Particles iron sulfide

Yagi et al. (1951) roasted pyrrhotite (iron sulfide) particles dispersed in asbestos fibers and found that the time for complete conversion was related to particle size as follows ... 

We often observed a pressure-drop increase in the first bed. The solid line in Figure 7 shows a typical curve of a pressure-drop increase in the first bed of the commercial reactor. The pressure drop starts increasing half way into the run and rises exponentially with time. The unit has to be shut down before the pressure-drop reaches the limitation. When we first experienced a serious pressure-drop increase, we observed that the fines of iron sulfide plugged the voidage of the bed surface. The iron sulfide particles suspended in the feedstock are so fine that most of... 

Figure 5 illustrates microbial corrosion by SRB (63). The corrosion products FeS and Fe(OH)2 flow with the injection water as suspended solids. They deposit in the formation and cause significant reduction in the injectivity of water injection wells (64). The presence of SRB is characterized by the formation of tiny black iron sulfide particles and hydrogen sulfide smell is interesting to note. Sulfate-reducing bacteria... 

Davison, W., Grime, G.W., Woof, C., 1992. Characterization of lacustrine iron sulfide particles with proton-induced X-ray emission. Limnol. Oceanogr. 37, 1770-1777. 

Suspended solids and polymers generally tend to stabilize foams. One example is iron sulfide particles in amine solutions (26, 239, 318) also see item 7 above. In one case (107), precipitation of sodium chloride in a solvent-water separation column caused foaming. 

This tower was used to steam-strip hydrogen sulfide from an amine solution. This is a somewhat corrosive service. Thus, iron sulfide particles (products of corrosion) accumulate in the circulating amine solution. The regenerator was equipped with stainless steel valve trays. It had been onstream for three years before the trouble started. 

Particulate matter reduces the surface tension of liquids and thus promotes foaming. A common example of this in a refinery is flooding of amine scrubbers due to iron sulfide particles in the circulating solution. A system which utilizes a circulating liquid that suddenly exhibits a carryover problem is probably subjected to foaming. Check the circulating liquid for particulate content. Examples of this are sulfuric acid recycle in alkylation units and closed hot-oil reboiler systems on gas plants. 

A portion of the rich amine flows through a particle filter and a carbon bed filter. The particle filters remove dirt, rust, and iron sulfide The carbon filter, located downstream of the particle filters, remo cs residual hydrocarbons from the amine solution. 

It is found that the dissolution of zinc sulfides occurs more rapidly when they are in contact with copper sulfide or iron sulfide than when the sulfides of these types are absent. This enhancement is brought about by the formation of a galvanic cell. When two sulfide minerals are in contact, the condition for dissolution in acidic medium of one of the sulfides is that it should be anodic to the other sulfide in contact. This is illustrated schematically in Figure 5.3 (A). Thus, pyrite behaves cathodically towards several other sulfide minerals such as zinc sulfide, lead sulfide and copper sulfide. Consequently, pyrite enhances the dissolution of the other sulfide minerals while these minerals themselves understandably retard the dissolution of pyrite. This explains generally the different leaching behavior of an ore from different locations. The ore may have different mineralogical composition. A particle of sphalerite (ZnS) in contact with a pyrite particle in an aerated acid solution is the right system combination for the sphalerite to dissolve anodically. The situation is presented below ... 

In the case of roasting, the pretreatment process destroys the sulfide matrix by driving off sulfur from the structure. This results in the formation of iron oxide particles that are made of concentrically zoned and porous hematite and maghemite (Paktunc et al. 2006). Arsenic is volatilized as As203 and oxidised to... 

Some of the discharged sulfide particles settle onto the chimney s exterior, where they are buried by the outward growth of anhydrite. Sulfide precipitation within the chimneys, causes copper, zinc, and iron sulfides to deposit and partially replace the anhydrite. Chimneys can build to several meters in height and their orifices range in diameter from 1 to 30 cm. Both the smoke and the chimneys are composed of polymetallic sulfide minerals, chiefly pyrrhotite (FeS), pyrite (FeS2), chalcopyrite (CuFeS2), and sphalerite or wurtzite (ZnS). 

Hydrogen sulfide is removed form coal gas by contact with a moving bed of iron oxide particles which convert to the sulfide as follows ... 

Hydrogen sulfide is removed from coal gas by passing the gas through a moving bed or iron oxide particles. In the coal gas environment (consider uniform) the solids are converted from Fe203 to FeS by the SCM/reaction control, T = 1 hr. Find the fractional conversion of oxide to iron sulfide if the RTD of solids in the reactor is approximated by the E curves of Figs. P26.ll-P26.14. 

The most conventional catalytic material since the work of Bergius has been iron sulfide in various types. Pyrite, pyrrhotite, and various nonstoi-chiometric sulfides are known, and pyrrotite is postulated as the active form. Its precursors are red mud, residue of bauxite after the separation of alumina, iron ores of various sources, synthetic and natural pyrites, fine iron particles, iron dust from converters, iron sulfate, iron hydroxide, etc. (32, 33). 

Very fine particles of iron sulfide is one class of very promising catalysts because of lower cost and moderate activity. Presulfiding treatments for activation, ion exchange, and dispersed impregnation of catalysts or catalyst precursors are combined to enhance the catalytic activity and reduce the amount of catalyst required (69, 70). 

The presence of solids further complicates the performance requirements for a demulsifier. Emulsions stabilized by fine particles can usually be broken if the wettability of the particles is reversed. Inorganic particles, such as iron sulfides or clay minerals, can be made water-wet, causing them to leave the interface and diffuse into the water phase, or they can be made oil-wet so that they leave the interface and diffuse into the oil phase [68]. Organic particles, such as paraffins and asphaltenes, can be removed from interfaces by dissolution [461,463,466]. 

The thermal film made of long-chain zinc polyphosphates is formed on the surface. When friction increases, the process of transformation of phosphorus compounds into short-chain phosphate glasses is observed and iron sulfide abrasive particles are eliminated by tribochemical acid-base reactions. Under very severe wear conditions (nascent metal surface creation), an iron sulfide is formed, which will be mixed with the phosphate glasses tribofilm. 

The iron sulfide used in the experiment was obtained from the thermal decomposition of pyrite(FeS2). The particles were extremely porous, with pores sizes of several tens of microns. In contrast, the reaction behavior obtained with natural pyrrhotite or synthetic FeS composed of fine particles, gave much worse results. Thus, the influence of the specific surface area of a solid on the formation behavior was thought to be important. 

The concentrate was composed of fine chalcopyrite particles of ca. 50 micron. The maximum H2 concentration in both the normal and reduced pressure cycles was larger than the value obtained with iron sulfide. The results are shown in Figure 3. 

Figure 2.2 A GEMS particle found in an IDP, consisting of a glassy matrix with silicate-like composition and embedded nanometer-sized inclusions of iron metal and iron sulfide (dark patches). Some of them are possibly interstellar silicate dust grains. (From NASA http //stardust.jpl.nasa.gov/science/sci2.html.)...

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