Showing papers in "Korean Journal of Chemical Engineering in 2001"

CO2 Recovery from Flue Gas by PSA Process using Activated Carbon

Abstract: An experimental study was performed for the recovery of CO2 from flue gas of the electric power plant by pressure swing adsorption process. Activated carbon was used as an adsorbent. The equilibrium adsorption isotherms of pure component and breakthrough curves of their mixture (CO2 : N2 : O2=17 : 79 : 4 vol%) were measured. Pressure equalization step and product purge step were added to basic 4-step PSA for the recovery of strong adsorbates. Through investigation of the effects of each step and total feed rate, highly concentrated CO2 could be obtained by increasing the adsorption time, product purge time, and evacuation time simultaneously with full pressure-equalization. Based on the basic results, the 3-bed, 8-step PSA cycle with the pressure equalization and product purge step was organized. Maximum product purity of CO2 was 99.8% and recovery was 34%.

Oxidation and reduction characteristics of oxygen carrier particles and reaction kinetics by unreacted core model

Abstract: The reaction kinetics of the oxygen carrier particles, which are used as bed material for a fluidized bed chemical looping combustor (CLC), has been studied experimentally by a conventional thermal gravimetrical analysis technique. The weight percent of nickel and nickel oxide in oxygen carrier particles and reaction temperature were considered as experimental variables. After oxidation reaction, the pure nickel particle was sintered and unsuitable to use as fluidizing particles. The oxidation reaction rate increased with increasing weight percent of nickel in oxygen carrier particles and reaction temperature. The rate of reduction shows maximum point with weight percent of nickel oxide (57.8%) and reaction temperature (750 or 800 °C) increased. In this work, the reaction between air and Ni/ bentonite particle was described by a special case of unreacted core model in which the global reaction rate is controlled by product layer diffusion resistance. However, the reaction between CH4 and NiO/bentonite particle was described by unreacted core model in which the global reaction rate is controlled by chemical reaction resistance. The temperature dependence of the effective diffusivity of oxidation reaction and reaction rate constant of reduction reaction could be calculated from experimental data and fitted to the Arrhenius equation.

Colloid Chemical Approach to Nanotechnology

Abstract: Colloid chemical methods for the preparation of nanoparticles and their self-assembly and organization into 2-dimensional arrays and three dimensional networks are surveyed. Potential applications of nanoparticles and nanostructured materials, fabricated by the wet colloid chemical approach, are also illustrated.

Preparation of Microporous Silica Membranes for Gas Separation

Abstract: Microporous silica membranes for hydrogen separation were prepared on a γ-alumina coated α-alumina tube by sol-gel method. The reactants of sol-gel chemistry were tetraethoxysilane (TEOS) and methacryloxypropyl-trimethoxysilane (MOTMS). The silane coupling agent, MOTMS, was added as a template in order to control the pore structure to the silicon alkoxide, TEOS. In particular, the microporous membranes were prepared by changing the molar ratio of MOTMS with respect to other substances, and their pore characteristics were analyzed. Then, the effects of thermal treatment on the micropore structure of the resulting silica membranes were investigated. The pore size of the silica membrane prepared after calcination at 400–700 ‡C was in the range of 0.6–0.7 nm. In addition, permeation rates through the membranes were measured in the range of 100–300 dgC using H2, CO2, N2, CH4, C2H6, C3H6 and SF6. The membrane calcined at 600 ‡C showed a H2 permeance of 2×10-7-7×10-7 molm-2s-1Pa-1 at permeation temperature 300 ‡C, and the separation factors for equimolar gas mixtures were 11 and 36 for a H2/CO2 mixture and 54 and 132 for a H2/CH4 mixture at permeation temperatures of 100 ‡C and 300 ‡C, respectively.

New Aspects of Heterogeneous Photocatalysts for Water Decomposition

Abstract: Several new photocatalysts for overall water splitting are described. Under UV light irradiation (270 nm), La-doped NaTaO3 modified with NiO decomposed water into H2 and O2 with extremely high quantum efficiency. Under an optimized condition, the apparent quantum efficiency, which was estimated with numbers of irradiated photons and evolved H2 molecules, reached 56%. New stable photocatalytic materials containing elements with d10 electronic configuration such as In3+ Sn4+ and Sb5+ were developed for overall water splitting. Some mesoporous oxides were proved to be effective photocatalysts. (Oxy)nitrides of some early transition metals, i.e., Ta, Nb and Ti, were found to be stable materials having potentials for H2 and O2 evolutions under visible light irradiation (⪯600 nm). The electronic structures of these photocatalysts are also discussed based on DFT calculation.

Adsorption equilibrium of heavy metals on natural zeolites

Abstract: Prior to equilibrium experiments, a clinoptilolite-type Korean natural zeolite was pretreated with HCl, NaOH, and NaCl to improve the ion-exchange capacity for heavy metals. Singleand multi-species equilibrium data of heavy metals such as copper, cadmium, cesium, and lead on treated and untreated natural zeolites were measured experimentally. For single-species equilibrium data, one of the conventional adsorption isotherms, the Sips equation, was used to fit them and then multi-species equilibrium data were predicted by using the loading ratio correlation (LRC), the ideal adsorbed solution (IAS) theory, and the real adsorbed solution (RAS) theory based on the Sips equation. In applying the RAS theory, we used the Wilson equation for fitting activity coefficients of metal ions in the ion-exchanger phase. It was proven that basic adsorption models except the LRC model could describe multi-species ion-exchange equilibrium for heavy metals/natural zeolite systems well.

Adsorption of Basic Dyes in a Fixed Bed Column

Abstract: The adsorption of basic dyes from aqueous solution onto granular activated carbon and natural zeolite has been studied by using a fixed bed column. The design procedures for fixed bed adsorption columns have been investigated for two basic dyes, Maxilon Goldgelb GL EC 400% (MG-400) and Maxilon Shwarz FBL-01 300% (MS-300). The effects of process variables such as bed height, volumetric flow rate, and dye concentration have been investigated. The results have been used to predict the effect of parameter changes on the system by using the bed depth service time (BDST) approach. The performances of the column charged with the natural zeolite were compared with those of the column charged with activated carbon.

Adsorption Equilibrium and Kinetics of H2O on Zeolite 13X

Abstract: The adsorption characteristics of H2O on zeolite 13X were measured by a gravimetric method. The adsorption isotherm showed type II isotherm and was fitted by using both the excess surface work (ESW) model and Langmuir-Freundlich model. The results predicted by the Langmuir-Freundlich model were much smaller than the experimental results at higher-pressure region. However, the ESW model agreed well with the experimental data over the whole pressure region. In this case, a plot of the change in chemical potential versus the amount adsorbed gave two linear regions due to secondary effects such as capillary condensation. The experimental uptake curves were well fitted by several LDF models and solid diffusion model with the error range of 1.5-3.5%. Unlike the expectation that the more rigorous solid diffusion model would fit better, Nakao-Suzuki model showed the best agreement with experimental uptake data.

Kinetics and Rate of Enzymatic Hydrolysis of Cellulose in Supercritical Carbon Dioxide

Abstract: Experiments were carried out on the application of supercritical fluid to the hydrolysis of cellulose by the enzyme, cellulase. The stability of cellulase was sustained at the pressures of up to 160 atm for 90 min at 50 ‡C in supercritical carbon dioxide. In the hydrolysis of cellulose the glucose yield was 100% at supercritical condition. Kinetic constants of hydrolysis at supercritical condition were increased as compared to those at atmospheric condition. The hydrolysis reaction was found competitively inhibited by glucose at supercritical condition.

A Study on the Fabrication of an RTD (Resistance Temperature Detector) by Using Pt Thin Film

Abstract: Pt thin film was deposited on alumina substrate by using DC sputter and the serpentine pattern was formed by photolithography to fabricate the resistance temperature detector (RTD) The Pt film was thermally treated and the surface structure of the film and its effect on the electrical resistance were studied The sheet resistance of the film depends on the thickness and thermal treatment The developing and etching conditions for serpentine patterning of the film were investigated and various RTD samples were prepared All of the fabricated RTD’s show a good linear variation of resistance with the temperature The temperature coefficient of resistance (TCR) values of RTD’s increased with decreasing film thickness, narrowing pattern line width, and increasing annealing temperature The highest TCR value was obtained from RTD with 1 mm line width thermally treated at 700 ‡C and was 353×103 ppm/‡C

Solubilities of Calcium and Zinc Lactate in Water and Water-Ethanol Mixture

Abstract: The solubility of lactate salts, L(+) and DL(±) forms of calcium and zinc lactate in water at temperature between 5 and 80 ‡C, was measured and empirical equations were obtained by regression of solubility-temperature data. The equations can be used to calculate the solubility of calcium and zinc lactate at a given temperature. The change in solubility of L(+) and DL(±) calcium and zinc lactate in water-ethanol mixture at 20 ‡C was also investigated. The solubilities of calcium and zinc lactate were lowered by the addition of ethanol to the solution.

Rheological properties and stability of magnetorheological fluids using viscoelastic medium and nanoadditives

Abstract: In order to improve the stability of magnetorheological (MR) fluids, viscoelastic medium having 2.2 Pa yield stress has been used as a continuous phase and nanosized CrO2 particles are added too. The rheological properties as well as the dispersion stability of MR fluids have been studied by using a stress-controlled rheometer and sedimentation test. The steady-shear MR response was independent of the continuous and nano additives and the fieldinduced yield stress increased subquadratically with the flux density. Since the constant stress is generated within the limit of zero shear rate, the plateau in the flow curve corresponds to the Bingham yield stress. Under an external field, the yield stress varied as B3/2. The yield stress has an approximately linear relation with the particle volume fraction.

Removal of heavy metals in plating wastewater using carboxylated alginic acid

Abstract: Potentially, biosorption is an economic process for metal sequestering from water. Carboxylated alginic acid showed high uptake capacities for heavy metals of 5-6 meq/g dry mass. For application to actual plating waste-water, the carboxylated alginic acid was immobilized using PVA. In order to remove chelating or organic materials in plating wastewater, oxidation using sodium hypochlorite was performed as a pretreatment. When carboxylated alginic acid bead was applied in a packed-bed contactor, the breakthrough point of copper ion in the acid-alkaline wastewater appeared around 350 bed volumes; the breakthrough point of nickel ion in the chelating wastewater emerged around 200 bed volumes. The adsorption capacity for heavy metal of the carboxylated alginic acid bead was higher than that of a commercial ion exchanger (IR-120 plus) in plating wastewater.

Ethylene Glycols Technology

Abstract: Ethylene glycol (EG) or monoethylene glycol (MEG), the adduct of ethylene oxide (EO) and water, is the simplest glycol. It is the first of a homologous series of three dihydroxy alcohols discussed in this article. Diethylene and triethylene glycols (DEG, TEG) are the other two. These glycols are composed solely of carbon, hydrogen and oxygen. Although they have similar chemical properties, their applications vary mainly with physical properties such as viscosity, hygroscopicity and boiling point. The commercial route to ethylene glycols in use today involves the noncatalyzed thermal hydrolysis of ethylene oxide in water. This process produces chiefly mono-, di- and triethylene glycols and a small amount of tetraethylene and heavier glycols. The yield of monoethylene glycol via hydrolysis is controlled by the water-to-ethylene oxide ratio in the feed to the reactor system. Removal of excess water following the glycols-forming hydrolysis is energy intensive and requires capital investment in evaporators. Such costs limit the amount of excess water which is used. In practice, reactor feed water content is such that the selectivity to monoethylene glycol achieved ranges from 89-91%. The equipment elements in a simplified process flow diagram are discussed along with recommended materials of construction. Among other items discussed are a) a brief review of economic factors; b) health, safety and environmental issues; and c) commercial applications of the three glycols, MEG, DEG and TEG. Finally, recommendations for shipping, handling and storage are discussed.

Preparation, Crystal Structure, and Photocatalytic Activity of TiO2 Films by Chemical Vapor Deposition

Abstract: Photocatalytic activities of TiO2 films were experimentally studied. TiO2 films with different crystal structures (amorphous, anatase, rutile) were prepared by a Low Pressure Metal Organic Chemical Vapor Deposition (LPMOCVD) at different reaction temperatures and also by a Sol-Gel method using TTIP (Titanium Tetra Iso-Pro-poxyde). The Effect of CVD preparation method, CVD reaction conditions, crystal structure and wave-length of UV light on the photocatalytic decomposition rate of methylene blue in aqueous solution were studied. First, the characteristics of CVD preparation of TiO2 films, such as the CVD film growth rate, crystal structure and morphology of the grown TiO2 films, were experimentally studied as a function of CVD reaction temperature. Secondly, photocatalytic activities of TiO2 films were evaluated by using two types of photo-reactors. The results indicated that TiO2 films prepared by CVD exhibit higher photocatalytic activity than a catalyst prepared by the Sol-Gel method. Among the CVD grown TiO2 films, anatase and rutile showed high photocatalytic activities. However, amorphous TiO2 films showed lower activities. The activity of the photocatalysts of anatase films was excellent under all types of UV-lamps. The activity of CVD-prepared anatase films was four to seven times higher than that of photocatalyst films prepared by the Sol-Gel method.

Conversion of Methane to Higher Hydrocarbons in Pulsed DC Barrier Discharge at Atmospheric Pressure

Abstract: Conversion of methane to C2/C3 or higher hydrocarbons in a pulsed DC barrier discharge at atmospheric pressure was studied. Non-equilibrium plasma was generated in the barrier discharge reactor. In this plasma, electrons which had sufficient energy collided with the molecules of methane, which were then activated and coupled to C2/C3 or higher hydrocarbons. The effect of the change of applied voltage, pulse frequency and methane flow rate on methane conversion, selectivities and yields of products was studied. Methane conversion to higher hydrocarbons was about 25% as the maximum. Ethane, propane and ethylene were produced as primary products, including a small amount of unidentified C4 hydrocarbons. The selectivity and yield of ethane as a main product came to about 80% and 17% as the highest, respectively. The selectivities of ethane and ethylene were influenced not by the change of pulse frequency but by the change of applied voltage and methane flow rate. However, in case of propane, the selectivity was independent of those condition changes. The effect of the packing materials such as glass and A12O3 bead on methane conversion was also considered, showing that A12O3 played a role in enhancing the selectivity of ethane remarkably as a catalyst.

Constrained digital regulation of hyperbolic PDE systems: A learning control approach

Abstract: In this paper, exploiting repetitive properties, a constrained digital regulation technique for first order hyperbolic PDE systems is proposed that guarantees the stability and performance of the closed loop system.

Effect of Calcination Temperature and Addition of Silica, Zirconia, Alumina on the Photocatalytic Activity of Titania

Abstract: Nanophase titania was prepared by sol-gel method and spray pyrolysis. We tried to elucidate the relationship between the photoactivity and the crystallite size of anatase phase. To better understand the changes in the bulk and the surface of titania as the calcination temperature is changed, EPR and photoluminescence analysis were carried out. The effect of the secondary metal oxide embedded into titania matrix on the photoactivity was also investigated. It was found that the photoactivity of titania has a linear relationship to the crystallite size. For the analysis of EPR and photoluminescence for pure titania, the increase of photoactivity with increasing the calcination temperature is due to the formation of surface active sites such as O- as well as the increase of crystallinity resulting from the removal of bulk defects. For silica/titania mixed oxide, it was found that the improvement of the thermal stability of anatase phase is important to enhance the photoactivity of titania because the prepared catalyst was calcined at a higher temperature than 700 °C without forming rutile phase. It was also concluded that the simultaneous increase of the surface area and the crystallinity promises to improve the photoactivity achieved by increasing the content of silica up to 60%. By the analysis of EPR and photoluminescence, it was found that the embedding of silica into titania matrix suppresses the formation of Ti3+ and produces a new active site of Ti-O-Si, which easily interacts with the oxygen. In the investigation of zirconia/titania and alumina/titania mixed oxide, it was found that the increase of the surface OH is essential to positively affect of the improved thermal stability on the photoactivity.

Effect of precursors on the morphology and the photocatalytic water-splitting activity of layered perovskite La2Ti2O7

Abstract: A [110] layered perovskite, La2Ti2O7, was a good photocatalyst under ultraviolet light in water splitting reaction. The material was synthesized with La2O3 and TiO2 as precursors by solid-state transformation. The morphology and photocatalytic activity of La2Ti2O7 depended on the preparation methods, as well as purity and morphology of the precursors. Wet-grinding of precursors in ethanol gave a product with higher crystallinity and phase purity, and thus higher photocatalytic activity, than dry-grinding without solvent. It was important to reduce the particle size of La2O3, as it usually had larger initial particle sizes than TiO2. Thus, the particle size of La2O3 had a strong effect on the crystallinity and surface area of the product La2Ti2O7. On the other hand, a severe chemical purity control was required for TiO2, while the effect of morphology was relatively small. In all cases, a high degree of crystallinity and purity of the prepared La2Ti2O7 was critical to show a high photocatalytic water-splitting activity.

Inorganic membranes and membrane reactors

Abstract: The inorganic membrane reactor is a combined unit operation of chemical reactions and membrane separations. By having a membrane reactor, the downstream separation load can be reduced. Also, the yields can be increased and conversion can be improved for equilibrium limited reactions. However, many of the industrial chemical reactions take place at high temperature that the conventional polymeric membranes cannot withstand. A great deal of research has been done recently to develop ion-conducting ceramic membranes. Many of these have been successfully employed to form membrane reactors for many industrially relevant chemical reactions, such as hydrogenation, dehydrogenation, oxidation, coupled reactions, and decomposition reactions. An overview is given for the area of inorganic membrane preparations and membrane reactors. Many examples of petrochemical interests are presented, including hydrocarbon conversions and fuel cell applications.

Gasification of Food Waste with Steam in Fluidized Bed

Abstract: Biomass has became an important renewable alternative energy resource. Million tons of food sludge, which is difficult to handle because of its rank smell and water content, is generated in Korea. Thermochemical conversion is one way to convert biomass to energy; it can be divided into carbonization, liquefaction, and gasification. Carbonization of food waste was carried out in a conventional stainless steel autoclave of 2 L capacity at different temperatures. Since gasification produces hydrogen-rich synthesis gas, which can be used for methanol synthesis, gasification of carbonized solid was studied in the fluidized-bed gasifier. The reaction parameters in the gasification of carbonized solids were investigated.

The reactivity of V 2 O 5 -WO 3 -TiO 2 catalyst supported on a ceramic filter candle for selective reduction of NO

Abstract: For realizing the environmental issues and constituting an economical treatment system, a catalytic filter based on V2O5/TiO2 supported on tubular filter elements has many advantages by removing NOx and particulate simultaneously from flue gas. In order to improve the activity of a catalytic filter based on V2O5/TiO2 supported on a commercial high temperature filter element (PRD-66), the promoting effects of WO3 were investigated in an experimental unit. PRD-66 presented very good properties for SCR catalyst carrier since it contains much active material such as A12O3 SiO{om2}, and MgO whose contributions were remarkable. For additional catalyst carrier, TiO2 particles were coated in the pores of PRD-66 with relatively good distribution of the particle size less than 1 μm, by a coating process applying centrifugal force. WO3, in the V2O5-WO3-TiO2/PRD-66 catalytic filter system, increased the SCR activity significantly and broadened the optimum temperature window. The catalytic filter shows the maximum NO conversion of more than 95% for NO concentration of 700 ppmv at face velocity of 0.02 m/sec, which is comparable to the current commercial catalytic filters of plate form.

Water tolerance of DeNOx SCR catalysts using hydrocarbons: Findings, improvements and challenges

Abstract: The recent developments on the effect of H2O on deNOx performance of a variety of SCR catalysts selectively removing NOx by hydrocarbons in excess oxygen have been reviewed. In particular, the water tolerance of the catalyst is summarized to illustrate a common deactivation behavior of SCR catalyst for the reduction of NO by hydrocarbons under wet feed gas mixture. Earlier proposals elucidating the possible cause of the catalyst deactivation under wet conditions are discussed, focusing mainly on the catalyst characteristics. A promising way, which can improve the water tolerance and the hydrothermal stability of zeolite-based SCR catalyst, is also described.

Development of a microchannel catalytic reactor system

Abstract: The purpose of this article is to demonstrate the applicability of microreactors for use in catalytic reactions at elevated temperatures. Microchannels were fabricated on both sides of a silicon wafer by wet chemical etching after pattern transfer using a negative photoresist. The walls of the reactor channel were coated with a platinum layer, for use as a sample catalyst, by sputtering. A heating element was installed in the channel on the opposite surface of the reactor channel. The reactor channel was sealed gas-tight with a glass plate by using an anodic bonding technique. A small-scale palladium membrane was also prepared on the surface of a 50-Μm thick copper film. In the membrane preparation, a negative photoresist was spin-coated and solidified to serve as a protective film. A palladium layer was then electrodeposited on the other uncovered surface. After the protective film was removed, the resist was again spin-coated on the copper surface, and a pattern of microslits was transferred by photolithography. After development, the microslits were electrolitically etched away, resulting in the formation of a palladium membrane as an assemblage of thin layers formed in the microslits. The integration of the microreactor and the membrane is currently under way.

Mechanisms and Kinetics of Cadmium and Lead Capture by Calcined Kaolin at High Temperatures

Abstract: One of the most promising technologies for reducing volatile metal emissions from the waste incineration process is the high-temperature capture of vapor-phase metals before their condensing into fine particles. Packed bed sorption experiments for the capture of gaseous cadmium and lead using calcined kaolin particles were performed in a temperature range of 973-1,173 K. A calcined kaolin particle is composed of 2–3 im grains separated by large pores, through which the cadmium and lead vapor easily diffuse. Cadmium and lead react with sorbent to form waterinsoluble metal-mineral complexes (PbAl2Si2O8, CdAl2Si2O8 and Cd2Al2Si2O9). An increase in bed temperature results in an increase of capturing rates, but it has no effect on maximum uptakes for both metals. The diffusional resistance developed in the interior of the porous kaolin particles became limiting only after the conversion of metakaolinite reached a value of 50% or higher. The order of reaction with respect to the gas-phase concentration was determined to be 1.67 and 3.26 for lead and cadmium, respectively. The activation energy, Ea, was estimated to be 10.16 and 5.56 kcal/mol for lead and cadmium, respectively.

Photocatalytic oxidation of ethylene to CO2 and H2O on ultrafine powdered TiO2 photocatalysts: Effect of the presence of O2 and H2O and the addition of Pt

Abstract: The complete photocatalytic oxidation of C2H4 with O2 into CO2 and H2O has been achieved on ultrafine powdered TiO2 photocatalysts and the addition of H2O was found to enhance the reaction. The photocatalytic reaction has been studied by IR, ESR, and analysis of the reaction products. UV irradiation of the photocatalysts at 275 K led to the photocatalytic oxidation of C2H4 with O2 into CO2, CO, and H2O. The large surface area of the photocatalyst is one of the most important factors in achieving a high efficiency in the photocatalytic oxidation of C2H4. The photoformed OH species as well as O 2 − and O 3 − anion radicals play a significant role as a key active species in the complete photocatalytic oxidation of C2H4 with O2 into CO2 and H2O. Interestingly, small amount of Pt addition to the TiO2 photocatalyst increased the amount of selective formation of CO2 which was the oxidation product of C2H4 and O2.

The preparation of V2O5/TiO2 catalyst supported on the ceramic filter candle for selective reduction of NO

Abstract: In order to prepare the catalytic filters based on V2O5/TiO2 for the removal of NOx and participate simultaneously from the flue gas stream, the experimental study was carried out. The effective method to support TiO2 layer in the pore of the commercial ceramic filter element was developed. TiO2 layer was supported on the filter element by three methods; impregnation with Ti solution, sol-gel dip coating and sol-gel centrifugal coating. As the model test to check the catalytic activity, NO reduction in the oxidizing stream was investigated. The catalytic filter prepared by applying the centrifugal force showed the best NO conversion more than 90% when the face velocity was 0.02 m/sec. This was a very promising result for the application of catalytic filter for the flue gas control at high temperature. The supporting methods by the impregnation and dip coating were not recommended because the TiO2 layer was concentrated in the exterior layer of the filter element.

Effect of Water on Liquid Phase DME Synthesis from Syngas over Hybrid Catalysts Composed of Cu/ZnO/Al2O3 and γ-Al2O3

Abstract: DME synthesis from syngas via methanol has been carried out in a single-stage liquid phase reactor. Cu/ ZnO/Al2O3 and γ-Al2O3 were used together as methanol synthesis catalyst and dehydration catalyst, respectively. The influence of water on the catalytic system was investigated mainly. Water affected the activity of methanol dehydration catalyst as well as methanol synthesis catalyst. Thus, removal of water from the reaction system, by adding a dehydrating agent or controlling methanol formation rate by the reaction parameters, was efficient in maintaining the high catalytic activity and stability.

Process system engineering in wastewater treatment process

Abstract: This paper reviews the research and development of process system engineering (PSE) in the wastewater treatment process (WWTP). A diverse range of PSE applications have evolved in the wastewater treatment process, such as modeling, control, estimation, expert system, fault detection and monitoring system. This article describes several types of PSE that have proven to be effective in WWTP. The merits and shortcoming of PSE and its detailed applications are presented. Since its development is the forefront in WWTP, a reasonable review of the research progress in this field is addressed.

Performance improvement of integrated coal gasification combined cycle by a new approach in exergy analysis

Abstract: A new approach to exergy analysis is proposed for examing the consumption of energy as the minimum driving force and of exergy consumption that is avoidable, and for the development of a method to predict the alternatives in system improvement by exploring possible reduction in the avoidable exergy consumption. Also suggested in this study is a dimensionless parameter γAVO, which is the ratio of avoidable exergy consumption over total fuel energy input to the system. Detailed analyses, including the calculation of exergy consumption, exergy loss and avoidable exergy consumption, were conducted for each component in the syngas cooling system in the Integrated coal Gasification Combined Cycle (IGCC) plant, to prove the effective application of the proposed method. The analysis showed that the rank of avoidable exergy consumption was different from that of total energy consumption, and hence it confirmed that an energy analysis by conventional methods misled the focus of improvement in system design. The methodology developed in this study offers a new approach for system designers to analyze and to improve the performance of a complex energy system such as an IGCC plant.