Shaanxi Jiate Technology Paper Co., Ltd. No. 2 paper machine produces coated white paperboard, the amount of fresh water is less than 20t / t paper, reaching the domestic advanced level. This article introduced its white water treatment process and technical equipment, and analyzed its economic and technical indicators.

Air floatation process

1.1 Equipment and Parameters

Two Φ18m*0.8m shallow air flotation units were used to treat 15,000 m3/d of white water. Three ANDRITZ belt filter presses were used to dewater the dross. The belt width of the filter press was 2 m. Each filter press was processed. The capacity is 200 m3/d; SS<100 mg/L after treatment, dross dryness>1.5%.

1.2 Process flow

The white water of the paper machine is first treated with a diagonal net, and the long fibers that have been filtered are recovered and reused, and the net water enters the white water tank of the air floating system. The white water in the white water pond is pumped into the shallow air flotation tank. After the white water stays in the air flotation tank for 2-3 min, the clear water flows from the center of the round pond to the clarification pond, and about 30% of the clear water circulates into the dissolved air pipe. The compressed air in the tank also enters the dissolved air pipe. In the dissolved air pipe, due to the action of the release head, tiny air bubbles are dissolved in the refluxing clear water to form dissolved air water and enter the air floatation tank. Before the scum pressure filtration, it is necessary to dewater after gravity concentration, the dewatered scum quality fraction is 7%-9%, and the sludge dryness after the dewatering by the filter press can reach more than 25%.

2 operation effect

Since the system was put into operation in 2002, it has been operating stably and reliably, and the white water treatment effect has fully met the design requirements. Most of the clarified water after treatment is recycled to the waste paper deinking line. After treatment, clarified water SS≤86mg/L, CODCr≤530 mg/L, BOD5≤120mg/L, SS removal rate reached 96%. The white water treatment equipment has a small investment, stable operation, small floor space and low cost, and is the best choice for sewage treatment equipment of small and medium-sized paper-making enterprises.