随着新能源的大规模装机，新能源消纳问题愈发严峻，电力系统对调峰及高灵活调节能力资源的需求显著增加。我国的资源禀赋决定了采用燃煤机组调峰及灵活发电在经济性、可靠性和国家能源安全方面具有天然优势。循环流化床机组是燃煤机组的重要组成部分，其本身具有很好的负荷适应性，具有很好的调峰特性，然而由于其炉内有大量的耐磨耐火材料、床料、循环物料、工质以及受热面金属等，锅炉运行过程中积蓄大量热量，形成了循环流化床锅炉的热惯性，成为其变负荷速率提高的主要瓶颈之一，因此，要进一步提高循环流化床机组的负荷响应速率，首先应对其热惯性特性开展系统研究。本文提出采用单位发电功率变化对应的锅炉蓄热量变化量来表征锅炉的热惯性。通过现场采集330MW 循环流化床锅炉的运行数据，对热惯性进行分析，从而揭示炉内各蓄热体对锅炉总热惯性的影响规律以及在机组不同负荷区间变负荷过程中热惯性的变化规律。然后，分析循环流化床锅炉在变负荷过程中的传热特性，以确定热惯性的作用机制。采用基于能量守恒原理的控制容积法编写了非稳态传热计算程序，计算变负荷过程中耐磨耐火材料和金属受热面处的温度分布及热量传递特性，明确热惯性在变负荷过程中的具体影响和作用机制。此外，还提出了使用高导热防磨材料和金属格栅来替代循环流化床锅炉中传统耐磨耐火材料的优化方案，并对耐磨耐火材料替换后的锅炉热力性能、热惯性及动态特性进行了分析。研究结果表明，炉膛水冷壁和分离回料系统是循环流化床锅炉内热惯性最大的部件，它们的热惯性约占锅炉总热惯性的80%；在不同负荷区间，耐磨耐火材料占总热惯性的比例均超过50%，工质热惯性占比约为25%；循环流化床锅炉在低负荷区间具有更大的热惯性，30%-50%负荷区间的热惯性是75%-100%负荷区间热惯性的约1.6倍。锅炉负荷从75%变化到100%，仅由于热惯性导致的工质参数延迟约451s。使用金属格栅和高导热材料替代耐磨耐火材料可以有效降低锅炉的热惯性，提高锅炉的变负荷速率和运行稳定性。不同负荷区间负荷变化时，锅炉整体热惯性降幅均约为30-35%。这种热惯性的减小有助于提高锅炉的变负荷响应速率，满足消纳新能源对火电机组提出的灵活运行需求。
With the large-scale deployment of new energy, the challenge of accommodating new energy sources has become increasingly severe, and the demand for peaking and highly flexible resources in the power system has significantly increased. China‘s resource endowment provides natural advantages in terms of economic, reliability, and national energy security in using coal-fired power plants for peaking and flexible power generation. Circulating fluidized bed (CFB) boilers, as a critical component of coal-fired power plants, exhibit excellent load adaptability and peaking characteristics. However, the accumulation of a large amount of heat in CFB boilers during operation, due to the presence of refractory materials, bed materials, circulating materials, working media, and heated metal surfaces, forms a thermal inertia that hinders the rate at which the boiler can change its load. Therefore, further research into the thermal inertia characteristics of CFB boilers is necessary to improve their load response rate.In this study, we propose to characterize the thermal inertia of the boiler by using the amount of heat accumulation in the boiler corresponding to the change of unit power generation. By analyzing the operating data of a 330MW CFB boiler, the thermal inertia is quantitatively calculated to reveal the influence of each heat accumulator in the furnace on the total thermal inertia of the boiler, and the change law of thermal inertia in the process of different variable loads. We analyze the heat transfer characteristics of the CFB boiler during the variable load process to determine the time-domain characteristics of thermal inertia. Using the controlled volume method based on the principle of energy conservation, we develop a non-stationary heat transfer calculation program to compute the temperature distribution and heat transfer characteristics at the refractory and metal heating surfaces during the variable load process, and to clarify the specific effects and mechanisms of thermal inertia in the variable load process.Furthermore, we propose an optimized solution of using highly thermally conductive anti-friction materials and metal grids to replace the existing refractory materials in CFB boilers. We analyze the thermal performance, thermal inertia, and dynamic characteristics of the boiler after refractory replacement. The results of the study show that the furnace water-cooled wall and the separation return system are the components with the largest thermal inertia within the CFB boiler, and their thermal inertia contribution accounts for about 80% of the total thermal inertia of the boiler. Refractory materials and work materials are the main sources of thermal inertia for the entire boiler. In addition, CFB boilers have higher thermal inertia in the low load region, and the thermal inertia of the refractory material causes a delay of up to 187s in reaching a new steady state.Replacing refractory materials with metal grids and highly thermally conductive materials can effectively reduce the thermal inertia of the boiler and improve its variable load rate and operational stability. The overall thermal inertia reduction of the boiler is about 30-35%, which helps the boiler to respond faster to load changes and meet the demand for flexible peaking.
