Mechanism of phosphorus removal in beneficiation of high phosphorous oolitic hematite by direct reduction roasting with dephosphorization agent

High phosphorous oolitic hematite ore is one of typical intractable iron ores in China, and the conventional beneficiation methods are found to be impracticable to , remove phosphorus from the ore effectively. Better beneficiation index were gotten by direct reduction roasting with dephosphorization agent followed by two stages of grinding and magnetic separation. P content decreases from 0.82% in the raw ore to 0.06% in the magnetic concentrate, and the total iron grade increases from 43.65% to 90.23%, the recovery of iron can reach 87%. Mechanisms of phosphorus removal in the beneficiation of high phosphorous oolitic hematite ore by direct reduction roasting with dephosphorization agent were studied using XRD, SEM and EPMA. The results showed that about 20% of the apatite in the raw ore transferred into phosphorus and volatilized with the gas in the process of reduction roasting, while the rest 80% apatite was not involved in the reaction of generation of phosphorus, and remained as apatite in the roasted products, which was removed to tailings by grinding and magnetic separation. A small amount of phosphorus existed in the magnetic concentrate as apatite. The oolitic texture of raw ore was partly changed during roasting, resulting in the formation of nepheline in the reaction between the dephosphorization agent, SiO2 and Al2O3 in the raw ore, which greatly improved the liberation degree of minerals in the roasted products, and it was beneficial to the subsequent grinding and magnetic separation.

Differentiation of Barley Genotypes with High Phosphorus Efficiency under Low Phosphorus Stress

[Objective] This study aimed to investigate differences in phosphorus effi-ciency between two-rowed barley and multiple-rowed barley and differences in phos-phorus efficiency among various agronomic traits, and to explore the relationship be-tween agronomic traits and row type with phosphorus efficiency. [Method] Under available phosphorus mass fractions of 1.32 and 36.6 mg/kg, 172 barley varieties, including 79 two-rowed foreign barley, 22 multiple-rowed foreign barley, 58 two-rowed Chinese barley and 13 multiple-rowed Chinese barley, were selected to com-pare differences in phosphorus efficiency-related agronomic traits. Plant height, spike length, number of unfil ed grains, number of unfil ed grains, main panicle weight, to-tal panicle weight, total stem weight, weight of aerial part and heading stage were surveyed for statistical analysis. [Result] The results showed that, various agronomic traits were larger under fertilization condition than under non-fertilization condition ex-cept number of unfil ed grains and heading stage. Plant high, spike length, weight of aerial part and heading stage varied greatly under non-fertilization condition; number of fil ed grains, number of unfil ed grains and total stem weight varied greatly under fertilization condition. In two-rowed barley, plant height and number of fil ed grains of Chinese varieties were higher than those of foreign varieties, while other agronomic traits such as spike length, number of unfil ed grains, main panicle weight, total panicle weight, total stem weight, weight of aerial part and heading stage of foreign varieties were higher than those of Chinese varieties. Spike length and weight of aerial part in multiple-rowed and two-rowed foreign barley were higher than those in Chinese barley. In multiple-rowed barley, plant height, number of unfil ed grains, total panicle weight and total stem weight of foreign varieties were higher under non-fer-tilization condition and lower under fertilization condition compared with those of Chi-nese varieties; number of fil ed grains, main panicle weight and heading stage of foreign varieties were lower under non-fertilization condition and higher under fertil-ization condition compared with those of Chinese varieties. [Conclusion] Heading stage, number of fil ed grains, number of unfil ed grains and total stem weight are more sensitive to phosphorus efficiency. Multiple-rowed barley is more sensitive to phosphorus efficiency than two-rowed barley.

Effect of coal levels during direct reduction roasting of high phosphorus oolitic hematite ore in a tunnel kiln

The effect of coal levels on phosphorus removal from a high phosphorus oolitic hematite ore after direct reduction roasting have been investigated. Raw ore, coal, and a dephosphorizatiou agent were mixed and the mixture was then roasted in a tunnel kiln. The roasted products were treated by two stages of grind- ing followed by magnetic separation. XRD and SEM-EDS examination of the products was used to analyze differences in the roasted products. The results show that coal is one of the most important factors affect- ing the direct reduction roasting process. When the inner coal levels increased from 0% to 15% the iron grade decreased linearly from 94.94%to 88.81% and the iron recovery increased from 55.94% to 92.94%. At the same time the phosphorus content increased from 0.045% to 0.231%. Increasing the inner coal levels also caused more hematite to be reduced to metallic iron but the oolitic structure of the roasted product was preserved in the presence of high coal loading. The phase of the phosphorus in raw ore was not changed after direct reduction roasting. The effect of coal on the phosphorus content in the H-concentrate arises from changes in the difficulty of mechanically liberating the metallic iron from the phosphorus bearing minerals.

Mixture of ilmenite and high phosphorus iron ore smelted by oxygen-enriched top-blown smelting reduction

In order to reasonably utilize the abundant resources of high-phosphorus iron ore and ilmenite in China, the technology of top-blown smelting reduction with oxygen enrichment was used to smelt the mixed ore of high-phosphorus iron and ilmenite. The effect, which is related to basicity, reduction temperature, carbon-oxygen ratio and time of ventilated oxygen to iron recovery, dephosphorization rate, content of iron, phosphorus, sulfur and titanium in pig iron, was investigated in the experiment. The results show that an ideal outcome can be gained in condition of 6：4 ration on Mengqiao concentrate and Huimin iron ore, temperature of 1 500℃, basicity of 1.3, 1.0 on molar ration of carbon to oxygen, time of 10 min on blowing-oxygen. The outcome is that there is no foamy slag in generation, a good separation of slag and iron, iron recovery with 91.41%, content of phosphorus with 0.27% and tilanium content less than 0.001%, The atmosphere of strong oxidizing in the upper of reduction container and high potential of oxygen in the composition of slag in this technique bring phosphorus, titanium and silicon into slag, which ensures less content of impurity in pig iron.

Effects of FeNi-phosphorus-carbon system on crystal growth of diamond under high pressure and high temperature conditions

This paper reports the crystal growth of diamond from the Fe Ni–Carbon system with additive phosphorus at high pressures and high temperatures of 5.4–5.8 GPa and 1280–1360°C. Attributed to the presence of additive phosphorus,the pressure and temperature condition, morphology, and color of diamond crystals change obviously. The pressure and temperature condition of diamond growth increases evidently with the increase of additive phosphorus content and results in the moving up of the V-shape region. The surfaces of the diamonds also become coarse as the additive phosphorus added in the growth system. Raman spectra indicate that diamonds grown from the Fe Ni-phosphorus-carbon system have more crystal defects and impurities. This work provides a new way to enrich the doping of diamond and improve the experimental exploration for future material applications.

Indigenous arbuscular mycorrhizal fungi play a role in phosphorus depletion in organic manure amended high fertility soil

The species richness and propagule number of arbuscular mycorrhizal fungi(AMF)are high in intensively-managed agricultural soils.Past research has shown that AMF improve crop phosphorus(P)uptake under low soil P conditions,however it is unclear if AMF play a role in high Olsen-P soils.In this study,we investigated whether native fungal benefits exist under high P input field conditions in-situ and contribute to P utilization.We installed in-grow tubes which were sealed with different membrane pore sizes(30 or 0.45μm)to allow or prevent AMF hyphae access to the hyphal compartment and prevent cotton roots from penetrating the chamber.We used the depletion of soil available P(Olsen-P)in the hyphae accessed compartment to indicate P uptake by the native AMF community.Our results showed that the native AMF mediated P depletion and microbial biomass P(MBP)turnover and caused the largest Olsen-P depletion ratio and MBP turnover ratio in the high P treatments(Olsen-P:78.29 mg kg^(-1)).The cotton roots in each fertilization regime were colonized by a unique AMF community and Glomus and Paraglomus were the dominant genera,implying the longterm fertilization regimes domesticated the AMF community.We conclude that native AMF caused the P depletion and P turnover even under high soil Olsen-P conditions.

Microwave Assisted Liberation of High Phosphorus Oolitic Iron Ore

The influence of microwave treatment on the liberation of iron ore from the high phosphorus oolitic iron ore from Aswan region, Egypt was studied. The effect of microwave power, exposure time and grain size on the liberation of iron ore was investigated. The microfractures and cracks of the samples were characterized before and after microwave treatments. The heating rate of high phosphorus oolitic iron ore was studied. Crystallinity of hematite was characterized before and after microwave pretreatment. The results indicated that intergranular fractures formed between the gangues (fluorapatite and chamosite) and hematite after microwave treatment, leading to improved liberation of iron ore and a significant reduction in comminution energy. Percentages of fraction ≤ -0.125 mm increased from 46.6% to 59.76% with increased exposure time from 0 to 60 seconds. The heating rate of iron ore showed that microwave treatment was less efficient at smaller particle sizes for a fixed applied power density. Crystallinity of hematite increased with the microwave exposure time.

EFFECT OF HIGH TEMPERATURE REPRESSING ON PHOSPHORUS SEGREGATION IN 93W-4.5Ni-2.5Fe ALLOY

The influence of high temperature repressing treatment on the segregation of phosphorus in the 93W alloy was carefully investigated by means of Auger electron spectroscope,EPMA, TEM and SEM.The segregation of phosphorus has been observed at the tungsten-tungsten grain boundaries,particularly at the tungsten-matrix interphases when the specimens were kept at the temperature in the range of 1200—1500℃ ,followed by furnace cooling.However, no segregation of phosphorus was observed at the interfaces after the specimens were re- pressed at the range of temperature,followed by furnace cooling.After investigation,the dis- locations in the matrix phase of as-repressed specimens directly influenced the phosphorus segregation to the interfaces.After annealing,the mechanical properties were reduced because of the phosphorus segregation at the interface boundaries.

Corrosion and Penetration Resistance of Corundum Bricks to High Phosphorus Oolitic Hematite Reducing Materials

The paper aims at investigating whether corundum bricks can be used for the bottom, of the direct reduction furnace of high phosphorus oolitic hematite. The reducing materials including high phosphorus oolitic hematite, bitumite, Ca（OH） 2 and Na2CO3 at a mass ratio of 1：0. 15：0. 15：0. 03 were mixed and pressed into carbon containing cylindrical specimens with the size of Ф15 mm × 20 mm. The specimens were placed on the corundum bricks and reduced in a high temperature tube furnace at 1 200 ℃ for 40, 60, 80, 140 and 220 min, respective- ly. The corrosion and penetration resistance of corundum. bricks to high phosphorus oolitic hematite reducing materials were analyzed with XRD, SEM and EDS. It shows that the reducing slag formed in the reduction process corrodes the surface of corundum bricks to form a product layer of anorthite and hercynite, retarding the further corrosion of the reducing slag; the reducing slag which has penetrated into the interior of the brick goes through the gaps between the particles and generates anorthite and hercynite, filling the gaps and hindering the reducing slag penetration.

Influence of phosphorus in high strength steel on welding quality in laser welding

P-added high strength IF steel M250P1 is widely used in vehicle body and safety parts because of its good mechanical performance and forming properties.Experiments of high power laser welding of 4.8 mm thick P-added high strength IF steel M250P1 is performed by using a 12 kW CO_2 laser.In order to investigate the effects of phosphorus in high strength steel on the quality of welding,the Cupping and tensile tests,optical and SEM energy dispersive spectrometer analysis have been done on three welded joints.Some results have been obtained below.In the given welding parameters,the welded joints show good tensile and forming properties.However,it has been also found that the cracking is easy to occur in the fusion zone of welded joint during deformation.Some research works have been done.The results show that the fast cooling of fusional metal leads to the phosphorus microsegregation in the fusion zone because of relative low diffusion rate of phosphorus,which brings about the poor toughness of welded joints.

Reduction Characteristics of High Phosphorus Iron Ore in Reducing Parameters Similar to Blast Furnace Conditions

The strong global demand for iron and steel has necessitated the utilization of various low grade iron ores, which are not suitable for direct utilization in ironmaking processes. The low grade iron ores cannot be dressed effectively using the traditional mineral processing methods because of complicated min-eral compositions. The main problem associated with exploiting these deposits is the dissemination of fine silicate minerals and the high level of phosphorus content due to the poor liberation of iron minerals from the gangues. The pre-sent manuscript is aimed to investigate reduction properties of iron ores rich in phosphorous in order to study the suitability of using these ores in iron blast furnace. Representative technological samples of iron ore are collected from Eastern South Aswan iron ore mine in Egypt. The principal gangue contents are SiO2 7.76%, and P2O5 1.13%. Iron and phosphorus exist in the form of hematite 78% and apatite respectively. The ore was fired at 1000°C for 3 hours. The green and fired samples were isothermally reduced at conditions which closely represent the theoretical reduction conditions in different zones of blast furnace. The influence of reduction conditions on the reduction behaviour and the morphology of the reduced samples were investigated. After reduction apatite is changed to Calcium phosphate beside fayalite and quartz. The reduction rate of fired samples is greater than that for the green ones and that was confirmed by morphological examination. At cohesive zone condition, the effect of firing on reduction characteristics cannot be distinguished.

Preparation of High Activity Admixture from Steel Slag,Phosphate Slag and Limestone Powder

The problem of low disposal and utilization rate of bulk industrial solid waste needs to be solved.In this paper,a high-activity admixture composed of steel slag-phosphate slag-limestone powder was proposed for most of the solid waste with low activity and a negative impact on concrete workability,combining the characteristics of each solid waste.The paper demonstrates the feasibility and explains the principle of the composite system in terms of water requirement of standard consistency,setting time,workability,and mechanical properties,combined with the composition of the phases,hydration temperature,and microscopic morphology.The results showed that the steel slag:phosphate slag:limestone=5:2:3 gave the highest activity of the composite system,over 92%.Besides,the composite system had no significant effect on water demand and setting time compared to cement,and it could significantly increase the 7 and 28 d activity of the system.The composite system delayed the exothermic hydration of the cement and reduced the exothermic heat but had no effect on the hydration products.Therefore,the research in this paper dramatically improved the solid waste dissipation in concrete,reduced the amount of cement in concrete and positively responded to the national slogan of carbon neutral and peaking.

Metal-free two-dimensional phosphorene-based electrocatalyst with covalent P-N heterointerfacial reconstruction for electrolyte-lean lithium-sulfur batteries

The use of lithium-sulfur batteries under high sulfur loading and low electrolyte concentrations is severely restricted by the detrimental shuttling behavior of polysulfides and the sluggish kinetics in redox processes.Two-dimensional(2D)few layered black phosphorus with fully exposed atoms and high sulfur affinity can be potential lithium-sulfur battery electrocatalysts,which,however,have limitations of restricted catalytic activity and poor electrochemical/chemical stability.To resolve these issues,we developed a multifunctional metal-free catalyst by covalently bonding few layered black phosphorus nanosheets with nitrogen-doped carbon-coated multiwalled carbon nanotubes(denoted c-FBP-NC).The experimental characterizations and theoretical calculations show that the formed polarized P-N covalent bonds in c-FBP-NC can efficiently regulate electron transfer from NC to FBP and significantly promote the capture and catalysis of lithium polysulfides,thus alleviating the shuttle effect.Meanwhile,the robust 1D-2D interwoven structure with large surface area and high porosity allows strong physical confinement and fast mass transfer.Impressively,with c-FBP-NC as the sulfur host,the battery shows a high areal capacity of 7.69 mAh cm^(−2) under high sulfur loading of 8.74 mg cm^(−2) and a low electrolyte/sulfur ratio of 5.7μL mg^(−1).Moreover,the assembled pouch cell with sulfur loading of 4 mg cm^(−2) and an electrolyte/sulfur ratio of 3.5μL mg^(−1) shows good rate capability and outstanding cyclability.This work proposes an interfacial and electronic structure engineering strategy for fast and durable sulfur electrochemistry,demonstrating great potential in lithium-sulfur batteries.

Surface Reactivity in Tropical Highly Weathered Soils and Implications for Rational Soil Management

Highly weathered soils are distributed in the humid and wet-dry tropics, as well as in the humid subtropics. As a result of strong weathering, these soils are characterized by low activity clays, which develop variable surface charge and related specific properties. Surface reactions regarding base exchange and soil acidification, heavy metal sorption and mobility, and phosphorus sorption and availability of the tropical highly weathered soils are reviewed in this paper.Factors controlling surface reactivity towards cations and anions, including ion exchange and specific adsorption processes, are discussed with consideration on practical implications for rational management of these soils. Organic matter content and pH value are major basic factors that should be controlled through appropriate agricultural practices, in order to optimise favorable effects of colloid surface properties on soil fertility and environmental quality.

Simultaneous nitrogen and phosphorus removal under low dissolved oxygen conditions

A full-scale test was operated by using low dissolved oxygen activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of CODCr, TN and TP varied in a range of 352.9 mg/L-1338.2 mg/L, 34.4 mg/L-96.3 mg/L, and 2.21 mg/L-24.0 mg/L, the average removal efficiencies were 94.9%, 86.7% and 93.0%, respectively. During the test period of two months, effluent meas of CODCr,, BOD5, NH3-N, TN and TP were below 50 mg/L, 25 mg/L, 10 mg/L and 1.0 mg/L respectively. The low dissolved oxygen activated sludge process has a simple flow sheet, fewer facilities and high N and P removal efficiency. It is very convenient to retrofit the conventional activated sludge process with the above process.

Nitrogen and phosphorus removal under intermittent aeration conditions

A practice wastewater treatment plant was operated using intermittent aeration activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of COD Cr , BOD 5, TN, TP, NH 3\|N, TKN, and SS varied in a range of 207.5—1640 mg/L, 61.8—637 mg/L, 28.5—75.6 mg/L, 4.38—20.2 mg/L, 13.6—31.9 mg/L, 28.5—75.6 mg/L, and 111—1208 mg/L, the effluent means were less than 50 mg/L, 20 mg/L, 5 mg/L, 1.0 mg/L, 5 mg/L, 10 mg/L, and 20 mg/L, respectively. Based on a long time of operating results, this process is very suitable for nutrient biological removal for treating the municipal wastewater those water characteristics are similar as that of the Songjiang Municipal Waste Water Treatment Plant(SJMWTP).

Effective removal of phosphorus from high phosphorus steel slag using carbonized rice husk

High phosphorus steel slag and carbonized rice husk are two common wastes characterized by high generation and low secondary use values.Through the reduction of high phosphorus steel slag by biomass,both wastes were fully utilized,thus reducing the negative impact on the environment.In this study,variables such as temperature,time,and amount of reactants were changed to determine the optimal conditions for the reaction of steel slag with carbonized rice husk at high temperatures.The actual amount of reducing agent consumed during the reduction was significantly greater than that predicted by theoretical calculations.Adding three carbon equivalent of carbonized rice husk and maintaining at 1500℃ for 30 min could remove 79.25% of P_(2)O_(5) in the slag.By modeling the material cycle in which high phosphorus steel slag was treated with biomass,the product could be used for crop growth.Meanwhile,the reduced iron and residual steel slag can be used tomake steel again,thereby leading to a sharp reduction in fossil fuel usage and greenhouse gas emissions in this process.

Pre-anoxic/Orbal Oxidation Ditch/Rotary Disc Filter Treatment of Mixed Sewage in Industrial Park

The design scale of a sewage treatment plant in the industrial center of a district in Changzhou is 2×10^(4) m^(3)/d. Data analysis, process selection and analysis and main structure design were carried out for the sewage treatment plant to ensure that the effluent quality meets the discharge standards. The operation results after the implementation of the project show that the project can effectively improve the effluent quality of the sewage treatment plant. The removal rates of COD, NH+4, TN and TP are 93.97%, 98.63%, 82.67% and 97.37% respectively, and the effluent quality can be discharged stably up to the standard. Using cost analysis to study the operation of the sewage treatment plant, the results show that the total investment of the sewage treatment plant is 40 million yuan, the electricity cost of this project is 0.426 yuan/m^(3), the pharmaceutical cost is 0.655 yuan/m^(3), and the material replacement fee is 0.323 yuan/m^(3). The direct operating cost is 1.404 yuan/m^(3). This method has good practical guiding significance for the optimization and operation transformation of the same type of sewage treatment plants.

Removal of Phosphorus From High Phosphorus Iron Ores by Selective HCl Leaching Method

The selective HCl leaching method was used to remove phosphorus from high phosphorus iron ores. The hydroxyapatite in high phosphorus iron ores was converted into soluble phosphate during the process of HCl leaching. The effects of reaction time,particle size,hydrochloric acid concentration,reaction temperature,liquid-solid ratio and stirring strength on the dephosphorization ratio were studied. The results showed that the dephosphorization ratio can exceed 98% under the conditions of reaction time 30-45 min,particle size 0.147 mm,hydrochloric acid concentration 2.5 mol/L,reaction temperature 25 ℃,liquid-solid ratio 5：1 and stirring strength 5.02-12.76 s-1. After dephosphorization reaction,the content of phosphorus in iron ore complied completely with the requirements of steel production.

Phosphorus Removal of High Phosphorus Iron Ore by Gas-Based Reduction and Melt Separation

A new method （gas-based separation plus melt separation） has been proposed to remove phosphorus of the high phosphorus iron ore which was 1.25 % of phosphorus content and 50. 0% of iron content. HSC chemistry package and the coexistence theory of slag structure were adopted for theoretical analysis. The gas-based reduction was carried out using a fixed bed reactor and the ore sample of 80 g with an average particle size of 2 mm were reduced using CO or H2 at temperature of 1 073 K for 5 hours. 50 g of the reduced sample with 3.0% CaO as additive was then subjected to melt separation in an electric furnace at temperature of 1 873 K under Ar atmosphere. In each run, SEM, EDS, optical microscopic examination and chemical analysis of the reduced ore sample, the metal sample and the slag sample were conducted. Results of all gas-based reduction experiments showed that iron metallization ratios were some 65% and the phosphorus compounds in the ore remained unchanged. It was agreed well with the simula- tions except for the iron metallization rate being less than predicted value; this difference was attributed to kinetics. Results of melt separation experiments showed that P content in metal samples is 0.33% （metal sample from H2 reduction product） and 0.27% （metal sample from CO reduction product）. The phosphorus partition ratios of both cases were less than predicted values. Some P in the metal samples existed as slag inclusion was considered to be the reason for this discrepancy.