Analysis And Optimization Of Flow Field Of Vertical High-consistency Hydraulic Pulper And Research On The Effect Of Pulping Efficiency

In recent years,China has been actively promoting circular economy and sustainable development,leading to increasing demand for packaging paper and recycled pulp board.However,due to the shortage of fiber resources for papermaking in China,as well as the ban on solid waste imports and plastic bags,and the advocacy for resource recycling,low-carbon energy conservation,etc.,paper recycling has attracted much attention.Pulp-molded products made mainly from waste paper and recycled pulp board are green products that are pollutionfree,recyclable,degradable,and with good performance,which are widely used in the packaging industry and are the best choice for "paper replacing plastic".The market potential for pulp-molded products is enormous.The disintegration of waste paper or pulp board is an important raw material pulping process for pulp molded products,and a hydraulic pulper is a key disintegration equipment in this process,generally using a vertical hydraulic pulper.Therefore,improving the disintegration efficiency of hydraulic pulpers and reducing equipment energy consumption is of great significance to promoting the development of the paper molding industry and promoting the substitution of paper for plastic.The structure of the pulper and the pulping process parameters are the main factors affecting the disintegration efficiency and equipment energy consumption.This paper studies the two aspects of the impact of pulper structure and pulping process on pulp performance,and the specific research contents are as follows:(1)Based on the flow theory of pulp and the conditions for achieving fluidization of pulp,the flow characteristics of three representative commercial pulp(wood pulp,bamboo pulp,and waste paper pulp)were studied.The results showed that the flowability of wood pulp was poor at the same concentration,so the conditions for achieving fluidization of wood pulp were higher than those of bamboo pulp and waste paper pulp.Based on the design theory of a high concentration hydraulic pulping machine,the rotor and trough structure that mainly affect the disintegration efficiency and energy consumption of the pulper were preliminarily designed.(2)Using FLUENT software and a controlled variable method,the influence of rotor blade number,rotor-to-bottom clearance and turbulence plate number on the internal flow field of the hydraulic pulper was investigated and Optimized the structure of the pulp crusher.In the optimized structure,the rotor has 2 blades,a bottom clearance of 10 mm,and 3 spoilers.After optimization,the power consumption of the equipment is reduced by 8.50% compared to the original structure.The motion of pulp within the optimized structure was simulated numerically to further verify the rationality of the machine structure.(3)Customized production was carried out on the optimized structure of the pulping machine,and experimental verification was conducted through pulping tests.The test results showed that the equipment met the design requirements.However,the slurry flow rate was slow when processing high-concentration slurry.In order to further improve the pulping efficiency,a reject plate was designed and installed at the bottom of the rotor.After the installation of the reject plate,the pulping efficiency was improved by a factor of two.And compared with the commercial pulping machine in the laboratory,the pulping efficiency of the test bench is better.In this paper,the circulation flow characteristics in the tank of pulper equipped with pulp slinger were studied when three kinds of pulps were pulped.It was found that cavitation occurred in wood pulp board,waste paper pulp board and bamboo pulp board when the pulp concentration was 13%,16% and 14%,respectively.(4)Through experiments on process parameters such as pulp concentration,rotor speed,and pulping time,the disintegration efficiency of wood pulp,bamboo pulp,and waste paper was analyzed.The experimental results showed that the optimal disintegration conditions for wood pulp board were pulp concentration of 10%,rotor speed of 700 r·min-1,and pulping time of 10 min;the optimal disintegration conditions for the waste paper were pulp concentration of14%,rotor speed of 600 r·min-1,and pulping time of 20 min;the optimal disintegration conditions for bamboo pulp board were pulp concentration of 11%,rotor speed of 600 r·min-1,and pulping time of 5 min.These results have guiding significance for the actual production of pulp disintegration.