Calcined Magnesite Research Articles

Magnesium availability from kieserite and calcined magnesite on five soils of different pH

Abstract. Five soils from the South of England were incubated with additions of magnesium fertilizers; two also received magnesian limestone. After two years, the recovery of the added magnesium by 0.5 h extraction with 1 m ammonium nitrate was 75–89% for kieserite granules, 64–84% for calcined magnesite powder (< 1 mm), but only 20–41% for calcined magnesite granules (1–3 mm) and 26–32% for ground magnesian limestone. These were all much greater than the Mg dissolved by extracting the fertilizers directly in 1 m ammonium nitrate.In calcareous soils, recovery of Mg was less from the calcined magnesite but most of this reduction was due to its particle size rather than to soil pH.The four magnesium sources are evaluated as fertilizers for agriculture. Kieserite is the most reliable means of raising low soil Mg status.

Flash calcination of a magnesite ore in a free-fall reactor and leaching of magnesia

Flash calcination of a magnesite ore in a free-fall reactor and leaching of calcined magnesite with aqueous carbon dioxide were investigated. The effect of temperature and particle size on the weight loss were observed in the calcination experiments. The maximum weight loss was obtained as 43.2% for the particles of −100 + 140 mesh at the calcination temperature of 850°C. In leaching experiments; leaching temperature and time, particle size, stirring speed, and solid/liquid ratio were selected as variables. The dissolution fraction of magnesium increases with the increase in the leaching time, temperature and to a lesser degree stirring speed. The dissolution also increases with decreasing solid/liquid ratio and particle size. A thermal gravimetric method was used to measure activation energy, preexponential factor and rate constants for the thermal decompositon of the magnesite ore. The activation energy and preexponential factor were calculated as 39.4 kcal mol −1 and 3.5×10 6 s −1, respectively. The rate constants were found to vary between 1.2×10 4 and 1.3×10 −2 s −1 in the temperature range of 823 to 1023 K.

Effects of calcined magnesite, magnesium hydroxide and “geosan” on soil properties in declining spruce stands (NE Bavaria)

Effects of calcined magnesite, magnesium hydroxide and “geosan” on soil properties in declining spruce stands (NE Bavaria)

Leaching behaviour of calcined magnesite with ammonium chloride solutions

The leaching behaviour of calcined magnesite with ammonium chloride has been studied to ascertain the effect of different variables viz. temperature, concentration of ammonium chloride, particle size, calcination temperature, hydration and the effect of calcium chloride addition on the rate of dissolution. The rate of dissolution is not affected by ammonium chloride concentration. The reaction rate mechanism has been discussed in terms of the shrinking core model for spheres. The activation energy for the leaching of particles of −75+63 μm calcined magnesite was found to be about 43.2±0.5 kJ mol −1. It is indicated that the reaction is chemically controlled and the rate is proportional to the inverse of initial size of magnesia particles.

Studies on particle breakage during hydration of calcined magnesite

The paper deals with the process of continuous particle breakage observed during the hydration of calcined magnesite and is studied as a case of substantial comminution of particles under a chemical process. The material studied was magnesite from Chalk Hills of Salem, India, calcined at 700°C and observed under hydration at different temperatures from 30° to 80°C. Starting from a narrow range of particle size (−75 + 63 microns), a rapid degradation of particle size by breakage was observed throughout the progress of hydration. The behaviour of the sample was studied by way of size analysis at various time intervals, the degree of hydration and the determination of variation of number of particles, surface area, etc. during the process. It was not possible to correlate the observed results on the basis of simpler matrix models or common first order equations of the kinetic models. Earlier studies have suggested a mechanism of advancing interface for the reaction with the usual equation obeying 2 3 index law. The present work however indicates that the reaction may not progress inwards by way of an interface, but takes place on a fresh surface made available by breakage. The reaction causes further breakage and a repetitive cycle of breakage, formation of fresh surface and a rapid reaction leading to further breakage appears to be taking place, without appreciable ageing of the hydrated product in the presence of water.

Effects of calcined magnesite, magnesium hydroxide and ?geosan? on soil properties in declining spruce stands (NE Bavaria)

The results of pH-stat.-titrations at six pH levels show increasing reactivities of the fertilizers under investigation in the order magnesite < Geosan < Mg-hydroxide. Further differences exist in the acid neutralization capacity of the three samples. By 3 mo after fertilization, Mg concentrations in soil solution down to 70 cm soil depth significantly increased. Differences between the fertilizers reflect their reactivities. Fertilization increases soil nitrate concentrations by 50 to 100% up to 55 ppm It is unclear why the control plots already show high nitrate contents in soil solution. The top mineral soil shows significant increases of base saturation after fertilization. The highly reactive Mg-hydroxide produces the highest Mg concentrations in the soil solution, whereas the slower soluble magnesite has a stronger effect on the exchange complex.

Comparison of Methods to Determine Relative Bioavailability of Magnesium in Magnesium Oxides for Ruminants

Two Mg balance trials were conducted with wethers to compare relative bioavailability of Mg in several Mg oxides with that of reagent grade sulfate as determined by different methods. In Experiment 1,600ppm Mg as sulfate or four feed grade oxides varying in origin and particle size were added to a semipurified basal diet (200ppm Mg). Diets were fed at 800 g/d to 30 crossbred wethers during the 14-d trial and fecal and urinary collections were made during the last 7 d. In Experiment 2, the basal corn-soybean meal-cottonseed hull diet (1387ppm Mg) was supplemented with 0, 700, 1400, or 2100ppm added Mg as reagent grade sulfate or 1400ppm Mg as three of the oxides from Experiment 1 and fed at 1000 g/d to 35 wethers. Urine was collected daily for 10 d and feces were collected on d 7 through 10. In Experiments 1 and 2, absorption of Mg from the oxide of brine origin and larger particle size distribution was lower than that from sulfate, but there was no difference in absorption for sheep fed oxides derived from sea water or calcined magnesite. In Experiment 2, urinary Mg excretion on d 4 and 5 of the collection was lower for sheep fed the brine oxide than for those fed sulfate or oxide from calcined magnesite. Urinary Mg excretion on d 4 and 5 following addition of 1400ppm Mg to practical diets could be used to predict bioavailability of Mg.

Technical note hydration of calcined magnesite at elevated temperatures under turbulent conditions

The kinetics of the reaction between water and calcined magnesite have been investigated for the effect of different variables viz. temperature, particle size, calcination temperature, magnesium sulphate soaking effect and calcium chloride addition on the rate of hydration. The activation energy is 5+-5 kJ/mol. indicating chemical reaction as the rate controlling process. The preliminary treatment of raw magnesite with MgSO 4 7H 2O prior to calcination did not have any critical effect on the degree of hydration.

High quality chrome-bearing basic refractories from brine magnesia

Abstract Pure magnesia (>96% MgO) was recovered from marine brine of high MgCl2 content using calcined dolomitic magnesite as alkali precipitating agent. High quality chrome-bearing refractories were obtained from clinkers produced by joint fine grinding and firing at 1550°C of the dried Mg(OH)2 paste with different amounts (10, 20, 35 wt. %) of common chrome ore and chemically enriched ore. The technical characteristics of the basic refractories were improved as the chrome content is increased up to 20% common ore and 35% chemically enriched ore. On substituting the common ore by the chemically enriched one the properties of the refractories were remarkably improved due to lower silicate level (about 2%) and higher chrome spinellide content. The properties of the basic refractories were correlated with their different constituent phases.

Beneficiation of calcined satkinsk magnesite through magnetic separation

Because of the fine-grained structure of minerals and the close association of impurities with the periclase, fired magnesite is classified as a raw material which is difficult to beneficiate. We developed a scheme for beneficiating calcined magnesite by dry magnetic separation in a strong field, increasing the quality of regular metallurgical powders, and increasing the yield of granular fractions 2 (3)-1 mm.

The effect of magnesium fertiliser applied to a pumice soil on magnesium concentration in grass herbage

Abstract Application of commercial calcined magnesite at 0, 20,40,60, and 80 kg/ha magnesium on a yellow-brown pumice soil of Mg status adequate for plant growth increased the concentration of Mg in soil and pasture proportional to the rate of Mg applied. Annual applications over 3 consecutive years resulted in a cumulative effect in comparison with the control. There was a measurable residual effect in pasture Mg and soil test values for 3 years after application had ceased. The increases obtained suggest that on hill-country pumice soils, where Mg supplementation by oral or other means to control hypomagnesaemia has severe practical limitations, a pasture Mg level conducive to stock health may be established with 1 or 2 initial applications of 60 – 80 kg/ha maintained by annual inputs of 20 kg/ha.

Magnesium uptake by herbage

AbstractGround carboniferous limestone at 0, 5 and 10 t/ha was applied in all combinations with calcined magnesite at 0, 1.25 and 2.5 t/ha on perennial ryegrass/white clover swards at five sites. an extra treatment of ground magnesian limestone supplying magnesium equivalent to that in 1.25 tonne calcined magnesite was also applied at each site. cuts of herbage were taken over a period of 3 years and samples taken for magnesium and potassium analysis. at two of the sites the herbage samples were divided into grass and clover and analysed separately. calcined magnesite significantly increased the magnesium content of both grass and clover, and in both instances the higher dressing gave a further significant increase in magnesium content over the lower level of application. magnesian limestone was not as effective as calcined magnesite in the first 2 years after application, but had a similar effect on the magnesium content by the third year. 5 and 10 t/ha of ground carboniferous limestone had but a small effect on magnesium levels. this effect was probably of no practical significance. white clover contained, on average, about 25 % more magnesium than perennial ryegrass. the potassium content of clover was little affected by the magnesium and lime treatments, but calcined magnesite depressed the content in grass very slightly and magnesian limestone raised the % k value from 2.72 to 2.88.

Improvements in calcined magnesite as a magnesium fertilizer

SummaryA laboratory and glasshouse study investigated whether it was possible to improve the availability of magnesium from calcined magnesite (MgO). Samples varying from largely unchanged magnesite (MgCO3) to overburnt MgO were made by calcining small quantities of magnesite ore for up to 6 h at several temperatures between 500 and 1000 °C in the laboratory. The effect of calcining conditions on weight loss on ignition, particle size distribution, total, water-soluble and NH4+ -exchangeable Mg was determined and results compared with the current commercial oxide and kieserite (MgSO4. H2O).The results indicated that an oxide could be produced containing nearly double the amount of readily-exchangeable Mg of the oxide used at present. The analysis showed that the most reactive oxide was produced either by burning for 3 h at 700 °C or about half-an-hour at 800 °C, i.e. the minimum time at each temperature for complete conversion of the carbonate to the oxide. Either of these two oxides increased the Mg in plants of the three crops grown in the glasshouse by 0·3% on average, whereas plants given the commercial oxide increased it by only 0·2%. The three crops removed about 70% of the applied Mg from the most reactive oxides but only 50% of the Mg from the commercial oxide. The results of an incubation experiment suggested that burning at 700 °C for 3 h gave a marginally more reactive oxide than the short burn at 800 °C. However, the most reactive oxide produced supplied magnesium at a slower rate than kieserite. This may not necessarily be a disadvantage since most of the soils where Mg deficiency of sugar beet and similar crops is a potential problem need a Mg fertilizer which maintains or gradually increases soil Mg. Thus the improved oxide may bo suitable and a comparison in field experiments of the effects of kieserite and oxides produced under different calcining conditions is needed.

A study of the effectiveness of calcined magnesite as a neutralizing agent for hydrochloric acid in the diet of sheep

1. Five experimental diets were offered ad lib. for 21 d to five sheep in a 5 x 5 Latin-square design experiment as follows: pelleted grass meal alone (control); pelleted grass meal plus hydrochloric acid (470 mmol/kg dry matter (OM); pelleted grass meal plus 470 mmol HCl/kg DM and either an equivalent amount of calcined magnesite (MgO) (235 mmol/kg DM) or twice the amount (470 mmol MgO/kg DM); pelleted grass meal plus 470 mmol MgO/kg DM. 2. MgO supplementation partly prevented the reduction in food intake caused by HCl, being more effective at the low than at the high level. When fed alone, the high level of MgO had a slight adverse effect on food intake. 3. There was no significant treatment effect on either the pH or volatile fatty acid concentrations of rumen fluid. MgO supplementation was only slightly effective in preventing the metabolic acidosis caused by HCl supplementation, as indicated by blood and urine acid-base measurements. 4. With the MgO-supplemented diets, values for the faecal and urinary excretion of magnesium were approximately 70 and 10% respectively of Mg intake and were not significantly affected by HCl supplementation. For rumen fluid, the water-soluble Mg concentration as a percentage of the total Mg concentration was similar for each treatment, approximately 90%. For faeces, the corresponding value was also similar for each treatment, approximately 30%. 5. MgO supplementation altered the effect of dietary HCl on faecal calcium excretion and on the balance of Ca, but did not alter its effect on urinary Ca excretion. 6. It is concluded that the beneficial effect of MgO supplementation on the intake of the HCl-treated diet was related more to its influence on dietary pH than on conditions in the rumen or the acid-base balance of the sheep.

Sources of magnesium for grassland

SUMMARYIn a 3-year field experiment, calcined magnesite, Epsom salt, magnesium ammonium phosphate and magnesian limestone gave only small and non-significant increases in yield of a mixed sward but increased the concentration of magnesium in the herbage at all 11 cuts. Magnesianlimestone increased plant magnesium concentrations less than calcined magnesite, magnesium ammonium phosphate or Epsom salt, all of which had a similar effect; each increment of calcined magnesite gave additional increases in magnesium concentration.Concentration of magnesium in the plant dry matter increased as each season progressed and was linearly related to exchangeable magnesium. At an exchangeable soil magnesium of 1·4 m-equiv./100g soil, Mg concentrations doubled between the first and last cuts. Changes in magnesium concentrations caused by increasing the exchangeable soil magnesium from 0·7 to 1·4 m-equiv./100g soil were less than the seasonal effects.

Effect of potassium fertiliser., soil magnesium status, and soil type on uptake of magnesium by pasture plants from magnesium fertilisers

Abstract Comparisons were made between low rates of dolomite (D) and superphosphate (SP) applied separately or in a dry mixture (SP + D), dolomite- “reverted” superphosphate (DSP), serpentine-reverted superphosphate (SSP), superphosphate plus ground serpentine rock (SR), and superphosphate plus calcined magnesite (MgO), supplying 27.5 to 55kg total Mg/ha, in the presence and absence of K fertiliser, as sources of Mg for uptake by pasture plants in 23 experiments on a range of soil types (pH 5.2 to 6.6) of variable Mg status (0.28 to 4.17 me. exchangeable Mg per 100g soil). Dolomite and ground limestone (L) at 2510 kg/ha were included in 13 experiments. No consistent yield responses were obtained from any of the Mg treatments or L. but some significant K responses were found. Mg concentrations in herbage from control (no Mg) treatments ranged from 0.16 to 0.26% in spring and from 0.23 to 0.35% in autumn. At the low rates used, mean absolute increases in herbage Mg concentrations were very small, ranging fr...

Comparisons of kieserite and calcined magnesite for sugar beet grown on sandy soils

SUMMARYTwenty-three experiments between 1968 and 1971 compared the effect of no magnesium, 50 and 100 kg/ha magnesium as kieserite and 100 and 200 kg/ha magnesium as calcined magnesite, on yield and magnesium uptake by sugar beet. On average, 100 kg/ha magnesium as kieserite increased the mean sugar yield of 7·55 t/ha by 0·17 t/ha whereas 200 kg/ha magnesium as calcined magnesite increased it by only 0·08 t/ha; on fields with less than 15 ppm exchangeable magnesium the magnesium fertilizers increased sugar yield by 0·34 and 0·10 t/ha respectively and there was no response to either fertilizer when the soil contained more than 25 ppm of exchangeable magnesium.100 kg/ha magnesium as kieserite or calcined magnesite increased magnesium in the dry matter of tops by 0·091 and 0·040% and of roots by 0·013 and 0·004% respectively. Giving 100 kg/ha magnesium as kieserite or calcined magnesite increased uptake of the element in August by 5·1 and 2·6 kg/ha respectively. Differences in soil pH did not influence the uptake of magnesium from kieserite but they greatly affected uptake from calcined magnesite. On the slightly acid soils, the fertilizers were almost equally effective but at pH &gt; 7·6 little magnesium was taken up from calcined magnesite. Glasshouse experiments showed that grinding the calcined magnesite increased the availability of the magnesium.

Studies on the amount and composition of digesta flowing through the duodenum of dairy cows. 1. Rate of flow of digesta measured direct and estimated indirect by the indicator dilution technique.

1. Feed intake and the output of faeces, urine and milk were recorded for 8 to 10 days on 2 Friesian cows, with duodenal re-entrant cannulae, receiving hay and concentrates or fresh-mown herbage at the early or mature growth stage. One cow was also given 50 g calcined magnesite daily. During and in the 5 days preceding the collection periods 100 g polyethylene glycol (PEG) and 5.25 g Cr2O3 were given twice daily into the rumen. The digesta were measured and sampled from the re-entrant cannulae for 120 h in the middle of each balance period. All of the administered PEG and Cr2O3 were recovered from the duodenal digesta and faeces. The PEG content of duodenal digesta reached a peak 3 to 4 h after administration, but no diurnal pattern was observed for Cr2O3. The contents of PEG, Cr2O3, DM, Ca and Mg in spot samples of duodenal digesta taken at 2-h intervals agreed well with proportional samples collected during the same hours. (Abstract retrieved from CAB Abstracts by CABI’s permission)

連続自焼成式酸化マグネシウム・炭素陽極を用いるマグネシウムの電解採取に関する研究 (2,000A電解)

A self-baked anode (Söderberg type), which consisted of dntimatemixture of calcined magnesite and carbonaceous binding materials (pitch, tar and creosote), was applied in a 2000 amp magnesium reduction cell containing molten magnesium chloride and sodium chloride.The cell was operated successfully for 143 days at a bath temperature of about 700°C, an average cathodic currentdensity of 1.0A/cm2and an average anodic one of 0.3A/cm2.The results were summarized as follows.1) The cathodic current efficiency was low generally, but it was raised to 71% for the last 24 days, since the operating conditionswere improved. Its maximum value per day became 90%, which was almost the same as that in I. G. Process.2) It was very difficult to collect completely magnesium particles formed at the cathode, because some of. them were finely divided and dispersed in the electrolyte. A black film, which was composed of magnesiumoxide, carbon and iron, sometimes covered the surface of magnesium and disturbed the coagulation of them. Very small magnesium particles were also found in the sludge accumulated on the cell bottom.3) The amount of magnesium oxide consumed practically, by the anode reaction under the best condition, was estimated tobe 70% of that to be consumed theoretically. This and the previous experimental results by authors show that the prebaked anode is preferable to the self-baked anode from the viewpoint of magnesium chloride formation by the reaction of magnesium oxide withchlorine.4) The large cell voltage (about 22V) was necessaryto compensate the heat loss and to keep the bath at constant temperature (about 700°C). The ohmic voltage drop was also verylarge at various contact parts of the cell circuit, therefore a device to minimize it must be considered.5) There have been remained many unclear points in our experiment, and it is possible that we may solve them in a much larger scale electrolysis.

Hypomagnesaemic Tetany in Cattle : I. Incidence, aetiology, diagnosis and treatment

SUMMARY The incidence, aetiology, diagnosis and treatment of hypomagnesaemic tetany are briefly reviewed. Despite the large amount of information gathered over the last 35 years there is still insufficient knowledge of the physiological role of magnesium in the dairy cow, of factors influencing day to day requirements and of the mechanisms involved in the onset of clinical symptoms of tetany in hypomagnesaemic animals. Among the causal factors that can increase the risk of severe hypomagnesaemia are: low availability of magnesium in some foodstuffs, heavy dressings of nitrogenous and potassic fertilizers to grass swards, high milk yields and the absence of any significant mobilizable reserves in the adult bovine. There can be wide variations in magnesium requirements among individuals in a herd and hence considerable variations in serum magnesium levels so that a representative number of blood samples should be taken from survivors for diagnostic purposes; blood samples taken after death are of little diagnostic value. Treatment of the acute phase by injection should be followed by giving calcined magnesite by mouth.