This report is from Yangquan Jidong Cement Co., Ltd: Abstract: By changing the air inlet of the three air ducts, eliminating the original ammonia lance and adding four sets of lances in the rising flue of C5A and C5B, as well as adding denitrification automatic control system and other technical improvement measures, the NOx emission was reduced from 400 mg/Nm3 before the technical improvement to 230 mg/Nm3, and the ammonia consumption was reduced from the original 2.1 m3/h to 0.4 m3/h, the denitrification efficiency has been significantly improved, and good economic benefits have been achieved, meeting the requirements of the special emission limits.

As enterprises pay more attention to environmental protection, cement rotary kiln nitrogen oxide emissions as the key control indicators, enterprises continue to increase investment in environmental protection. Yangquan City, as a transmission channel of Beijing-Tianjin-Hebei air pollution in "2+26" city circle, has reduced the NOx emission limit from 400 mg/Nm3 to 320 mg/Nm3 in accordance with the special emission limit. 5000 t/d production line of our company, rotary kiln specification Φ4.8 m×72 m, decomposition furnace Φ8.0 m spouting duct type. The SNCR denitrification system originally used, because of the unreasonable position and arrangement of the lance and inappropriate equipment selection, the ammonia (concentration 25%) dosage is high, the average value is 2.1 m3/h. The system automation control is not high, and the ammonia flow is adjusted manually, resulting in high ammonia cost as a percentage of clinker production cost. In response, the company organized technicians to renovate the ammonia denitrification system during the furnace maintenance at the beginning of the year, and achieved satisfactory results.

1 Technical modification of the air inlet method of the three air ducts

In order to make the low oxygen reduction zone have sufficient reaction space, the three air sub-pipe into the decomposition furnace at the optimization process, the original three air pipe center into the approximate tangential entry, see Figure 1.

2 ammonia lance technical reform

The current decomposition furnace five layers of lances canceled, in C5A, C5B of the rising flue to add four sets of lances each, the location selected in the upper 1.5 m of the top cover, lances cross-arranged to improve the effective coverage of ammonia spraying area and atomization effect. Ammonia and atomization of the compressed air required, are drawn from the original denitrification system control cabinet, the control system remains unchanged. See Figure 2 for the technical modification of ammonia spray gun.

3 Increase denitrification automatic control system

During the collaborative kiln shutdown, an automatic control system was added to the ammonia denitrification system to set the target value of NOx emission from the kiln tail flue tube, and the frequency of ammonia pump was increased and decreased according to the NOx value in time to achieve precise control.

4 Effect of technical improvement

After one and a half months of operation, the actual data show that the retrofitting effect is remarkable. The NOx emission is reduced from 400 mg/Nm3 before the renovation to 230 mg/Nm3, and the ammonia consumption is reduced from 2.1 m3/h before the renovation to 0.4 m3/h. The denitrification efficiency is obviously improved and is only one-fifth of the consumption before the renovation. According to the consumption of ammonia compared with that before the transformation, it can save the company about 2 million RMB per year according to the calculation of 7 months kiln opening time.