Optimisation of Biomass/Coal Co-Firing Processes through Integrated Measurement and Computational Modelling

在英国和世界其他地区，生物质与煤在现有发电厂共烧被广泛采用作为减少二氧化碳排放的主要技术之一。尽管在开发混烧技术方面取得了各种进展，但由于生物质和煤在物理和燃烧性质上的固有差异，一系列技术问题仍有待解决。与混烧相关的典型问题包括火焰稳定性差、热效率低以及结渣和结垢。该项目旨在通过结合先进的燃料特性、综合测量和计算模型来实现生物质/煤共燃过程的优化。在燃料表征方面，将把热重分析和自动图像分析技术与传统的燃料分析方法结合起来，以实现对来自各种来源的生物质和生物质/煤混合物的全面表征。由于生物质和煤的物理性质不同，生物质/煤/空气三相流在供给燃烧器的燃料管路中的流体动力学是相当复杂的，在这一科学领域中知之甚少。本项目建议开发一种能够在线连续测量燃料管路中生物质/煤颗粒基本参数的仪器技术。该系统将允许监控和优化向燃烧器输送的燃料。该仪器技术将新颖的静电传感和数字成像原理与嵌入式系统设计方法相结合。所要测量的流动参数包括生物质/煤颗粒的粒度分布、速度和浓度以及生物质在混合物中的比例。众所周知，生物质的添加和煤日粮的变化会对燃烧稳定性和混燃效率产生重大影响。作为该项目的一部分，将开发一个包含数字成像设备和固态光学探测器的系统，用于持续监测燃烧器条件和共烧条件下的火焰稳定性。在三相流动和燃烧火焰特性的研究中，计算模型为实验测量提供了一个强有力的辅助工具。本项目将应用计算流体力学(CFD)模拟技术来研究不规则生物质颗粒及其与煤粉混合物在燃料管路中的动态行为以及相关的燃烧特性，特别是火焰稳定性。还将应用CFD模拟技术来研究生物质添加对灰渣沉积和结渣和结垢形成的影响。流量测量和火焰监测系统的测量将被整合，以建立和验证CFD模型。同时，模拟结果将被用来解释在各种情况下的实际测量。该项目财团由肯特、利兹和诺丁汉三个学术专业中心组成。除了英国和中国的发电组织的支持外，还与中国的三个领先研究中心建立了合作安排。在设计和实施仪器系统和计算建模工作之后，将在两国的燃烧试验台上进行实验工作。然后，仪器系统和计算模型将按比例扩大到全规模的发电站。将进行示范试验，以评估先进燃料表征技术的有效性、仪器系统的性能和可操作性，以及计算模型在一系列共燃条件下的有效性。将报告对现有发电厂联合燃烧过程的优化和对新工厂设计的建议。

Co-firing biomass with coal at existing power plant is widely adopted as one of the main technologies for reducing CO2 emissions in the UK and the rest of the world. Despite various advances in developing the co-firing technology, a range of technological issues remain to be resolved due to the inherent differences in the physical and combustion properties between biomass and coal. Typical problems associated with co-firing include poor flame stability, low thermal efficiency, and slagging and fouling. This project aims to achieve the optimisation of biomass/coal co-firing processes through a combination of advanced fuel characterisation, integrated measurement and computational modelling. In the area of fuel characterisation, both thermo-gravimetric analysis and automated image analysis techniques in conjunction with conventional fuel analysis methods will be combined to achieve comprehensive characterisation of biomass and biomass/coal blends from a wide range of sources. Because of the physical differences between biomass and coal the fluid dynamics of the biomass/coal/air three-phase flow in the fuel lines feeding the burners is rather complex and very little is known in this area of science. It is proposed in this project to develop an instrumentation technology capable of measuring the basic parameters of the biomass/coal particles in the fuel lines on an on-line continuous basis. The system will allow the monitoring and optimisation of the fuel delivery to the burners. The instrumentation technology combines novel electrostatic sensing and digital imaging principles and embedded system design methodology. The flow parameters to be measured include particle size distribution, velocity and concentration of biomass/coal particles as well as biomass proportion in the blend. It is known that biomass addition and variations in coal diet can have a significant impact on combustion stability and co-firing efficiency. As part of this project, a system incorporating digital imaging devices and solid state optical detectors will be developed for the continuous monitoring of the burner conditions and flame stability under co-firing conditions. Computational modelling provides a powerful supplementary tool to experimental measurement in the studies of three-phase flow and combustion flame characteristics. Computational Fluid Dynamic (CFD) modelling techniques will be applied in this project to investigate the dynamic behaviours of irregular biomass particles and their blends with pulverised coal in the fuel lines and associated combustion characteristics particularly flame stability. CFD modelling techniques will also be applied to study the impact of biomass addition on ash deposition and formation of slagging and fouling. The measurements from the flow metering and flame monitoring systems will be integrated to establish and validate the CFD models. Meanwhile, the modelling results will be used to interpret the practical measurements under a wide range of conditions.The project consortium comprises three academic centres of expertise including Kent, Leeds and Nottingham. Collaborative arrangements with three leading research centres in China have been established in addition to support from power generation organizations in the UK and China. Following the design and implementation of the instrumentation systems and computational modeling work, experimental work will be performed on combustion test rigs in both countries. The instrumentation systems and computational models will then be scaled up for full scale power stations. Demonstration trials will be undertaken to assess the efficacy of the advanced fuel characterisation techniques, the performance and operability of the instrumentation systems, and the validity of the computational models under a range of co-firing conditions. Recommendations for the optimization of co-firing processes at existing power plant and on the design of new plant will be reported.