Performance test and analysis after high pressure turbine retrofit for Maanshan nuclear power plant Unit 1

The purpose of the performance test for Unit 1 of Maanshan nuclear power plant was to determine the electrical output and heat rate after the retrofit of the high-pressure turbine during the refueling in 2012. The performance test was conducted in order to verify that the actual improvement in electrical output resulting from the replacement of the high-pressure turbine meets the vendor’s guarantee. A total of two performance test runs was conducted in accordance with the American Society of Mechanical Engineers performance test code (PTC) 6. The measured electrical powers for the two test runs were 977.4 and 975.0 MWe, respectively, and the average value was 976.2 MWe. After correcting the electrical power to the rated conditions specified in the performance test procedure, the gross electric output was 983.2 MWe. The corrected heat rate for the two performance tests were 10365 and 10353 kJ/kWh, respectively. The deviation between two corrected heat rates was 0.11%. Since the acceptable deviation between two test runs required by PTC 6 is no more than 0.25%, the quality of test results is acceptable. Moreover, the performance test results also demonstrated that the improvement in gross electrical output was 17.6 MWe, which was higher than the contract guarantee of 10.0 MWe.     

Local boiling heat transfer characteristics of ammonia/water binary mixture in a vertical plate evaporator

The next-generation energy production systems are expected to be based on ocean thermal energy conversion (OTEC) and discharged thermal energy conversion (DTEC). These systems use a plate-type evaporator and ammonia or an ammonia/water mixture as a working fluid. It is important to clarify heat transfer characteristics for designing efficient power generation systems. Measurements of local boiling heat transfer coefficients and visualizations were performed for an ammonia/water mixture (z = 0.9) on a vertical flat plate heat exchanger at a range of mass fluxes (7.5-15 kg m⁻² s⁻¹), heat fluxes (15-23 kW m⁻²), and pressures (0.7-0.9 MPa). The results show that in the case of an ammonia/water mixture, the local heat transfer coefficients increase with an increase in the vapor quality and mass flux and decrease with an increase in the heat flux. The influence of the flow pattern on the local heat transfer coefficient is also observed.     

A framework for the selection of the right nuclear power plant

Civil nuclear reactors are used for the production of electrical energy. In the nuclear industry vendors propose several nuclear reactor designs with a size from 35–45?MWe up to 1600–1700?MWe. The choice of the right design is a multidimensional problem since a utility has to include not only financial factors as levelised cost of electricity (LCOE) and internal rate of return (IRR), but also the so called “external factors” like the required spinning reserve, the impact on local industry and the social acceptability. Therefore it is necessary to balance advantages and disadvantages of each design during the entire life cycle of the plant, usually 40–60 years. In the scientific literature there are several techniques for solving this multidimensional problem. Unfortunately it does not seem possible to apply these methodologies as they are, since the problem is too complex and it is difficult to provide consistent and trustworthy expert judgments. This paper fills the gap, proposing a two-step framework to choosing the best nuclear reactor at the pre-feasibility study phase. The paper shows in detail how to use the methodology, comparing the choice of a small-medium reactor (SMR) with a large reactor (LR), characterised, according to the International Atomic Energy Agency (2006), by an electrical output respectively lower and higher than 700?MWe.     

某2×300MW机组热电厂循环水余热回收技术研究

吸收式热泵式热电厂循环水余热回收技术的节能减排经济效益和社会效益非常巨大。但是,该技术还没有得到全面推广,大多数热电厂没有掌握技术要素,担心循环水余热回收系统故障导致机组循环水中断而造成停机的安全风险,以及投资风险性。笔者从事几个热电厂循环水余热回收项目的技术研究,并成功投入运营,取得巨大的经济和社会效益。本文对吸收热泵式热电厂循环水余热回收技术成功案例进行论述。     

新形势下蓄能蓄电与各种电源的可持续发展

当今水电发展受限于水能资源,在原有基础上再考虑蓄能蓄电可利用电网低谷剩余电能储存转换,变成和再生能源一样,可周而复始更新使用,形成各种电源持续发展的循环机制。蓄能蓄电涵盖抽水蓄能和其他蓄能蓄电设施后,特别有利于节能减排和可再生新能源的发展。今后应关注风险分析、风险设计和风险管理。     

Exergetic analysis and evaluation of coal-fired supercritical thermal power plant and natural gas-fired combined cycle power plant

The present work has been undertaken for energetic and exergetic analysis of coal-fired supercritical thermal power plant and natural gas-fired combined cycle power plant. Comparative analysis has been conducted for the two contestant technologies. The key drivers of energetic and exergetic efficiencies have been studied for each of the major sub-system of two contestant technologies. Overall energetic and exergetic efficiency of coal-fired supercritical thermal power plant are found to be 43.48 and 42.89 %, respectively. Overall energetic and exergetic efficiency of natural gas-fired combined cycle power plant are 54.47 and 53.93 %, respectively. The major energetic power loss has been found in the condenser for coal-fired supercritical thermal power plant. On the other hand, the major energetic power loss has been found in both the condenser and heat recovery steam generator for gas-fired combined cycle thermal power plant. The exergetic analysis shows that boiler field is the main source of exergetic power loss in coal-fired supercritical thermal power plant and combustion chamber in the gas-fired combined cycle thermal power plant. It is concluded that natural gas-fired combined cycle power plant is better from energetic and exergetic efficiency point of view. These results will be useful to all involved in the improvement of the design of the existing and future power plants.     

结合燃气-蒸汽联合循环的液化天然气冷能发电利用

提出了结合燃气-蒸汽联合循环的利用液化天然气（liquefied natural gas,LNG）冷能的朗肯循环发电系统,实现LNG冷能梯级利用。朗肯循环蒸发器和燃气-蒸汽联合循环凝汽器换热量匹配一致,循环水系统实现闭式且不受环境温度影响。对系统进行模拟并分析了影响系统的主要参数,结果显示：随着朗肯循环冷凝温度的降低,朗肯循环净输出功率和净效率均有提升;随着循环水温度的提高,朗肯循环的净输出功率和净效率都将提高,而蒸汽轮机输出功率减少,但二者总的输出功率降低幅度不大。     

Energy Planning for Puerto Rico: A Systems Modeling Approach

This study presents various models for energy planning for the year 2000 in Puerto Rico. Puerto Rico depends on imported oil for 99% of its energy needs. The island has many promising energy sources such as biomass (sugar cane bagasse), photovoltaics (solar energy), ocean thermal energy conversion (OTEC), and wind power systems (WPS). These energy sources present some trade-offs in costs, pollution level, and fuel importation, which are studied. Uncertainty in future demand is taken into account. Integer variables representing the possible electricity generation plants are defined. The best compromise solution using the global criterion method for multiple objectives is presented. The proven alternatives such as coal-steam plants, nuclear plants, and biomass steam plants could have political constraints. New technologies such as photovoltaics, OTEC, and WPS possess many uncertainties. Should the cost of these alternatives be less than the electricity generated using oil, a combination of these energy sources would represent the best alternatives to solve Puerto Rico's electricity needs.     

电站锅炉烟气余热利用技术方案研究

超临界电站锅炉排烟热损失量很大,对锅炉尾部烟气余热进行回收利用可以有效提高电厂的热经济性,减少煤耗,降低环境污染。目前火电厂最广泛提高烟气余热利用效率的方式是加装低温省煤器装置。对某超临界机组锅炉余热利用技术进行研究,分析不同低温省煤器布置方案,提出采用双级低温省煤器回收电站锅炉余热利用技术方案,即采用低温烟气与低加凝结水换热技术、前置式空气预热器与低温省煤器组合的能源梯级利用方式,实现最优节能及最佳投资收益。     

Studies in biogas technology. Part III. Thermal analysis of biogas plants

A thermal model for a conventional biogas plant has been developed in order to understand the heat transfer from the slurry and the gas holder to the surrounding earth and air respectively. The computations have been performed for two conditions : (i) when the slurry is at an ambient temperature of 20°C, and (ii) when it is at 35°C, the optimum temperature for anaerobic fermentation. Under both these conditions, the gas holder is the major “culprit” with regard to heat losses from the biogas plant. The calculations provide an estimate for the heat which has to be supplied by external means to compensate for the net heat losses which occur if the slurry is to be maintained at 35°C. Even if this external supply of heat is realised through (the calorific value of) biogas, there is a net increase in the biogas output, and therefore a net benefit, by operating the plant at 35°C. At this elevated temperature, the cooling effect of adding the influent at ambient temperature is not insignificant. In conclusion, the results of the thermal analysis are used to define a strategy for operating biogas plants at optimum temperatures, or at higher temperatures than the ambient.     

Failure analysis on speed reducer shaft of sluice gate in nuclear power plant

Irradiated fuels of nuclear power plants are usually preserved and cooled in specific water pools containing boric acid solution in nuclear power plants because of residual radioactivity and radiated heat. A sluice gate between two storage pools is used for isolation and connection of irradiated fuels. However, suddenly happened an abnormal fracture of a speed reducer shaft for driving sluice gate in a nuclear power plant with 650 MW capacity in the southern part of China, which could cause potential risk for storage safety of the fuel assemblies. Therefore, comprehensive analysis and investigation on the fractured shaft were carefully carried out in this study. The analysis results revealed that hydrogen embrittlement and temper brittleness induced during carburization and heat treatment were the root causes for the unexpected fracture of the shaft. Countermeasures and recommendations were then proposed and proved effective after implementation.     

凹版印刷工业的绿色节能技术

针对当前凹版印刷设备存在的耗能大、尾气排放污染等问题,通过对凹版印刷机热风干燥系统节能、印刷有机废气(VOCs)综合治理和凹印企业主要热源余热循环利用等主要相关技术的探讨,提出了切实可行的节能减排方案.在此基础上,进一步将热力燃烧式氧化器与热水二段型溴化锂机组相结合,解决了热力燃烧式氧化器运行成本较高的问题.研究结果表明,从热风干燥系统、有机废气综合利用、主要热源余热循环利用3个方面入手实施的节能减排方案,可以降低凹版印刷工业运行能耗的20%~40%.     

锅炉远程水吹灰器更换小口径喷嘴研究

大规模风电并网需要火电机组的灵活调节,在调节能力改造过程中应该保持锅炉的正常运行。为了减少远程水吹灰对锅炉炉膛热负荷的扰动,抑制锅炉本体膨胀,保证输出功率的灵活调节,对锅炉参数进行了研究。某电厂#1、#2锅炉远程水吹灰器流量较大、吹灰过程中对锅炉参数影响较大,通过更换小口径喷嘴,控制了水吹灰器对锅炉参数的扰动。根据试验前后参数对比分析远程水吹灰器更换小口径喷嘴对锅炉不同参数的影响,证明通过更换小口径喷嘴来改造是可行和安全的。     

Role of in-service stress and strain fields on the hydrogen embrittlement of the pressure vessel constituent materials in a pressurized water reactor

The in-service brittle fracture of a structural component of a nuclear power plant (NPP) is a problem of major concern in engineering. During nuclear energy generation, the wall of the nuclear reactor pressure vessel (RPV) is exposed to a hydrogenating environment leading to a fracture phenomenon known as hydrogen embrittlement (HE). This in-service failure is ruled by hydrogen diffusion from the hydrogenating source (the inner side of the RPV) towards certain places inside the vessel where hydrogen is accumulated and microstructural damage is located. The diffusion process is highly influenced by the stress and plastic strain distributions. For achieving a realistic estimation of the hydrogen accumulation by diffusion, both the in-service thermal stress and the manufacturing induced residual stress and strain (due to tempering heat treatment) must be taken into account. In this paper, a numerical analysis of the hydrogen diffusion assisted by stress and strain is carried out to find out the hydrogen accumulation within the wall of a real pressurized water reactor (PWR) for diverse heat treatment conditions. Results reveal the key role of the in-service thermal stress which enhances the hydrogen diffusion through the constituents' materials of a PWR pressure vessel.     

Ash deposit characterisation in a large-scale municipal waste-to-energy incineration plant

The deposition of ash - combustion residues - on superheaters and heat exchanger surfaces reduce their efficiency; this phenomenon was investigated for a large-scale waste-to-energy incineration facility. Over a period of six months, ash samples were collected from the plant, which included the bottom ash and deposits from the superheater, as well as flyash from the convective heat exchanger, the economiser and fabric filters. These were analysed for particle size, unburned carbon, elemental composition and surface morphology. Element partitioning was evident in the different combustion residues, as volatile metals, such as cadmium, antimony and arsenic, were found to be depleted in the bottom ash by the high combustion temperatures (1000+°C) and concentrated/enriched in the fabric filter ash (transferred by evaporation). Non-volatile elements by contrast were distributed equally in all locations (transported by particle entrainment). The heat exchanger deposits and fabric filter ash had elevated levels of alkali metals. 82% of flyash particles from the fabric filter were in the submicron range.     

Characterisation of radioactive waste products associated with plant decommissioning

The inventory of radioactivity that must be considered in the decommissioning of a typical 1000 MWe Spanish pressurised water reactor (PWR) was investigated as part of a generic plant decommissioning study. Analyses based on DORT models (in both R-Z and R-theta geometries) were used with representative plant operating history and core power distribution data in defining the expected neutron environment in regions near the reactor core. The activation analyses were performed by multiplying the DORT scalar fluxes by energy-dependent reaction cross sections (based on ENDF/B-VI data) to generate reaction rates on a per atom basis. The results from the ORIGEN2 computer code were also used for determining the activities associated with certain nuclides where multi-group cross section data were not available. In addition to the bulk material activation of equipment and structures near the reactor, the activated corrosion-product (or 'crud') deposits on system and equipment surfaces were considered. The projected activities associated with these sources were primarily based on plant data and experience from operating PWR plants.     

Techno-economic performance evaluation of a direct biomass-fired combined cycle plant employing air turbine

Techno-economic performance analysis of a biomass-fired combined cycle plant, employing a topping air turbine (AT) cycle and a bottoming steam turbine cycle, is reported in this paper. The net power output is 500 kWe, the AT producing 350 kWe and the ST producing the rest. Biomass (saw dust) is directly fired in a biomass combustor-heat exchanger (BCHX) duplex unit which supplies heat to the topping cycle. Influences of major plant parameters on the thermo-economic performance of the plant are analysed. Overall efficiency is found to maximise at topping cycle pressure ratio of 4. Higher TIT results in better energetic performance, while higher hot end temperature difference of the BCHX unit lowers the plant efficiency. Thermo-economic analysis reveals that the lowest unit cost of electricity (UCOE) of about 0.12 $/kWh could be achieved for the plant, while still giving an overall efficiency of about 48 %. Based on minimum UCOE, the payback period is estimated to be about 6 years with 50 % capital subsidy and about 13 years with no capital subsidy.     

空气源热泵耦合太阳能及余热用于升压站供暖的研究

风电场、光伏发电站等工程的升压站,一般远离集中热源,冬季多采用“电暖气+热水器”的传统方案,能源利用效率低,增加了电能消耗,降低了项目收益。提出“空气源热泵耦合太阳能及余热”的供暖方案,为升压站提供了可靠的热源,并提高了能源利用效率,降低了运行费用。升压站内电气设备间有大量的40℃左右的排风,可以作为空气源热泵的低温热源,解决了空气源热泵低温时效率低的弊病;空气源热泵生产出热水,并设置太阳能热水器进一步提高水温满足供暖要求;设置单独的蓄热水箱适应供暖负荷变化并解决一部分生活热水需求。以北京某风电场工程为例,阐述了这一系统的优缺点以及推广的必要性和可行性。分析表明,在最冷时该系统仍可以高效、稳定的运行,投资回收期短,为寒冷地区空气源热泵的应用提供了参考依据。     

过冷度对地热发电非共沸工质有机朗肯循环热力性能的影响

有机朗肯循环（organic Rankine cycle,ORC）是利用中低温地热能（< 150℃）发电的主要途径,在实际运行中,非共沸工质往往会冷凝至过冷状态。分析了冷凝过冷度对非共沸工质ORC热力性能的影响,建立了ORC、内回热（internal heat exchanger,IHE）ORC的热力学模型,以净输出功最大为目标函数优化了工质的蒸发压力,并开展了系统的㶲分析。结果表明：过冷度影响了工质与冷源换热流体间的温度匹配特性,受夹点温差的限制,随着过冷度的增加,工质的冷凝压力上升;过冷度亦改变了预热器和蒸发器的热量分摊,随着过冷度的增加,最佳蒸发压力亦上升。混合工质异丁烷/异戊烷的质量配比为0.4：0.6时,净输出功受过冷度的影响最大,当过冷度为2℃时,净输出功下降了4.36%。IHE回收膨胀机排汽的余热,提高了预热器入口温度,可提高过冷ORC系统净输出功0.55%。过冷度增大了冷凝器的㶲损失;采用内回热冷凝器的㶲损失降低了24.7%。     

一种新型跨临界CO2冷电联供系统热力分析

提出一种新型跨临界二氧化碳（trans-critical carbon dioxide,TCO₂）再压缩循环和喷射器制冷循环耦合的冷电联供系统。该系统在输出电能的同时,利用低品位热能驱动喷射器工作输出冷量。以输出电量1 MW为设计目标,对比冷电联供系统和再压缩发电系统的性能,研究联供系统各部件（火用）损和主要热力参数对其性能的影响。结果表明：联供系统利用CO₂余热驱动喷射器输出冷量,循环热效率高于单一再压缩系统;加热器（火用）损所占比例最大,回热器次之;透平进口温度、压力和背压对联供系统工质流量、循环效率、输出功率、加热器功率、压缩机耗功及喷射器制冷量等参数影响较大;而冷凝温度和蒸发温度仅对制冷循环制冷量影响较大。在设定条件下,联供系统的循环热效率和（火用）效率可分别达到46.99%和47.21%。