The Influence Of The Addition Of CMC And Beating Method On The Yield Stress Of CMP Fiber Suspension

"Material structure"and"environmental protection"are important strategic issues for the pulp and paper industry at present and in the future.In terms of material structure,fast-growing poplar wood has become an important materials for pulp and paper making,from the viewpoint of energy saving and consumption reduction,the beating process is the main energy consumption stage in pulp and paper making process.Therefore,it is great significance to study the change of yield stress of poplar APMP pulp during beating process treated by CMC.As one of the most important rheological parameters of PFS,the yield stress has an important guiding significance for the optimization of the pulp and paper process and the optimization of the design and selection of equipment.In this paper,based on the principle of yield stress of PFS,summarized the research status of yield stress at home and abroad.Firstly,the yield stress of poplar APMP and eucalyptus BKP fiber suspension were measured by shear stress ramp method in the mass concentration of 1%~3%,then compared with each other.In addition,based on analysis the relationship between beating degree and yield stress,after added with a certain amount of CMC and pretreated for 10 min,poplar APMP were refined separately with Valley beater and PFI mill,and,then,the influences of the refining ways and adding CMC pretreatment on beating degree and yield stress of poplar APMP fiber suspension were separately analyzed.In the end,summarized the applications of yield stress in pulp fiber suspension transported in pipe.Through a series of experiments and researches,the main results of this paper are identified as follows:(1)Compared with Eucalyptus BKP,poplar APMP fiber has higher initial beating degree,shorter fiber and more fine fiber content.The length of the fiber and the mass concentration of the PFS have a significant effect on the yield stress.With the increase of fiber length and fiber suspension concentration,the yield stress of PFS was also increased.(2)Over the range of concentrations tested of poplar APMP and Eucalyptus BKP,the yield stress ?_y was found to depend on the concentration C_m via a power law relationship ?_y=a C_m~b.The yield stress of two PFS at a specific mass concentration can be estimated by the exponential equation.(3)The yield stress of the poplar APMP fiber suspension,with a certain beating degree,increased rapidly with the concentration increasing,and the yield stress was found to depend on the concentration via a power relationship(the values of a and b are closely related with the beating ways and beating degree);after refined under a low concentration by a free beating device(E.g Valley beater),the yield stress of the poplar APMP fibers suspension decreased as the beating degree increased,while the results were reversed under the medium concentration refining by a shiny beating device(E.g PFI mill).(4)After the poplar APMP was added with CMC of 4.5%dry pulp weight and pretreated for10 min,the yield stress of the poplar APMP fibers suspension are at a minimum value,the value decreased from 30.14Pa to 19.43Pa(PFS mass concentration is 3%).(5)After the poplar APMP was added with CMC of 2%dry pulp weight and pretreated for10 min,and then refined,the beating degree might increase from 45°SR to 48°SR with valley beater's refining and from 40°SR to 50°SR with PFI mill's refining,meanwhile,the yield stress of the poplar APMP fibers suspension are at a minimum value with the same beating conditions,the minimum value of the yield stress is respectively 16.4Pa and 22.8Pa(PFS mass concentration is 3%).(6)PFS yield stress can be used to calculate the head loss under different flow regime in the process of pipeline transportation(Plug flow,Laminar flow,Turbulent flow).This paper can provide theoretical basis for the research and development and optimization design of process and equipment technology with high efficient,energy-saving and low consumption for some sections such as beating,transport,screening and mixing processes in the production of the poplar APMP.