Study On The Uniformity Of Extruder Die Discharge And Optimization Of Feed Processing Parameters

Aquatic feed production needs to be extruded,which can make the feed more easily digested and absorbed by animals.The processing uniformity of feed is relatively low,resulting in a coarser particle appearance and lower pore uniformity.Appropriate die structure can improve the uniformity of the flow,improving feed quality,including appearance,water resistance,and so on.This research contains the following contents:The influence of the number of die openings(12,13,14,15 and 16)on the discharge uniformity of the H66 extruder die(discharge velocity,mass flow and viscosity)was studied by CFD simulation using Ansys Fluent.When hole number was 12,the velocity and mass flow were the highest,0.75 m/s and 1.75e-04 kg/s,and the viscosity was the lowest,72.5 Pa·s;When hole number was 16,the viscosity was the highest,85 Pa·s,and the speed and mass flow were the lowest,0.55 m/s and 1.25e-04 kg/s,respectively.It was concluded that when production capacity at 300 kg/h and the opening area per ton of the die at 330 mm2·h/t,die number at 14 has the optimal uniformity of the material flow.the variance of the discharge speed,mass flow and viscosity was the lowest.The influence of the length-diameter(L/D)ratio(1.25,1.5,1.75,2.0 and 2.25)of the die land on the uniformity of the material flow in the extruder was studied.Results show that when the die L/D ratio was 2.25,the speed and mass flow were the highest,0.6304 m/s and 1.4809e-04 kg/s,and the viscosity was the lowest,at 78.85 Pa·s;When the die L/D ratio was 1.25,the viscosity was the highest,79.87 Pa·s,the speed and mass flow were the lowest,0.6304 m/s and 1.3046e-04 kg/s.When the die L/D ratio was 1.5,the variance of the speed,mass flow and viscosity was the lowest and the uniformity of the die was the optimal.The unit weight,starch gelatinization,oil absorption,water absorption,water solubility and water stability of feed were studied under different screw speeds(266 rpm,300 rpm,350 rpm,400 rpm and 434 rpm),moisture content(15.82 kg/h,24 kg/h,36 kg/h,48 kg/h and 56.18 kg/h)and temperature(76.6℃,80 ℃,85 ℃,90 ℃ and 93.41 ℃).Adopting a central combination experiment method,using Design Expert software and response surface analysis method.It was found that with the increase of screw speed from 266 rpm to 434 rpm,the water absorption and water stability(water resistance time)gradually increased;the unit weight,starch gelatinization degree,oil absorption characteristics of particles and water solubility gradually decreased.With the moisture content increasing from 15.82 kg/h to 56.18 kg/h,the water absorption,water solubility and water stability(water resistance time)gradually increased;the bulk density,starch gelatinization degree and oil absorption characteristics of granules gradually decreased.With the temperature increasing from 76.6℃ to 93.41℃,the unit weight,starch gelatinization degree and water solubility gradually increased;the oil absorption characteristics,water absorption and water stability(water resistance time)of particles gradually decreased.The optimal process parameters were screw speed 362 rpm,moisture 42 kg/h,and temperature 88℃.