Showing papers on "Lime published in 1998"

Lime pretreatment of crop residues bagasse and wheat straw

Abstract: Lime (calcium hydroxide) was used as a pretreatment agent to enhance the enzymatic digestibility of two common crop residues: bagasse and wheat straw. A systematic study of pretreatment conditions suggested that for short pretreatment times (1–3 h), high temperatures (85-135°C) were required to achieve high sugar yields, whereas for long pretreatment times (e.g., 24 h), low temperatures (50–65°C) were effective. The recommended lime loading is 0.1 g Ca(OH)2/g dry biomass. Water loading had little effect on the digestibility. Under the recommended conditions, the 3-d reducing sugar yield of the pretreated bagasse increased from 153 to 659 mg Eq glucose/g dry biomass, and that of the pretreated wheat straw increased from 65 to 650 mg Eq glucose/g dry biomass. A material balance study on bagasse showed that the biomass yield after lime pretreatment is 93.6%. No glucan or xylan was removed from bagasse by the pretreatment, whereas 14% of lignin became solubilized. A lime recovery study showed that 86% of added calcium was removed from the pretreated bagasse by ten washings and could be recovered by carbonating the wash water with CO2 at pH 9.5.

Lime and Limestone: Chemistry and Technology, Production and Uses

Abstract: PRODUCTION OF LIMESTONE. Formation, Classification and Occurrence of Limestone. Physical and Chemical Properties of Limestone. Prospecting and Quarrying. Processing and Dispatch of Limestone. Sampling and Testing of Limestone. USES AND SPECIFICATIONS OF LIMESTONE. Overview and Economic Aspects of the Limestone Market. Construction and Building. Use of Limestone in Cement Production. The Use of Limestone in Agriculture. Use of Limestone in Refining Metals. Others Uses of Limestone. PRODUCTION OF QUICKLIME. Physical and Chemical Properties OF Quicklime. Raw Materials for Lime Burning (Limestone, Fuel and Refractories). Calcination of Limestone. Production of Quicklime. Processing Storage and Transport of Quicklime. Sampling and Testing of Quicklime. PRODUCTION OF SLAKED LIME. Physical and Chemical Properties of Slaked Lime. Production of Hydrated Lime. Handling and Storage of Hydrated Lime. Production of Milk of Lime and Lime Putty. Handling and Storage of Milk of Lime and Lime Putty. Sampling and Testing of Slaked Lime. USES AND SPECIFICATIONS OF LIME PRODUCTS. Overview and Economic Aspects of the Lime Market. Construction and Building. The Use of Lime in Iron and Steelmaking. Water and Sewage Treatment. Gaseous Effluents. Agriculture, Food and Food By-products. Use of Quick and Slaked Lime in the Production of Chemicals. Other Uses of Quick and Slaked Lime. SAFETY, HEALTH AND ENVIRONMENT. Control of the Environmental Effects of Lime and Limestone Production. Toxicology and Occupational Health. Annexes. Index.

Nutrient limitations and their implications on the effects of atmospheric deposition in coastal dunes; lime-poor and lime-rich sites in the Netherlands

Abstract: 1 A survey of plant and soil parameters was carried out in dry dune grasslands along the Dutch coast in the lime- and iron-poor Wadden district and initially lime- and iron-rich Renodunaal district, in order to detect differences in nutrient availability related to soil characteristics and potential sensitivity to atmospheric deposition of nitrogen. 2 Plant biomass and phosphorus pools in the shoot were higher in the Wadden district. The low foliar nitrogen concentrations and nitrogen/phosphorus ratios in the Wadden district suggested nitrogen-limitation, while in the Renodunaal district there appeared to be a balanced supply of both nitrogen and phosphorus. 3 Soil pH, soil organic matter, soil nitrogen and phosphorus concentrations and total amounts were generally higher in the Renodunaal district. In both districts mineral phosphorus decreased with acidification and phosphorus oxalate (iron and aluminium bound) increased. 4 In the Wadden district iron is present primarily in iron–organic matter complexes, which leads to reversible binding of phosphorus. In the Renodunaal district large amounts of iron (hydr)oxides occur and at high pH may contribute to reversible phosphorus-sorption, but at low pH this probably leads to immobilization of phosphorus. 5 While pools of soil phosphorus are low in the Wadden district, the phosphorus availability may be relatively high due to the comparatively loose nature of phosphorus-sorption. As a result the area may be nitrogen-limited and grass-encroachment may thus have resulted from atmospheric deposition of nitrogen. 6 In the Renodunaal district, atmospheric deposition probably only accelerates grass-encroachment, because deposition of acid and nitrogen increases the availability of both nitrogen and phosphorus and maintains the ‘co-limitation’.

Immobilization Mechanism of Arsenic in Waste Solidified Using Cement and Lime

Abstract: The material studied, a waste fly ash from the metallurgical industry, contains the toxic element As in high concentrations, ranging from 23% to 47% (wt %). Besides As, Sb and Pb are present in the waste material. The waste was solidified with inorganic materials such as cement and pozzolanic materials in order to reduce the leachability of the contaminants from the waste. The optimal solidification recipe lowered the As concentration in the leachate of the extraction test DIN 38 414 S4 from ca. 5 g/L to ca. 5 mg/L. In this paper, it was shown that this enormous reduction in As concentration was due to the formation of CaHAsO3 in the leachate, in the presence of Ca(OH)2. Formation of CaHAsO3 alone cannot lower the arsenic concentration beneath ca. 55 mg/L, as was calculated with the speciation program MINTEQA2.

Influence of Compactive Efforts and Compaction Delays on Lime-Treated Soil

Abstract: The results of a laboratory study on the influence of standard Proctor and West African standard compactive efforts as well as compaction delays up to 3 h on the compaction and strength characteristics of lateritic soil treated with a maximum of 8% lime (by dry weight of soil) is presented. The results obtained show that the compaction and strength properties of the lime-treated soil decreased with increases in compaction delays. The decreases that were generally greater at higher lime contents were more prominent in specimens compacted at the energy of the West African standard. The determination of properties of lime-treated soil at no compaction delay defines optimum properties of the soil-lime mixtures, while compaction and strength properties determined following compaction delays define the minimum that can be achieved in the field for the specified elapsed times between mixing and compaction.

Hydraulic Conductivity and Leachate Characteristics of Stabilized Fly Ash

Abstract: Disposal of fly ash on land amounts to sacrificing precious land space. Recycling of fly ash is one of the methods of solving the disposal problem. Stabilization of a low lime fly ash with lime and gypsum was studied through large scale tests on the stabilized material designed to simulate field recycling conditions as closely as possible, and found to be a very effective means to control hydraulic conductivity and leachate characteristics. The effects of moulding water content, lime content, gypsum content, curing period, and flow period on hydraulic conductivity, and on leachate of metals flowing out of the stabilized fly ash are reported herein. With proper proportioning of the mix, and adequate curing, the values of hydraulic conductivity on the order of 10\u–\u7 cm/s were achieved. The concentrations of As, Cd, Cr, Cu, Fe, Hg, Mg, Ni, Pb, and Zn in the effluent emanating from the hydraulic conductivity specimens of mixes with higher proportions of lime or lime and gypsum were below threshold limits acceptable for contaminants flowing into ground water.

Molar-tooth structure in Proterozoic carbonate rocks: Origin from synsedimentary earthquakes, and implications for the nature and evolution of basins and marine sediment

Abstract: Proterozoic argillaceous lime mudstones commonly contain molar-tooth structure, a curious synsedimentary feature consisting of crumpled, generally vertically oriented veins filled with calcite microspar. Long enigmatic, these veins are interpreted here as earthquake-induced deformation structures. A model is proposed whereby violent ground motion caused shrinkage, dewatering, and fissuring of the colloidal sea-floor sediment of clay and lime mud. A slurry of equant particles of lime mud, segregated from the clay platelets trapped in the matrix, was expelled into these voids. The host bed underwent as much as 80% compaction as well as shear, causing the lime mud-filled fissures to be ptygmatically folded and shingled both vertically and horizontally, and in places pulled apart. This lime mud lithified rapidly by high-Mg calcite grain growth, such that subsequent earthquakes shattered the folded veins. In the Belt basin of western North America, tsunamis from different events created currents that transported ooids and coarse sand from shoals into deeper water, and scoured deeply into the now-consolidated sediment, leaving behind a lag of vein fragments. Molar-tooth structure is a signature of basin tectonism recorded specifically in argillaceous lime mudstones deposited in low-energy settings above the thermocline in supersaturated marine water. Syneresis cracks are the counterpart in terrigenous facies, in that silt and sand were injected into the shrinkage fissures. This process points to the importance of seismically induced compaction under negligible burial. Smectite might have made up a significant proportion of the sediment, making it more conducive to shrinkage. The absence of molar-tooth structure in Phanerozoic strata is ascribed mainly to changes in sediment rheology brought about by increased organic binding due to diversification of the microbiota.

Permeability of lime-treated lateritic soil

Abstract: Laboratory investigations were carried out on a residual lateritic soil treated with quicklime (up to 8% by weight of dry soil) in order to evaluate the effect of lime content, curing period, and compactive effort on the permeability of lateritic soil-lime mixtures prepared at various maximum dry densities and corresponding optimum moisture contents. The permeability of uncured specimens (standard Proctor) increased to a maximum at 4% lime content and decreased with increasing lime content. Specimens compacted at the energy of the West African Standard had coefficients of permeability that decreased with increasing lime content. For the cured condition, the permeability of all the lime-treated specimens compacted at the two energy levels increased with curing age up to 14 days and decreased with curing age beyond 14 days.

Soil and plant analyses for lime and fertilizer recommendations in Brazil

Abstract: The fertilizer recommendation guidelines for over 160 crops for the State of Sao Paulo, Brazil were updated in 1996 based on recent results of research on soil and plant analysis, and crop responses. Recommendations are based mainly on soil analysis and expected yield. Limestone rates are calculated to raise soil base saturation as a percentage of the cation exchange capacity (CEC) of the soil at pH 7.0, to levels which vary with crop species (i.e., to 50% for rice, coffee, and cassava, 60% for sugar cane and soybeans, 70% for cotton and maize, and 80% for grapes and onions). In addition, exchangeable magnesium (Mg) contents must reach a minimum level. Exchangeable subsoil aluminum (Al) and calcium (Ca), and clay content are used to determine rates of gypsum as amendment of subsoil acidity. Fairly consistent data on soil phosphorus (P) and potassium (K) calibration are available for Brazilian soils. Potassium rates are recommended based on values of soil exchangeable K and, for P fertilization, i...

Effect of bentonite and zeolite on durability of cement suspension under sulfate attack

Abstract: The sulfate resistance of cement-bentonite suspension with additive lime is compared with that of a suspension where bentonite was totally replaced by pozzolanic zeolite. Cement-bentonite suspensions are frequently used for the construction of underground sealing walls. The disadvantage of these suspensions is due to a relatively low resistance against the aggressive media. With the purpose of obtaining sulfate-resistant suspension, a cement-zeolite suspension with the viscosity (Marsh cone) of 35 sec, the maximum settlement of 3% volume/24 hr, and minimal compressive strength (28 days curing in water) of 2.0 MPa (290 psi) was prepared. In the 10% sodium sulfate solution, a total destruction of the cement-bentonite suspension test specimens took place within 30 days. No degradation was found in the cement-zeolite suspension attacked by the sulfate solution for 365 days. Moreover, the cement-zeolite suspension showed an increase in compressive strength. It is supposed that the reason for this lies in the high reactivity of zeolite toward lime and intensive consumption of calcium hydroxide by pozzolanic reaction of zeolite. The SO3 bonding and resulting calcium sulfate dihydrate development is markedly decreased in the cement-zeolite suspension compared with cement-bentonite suspension.

The Structure, Stoichiometry and Properties of C-S-H Prepared by C3S Hydration Under Controlled Condition

Abstract: Hydrations of tricalcium silicate undertaken by keeping constant lime concentration in solution in an open system and in diluted suspensions for different values of [CaO] ranging between 65 and 30 mmol/1 show that the lime concentration in solution is the parameter which determines the main characteristics of the reaction and products The stoichiometry of C3S hydration products vanes with lime concentration in the same way as synthetic C-S-H until C/S ca 15 corresponding to about [CaO] =20 mmol/1 Beyond this concentration, single phase C-S-H samples were obtained with 18

Effect of lime (CaCO3) application on soil structural stability of a red earth

Abstract: Changes in soil structural stability as a result of lime application (1·5 t/ha) were monitored over 3 years in a red earth with contrasting initial pH, organic carbon, and structural stability conditions at Wagga Wagga, NSW. The lime was applied to the surface of the direct drilled-soil without any incorporation, but in the case of the cultivated soils, the lime was incorporated into the top 10 cm by scarifying. After liming, an initial temporary reduction in macroaggregate (>2 µm) stability was detected in the immediate surface (0-2·5 cm) of the direct-drilled soil where the highest increases in pH, losses in soil organic carbon, and increases in microbial biomass were also observed. The decrease in structural stability was attributed to lime-induced increases in biological decomposition and the resulting soil organic carbon losses. Subsequent samplings did not detect any difference in either macro- or micro- (<50 µm) aggregate stability of this soil as a result of lime treatment. In contrast, for the 2 cultivated soils which had lower initial structural stability and organic carbon levels, a decline in stability was not observed. Instead, significant increases in macroaggregate and microaggregate stability were detected 1·5 years after lime application. By the end of 3 years, macroaggregate stability of the limed cultivated soils approached that of the direct-drilled soil. The improvement in structural stability extended to 7·5 cm depth 3 years after lime application. Wet-sieving experiments using prolonged periods of shaking indicated enhanced stability of the water-stable aggregates of the limed cultivated soils but not the direct-drilled soils.

Apparatus and methods for reducing carbon dioxide content of an air stream

Abstract: Apparatus and methods for reducing CO 2 content of an air stream are described. A method of reducing CO 2 content of an air stream in accordance with one embodiment of the present invention includes the steps of first injecting hydrated lime into an air stream containing CO 2 . The hydrated lime reacts with the CO 2 in the air stream to form calcium carbonate, CaCO 3 . The air stream is then directed into a lime storage container having a dust collector. As air is drawn through the dust collector, hydrated lime and CaCO 3 are collected on the filter bags. The air drawn through the dust collector has a reduced CO 2 content as compared to the air prior to being injected with hydrated lime. The reduced CO 2 content air stream exhausted from the dust collector can then be directed to the different parts of the hydrated lime manufacturing process, such as the milling process, conveying and storing the hydrated lime.

"A Study of the Hydration of Lime-Pozzolan Binders"

Abstract: DTA/TG and TG/DTG thermal studies and XRD investigations were carried out on pastes of lime-pozzolan binders to examine the relative hydration process. The binders were prepared with two natural pozzolans and hydrated lime, mixed together in different proportions. The main hydrated phases formed in the pastes are calcium silicate hydrate (CSH) and mono-carboaluminate. The growth of CSH was greater for the paste of the pozzolan richer in reactive constituents. For pastes with a higher lime/pozzolan ratio, a slowing of the formation of CSH was observed, while the formation of monocarboaluminate was more intense. The calcium hydroxide contents of the pastes obtained by thermogravimetric analysis made it possible to determine the pozzolanic activities of the two pozzolans under examination. The mortars for the various lime-pozzolan binders displayed characteristic hardening.

Steel slag: applications for amd control

Abstract: In both laboratory and field studies, steel slags were found to generate exceptionally high levels of alkalinity over extended periods. Steel slags also have high neutralization potentials and can be used as alkaline amendments to acid-producing materials. This paper discusses the alkalinity-generating capacity of steel slags, their metal leaching potential and applications for acid mine drainage control. Results indicate that steel slags can provide highly concentrated alkaline recharge to acid mine wastes. Proper design and sizing offers the potential for a low- to zero-maintenance method for treating acid mine drainage (AMD) within the spoil pile itself. Since slags form around the melting point of iron, >2,700 o F, most compounds which have a low boiling point have been driven off. Most of the residuals are encased as oxides or in a calcium-alumino-silicate glassy matrix. Fortunately, the matrix is soluble and releases calcium and manganese oxides which drive the pH above 10. Since slag is a glass in its coarser form (e.g. -1/8 in.) it will, unless compacted, maintain high permeability regardless of how much water has passed through it. Unlike lime, steel slags do not absorb CO 2 from the air and convert back to relatively insoluble calcite: Ca (OH) 2 + CO 2 fiCa CO 3 +H 2 O. This is an extremely important property, since it means slag will generate high levels of alkalinity even after years of open storage. STEEL SLAG: WHAT IS IT? Technically, slag is nearly any solid which melts and forms a silicate glass during a metal refining process. In the power industry, slag is ash which melts and sticks to the walls or pipes of the boiler. In the base-metal industry, slags result from the smelting of various ores of copper, zinc, lead, etc. These slags can have high concentrations of heavy metals. In this paper, we are only discussing slags from the steel-making process. In making steel, iron ore or scrap metal is melted in combination with limestone, dolomite or lime. Pure iron is soft, bends easily under loads, and has limited uses. Small amounts of carbon, nickel, manganese, and other elements turn iron into various alloys of steel. There are hundreds of grades of steel ranging from basic carbon steel to high grade stainless. Steel making begins by reducing any metal oxides in the melt to pure iron metal, while scavenging ions such as aluminum, silicon, and phosphorous. The later three elements are bad news for steel as they cause it to become weak, brittle, or otherwise difficult to roll into sheet in a predictable way. For that matter, they make it nearly impossible to make anything useful out of iron. (Even though iron is much more readily available, its impurities caused bronze to become the metal of choice for tools after stone became obsolete.) Fortunately, our ancestors discovered that ironis imperfections could be controlled by adding limestone or dolomite. These calcium compounds mix with aluminum, silicon and phosphorous to form slag. Slag then floats to the top of the melt, is poured off, and sent to disposal. Slag starts its life at about 2,700 o F and cools almost immediately.

Multidimensional capillary GC–GC for the analysis of real complex samples. Part II. Enantiomeric distribution of monoterpene hydrocarbons and monoterpene alcohols of cold-pressed and distilled lime oils

Abstract: The enantiomeric distribution of sabinene, β-pinene, limonene, linalool, terpinen-4-ol, and α-terpineol for cold-pressed Key lime oils type A and type B, cold-pressed Persian lime oils, and distilled lime oils has been determined by a fully automated, multidimensional, double-oven (GC–GC) system using a SE-52 precolumn and a β-cyclodextrin main column. This system allows fractions to be multransferred during the same GC analysis and the use of the two GCs independently when the multitransfer option is not used. The results allow us to distinguish cold-pressed Key lime oils type A and type B, cold-pressed Persian lime oils, and distilled lime oils. © 1998 John Wiley & Sons, Inc. J Micro Sep 10: 203–212, 1998

On the Possible Role of Opuntia ficus-indica Mucilage in Lime Mortar Performance in the Protection of Historical Buildings

Abstract: In Mexico, the preparation of lime mortar may include the addition of nopal juice. The lime mortarprepared in this way has been used for centuries for restoring and protecting historical buildingsbecause of an improved performance against water penetration and cracking. To date, no scientificexplanation has been offered to explain the use of cactus juice in lime mortar. The objective of thisstudy was to provide a preliminary experimental account of the use of nopal juice as animpermeabilization agent. Calcium hydroxide and commercial slaked-lime pastes were preparedand mixed with varying concentrations of nopal juice at ratios of 0.65%, 1% and 1.95% of cactusjuice to Ca(OH)2 or commercial slaked lime. The dry pastes thus obtained were evaluated by apenetration-breaking test with a TA-XT2 texture analyzer. Increasing amounts of cactus juice in theformulation resulted in a drastic reduction of the maximum stress and deformation values of thepastes as compared to those of the control sample. In the control sample, a more mechanicallyhomogeneous Ca(OH)2 structure was formed. In the sample with the lower cactus juice ratio, themucilage had a reduction effect upon the continuity of the network. The amorphous soft filler,forming a discontinuous phase, makes the hydroxide network weaker. As the ratio increased,mechanical properties also increased due to the formation of a homogeneous network of nopalmucilage interpenetrated into the hydroxide base. Results indicate the formation of aninterpenetrated network of nopal mucilage with no structural modification involved.

Residual effects of surface applications of organic matter and calcium salts on the subsoil of a red-brown earth

Abstract: Summary. The effects of surface soil applications of organic matter and calcium salts on the subsoil (200–280 mm) of a red-brown earth (Natrixeralf) were investigated in a field experiment. The calcium treatments included gypsum, lime or nil-calcium added to the surface soil. To these calcium treatments, organic matter or nil-organic matter was added. Three years after final applications of organic matter and calcium salts to the surface soil, the physical and chemical properties of the subsoil were measured. The bulk physical measurements of the subsoil (penetrometer resistance, bulk density, macroporosity and plastic limit) were not significantly influenced by the treatments. The electrical conductivity of the subsoil was greater in the gypsum-treated soil than in the lime- or nil-calcium-treated soils. Subsoil pH values were lower in the gypsum-treated soil than in the lime- or the nil-calcium-treated soil. Dispersion (spontaneous and mechanical) of the clay subsoil decreased with gypsum-treated surface soil. In treatments where both organic matter and gypsum were added to the surface soil, the subsoil showed an increased concentration of exchangeable calcium and decreased spontaneous dispersion of the clay.

Reaction Mechanism of Calcium Hydroxide with Gaseous Hydrogen Chloride

Abstract: The reduction of acid gas content in combustion or incineration flue gases can be carried out by reaction with dry, fine alkaline sorbents such as calcium oxide or calcium hydroxide In the present work, in addition to the thermodynamic study of the different reactions involved in the dechlorination process, an experimental study to identify the reaction products by means of X-ray diffraction, electron microscopy and thermogravimetry has been carried out It has been shown that the reaction of hydrochloric acid with hydrated lime leads to the formation of not only calcium chloride but calcium hydroxichloride

Investigation into the mechanisms causing lime responses in a grass/clover pasture on a clay loam soil

Abstract: A mowing trial was conducted on the Mangatea clay loam (a yellow‐grey earth or Umbric Dystrochrept fine hallositic mesic) to examine the mechanisms causing lime responses in a grass/ clover pasture. The trial site was located on a sheep and beef farm 8 km south of Te Kuiti, New Zealand. The site generally had cool winters and warm moist summers, with an annual rainfall of about 1400 mm. The treatments consisted of 3 lime rates (0, 5000, 10 000 kg ha−1) in the absence of P and 6 lime rates (0, 1250, 2500, 5000, 7500, 10 000 kg ha−1) in the presence of P (50 kg P ha−1 yr−1), all in the presence of sodium molybdate (Mo), and an additional treatment where P was applied in the absence of lime and Mo. Lime increased grass yield but decreased clover yield for the first 2 years after application. In Years 3 and 4, the responsiveness of the grass decreased and that of clover increased. Lime increased net N mineralisation by up to 58 kg ha−1, resulting in increased grass growth. Plant P uptake in both gras...