Evaporating And Properties Of Chemi-mechanical Pulping Waste Water

The boiling heat transfer coefficient of P-RC APMP waste water was studied.The experiment was carried out using the forced circulation evaporator.The influence of heat flux,velocity of flow and the solid content of P-RC APMP waste water on boiling heat transfer coefficient was investigated.The results show that under a certain heat flux,the boiling heat transfer coefficient of P-RC APMP waste water increases as the velocity of flow increases.The influence of flow velocity on the boiling heat transfer coefficient varies with the solid content of P-RC APMP waste water.It becomes greater as the solid content increases.Different multi-effect evaporation process were used,the energy consumption were accounted according to the measured boiling heat transfer coefficient,and were compared to the MVR (mechanical vapor compression).The results show that18.52kg standard coal is needed for evaporating each ton water in the five effect follow stream evaporator as well as26.17kg in the three effect follow stream evaporator,however,the production data of Sunpapergroup shows that6.81kg standard coal is needed in the MVR.From the above results,we can see that MVR has advantage in evaporating between2～15%concention.The properties of P-RC APMP waste water and BCTMP waste water were investigated to give the evidence of theory and experiment for the treatment of waste water,including relative density,baume degree,viscosity,surface tension,specific heat capacity,boiling pont rise(BPR) and elementary analysis of waste water dry solids.The results show that relative density, baume degree are tested well proportional to the solid content of P-RC APMP waste water and BCTMP waste water,and inverse proportional to the temperature.Viscosity is function of concentration and temperature,it increases with increase of solid content or decrease in temperature.At fixed temperature,the viscosity of P-RC APMP waste water rises sharply when solid content above about40%and the viscosity of BCTMP waste water rises sharply when solid content above about30%.Surface tension of P-RC APMP waste water changes wildly with rise in concentration firstly,however,when solid content above about35%,it rises as the concentration increases at fixed temperature.BCTMP waste water has similar surface tension property,its turning point is15%,however.Both gradually decrease as temperature rises.Specific heat capacity is related with the solid content,any increase in dry solids will decrease specific heat capacity,it has good proportional relation with solid content.BPR of P-RC APMP waste water is proportional to the solid content,when the solid content above30%,it increases sharply.The percentage of C element in the P-RC APMP waste water dry solids is31.18%,N element is0.46%,H element is3.93%,S element is0.008%.The inorganic content in P-RC APMP waste water solids is30.26%,organic matter content is69.74%,its HHV(high heat value) is12457kJ/kg; The inorganic content in BCTMP waste water solids is25.66%,organic matter content is74.34%,its HHV is16380kJ/kg.