K.F. Cen

Experimental studies on municipal solid waste pyrolysis in a laboratory-scale rotary kiln

A laboratory-scale, externally heated, rotary-kiln pyrolyser was designed and built. Pyrolysis tests were performed. Solid wastes (paper, paperboard, waste plastics including PVC and PE, rubber, vegetal materials, wood, and orange husk) were tested. The effects of heating methods, moisture contents and size of waste on pyrolysis gas yields and compositions, as well as heating values, were evaluated.

Pyrolysis of solid waste in a rotary kiln: influence of final pyrolysis temperature on the pyrolysis products

Temperature is one of the most important parameters in pyrolysis reaction. In present work, an externally heated laboratory-scale rotary-kiln pyrolyser was designed and developed. The influence of final pyrolysis temperature (FPT) on the pyrolytic products of solid wastes has been studied. Raising FPT caused increasing gas yield and decreasing semi-coke yield. The average heat value of the gas also changed with FPT. The content of aliphatic hydrocarbons in PE tar increased initially and then decreased with increasing FPT. Parallel to this, the content of aromatic ring changed conversely. FPT had obvious influence on the primary and elemental analysis data of the semi-cokes. The CO2 reactivity of the semi-cokes also varied with the FPT. The kinetic parameters of the semi-cokes were different for the same material at the different FPT.

Study on coal combustion characteristics in a W-shaped boiler furnace

A numerical simulation approach is given to investigate the characteristics of coal particle flow, heat transfer and combustion processes in a W-shaped furnace. In order to obtain, in detail, behaviors of coal combustion, many different coal particle sizes of two different load cases are used to predict the characteristics of combustion. The conclusions of the characteristics of coal particle trajectories, devolatilization, ignition time, ignition distance and burnout are drawn out in detail. These conclusions can be used to optimize the design and operation of the W-shaped furnace.

Simulation of ash deposit in a pulverized coal-fired boiler

A model has been developed to simulate deposit growth under slagging conditions. The model was coupled with a comprehensive combustion code to predict the flow field, the temperature field and the deposit growth behavior. The predictions indicate that the numerical model can be used to optimize the design and operation of pulverized coal-fired boilers.

Analysis of volatile species kinetics during typical medical waste materials pyrolysis using a distributed activation energy model.

The complex reactions of typical medical waste materials pyrolysis and the evolution of different volatile species can be well represented by a Distributed Activation Energy Model (DAEM). In this study, A thermogravimetric analyser (TGA), coupled with Fourier transform infrared analysis of evolving products (TG-FTIR), were used to perform kinetic analysis of typical medical waste materials pyrolysis. A simple direct search method was used for the determination of DAEM kinetic parameters and the yield of individual pyrolysis products under any given heating condition. The agreement between the model prediction and the experimental data was generally good. The results can be used as inputs to a pyrolysis model based on first-order kinetic expression with a Gaussian Distribution of Activation Energies as a sub-model to CFD code.

Numerical simulation of the flow and combustion processes in a three-dimensional, w-shaped boiler furnace

Numerical simulations of gas-solid flows, heat transfer and gas-particle combustion have been conducted for a three-dimensional, W-shaped boiler furnace. The gas-particle flow, distributions of temperature and concentrations of gaseous constituents, distributions of the rates of heat release, burnout rates of coal particles, and formations of volatiles and CO have been predicted.

Numerical and experimental investigation on the reduction of NOx emission in a 600 MW utility furnace by using OFA

The paper describes a three-dimensional computer simulation, developed to predict the formation of nitric oxide in a tangentially fired boiler furnace burning pulverized fuel. The model was applied to a 600 MW utility boiler under different operating conditions. As fuel nitrogen is released in proportion to burnout of pulverized coal particles, the particles are treated in a Lagrangian framework in order to track burning pulverized coal particles through the gas continuum. The prediction yields encouraging results compared to experimental data.

Modeling of NOX emissions from a W-shaped boiler furnace under different operating conditions

A numerical model for gas-particle flow dynamics has been combined with an NOx chemistry post-processor to predict the formation of nitric oxide in a three-dimensional, W-shaped boiler furnace burning pulverized fuel. The model includes complex interactions in gas-particle turbulent flow, heat transfer, gaseous chemical reaction, coal combustion, and NOx reaction chemistry. Because fuel nitrogen is released in proportion to burnout of pulverized coal particles, the particles are treated in a Lagrangian framework in order to track burning pulverized coal particles through the gas continuum. The results show capability of the model to describe NOx emissions under different operating conditions for full and partial loads.

Modeling of coal combustion and NOx formation in a W-shaped boiler furnace

A numerical model for the gas-particle flow dynamics has been combined with a NOx – chemistry post-processor to predict the formation of nitric oxide in a three-dimensional, W-shaped boiler furnace burning pulverized fuel. The model includes the complex interaction of gas-particle turbulent flow, heat transfer, gaseous chemical reaction, coal combustion, and NOx reaction chemistry. Because the fuel nitrogen is released in proportion to the burnout of the pulverized coal particles, the particles are treated in a Lagrangian framework in order to track burning pulverized coal particles through the gas continuum. The results show the capability of the model for describing NOx emissions under different operating conditions for full and partial load.

Experimental research on solid circulation in a twin fluidized bed system

Abstract A twin fluidized bed solid circulation system, in which two adjacent fluidized beds exchange solids, was developed for coal gasification to produce middle heating value gas. The effects of bed material, operation velocity, and bed structure on the solid circulating rate were tested at a small-scale test facility. Experimental results showed that the solid circulation rate of the system could be adjusted by changing gas velocities of two beds and could attain 30–40 times of the fuel feed rate, which would meet the demands of heat supply to an endothermic process of a gasifier. On the basis of experiments, reasonable operation and design parameters were put forward, which can be used to as a reference for the commercial gasifier design. A mathematical model was erected to calculate the solid circulation rate of the system, and it could predict well the solid flow rate through a horizontal orifice by comparison with experimental data.