Junfu Lv

Effects of the Updated National Emission Regulation in China on Circulating Fluidized Bed Boilers and the Solutions To Meet Them

The advantage of circulating fluidized bed (CFB) boilers in China is their ability to utilize low rank coal with low cost emission control. However, the new National Emission Regulation (NER) issued in early 2012 brings much more stringent challenges on the CFB industries, which also causes much attention from other countries. Based on the principle of a CFB boiler and previous operating experience, it is possible for the CFB boilers to meet the new NER and maintain the advantage of low cost emission control, while, more influences should be considered in their design and operation. To meet the requirement of the new NER, the fly ash collector should adopt a bag house or combination of electrostatic precipitator and bag filter to ensure dust emissions of less than 30 mg · Nm(-3). For SO2 emission control, the bed temperature should be strictly lower than 900 °C to maintain high reactivity and pores. The limestone particle size distribution should be ranged within a special scope to optimize the residence time and gas-solid reaction. At the same time, the injecting point should be optimized to ensure fast contact of lime with oxygen. In such conditions, the desulfurization efficiency could be increased more than 90%. For lower sulfur content fuels (<1.5%, referred value based on the heating value of standard coal of China), increasing Ca/S enough could decrease SO2 emissions lower than that of the new NER, 100 mg · Nm(-3). For fuels with sulfur content higher than 1.5%, some simplified systems for flue gas desulfurization, such as flash dryer absorber (FDA), are needed. And the NOx emissions of a CFB can be controlled to less than 100 mg · Nm(-3) without any equipment at a bed temperature lower than 900 °C for fuels with low volatiles content (<12%), while for fuels with high volatiles, selective non-catalytic reduction (SNCR) should be considered. Due to the unique temperature in CFB as well as the circulating ash, the efficiency of SNCR could reach as high as 70%. The Hg emission of CFB is very low for the new NER due to its innate property.

Dynamic modelling and simulation of IGCC process with Texaco gasifier using different coal

Integrated gasification combined cycle (IGCC) is considered as a viable option for low emission power generation and carbon dioxide sequestration. As a part of the process of IGCC plant design and development, modelling and simulation study of the whole IGCC process is important for thermodynamic performance evaluation, study of carbon capture readiness and economic analysis. The work presented in the paper is to develop such a whole system model and simulation platform. A simplified dynamic model for the IGCC process is developed, in which Texaco gasifier is chosen to give the basic representation for the IGCC process. The chemical equilibriums principle is used to predict the syngas contents in the modelling procedure. The influences of key parameters to regulate the input such as oxygen/coal ratio and water/coal ratio to syngas generation are studied. The simulation results are validated by comparing with the industry data provided by the Lu-nan fertilizer factory. Water-shift reactor, gas turbine and heat recovery steam-generation modules are modelled to study the dynamic performance with respect to the variation from the input of syngas stream. The simulation results reveal the dynamic changes in the plant outputs, including gas temperature, power output and mole percentages of hydrogen and carbon dioxide in the syngas. The process dynamic responses with three types of coal inputs are studied in the paper and their dynamic variation trends are presented via the simulation results.

Mathematical Modelling for Coal Fired Supercritical Power Plants and Model Parameter Identification Using Genetic Algorithms

The paper presents the progress of our study of the whole process mathematical model for a supercritical coal-fired power plant. The modelling procedure is rooted from thermodynamic and engineering principles with reference to the previously published literatures. Model unknown parameters are identified using Genetic Algorithms (GAs) with 600MW supercritical power plant on-site measurement data. The identified parameters are verified with different sets of measured plant data. Although some assumptions are made in the modelling process to simplify the model structure at a certain level, the supercritical coal-fired power plant model reported in the paper can represent the main features of the real plant once-through unit operation and the simulation results show that the main variation trends of the process have good agreement with the measured dynamic responses from the power plants.

Dynamic modelling and simulation study of a university campus CHP power plant

Combined Heat and Power (CHP) has become one of the most widely used technologies to provide electricity and heat with a single plant. Modelling and simulation study of the CHP process is important for power and thermodynamics evaluation and economic analysis. A simplified dynamic model based on the University of Warwick micro-CHP power plant is developed in this paper. In this CHP process, a gas turbine module is adopted and modelled as the gas engine based on methane combustion principle to generate electricity. Heat recovery system and auxiliary boiler modules are developed for thermal power generation. The simulation results of the gas engine and each auxiliary sub-system are validated by comparing the results with the operating data collected by the Estates Team of the University of Warwick. In addition, the dynamic performance of the whole CHP process is studied with respect to the variation from the input of syngas stream. The simulation results show the dynamic changes of key output variables, including electricity generation, thermal power output and water output temperature. The simulation results of one summer working day and one winter working day of gas engine and heat exchanger are compared with operation data. The auxiliary boiler simulation data is analyzed and compared with collected operation data of one spring and one winter working day.

Effects of Cyclone Structures on the Pressure Drop Across Different Sections in Cyclone Under Gas–Solid Flow

The pressure drop is a key performance of the cyclone in the circulating fluidized beds, and it shows a nonlinear change with the increase in inlet solids loading at certain gas flow rate. The nonlinear characteristic is related to the effect of solid behaviors on the pressure drop in different sections of the cyclone. The adjustment of cyclone structures would influence the pressure drop of different sections, changing the nonlinear characteristic. To improve the understanding of the nonlinear characteristic, the pressure drops across the inlet, the swirling part, and the vortex finder are measured, respectively, under different inlet solid loadings, and effects of the inlet dimensions, the barrel dimensions, and the vortex finder dimensions are investigated. Compared with the pure gas flow, the solid behaviors influence the gas flow in different section of the cyclone, leading to the changes in pressure drop across each section. The pressure drop across the inlet is positive related to the solid loading because of the solid acceleration; however, the pressure drop across the swirling section is negative related to the solids loading due to the weak effect on the swirling energy. The effect of solid loading on the pressure drop across the vortex finder is obscure due to the low solid loading in the upward gas flow accompanying the rotation movement. In addition, the narrowing of the inlet enhances the solid acceleration in the inlet and improves the swirling energy in the barrel by increasing the input tangential velocity, which greatly increases the pressure drop across the inlet and the swirling section. The extending of barrel enhances the weak effect caused by the solid loading on the swirling energy and reduces the pressure drop across the swirling section. The enlarging of vortex finder greatly reduces the axial velocity, reducing the pressure drop across the vortex finder.

Mass Balance Performance of A 300 MW CFB Boiler Burning Blend Fuel with Different Mixing Ratio

In order to predict the mass balance of a 300 MWe circulating fluidized bed (CFB) boiler under design process, the ash formation and attrition characteristic of the design fuel mixed with gangue, middling and slime were investigated with Tshinghua own process. In addition, the mass balance in this CFB boiler was simulated with 1D mass balance model, giving the ratio of the ashes, particle size distribution of circulating solid materials and solid circulating rat, Gs. By comparing the residence time distribution and the burn out time required for different size, the minimum bed pressure drop (BPD) or bed inventory in the furnace was determined for different mixing ratio among the three coals.