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A comprehensive three-dimensional (3D) numerical model is developed for simulation of entrained coal slurry gasifiers. In this model, a presumed probability density function (PDF) method is used to consider turbulent effects on gas-phase reactions in the gasifier. A realizable k-ε model is adopted to predict turbulence information. Coal slurry particles are tracked with the Lagrangian method. The coal slurry gasification process is divided into several simple subprocesses, which are droplet evaporation, boiling, devolatilization, and heterogeneous reactions of coal char particles. The particle-source-in-cell method is adopted to couple gas-particle interactions. With this methodology, simulations for GE and staged coal slurry gasifiers are completed. A comparison between the predictions and measured data shows that the proposed model correctly predicts the global performance of the coal gasification process. The mixing process in the staged gasifier is better than that in the GE gasifier because of the existence of secondary flow. The particle size has a negative effect on coal conversion. The effects of the coal slurry concentration and molar ratio of oxygen/carbon on the gasifier performance are also studied in this paper.

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Studies on circulating fluidized bed (CFB) boilers have being conducted at the Tsinghua University (TH) for about two decades and much of works are done to link the fundamentals with practical application. A full set of design theory was developed and some key elements of this theory are presented in this paper. First, a classification of state of the solid-gas two-phase flow in CFB boiler is given. TH’s studies validated that a CFB boiler can be generally described as the superposition of a fast bed in the upper part with a bubbling bed or turbulent bed in the bottom part. A concept model of material balance for the open system of CFB boiler was developed and later improved as a more comprehensive 1-D model taking ash formation, particle attrition and segregation in bed into account. Some results of the models are discussed. Then the concept of State Specification of a CFB boiler is defined and discussed. The State Specification is regarded as the first step to design a CFB and a base to classify different style of CFB boiler technologies for various CFB boiler manufacturers. The State Specification adopted by major CFB boiler makers is summarized and associated importance issues are addressed. The heat transfer model originally developed by Leckner and his coworkers is adopted and improved. It is further calibrated with experimental data obtained on the commercial CFB boiler measurements. The principle, improvements and application of the model are introduced. Some special tools developed for heat transfer field test are also given. Also, combustion behaviors of char and volatile content are studied, and the combustion difference between a CFB boiler and a bubbling bed is analyzed. The influence of volatile content and size distribution is discussed. The concept of vertical distribution of combustion and heat in CFB boiler furnace is introduced and discussed as well. In the last, the suggested design theory of CFB boiler is summarized.

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