Model Identification Based on Subspace Model Identification of Main Steam Temperature in Ultra-Supercritical Coal-Fired Power Unit

Ultra-supercritical(USC) unit is more and more popular in coal-fired power industry.In this paper,closed-loop identification based on subspace model identification(SMI) is introduced for superheated steam temperature system of USC unit.Closed-loop SMI is applied to building step response model of the unit directly.The parameters selection method is proposed to deal with the parameter sensitivity and improve the reliability of the model.Finally,the model is used in model identification of real USC unit.

Research on the Prediction of Load Regulation Capacity for Supercritical Thermal Power Unit

Both the modeling and the load regulation capacity prediction of a supercritical power plant are investigated in this paper. Firstly, an indirect identification method based on subspace identification method is proposed. The obtained identification model is verified by the actual operation data and the dynamic characteristics of the system are well reproduced. Secondly, the model is used to predict the load regulation capacity of thermal power unit. The power, main steam pressure, main steam temperature and other parameters are simulated respectively when the unit load is going up and down. Under the actual constraints, the load regulation capacity of thermal power unit can be predicted quickly.

Application of Homemade DCS in Integrated BOP Control of 600-MW Supercritical Unit

The PLC and upper computer are used in BOP control system of traditional thermal power plant to monitor the in-situ equipment. It is complicated and wastes labor and resources. It is difficult to maintain and manage them. Beijing GuoDian ZhiShen Control Technology applied the homemade DCS (EDPF-NT System) to the integrated BOP control system of 600-MW supercritical power unit, which offers advantages in efficiency promotion, cost reduction and resource sharing. That also reflects the dominance of EDPF-NT System in performance, price, real-time DUP, network compatibility and communication. This article introduces the main characteristics, structure and configuration of EDPF-NT System, as well as the hierarchical operation, the multi-domain network structure and the private network router developed for Zhuanghe Power Plant.

A novel carbon trap sampling system for coal-fired flue gas mercury measurement

A novel carbon trap sampling system for gas-phase mercury measurement in flue gas is developed, including the high efficient sorbents made of modified biomass cokes and high precision sorbent traps for measuring particle-bound and total vapor-phase mercury in flue gas. A dedusting device is installed to collect fine fly ash for reducing the measurement errors. The thorough comparison test of mercury concentration in flue gas is conducted between the novel sampling system and the Ontario hydro method （OHM） in a 6 kW circulating fluidized bed combustor. Mercury mass balance rates of the OHM range from 95.47% to 104.72%. The mercury breakthrough rates for the second section of the sorbent trap are all below 2%. The relative deviations in the two test cases are in the range of 15. 96% to 17. 56% under different conditions. The verified data suggest that this novel carbon trap sampling system can meet the standards of quality assurance and quality control required by EPA Method 30B and can be applied to the coal-fired flue gas mercury sampling system.

Experimental Study on Performance of Supercritical CO_2 Heat Exchanger with Four Different Inner Tubes

The experiment was conducted to investigate the heat transfer performance of supercritical CO_2 in a casing heat exchanger by comparing their heat transfer,entropy production unit number,non-dimensional entropy production rate and field synergy factor.The results show that both heat transfer and entropy production unit number in four tubes decrease with water temperature increasing.Heat transfer and entropy production unit number in multiple tubes( i. e.,triple straight tube and double helix tube) is higher than their single counterparts; the non-dimensional entropy production rate increases with water temperature. Non-dimensional entropy production rate of triple straight tube and double helix tube is far below the single tube. Field synergy factor of double helix tube is much higher than that of the triple straight tube under the same condition. Further experiment was carried out in double helix tube,under various CO_2 pressure and inlet water temperature,the results are analyzed and reported in this paper.

The Effects of SO_3 in Flue Gas on the Operation of Coalfired Units and Countermeasures

There exists a certain amount of SO_3 in flue gas discharged from coal-fired power plants. With the operation of the selective catalystic reduction( SCR) denitrification system,SO_3 concentration in the flue gas increases,which will lead to fouling,erosion and plugging of downstream equipment. In this study,the main effects of SO_3 on the safety,stability and efficiency of units were analyzed,and measures to control SO_3 were proposed.

Performance Analysis of Cooling Wall of Supercritical CO_(2) Coal-Fired Plants

Using supercritical CO_(2)(S-CO_(2)) instead of water steam as heat transfer fluid for coal-fired power plants is another way to further improve the power generation efficiency. In this paper, a multi-field coupling model that integrates fluid flow, heat transfer and thermal stress is proposed to solve the complex problem. The effects of the key operating parameters on the performances of the cooling wall are numerically investigated. More details of the characteristics of fluid dynamics, thermal stress, pressure drop, coupled heat transfer and the whole flow and temperature fields in the S-CO_(2) cooling wall are revealed and discussed. A comparison study is made between the cooling wall tube and waterwall tube. Both temperature and thermal deformations of cooling wall tube are much higher than that of water. Numerical simulation results indicate that inclination angle has little effects on the temperature distribution, while increase of pressure drop is obvious as the inclination angle increases. Increasing tube diameter can effectively reduce both the pressure drop and the temperature of the cooling wall tube. As a result, a new insight is introduced for the design of S-CO_(2) power cycle.

Energy conservation in China's coal-fired power industry by installing advanced units and organized phasing out backward production

Coal-fired power is the main power source and the biggest contributor to energy conservation in the past several decades in China.It is generally believed that advanced technology should be counted on for energy conservation.However,a review of the decline in the national average net coal consumption rate(NCCR)of China's coal-fired power industry along with its development over the past few decades indicates that the upgradation of the national unit capacity structure(including installing advanced production and phasing out backward production)plays a more important role.A quantitative study on the effect of the unit capacity structure upgradation on the decline in the national average NCCR suggests that phasing out backward production is the leading factor for the decline in the NCCR in the past decade,followed by the new installation,whose sum contributes to approximately 80%of the decline in the national average NCCR.The new installation has an effective affecting period of about 8 years,during which it would gradually decline from a relatively high value.Since the effect of phasing out backward production may remain at a certain degree given a continual action of phasing out backward capacity,it is suggested that the organized action of phasing out backward production should be insisted on.

Tempospacial energy-saving effect-based diagnosis in large coal-fired power units:Energy-saving benchmark state

The energy-saving analytics of coal-fired power units in China is confronting new challenges especially with even more complicated system structure, higher working medium parameters, time-dependent varying operation conditions and boundaries such as load rate, coal quality, ambient temperature and humidity. Compared with the traditional optimization of specific operating parameters, the idea of the energy-consumption benchmark state was proposed. The equivalent specific fuel consumption(ESFC) analytics was introduced to determine the energy-consumption benchmark state, with the minimum ESFC under varying operation boundaries. Models for the energy-consumption benchmark state were established, and the endogenous additional specific consumption(ASFC) and exogenous ASFC were calculated. By comparing the benchmark state with the actual state, the energy-saving tempospacial effect can be quantified. As a case study, the energy consumption model of a 1000 MW ultra supercritical power unit was built. The results show that system energy consumption can be mainly reduced by improving the performance of turbine subsystem. This nearly doubles the resultant by improving the boiler system. The energy saving effect of each component increases with the decrease of load and has a greater influence under a lower load rate. The heat and mass transfer process takes priority in energy saving diagnosis of related components and processes. This makes great reference for the design and operation optimization of coal-fired power units.

不同参数高效超超临界机组经济性分析及建议

本文根据目前大量已投运二次再热机组运行经验,结合某660MW项目高效一次再热和二次再热不同的高效超超临界参数,结合对应的汽机热平衡图参数,通过对THA、80%THA、60%THA三个运行负荷进行了相关的机组经济性参数的计算和对比,通过分析提出了在选择一次再热或二次再热参数上的一些建议和结论。

基于SDAE的超临界机组协调系统特性建模

为采用预测控制方法改善超临界机组的协调控制品质,采用堆叠降噪自编码器(SDAE)建立了单元机组协调系统特性的数学模型。首先,对600MW火电机组的变工况运行数据进行归一化处理,并运用预处理后的数据完成模型的离线训练。将模型并入仿真机进行单一输入变量阶跃扰动和大幅变负荷实验来验证其动态性能。实验结果表明,上述模型能够很好地描述燃料量、汽轮机调门开度、给水量与主蒸汽压力、负荷间的复杂非线性关系,泛化能力强、精度高,可以满足超临界机组智能控制器的设计要求。

P92钢接头Ⅳ型开裂蠕变孔洞临界值的分析及应用

【目的】分析P92管道接头热影响区发生Ⅳ型开裂的蠕变孔洞临界值的影响因素,得到蠕变孔洞临界值计算方法,为评估接头开裂风险提供依据。【方法】收集服役后发生Ⅳ型开裂的P92接头,在未开裂处取样进行610℃下不同应力条件的高温持久蠕变试验,然后使用光学显微镜、电子显微镜观察服役开裂接头和持久断裂接头热影响区的蠕变孔洞分布形貌,并借助图像分析软件测量蠕变孔洞的面积分数,同时使用硬度仪测试热影响区软化情况,最后综合测试结果分析细晶区软化程度和接头应力水平对蠕变孔洞临界值的影响,并拟合应力、显微硬度、孔洞临界值三者之间的函数关系。【结果】研究发现,P92钢接头细晶区相比于接头其它区域软化速度更快,但软化作用并非其发生Ⅳ型开裂的必要条件,当应力水平较高时,细晶区没有发生明显软化时就可以触发蠕变开裂;得到接头轴向应力水平、蠕变孔洞面积分数临界值和显微硬度的函数关系式。【结论】引起Ⅳ型开裂的蠕变孔洞面积分数临界值与相对应力水平(轴向应力与硬度的比值)有关,相对应力水平越高,蠕变孔洞临界值越小,接头安全性就越低;通过测量接头细晶热影响区的蠕变孔洞面积分数和显微硬度,可以估算开裂接头的轴向应力水平,也可以评估在役未开裂接头的Ⅳ型开裂风险。

燃用高硫煤锅炉空预器选型分析

为有效解决2×660MW燃用高硫煤超超临界机组空预器堵塞问题,研究了回转式空预器和管式空预器特性,分析了机组特点,提出了回转式空预器和管式空预器两级换热器串联方案,并探究了该方案对机组锅炉效率的影响。研究表明,相比于常规回转式空预器方案,采用回转式空预器和管式空预器两级换热器串联方案时,回转式空预器的出口排烟温度高于烟气酸露点,有效解决了机组空预器腐蚀堵塞问题,同时在保证设备安全下使锅炉效率提高1%。

基于Q学习的超超临界机组协调系统模型预测控制研究

超超临界机组具有多输入多输出、非线性严重、耦合强、时滞大的特点,其控制系统的设计要求是在保证系统稳定运行的同时,最大限度地提高机组的热效率和功率输出、快速准确地调节机组负荷、确保机组主蒸汽压力和温度在允许范围。通过调整系统模型以及阶段成本,进而获取最优策略。选取强化学习中的Q学习方法。将参数化模型预测控制作为Q学习中的一种新型函数逼近器,通过调整模型预测控制的参数来获取近似最优闭环控制策略以及最优的值函数。将该方法应用到1 GW超超临界锅炉汽轮机协调系统的控制中。在升负荷以及小范围升负荷变化情况下进行仿真。仿真结果表明,与传统模型预测控制方法对比,该方法可以在满足约束的情况下使系统输出值更加准确地到达设定值。

偏置量影响的超超临界汽轮机转子密封动力特性

超超临界汽轮机运行时不平衡的汽流冲击力会引发汽流激振,以某1000MW汽轮机超高压缸隔板迷宫密封为研究对象,采用改进的涡动方程控制转子实现多频涡动,分析了不同偏置量对密封动力特性的影响。结果表明:直接刚度k_(yy)随涡动频率的增加而增加,直接阻尼c_(yy)在30Hz以前先降低后不变。随着压比的增加,有效阻尼增大,转子的稳定性提高。各偏置量下直接刚度k_(yy)朝着正方向增大,c_(yy)随频率的增加先大幅度减小最后近似不变,偏置量引起的密封气动特性变化在高压区域较强。

超超临界机组再热热段疏水管弯头断裂失效分析

为了研究再热热段疏水管弯头断裂的原因,以某火力发电厂1000 MW超超临界机组B侧再热热段疏水管为研究对象,对弯头断裂处及附近位置进行了宏观形貌、金相组织、硬度以及力学性能进行了试验分析,疏水管材质为P92,规格为38.1mm×5mm,工作温度603℃,工作压力4.79 MPa。结果表明:一方面,疏水管温度存在反复变化情况,管壁的膨胀与收缩受到一定程度的约束从而产生热应力循环,疏水管弯头产生疲劳损伤,出现热疲劳裂纹;另一方面,弯头外壁存在凹坑,凹坑处易产生裂纹,同时,弯头位置硬度值超过标准上限,使得弯头抗形变能力降低,在排出凝结水过程中,机组负荷变化和排出凝结水的间歇性致使介质流速发生变化,弯头处振动明显,致使弯头处裂纹进一步发展直至出现断裂。

基于LSTM神经网络算法的超超临界机组负荷优化分配

目前研究的超超临界机组负荷优化分配方法成本较高,分配时间过长,导致节能效果不佳。为此,该文基于LSTM神经网络算法研究了一种新的超超临界机组负荷优化分配方法。利用LSTM中的记忆块、遗忘门、输入门、输出门和记忆单元,实现对递归神经网络的简单处理,建立目标函数,采用正平衡法和反平衡法计算电荷吸收效率,确定超超临界机组负荷优化分配数学模型。针对单元制机组模型和母管制机组模型在忘记阶段、选择记忆阶段与输出阶段进行优化,反复迭代,得到迭代最大次数后停止运行,输出优化结果。实验结果表明,与传统优化方法相比,所设计超超临界机组负荷优化分配方法可将成本降低50%以上,1000 MW内负荷分配时间低于10 min。