Showing papers on "Calcium oxide published in 2008"

Active phase of calcium oxide used as solid base catalyst for transesterification of soybean oil with refluxing methanol

Abstract: For developing a process of biodiesel production with environmental benignity, much interest has been focused on solid base catalysts such as calcium oxide for transesterification of vegetable oils with methanol. In this paper, the active phase of calcium oxide was investigated by characterizing the catalyst collected after achieving the conversion of edible soybean oil into its methyl ester at reflux of methanol in a glass batch reactor. Calcium oxide combined with the by-produced glycerol, so that calcium diglyceroxide was a major constituent of the collected catalyst. The absence of calcium methoxide was clear from the spectrum of solid-state 13C-NMR. The chemical change of calcium oxide was not observed, when the yield of FAME reached 30%. The collected catalyst was not as active as the fresh one (calcium oxide), but was reused without any deactivation. In order to identify the active phase of the collected catalyst, we prepared calcium diglyceroxide by immersion of calcium oxide with refluxing methanol in the presence of glycerol. Calcium diglyceroxide prepared as the reference sample was as active as the collected catalyst in the transesterification, and was tolerant to air-exposure.

The Influence of Gypsum on the Hydration and Properties of Portland Cement Pastes

Abstract: The effect of sulfate on the rate of hydration was measured with a conduction calorimeter on neat cement pastes. Mortar prisms were used for physical tests. These studies have shown that a proper regulation of the reaction of early hardening is of much greater importance than merely regulating the time of setting. Such regulation not only influences the rate of hydration, but affects the strength and volume-change characteristics of the hardened cement paste. With some cement compositions the gypsum retards the initial hydration and set, while with others it acts as an accelerator. For each cement there is an optimum gypsum content, and calcium oxide, aluminum oxide content all influence this gypsum requirement. At their optimum gypsum contents the cements all showed essentially equal drying shrinkages.

Relationship between Structural Properties and CO2 Capture Performance of CaO-Based Sorbents Obtained from Different Organometallic Precursors

Abstract: A series of CaO-based sorbents were synthesized from various organometallic precursors, namely, calcium propionate, calcium acetate, calcium acetylacetonate, calcium oxalate, and calcium 2-ethylhexanoate, by a simple calcination technique. In general, the five organometallic precursors (OMPs) exhibit a three-step weight loss regime in their respective thermogravimetic (TG) profiles. The first weight loss occurs because of dehydration in the temperature range of 50−200 °C. The second one results from decomposition leading to the formation of calcium carbonate in the temperature range of 450−550 °C. The calcium carbonate so formed then undergoes decarboxylation at higher temperatures of 710−750 °C and results in the formation of calcium oxide. Among the various precursors evaluated, CaO-sorbents obtained from calcium propionate and calcium acetate precursors were found to exhibit the highest CO2 capture capacity. The observed results were correlated with the intrinsic properties of the precursors by means o...

Soil Property Criteria for Rammed Earth Stabilization

Abstract: This study relates value ranges of natural soil properties (plasticity, texture, and shrinkage) to the degree of predisposition of soils to stabilization for rammed earth wall construction. A total of 219 strength determinations were made on 104 soils compacted and stabilized with cement and/or lime and/or asphalt. Using a 2 MPa compressive strength criterion as the measure of stabilization success, soil property value ranges were related to the proportion of samples exceeding the criterion. Linear shrinkage (LS) and plasticity index (PI) are found to be the best discriminators of soil predisposition, with textural variables being useful secondary discriminators. “Favorable” soils, with stabilization success rates of ≥80% , include those with: (1) LS<6.0% and PI<15% ; and (2) LS 6.0–11.0%, PI 15–30%, and sand content <64% . These soils were stabilized with treatments averaging 4.2% cement and 1.8% lime, with individual treatments ranging from 4–8% total cement and/or lime. “Unfavorable” soils, with stabil...

Engineering Behavior of a Remolded Expansive Clay Blended with Lime, Calcium Chloride, and Rice-Husk Ash

Abstract: This paper presents experimental results obtained from tests conducted on remolded expansive soil specimens blended with rice-husk ash (RHA) and stabilized with lime and calcium chloride. The amounts of RHA, lime, and calcium chloride were varied from 0 to 16%, 0 to 5%, and 0 to 2%, respectively, by dry weight of the soil. The effect of additives on unconfined compressive strength (UCS) and California bearing ratio (CBR) is reported. It was found that the stress-strain behavior of expansive clay improved upon the addition of up to 5% lime or up to 1% calcium chloride. A maximum improvement in failure stress of 225 and 328% was observed at 4% lime and 1% calcium chloride, respectively. A RHA content of 12% was found to be the optimum with regard to both UCS and CBR in the presence of either lime or calcium chloride. An optimum content of 4% in the case of lime and 1% in the case of calcium chloride was observed even in clay-RHA mixes.

Behaviour of lime - Slag-treated clay

Abstract: This paper describes the strength and microstructural behaviour of lime–slag-treated clay. The microstructure was investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the strength of the treated clay was measured using the unconfined compressive strength (UCS) test. Untreated clay was prepared in the laboratory by mixing commercially available kaolin and bentonite, while hydrated lime and ground granulated blastfurnace slag (ggbs) were used as binders. XRD analyses of lime–slag-treated clay showed the existence of numerous reaction products such as calcium silicate hydrate (C–S–H), calcium aluminium silicate hydrate (C–A–S–H), and hydrotalcite (HT), which facilitated the strength increment. For a fixed proportion of lime, the relative intensity of pozzolanic reaction products was found to increase with increasing slag content. Slag was found to be very active to promote the pozzolonic reaction with lime, as evidenced from the presence of crystalline reticular (C–S–H) and ...

Influência da utilização de aditivos químicos no perfil da fermentação, no valor nutritivo e nas perdas de silagens de cana-de-açúcar

Abstract: The objective of this trial was to evaluate the effects of chemical additives in the dry matter losses, fermentation profile, and nutritive value of sugar cane silages. The trial was carried out in a completely randomized experimental design with four replicates per treatment. The following additives were applied to the fresh forage during the ensiling: control (without additive), L. buchneri, calcium oxide and calcium carbonate,1.0 and 1.5% (wet basis) each, and calcium sulfate 1.0% (wet basis), all of them diluted in to 40 L of water per ton of fresh forage. The variables analyzed were: total and gaseous dry matter losses, dry matter recovery, fermentation end products, and nutritive value. The use of calcium oxide or calcium carbonate were effective in reducing dry matter losses and gaseous production and had the highest dry matter recovery rate. Both silages had also low ethanol content and, as a result, had greater concentrations of residual water soluble carbohydrates and lactic acid. The addition of calcium oxide and calcium carbonate at the time of ensiling produced silages with higher nutritive value compared with all other treatments, due to the increase of ash content and dry matter and organic digestibility and also, by reducing the fiber content. The crude protein content range was similar to the values observed in the fresh forage. The treatments with L. buchneri and calcium sulfate were ineffective in altering the fermentation process of sugar cane silages and became similar to the control silages. In summary, the overall analysis pointed out that the treatment containing calcium oxide and calcium carbonate improved the fermentation and storage process.

Method and means for capture and long-term sequestration of carbon dioxide

Abstract: The invention teaches a practical method of recovering CO 2 from a mixture of gases, and sequestering the captured CO 2 from the atmosphere for geologic time as calcium carbonate and provides a CO 2 scrubber for carbon capture and sequestration. CO 2 from the production of calcium oxide is geologically sequestered. A calcium hydroxide solution is produced from the environmentally responsibly-produced calcium oxide. The CO 2 scrubber incorporates an aqueous froth to maximize liquid-to-gas surface area and time-of-contact between gaseous CO 2 and the calcium hydroxide solution. The CO 2 scrubber decreases the temperature of the liquid and the mixed gases, increases ambient pressure on the bubbles and vapor pressure inside the bubbles, diffuses the gas through intercellular walls from relative smaller bubbles with relative high vapor pressure into relative larger bubbles with relative low vapor pressure, and decreases the mean-free-paths of the CO 2 molecules inside the bubbles, in order to increase solubility of CO 2 and the rate of dissolution of gaseous CO 2 from a mixture of gases into the calcium hydroxide solution. The CO 2 scrubber recovers gaseous CO 2 directly from the atmosphere, from post-combustion flue gas, or from industrial processes that release CO 2 as a result of process. CO 2 reacts with calcium ions and hydroxide ions in solution forming insoluble calcium carbonate precipitates. The calcium carbonate precipitates are separated from solution, and sold to recover at least a portion of the cost of CCS.

Spectroscopic, structural and textural properties of CaO and CaO–SiO2 materials synthesized by sol–gel with different acid catalysts

Abstract: Calcium oxide and a mixed CaO(10)–SiO2(90) wt% sample were synthesized by sol–gel method, using HCl or HNO3 as hydrolysis catalysts. The powders were thermally treated at 200, 400, 600 and 800 °C. Sample characterization was carried out by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The specific surface area and pore volume were measured by the BET method. For the pure samples, it was found that the crystalline phases and structural properties depend on the catalyst used during the synthesis; whereas the surface areas were similar in both cases. On the other hand, at high temperatures, the mixed CaO–SiO2 oxide showed glass-like properties, where CaO is dispersed in an amorphous phase.

Physicochemical Behavior of Cement Kiln Dust-Treated Kaolinite Clay

Abstract: The physicochemical responses induced in kaolinite clay treated with 25% of a high free lime content cement kiln dust (CKD) were investigated. Atterberg limits, unconfined compressive strength, and stiffness of the compacted, CKD-treated kaolinite were measured as functions of the curing period. These properties were compared with those of the untreated clay and of the clay treated with quicklime, so as to determine the comparative extent of enhancement induced by the CKD treatment. The CKD-treated clay developed significantly higher strength than quicklime-treated clay containing the same amount of lime. The remarkable enhancement in clay properties observed suggests significant potential for use of some CKDs as soil stabilizers. The mineralogical and morphologic changes induced in the clay by the CKD addition were characterized using X-ray diffraction (XRD), scanning electron microscopy, and energy-dispersive X-ray analyses, so as to help provide an understanding of the CKD-clay interaction mechanism. T...

High performance expansible cement clinker expansion agent series prepared thereby

Abstract: Disclosed are a high-performance expansion cement clinker, a manufacturing method of the cement clinker, a series concrete expansion agent and a manufacturing method of the concrete expansion agent. The high-performance expansion cement clinker is made as follows: firstly, 50-90 wt% of limestone, 1-20 wt% of bauxite, 5-30 wt% of gypsum and 1-5 wt% of iron powder are grinded together into raw meal, then the raw meal is calcined at 1250-1400 DEG C in a rotary kiln, a tunnel kiln or a roller kiln to get the cement clinker. The cement clinker is milled alone or in combination with sulfur calcium aluminate cement clinker, calcium aluminate cement clinker, anhydrite, calcined gangue, alunite, calcined kaolin and hydration heat inhibiting additives until the specific surface area reaches 200-400m2/kg, so as to get the series concrete expansion agent. The high-performance expansion cement clinker disclosed in the invention is calcium hydroxide-hydrated calcium aluminate sulfate double-expansion source expansion clinker, which is fast in expansion rate and high in expansion efficiency and uses less bauxite of scarce resources; besides, the calcination temperature is low to avoid calcium oxide dead burning, so the preparation is safe and reliable.

Amorphous polyamide resin composition and molded product

Abstract: Provided are an amorphous polyamide resin composition having high transparency, and is excellent in heat resistance and stiffness, and a molded product thereof. The glass filler contains, expressed in terms of oxides by mass %, 68 to 74% of silicon dioxide (SiO 2 ), 2 to 5% of aluminum oxide (Al 2 O 3 ), 2 to 5% of boron oxide (B 2 O 3 ), 2 to 10% of calcium oxide (CaO), 0 to 5% of zinc oxide (ZnO), 0 to 5% of strontium oxide (SrO), 0 to 1% of barium oxide (BaO), 1 to 5% of magnesium oxide (MgO), 0 to 5% of lithium oxide (Li 2 O), 5 to 12% of sodium oxide (Na 2 O), and 0 to 10% of potassium oxide (K 2 O), where a total amount of lithium oxide (Li 2 O), sodium oxide (Na 2 O), and potassium oxide (K 2 O) is 8 to 12%.

Calcium carbide production method

Abstract: The invention relates to a carbide preparation method belonging to the field of carbide preparation. The conventional carbide preparation technology adopts block materials and electric arc as a heat-supply, while the preparation method according to the invention adopts powdery carbon-containing materials and powdery calcium-containing materials, and the combustion of partial carbon-containing materials and oxygen-containing gas as a heat-supply at 1700-2300 DEG C to prepare carbide, wherein the carbon-containing materials is coal or coke, calcium-containing materials is calcium carbonate, calcium oxide, calcium hydroxide or carbide slag, the granularity of the carbon-containing materials and calcium-containing materials is less than 1mm, and the quality ratio is 0.5-3:1. The oxygen-containing gas for combustion is oxygen, oxygen-enriched air or air. The method solves the problems of high energy consumption and high pollution of the carbide preparation and has advantages of wide choice scope of materials, high energy utilization rate, continuous operation and large production capacity. The technology also couples with the process of carbon-containing materials coking and calcium-containing materials calcining, preheats the materials to 500-1500 DEG C utilizing the combustion of by-products CO of the carbide preparation and the assistant fuel, thereby further reducing the oxygen and energy consumption of the carbide preparation.

Environment-friendly type soil solidifying agent

Abstract: This is a compound material of contents as: one or two from fly ash, aluminum sulfate, calcium sulfate, sodium sulfate, sodium carbonate, potassium carbonate, aluminum oxide; one or two from granulated blast furnace slag, calcium carbonate, potassium hydroxide, calcium oxide, sodium silicate, silica oxide; one or two from aluminum potassium sulfate, Portland cement, carbide slag, lime, alunite, gesso; one or two surface active agent from triethanolamine, calcium lignosulphonate and sodium lignosluphonate.

Phase equilibria in ferrous calcium silicate slags: Part IV. Liquidus temperatures and solubility of copper in "Cu2O"-FeO-Fe2O3-CaO-SiO2 slags at 1250 °C and 1300 °C at an oxygen partial pressure of 10(−6) atm

Abstract: Liquidus temperatures and the solubility of copper oxide in slag are evaluated and discussed for the ferrous calcium silicate system (described by the “Cu2O”-FeO-Fe2O3-CaO-SiO2 system). The solubility of copper in this system was interpolated into the fully liquid region by fitting the experimental values to a second-power polynomial in terms of CaO/SiO2 and SiO2/Fe compositional parameters. The industrial application of this slag system for copper converting is discussed and optimal slag compositions are defined that ensure one stable liquid phase over the range of temperatures at the oxygen partial pressure of 10−6 atm. The copper oxide solubilities in iron-silicate, ferrous calcium silicate, and calcium ferrite slags are compared at fixed conditions relevant to copper converting.

Sullage solidifying method

Abstract: A sludge solidification method is a method for carrying out solidification treatment to the sludge produced in water conservancy projects and civil engineering. The method is that: a. the liquid water content, the clay content and organic content of dredging sludge are tested. b. curing agent is prepared: the curing agent mainly contains cement and calcium oxide which play the function of solidification; wherein, the weight proportion is between 1 : 1 to 4 : 1; waste gypsum is used as water reducing agent which occupies 1 to 8 percent of the sum of cement and calcium oxide in proportion; mealy sand or pulverized fuel ash are used as concrete aggregate which occupies 3 to 5 percent of the sum of the cement and calcium oxide in proportion; c. the curing agent-mixing ratio which is usually controlled from 5 to 20 percent is determined; sampling respectively is carried out, setting time is tested and the unconfined compressive strength which maintains 7, 14 and 28 days is tested by sampling, and the curing agent-mixing ratio finally is determined according to optimal performance price ratio; d. the sludge is carried out curing and constructing in site; mechanical devices are used for stirring the curing agent and the sludge rapidly and evenly, thereby leading the solidification to be rapid and full.

Self-heating apparatuses using solid chemical reactants

Abstract: The present invention provides self-heating apparatuses and methods of heating using an aqueous solution and a solid chemical reactant mixture. The solid chemical reactant mixture may include magnesium chloride, calcium chloride, and/or calcium oxide.

Process for production of PCC

Abstract: The present invention relates to a process of preparing precipitated calcium carbonate (PCC) in a low energy intensity reactor in such a manner that the amount of solids in the PCC product can be raised to 35% or more without performing a dewatering step. The process comprises performing in parallel and in two or more separate reaction vessel the steps of contacting calcium hydroxide with a gas comprising carbon dioxide to allow formation of calcium carbonate, and adding calcium oxide, lime or dry calcium hydroxide or a combination of any of the three to a part of the resulting mixture of calcium hydroxide and calcium carbonate. The invention further provides a specialized reactor system as well as the use of this reactor system in the manufacture of PCC.

Environment-friendly type soil curing agent

Abstract: An environment-friendly type soil-solidified agent belongs to the technical field of municipal and building engineering, which aims to resolving problems of present soil-solidified agents which have low soil-solidified strength, bad soil-solidified stability, form saline land and have impaction on ecologic environment. The environment-friendly type soil-solidified agent is prepared by a compound technical formula which comprises two or three chemical materials among cement, slag and calcium carbonate, at least two chemical materials among calcium hydroxide, calcium oxide, calcium sulfate, aluminum sulfate and sodium sulfate and at least two chemical materials among potassium carbonate, sodium carbonate, calcium lignosulphonate, sodium lignosulphonate, sodium tripolyphosphate, calcium stearate, sodium stearate, sodium hydroxide, silica, sodium aluminates, calcium chloride, magnesium chloride and urea. The environment-friendly type soil-solidified agent has the advantages of small dosage and good effect of environment protection, as the principal raw materials are all nontoxic, innocuous and pollution-free, the environment-friendly type soil-solidified agent is reliable and safe to animals and plants. Further as obtaining raw materials locally, the environment-friendly type soil-solidified agent is low in construction cost, not only adapted for stabilizing road foundation and processing municipal road structure layer and soft soil foundation, but also adapted for mechanized construction working.

Method for preparing ultra-fine active nano-calcium carbonate with low-ore grade limestone wet-process activation

Abstract: The invention provides a method for preparing superfine activated nano calcium carbonate by utilization of low-grade lime. The method adopts the technical proposal that: firstly, the low-grade lime is calcined and crushed so as to prepare calcium oxide; secondly, staged sieving is performed, namely a part of high-quality calcium oxide enters into the next procedure for producing calcium hydroxide and calcium carbonate; and thirdly, the superfine activated nano calcium carbonate product is prepared after incineration through an incinerator, heat-insulated aging, bubbling carbonization, secondary aging, wet-way secondary activation, recarbonization, centrifugal dewatering, drying and superfine crushing of the high-quality calcium oxide. When the product is applied to plastics and rubber, the cost can be reduced and simultaneously the hardness, the toughness, the strength, the bending resistance and the abrasion resistance of polymer products can be improved; and when the product is applied to coating, performance parameters such as the insubmersibility, the storage stability, the thixotropy and so on can be effectively improved.

Forensic Investigation of Pavement Premature Failure due to Soil Sulfate-Induced Heave

Abstract: Current practice does not recommend stabilizing high sulfate-bearing soils using calcium-based stabilizers due to high potential swell and low retained unconfined compressive strength. In this technical note, a series of tests has demonstrated that a combination of lime and fly ash (Class F) proved to be the most suitable stabilizer for a high sulfate-bearing soil, and a combination of lime and slag seemed to be the most effective stabilizer for a moderate sulfate-bearing soil in terms of retained unconfined compressive strength and three-dimensional free swell potential.

Efficacy of lime-stabilised fly ash in expansive soils

Abstract: The alternate swelling and shrinkage undergone by expansive clays due to moisture fluctuations causes substantial distress to structures built on such soils. Techniques such as sand cushions and ohesive nonswelling soil (CNS) cushions have been tried to arrest volume changes in these soils and hence prevent damage to structures. Sand cushions have been proved to be counterproductive. A CNS layer, though effective initially, became less effective after the first cycle of wetting and drying. Research carried out by the authors using a lime-stabilised fly ash cushion has shown that it is quite effective in arresting volume changes in expansive soils. A fly ash cushion, stabilise with 10% lime and with thickness equal to half that of the active zone in an expansive soil bed, educes heave by about 68% initially. With subsequent cycles of swelling and shrinkage the percent ge reduction in swelling is as much as 99·2%. Studies carried out on leaching have shown that only a small percentage of lime added to the f...

Additive for preparing fine oxide dispersion steel, preparation and use thereof

Abstract: The invention relates to an external furnace refining technology for steelmaking, in particular to an additive for preparing fine oxide dispersion steel, a method for making the same and an application of the additive. The invention belongs to the metallurgical technology field. The additive consists of raw materials proportioned according to a formula; low-melting point pre-smelting slag powder, calcium fluoride, calcium carbonate, magnesium carbonate or a mixture of calcium carbonate and magnesium carbonate, calcium oxide, magnesia or a mixture of calcium oxide and magnesia and caking agent are respectively adopted and prepared to additives with various additive types of core-spun yarn, powder, a composite pellet and a composite sphere; through adopting wire feeding, powder spraying and pill shooting, or even a direct throwing mode, the additive is fed in LF, RH, VD or CAS-OB in order that the oxide class impurity is fine, dispersed and distributed in steel; and the addition type is beneficial for application and can stably and rapidly produce the fine oxide dispersion steel with an oxide grain diameter of less than 1mu m in large quantities, thereby greatly improving the quality of rolled steel and reducing the smelting cost.

Zirconium oxide foamed ceramic filter

Abstract: The invention relates a ceramic filter used in the foundry industry, in particular to a zirconium oxide ceramic foam filter with high resistance to heat shock and elevated temperature strength. The raw material of the zirconium oxide ceramic foam filter of the invention has the following ingredients by weight portions: 80-97 percent of oblique crystal zirconium, 2-10 percent of stabilizer and 1-10 percent of binder; the stabilizers are two or more of calcium oxide, aluminium oxide, silicon oxide, magnesium oxide, yttrium oxide, cerium oxide and other rare earth oxides; the binder is inorganic or/and organic ones. The zirconium oxide ceramic foam filter of the invention can be used in the filtering of high-temperature alloys, and has advantages of low cost and superior quality compared with the filters made from pre-made stabilized zirconium.