Top PDF Process for high temperature gaseous reduction of calcium sulfate

Process for high temperature gaseous reduction of calcium sulfate

Process for high temperature gaseous reduction of calcium sulfate

proportioned air and natural gas into and through the bed to fluidize the finely divided calcium sulfate and to heat to reaction temperatures. The natural gas is only partially burned within the bed, thereby also producing reducing quantities of CO and H2. In a preferred embodiment, the calcium sulfate feed is preheated by direct contact with the gas product to recover part of the heat therefrom, and the gas product of reduced heat content is then subjected to indirect countercurrent heat exchange with the air being supplied to the reaction bed.

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Recovery of Calcium Carbonate and Calcium Sulfate from Waste Gypsum

Recovery of Calcium Carbonate and Calcium Sulfate from Waste Gypsum

petro coke combustion in a circulating fluidized bed combustor (CFBC) of refinery. The ratio of fly ash to bottom ash in the CFBC desulfurization process is about 7:3. However, they were mixed and discharged without separation; the composition was greatly different according to the discharge position and operating conditions. In order to observe the changes in composition of the WDG by season, boiler type, calcium carbonate characteristics and operating variables, we analyzed 7 times and the average composition of the samples is shown in Fig. 1. As shown in Fig. 1, the mean (standard deviation) of CaO, CaSO 4 ,
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Immersion Induced Changes in Structure and Properties of a Calcium Sulfate Cement

Immersion Induced Changes in Structure and Properties of a Calcium Sulfate Cement

This research was devoted to the investigation of changes in structure and properties of a calcium sulfate hemihydrates (CSH) cement immersed in Hanks ’ solution for different periods of time. XRD patterns indicated a quick phase change (a hydration process) of CSH into calcium sulfate dihydrate (CSD) after the cement powder was mixed with the setting solution. After the hardened cement was immersed in Hanks ’ solution for 1 d, CSD became the dominant phase. The long-term (up to 30 d) pH value of the Hanks ’ solution wherein the cement was immersed remained in the range of 6 ­ 7. The hardened cement gradually lost its weight and increased its porosity level with immersion time. When immersed for 1 d, the average compressive strength (CS) value of the cement reached its maximum value. After 30 d, the compressive strength (CS) value of the cement still remained > 25 MPa. SEM showed that, after being immersed for 30 d, numerous large, faceted CSD crystals were observed throughout the sample. Cytotoxicity test indicated that the present cement is a biocompatible implant material. [doi:10.2320 / matertrans.M2011362]
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Effect of Gamma Radiation on Properties of a Calcium Phosphate Calcium Sulfate Composite Cement

Effect of Gamma Radiation on Properties of a Calcium Phosphate Calcium Sulfate Composite Cement

The early stage (during setting process) variation in pH value was determined using a pH meter (Suntex Instruments SP-2300, Taipei, Taiwan) that was embedded in the cement paste immediately after the powder and setting liquid were mixed. The first reading was taken at 2 min after mixing. Readings were taken every 1 min until 30 min post-mixing. The pH value of the Hanks ’ solution wherein the cement paste sample was immersed for one day was monitored using the same pH meter.

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Optimization of Calcium Sulfate Precipitated in the Laminar Flow Pipe Through Response Surface Modeling of Temperature, Ca2+ Concentration and Citric Acid Additives

Optimization of Calcium Sulfate Precipitated in the Laminar Flow Pipe Through Response Surface Modeling of Temperature, Ca2+ Concentration and Citric Acid Additives

bulk, once the supersaturated solution increases, or corrosion by-products are formed at a second stage sediment out. Moreover, scaling in pipe system may be imputed by a combination of these two pathways and also kept in line by the process condition in pipes. Correspondingly, the mitigation of mineral scaling may be performed by the utilization of chemicals and antiscalants for inhibiting nucleation, crystal growth or both. For instance, polyacrylic acid, polyacrylamide, polymaleic anhydride, and polyphosphates are commonly employed 9-10 . At that place are likewise
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Microscopic studies of calcium sulfate crystallization and transformation at aqueous organic interfaces

Microscopic studies of calcium sulfate crystallization and transformation at aqueous organic interfaces

that parts-per-million amounts of condensation water, 43 or even seven monolayers of water, 44 can induce this process. Both optical and interferometry images, as well as crystal growth videos, provide significant evidence for the dissolution of gypsum needles, shown through a decrease in length, as the dissolution flux is higher at the ends of each needle (see Figure 8a). This strongly indicates the presence of a thin interfacial layer, which must have some aqueous character, to allow the dissolution of this hydrated phase. This suggestion is reasonable given the existence of thin water films on surfaces subjected to atmospheric conditions, with thicknesses of approximately five monolayers of water. 45 Thus, the conditions in this thin interfacial film, which are largely different to those of bulk aqueous solutions, appear to aid gypsum dissolution and anhydrite precipitation. However, this thin interfacial layer is also likely to contain small residues of hexane solvent, and base oil from the detergent formulation, and thus would have a rather complex structure with a thickness greater than a few monolayers.
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Respiratory Morbidity Associated with Long Term Occupational Inhalation Exposure to High Concentrations of Hydrated Calcium Sulfate Dust

Respiratory Morbidity Associated with Long Term Occupational Inhalation Exposure to High Concentrations of Hydrated Calcium Sulfate Dust

sulfate and 21% water [1]. Gypsum is obtained from heating process of gypsum rock [2]. Calcium sulfate dihy- drate is a colorless, solid inorganic substance with hygroscopic properties [3]. The production sources of this substance vary and it may be contaminated with quartz [4]. Workers employed in the processing of gypsum rock may be exposed to high atmospheric concentrations of gypsum dust via inhalation, ingestion, skin and/or eye contact [5]. It is classified as a nuisance dust [4]. Limited information exists as to the respiratory effects of gyp- sum dust. This, presumably, is due to the general belief that the substance is harmless due to its short half-life (in the order of a few weeks or, at most, months) [4] [6] [7].
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Preparation of High Percentage α Calcium Sulfate Hemihydrate via a Hydrothermal Method

Preparation of High Percentage α Calcium Sulfate Hemihydrate via a Hydrothermal Method

as starting materials to synthesize high percentage α -HH via a hydrothermal method. The median particle sizes of the three types of DH were 946.7 µm, 162.4 µm and 62.4 µm, respectively. They were named as DH-L, DH-M and DH-S in this paper. The particle size distribution, morphology and phase composition of the raw materials were evaluated before synthesis. SEM results revealed that DH-L consisted of irregu- lar large particles, while DH-M and DH-S were composed of plate-like particles with some small ones. High percentage HH can be obtained with proper synthesis para- meters by hydrothermal method, specifically, 105˚C/90 min for DH-L (achieving 98.8% HH), 105˚C/30 min for DH-M (achieving 96.7% HH) and 100˚C/45 min for DH-S (achieving 98.4% HH). All the synthesized HH were hexagonal columns, de- monstrating that they were α -phase HH. The particle size and morphology of start- ing material (DH) have significant influences on not only the rate of phase transition but also the morphology of the synthesized α -HH. Calcium sulfate dihydrate cements were prepared by the synthesized α -HH. The highest compressive strength of cal- cium sulfate dihydrate cement was 17.2 MPa. The results show that the preparation of high percentage α -HH is feasible via a hydrothermal method and the process can be further scaled up to industrial scale production.
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Dynamic Thermo-Physical Characteristics of High Temperature Gaseous Hydrocarbon Fuel Thermal Power Generation for Regeneratively Cooled Hypersonic Propulsion System

Dynamic Thermo-Physical Characteristics of High Temperature Gaseous Hydrocarbon Fuel Thermal Power Generation for Regeneratively Cooled Hypersonic Propulsion System

During the scramjet normal working conditions, the flight Mach number increases gradually with the acceleration of the aircraft. Therefore, the dynamic response characteristics of the thermodynamic power generation system will be discussed when the flight Mach number changes with given acceleration. In order to discuss the influence of acceleration on cooling and expansion TPG system characteristics, the total increase of flight Mach number is 0.2, while the acceleration varies from 0.08g to ∞ (which is also considered as Mach number step variation). As a result, dynamic characteristics of the outlet fuel temperature for the cooling channel and the turbo-pump rotation speed show the same trends with flight Mach number step change conditions. When the acceleration increases, the outlet fuel temperature increases, and the positive overshoot of fuel temperature is larger, which is shown in Figure 7. The reasons at acceleration step change conditions are the same with flight Mach number step change conditions. What is different is that while the acceleration is larger, the dynamic time of outlet fuel temperature is shorter. That is because the larger acceleration causes shorter Mach number increasing time when the Mach number increasing amount is constant. Although larger acceleration provides shorter dynamic time, it causes positive overshoot of fuel temperature, which may lead to over temperature risk of combustor wall.
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Numerical Study of Reduction of NOx Emission by High Temperature Air Combustion Technology

Numerical Study of Reduction of NOx Emission by High Temperature Air Combustion Technology

air combustion (HTAC) technology was done. The basic concept of the regenerative burner including heating a diluting of fresh air by flue gas was implemented in a two-dimensional furnace model. Governing equations in conjunction with a turbulence model and an overall chemistry model were solved using an implicit numerical scheme. Effect of temperature and O 2 concentration of preheated

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High-temperature Corrosion Investigation of the Inconel-600 in Molten Sulfate/Vanadate Mixtures Using Electrochemical Techniques

High-temperature Corrosion Investigation of the Inconel-600 in Molten Sulfate/Vanadate Mixtures Using Electrochemical Techniques

mixtures was made from analytical grade reagents. Taking into account the initial area of the specimens, an amount of 2000 mg/cm 2 of the corrosive salts was introduced into a 30 ml silica crucible, allowing a melt depth of about 3 cm. Afterwards, the crucible was placed inside an electrical tubular furnace to reach the test temperature of 700 °C, which was constantly monitored during the tests using a K-type thermocouple and controlled to ± 4 °C with respect to the test temperature. The crucible containing the solid corrosive salts was replaced for every new test. It is important to note that in a real high temperature corrosion process, the alloys are in contact to a thin molten salt layer and a corrosive gas environment; while the experimental procedure carried out in this work, the specimens were exposed in a deep melt with static air, therefore, the experimental conditions and corrosion rates obtained are not representative of those present in power generation boilers [15]. However, bulk molten salt tests are considered a viable experimental procedure for the evaluation of corrosion performance of metallic materials. The size and preparation of the samples, as well as the preparation of the corrosive mixtures were the same for all the electrochemical tests.
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Inhibitory Effect of Copper Precipitates on Anaerobic Biological Sulfate Reduction

Inhibitory Effect of Copper Precipitates on Anaerobic Biological Sulfate Reduction

Biological sulfate reduction produces sulfide that is used to precipitate copper in the single or two stage processes being investigated in the current study. Depending on the matrix, it is possible that additional copper may be precipitated due to the presence of other ions in solution. Therefore, in order to determine the effectiveness of the processes in their ability to precipitate copper or to compare them, it is important to determine the amount of copper precipitated with the sulfide produced. Precipitation of copper in the form of sulfide was evaluated for both single stage and two stage metal removal concept. For the single stage process, reactor HR1 was fed with different concentration of copper and the amount precipitated with sulfide inside the reactor was evaluated. The potential for the residual sulfide, if any, in HR1 effluent to precipitate copper was evaluated using batch chemical precipitaton experiments as described in Section 3.1.2.2b. The ability of the sulfide produced in stage 1 (HR2) of the two stage process to precipitate copper in stage 2 (chemical precipitation) was evaluated by running batch experiments as described in Section 3.1.2.2b. Efficiencies of copper sulfide precipitation for both concepts were estimated and compared together. The precipitates resulted from the precipitation experiments were also characterized using Scanning Electron Microscope and Energy Dispersive Spectroscopy (SEM/EDAX) and X Ray Diffraction (XRD) to identify the other copper precipitate species that were possibly be formed. The visual MINTEQ model was also applied as a powerful speciation model to simulate the precipitation experiments to further evaluate the precipitation process.
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Sulfate Assimilation Mediates Tellurite Reduction and Toxicity in Saccharomyces cerevisiae

Sulfate Assimilation Mediates Tellurite Reduction and Toxicity in Saccharomyces cerevisiae

- enomethionine and telluromethionine, respectively, which, fol- lowing replacement of methionine during protein biosynthesis, may cause protein inactivation. To investigate Se-methionine and Te-methionine formation as potential toxicity mechanisms for Se(IV) and Te(IV), we screened gene knockout mutants with aberrations in Te phenotypes following selenomethionine exposure. Telluromethionine is unstable and rapidly decom- poses, impeding phenotypic screening. No quantifiable Se(0) accumulation was observed in selenomethionine-exposed cells, suggesting that the conversion of Se(IV) to selenomethionine is unidirectional (Fig. 5). However, comparing gene knockout tolerance traits, we found a strong overlap of Se(IV), Te(IV), and selenomethionine, showing that toxicity and detoxifica- tion mechanisms are partially shared by these compounds (Fig. 4). Specifically, loss of MET genes conferred tolerance to Se(IV), Te(IV), and selenomethionine whereas loss of HOM6 or MUP1 resulted in sensitivity, suggesting a similar role for the sulfate assimilation system in Se(IV), Te(IV), and selenomethionine toxicity.
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Flammable mixture formation in a transient gaseous fuel injection process

Flammable mixture formation in a transient gaseous fuel injection process

4.43: Angular momentum change time at different tumble ratios in cylindrical chamber with moving piston.. Chapter 5[r]

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HTHW temperature reduction

HTHW temperature reduction

The CIP sets in the bottling department are used to clean only the fillers. Giobbe (Sidel) and Reinhard (Software engineer) told me that it’s difficult to heat up the filler so quickly; it’s very heavy and will take some time to heat up in any case. One option is increase the flow of hot water and CIP fluid through the filler. This can be done by adding more plates to the exchanger and reducing pressure drop or by increasing pumping power. Otherwise the temperature of the CIP and hot water streams can be increased further above 88 degrees but there is an upper limit of 95 degrees with the filler. There is some space to improve and increase heating up time for sure. Although the manufacturers (Sidel) told me it is important to beware of thermal shock, heating up or cooling down too quickly could cause the filler to deform.
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Calcium- and Calcineurin-Independent Roles for Calmodulin in Cryptococcus neoformans Morphogenesis and High-Temperature Growth

Calcium- and Calcineurin-Independent Roles for Calmodulin in Cryptococcus neoformans Morphogenesis and High-Temperature Growth

All of the temperature-sensitive isolates were crossed with strain JEC171 (MATa ade2 lys2) to determine if the 37°C growth defect was linked to the NAT insertion. Crosses were analyzed by both using random spore analysis and isolating individual basidiospores by micromanipulation and determin- ing the phenotypes of meiotic progeny produced by germina- tion. For 1 of the 12 isolates, 3E7, all meiotic segregants that displayed a growth defect at 37°C were also nourseothricin resistant, and nourseothricin-sensitive segregants grew nor- mally at 37°C, indicating that the NAT dominant marker and the growth defect are genetically linked. In addition to the growth defect at 37°C, isolate 3E7 displayed hypersensitivity to the calcineurin inhibitor FK506 at the permissive growth tem- perature of 25°C (Fig. 1A). This phenotype was the result of calcineurin inhibition by the FK506-FKBP12 drug-protein complex, as an frr1-3 cam1-ts mutant isolated following a ge- netic cross, in which FKBP12 contains an active-site point mutation, was resistant to FK506 (data not shown). Thus, cal- FIG. 1. An insertion in the calmodulin gene CAM1 confers temperature-sensitive growth. (A). Southern analysis of genomic DNA from insertion mutant 3E7 and parental strain JEC43. Genomic DNA was digested with EcoRV or HindIII. The probe used is indicated by the black bar. Abbreviations: WT, wild type; E, EcoRV; H, HindIII. (B). Schematic diagram of the CAM1 locus in the 3E7 mutant strain. The inserted NAT dominant marker lies 49 bp downstream of the CAM1 stop codon in the 3 ⬘ untranslated region. (C). Fivefold serial dilutions of cultures of the insertion mutant 3E7 and the parental strain JEC43 were inoculated on YPD medium and grown at 25°C or 37°C for 3 days or on YPD medium containing 1 ␮ g/ml FK506 and incubated at 25°C for 3 days.
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ION ASSOCIATION  III  THE EFFECT OF SULFATE INFUSION ON CALCIUM EXCRETION

ION ASSOCIATION III THE EFFECT OF SULFATE INFUSION ON CALCIUM EXCRETION

Wolf and Ball 9 observed increased excretion of calcium, magnesium and potassium during sulfate diuresis but found similar changes during infusion of 5 per cent glucose solution.. The pr[r]

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GASEOUS METABOLISM IN PREMATURE INFANTS AT 32-34°C AMBIENT TEMPERATURE

GASEOUS METABOLISM IN PREMATURE INFANTS AT 32-34°C AMBIENT TEMPERATURE

and in weight from 1,040 to 2,iiO gm were studied. Oxygen consumption, carbon diox- ide production, respiratory rate, rectal tem-.. perature, ambient temperature, and body.[r]

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The polarographic estimation of calcium and the reduction of the cobaltinitrite ion

The polarographic estimation of calcium and the reduction of the cobaltinitrite ion

When the concentration of oxalic acid is very small, of order 10- 3 molar no wave is obtained, probably as the half-wave potential has become so negative as to merge with the waves of hy[r]

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Simultaneous reductive and oxidative decomposition of calcium sulfate in the same fluidized bed

Simultaneous reductive and oxidative decomposition of calcium sulfate in the same fluidized bed

oxidizing zone in the upper portion of the bed above the reducing zone capable of converting CaS to CaO. The concurrent use of such reducing and oxidizing zones permits reducing conditions to be maintained which favor a high rate of decomposition even though these conditions favor the formation of CaS as well as CaO. The undesirable CaS, which would otherwise be discharged with the CaO product is eliminated by circulation of the fluidized particles through the oxidizing zone. Further, the heat of the exothermic reactions is conserved and utilized for promoting the endothermic reactions, both types of reactions occuring simultaneously while the rapid fluidized circulation of solids maintains a relatively uniform temperature throughout the bed.
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