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QC 20150409, Baltic Sea Region Programme, Interreg project Bioenergy Promotion, Task 5.1 ”Mapping the Baltic Sea Region on Technology Developments”, Part-financed by the European Union

The feasibility of direct causticization of kraft black liquor using titanates has been evaluated. This has been done by studying the kinetics of the reaction between sodium tri-titanate and sodium carbonate and describing the kinetics by appropriate reaction models. Furthermore, three different chemical recovery processes have been studied from an energy point of view: the conventional kraft recovery cycle using lime, the borate causticization process (as an add-on to conventional kraft recovery process) and the titanate causticization process combined with black liquor gasification has been made. Finally the carbon and carbon species transition during black liquor pyrolysis and gasification in the presence of sodium titanium compounds was studied. The experimental studies have been carried out in three different reactors; a small scale fixed bed reactor, a fluidized bed reactor and a pressurized entrained flow reactor. In the small scale fixed bed reactor the kinetics of the direct causticization reaction between sodium tri-titanate and sodium carbonate was studied at various temperatures between 800°C and 880°C, and in pure nitrogen or in nitrogen with 0.5-5% CO2. By fitting different kinetic models to the experimental data the overall reaction rate was found to be diffusion controlled at the lower temperature and chemical reaction controlled at higher temperatures. Furthermore, this change in mechanism was seen to be influenced by the carbon dioxide concentration in the reaction atmosphere in the way that the mechanism change occurred at higher temperatures. In the semi-batch fluidized bed the direct causticization reaction was studies at temperatures between 800-825°C. Conversions of the sodium carbonate up to 88% were obtained. The fitting of different kinetic models to the experimental data showed that the overall reaction rate in this equipment was controlled by the time taken for the reactants to achieve physical contact. The studies in the pressurized entr, Godkänd; 2002; 20061113 (haneit)

Godkänd; 2000; 20091123 (andbra)

Godkänd; 2000; 20091123 (andbra)

The solid state reaction between sodium tri-titanate and sodium carbonate, forming mainly sodium penta-titanate, was investigated. Experiments were carried out in a micro-differential reactor made of quartz glass at various temperatures between 800°C and 880°C and in a pilot fluidized bed reactor operated in a semi-batch mode. In the micro-differential reactor, basic kinetic data was obtained by measuring the release of carbon dioxide during the reaction. Different kinetic models were considered to describe the conversion, such as the Valensi-Carter model for diffusion controlled reaction rates and the phase-boundary model for first-order reaction kinetics. Furthermore, a model that included both diffusion in the solid material and the chemical kinetics was derived. This model described the experimental data obtained in the micro-differential reactor very well. Finally, rating models describing the conversion obtained in a fluidized bed and in an entrained flow reactor were developed., Godkänd; 1999; 20070403 (ysko)

The solid state reaction between sodium tri-titanate and sodium carbonate, forming mainly sodium penta-titanate, was investigated. Experiments were carried out in a micro-differential reactor made of quartz glass at various temperatures between 800°C and 880°C and in a pilot fluidized bed reactor operated in a semi-batch mode. In the micro-differential reactor, basic kinetic data was obtained by measuring the release of carbon dioxide during the reaction. Different kinetic models were considered to describe the conversion, such as the Valensi-Carter model for diffusion controlled reaction rates and the phase-boundary model for first-order reaction kinetics. Furthermore, a model that included both diffusion in the solid material and the chemical kinetics was derived. This model described the experimental data obtained in the micro-differential reactor very well. Finally, rating models describing the conversion obtained in a fluidized bed and in an entrained flow reactor were developed., Godkänd; 1999; 20070403 (ysko)