Kinetics Of Pyrolysis Of Reed Pulp Black Liquor And Experimental Study On Pyrolysis In Fluidized Bed

In the present world, the environment is deteriorating and the shortage of resources is due to the overuse of fossil fuel. China consumes a large amount of coal and also faces this problem. Biomass is a clean and sustainable energy, in recent years it has been concern widely in the energy community and it is also considered as one of the most ideal alternatives for fossil fuel fuels. China has a rich variety of biomass and the amount of biomass is large, biomass can be used in place of a considerable portion of fossil fuels.Papermaking black liquor belongs to approximate biomass, it has the general characteristics of biomass and but has its own characteristics, for example, high COD concentration, high alkalinity and high organic content. Untreated direct emissions can cause serious environmental pollution. Generally, the conventional alkali recovery boiler is used for treatment of wood pulp black liquor, but the effect is not ideal for treating straw pulp black liquor, this is caused by black liquor’s characteristics of high viscosity,high silicon content and low calorific value. Therefore a new recycling technology is needed to develop for treating straw pulp black liquor, a fluidized bed pyrolysis treatment technology of straw pulp black liquor for alkali recovery is proposed in this paper. The reed pulp black liquor is selected as raw material, The kinetic parameters of pyrolysis reaction of the reed pulp black liquor are calculated, its mechanism of reaction kinetics are studied. The pyrolysis experiment of reed pulping black liquor was carried out in a small fluidized bed and the mechanism of its pyrolysis was obtained. It provides the theoretical basis for the application of the technology of the recovery of the pyrolysis of the fluidized bed.First, according to the 3 temperature interval of reed pulp black liquor pyrolysis and the known TG and DTG curves of reed pulp black liquor, The kinetic parameters of pyrolysis reaction were solved by using Coats-Redfern, Flynn-Wall-Ozawa, Friedman,and Kissinger method which were in common use in reaction kinetics calculation. The results showed that the reaction mechanism of reed pulping black liquor by Coats-Redfern method was random nucleation and subsequent growth. The error caused by the choice of the reaction mechanism was avoided by Flynn-Wall-Ozawa and Friedman method and the accuracy of the results was higher. The Kissinger method could only analyze the data points of the peak points, and there were large deviations in some results for Kissinger method.Secondly, the calcium based zeolite was selected as the bed material and the nitrogen was selected as the fluidization medium, the temperatures of the experiment were selected by 530, 580, 630, 680, 730 and 780℃, the pyrolysis process of reed pulpblack liquor in a small fluidized bed was carried out, and the gas phase, liquid phase and solid phase products were obtained. The test results of these products were obtained by means of the corresponding detection method. These researches showed that the higher pyrolysis temperatures were suitable for the pyrolysis process, the specific performances were that the pyrolysis gases were obtained, and the combustible gases could account for a large proportion of the pyrolysis gases, the formation of tar was suppressed, the volatile content of the residual in the semi coke of the black liquor could be reduced, the conversions of carbon and hydrogen were increased, and the losses of carbon and hydrogen were reduced. The pyrolysis temperature had a significant impact on the variation of the components of each phase of product. For gas products pyrolysis, with increase of the pyrolysis temperature, the volume concentration of H2 and CO gradually increased the volume concentration of CH4 gradually reduced, the volume concentration of CO2 were declining. For tar which was liquid phase product, the yield was decreased with the increase of pyrolysis temperature, the relative contents of polycyclic aromatic hydrocarbons were more at high temperature. For solid phase product, the high calorific value of the semi coke decreased with the increase of the pyrolysis temperature. The micro morphology of the semi coke was greatly influenced by the pyrolysis temperature.Analysed comprehensively, the most ideal pyrolysis temperature was 780℃.