cyclone with rotary kiln consequent than the reverse, whether because of the raw materials of harmful ingredients or amount of liquid, the liquid viscosity causes such as liquidity is a bit slow in the stove, the flame of the pressure is low, making it easier for the flame under the same exhaust backward outspread, scatters upward flame length, and the reverse than downstream flame advance ability is a bit weak, made another kind of balance, to achieve an optimal state.
Table 1 Full analysis of kiln clinker before and after replacing cyclone
For most enterprises, there is no hard and fast requirement for the direction of the coal jet cyclone, so it is not considered in the analysis of the problem, but it has a great influence on the actual production. In the actual operation, the appropriate direction of the jet cyclone should be determined according to the specific situation, so that the system can run the best.