Showing papers on "Calcium oxide published in 2007"

Influence of Fly Ash, Lime, and Polyester Fibers on Compaction and Strength Properties of Expansive Soil

Abstract: An experimental program was undertaken to study the effects of polyester fiber inclusions and lime stabilization on the geotechnical characteristics of fly ash-soil mixtures. An Indian fly ash was mixed with expansive soil in different proportions. The geotechnical characteristics of fly ash-soil specimens, lime-soil specimens and lime-fly ash-soil specimens mixed with different proportions of randomly oriented fibers were investigated. Lime and fly ash were added to an expansive soil at ranges of 1–10% and 1–20%, respectively. Test specimens were subjected to compaction tests, unconfined compression tests and split tensile strength tests. Specimens were cured for 7, 14, and 28 days after which they were tested for unconfined compression tests and split tensile tests. Based on optimum values obtained for lime and fly ash, tests were conducted on test specimens prepared from fly ash-expansive soil- lime-fiber mixture after 28 days of curing. Samples were tested with 0, 0.5, 1.0, 1.5, and 2% plain and crimped polyester fibers by dry weight. Based on the favorable results obtained, it can be concluded that the expansive soil can be successfully stabilized by the combined action of fibers, lime, and fly ash.

Self Healing Concrete: A Biological Approach

Abstract: Concrete can be considered as a kind of artificial rock with properties more or less similar to certain natural rocks. As it is strong, durable, and relatively cheap, concrete is, since almost two centuries, the most used construction material worldwide, which can easily be recognized as it has changed the physiognomy of rural areas. However, due to the heterogeneity of the composition of its principle components, cement, water, and a variety of aggregates, the properties of the final product can widely vary. The structural designer therefore must previously establish which properties are important for a specific application and must choose the correct composition of the concrete ingredients in order to ensure that the final product applies to the previously set standards. Concrete is typically characterized by a high-compressive strength, but unfortunately also by a rather low-tensile strength. However, through the application of steel or other material reinforcements, the latter can be compensated for as such reinforcements can take over tensile forces. Modern concrete is based on Portland cement, a hydraulic cement patented by Joseph Aspdin in the early 19th century. Already in Roman times hydraulic cements, made from burned limestone and volcanic earth, slowly replaced the widely used non-hydraulic cements, which were based on burned limestone as main ingredient. When limestone is burned (or “calcined”) at a temperature between 800 and 900◦C, a process that drives off bound carbon dioxide (CO2), lime (calcium oxide; CaO) is produced. Lime, when brought into contact with water, reacts to form portlandite (Ca(OH)2) which can further react with CO2, which in turn forms back into calcite (CaCO3), or limestone, the pre-burning starting material. However, a major drawback of this non-hydraulic cement is that it will not set under water and, moreover, its reaction products portlandite and limestone are relatively soluble, and thus will deteriorate rapidly in wet and/or acidic environments. In contrast, portland cement produces, upon reaction with water, a much harder and insoluble material that will also set under water. For portland cement production a source of calcium, silicon, aluminum, and iron is needed and therefore usually limestone, clay, some bauxite, and iron ore are burned in a kiln at temperatures up to 1, 500◦C. The cement clinker produced is mainly composed of the minerals alite (3CaO.SiO2), belite (2CaO.SiO2), aluminate (3CaO.Al2O3), and ferrite (4CaO.Al2O3.Fe2O3), which all yield specific hydration products with different characteristics upon reaction with water.

Strength Characteristics of Class F Fly Ash Modified with Lime and Gypsum

Abstract: This paper presents the shear strength characteristics of a low lime class F fly ash modified with lime alone or in combination with gypsum. Unconfined compression tests were conducted for both unsoaked and soaked specimens cured up to 90 days. Addition of a small percentage of gypsum (0.5 and 1.0%) along with lime (4–10%) enhanced the shear strength of modified fly ash within short curing periods (7 and 28 days). The gain in unsoaked unconfined compressive strength ( qu ) of the fly ash was 2,853 and 3,567% at 28 and 90 days curing, respectively, for addition of 10% lime along with 1% gypsum to the fly ash. The effect of 24 h soaking showed reduction of qu varying from 30 to 2% depending on mix proportions and curing period. Unconsolidated undrained triaxial tests with pore-pressure measurements were conducted for 7 and 28 days cured specimens. The cohesion of the Class F fly ash increased up to 3,150% with addition of 10% lime along with 1% gypsum to the fly ash and cured for 28 days. The modified fly a...

Carbon dioxide sequestration materials and processes

Abstract: The disclosure provides methods and systems for sequestering and/or reducing carbon dioxide present in an industrial effluent fluid stream containing carbon dioxide. A scrubbing material comprising a first component, a second component (distinct from the first component), and preferably water, is contacted with the effluent fluid stream. The first component comprises a source of calcium oxide and a source of alkali metal ions. The second component comprises a slag having one or more reactive silicate compounds. Methods of reducing carbon dioxide from exhaust generated by combustion sources, lime and/or cement kilns, iron and/or steel furnaces, and the like are provided. Carbon dioxide emission abatement systems are also disclosed. Methods of recycling industrial byproducts are further provided.

Simultaneous removal of SO2 and trace As2O3 from flue gas: mechanism, kinetics study, and effect of main gases on arsenic capture.

Abstract: Sulfur dioxide (SO2) and trace elements are pollutants derived from coal combustion. This study focuses on the simultaneous removal of SO2 and trace arsenic oxide (As2O3) from flue gas by calcium oxide (CaO) adsorption in the moderate temperature range. Experiments have been performed on a thermogravimetric analyzer (TGA). The interaction mechanism between As2O3 and CaO is studied via XRD detection. Calcium arsenate [Ca3(AsO4)2] is found to be the reaction product in the range of 600−1000 °C. The ability of CaO to absorb As2O3 increases with the increasing temperature over the range of 400−1000 °C. Through kinetics analysis, it has been found that the rate constant of arsenate reaction is much higher than that of sulfate reaction. SO2 presence does not affect the trace arsenic capture either in the initial reaction stage when CaO conversion is relatively low or in the later stage when CaO conversion is very high. The product of sulfate reaction, CaSO4, is proven to be able to absorb As2O3. The coexisting ...

Kinetics and Structural Characterization of Calcium-Based Sorbents Calcined under Subatmospheric Conditions for the High-Temperature CO2 Capture Process

Abstract: The influence of several process parameters on the calcination of a naturally occurring limestone and a precipitated mesoporous calcium carbonate (CaCO3) sorbent structure to calcium oxide (CaO) is detailed in this study. CaCO3 calcination is an integral part of a multicyclic carbonation−calcination reaction (CCR) process that separates carbon dioxide (CO2) from high-temperature gas mixtures into a pure CO2 stream. Maintenance of high sorbent reactivity over repeated CCR cycles reduces the capital and operating cost of the CCR process. A lower calcination temperature, required to maintain high sorbent reactivity, reduces the calcination rate of CaCO3. This study investigates various process conditions such as subatmospheric calcination, sorbent dispersion in a rotary calciner, use of a high thermal conductivity sweep gas, etc. in enhancing the calcination rate at lower calcination temperatures. The high-temperature gas−solid carbonation studies of the resulting CaO sorbent prove the necessity to maintain ...

Mechanism of the carbonatation shrinkage of lime and hydrated cement

Abstract: Carbonatation of hydrated lime compacts produces shrinkage and changes in mechanical properties comparable with those found in similarly treated compacts of bottle-hydrated cement and samples of hardened Portland cement paste. From experimental results obtained with the simpler lime system a mechanism for carbonatation shrinkage is proposed that postulates a through-solution reaction and induced cycles of wetting and drying. Experiments on compacts of bottle-hydrated cement show that carbonatation of the ‘combined lime’ is at least as rapid and extensive as the carbonatation of the ‘free lime,’ and that contrary to current opinion the former reaction results in even greater carbonatation shrinkage. The mechanism for carbonatation shrinkage of this system is considered to be connected with dehydration and polymerisation of the hydrous silica product of carbonatation.

Lime and Limestone

Abstract: The article contains sections titled: 1. Introduction 2. Limestone 2.1. Physical and Chemical Properties 2.2. Formation and Occurrence 2.3. Production 2.4. Uses and Specifications 3. Quicklime 3.1. Physical and Chemical Properties 3.2. Raw Materials 3.2.1. Limestone 3.2.2. Fuel 3.3. Production 3.3.1. Calcination 3.3.2. Lime Kilns 3.3.3. Quicklime Processing 3.4. Uses and Specifications 4. Hydrated and Slaked Lime 4.1. Physical and Chemical Properties 4.2. Raw Materials 4.2.1. Raw Materials for Hydrated Lime 4.2.2. Raw Materials for Slaked Lime 4.3. Production 4.3.1. Normal Hydration Process 4.3.2. Pressure Hydration Process 4.3.3. Production of High Surface Area Hydrated Limes 4.3.4. Normal Slaking Process 4.3.5. Production of Ultrafine Milks of Lime 4.4. Uses and Specifications 4.4.1. Uses 4.4.2. Specifications 5. Environmental Protection 5.1. General 5.2. Dust Emission 5.3. Gaseous Emissions 5.4. Noise and Vibration 6. Physical Testing and Chemical Analysis 6.1. Sampling and Sample Preparation 6.2. Physical Testing 6.3. Chemical Testing and Analysis 7. Storage and Transportation 8. Economic Aspects 9. Toxicology and Occupational Health 9.1. Toxicology 9.2. Occupational Health Limestone (principally calcium carbonate) is a naturally occurring mineral and is found widely throughout the world. It is mainly used for road construction, in the production of concrete and as a structural fill. It is also the principal raw material for the production of cement, quicklime, and numerous other products. Quicklime (principally calcium oxide) is produced by the thermal decomposition of limestone at temperatures above 900°C. About half of the quicklime made is reacted with water to produce calcium hydroxide (in the form of milk or lime putty). Lime products are generally the most readily available and most cost-effective alkaline chemicals and are used in a wide variety of industrial processes. In many countries, the largest use is for the production of iron and steel, followed by building and construction, environmental protection, and the chemical industry. Hydraulic lime is a traditional product used in building, especially as a binder in mortars. The main environmental issues associated with the production of lime and limestone products are emissions to air and energy consumption.

Development of high-volume low-lime and high-lime fly-ash-incorporated self-consolidating concrete

Abstract: The current article presents an experimental study on the use of two types of fly ash (low lime and high lime) as mineral admixtures in producing self-consolidating concrete (SCC) with the objective of assessing the effects of both types of fly ash on the fresh and hardened properties of SCCs. Within the scope of an experimental programme, SCCs were prepared by keeping the total mass of cementitious materials constant at 500 kg/m3, in which 30, 40, 50, 60 or 70% of cement, by mass, was replaced by high-lime and low-lime fly ash. The workability-related fresh properties of SCCs were observed through slump flow time and diameter, V-funnel flow time, L-box height ratio, GTM sieve stability test and the rheological parameters (relative yield stress and relative plastic viscosity). Setting times and temperature rise of SCCs were also determined as part of fresh properties. The hardened properties that were monitored for a year included the compressive strength, ultrasonic pulse velocity, drying shrinkage and c...

Reactivity of lime and related oxides. I. Production of calcium oxide

Abstract: The calcination of calcium hydroxide and of calcium carbonate (precipitated or prepared from calcium oxalate monohydrate) has been studied by determining the changes occurring in the specific surface and lattice structure during each decomposition in vacuo or in air at a series of temperatures up to 900° or 1000°c. In parallel with earlier observations on calcium hydroxide, the decomposition of the calcium carbonate results in a several-fold increase in specific surface which is ascribed to the activation of the newly-formed calcium oxide when it recrystallizes from a pseudo-lattice of calcium carbonate to very small individual crystals having a more stable lattice structure. The preliminary decomposition of the calcium oxalate, particularly in vacuo at about 450°, produces samples of calcium carbonate of much higher specific surface than that of the precipitated form, but they tend to sinter considerably at higher temperatures before decomposing to calcium oxide. Further calcination after complete decomposition always causes sintering of the calcium oxide, the extent of which is enhanced by increased temperature whether in vacuo or in air.

Reactivity of lime and related oxides. II. Sorption of water vapour on calcium oxide

Abstract: Calcium oxide samples differing widely in surface activity (specific surface 1 to 100 m.2g.−1) have been hydrated by exposure to water vapour at room temperature. Although the rates of hydration differ considerably, each sample takes up in chemical combination a stoicheiometric quantity of water but, in further uptake of water by the newly formed calcium hydroxide by physical adsorption, the isotherm gives no ‘stepwise’ evidence of formation of the alleged hemi-hydrate, Ca(OH)2,0.5H2O. Changes in surface area and lattice structure during hydration indicate that the most active limes become aged (agglomerated) rapidly in the presence of water vapour, and must be hydrated at very low relative pressures to maintain the same number of crystallites; limes of moderate activity can be hydrated without ageing; the least active limes undergo hydration only when the number of crystallites increases, the necessary fission of the original crystallites being accompanied by slow rates of hydration. Progressive changes in surface area during hydration are related to the volumes of the oxide and hydroxide on the basis that the reaction proceeds inwards from the outside of each particle by an advancing interface mechanism.

On the formation of cementitious c-s-h nanoparticles: a computational approach

Abstract: Much of the existing knowledge on the nanostructure of cementitious Calcium Silicate Hydrate (C-S-H) nanoparticles has been gained from structural comparisons with crystalline calcium silicate hydrates. In fact, several models [1-5] have been proposed so far that draw structural analogies with tobermorite and jennite crystals and/or with distorted semi-crystalline variations of them (the so called C-S-H (I) and C-S-H (II) phases respectively). From these models, CS-H gels can be approximately viewed as layered structures, in which calcium oxide sheets are ribbed on either side with silicate chains, and free calcium ions and water molecules are present in the interlayer space (see Figure). 1.4nm-Tobermorite Jennite

Lime characterization as a food additive

Abstract: This article discusses the use of various measurement techniques for physico-chemical and mineralogical analyze of lime for its safe use as a food additive. Two types of samples were taken from a mine in Queretaro, Mexico, and measurements were made to determine Pb (CaO—0.0012 mg/kg, Ca(OH)2—0.0527 mg/kg), As (CaO—0.0290 mg/kg, Ca(OH)2—0.0849 mg/kg), F (under the quantification limit), and V (CaO—1.9068 mg/kg, Ca(OH)2—4.3403 mg/kg). The samples were within the safety limits for human consumption. It is suggested that similar analysis be carried out on commercially marketed lime products.

Strength and Slake Durability of Lime Stabilized Pond Ash

Abstract: Pond ash, after adequate stabilization, may be suitable for various engineering applications. The effects of lime stabilization on the strength and durability aspects of a class F pond ash, with a lime constituent as low as 1.12%, are reported. Lime contents of 10 and 14% were used, and the samples were cured at ambient temperature of around 30°C for curing periods of 28, 45, 90, and 180 days. Samples were subjected to unconfined compression tests as well as tests that are usually applied to rocks such as point load strength tests, rebound hammer tests, and slake durability tests. Unconfined compressive strength (UCS) values of 4.8 and 5.8 MPa and slake durability indices of 98 and 99% were achieved after 180 days of curing for samples stabilized with 10 and 14% lime, respectively. Good correlations, that are particularly suitable for stabilized materials of low density and low strength, have been derived for strength parameters obtained from UCS tests, point load strength tests, and Schmidt rebound hammer tests, and also between UCS and slake durability index.

Rapid Chemical Stabilization of Soft Clay Soils

Abstract: Since World War II, the military has sought methods for rapid stabilization of weak soils for support of its missions worldwide. Over the past 60 years, cement and lime have been the most effective stabilizers for road and airfield applications, although many nontraditional stabilizers also have been developed and used. The most effective stabilizer to increase the strength of two soft clay soils within 72 h for contingency airfields to support C-17 and C-130 aircraft traffic needed to be determined. The treatment of one clay with cement resulted in relatively high unconfined compressive strengths (UCS), whereas treating the same clay with quicklime and calcium carbide resulted in lower UCS. The treatment of another clay with higher plasticity resulted in similar UCS for cement, quicklime, and calcium carbide. Secondary stabilizers, including sodium silicate, superabsorbent polymers, a superplasticizer, and an accelerator, were ineffective in increasing the UCS of a soil treated with cement, quicklime, or...

A modified solvay process, and uses thereof for processing co2-containing gas streams and for desalination

Abstract: There is disclosed a method for processing an input gas stream, characterised by the following steps of: a) reacting the carbon dioxide of the input gas stream with an alkaline solution based on ammonia, for the formation of ammonium carbonates; b) reacting said ammonium carbonates from step a) with a saline solution for forming chemical products including alkaline metal carbonate and ammonium chloride; and c) processing said ammonium chloride from step b) by decomposition to form ammonia and metal chloride and/or hydrochloride acid; and d) step c) is implemented by using calcium oxide (CaO) to generate calsium chloride as said metal chloride, and/or by using magnesium oxide (MgO) to generate magnesium chloride as said metal chloride. Preferably the method is used in a combined process for removing carbon dioxide from combustion gas and desalination of water.

Digestibilidade da cana-de-acúcar hidrolisada, in natura e ensilada para bovinos

Abstract: The objective of the present study was to determine in vitro dry matter ruminal digestibility (IVDMD), neutral detergent fiber (IVNDFD), acid detergent fiber (IVADFD) and lignin (IVLD) in two varieties of sugarcane (IAC 862480 and RB 835453), hidrolised with zero; 0.5 and 1.0% of the lime, during three hours, in natura and ensiled forms. The treatments with three replications, in scheme factorial design were applied. There was no influence of the different lime levels, but the digestibility in the 0; 0.5 and 1.0% of the lime were equal statistically (P>.05). The IVDMD, IVDFDN and IVDFDA were greated in IAC 862480 variety in the lime levels utilized. Despite the variation found in the digestibility of some components, both in natura with 0.5% and silagem with 1.0% of sugarcane are indicated in dairy and beef cattle feeding program. KEY WORDS: Bovine, calcium oxide (lime), ensilage, in vitro.

A preliminary study of processing seafood shells for eutrophication control

Abstract: Shells from the seafood processing industry in New Zealand are currently an under-utilized waste resource. In this study we investigate the processing conditions required for the creation of calcium oxide (lime) from green-lipped mussel (Perna canaliculus) and pacific oyster (Crassostrea gigas) shells. Lime is commonly used in wastewater treatment for the removal of phosphorous compounds from water, thus providing a means of eutrophication control. Mussel and oyster shells were processed in a horizontal tube furnace at various temperatures (650–800 °C) in both air and nitrogen environments. From X-ray diffraction (XRD) and weight-loss measurements, the extent of limestone calcination was found to increase with increasing furnace temperature for both shell species and furnace atmospheres. Analysis showed that the lime was present as a layer on the surface of the shell particles. From scanning electron microscope (SEM) images, significant changes in the surface morphology of the raw shells were observed as a result of heat treatment in both air and nitrogen atmospheres. Preliminary testing of shells heat-treated in both air and nitrogen atmospheres indicated that both types of shell removed about 90% of phosphates in water within 30 min, whereas up to 40% of phosphates were removed with untreated shells. Our results for heat-treated oyster shell differ slightly with studies in the literature, which report an absence of compositional and structural changes in an air atmosphere. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.

On the thermal decomposition of dolomite. IV.thermogravimetric investigation of the dolomite decomposition

Abstract: The thermal decomposition of dolomite at various constant temperatures and carbon dioxide pressures has been investigated by the ‘loss-of-weight method.’ Depending on these conditions, dolomite can be decomposed either stepwise to magnesium oxide and calcium carbonate (‘half-burnt dolomite’) with subsequent dissociation of calcium carbonate, or in a single stage to both magnesium oxide and calcium oxide. It is most significant that partial decomposition is independent of the carbon dioxide pressure occurring within the same narrow temperature range, about 680°. If the ambient carbon dioxide pressure is lowered below the dissociation pressure of calcite corresponding to this temperature, then decomposition curves are shifted to lower temperatures. The second stage of the step-wise decomposition occurs at increasingly higher temperatures with increased carbon dioxide pressure. However, complete decomposition becomes progressively more difficult owing to remaining calcium carbonate. A reaction mechanism of the thermal decomposition of dolomite is propounded based on these thermogravimetric results in conjunction with thermodynamic calculations and X-ray studies.

Apatite group minerals : solubility and environmental remediation

Abstract: Publisher Summary This chapter focuses on the solubility and environmental remediation of the apatite group of minerals. Remediation processes based on chemical treatments destroy contaminants or convert them into less environmentally hazardous forms. The apatite group minerals are hexagonal or pseudohexagonal monoclinic arsenates, phosphates, and vanadates of the general formula A 5 (XO 4 ) 3 Z, where A = Ba, Ca, Ce, K, Na, Pb, Sr, and Y; X = As, P, Si, and V; and Z = F, Cl, O, OH, and H 2 O. Solids belonging to the apatite group have been investigated as host materials for long-term immobilization of a large number of stable and radioactive elements including cadmium, copper, lead, nickel, uranium, zinc, iodide, and bromide. The apatite group of minerals displays a large solubility range, with calcium-bearing species being more soluble than their lead analogues. In situ metal immobilization employing phosphate is a cost-effective and environment-friendly technique of less disruptive nature than other remediation techniques such as soil removal, washing, or leaching. The treatment of waters with calcium oxide or hydroxide can also precipitate dissolved arsenate. To attain a total dissolved arsenic level lower than the maximum permissible concentration for total arsenic in potable water (0.010 mg/L arsenic), it is necessary to have a pH higher than 12.5, which poses other environmental problems. Under these conditions, calcium carbonate is thermodynamically stable in the solid phase if ambient surface conditions are maintained. Transformation of calcium arsenates into calcium carbonate re-releases arsenic into the environment.

Process for preparing concentrated polyunsaturated fatty acid oil

Abstract: The present invention provides a process for concentrated PUFA oil, characterized in that alcoholysis reaction using lipase is carried out in the presence of a small amount of water and at least one compound as an additive selected from magnesium oxide, magnesium hydroxide, calcium oxide and calcium hydroxide, and then separation is conducted to obtain a glyceride fraction.

Production method of dental ceramics material

Abstract: To make a color tone similar to that of dentin of a tooth at a low cost without discoloration when baking, a dental ceramics material is produced by: mixing a pink coloring agent and a yellow coloring agent with zirconium oxide containing a stabilizer while having a mixing ratio of 0001 to 5 wt % respectively; and baking it, where the pink coloring agent is obtained by dissolving manganese oxide in aluminum oxide as a solid solution, the yellow coloring agent is obtained by dissolving vanadium oxide in zirconium oxide as a solid solution, the zirconium oxide contains 01 to 30 wt % aluminum oxide if necessary, the stabilizer is one or more kinds selected from a group including yttrium oxide, magnesium oxide, calcium oxide, and cerium oxide, and the content thereof is preferably 3 to 7 wt %

Process for producing super-activated carbon

Abstract: A process of preparing super activated carbon includes such steps as mixing hydroxide of alkali metal with carbon material, activating in a sealed furnace to obtain coarse product and tail gas, washing the coarse product with water, drying to obtain finished product, washing said tail gas with solvent, adding calcium oxide (or hydroxide), stirring while reacting to transform the carbonate of alkali metal to hydroxide and calcium, depositing, washing to obtain calcium carbonate, and cyclic use of said hydroxide.

Reactivity of lime and related oxides. VII crystal size variations in calcium oxide produced from limestone

Abstract: The calcination of limestone has been studied by determining the changes in the specific surface and crystallite size of the calcium oxide produced when limestone spheres are calcined for various times at each of a number of fixed temperatures either in vacuo or in air. At lower temperatures (below about 900°) as in rotary-kiln lime-burning, the crystallite size of the calcium oxide is determined more by the mode of recrystallisation of the oxide from its CaCO3-like transition structure than by the sintering of the recrystallised oxide. Since the decomposition rate of the limestone progressively diminishes, the rate of nucleation in the recrystallisation of the oxide becomes lower, so that the crystallite size of the oxide formed in the outer sections of the spheres tends to be less than that formed in the inner sections. The differences in size are minimised if the evolved carbon dioxide is not quickly removed, for it enhances sintering of the calcium oxide. At higher temperatures (above about 900°), as in conventional lime-kilning, the crystallite size of the calcium oxide depends mainly on the rate of sintering. Rapid decomposition of the limestone at these temperatures therefore produces lime more homogeneous in surface activity even after only short calcinations, since all of the lime crystallites in each sample still have approximately equal times in which to sinter; the crystallite size of the lime then becomes practically independent of that of the original calcium carbonate.

Simultaneous removal of SO2 and NO by low cost sorbent-catalysts prepared by lime, fly ash and industrial waste materials

Abstract: The potential of the sorbent-catalysts prepared from three low cost materials, i.e., the lime, fly ash and some industrial waste material containing iron oxide, have been investigated for simultaneous removal of SO2 and NO x from flue gas in the temperature range 700–850 °C. NH3 was chosen as the reducing agent for NO reduction in this study. Experimental results showed that SO2 and NO could be simultaneously removed efficiently in the absence of O2 at the temperature window of 700–800 °C. The effect of product layer generated from SO2 removal on NO removal was not obvious. NO removal efficiency was strongly inhibited by O2, which was attributed to the partial oxidation of NH3 to NO over the sorbent-catalysts in the presence of oxygen. Neither NO2 nor N2O by-product was detected both in the absence and presence of O2. Three routes were suggested to overcome the negative effect of O2.

Preparation of Fully Cubic Calcium-Stabilized Zirconia With 10 mol% Calcium Oxide Dopant Concentration by Microwave Processing

Abstract: A novel, fast, and cheaper method has been developed for the synthesis of fully cubic calcium-stabilized zirconia (ZrO2) of composition Ca0.1Zr0.9O1.9 by dissolution of calcium oxide in monoclinic ZrO2 for the first time using microwave energy. In this process, the precursors have been prepared by the mixed-oxide method taking the constituents in their stoichiometric ratio. The samples have been allowed to absorb microwave radiation in the presence of a polymeric susceptor. The susceptor absorbs the microwave radiation at room temperature and increases the temperature of the sample, where it starts interacting with microwave radiation. The susceptor burns off at a higher temperature without reacting with the sample. The cubic Ca0.1Zr0.9O1.9 has been prepared at a temperature of 1100°C within 5 min.

Polyaluminum calcium hydroxychlorides and methods of making the same

Abstract: A process is provided for the preparation of a novel polyaluminum calcium hydroxychloride composition of enhanced efficiency for water treatment, paper sizing, and antiperspirant applications. The polyaluminum calcium hydroxychloride compositions are prepared via the acidification of higher basicity reaction products to form mid-to-high basicity final products. Two methods are provided for the preparation of higher basicity products, contemplated in the first, and an aqueous acid solution, such as hydrochloric acid, aluminum chloride, or a mixture thereof, is mixed with a strong alkaline calcium salt such as calcium oxide or calcium carbonate and aluminum powder at temperatures greater than 60°C. In a second method, bauxite, aluminum hydrate, or aluminum metal, and calcium aluminate are mixed with hydrochloric acid and are reacted at high temperatures and/or elevated pressures for a certain period of time whereby, when the reaction is complete, the mixtures are filtered to obtain clear solutions. The final PAC-Ca solutions may be dried to powder to have a wide range of basicities from about 40% to about 80%. At lower basicities, the polyaluminum calcium hydroxychloride sales are used preferably as antiperspirants, while at higher basicities, the solutions are used preferably as water treatment chemicals.