Analysis of water production costs of a nuclear desalination plant with a nuclear heating reactor coupled with MED processes

A nuclear heating reactor (NHR) was designed with the required inherent safety and simplified design features. Power capacity of the NHR-200 (200 MW(th), with steam production of 380 t/h) is compatible with reasonably sized desalination plants. Thermal-hydraulic parameters of the produced steam (2.4 bar and 124°C) are suitable for coupling with distillation processes. Economic competitiveness of the NHR desalination plant is the key point to which the public and decision-makers are paying good deal of attention. Coupling of the NHR with selected MED processes and design parameters of an integrated desalination plant are described. Results of analyses of water production costs are presented as well. Based on the economic evaluation, the average energy cost of the nuclear plant may reach 5.44 $/t of steam, and the provided water production cost may reach 0.72 $/m³ and 0.76 $/m³ for coupling with HT–VTE–MED and LT–HTE–MED processes, respectively.     

Reverse osmosis to achieve water control and recycle

A 648,000 GPD reverse osmosis (RO) facility at ERDA's Rocky Flats Plant near Golden, Colorado will convert tertiary sewage plant effluent for recycle as cooling tower makeup to reduce external water demand and achieve “zero discharge” off-site of tertiary sewage effluent.

Design parameters for the facility, determined by three years of pilot plant testing, include 98% feedwater recovery, 100 ppm T.D.S. product water, and minimum brine production for evaporation to dryness.

Pretreatment consists of RO feed attenuation in a large pond, chlorination, sand filtration, softening, diatomaceous earth filtration, feed-water heating and pH adjustment. The RO plant will have three 150 GPM trains, each with a combination of HFF modules producing about 90% of the permeate, followed by SW modules producing the final 10%. Permeate from the SW modules can be combined with permeate from the HFF modules or returned to the RO feed stream.

Unique design considerations include heating the 40–70°F fee to 77°F by means of heat recovery from the permeate and supplemental steam heating, recycling of pretreatment backwash streams wherever possible to reduce the volume of brine, and precautions to avoid silica scaling of the modules.     

Integration of seawater desalination with power generation

The economic benefits of integrating seawater desalination with power plants are discussed, starting from the first principles of thermodynamics. The concepts of the “fuel-use performance ratio” and the “power loss” method are described in the context of their usage for thermal cycle evaluation and desalination process selection, both with conventional steam cycles and with combined cycle power plants. A thermo-economic model is introduced to evaluate water and power costs and rates of return in dual-purpose power/desalination applications. The future of integrated power and desalination plants is discussed with reference to the growing role of seawater reverse osmosis (SWRO) in the desalination arena. A case study is presented to evaluate the benefits of integrating SWRO with existing power/desalination plants in the Middle East. Subject to the assumptions of the study, it is concluded that repowering and retrofitting would result in a nearly three-fold increase in the power generating capacity and an over six-fold increase in the water output, without requiring any expansion of the seawater intake system. Based on natural gas fuel, the repowered plant would also result in a 70% increase in the fuel efficiency of the station and a drastic reduction in the cost of water production. For a privatization scenario, an economic analysis is used to show that attractive rates of return would be obtained if a developer were to purchase and refurbish the existing plant, selling the products on a build own and operate (BOO) basis. In preparation for this promising application, the need for pilot plant testing at existing power/desalination stations, together with research and development work in membrane technology for high temperature operation, is emphasized.     

On the reduction of desalting energy and its cost in Kuwait

All seawater desalting processes, multi-stage flash (MSF), multi-effect boiling (MEB), mechanical vapor compression (MVC) and seawater reverse osmosis (SWRO) consume significant amounts of energy. The recent increase of fuel oil cost raises the cost of energy consumed for desalting water and the final water cost, and creates more interest in using more energy efficient desalting systems.

The most used desalting systems by distillation (MSF and MEB) are usually combined with power plants in what is called co-generation power desalting plants, CPDP. Fuel is supplied to the CPDP to produce both desalted water D and power W, and the fuel cost is shared between D and W. Exergy analysis and equivalent work are among the methods used to determine the fuel energy charged to each product. When desalting systems, such as SWRO and MVC, are not combined with a power plant, the fuel energy can be directly determined from its electrical power consumption.

In this paper, the fuel energy cost charged to desalting seawater in the presently used CPDP in Kuwait is calculated based on exergy analysis. The MSF, known by its high energy consumption, is the only desalting method used in Kuwait. The MSF units consume 258 kJ/kg thermal energy by steam supplied to the brine heater BH, 16 kJ/kg by steam supplied to steam ejectors, and 4 kWh/m3 mechanical energy for pumping. These MSF units are operated either by:

(1) Steam extracted from extraction/condensing steam turbines EC/ST as in as in Doha West, Azzour, and Sabbiya CPDP. This practice is used in most Gulf area.

(2) Steam supplied directly from boilers as occurred in single purpose desalting plants as Al Shuwaikh plant; or in winter time when no steam turbines are in operation in the CPDP to supply steam to the desalting units.

The CPDP have limited water to power production ratio. While they can cope with the increase of power demand, it cannot satisfy the water demand, which is increasing with higher pace than the power demand.

The case of steam CPDP used in Kuwait is presented in this paper as a reference plant to evaluate the amount of fuel energy consumed to desalt water in MJ/m3, its cost in $/m3. The resulted high fuel cost calls for some modifications in the reference CPDP to lower the energy cost, and to increase its water to power ratio. The modifications include the use of an auxiliary back-pressure steam turbine ABPST supplied with the steam presently extracted to the MSF units. The power output of the ABPST operates MVC or SWRO desalting units; while the ABPST discharged steam operates LT-MEB desalting unit. The desalting fuel energy costs when applying these modifications are also calculated by the exergy analysis and compared with that present situation.

It is also suggested to increase desalted water output by using separate SWRO desalting units operated by the existing power plants of typical η_c = 0.388, or by new combined gas/steam turbines power cycle GT/ST-CC of typical η_c = 0.54 under construction. The SWRO with energy recovery is assumed to consume typical 5.2 kWh/m³ electric energy.     

蒸汽—电联合动力在水泥厂余热利用中 的分析与实践

针对许多熟料生产线的剩余余热蒸汽,设计了蒸汽—电联合动力方式,通过工业汽轮机与电动机联轴运行,实施水泥厂大型转动设备的蒸汽—电联合动力。实现了以较低的成本,扩展水泥厂余热蒸汽的利用范围,降低熟料生产线的用电量。论文对比分析余热发电与蒸汽—电联合动力的效率,结果表明,蒸汽—电联合动力有更高的效费比,更低的投资与运行费用。     

A study of the deactivation by sulfur and regeneration of a model NSR Pt/Ba/Al2O3 catalyst

The deactivation by sulfur and regeneration of a model Pt/Ba/Al₂O₃ NO_x trap catalyst is studied by hydrogen temperature programmed reduction (TPR), X-ray diffraction (XRD), and NO_x storage capacity measurements. The TPR profile of the sulfated catalyst in lean conditions at 400 °C reveals three main peaks corresponding to aluminum sulfates (550 °C), “surface” barium sulfates (650 °C) and “bulk” barium sulfates (750 °C). Platinum plays a role in the reduction of the two former types of sulfates while the reduction of “bulk” barium sulfates is not influenced by the metallic phase. The thermal treatment of the sulfated catalyst in oxidizing conditions until 800 °C leads to a stabilization of sulfates which become less reducible. Stable barium sulfides are formed during the regeneration under hydrogen at 800 °C. However, the presence of carbon dioxide and water in the rich mixture allows eliminating more or less sulfides and sulfates, depending on the temperature and time. The regeneration in the former mixture at 650 °C leads to the total recovery of the NO_x storage capacity even if “bulk” barium sulfates are still present on the catalyst.     

工业汽轮机的经济出力分界点

在石化企业蒸汽动力系统中存在大量的减温减压器,将较高压力蒸汽转化为较低压力蒸汽以适用于不同品位热量的需求。此外在夏季企业可能存在低压蒸汽过剩现象。采用背压汽轮机替代减温减压器和凝汽汽轮机回收过剩低压蒸汽能量是节能的有效方法。为了确定采用汽轮机的经济合理的范围,通过经济评价方程,获得了背压汽轮机和凝汽汽轮机的经济出力分界点,并讨论了在不同蒸汽价格或电热比价下该分界点的变化。案例结果表明,该临界值所对应的功率较小,表明在企业多数情况采用汽轮机的节能方案是经济可行的。本文可为在石化企业的节能减排中采用工业汽轮机提供指导和依据。     

An investigation of high operating temperatures in mechanical vapor-compression desalination

It is common practice to operate mechanical vapor-compression (MVC) seawater desalination systems at temperatures lower than 80°C. This study presents the detail engineering and economics of a MVC system operating at 172°C. The literature indicates that high overall heat transfer coefficients for the evaporator are possible at high temperatures with dropwise condensation on the steam side and pool boiling on the liquid side. Employing high operating temperature delivers the following advantages: (1) low compression work, (2) small latent heat transfer area, and (3) small compressor. These advantages potentially reduce operating costs and capital investment. The disadvantages follow: (1) pretreatment required to prevent fouling of heat exchangers, (2) careful selection of materials to prevent corrosion, and (3) larger sensible heat transfer area is required. A desalination plant is designed herein to produce 37,854 m³/d (10 mil gal/day), which is financed with a 5%, 30-y municipal bond. To maximize energy efficiency, combined-cycle cogeneration is employed. For the US ($5.00/GJ energy), the product water selling price is estimated to be $0.49/m³ ($1.86/thous gal). For the Middle East ($0.50/GJ energy) the product water selling price is estimated to be $0.38/m³ ($1.44/thous gal). These are attractive prices relative to competing technologies.     

In situ EXAFS study of the nucleation and crystal growth of Ni particles on SiO2 support

Ni/SiO₂ catalysts were prepared by wetness impregnation method (INi) and by a new two-step method (ENien_2.5/600+INi_2.5). The two-step method consists of formation of chemical glue, “nickel nuclei”, having strong metal support interaction with SiO₂ and preparation of the “nickel reservoir” which has weak interaction with support. The nucleation and growth behaviors of such Ni/SiO₂ catalysts in the preparation stage were continuously monitored by in situ EXAFS spectroscopy. The in situ EXAFS spectra of INi catalyst began to change after 320°C and bulk NiO like structure was formed at 500°C heat treatment. The Ni/SiO₂ prepared with the two-step method had larger coordination number of Ni with silica support in the initial stage of in situ monitoring than that of INi catalyst, which showed the coexistence of Ni nuclei and Ni reservoir. The ENien_2.5/600+INi_2.5 had smaller particles of Ni compared with INi after high temperature calcination. The formation of small Ni particles could be attributed to the strong ion-support interaction of nickel nuclei with nickel reservoir in ENien_2.5/600+INi_2.5 catalyst. Slight particle growth occurred after 370°C calcination in Ni/SiO₂ prepared by two-step method.     

Reverse osmosis desalination plants — marine environmentalist regulator point of view

The environmental characteristics of the brine and its impacts on the marine environment were always the “backyard” and the less concern while planning and operating RO desalination plants. The lack of drinking water in Israel made desalination a national goal. The first huge RO plant was initially operated in Israel on 2005 — 100 Mm³/y and by the end of 2010 305 Mm³/y potable water expected to be produced. Construction and installation of desalination plants requires applying suitable environmental solutions for protecting and preserving the marine and coastal environment from ruin or deterioration.

The Israeli environmental legislation is described including the marine environmental policy and regulations as well as the acquired operational experience during the last two years. Results from the first year of operation and monitoring are shown along with the new appearance of the red phenomenon discharge of VID desalination plant in Ashkelon.

The environmental policy based on the precautionary principle is performed and includes environmental requirements and guidelines for pretreatment, discharge composition, planning marine outfall, background and compliance marine monitoring program and discharge quality standards.     

Energetic aspects of the fouling of MSF desalination plants with and without the use of on load ball cleaning system

Multi-stage flash (MSF) desalination plants are designed with specific permissible fouling factors. When these conditions are met, the performance is said to “meet design”.With single- purpose desalinators, fouling of the brine heater can be compensated for by increasing the steam pressure without substantial increase of heat consumption and within the limits of the boiler pressure. With dual-purpose desalinators, the brine heater pressure will influence the efficiency of the turbine process.Fouling of the heat recovery section increases the heat consumption of the MSF process. The distillate production can be maintained within the limits of the boiler.Typical “design fouling factors” have been compiled from literature.The influence of fouling factor on specific heat consumption has been calculated for typical MSF design conceptions, as well as the increase of water costs per m³ with different fuel prices.The costs of various scale prevention methods have been evaluated. The effectiveness of such countermeasures can be quantified by plant experience.This analysis of cost/return gives a basis for a correct economic comparison.     

Ceria-based oxides as supports for LaCoO3 perovskite; catalysts for total oxidation of VOC

Supported LaCoO₃ perovskites with 10 and 20 wt.% loading were obtained by wet impregnation of different Ce_1−xZr_xO₂ (x = 0–0.3) supports with a solution prepared from La and Co nitrates, and citric acid. Supports were also prepared using the “citrate method”. All materials were calcined at 700 °C for 6 h and investigated by N₂ adsorption at −196 °C, XRD and XPS. XRD patterns and XPS measurements evidenced the formation of a pure perovskite phase, preferentially accumulated at the outer surface. These materials were comparatively tested in benzene and toluene total oxidation in the temperature range 100–500 °C. All catalysts showed a lower T₅₀ than the corresponding Ce_1−xZr_xO₂ supports. Twenty weight percent LaCoO₃ catalysts presented lower T₅₀ than bulk LaCoO₃. In terms of reaction rates per mass unit of perovskite calculated at 300 °C, two facts should be noted (i) the activity order is more than 10 times higher for toluene and (ii) the reverse variation with the loading as a function of the reactant, a better activity being observed for low loadings in the case of benzene. For the same loading, the support composition influences drastically the oxidative abilities of LaCoO₃ by the surface area and the oxygen mobility.     

Surface Mechanical Properties of the Spore Adhesive of the Green Alga Ulva

The mechanical properties of the adhesive produced by spores of the green, marine, fouling alga Ulva linza are reported. Atomic force microscopy studies were performed and nanoindentation data were analyzed using a model for an asymmetric indenter. Freshly secreted adhesive is characterized by multiple layers. We found that the modulus of the outer ∼600-nm thick layer was about 0.2 ± 0.1 MPa, whereas the modulus of the inner layer was about 3 ± 1 MPa. Older adhesive showed the formation of a “crust” of harder material with a yield strength of ∼20 MPa at a loading rate of 2.5 × 10^-6 N · s^-1. Mechanical properties under tension are also described, and extension profiles that showed either constant or nonlinear force changes with tip-sample separation were observed. Models for both kinds of behavior are described. The work of adhesion between poly-dimethylsiloxane (PDMS)-coated AFM tips and the adhesive was determined to be less than 1.5 mJ · m^-2.     

Effect of LaCoO3 perovskite deposition on ceria-based supports on total oxidation of VOC

Supported LaCoO₃ perovskites with 10 wt.% loading were prepared by impregnation of different supports containing ceria with a solution of La and Co nitrates and citric acid. All precursors were calcined at 700 °C for 5 h. XRD investigations indicated the perovskite formation via “citrate” precursor only on ceria support. All catalysts were tested for toluene total oxidation in the temperature range 100–600 °C. In spite of a large surface area, alumina-supported perovskites showed a lower global activity. It appears then the necessity of the presence of a perovskite phase for good oxidative activity. In terms of reaction rates higher reaction rates per perovskite weight were observed for all supported catalysts when compared to bulk LaCoO₃.     

Electrochemical adsorption of organic bases and their conjugate acids—I. Adsorption of neutral bases at mercury

Following previous studies on solid metals, electrocapillary measurements are reported for the adsorption of a series of heterocyclic and aromatic bases (and their ions) at the mercury electrode. The adsorption isotherms are derived for various electrode potentials and standard electrochemical free energies Δ ° of adsorption are deduced and related to molecular and electronic structure of the adsorbates. Specific π-orbital interaction effects are indicated which determine the orientation of the bases at the electrode. It is shown that dipole interaction effects lead to variations of Δ ° (adsorption) with the 3/2 power of surface coverage θ; this prediction is confirmed experimentally. The variation of Δ ° with θ^3/2 has two distinct linear regions, the change of slope (∂Δ °/∂θ )_E being related to molecular orientation at high fields and coverages. The effects are closely related to the shifts of the potential of the electrocapillary maximum (e.c.m.) observed in the solutions of the bases. The observed Δ ° values at the e.c.m. are related to those found for adsorption of two bases at the air/water interface.     

Measurement of the Surface Free Energy of Amorphous Cellulose by Alkane Adsorption: A Critical Evaluation of Inverse Gas Chromatography (IGC)

Surface energies of amorphous cellulose “beads” were measured by IGC at different temperatures (50 to 100°C) using n-alkane probes (pentane to undecane). The equation of Schultz and Lavielle was applied which relates the specific retention volume of the gas probe to the dispersive component of the surface energy of the solid and liquid, γ^d_s and γ^d_l, respectively, and a parameter (“a”) which represents the surface area of the gas probe in contact with the solids. At 50°C, γ^d_s was determined to be 71.5 mJ/m², and its temperature dependence was 0.36 mJ m^-2 K^-1. Compared with measurements obtained by contact angle, IGC results were found to yield higher values, and especially a higher temperature dependence, d(γ^d_s)/dT. Various potential explanations for these elevated values were examined. The surface energy, as determined by the Schultz and Lavielle equation, was found to depend mostly on the parameter “a”. Two experimental conditions are known to affect the values of “a”: the solid surface and the temperature. While the surface effect of the parameter “a” was ignored in this study, the dependence of the surface energy upon temperature and probe phase was demonstrated to be significant. Several optional treatments of the parameter “a” were modeled. It was observed that both experimental imprecision, but mostly the fundamental difference between the liquid-solid vs the gas-solid system (and the associated theoretical weakness of the model used), could explain the differences between γ^d_s and d(γ^d_s)/dT measured by contact angle and IGC. It was concluded that the exaggerated temperature dependence of the IGC results is a consequence of limitations inherent in the definition of parameter “a”.     

Reactor and in situ FTIR studies of Pt/BaO/Al2O3 and Pd/BaO/Al2O3 NOx storage and reduction (NSR) catalysts

The reduction of NO under cyclic “lean”/“rich” conditions was examined over two model 1 wt.% Pt/20 wt.% BaO/Al₂O₃ and 1 wt.% Pd/20 wt.% BaO/Al₂O₃ NO_x storage reduction (NSR) catalysts. At temperatures between 250 and 350 °C, the Pd/BaO/Al₂O₃ catalyst exhibits higher overall NO_x reduction activity. Limited amounts of N₂O were formed over both catalysts. Identical cyclic studies conducted with non-BaO-containing 1 wt.% Pt/Al₂O₃ and Pd/Al₂O₃ catalysts demonstrate that under these conditions Pd exhibits a higher activity for the oxidation of both propylene and NO. Furthermore, in situ FTIR studies conducted under identical conditions suggest the formation of higher amounts of surface nitrite species on Pd/BaO/Al₂O₃. The IR results indicate that this species is substantially more active towards reaction with propylene. Moreover, its formation and reduction appear to represent the main pathway for the storage and reduction of NO under the conditions examined. Consequently, the higher activity of Pd can be attributed to its higher oxidation activity, leading both to a higher storage capacity (i.e., higher concentration of surface nitrites under “lean” conditions) and a higher reduction activity (i.e., higher concentration of partially oxidized active propylene species under “rich” conditions). The performance of Pt and Pd is nearly identical at temperatures above 375 °C.     

COMPARISON OF CONVECTIVE, VACUUM, AND MICROWAVE DRYING CHLORPROPAMIDE

Drying kinetics of convective, vacuum, and microwave drying of a pharmaceutical product, chlorpropamide, has been investigated on a laboratory scale, in the temperature interval from 40°C to 60°C, and the range of microwave heating power from 154 W/kg_dm to 385 W/kg_dm.

The experimental data obtained were approximated with the “thin-layer” equation and a two parameter exponential model. In order to compare convective, vacuum, and microwave drying, effective diffusion coefficients and specific heat consumption were calculated for each drying method.

Higher rates and shorter drying times were achieved at a higher temperature and microwave heating power. The highest drying rates and the lowest specific heat consumption were achieved with microwave drying. This leads to the conclusion that microwave heating is the most appropriate method for drying of chlorpropamide. The quality of product was not changed for all applied methods.     

Study of stabilized phases in high alumina cement mortars Part I Hydration at elevated temperatures followed by carbonation

The use of temperatures higher than 30°C during the hydration of 1:3 high alumina cement mortar leads to the formation of the cubic hydrate C₃AH₆, hence avoiding the conversion of CAH₁₀ to C₃AH₆. The subsequent carbonation of C₃AH₆ with CO₂ and thermal treatment leads to the formation of stable carbonated phases. The optimum hydration ages are the minimum necessary times to get C₃AH₆: 3 hours at 80°C, 6 hours at 60°C. The product is in a state we call “semiplastic” in which the next structural transformation - carbonation - occurs more easily than when the specimens have a rigid structure. The effect of a super-water-reducing admixture has also been studied.     

THERMAL PERFORMANCE AND EVALUATION OF SIPERHEATED STEM DRYING SYSTEM USING SOLAR-ASSISTED ABSORPTION HEAT TRANSFORMER

This paper summarizes the main results of our study carried out under the priority-area research “Energy Conversion and Utilization with High Efficiency” supported by the grant-in-aid of scientific research from the Ministry of Education, Science and Culture of Japan. In the research we focused on applications of solar energy utilization for industrial drying systems. In this paper a new concept of a closed drying system with superheated steam provided from a temperature boosting type heat pump (absorption type heat transformer) was proposed. The heat transformer is driven directly by heat from a solar collector. The performance for different three drying periods and a number of factors affecting it were predicted by a computer simulation. Furthermore the heat and mass transfer characteristics of water evaporation into superheated steam stream by radiative and convective heating were indicated experimentally. It was concluded that the system would be useful for industries where high temperature (over 100°C) drying is required.