Organization Design And Experiments Of Screw Separator

Livestock and poultry manure is the main source of agricultural non-point source pollution in China,and the annual output is about 3.8 billion tons,with a moisture content of 80% or more.The amount of manure is huge and they are flow shaped.If handled improperly,they will easily lead to environmental pollution and a great waste of resources.Therefore,deep processing and utilization of livestock and poultry manure could achieve the “waste to treasure” change of them.Solid-liquid separation is the first procedure of their processing and utilization.At present,there exists three kinds of technology for solid-liquid separation of manure,i.e.centrifugal,filter-type and sieving.When livestock and poultry manure has a high solid content and viscosity,theeffect of the traditional spiral extrusion separator is poor.To enhance the separation effect,large amounts of water will be added to dilutethe manure,which not only produce much sewage,but also increase the difficulty and cost of follow-up processing.Therefore,it is of great practical significance to study the solid-liquid separation technology of livestock and poultry manure for processing efficiency enhancement,filter cake moisture content reducing and viscous materials adaptability improvement of equipment.Based on the analysis of the mechanism of the screw extruder,the numerical simulation of the flow field in the spiral extrusion and dewatering flow channel was carried out by using the computational fluid dynamics(CFD),to probe the low of spiral extrusion Dewatering flow field and to provide the theoretical basis for structural parameter optimization and multi-factor experiment.This study analyzed the effects of intermittent distance,helix speed and slag pressure on the dehydration efficiency and the moisture content of the slag.The optimum operating parameters of the spiral extrusion and dewatering mechanism were obtained,and the performance test was carried out with the ordinary continuous screw extruder.It is concluded that the extruder has the better dehydration performance and reached the design expectation.The main research contents and research results are as follows:(1)Study on the physical characteristics of livestock and poultry waste.The physical properties of pig manure and cow dung were experimentally studied.According to the water content viscosity curve,the physical properties of pig manure and cow dung were similar,and there was a high correlation between solid content and viscosity.The lower the solid content,the smaller the viscosity,the relatively smaller the intermolecular polymerization force,which make the manure relatively easy to dehydrate;Otherwise,the manure relatively is difficult to dehydrate.(2)Design of screw extrusion and dewatering mechanism.In order to solve the problems existing in the existing spiral solid-liquid separator,the tooth-screw is divided into continuous and broken teeth.The former is arranged by two continuous blades.The latter consists of four spiral units,with each helix separated by two pieces of teeth arranged intertwined and adjacent spiral unit leaves two orthogonal.Each spiral blade has a sharp cutting function at the feed edge.Spiral Extrusion Dehydration Mechanism efficient for separation of high concentrations of fecal waste and it is uneasy to plug.(3)Broken tooth spiral flow field characteristic research.Using CFD,the flow field numerical simulation of small designed and large-panmodel was analyzed.The broken tooth spiral dewatering device performance,particle concentration distribution and particle velocity distribution in the runner and regional differential pressure distribution of porous media was compared and analyzed for three kinds of structure parameter models.The numerical simulation results also accurately speculated the flow characteristics of broken tooth spiral squeeze dewatering device.The variations of volume fraction changes in the runner were divided into three stages.The valume fraction increased with a wavy shape in general.The gap length plays a important role on the flow pattern inside the cavity.Discontinuous zone of particle movement has certain cushion.Length of the gap distance can control particle residence time in the cavity.Porous media areas inside and outside differential pressure has largest growth in the late of dehydration.The smaller the gap distance under the condition of same,the greater the pressure difference.By analysis of flow field characteristic in theory in this study,the high efficiency,low moisture content of extrudate and strong adaptability of the broken tooth spiral separation were theoretically introduced.According to simulation and real practices,the reasonable range of broken teeth distance in 20 mm to 50 mm,which provides reference for further optimization study.(4)Operation parameters optimization test.To reduce the design cycle,virtual modeling was conducted with the 3d design software Creo2.0 test device,and the test bench was designed,the Box-Benhnken center combination experimental design method,the working parameters of broken teeth screw extrusion mechanism optimization test.Selection of screw speed,intermittent distance,counterweight position to influence factors of moisture content on separation efficiency and extrudate as objective function,determines the influence factors of primary and secondary relations as well as significant,and established the influence factor and multiple mathematical regression model between the objective function.Through experiments and combined with production practice,finally to work out the best parameters combination for: 37 mm gap distance,speed and 56 r/min,the counterweight position at 309 mm,the separation efficiency and extrudate moisture content after 5.43 m/h,53.52% respectively.By the broken teeth screw and continuous spiral contrast test shows that the performance of both under the same conditions,broken teeth screw a continuous spiral discharging speed,uniformity of material concentration and strong adaptability,low moisture content of extrudate.