Economics of small solar-assisted multiple-effect stack distillation plants

The objective of this paper is to compare the economics of using solar energy to operate small, multiple-effect seawater distillation systems in remote areas with the conventional method of using fossil fuels. The particular multiple-effect system used is an advanced horizontal-tube, falling-film system called “multiple-effect stack” (MES) in which the pumping energy requirement is relatively low compared with the horizontal in-line system. Three system configurations were investigated: (1) a conventional system using a steam generator to provide steam for the MES evaporator and a diesel generator to provide pumping power, (2) a solar-assisted system which uses solar thermal collectors to provide hot water (instead of steam) for the evaporator and a diesel generator for pumping power, and (3) a solar stand-alone system which uses solar thermal collectors for the evaporator heat requirement and a solar PV array to provide electrical energy for pumping. At the present time, solar energy cannot compete favorably with fossil energy, particularly under the present international market prices of crude oil. However, in many remote sunny areas of the world where the real cost of fossil energy can be very high, the use of solar energy can be an attractive alternative. Two important cost parameters affect the relative economics of solar energy vis-à-vis conventional (fossil) energy: the collector cost in dollars per square meter and the cost of diesel oil in dollars per giga Joule. Solar energy becomes more competitive as the local cost of procuring conventional fuel increases and as the collector cost decreases. The water cost from a solar thermal-diesel-MES system (configuration #2) can be seen to approach the water cost from a steam generator-diesel-MES system (configuration #1) when the collector cost drops to $200/m² and diesel oil cost at the remote site reaches $50/GJ. Using a 100% solar system (configuration #3) with solar thermal and solar PV collectors, the economics was seen to improve in favor of the solar system. Even when diesel fuel can be procured at $10/GJ at the remote site, the cost of water from the solar system can be seen to approach that from a conventional plant when thermal collectors costing $200/m² are used. The cost of water from the solar system was shown to be always less than that from a conventional system which uses diesel oil procured at the high price of $50/GJ, but always higher than water produced from a conventional system using diesel oil at the low price of $10/GJ.     

蒸汽冷凝液回收改造总结

针对熔融尿素装置开工运行过程中出现的蒸汽冷凝液外送与确保正常的高压甲铵泵密封水泵进口压力及蒸汽冷凝液贮槽液位控制相互矛盾的问题进行探讨和分析,并提出相应解决方案。方案实施后,达到了确保正常的密封水泵进口压力和有效回收生产系统蒸汽冷凝液的目的。     

考虑水需求的水电联产海水淡化系统的优化设计

水电联产不仅能缓解淡水资源不足的问题,而且可有效降低能耗和淡化成本。建立了水电联产系统数学模型,将优化设计描述为一个混合整数非线性规划(MINLP)问题,并采用混合编码的遗传算法进行求解,结果表明,以水定电模式下水电联产系统最优操作模式为发电、多级闪蒸(MSF)和反渗透(RO)三者的集成,且MSF和RO的产水比存在最优值,发电采用背压式蒸汽轮机。随着淡水需求量的增加,联产系统的淡水成本逐渐降低,MSF与RO的产水比呈现出逐渐降低的趋势。     

Comparison of solar thermal technologies for applications in seawater desalination

This paper deals with a global analysis of the use of solar energy in seawater distillation under Spanish climatic conditions. Static solar technologies as well as one-axis sun tracking were compared. Different temperature ranges of the thermal energy supply required for a desalination process were considered. At each temperature range, suitable solar collectors were compared in some aspects as: (1) fresh water production from a given desalination plant; (2) attainable fresh water production if a heat pump is coupled to the solar desalination system; (3) area of solar collector required for equivalent energy production. Results showed that direct steam generation (DSG) parabolic troughs are a promising technology for solar-assisted seawater desalination.     

汽动给水泵在我公司节能生产中的应用

利用除氧加热蒸汽先驱动给水泵汽轮机做功,给水泵汽轮机的排汽再供除氧器加热脱盐水,可以减少调节阀的节流损失,实现能源梯级利用,减少用电量,提高热电厂的经济效益。给水泵汽轮机采用变速调节,提高了其与给水泵之间的能量转换效率,同时也使锅炉给水系统运行更安全可靠。     

热电联产机组热电解耦技术对比分析

增加热电联产机组运行的灵活性可以提高可再生能源利用率,减小“弃风”和“弃光”率,然而对于灵活性改造技术的对比分析研究相对较少。本文基于Ebsilon建立了600MW案例机组的热力学模型,采用Matlab调用模拟数据构建了该机组的能耗模型。基于此模型对比分析了热泵、电锅炉、蓄热罐及采用汽轮机本体改造等热电解耦技术对机组供热可行域及可行域内机组热力性能的影响规律。研究结果表明,采用热电解耦技术可以扩大机组的供热可行域,当机组热负荷为500MW时,采用热电解耦技术后,机组最小调峰能力由大到小排列为：电锅炉>低压缸光轴运行>低压缸零出力>压缩式热泵>蓄热罐。但电锅炉的能量利用率与?效率在所有热电解耦技术中最低。综合对比分析,在热电联产机组中采用压缩式热泵或热泵与蓄热罐耦合运行是一种节能的热电解耦方式。     

变负荷反渗透海水淡化技术研究

为适应风电、太阳能等新能源的波动性,设计了可变负荷的反渗透(RO)海水淡化装置,用电动阀替代常规浓水调节阀,变频器控制高压泵电机,通过PLC控制变频器的输出频率和电动阀的开度使RO海水淡化的功率可调;利用溶解扩散模型分析了变负荷海水淡化的特性,并通过试验验证了相关结论。在维持膜壳内压力稳定的工况下,低功率运行时可以增加系统回收率,降低单位产水能耗,可以降低运行成本。     

双膜技术在油田污水中的中试试验研究

针对注汽锅炉用水水质要求,采用超滤+反渗透双膜技术对河南油田王集转油站污水处理系统"两级沉降+两级过滤"处理后的污水进行深度处理,通过一个多月的中试连续试运行,结果表明经过双膜技术处理后的污水各项指标均满足进锅炉水质标准。     

某化工项目炼油厂65T/h燃油锅炉改烧水煤浆的运行情况及相关问题的探讨

本文介绍了某化工项目所属炼油厂一台65t/h油炉改烧水煤浆工程改造精况,对厂区煤浆卸、储、运、炉前系统、出渣除尘等进行了介绍,及改造后锅炉运行情况。对运行中出现的相关问题进行了分析探讨。实际应用结果表明,锅炉负荷可达60t/h以上,燃烧效率达到97%以上,锅炉热效率达到88.5%以上,经过整改调试,能够发挥较好的经济效益。     

Optimal operation of RO system with daily variation of freshwater demand and seawater temperature

The optimal operation policy of flexible RO systems is studied in this work. The design and operation of RO process is optimized and controlled considering variations in water demands and changing seawater temperature throughout the day. A storage tank is added to the system layout to provide additional operational flexibility and to ensure the availability of freshwater to customer at all times. A steady state model for the RO process is developed and linked with a dynamic model for the storage tank. The membrane modules are divided into a number of groups to add flexibility in operation to RO network. The total operating cost of the RO process is minimized in order to find the optimal layout and operating variables at discreet time intervals for three design scenarios.     

宽流道反渗透膜耐污染性分析及其在电厂的应用

分析了宽流道反渗透膜的抗污染效果,并结合电厂应用案例,以煤矿井水为原水,对宽流道反渗透膜和混床工艺制备锅炉补给水的实际应用进行验证。结果表明,宽流道反渗透膜表现出较高的耐污染性,用于处理原水水质较为复杂的锅炉补给水的工艺可靠,产水水质满足电厂锅炉补给水的要求。     

Comparison of solar RO and solar thermal desalination systems

In this paper the unit water costs from 100m³/day solar RO and solar distillation plants are compared. RO plants powered by photovoltaic cells are already available, and distillation plants operated from solar collectors are being constructed. For the size chosen and these options it is concluded that distillation is cheaper than RO for salinities above about 6,000ppm.Solar ponds can provide both thermal and electrical energy more cheaply than the above options, but they do not yet have the market penetration of the more accepted systems. If solar ponds are used then distillation is cheaper than RO only for salinities above about 10,000ppm.     

Flow rate distribution in evaporating parallel pipes—modeling and experimental

The motivation for the present work is related to the use of parabolic trough solar power technology for direct steam generation (DSG). So far, commercial plants use liquid oil to absorb heat from the collectors, and steam is produced in heat exchangers. A more efficient process of direct steam generation in the collectors is not used due to possible uneven flow rate distribution and other instabilities, related to liquid-vapor flow in parallel pipes.In this work we present an analysis and experimental results for the flow rate distribution of water flowing and evaporating in two parallel pipes with common inlet and outlet manifolds.A new simplified model that yields the pressure drop versus the flow rate in a single pipe is developed. This model is the basis for the calculation of steady-state solutions, stability analysis and transient simulations in two parallel pipes.Multiple steady-state solutions may be obtained depending on the flow rate and the heating power. Linear stability analysis and transient simulation allow to differentiate between the stable steady states and the unstable ones. It is also shown that when few stable state solutions are possible the one that takes place depends on the history of the inlet flow rate. Experimental results compare well with the theoretical solutions.     

改烧水煤焦浆的燃油锅炉增加吹灰系统的设计研究

水煤焦浆是良好的代油燃料,但含有的灰分使其不能直接应用于现有的燃油锅炉,需要增加除灰装置。通过实验对水煤焦浆燃料灰分的模拟,得出卧式燃油锅炉的积灰主要集中在辐射段和对流段。针对2个区域进行了不同的改造设计,并对吹灰管等设备进行了设计布置,通过现场试验证明效果良好。     

水泥工业纯低温余热发电技术及其效益分析

水泥工业国产化纯低温余热发电技术已基本具备全面推广的条件。对纯低温余热发电系统的设计要因地制宜,总体上可以分为三类:采用单压进汽的凝汽式汽轮机组;利用余热锅炉产生双压蒸汽,配套补汽凝汽式汽轮机组;利用余热锅炉和热水闪蒸技术产生双压蒸汽,配套补汽凝汽式汽轮机组。利用纯低温余热发电技术,采用国产装备,纯低温余热发电系统在建成后2.5～3年内可收回成本。     

FK6F32型调速给水泵推力轴承超温故障诊断及处理

锅炉给水泵组是火力发电机组的重要辅机设备之一,其推力轴承超温故障将增加给水泵跳泵风险,导致锅炉水位波动,严重影响机组的安全运行.通过对高压给水泵平衡装置、叶轮密封环等部件的工作尺寸进行校核计算,得出超温故障成因,并进行针对性处理.