Sulfur combustion

First Alternative. Figure 1 illustrates the first of the two alternative production processes. Here the mother Hquor from the sodium nitrate crystallization plant, normally containing about 1.5 g/L iodine as iodate, is decanted for clarification and concentration homogenization. From there the solution is spHt into two fractions. The larger fraction is fed into an absorption tower where it is contacted with SO2 obtained by sulfur combustion. In the absorption tower iodate is reduced to iodide according to the following reaction ... 

Sulfur oxides resulting from fuel sulfur combustion often inhibit catalyst performance in Regions II, III, and a portion of Region IV (see Fig. 7) depending on the precious metals employed in the catalyst and on the air/fuel ratio. Monolithic catalysts generally recover performance when lower sulfur gasoline is used so the inhibition is temporary. Pd is more susceptible than Rh or Pt. The last is the most resistant. Pd-containing catalysts located in hotter exhaust stream locations, ie, close to the exhaust manifold, function with Httie sulfur inhibition (72—74). 

By-product processing Hydrogen sulfide Conversion to elemental sulfur or sulfuric acid by liquid absorption, wet oxidation to elemental sulfur, combustion to SO2... 

It has been shown in these studies that the principal, and probably only significant source of NDMA, is malt which had been dried by direct-fired drying (21, 73). It is well known that malts kilned by indirect firing have either low or non-detectable levels of NDMA (74). Consequently, changes in malting procedures have been implemented in both the U.S. and Canada which have resulted in marked reductions in N-nitrosamine levels in both malts and beer (70,74). For example, sulfur dioxide or products of sulfur combustion are now used routinely by all maltsters in the U.S. to minimize N-nitrosamine formation (70). The Canadian malting industry, on the other hand, has... 

It is important and beneficial for the environment to reduce the sulfur levels in refinery products, as well as in energy fuel (e.g. natural gas, LPG and heating oil) [1]. It has been previously reported that atmospheric emission of sulfur combustion products contributes to acid rain, ozone, and smog generation. 

There is much concern about the emissions which result when fuel sulfur combusts (i.e., sulfur oxides). These gaseous products further react to form environmental pollutants such as sulfuric acid and metal sulfates. Active sulfur and certain sulfur compounds can corrode injection systems and contribute to combustion chamber deposits. Under low-temperature operating conditions, moisture can condense within the engine. Sulfur compounds can then combine with water to form corrosive acidic compounds. 

Sulfur burning furnaces are 2 cm thick cylindrical steel shells lined internally with 30 to 40 cm of insulating refractory, Fig. 3.3. Air and atomized molten sulfur enter at one end. Hot S02, 02, N2 gas departs the other into a boiler and steam superheater (Fig. 3.4). Some furnaces are provided with internal baffles. The baffles create a tortuous path for the sulfur and air, promoting complete sulfur combustion. Complete sulfur combustion is essential to prevent elemental sulfur condensation in downstream equipment. 

Fig. 6.1. Dehydration of sulfur combustion air in a sulfur burning acid plant. The dried air contains 50 milligrams of H20(g) per Nm3 of gas.

Fig. V.l. Front end of sulfur burning acid plant showing that kg-mole dry Is catalyst bed feed gas = kg-mole dry sulfur combustion air.

Sulfuric acid 1.66 18.3 Frasch process with sulfur combustion... 

Provision of the sulfur dioxide feed gas for a contact plant is usually obtained by sulfur combustion, but there are many other potential sources. Pyrite, FeS2, is burned (Eq. 9.27) and other sulfidic minerals are roasted (Eqs. 9.28 and 9.29), the latter primarily for their metal values rather than for the sulfur dioxide. 

Some external fuel, usually oil or gas, is required initially to raise the roaster temperature to the desired range for these processes to occur. Less is required later since the sulfur combustion is highly exothermic and provides some of the heat. If the concentrate contains more than 25% sulfur and is dry, sufficient heat is evolved from the sulfur combustion to maintain the roaster... 

Smelter acid is not as pure as the acid produced from sulfur combustion, so it fetches a lower price. Nevertheless, this product is quite suitable for uses such as fertilizer phosphate production, which gives a by-product credit to the process. Smelters which exercise this choice produce about 4 tonnes of sulfuric acid for each tonne of copper [36]. Smelter sources contributed about 6% of the sulfuric acid produced in the U.S.A. in 1965 and more than 60% of the Canadian total for 1976 [39]. 

Supplementary Engineering Equipment for Process Rearrangement. To be able to utilize the lean gas stream, which is saturated with water vapor, in the sulfuric acid plant, a new wet-dry catalytic process for sulfur combustion was developed jointly by... 

The combustion of sulfur, which is obtained either from natural deposits or from desulfurization of natural gas or crude oil, is carried out in one-stage or two-stage sulfur combustion units at 900-1,050 °C. The combustion unit consists of a combustion chamber followed by a process gas cooler. The SO2 content of the combustion gases is generally up to 11 vol.% aud the O2 conteut is low (but higher than 10%). 

Combustion of hydrogen sulfide (H2S) or similar gases is achieved in a fixed furnace at about 1,000 °C. Combustion heat is higher than with sulfur combustion. Two different ways are used to process the gases to SO3 and H2SO4 ... 

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