The Research Of Chinese Pulp And Paper Energy Consumption-the Research Of Alkali Recovery-system’s Energy Balance Computation

The calculation method of energy balance in alkali recovery system in the Chinese pulpand paper industry was studied in this paper. At the same time, the differences of alkalirecovery between wood pulp and straw pulp were analysed thoroughly. Taking the typicalalkali recovery systems of wood pulp and straw pulp in China as research subjects, theirenergy consumptions were calculated, including evaporation, burning and causticzing systems.By studying their calculation methods about heat energy, electricity energy and thermalefficiency, we can know the consumption of water, electricity, gas. Further the standards ofenergy consumption for wood pulp and straw pulp alkali recovery systems were established.In addition, energy consumption, productions and degree of self-sufficiency of wood pulp andstraw pulp alkali recovery systems were analysed in the paper.The theoretical basis of the article is the first law of thermodynamics and the second lawof thermodynamics. The key technology is to determine the scheme of energy balance. Thespecific implementation steps are as followes:The required information and data were collected by the investigations and studies to theplant. According to the characteristics of the system we can clear the system boundary.Baseing on the material balance we can draw block diagram of energy balance and identifythe process parameters. The input energy and output energy of each unit were calculatedseparately and determined the energy balance table. Finally, the appropriate ratio energy flowdiagram of system corresponding to block diagram was drawn according to the methoddescribed in GB6421-86. The balance of electricity energy is an important component ofenergy balance, it is allocated to each corresponding electrical device according to the actualload and need coefficient method.The conclusions are that:The alkali recovery of straw pulp can produce19145.57MJ heat energy, it isn’t used forgenerating electricity. The63.55%of heating energy produced by the alkali recovery of thestraw pulp can satisfy the whole energy demand of alkali recovery, including evaporation,burning and causticizing. The residual heat can satisfy51.95%energy consumption of the straw pulping.The alkali recovery of wood pulp can produce23476.43MJ heat energy, it can generateelectricity213.85kwh. The52.51%energy produced by the alkali recovery of the wood pulpcan satisfy the whole energy required of the alkali recovery including evaporation, burning,causticizing and lime mud recovery. It can satisfy the whole required energy of wood pulping.And the16.93%of heat energy was delivered.The level of the energy produced by the wood pulp alkali recovery in china wasdelivered16.93%of heat energy. It exceeds the level of developed country which was15.27%in Europe in the later stage of the last century.