Papermaking equipment-wastewater treatment method

　　The paper industry is an industry that consumes a lot of water and has serious pollution. Due to the high concentration of pollutants in paper-making wastewater and the difficulty of treatment, all countries have listed paper-making wastewater as one of the major public hazards, and Japan is listed as one of the five major public hazards. According to statistics from the United Nations Environmental Planning Group, the world’s papermaking industry discharges 27.4 billion tons of wastewater per year, the total amount of pollutants in papermaking wastewater is BOD 10.8 million tons, total suspended solids is 5.94 million tons, and sulfides are 1 million tons.

　　my country's paper industry has the following characteristics: First, the proportion of small and medium-sized enterprises with an annual output of less than 10,000 tons is about 82%; second, my country's papermaking is mainly made of straw pulp. Wood pulp papermaking accounts for about 14% of total production, non-wood pulp accounts for about 86%, and about 60% of non-wood pulp production is straw paper. Straw pulp papermaking makes the concentration of pollutants in my country's papermaking industry higher than that of foreign papermaking industries.

　　Paper industry wastewater is divided into three types: black liquor, intermediate water and white water. Black liquor: comes from cooking waste liquor, producing 1t pulp about 10t black liquor. The concentration of pollutants in black liquor is related to the types of papermaking raw materials used and the internal production process. Generally, impurities in black liquor account for about 10-20%, of which 1/3 are inorganic substances, mainly various sodium salts; 2/3 are organic substances, mainly alkaline lignin, hemicellulose, fatty acids and resin acids. The middle-stage water comes from the washing, screening and bleaching sections of the papermaking process. The indicators of the middle section water: COD=800～2000mg/L, BOD=200～500 mg/L, lignin=50～200 mg/L, PH=7～8, this kind of wastewater has a higher color, and the water contains difficult organisms Degradable substances. The white water comes from the paper machine and the beating machine in the papermaking process. The concentration of white water pollutants is low, and the BOD is usually only tens of mg/L.

　　In recent years, the industry of using waste paper to regenerate pulp has developed rapidly, but in the process of waste paper recycling, deinking wastewater will be generated, and its water quality is characterized by high ink and short fiber content.　　 For small and medium-sized paper mills, it is difficult to recover alkali from black liquor. Some small and medium-sized pulp mills use acid precipitation to recover lignin, turning waste into treasure. After extracting lignin from black liquor, coagulation and biochemical treatment are used to achieve discharge standards.

　　China's treatment technology for middle-stage wastewater has been improved through research and practical applications, such as: coagulation air flotation-biochemical treatment process, anaerobic fluidized bed-aerobic treatment process, stabilization pond treatment process, hydrolytic acidification-SBR treatment process. It has been widely used and achieved good treatment results.

　　Because of the low concentration of pollutants in white water, the focus of treatment is to realize water reuse. The usual processes used are air flotation-filtration or membrane treatment.

　　The papermaking deinking wastewater treatment process is based on the need for thick lines of waste paper for the pulping process. The main pollutants of waste paper pulping wastewater are ink, porcelain clay, and short fibers. The two-stage air flotation-filtration process has been used in experiments and has been successful. After treatment, it can be used in the production process and achieved good environmental and economic benefits. .

　　The process flow mainly includes the following methods:

　　(1) Deinking wastewater: wastewater → conditioning tank → mixed reaction tank → primary air flotation → mixed reaction tank → secondary air flotation → valveless filter → discharge standards

　　(2) White water wastewater: white water → collection tank → air flotation tank → clear back tank → to production slurry tank

　　(3) Papermaking black liquor: black liquor → silicon removal reaction tank → coagulation reaction tank → mixed liquid separation equipment → clear liquid tank → discharged into the middle water treatment station

　　(4) Middle-stage wastewater: sewage → grit tank → primary sedimentation tank → oxidation tank (adding chemicals) → oxidation tank → secondary sedimentation tank → effluent　　1. Paper industry: The appreciation of RMB will reduce the production cost of enterprises in the industry. If only the impact of RMB appreciation on the cost of raw materials is considered, the cost of product sales in China’s paper industry in 2004 was 171.591 billion yuan, of which the foreign exchange for imported raw materials was nearly 5.3 billion US dollars, equivalent to 43.8 billion yuan. A 2% appreciation of the renminbi can reduce costs. 0.51%, gross profit margin increased by 3.01%, total profit increased by 8.79%.

　　2. Pulp and waste paper: my country is an important net importer of pulp and waste paper in the world. By 2003, paper and paper products had become my country's third largest foreign exchange commodity after petroleum and steel. The appreciation of the renminbi will make it cheaper for domestic paper companies to import important raw materials such as pulp and waste paper, which will help companies reduce costs.

　　3. Stock market: Renminbi's entry into a real appreciation cycle will become an important positive factor driving the long-term trend of China's stock market. In the short term, it will affect investors' revaluation of companies in industries that are sensitive to exchange rate changes. The paper industry and other industries with a high proportion of imports, large external debts, high liquidity or huge RMB assets have been encouraged by long-term positives and have been sought after by investors and have seen a surge.

　　3. Exported paper: Due to the small export volume of my country's paper and paperboard, my country's paper and paperboard export volume was 1.25 million tons in 2004, accounting for only 2.5% of the output. Therefore, the appreciation of RMB has limited impact on paper and paperboard exports.

　　4. Imported paper: The appreciation of the renminbi this time is small, and the price of imported paper is generally more than 10% higher than that of domestic paper. At the same time, coated paper, newsprint and cardboard paper are currently in the anti-dumping period, so the appreciation of the renminbi will not lead to imports. Paper flooded in.