提高高炉干式TRT发电量的创新与实践

莱钢股份银前炼铁5号、6号共两座1080m3高炉设计采用了国家重点推广应用的高炉顶压余压发电节能环保先进技术,安装配备了干式TRT发电机组。投运以来,围绕高炉TRT提高发电量指标,持续开展了高炉与附属TRT装备工艺参数优化,TRT电气设备升级改造,有效地提高了发电量指标水平,为莱钢创造了可观的经济效益,环保效益十分显著。     

高炉提高TRT发电量方法浅谈

通过分析TRT透平机出力、高炉炉顶压力、温度、高压阀组的控制参数、静叶的开度、VS喉口的压差等因素对高炉炉顶煤气余压回收透平发电的影响,找出了TRT能稳定并高发电量的参数。     

全干法布袋除尘在大型高炉煤气除尘系统上的应用

通过对包钢大型高炉除尘系统成功由湿法除尘工艺改造为布袋除尘器的干法除尘工艺案例的监测,从其工作原理、工艺性能和生产运行等方面,分析论述该技术在提高除尘效率的同时,明显提高高炉煤气的出口温度,使TRT发电量大幅增加,是国内高炉首次应用全干法布袋除尘,在保证高炉正常安全运行的情况下,具有很好的节能节水环保效益和经济效益.     

某型TRT机组叶片性能优化设计

某运行高炉煤气余压回收透平发电装置(Blast Furnace Gas Top Pressure Recovery Turbine Unit, TRT)的动叶片是直叶片,机组运行效率不高。在不改变机组进气条件的前提下,通过优化叶型降低流道中的损失,提高TRT涡轮的效率。在给定TRT涡轮通流尺寸的基础上优化动叶片的型线,对原始型线进行三维CFD计算,在原型线的基础上进行优化改进,并针对动叶片的叶身部分做了强度校核计算,优化后机组的总效率提高了1.7%,机组的输出功增加了4.2%。     

单库单向运行潮汐电站发电量最大化计算模型及应用

潮汐电站一直存在资源利用率不高的问题,在电站建设初期当机组选型确定时,制定合理的水库蓄、放水计划,可在不增加投资的前提下获得更多的发电效益。为此,以国内某潮汐电站为例,根据各时刻机组发电流量的不同制定运行方案,基于动态规划法建立了单库单向运行潮汐电站发电量最大化计算模型,并利用龙格库塔算法,结合Matlab软件模拟了各时刻水库水位变化过程,求解了各运行方案的发电量值。计算结果表明,受潮汐水位及机组特性的控制,电站发电量的多少取决于发电流量在各时刻的分配,流量最大运行方案发电量明显大于效率最优运行方案,而发电量最大运行方案流量分配介于效率最优运行和流量最大运行之间。     

风电场微观选址对发电量影响的分析

根据华威风电场风机实际运行监测数据,对比华威风电场12台N62型风机不同方向的发电量、2个场址的平均发电量和同一场址内不同风机的发电量.分析了风电场微观选址对风机发电量的影响.结果表明:4～15号12台风机的单台月发电量差异较大,说明在风电场宏观选址条件相同的情况下,由于微观选址条件的不同,相同型号的风电机组的发电量存在较大的差异;骆驼岭风电场4号风机与风山风电场15号风机正北向发电量的差异较大,地形影响是造成风山发电场发电量较小的主要原因;对凤山风电场内的8～15号8台风电机组进行对比,在各个方向上的发电量差别很大,主要是受到相邻风机间尾流影响所致.     

不同天气类型对光伏电站理论发电量影响的研究

利用浙江某分布式屋顶光伏电站近一年的数据,对不同天气类型下光伏电站的发电特性进行分析。结合当地每日气象数据对天气类型进行分类,分析不同天气类型对光伏电站发电量及发电效率的影响;考虑不同天气类型以及环境温度对太阳电池板的影响,提出一种拟合度较高的理论发电量计算统计模型。最终的模型结果揭示了不同天气类型下,辐射量、温度与发电量之间的耦合关系确实有较大差异,为进一步建立更精确的光伏电站理论发电量模型提供了依据和指导。     

不同纬度下光伏电站阴影的影响与分析

目前光伏阵列支架间距计算均以保证冬至日发电6h为依据,而未考虑各纬度光伏电站不同日照时长情况下因阴影差异导致的发电量损失。故本文首先计算不同纬度、不同日照时长的不可用辐射量及发电量;然后分析因此产生的投资差异;最后计算出各纬度条件下间距计算的参考值。     

哈密东南部风电项目极端气温导致的发电量折减与不确定性分析

本文采用大气模式结合CFD降尺度技术,针对哈密东南部地区某风电项目进行精细化计算,获得多年气象参数的时间序列。通过对温度和风速时间序列的逐年统计,分析风电机组在不同运行温度范围下的发电量折减和不确定性。本文采用的方法可为风电机组设计、选型和项目技术经济评价提供数据基础。     

槽式光热电站连续运行模拟

使用THERMOFLEX软件对100 MW的槽式光热电站进行建模,模拟典型日电站连续运行动态过程。模拟中太阳法向直射辐射(DNI)、地理和气象条件采用某项目的实测参数。模拟结果表明,通过调节导热油的流量、温度、分配以及偏焦系数、热罐液位等主要运行参数,能够保证主蒸汽的温度、压力和流量,实现电站在一定负荷下的平稳运行,并获得了该条件下发电量、厂用电等性能参数。模拟发现,电站在夏至日和冬至日,集热装置接收有效辐射差别很大,随时间变化规律也不同,电站的运行参数的调节方案也存在较大差异。     

基于线热源理论的岩土热响应测试研究现状

地源热泵是可再生能源在建筑物空调中的重要利用形式。岩土热物性是地源热泵地埋管换热器长度设计的主要因素,对于大型埋管系统需要进行热响应测试。回顾了热响应测试的基本原理,介绍了常用的线热源模型及相应的数据处理方法,总结了热响应测试存在的主要问题,并对热响应测试的未来进行了展望。     

Effects of multiple ground layers on thermal response test analysis and ground-source heat pump simulation

A modified three-dimensional finite difference model for the borehole ground heat exchangers of a ground-source heat pump (GSHP) system was developed which accounted for multiple ground layers with different thermal properties in the borefield at no groundwater flow. The present model was used to investigate the impact of ignoring ground layers in the thermal response test (TRT) analysis and the subsequent system simulation. It was found that the adoption of an effective ground thermal conductivity and an effective ground volumetric heat capacity for a multi-layer ground determined from a TRT analysis led to very little error in the simulated long term system performance under various ground compositions investigated. The maximum difference occurred for a 3 × 3 borefield in a dual-layer ground which measured 0.5 °C or 3.9% in the rise of the borefield fluid leaving temperature with a cooling-dominated loading profile for 10 years. With the same borefield and ground composition, a dynamic simulation of the complete GSHP system was performed using the TRNSYS simulation software. It was found that the overall system performance based on the present and the old models differed very little. It was concluded that the assumption of a homogeneous ground in a TRT analysis and subsequent system simulation was appropriate and impact of ignoring ground layers was small. A single-ground-layer model, including the analytical models, was sufficient even for a multi-layer ground. This could reduce the computation time significantly, especially when simulating a large borefield.     

A Modified Entropy Generation Number for Heat Exchangers

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Optimal control of flow in solar collectors for maximum exergy extraction

The best operation strategies for open loop flat-plate solar collector systems are considered. A direct optimal control method (the TOMP algorithm) is implemented. A detailed collector model and realistic meteorological data from both cold and warm seasons are used in applications. The maximum exergetic efficiency is low (usually less than 3%), in good agreement with experimental measurements reported in literature. The optimum mass-flow rate increases near sunrise and sunset and by increasing the fluid inlet temperature. The optimum mass-flow rate is well correlated with global solar irradiance during the warm season. Also, operation at a properly defined constant mass-flow rate may be close to the optimal operation.     

Improved method and case study of thermal response test for borehole heat exchangers of ground source heat pump system

Thermal response test (TRT) is crucial for the determination of the ground thermal conductivity and the evaluation of the thermal performance of borehole heat exchangers (BHEs) of ground source heat pump (GSHP) system. This paper presented a novel constant heating-temperature method (CHTM) for TRT. Further, a type of improved TRT equipment was developed and the mathematical model to deal with test data was presented. Based on the measurement of the natural ground temperature distribution, an in situ TRT case was carried out. The experimental results showed that, compared with the conventional TRT with constant heating-flux method (CHFM), CHTM has an obvious advantage of reducing the time period reaching a steady heat-transfer state between the BHE and its surrounding soils. This improved TRT equipment can effectively operate under both heat-injection and heat-extraction modes, and its test data can accurately reflect the thermal properties of the soils as well as the thermal performance of the BHE under different operation conditions. Finally, the advantages and disadvantages between CHTM and CHFM were compared, which can provide a useful reference for the design of GSHP system.     

Estimation of soil and grout thermal properties through a TSPEP (two-step parameter estimation procedure) applied to TRT (thermal response test) data

In this paper, a versatile TSPEP (two-step parameter estimation procedure) based on a three-dimensional numerical model of a geothermal system is presented. The procedure is applied to both simulated and experimental TRT (thermal response test) data in order to restore the grout and soil thermal conductivities and volumetric heat capacities. The TSPEP is essentially a two-step process. The first step uses the parameter estimation procedure, in the early transient regime to restore the grout thermal conductivity and volumetric heat capacity. The values from the first step are used as the input values in the second step, in which the parameter estimation procedure is applied to the late transient regime to restore the soil thermal conductivity and volumetric heat capacity. Further iterations of these two steps can be used to improve the accuracy of the procedure and are discussed in this paper. The time separation used between the estimation of the soil properties and the estimation of the grout properties partially uncouples the two problems and makes the estimation of these four parameters feasible. A criterion to select the time separation is discussed and validated in this paper.     

Back‐analyses of in‐situ thermal response test (TRT) for evaluating ground thermal conductivity

In this study, a series of computational fluid dynamics (CFD) numerical analyses was performed in order to evaluate the performance of six full‐scale closed‐loop vertical ground heat exchangers constructed in a test bed located in Wonju, South Korea. The high‐density polyethylene pipe, borehole grouting and surrounding ground formation were modeled using FLUENT, a finite‐volume method program, for analyzing the heat transfer process of the system. Two user‐defined functions accounting for the difference in the temperatures of the circulating inflow and outflow fluid and the variation of the surrounding ground temperature with depth were adopted in the FLUENT model. The relevant thermal properties of materials measured in laboratory were used in the numerical analyses to compare the thermal efficiency of various types of the heat exchangers installed in the test bed. The numerical simulations provide verification for the in‐situ thermal response test (TRT) results. The numerical analysis with the ground thermal conductivity of 4.0 W/m?K yielded by the back‐analysis was in better agreement with the in‐situ TRT result than with the ground thermal conductivity of 3.0 W/m?K. From the results of CFD back‐analyses, the effective thermal conductivities estimated from both the in‐situ TRT and numerical analysis are smaller than the ground thermal conductivity (=4.0 W/m?K) that is input in the numerical model because of the intrinsic limitation of the line source model that simplifies a borehole assemblage as an infinitely long line source in the homogeneous material. However, the discrepancy between the ground thermal conductivity and the effective thermal conductivity from the in‐situ TRT decreases when borehole resistance decreases with a new three pipe‐type heat exchanger leads to less thermal interference between the inlet and outlet pipes than the conventional U‐loop type heat exchanger. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of Climate Change on wind speed and its impact on optimal power system expansion planning: The case of Chile

This work assesses the changes in power capacity expansion decisions regarding power generation and transmission that occur when the effects of Climate Change on wind speed are captured in the decision model. Considering an 85-year period (2016–2101), we use a Mixed-Integer Linear Program (MILP) model to analyze the optimal power capacity expansion in diverse types of power generation technologies, throughout the years and geographical locations. The optimization model minimizes the total (investment and operational) costs of the power system subject to several technical and economic constraints. We implement our model using the main Chilean power system. We compare two scenarios: one assuming that Climate Change affects wind speeds and hence wind farm capacity factors and the other assuming it does not. Our results reveal that, when taking into account the impact of Climate Change on wind speed, the optimal power generation and transmission expansion plan is different than when ignoring this effect. The variation of wind speed affects not only wind power capacity installed, but also other-technology power capacity installed. In particular, power capacity installed in wind and solar generation plants is higher (measured in MW installed) than the power capacity installed when we ignore the effects of Climate Change; and power capacity installed in diesel and natural gas technologies are lower. We perform sensitivity analyses, changing power capacity expansion limits and the discount rate, to check for the robustness of our results.     

Generation capacity adequacy in interdependent electricity markets

This paper deals with the practical problems related to long-term security of supply in regional electricity markets with transmission constraints. Differences between regulatory policies and market designs in terms of generation adequacy policies may distort the normal functioning of the neighboring markets, as well as the reliability of supply. We test the effect of heterogeneous regulatory design between two interdependent markets: energy-only market, price-capped market without capacity mechanisms and price-capped markets with forward capacity contracts obligation. We rely on a long-term market simulation model in system dynamics that characterizes expansion decision in a competitive regime. The results show that differences in market designs affect both price and reliability of supply in the two markets. We examine both the short and long terms effect, and how free-riding may occur where capacity adequacy policies are adopted in one market but not the other. The main finding is that the lack of harmonization between local markets in policies to ensure capacity adequacy may lead to undesirable side effects.     

Analysis of a metal hydride reactor for hydrogen storage

In this paper a two-dimensional model of an annular cylindrical reactor filled with metal hydride suitable for hydrogen storage is presented. Comparison of the computed bed temperatures with published experimental data shows a reasonably good agreement except for the initial period. Effects of hydrogen pressure and external fluid temperatures on heat transfer and entropy generation are obtained. Results show that the time required for hydrogen charging and discharging is higher when the thermal capacity of the reactor wall is considered. The time required for absorption and desorption can be reduced significantly by varying the hydrogen gas pressure and external fluid temperatures. However, along with reduction in time the entropy generated during hydrogen storage and discharge increases significantly. Results also show that for the given input conditions, heat transfer between the external fluid and hydride bed is the main source of entropy generation.