Hydrogen sulfide temperature

If poUed, most aquaculturists would probably indicate a preference for well water. Both freshwater and saline wells are common sources of water for aquaculture. The most commonly used pretreatments of well water include temperature alteration (either heating or cooling) aeration to add oxygen or to remove or oxidize such substances as carbon dioxide, hydrogen sulfide, and iron and increasing salinity (in mariculture systems). Pretreatment may also include adjusting pH, hardness, and alkalinity through the appHcation of appropriate chemicals. 

At ordinary temperatures, mercury is stable and does not react with air, ammonia (qv), carbon dioxide (qv), nitrous oxide, or oxygen (qv). It combines readily with the halogens and sulfur, but is Htde affected by hydrochloric acid, and is attacked only by concentrated sulfuric acid. Both dilute and concentrated nitric acid dissolve mercury, forming mercurous salts when the mercury is in excess or no heat is used, and mercuric salts when excess acid is present or heat is used. Mercury reacts with hydrogen sulfide in the air and thus should always be covered. 

In a reducing atmosphere, molybdenum is resistant at elevated temperatures to hydrogen sulfide, which forms a thin adherent sulfide coating. In an... 

In the acid-leaching process, the oxide ore is leached with sulfuric acid at elevated temperature and pressure, which causes nickel, but not iron, to enter into solution. The leach solution is purified, foHowed by reaction with hydrogen sulfide and subsequent precipitation of nickel and cobalt sulfides. 

Nickel sulfide, NiS, can be prepared by the fusion of nickel powder with molten sulfur or by precipitation usiag hydrogen sulfide treatment of a buffered solution of a nickel(II) salt. The behavior of nickel sulfides ia the pure state and ia mixtures with other sulfides is of iaterest ia the recovery of nickel from ores, ia the high temperature sulfide corrosion of nickel alloys, and ia the behavior of nickel-containing catalysts. 

Gas purification processes fall into three categories the removal of gaseous impurities, the removal of particulate impurities, and ultrafine cleaning. The extra expense of the last process is only justified by the nature of the subsequent operations or the need to produce a pure gas stream. Because there are many variables in gas treating, several factors must be considered (/) the types and concentrations of contaminants in the gas (2) the degree of contaminant removal desired (J) the selectivity of acid gas removal required (4) the temperature, pressure, volume, and composition of the gas to be processed (5) the carbon dioxide-to-hydrogen sulfide ratio in the gas and (6) the desirabiUty of sulfur recovery on account of process economics or environmental issues. 

Preparation. Thiophosgene forms from the reaction of carbon tetrachloride with hydrogen sulfide, sulfur, or various sulfides at elevated temperatures. Of more preparative value is the reduction of trichi oromethanesulfenyl chloride [594-42-3] by various reducing agents, eg, tin and hydrochloric acid, staimous chloride, iron and acetic acid, phosphoms, copper, sulfur dioxide with iodine catalyst, or hydrogen sulfide over charcoal or sihca gel catalyst (42,43). 

Chemical Properties. Although hydrogen sulfide is thermodynamically stable, it can dissociate at very high temperatures. The decomposition thermodynamics and kinetics have been reviewed and the equihbrium constant for the reaction has been deterrnined (101,102) ... 

Anhydrous hydrogen sulfide does not react at ordinary temperatures with metals, eg, mercury, silver, or copper. However, ia the presence of air and moisture, the reaction is rapid, leading to tarnishing ia the case of silver and copper. 

Hydrogen sulfide reacts with molten sulfur and depresses the viscosity of the latter, particularly at 130—180°C iafrared spectral studies show that polysulfanes, H2S, form. The average chain length of these polysulfanes is shorter than the equiUbrium chain length of molten sulfur alone at the same temperature consequendy, the viscosity of the molten sulfur is markedly reduced (99,100). 

Hydrogen sulfide reacts with alcohols under acid-cataly2ed conditions, usually with soHd acidic catalysts at elevated temperatures ... 

Corrosivity. Anhydrous hydrogen sulfide has a low general corrosivity toward carbon steel, aluminum. Inconel, Stehite, and 300-series stainless steels at moderate temperatures. Temperatures greater than ca 260°C can produce severe sulfidation of carbon steel. Alternative candidates for hydrogen... 

Hydrogen sulfide can react with S2CI2 to produce, depending on conditions, a mixture of sulfanes ( 28 where a > 1) or dichlorosulfanes (S Cl2 where x > 2). These compounds tend to be unstable at ambient temperatures. 

Reduction of sulfur dioxide to sulfur includes an industrially important group of reactions (227). Hydrogen sulfide reduces sulfur dioxide even at ambient temperature in the presence of water, but in the dry state and in the absence of a catalyst, a temperature of ca 300°C is required. 

Spent Acid or Burning. Burners for spent acid or hydrogen sulfide are generally similar to those used for elemental sulfur. There are, however, a few critical differences. Special types of nozzles are required both for H2S, a gaseous fuel, and for the corrosive and viscous spent acids. In a few cases, spent acids maybe so viscous that only a spinning cup can satisfactorily atomize them. Because combustion of H2S is highly exothermic, carehil design is necessary to avoid excessive temperatures. 

Sulfur reacts with alkanes to either dehydrate (eq. 1), oxidize, forming carbon disulfide and hydrogen sulfide (eq. 2), or cyclize, forming thiophenes (eq. 3). The products of alkane sulfurization depend on the temperature, the time at the temperature, and the stmcture of the hydrocarbon (1). 

Sulfurization of unsaturated compounds and meicaptans is normally carried out at atmospheric pressure, in a mild or stainless steel, batch-reaction vessel equipped with an overhead condenser, nitrogen atmosphere, an agitator, heating media capable of 120—215°C temperatures and a scmbber (typically caustic bleach or diethanolamine) capable of handling hydrogen sulfide. If the reaction iavolves the use of H2S as a reactant or the olefin or mercaptan is a low boiling material, a stainless steel pressurized vessel is recommended. 

Molecular sieves are typically regenerated using a sHp stream of the treated gas at elevated temperature and reduced pressure. This regeneration step creates an enriched hydrogen sulfide stream which must then be further treated if the sulfur is to be recovered. A typical molecular sieve adsorption unit is shown schematically in Figure 2. 

For feeds greater than 5 mol % hydrogen sulfide, but less than 40 mol %, the Recycle Selectox process can be used. In this variation of the Selectox process, a portion of the process gas leaving the condenser downstream of the Selectox reactor is recycled so as to limit the oudet gas temperature from the reactor to >205 C. 

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