Iron Oxide Dust Research Articles

A New Dry Process for Simultaneous Removal of SO2 and NO from Flue Gas by Powder-particle Fluidized Bed.

A new process, which is a combination of dry processes for flue gas desulfurization and selective catalytic reduction of NOx with NH3 for simultaneous removal of SOx and NOx from the flue gas, was developed using a powder-particle fluidized bed. In the process, SOx was removed by fine sorbent, and NOx was reduced to N2 with NH3 catalyzed by coarse DeNOx catalyst in a powder-particle fluidized bed reactor. The powder-particle fluidized bed was made of a stainless steel tube of 0.053m internal diameter and 1.0m in height above the distributor. Three kinds of fine sorbents, iron oxide dust (a by-product of steel production), sodium-based sorbents (sodium bicarbonate and sodium carbonate), and copper-based sorbents (CuO, CuO•V2O5/Al2O3, and CuO•V2O5•K2SO4/Al2O3), were evaluated in this study. Coarse particles of inactive silica sand and DeNOx catalysts of WO3/TiO2 and V2O5•WO3/TiO2 were used as fluidized medium particles. The effects of various operating conditions and properties of DeSOx sorbent and DeNOx catalyst on removal of SO2 and NO were investigated. The iron oxide dust appeared to be a potential low-cost sorbent for removal of SOx and also a catalyst for reduction of NOx. Both sodium-based and copper-based sorbents had sufficient reactivity for removal of SO2. The powder-particle fluidized bed reactor was effective for simultaneous removal of SOx and NOx from the flue gas. In the proposed process, the simultaneous removal of over 90% of SO2 and NO was achieved by proper combination of fine sorbent and coarse catalyst.

Simultaneous Removals of SO2 and NO in a Powder-particle Fluidized Bed by Using Iron Oxide Dust as Sorbent.

Experiments for simultaneous removals of SO2 and NO were conducted in a laboratory-scale powder-particle Fluidized bed reactor of 0.053m inside diameter and 1.0m in length above the distributor in a temperature range of 573-873K. Fine powders, sorbent of SO2, are continuously fed to the fluidized bed, in which coarse fluidized medium particles are fluidized. Iron oxide dust, a by-product of steel mills which contains considerable amounts of iron oxides, was used as sorbent of SO2 to find a cheap sorbent for removal of SOx. Two kinds of coarse particles of inactive silica sand and active WO3/TiO2 catalyst for removal of NOx were used as particles for fluidized medium. Influences of various operating parameters, including reaction temperature, mole ratio of Fe/S, superficial gas velocity, static height of bed, concentration of SO2 at inlet, concentration of NH3 at inlet and kinds of particles for fluidized medium on removal of SO2 were investigated. Furthermore, the effects of reaction temperature, concentration of NH3 at inlet and kinds of particles for fluidized medium on removal of NO were also studied. Experimental results indicated that the iron oxide dust showed potential capacity as low-cost sorbent of SO2 and weak catalytic activity for reduction of NO. A removal of SO2 of 60% was achieved at temperature of 773K and mole ratio of Fe/S of 3, while a nearly 100% removal of NO was attained when NH3/NO was equal to 1, with the use of catalyst for removal of NOx as particle for fluidized medium.

Behaviour of advanced polymer composites in erosive/corrosive environments

The erosion/corrosion properties of the advanced polymer composites, PMR-15, BMI (Matrimid 5292) and PMR-II-20 have been studied. Specimens of these materials were exposed to jets of an erosion/corrosion medium consisting of salt, iron oxide, quartz and coarse desert dust dispersed in water. The jets impinged on the specimens perpendicular to the plane of the reinforcements for a period of approximately 2 months. The velocity of the jets was measured to be 10 m s −1. The damaged surfaces were examined both visually and under a scanning electron microscope. Damage mechanisms which are associated with this phenomenon are identified. Matrix microcracking, matrix removal and blister formation are the principal damage mechanisms observed. Deep cuts, cutting lines and rust deposition are the main features of the damaged surface. It is observed that BMI matrix composites display a large amount of matrix removal and consequently, fibre exposure. A large amount of scales of deposits are also observed. On the other hand, PMR-15 shows cutting lines, with less matrix removal than BMI. Large scale deposits are also observed on the surface of PMR-15 composite. The PMR-II composite displays the least amount of matrix removal, with brittle matrix microcracking. Blister formation is a dominant corrosive feature of the PMR-II composite.

Health effects of coal mining and combustion: carcinogens and cofactors.

Some polynuclear aromatics (PNA) have been found to be potent carcinogens for all tissues and organs of experimental animals that have been exposed to them, but different dose levels are needed for these effects. They have been known for decades to cause cancer at the site of application but also at certain sites distant from the area of contact. Although some hydrocarbons are potent and complete carcinogens, the majority of related hydrocarbons was originally found to be inactive. Since they generally appear together, it was important to know more about their interaction, particularly whether they would synergize, or antagonize. The polycyclic hydrocarbons have been studied by subcutaneous injection, where they prove very potent carcinogens. They are also very active on the skin of mice where they produce cancer on prolonged application. Inhalation studies, require larger doses yielded negative results until particulate matter was introduced which facilitated the development of lung tumors. Although iron oxide dust was used initially, other dusts were also capable of enhancing the response of the tissue to benzo(a)pyrene carcinogenesis. This point is of importance, particularly since the inhalation of PNA in situations of air pollution or coal mining involves particulates, although of a different type. Soot is not a homogenous substance and several factors determine its properties. Soots will lose some of the absorbed chemicals during their residence in air, but they retain their PNAs for long periods of time when they reach the soil. The carcinogenicity of PNAs in the adsorbed state may be completely absent, depending on particle size of the soot and availability of eluting capability of the tissues or cells in contact with the soot. Whenever the carcinogenic polynuclear aromatics can be eluted they will be active in producing cancer if their residence is adequate. There seems to be no reason to assume that a large increase in coal combustion in the future will by necessity lead to greater risks of cancer to the coal miners or the general urban dweller, because activities to be started now can take into consideration the requirements necessary for control of air pollution in mines as well as in cities. If new uses of coal will be developed, it will be a completely different situation, and statements about the carcinogenic risk from coal utilization do not apply there. Although some of the same carcinogenic PNAs are involved in the health hazards from those processes, other carcinogens and also cocarcinogens will be present, and the exposed workers will not have the apparent benefits of adsorption of PNAs on soot.

Pulmonary function in workers inhaling iron oxide dust.

Lung function studies (static lung volumes, FEV1.0, transfer factor, blood oxygen tension) in fourteen workers (mean age 43 years) exposed (average length 10 years) to pure iron oxide dust did not reveal abnormalities compatible with pulmonary fibrosis, although nodular opacities were present in the chest radiographs. The results seem to support the opinion that pure iron oxide is not fibrogenic in the lung.