The performance of microfiltration with cyclic backwashing of secondary effluent emanating from a sewage treatment plant was assessed for the purpose of recycling of water. Microfiltration experiments were conducted under constant rate and constant pressure conditions, and filtration behavior in the two operations was compared. The filtrate obtained was found to be free from E. coli, and hence it can be reused as reclaimed water for urban reuse. As filtration proceeded, cake formation and pore blocking of the membrane occurred, causing an increase in pressure in constant rate filtration or flux decline in constant pressure filtration. Although backwashing was effective in decreasing cake resistance, the irreversible pore blocking of the membrane became gradually more severe with the increase in the number of backwashings. Characteristics of cake formation were analyzed using the compressible cake filtration model, and the pore blocking was found to be well described by a two-phase intermediate blocking law. As a result, the filtration behavior in constant pressure filtration with cyclic backwashing was expressed well by using models that represent cake formation and pore blocking, on the basis of the experimental data of constant rate filtration with cyclic backwashing. Moreover, it was shown from the experimental and predicted results that constant pressure filtration with cyclic backwashing assures almost constant throughput rate.

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This paper deals with an improvement of settling tank performance. New equipment is proposed and its usefulness is confirmed. In combined sewerage systems that are employed in big cities, storm waters often exceed the capacity of the treatment plant, so that they are discharged with only simple treatment. Recently, water pollution caused by this flush-over water has caused environmental problems. To meet this problem, the enhancement of the settling tank capacity is an important and urgent issue for urban sewage treatment plants. The objective of this paper is to develop a new method to enhance the treatment efficiency without building additional treatment plants.
In the paper, the characteristics of a rectangular settling tank are investigated using the numerical solution of a mathematical model to show the capacity limit of the conventional settling tank.
The newly developed settler is an improvement of the lamella settler, which arranges inclined parallel plates in the vertical direction, contrary to the usual horizontal arrangement. In this method, the separated clear water is removed directly by suction from the top end of the parallel plates. For the removal of clear water, the right and left edges of the plates are closed, to make a tube with rectangular cross section. These are the unique and original points of the equipment.
Since each settling tube acts as a small settling tank, the treatment capacity is proportional to the number of settling tubes. Furthermore, this system is less restricted by the surface area of the tank, as the tubes are arranged vertically.
The usefulness of the method was confirmed by laboratory experiments and numerical analysis. It was also shown from a numerical estimation that the new system can enhance the capacity of the settling tank to more than five times that of the conventional one.

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To examine the effects of supporting material and the properties of activated sludge, dynamic filtration of various activated sludges was performed at the filtration pressure of 0.3 kPa using non-woven fabrics with fiber density of 3.0×10^-2−0.18 kg·m^-2 and stainless nets with pore size of 44−100 μm. No significant difference in initial flux was found between these non-woven fabrics and stainless nets, but the stainless nets kept higher flux for a longer time than the non-woven fabrics. Dynamic filtration of seven activated sludges with MLSS concentrations were 9.0−14 kg·m^-3 was performed using a stainless net with pore size of 77 μm. Average filtration resistance (α_av) was estimated for each sludge, and their values ranged from 2.4×10⁹ to 5.6×10¹¹ m·kg^-1. The α_av value increased with decreases in average particle size of activated sludge in both the bulk (d) and the upper layer after sedimentation for 30 min (d_u). It also increased with an increase in activated sludge concentration in the upper layer after sedimentation for 30 min (C_u). From these results, it was found that the values of d, d_u and C_u were important factors determining the separation performance in dynamic filtration of activated sludge. When dynamic filtration of activated sludge at a sewage plant was conducted with a filtration area of 0.2 m² for more than 20 days, it was observed that flux and activated sludge concentration in permeate were strongly dependent on the C_u value.

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A bench-scale submerged membrane activated sludge process using a microfiltration type hollow fiber membrane module and synthetic wastewater was operated at different BOD loadings and sludge retention times (SRT), and various filtration resistances were investigated. At short SRT, because of unstable biological growth and incomplete metabolism of organic matter, the suction pressure and the filtration resistances of the membrane and adhered sludge (cake) increased rapidly and randomly with treatment time, and thereafter destabilized the process. At long SRT and low BOD loading, low and steady suction pressure and filtration resistances were maintained for a long time. Almost all microorganisms in the bioreactor were in the stationary phase at SRT=500 d (without sludge withdrawal), while the cake filtration resistance was very small and the microorganisms had better filtration characteristics.

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In the activated sludge treatment commonly used in sewage treatment plants, the activated sludge in an aeration tank occasionally has a bulking phase, and the sewage water cannot be treated due to the difficulty of solid-liquid separation in a final settling tank. It is known that the excess activated sludge which is discharged from the general sewage treatment plant has very bad dewaterability. We have previously reported that the freezing and thawing treatment improved its solid liquid separation characteristics remarkably.
In this paper, we report the effect of the freezing and thawing treatment on the solid-liquid separation characteristics of bulking and normal sludges acclimated to glucose and peptone, and the comparison of this effect between normal and bulking acclimated sludges and sewage sludge. This freezing and thawing treatment improves the settleability of all the sludges, and the floc of treated sludge acquires a denser structure. The filterability of bulking acclimated sludge is worse than that of the other sludges. This treatment also, however, improves the filterability of all the sludges and has almost equal effects on all kinds of sludges.

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In order to recover metal from plating wastewater, an attempt was made to precipitate copper in the form of sulfides, which tend to form fine particulates. Model plating wastewater containing 20, 100 or 250 mg-Cu/dm³, and real plating wastewater containing Cu, Zn and Ni at concentrations of 100 mg/dm³ were employed. Na₂S, Na₂S₂ and Na₂S₄ were used as sulfurization agents at a constant pH. Particulate size and filtration characteristics of precipitated copper sulfides were investigated.
Results showed that copper sulfide particulates formed with Na₂S were the smallest in size and slowest in growth rate compared to those formed with Na₂S₂ and Na₂S₄. At a constant pH of 1.4-1.5, no particulates of copper sulfides were observed when the amount of Na₂S added to Cu solution was controlled below 1.5 mol/mol-Cu. On the other hand, particulates of copper sulfides were formed when the amount of Na₂S exceeded 1.0 mol/mol-Cu at pH 2.4-2.5.
The filtration characteristics such as the mean specific filtration resistance and compressibility coefficient of copper sulfide cakes formed with sulfides of sodium reduced in size in the order Na₂S<Na₂S₂<Na₂S₄. All copper sulfides were superior to copper hydroxide in terms of filtration characteristics, except for copper sulfides formed with Na₂S of 1.0 mol/mol-Cu at pH 2.4-2.5.

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An electrokinetic method employing an ion-exchange reaction has been developed for remediation of soils contaminated with heavy metals, having relatively low hydraulic permeability. Consolidated bentonite cake contaminated with zinc was prepared by the mechanical expression method, and the removal of zinc ions from the cake was examined by the electrokinetic method employing the addition of sodium ions. From the preliminary adsorption test of zinc ions onto bentonite clay, the adsorption behavior was found to be described by an equation of the Freundlich type. Zinc ions were desorbed from the bentonite due to a cation-exchange reaction caused by the addition of sodium ions, and were efficiently removed from a cake of low hydraulic permeability by electroosmotic flow. The permeation rate of the liquid through the cake at the steady state was found to increase linearly with the current density, and the rejection ratio of the zinc ion was independent of the current density. Consequently, it appeared that the rejection rate of the zinc ion was proportional to the current density. Moreover, at the steady state, the variation of the rejection ratio with the permeate volume became marked with the increase of the concentration of added zinc ions, and it was not influenced by the cake thickness.

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The separation mechanism of a non-woven metallic fiber filter media having a depth filtration structure was investigated based on a probability model and a filtration test. First, thin non-woven filter media were prepared as filter media of unit thickness, and their pore size distribution was measured by image analysis. The thin media were then layered to make filtration media of various thicknesses, and the relationship between the thickness of the medium and the partial separation efficiency was obtained through a filtration test. In the case of non-woven filter media, the increase in the number of layers led to the smaller separation size and more accurate separation. To clarify the effect of pore size distribution, woven wire meshes with more homogeneous pores were evaluated in the same way. The separation size of wire meshes was almost constant regardless of the number of layers. By considering the number of layers as the number of separation trials, the probability model demonstrates the relationship between the thickness of media and the separation size. Consequently, this model can estimate the separation size of filter media.

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To estimate the pore size of a mircofiltration membrane easily, a method based on a pure water permeation test has been developed. The pore size of a symmetric ceramic membrane was estimated with high accuracy by applying Darcy's law and the Kozeny-Carman equation to the measurements of pure water permeability. Based on this method, the pore size of a double layer membrane composed of two symmetric membranes was evaluated. The pore size of the top layer membrane was estimated by measuring the pure water permeation rates of the double layer membrane and the bottom layer membrane alone. Moreover, the pore size of a very thin skin layer coated on a supporting layer in an asymmetric membrane was estimated using a similar method.

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The use of vibration on a filter can effectively reduce the membrane fouling by the shearing action on the membrane surface. The effect of vibration parameters on crossflow microfiltration performance was studied with two kinds of particle suspensions. The experimental results show that the filtration rate depends mainly on the product of frequency and amplitude. A method of calculating the crossflow microfiltration process with vibration was developed by incorporating the effects of vibration parameters into a particle adhesion probability model. The calculated results coincide favorably with the experimental results for a polystyrene latex suspension.

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Asymptotic perturbation technique was applied to mass transfer in parallel plate membrane filtration processes on the basis of Berman's analytic solution of flow fields by assuming that the filtration flow velocity is constant. Pressure-driven and diffusive membrane transport was treated under the assumption that the axial length scale is sufficiently larger than the channel width. An ordinary differential equation for the solute permeation flux and the solute concentration at the membrane surface was derived from the mass balance equation by perturbation analysis. On the basis of the asymptotic ordinary differential equation, approximate solutions of overall mass transfer coefficient and Sherwood number were obtained under the homogeneous boundary condition that the solute concentration outside of the membrane is zero. Validity of the derived results was confirmed by comparing them with a series solution derived from eigenfunction expansion in the asymptotic state in which the filtration flux is sufficiently low. The proposed asymptotic method refines the conventional film theory and can be applied to mass transfer modeling of a variety of membrane filtration processes including low Reynolds number flow systems.

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An analytical solution of the basic differential equation for a constant-current electro-osmotic dewatering is presented by assuming that both a modified consolidation coefficient C_e and an electro-osmotic pressure gradient E_pg are constant. Bentonite was used as an experimental material. Electro-osmotic dewatering of homogeneous bentonite cake was conducted under a constant electric current density i of 0.125−4 A/m². C_e and E_pg, both obtained by a fitting method, increase with increasing i. The final moisture distribution of the material can be explained well by the present theory. The progress of electro-osmotic dewatering can be represented by the average consolidation ratio U_c, as in a mechanical expression. The agreement between calculated and experimental U_c under the condition i<1 A/m² is satisfactory. The coincidence between theory and experiment for i>1 A/m² is good for the first half of the dewatering process but rather poor for the second half of the process, since the creep deformation of the material is not considered in the basic differential equation.

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Electric power application for electro-osmotic dewatering has been generally investigated under conditions of either constant voltage or constant current. If the electrical resistance between two electrodes holding a material such as sludge increases with dewatering, the dewatering process has to be stopped when the voltage required to maintain a constant current is too high, while the process operated at constant voltage stops because the current passing through the material gradually decreases. The increase or decrease of the electrical resistance between the electrodes depends on the physical and electrical properties of the material to be dewatered. In view of these properties, a combination of constant voltage and constant current was investigated as a means to improve the dewatering process. The combined operation was shown to be effective in terms of the amount of water removed and the efficiency of electric power consumption for its removal.

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Stress relaxation process of cross-linked sodium polyacrylate was investigated. When expression or expansion are stopped before a material reaches its equilibrium state, the stress of the material will decrease/increase as the material relaxes. The change of stress was measured after interruption of a constant-pressure or constant-rate expression/expansion operation of a packed spherical gel bed. It was found that the equilibrium stress of the material does not depend on the mode of expression/expansion (constant-pressure or constant-rate expression/expansion) but is uniquely determined by the average consolidation/expansion ratio when the expression/expansion is interrupted. This relaxation process was analyzed by use of the effective osmotic pressure, that is, the difference between the swelling pressure of the gel and the pressure applied to the gel. The reasonable agreement between calculated and empirical stress supports the validity of the analysis.

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To improve the particle collection performance and reduce the liquid volume of spray in the cyclone scrubber, experimental and numerical studies have been conducted. Particle deposition points were simulated with and without particle re-entrainment. Effect of surfactant concentration in spray liquid on particle collection performance was experimentally investigated.
From the simulation results, particles with diameters of 1.0 and 2.5 μm are deposited mainly on the upper cylindrical wall and bottom section of the conical wall. These results indicate that the spray nozzle position at the upper cylindrical wall is effective to improve the collection performance of the cyclone scrubber. Furthermore, from the experimental results, adding surfactant to the spray liquid improved the collection performance compared with the water sprayed to the at the same liquid flow rate. The addition of the surfactant to the spray liquid decreased the surface tension of the spray liquid and reduced the size of the spray droplets, so that droplets more easily collided with the particles.
From these results, it is clear that addition of surfactant to spray liquid is effective to improve the collection performance and reduce the spray liquid volume.

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The authors found that monodispersed bubbles with a mean diameter of less than 1 μm (monodispersed nano-bubbles) were generated from a porous glass membrane with uniform size-controlled pores. The size of the bubbles generated could be controlled by varying the pore size of the membrane used. When air was permeated through a hydrophilic tubular membrane at a right-angle to the flow of pure water containing sodium dodecyl sulfate (SDS) of 1.7 mol·m^-3 as a surfactant, and then dispersed into the water phase flowing on the inner side of the membrane, monodispersed bubbles were generated in the pressure region that exceeded the bubble point pressure. Under such conditions, nano-bubbles with a mean diameter of 0.720 μm were generated from a membrane with a mean pore diameter of 0.084 μm. The mean diameter of the bubbles generated was proportional to the mean pore diameter of the membrane used. By contrast, bubbles with a broad size distribution were generated from a hydrophobic membrane, and bubble point pressure was not observed. When the SDS concentration was lower than 1.7 mol·m^-3, polydispersed bubbles were generated from even the hydrophilic membrane.

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In this study, buoyancy components were introduced into turbulent fluxes such as Reynolds stress and turbulent heat fluxes, and the turbulent transport phenomena of combined convection were modeled by adding several buoyancy-induced components to the expressions of the turbulent fluxes. The turbulent transport mechanism of combined convection was also examined by applying a modified damping function, which is applicable to both the aiding and the opposing flows. The calculation target is a fully-developed turbulent combined convection between vertical smooth parallel plates, where the inertia force acts with parallel with or in opposition to the buoyant force. The wall is heated uniformly. The numerical computation was performed by combining two-equation turbulence models of different type, being applicable to both the velocity and the temperature fields. It was found from a series of computations that the model utilized simulates the heat transfer and fluid flow of turbulent combined convection physically. For industrial application, it is necessary to develop more appropriate and simpler turbulence models that are based on empirical knowledge than LES or DNS.

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Gas-liquid mixing at extraordinarily large gas flow rates was investigated for a pitched blade paddle creating upward flow in comparison with the Rushton turbine and Scaba SRGT impellers, which are commonly used for gas-liquid mixing. As a result, it was found that, by dispersing gas from a ring sparger set above the impeller against the flow created by the pitched blade paddle, flooding does not occur and the aerated power hardly decreases even at 25 vvm. The correlation of Froude number with gas flow number at the flooding-loading transition was derived for large gas flow rates.

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The power consumption in a turbulent agitated vessel with cylindrical baffles was measured for both paddle and pitched blade paddle impellers. The effect of the clearance between cylindrical baffle and vessel wall on the power consumption was examined, and it was confirmed that the power number approaches a constant value when the clearance increases. Both the power number when a cylindrical baffle is attached to the vessel wall Np_w and the power number when the cylindrical baffle is separated from the vessel wall Np_i were correlated with the impeller dimensions and the baffle conditions, and their power correlations were proposed. In addition, the effect of the number of cylindrical baffles in the radial direction on the power number was examined, and its power correlation was proposed.

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To compare the chars formed by one-stage and two-stage gasification in an entrained-flow coal-gasifier, the gasification method of entrained-flow-coal-gasifier, gasification tests were carried out using a practical gasifier with a capacity of 25 t/d coal input, in which both operations were possible.
Gasification reaction characteristics of the chars formed at high temperature and pressure were examined by thermogravimetric analysis.
As the result, the following characteristics were clarified.
1) The gasification rate of the char formed in the one-stage gasification at high temperature condition is lower than that of the char formed in two-stage gasification, which combined high-temperature and low-temperature operations.
2) The char formed in the two-stage gasification is a mixture of small particles formed at high temperature in the first stage and large particles formed at low temperature in the second stage. The gasification reaction of the char progresses in two steps, as such that both types of particle were synthesized.
3) The gasification rate of small particles within the char formed in two-stage gasification is lower than that of large particles within the same char and showed a similar value to that of the char formed in one-stage gasification.

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Steam reforming of oils produced from waste plastics such as polyolefins has been investigated with a view of producing hydrogen. Steam reforming of oils produced by decomposition of plastics at relatively low temperatures (350-450°C) was carried out at temperatures from 600 to 800°C using commercial Ni/Al₂O₃ catalysts. Gas yield, gas composition, carbon conversion and coking characteristics were examined. Oils from both polyethylene and polystyrene were well gasified with very high carbon conversions and low coking rates at temperatures higher than 700°C. The gas components were consistent with calculated equilibrium compositions. The coking rate of polystyrene oil was lower than that of polyethylene oil, and the coking rate was the lowest at the temperature of 800°C.

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A three-dimensional simulation method based on the Monte Carlo algorithm for the formation of microstructures in ceramics was proposed to control the microstructures in the sintering process. A method that takes into account real time in considering the diffusion rate as a microscopic rate constant can be used to discuss quantitatively the relation between the evolution of microstructures and the operating parameters during sintering, though the general Monte Carlo algorithm can not include time as a parameter.
The simulation results from the sintering behavior of the alumina particles consisting of grains, pores and grain-boundaries clearly illustrated the sintering process that densifies with grain growth and migration of grain-boundary. The validity of the proposed method which relates real time and Monte Carlo Step was confirmed by the agreement of the simulated values, which were calculated for the heating, sintering and cooling processes according to the experimental condition, with the experimental ones. It was clear quantitatively that the effects of heating rate, sintering temperature, particle size distribution and packing state of particles on the formation of microstructures with pore migration by the simulation carried out in various conditions. The information obtained from the proposed simulation method makes it possible to optimize the sintering conditions.

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Chemical absorption by aqueous solution of potassium carbonate is an excellent method for recovering CO₂ from flue gases, but it consumes a sizable amount of primary energy for heating a large amount of solvent water to recover the entrapped CO₂.
Thus, in an attempt to reduce energy consumption, potassium carbonate was supported on an activated carbon and applied to a fixed-bed operation. A previous lab-scale study showed that CO₂ absorption by activated carbon impregnated with K₂CO₃ is not influenced by moisture in feed gases. The hydrate of K₂CO₃ was held in cavities of the activated carbon, and cyclic sorption/release operations were repeated according to by the following reaction: K₂CO₃·1.5H₂O+CO₂=2KHCO₃+0.5H₂O.
In the present work, experiments employing a bench-scale column (54.5 mmφ×800 mm) were carried out to examine performances of K₂CO₃-on-activated carbon. Moist 13%CO₂ gas was supplied to 1.20 kg of K₂CO₃-on-activated carbon packed in the column to sorb CO₂, followed by flushing with steam to release CO₂ sorbed. The released gas was cooled through a heat-exchanger to condense the steam, giving CO₂ in high purity. Bench-scale behaviors of CO₂ sorption/release and of column cooling were elucidated. The energy consumption for CO₂ recovery was also estimated.

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A new technique for pulverization of ligneous biomass by using a vibration mill was developed. By this technique ligneous biomass was pulverized into micron-order particles, and its combustibility, compatibility, reactivity and extractability were improved dramatically. With conventional pulverization equipment, it is impossible to micronize wood fiber, since it is very strong, consisting of cellulose, hemicellulose, lignin. However, by using the vibration mill, it is possible not only to control the particle size and particle shape by changing the pulverization medium, but also economically to produce micron-order particles in large quantity.

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The lifespan of the oil-immersed transformers is predominantly controlled by deterioration of the insulation paper surrounding coils. The deterioration of the insulation paper is caused by the degradation of cellulose polymer due to the heat generated at the coils. The decrease of mechanical strength of the insulation paper caused by the reduction in the average degree of polymerization of the insulation paper makes it impossible to follow the deformation of the coils during operation. The present paper proposes a way to estimate the lifespan of the insulation paper based on the rate of depolymerization of cellulose polymer. The estimation takes into consideration the effect of temperature rise due to the heat generation in the transformer. The proposed method of identifying the residual lifespan of the oil-immersed transformers has proved to be valuable in devising an efficient strategy of maintenance.

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The absorption efficiency of gas desulfurization in a wet-desulfurization system was experimentally investigated using magnesite slurry (main component, magnesium carbonate). Continuous monitoring of a pilot plant for 4 months indicated that magnesite could be used as desulfurization agent when it was ground to a diameter of less than 12 μm. Operational problems did not arise in a pilot plant. Using a magnesite mineral with an average grain diameter 12 μm, a desulfurization ratio equal to or greater than 95% was achieved for a factory waste gas. The properties of magnesite were modified in order to improve the reaction ratio. It was determined that heating improved the reaction ratio. This observation can be incorporated in designing new desulfurization equipment.

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A fluidized bed reactor for hydrogen chloride removal by calcium absorbent was developed as a means to reduce hydrogen chloride concentration to less than 10 ppm in the gasification gas of the MCFC power generation system. The optimum calcium absorbents were evaluated from the chemical equilibrium and kinetics in the presence of CO₂. It was found that the selective reaction between slaked lime and hydrogen chloride took place without competitive inhibition by CO₂ at the temperature of 573 K. An absorption experiment with slaked lime in a fluidized bed reactor revealed that hydrogen chloride concentration could be reduced to less than 10 ppm until the conversion ratio of calcium reached 0.65.

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Vacuum heating separation is one of the methods for removing PCBs from electric appliances, whereby PCBs are vaporized under vacuum condition at 200°C. This method has a high removal performance without deteriorating the insulation oil, PCBs and other components of pole transformers. However, it takes a long time to detoxify pole transformers, because they are heated by radiative heat transfer in a vacuum. Previously, we reported that the heating time for vacuum heating separation was shortened by using a vibration dryer. In this study, the fundamental performance of PCB removal from various samples by the vacuum heating method was investigated. As a result, PCBs were reduced below the removal standard from copper and insulation paper. PCB concentration in the activated alumina was reduced by extending the treatment time.

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In order to obtain fundamental data for developing the recovery process of heavy metals from molten fly ash, the release of zinc and lead from the fly ash was followed under the conditions of a heating rate of 30 K/min, terminal temperatures from 873 to 1073 K and a holding time of 60 min in a nitrogen stream with the use of a fixed bed. Polyvinyl chloride or carbon powders were mixed with the ash in an attempt to accelerate the release of zinc and lead.
When a molten fly ash sample was heated at 1073 K without the additives, over 60% of the lead volatilized, but zinc did not volatilize at all. On the other hand, all of zinc and lead were released from the solid phase at the same temperature when polyvinyl chloride was added to the fly ash. XRD analysis showed that lead existed as oxides, while zinc was combined as a carbonate and an aluminosilicate in the raw fly ash. Lead and zinc were volatilized as chlorides via oxychlorides during heat treatment with addition of polyvinyl chloride. Both zinc and lead were released into the gas phase from the fly ash by heat treatment at 1073 K with addition of carbon powder.
These results suggest that the addition of polyvinyl chloride and carbon powders is very effective for volatilization of zinc and lead from molten fly ash.

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The formation of HCl from inorganic chlorides, NaCl and CaCl₂, was studied under simulated municipal solid waste incineration conditions. Experiments were conducted with NaCl and CaCl₂ particles of 75-125 μm in diameter, which were placed in a gas flow type tubular reactor in the temperature range of 623-1023 K, in an atmosphere of N₂ containing 2.5-15 vol% CO₂ and 2.5-15 vol% H₂O.
It was found that HCl was not generated from NaCl below 723 K, and that CaCl₂ started to release HCl in a CO₂-H₂O-N₂ mixed gas at around 623 K. The amount of HCl emitted from NaCl and CaCl₂ was increased with the increase in temperature as well as the concentrations of CO₂ and H₂O.
Based on a SEM/EDS observation of the distribution of C, O and Cl elements on the surface of reacted sample and the quantitative analysis of the amount of C by a CHN analyzer, it was found that NaCl reacted with CO₂ and H₂O to produce Na₂CO₃ and HCl. Similarly, HCl was emitted by the carbonation of CaCl₂ with CO₂ and H₂O to produce CaCO₃ at a temperature lower than 923 K. On the other hand, the emission of HCl from CaCl₂ occurred by the oxidation of CaCl₂ with H₂O to form CaO at a temperature higher than 923 K.

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Zeolite synthesis from the coal ash of a circulating fluidized bed combustor (CFBC) was examined in order to reuse them effectively. In this study, Zeolite Pt was successfully synthesized by hydrothermal alkali treatment following the pretreatment of ashes. The possibility of synthesizing zeolite was determined from XRD analysis, surface observation by SPM (scanning probe microscopy) and the capacity of ammonium ion adsorption

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