Papers by Keyword: Pyrolusite

Abstract: Manganese oxide and metallic manganese have made a long and varied contribution to the production of iron and steel through the centuries, long before Sir Robert Hadfield’s alloy manganese steel first produced in 1882. Although quite well known empirically, this contribution has sometimes been misunderstood or misrepresented.The success of some of the early so-called ‘natural steels’ was the presence of manganese oxides in the iron ores used.Manganese oxide was already used as a flux from the early days of the production of crucible steel in Asia and it now appears that it was used as a flux from the inception of the otherwise very different later European crucible steel technologies. After the introduction of crucible steel making in Britain in the 18^th century, foreign competitors believed that the reason for the success of the processes used at Sheffield was a secret flux and studies on recently discovered 18^th century crucibles in Sheffield have shown that process was indeed fluxed with manganese oxide.The function of manganese in the later European crucible steel industry has been rather overshadowed and confused historically by the very different ‘Carburet of manganese’, a strange concoction, patented by Josiah Heath in 1839 added to iron or steel to purify the metal. At the time the chemistry of the process was misunderstood and many acrimonious and inaccurate claims were made, crucially confusing the very different functions of manganese oxide and manganese metal, overshadowing the part already played by manganese oxide for almost a century previously..Finally manganese and its salts played a crucial role in the Bessemer process of steel making.

Abstract: The effect of rhodochrosite as the annexing agent of pH of pyrolusite slurry on desulfurization and manganese leaching was studied. The influence of the byproduct of sulfuric acid in the sintering flue gas desulfurization process on desulfurization and resource utilization of absorbent was also investigated. The results show that rhodochrosite produced the same effect as a pH buffering agent. High desulfurization and manganese leaching rates were maintained for a long period. This study showed the possibility of resource utilization of low-grade rhodochrosite.

Abstract: This paper studies the preparation of baking-free brick using the tailings of flue gas desulfurization of pyrolusite slurry, aiming to explore the optimal technological conditions. Experimental results show that the particle size of the tailings of flue gas desulfurization of pyrolusite slurry with the concentration up to 95% is below 80μm, which are the appropriate material for the preparation of baking-free bricks. "Byproduct tailings of flue gas desulfurization of pyrolusite slurry - cement cementitious materials - water" system is a relatively good ingredient program. The test results indicate that the flexural and compressive strength of the baking-free brick sample increases with the rise of forming pressure. Appropriately adding the dosage of binder could improve the flexural and compressive strength of the baking-free brick sample, but when it is added to a certain degree, the strength will decrease instead. To sum up, the optimal parameters of the baking-free brick product are shown as follows: desulfurization tailings: cementitious materials = 5:1, the forming pressure is 20 MPa, the moisture content is 10% and the natural curing time is controlled in the range of 7-28 days.

Abstract: Bagasse, a fibrous residue from sugarcane juice extraction, was used as a reducing agent to roast low-grade pyrolusite in N₂. The roasted ore was further leached using sulfuric acid, to convert manganese oxide in the ore to manganese sulfate. The effects of weight ratio of bagasse to manganese ore, roasting temperature, roasting time, leaching temperature, leaching time, stirring speed and sulfuric acid concentration on the leaching recovery of manganese were investigated. Optimal conditions were determined to be a bagasse to manganese ore weight ratio of 0.8:10, roasting temperature of 500°C for 40 min, leaching stirring speed of 100 rpm, sulfuric acid concentration of 3 mol•L^-1 and leaching temperature of 50°C for 40 min. The leaching recovery rate of manganese was up to 97.8% at the optimal conditions.

Abstract: An attempt has been made to study the pretreatment of sulfidic refractory gold ore with pyrolusite. The influences of various parameters were studied to optimize the conditions. The optimum leaching conditions were pyrolusite/gold ore mass ratio of 3.0, H₂SO₄ concentration of 3.0 M, temperature of 100°C, particle size of 45μm, stirring speed of 200 rpm. After the pretreatment, gold and silver were exposed, these made the extraction of the precious metal in the gold ore much easier.

Abstract: A mathematical model for flue gas desulfurization using pyrolusite pulp in jet bubbling reactor (JBR) was described. Firstly, based on the concept of two stages mass balance with chemical reaction, two models were set up, for jet bubbling zone and rising bubble zone, respectively, according to the construction of JBR. The models consist of two coupling differential equations and were solved simultaneously by integral and separation of the variables. Then the SO2 absorption efficiency expression was developed, considering the great discrepancy existing between the gas-side mass transfer coefficients of the jet bubbling zone and gas bubble rising zone. The final expression associates SO2 absorption efficiency with process conditions and JBR structure parameters, which can give some instruction and guidance for the study of reactor operation process. Predicted results from the theoretical model, including effect of pH value of the pulp, flue gas temperature and inlet SO2 concentration of flue gas on SO2 absorption efficiency, were found to be in good agreement with experimental data obtained in a jet bubbling reactor. The model provides a basis for the process scale up and operating guide.

Abstract: It’s a gas-liquid-solid three-phase reaction system in the reactor for flue gas desulfurization using pyrolusite pulp. Based on the two-film mass transfer theory and shrine core model, the macro-kinetics of flue gas desulfurization using pyrolusite pulp in a double magnetic stirred reactor were investigated. The effects of diffusion in solid film, surface chemical reaction, diffusion in liquid phase and gas phase of the process, have been carried out to distinguish the control step of the process. It was observed that SO2 absorption efficiency increased with the decreasing of pyrolusite particle size and varied gently when the pyrolusite particle diameter decreased to 0.18mm. SO2 absorption efficiency increased not significantly along with the increase of temperature and the liquid phase stirring speed but increased significantly along with the increase of the gas phase stirring speed. Experiment results showed that under simulated industrial conditions, gas phase diffusion was the control step compared to other related factors, given that pyrolusite particle diameter was kept below 0.1mm.