Study On The Critical Technology Of Flaxseed Dehulling And Separation And Dehull Equipment

Flaxseed is rich in nutrients, containing flaxseed gum, lignans, linolenic acid, linoleic acid and other bioactive substances. Flaxseed was found to possess multiple bioactive properties including antitumor, antioxidant, immune system regulation, blood pressure reduction, hypolipidemic effects and prevention of cardiovascular disease. With the continuous improvement of quality of life and growing demand for food safety, flaxseed is widely accepted. Meanwhile, it also brings new opportunities for development of the deep processing industry of flaxseed. Flaxseed dehulling is difficult due to the small particle size, hard hull and small clearance between hull and kernel. At present, flaxseed is used for oil, and flaxseed meal for feed. These production processes are simple and do not allow the bioactive substances in flaxseed to be utilized, which causes the resource waste. Flaxseed dehulling and separation play a critical role in flaxseed deep processing, but the research of dehulling and separation equipment is still in primary stages, and there is no equipment for dehulling and separation on the market. Therefore, the research on the technology of dehulling and separation equipment will be helpful to break the bottleneck of cultivating easily and process hard, which can drive the development of the flaxseed industry and green agriculture, and bring huge economic and social benefits.For the shortage of flaxseed dehulling and separation machinery, this paper has performed deep theory analysis and experimental research of the basic properties and equipment of dehulling and separation. Main research achievements include:(1) The basic physical characteristics of flaxseed were studied, including initial moisture, size, thousand-grain weight and bulk density. Microstructures of flaxseed hull, kernel, cross section and longitudinal section of flaxseed were observed by scan electron microscope. The Texture Analyzer was used to study the shear properties of flaxseed in order to provide theoretical basis for the development of dehulling equipment.(2) According to the structure of flaxseed, extrusion-grind flaxseed dehulling equipment was designed. The whole design about flaxseed dehulling equipment was perforemed by Inventor, a parameter feature modeling software. Taking the dehulling rate and loss rate as the target, dehulling conditions were optimized based on the response surface method, and tests of three factors were designed using Design-Expert software. The optimal flaxseed dehulling condition was obtained as follows:flaxseed moisture 1.65%, millstone speed 1670rpm and millstone gap 1.60mm. Under these conditions, the dehulling rate was 60.8%, and the loss rate was 5.37%.(3) A three-dimensional model of the corona electrostatic separator was established by Inventor. The PDE tool box from MATLAB was used to simulate the distrilbution of electric field strength in the corona electrostatic separator. The effects of voltage, the distance from electrode to roller and electrode position on the electric field strength were studied.(4) The working parameters of the corona electrostatic separator are optimized through the box benhnken central composite experimental design in Design-Expert software. The optimal separation condition was obtained as follows:voltage 5.535kV, roller speed 189r/min and distance from electrode to roller 129.5mm. Under these conditions, kernel content in the flaxseed hull was 6.804%, and hull content in the flaxseed kernel was 1.37%.(5) The three-dimensional model of the winnower was established by Inventor. The flow field simulation of combination of airway chamber was used to analyz air flow field distribution of airway under different outlet pressures (-30Pa,-50 Pa,-100 Pa) and airway widths (30mm,50mm,80mm). The results showed that the air flow distribution was more uniform in the airway of 50mm and 80mm, but taking account the cost and the space utilization efficiency,50mm airway width was selected.(6) Based on the simulation analysis of the gas flow field, the isolation performance was tested. It was found that kernel content in the flaxseed hull was 8.63%, and hull content in the flaxseed kernel was only 0.15% when air speed was 3.24m/s. The effect of air speed on kernel content in the flaxseed hull and hull content in the flaxseed kernel showed significant. Besides, the combinatorial ways were tested, and the way of first winnowing then electrostatic separation was better than other ways.