Ro, MSF and VTE/VC desalination: a comparative evaluation

The two main processes currently in vogue, for sea -water desalination 3?-- multistage flash. (MSF) and reverse osmosis (R.O.) -- are compared, on the basis of cost economics. Cost data are reported for unit sizes up to 10 million (U.S.) gallons per day. Both single-pass and double-pass systems are considered for the R. 0. unit, while the cost of water from MSF plants is calculated for different performance ratios. Controlling factors such. as fuel prices, pretreatment costs, membrane life, energy recovery and terms of financing, are discussed.On the basis of present technology, notwithstanding new developments, it is concluded that R. 0. is the more economical of the two for small unit sizes and regions of high fuel costs. There is a break-even point, depending on these two parameters, beyond which the MSF process yields lower water costs.Attention is focussed on a third process —- Vertical Tube Evaporation/Vapor Compression (VTE/VC), a self-contained, low-energy consuming system which is particularly suitable for barge-mounted or land-based single- purpose (water only) installations. The process, -which, is in an advanced stage of development under Envirogenics Systems Company's R and D program, is potentially competitive with R.O , even for small unit sizes. Future improvements and operational experience could make this the process of choice for single-purpose sea water desalination plants.     

反渗透海水淡化中差动式能量回收装置的研究

研究了一种应用于中小型反渗透海水淡化装置的新型差动式能量回收装置.结果表明,使用本能量回收装置的日产10m3反渗透海水淡化装置的单位淡水能耗只有3.6kWh/m^3,不考虑高压泵及电机自身损耗的影响时,单位淡水能耗为2.3～2.7kWh/m^3,装置能耗显著降低,能量回收效率达到97%.此能量回收装置不需要其它附加增压设备,并且能有效改进由于阀门开闭导致系统压力波动而造成的淡水产量不稳定的问题,保护了反渗透膜、高压泵等系统内的重要设备.     

Kreiselpumpen und Energierückgewinnungs-Turbinen in der verfahrenstechnischen Hochdrucktechnik

Centrifugal pumps and energy recovery turbines in high pressure industrial process engineering . Centrifugal pumps have to meet many different requirements in high pressure industrial process engineering. International standards call for minimum requirements and propose solutions for various problems. Nevertheless, options remain for the operator with regard to the choice of the casing, material, and sealing variants, and to the choice of hydraulics to meet such requirements as reliability, safety, service-friendliness, economic efficiency, and investment cost. The following review presents various designs of centrifugal pumps for high pressure industrial process engineering. Furthermore, the installation of high pressure pumps in turbine operation for energy recovery is introduced.     

HRS在硫磺制酸中的应用

重点介绍 HRS 的工艺原理、特点、主要设备及在中国 2 套硫磺制酸装置上的应用情况.HRS 用 HRS 热回收塔取代传统工艺的吸收塔,用 HRS 锅炉取代传统工艺的吸收塔酸冷却器,从而使硫酸装置的总能量回收率从传统装置的 70% 提高到 93%,同时减少了循环冷却水消耗,其经济效益、环境效益显著.     

Optimal Design of Membrane-Hybrid Systems for Waste Reduction

Abstract

A systematic procedure is devised to tackle the design of membrane-hybrid systems for waste reduction. A membrane-hybrid system corresponds to any separation network that employs reverse-osmosis modules, booster pumps, turbines and mass exchangers (e.g. extractors, adsorption columns, ion exchangers, etc.). The proposed approach provides a generally-applicable framework for simultaneously screening all potential separation processes of interest. The problem is formulated as an optimal synthesis task. The solution to this task provides the minimum-cost hybrid configuration, types and sizes of reverse-osmosis units, mass exchangers, pumps and turbines. It also identifies the best distribution of streams and waste reduction loads. A case study is tackled to illustrate the applicability of the devised procedure.     

Optimization analysis of dual-purpose systems

This paper aims to analyze dual-purpose systems focusing the total cost optimization; a superstructure is proposed to present cogeneration systems and desalination technologies alternatives for the synthesis process. The superstructure consists of excluding components, gas turbines or conventional steam generators with excluding alternatives of supplying fuel for each combustion system. Also, backpressure or condensing/extraction steam turbine for supplying process steam could be selected. Finally one desalination unit chosen between electrically-driven or steam-driven reverse osmosis, multi-effect and multistage flash should be included. The analysis herein performed is based on energy and mass conservation equations, as well as the technological limiting equation of equipment. The results for ten different commercial gas turbines revealed that electrically-driven reverse osmosis was always chosen together with both natural gas and gasified biomass gas turbines.     

甲醇生产系统中汽轮机拖动压缩机工艺的技改效果分析

介绍了甲醇生产系统中2种汽轮机拖动压缩机的工艺流程和设备技术参数;对比了2种汽轮机技术改造方案和工艺技术特点;对汽轮机的改造投资、动力消耗、生产运行状况和经济效益进行了分析。运行效果表明:以蒸汽作为动力进行汽轮机拖动压缩机的改造宜采用背压式汽轮机,背压式汽轮机替代电动机拖动压缩机每年可节约生产费用356.8万元。     

化工设备维修技能提高的办法

常见化工设备包括:离心机、压缩机、风机、汽轮机、各种泵、换热器、塔等。现代化工设备越来越复杂化、精密化,越来越需要维修钳工更高的维修技能,我们只有在多次维修实践中不断总结经验教训,才能满足现代化工设备对维修技能的需求。     

Power scheduling and real-time optimization of industrial cogeneration plants

Scheduling of power and real-time optimization for three industrial cogeneration plants at one of Dow's Louisiana site is presented in this paper. A first principle mathematical model that includes mass and energy balances for gas turbines, heat recovery units, steam turbines, pressure relief valves and steam headers is used to formulate an optimization problem to recommend the best strategy to trade power. The model has detailed operational information that includes equipment status and control curves for different operating scenarios. The model can also accurately predict the effect of ambient temperature, thereby resulting in an optimal day-ahead schedule. Adjustment of power schedule is done in the real-time market 30 min prior to the hour and implementation of the dispatched power schedule is done using a model predictive controller.     

Distillation and reverse osmosis energy consumption and costs

The paper compares the energy requirements of single and dual purpose MSF distillation with seawater reverse osmosis plant. Energy consumptions are given both as heat and power consumptions for distillation and as power consumption for R.O. To enable a true comparison to be made these inputs are referred back to the heat inputs from fuel needed at the boiler plant or appropriate thermal power plant.Energy recovery is also considered for reverse osmosis and it is shown that the energy input can be expected to decrease by some 35% for a typical example.Although the prime energy input needed for reverse osmosis is shown to be substantially lower than for dual purpose distillation, the overall costs taking account Of capital charges, energy, replacements and other operating costs, are found to be in a band width of about 5% for plants in the range of 5000 to 15000 m³/day. Reverse osmosis plant water costs are significantly less than distillation if membrane life increases from 3 years to 5 years, particularly with small plant capacities.     

Professor Joseph W. McCutchan, 1918-1982

The paper compares the energy requirements of single and dual purpose MSF distillation with seawater reverse osmosis plant. Energy consumptions are given both as heat and power consumptions for distillation and as power consumption for R.O. To enable a true comparison to be made these inputs are referred back to the heat inputs from fuel needed at the boiler plant or appropriate thermal power plant.Energy recovery is also considered for reverse osmosis and it is shown that the energy input can be expected to decrease by some 35% for a typical example.Although the prime energy input needed for reverse osmosis is shown to be substantially lower than for dual purpose distillation, the overall costs taking account Of capital charges, energy, replacements and other operating costs, are found to be in a band width of about 5% for plants in the range of 5000 to 15000 m³/day. Reverse osmosis plant water costs are significantly less than distillation if membrane life increases from 3 years to 5 years, particularly with small plant capacities.     

Transporting slurry for the production of seawater magnesia

Conclusions Hydrated magnesium oxide slurry produced from vacuum filters is unsatisfactorily handled by transportation with belt conveyers and augers.By mechanical blending the slurry into a constant volume it can be transmitted in the homogeneous liquid state, and in this form can be pumped with a gear pump.The expansion of the production of magnesium oxide from brine makes it necessary to use pumping equipment with a capacity of 30–40 m/h. Therefore it is necessary to continue research work in this direction for the design of pumps of the necessary output.Translated from Ogneupory, No. 3, pp. 24–27, March, 1969.     

Operating experience of the Dhekelia seawater desalination plant using an innovative energy recovery system

Dhekelia Desalination Plant in Cyprus has been in operation for 7 years. It includes eight 5,000 m³/d seawaterreverse osmosis trains operating with Mediterranean seawater with a TDS content of 41,800 ppm, with water temperature ranging from 17°C to 32°C. The energy recovery system originally installed at the plant is the Francis turbine, which, at the time, was considered one of the most efficient and economical devices on the market. Since then, however, market forces to reduce operational costs, by cutting down energy consumption, led to the advent of new energy recovery systems. Today several systems are in operation which reduce the RO energy consumption. Apart from the versions of the Francis turbine and Pelton wheel they include the hydraulic turbocharger, work exchanger and pressure exchanger, all harnessing the pressure energy of the brine. In our effort to be competitive for the years to come we decided to convert our existing energy recovery system from Francis turbines to the pressure exchanger. This paper outlines how it was decided to go ahead with the pressure exchangers, and gives comparisons with other energy recovery methods, and describes our operating experience with the pressure exchangers.     

Polymerwerkstoffe im Chemie-Apparatebau

Polymer materials in chemical plant equipment. The range and technical sophistication of organic materials today provide the chemical industry in particular with economical and highly dependable materials able to fulfill functions which previously required the use of expensive metals. Polymer materials suitable for use in chemical plant equipment can basically be subdivided into thermoplastics, elastomers, thermosets, and composites. They are used in the form of solid structures or as protective coatings. Recent years have seen a marked increase in the importance of self-vulcanizing rubber linings for on-site application (e.g. in sewage treatment and flue gas desulphurization plants), composite structures based on fluorinated polymers for acid recovery and electrically conducting polymers for the transportation of corrosive, combustible gases and vapours.     

Waste heat powered reverse osmosis plants

The purchased power required for operation of reverse osmosis systems can be greatly reduced or sometimes eliminated by reclaiming waste heat from diesel engines, gas turbines, flare gases, etc. This can be accomplished by using a Biphase turbine to convert low level waste heat to shaft horsepower.The system can be designed to use waste heat from existing installations or to reduce the size of the generating equipment in new supplies.The Biphase conservation turbine is driven by a two phase stream generated by flashing a superheated liquid through a nozzle to the turbine. The turbine can be directly coupled to a pump shaft, to an electrical generator or to a combination of the two. Performance of the turbine is discussed. The waste heat recovery turbine and a hydraulic turbine to recover energy from the high pressure concentrated brine can be combined into one system.This paper describes the design of a seawater reverse osmosis system using waste heat from an existing diesel generating unit. The SeaRO system is designed to produce 750 cmd of 400 ppm water at an energy consumption of approximately 2.5 KWH of purchased power per cubic meter.A discussion of available desalination capacity at various quantities and temperature levels of the waste heat source is presented. A comparison of water costs obtained using this system and a conventional electrical drive is presented.     

Energy considerations

A general survey is given on possibilities for energy conservation in an oil refinery with special consideration given to palm oils and coconut oil. Some selected areas are discussed more in detail: heat conservation by means of regenerative heat exchangers, optimization of vacuum equipment for deodorization etc. and use of heat pumps. Some examples are given to illustrate possible savings and payback time for installation of energy saving equipment.     

偏三甲苯装置的节能技术改造

介绍了偏三甲苯装置改造前工艺流程、设备、产品质量、产品收率及运行情况,并运用化工过程模拟软件Aspen Plus,讨论了通过技术改造降低装置能耗的可行性。通过运用热集成精馏工艺、增加真空泵和换热器、塔盘换填料等措施,优化生产流程和操作参数,进行技术改造,生产实践表明,改造后装置运行平稳,能有效地降低装置的能量消耗,并提高了偏三甲苯产品的质量和收率,对同类装置设计有借鉴作用。     

Hydraulic turbine energy recovery - R.O. System

In reverse osmosis desalination plants large flow rates of concentrated brine are discharged at high pressure from the membrane modules. Currently this pressure energy is wasted. This paper reviews the impact of soaring energy costs on the technical alternative of hydraulic turbine energy recovery. The capital costs, operating costs, and economics in electrical energy are evaluated for both sea-water and brackish water systems. Schemes of hydraulic turbine coupled with electric generator, tied to the electric power supply are considered for various plant sizes from 1 to 10 mgd. The analysis, in parametric form, presents the interrelationships between the cost of money, cost of electrical energy, and recovery factors for the different plant sizes and for sea-water and brackish water systems. The results will serve as a guide to determine when such a power recovery system should be seriously considered and evaluated in greater details for specific applications.     

高背压汽轮机拖动锅炉给水泵在尿素厂的技术应用

在日常生产过程中,部分尿素企业使用减温减压器来实现高温高压蒸汽减温减压至中温中压使用,针对这一现象,分析了此过程中能量的损失,采取了高背压汽轮机替代减温减压器、拖动锅炉给水泵的措施,实践表明,本次节能改造节约了成本,在能源的梯度利用中效果显著。