Research On The Process And Equipment Of Reclaimed Sewage Treatment And Recycling Use Of Used Sodium Silicate Sands

The reclamation of foundry CO₂ sodium silicate sands has always been one of the difficult problems in the industry.Relevant reclaim research and application practice show that wet reclamation can achieve high-quality and low-cost used sands reclaiming,but the disadvantage was the production of recycled sewage.Aiming at the problem of sewage discharge caused by wet reclamation,this topic proposed a wet reclamation method of used sodium silicate sands for recycling use,which can achieve the goal of water recycling used and zero discharge of sewage.Based on this,carried out theoretical and experimental research,and entered the pilot test to obtained the technical parameters of wet reclamation and sewage treatment.The results of the small-scale test of the wet reclamation sewage treatment and recycling of used sodium silicate sands were analyzed,the treatment effects of different reagents on sewage were compared,and the technical scheme of treating sewage with lime milk was determined.The treatment experiments of old sodium silicate sands and sewage were carried out from three aspects,such as the removal and precipitation of harmful components in sewage and the strength of regenerated sands,and the feasibility of the technical scheme was analyzed.A pilot test platform was built based on the experimental results.Use the multiphase flow model of Ansys Fluent to simulate the process of quicklime digestion and lime milk treatment of sewage,and complete the selection of quicklime powder particle size,digestion and mixing speed,and axial stress check.Realize the rational selection of key equipment including quicklime digestion system and sewage treatment system,and set up a pilot production line for wet reclamation of used sodium silicate sands.According to the parameters optimized by experiment and simulation,six times of water cycle wet reclamation were carried out on the pilot production line.The pilot test showed that the used sands was sprayed and dehydrated after secondary hydraulic scrubbing to obtain reclaimed sands and sewage;the lime milk with the mass ratio of water and quicklime being 3/1 and stirring at 300 r/min,the lime milk treated sewage can effectively dehydrate the sewage.More than 80%of carbonate and more than 90%of silicate were converted into sodium hydroxide solution and calcium carbonate and calcium silicate were precipitated.During the six times water cycles,the average recycling rate of the reclaimed sands was 87%,and the average loss rate of the circulating water was about 2.5‰,achieving the goal of zero water discharge.The initial strength of the regenerated sands was 1.5MPa and the 24h strength was 1.6MPa,which was close to the strength of the new sands;the residual strength was 2.5MPa,and the collapsibility was slightly deteriorated.The reclaimed sands was used for modeling and casting,and the castings had no obvious casting defects,which proved that the reclaimed sands fully meets the requirements for use.During the circulation process,the concentration of sodium hydroxide was continuously increased,and hydraulic scrubbing could restore the activity of sodium silicate on the surface of the used sands to become colloid,and the viscosity of the sewage increased.It slowed down the accumulation of impurities in the reclaimed sands,ensured the stability of the initial strength and 24h strength of the reclaimed sands,and effectively alleviated the problem of deterioration of collapsibility.