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Pretreatment process of decanting wastewater by decanter centrifuge

May 27, 2019

Chlorine reacts directly with water to form hypochlorous acid, which reacts continuously and uniformly in the reactor to form dichloropropanol (DCH). These include 1,3-DCH (34%) and 2,3-DCH (66%).


The dichloropropanol and calcium hydroxide aqueous solution undergo a cyclization reaction to form epichlorohydrin. The conversion rate of the reaction is as high as 98%. In comparison, the conversion rate of 1,3-DCH is faster than that of 2,3-DCH. In general, increasing the concentration of temperature and alkali and decreasing the concentration of DCH can increase the conversion rate. Since the production process uses lime milk as a raw material, the industrial wastewater produced by the reaction contains a large amount of CaC12, Ca(OH)2 and the like.


Industrial wastewater water volume, 162 m3/h; pH value >11; COD value, 2 200~2 400 mg/L; suspended solids, 5,000-8 000 rag/L; Ca value, 1O 400-12 024 mg/L.


The separation process of the centrifuge includes the following stages.

(1) Mixing and acceleration stages. The slag-containing wastewater and the flocculant are mixed and accelerated in the feed chamber to ensure that the slag-containing wastewater enters the separation zone in an optimal state.

(2) The clarification phase. Under the action of centrifugal force, the flocculated particles are quickly separated and settled in the straight section of the drum. The separated supernatant is discharged through a mouth provided at the end of the drum.

(3) Compression phase. The auger pushes the settled solids to the discharge end, and the sludge is further compressed by the centrifugal force and releases the pore water.

(4) Two-way extrusion stage. In the conical section of the drum, the waste cement slag is subjected to biaxial compression, and the auger is appropriately designed to generate a pressing force in the axial direction. The capillary water is further extruded by the compression of the centrifuge.

(5) Control the solid residence time. When the amount of sludge entering the centrifuge and the mud quality change, in order to maintain the optimal dewatering effect at all times, the total amount of solids in the drum of the centrifuge is continuously controlled.

Due to the large amount of water in the circulated wastewater, the solid content is low, the initial conditions can not meet the processing requirements of the horizontal screw machine. In order to improve the working efficiency of the horizontal screw machine, the mechanical sedimentation is considered in the transformation process, and polyester amide is used as the flocculant. Increase the solid content of the wastewater and then enter the horizontal screw machine for treatment. Transform the technical process.


The SS value of the effluent suspension in the propylene oxide saponification wastewater pretreatment unit is up to 8 960 mg/L on average, while the SS value of the effluent suspension in the cyclization wastewater pretreatment unit is 356 mg/L on average. The SS value of suspended solids in the cyclization wastewater pretreatment unit averaged 4 477 mg/L, and the SS value of the effluent suspended solids averaged 284 mg/L.


The horizontal spiral discharge centrifuge has a good effect, and the moisture content of the sludge is about 70%. The original neutralization device of the device, because the pH monitoring electrode can not meet the existing process parameters, the failure rate is high; at the same time, the carbon steel pipe currently used as the sewage pipe of the system, once the pH adjustment is unstable, it is easy to cause system corrosion, repair The rate is high, so the neutralization system is deactivated.