Sulfur superheater

A further enhancement to the HRS process whereby the exhaust from a gas fired turbine is used to superheat steam from the HRS process is also possible (129). The superheated steam is then fed through a turbogenerator to produce additional electricity. This increases the efficiency of heat recovery of the turbine exhaust gas. With this arrangement, electric power generation of over 13.6 kW for 1 t/d (15 kW/STPD) is possible. Good general discussions on the sources of heat and the energy balance within a sulfuric acid plant are available (130,131). 

Various reactor designs have been proposed, including fluidized beds (35—37), a whirlpool-type system (38), and a moving refractory bed to superheat the sulfur (39). 

The connection box cooler receives regenerator flue gas after it has been reduced to essentially atmospheric pressure. This arrangement is not limited to the production of saturated steam. Any number of coils can be installed in the box, and normally both steam-generating and superheater coils are present. The tube temperatures within the box must be maintained above the SO dew point of 150—175°C to prevent sulfuric acid corrosion (63). 

Ash fusion characteristics are important in ash deposition in boilers. Ash deposition occurring on the furnace walls is termed slagging, whereas accumulation on the superheater and other tubes is termed fouling. A variety of empirical indexes have been developed (60,61) to relate fouling and slagging to the ash chemical composition through parameters such as acidic and basic oxides content, sodium, calcium and magnesium, and sulfur. 

Sulfites are typically suitable for use in 900 psig boilers. If carryover of BW (containing sulfite) into a superheater occurs, however, then at very high temperatures the sulfite may break down to form acidic sulfur dioxide, which in turn forms sulfurous acid and reduces the pH of the condensate. 

Clearly the oil is a much cleaner fuel than the original coal, from the point of view either of the environmentalist or of the plant engineer concerned with fouling of steam and superheater tubes. The sulfur contents of the oils are 0.1-0.2%, which is acceptable, but the nitrogen contents are about 0.6%, which may cause undesired NOx emissions. Some of the more toxic elements, (mercury, selenium, fluorine, and cadmium) have not yet been determined in oil. It is not clear what will be done with the solid residue whether it will be disposed of as waste or whether its small carbon content, typically 20-50% depending on the... 

Fig. 25.11. Sankey energy flow diagram for a 1000ton/day sulfur-burning double absorption sulfuric acid plant (feed gas 10% S02). A Blower B Sulphur furnace C Waste heat boiler D Catalyst bed 1 E Steam superheater F Catalyst bed 2 G Boiler H Catalyst bed 3 J Intermediate heat exchangers K Intermediate absorber L Converter bed 4 M Economizer N Final absorber O Air dryer P Acid coolers. (Courtsey Lurgi GmbH, Frankfurt, Germany.)...

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. 

Product gas departs the sulfur burning fumace/boiler/superheater into ... 

Sulfur burning offgas is introduced directly into the hot converter because it leaves the sulfur burning fumace/boiler/superheater at its specified feed gas temperature, 700 K. 

Sulfon acid blue R, 218 Sulforation general, 6, 82 vessels, 101, 105 Sulfone reagent, 185, 211, 243 Sulfones, 85 Sulfonic adds rearrangement, 82 separation, 31 l-p-Sulfophenyl-3-methyl-5-pyrazolone, 129 Sulfoxylate, 80 Sulfur black T, 102, 337 Sulfur fusions, 332 Sulfuric add, heat capadty, 70 Sulfuryl chloride, 67, 145 Sun yellow G, 296 Superheater, 142... 

Figure 105. Modern integrated single-train ammonia plant based on steam reforming of natural gas (Clide process) a) Sulfur removal b) Primary reformer c) Steam superheater d) Secondary reformer e) Waste heat boiler f) Convection section g) Forced draft fan h) Induced draft fan i) Stack k) TIT and LT shift converters ...

Sometimes a transition between two crystalling phases occurs vei7 rapidly. That between orthorhombic sulfur and monoclinic i ulfur is rather slow, however, taking minutes or hours, and it is hence easy to superheat orthorhombic sulfur by heating it rapidly. If-this is done, the vapor pressure of the crystals increases as shown by the curve A, and at the point IP, where this curve crosses the vapor pressure curve of the liquid, the crystals melt. The temperature at P, 112.8° C, is... 

The presence of sodium and vanadium complexes in the fuel oil ash can, under certain plant operating conditions, result in considerable harm to the equipment. Spalling and fluxing of refractory linings is associated with the presence of sodium in the fuel. Above a certain threshold temperature, which will vary from fuel to fuel, the oil ash will adhere to boiler superheater tubes and gas turbine blades, thus reducing the thermal efficiency of the plant. At higher temperatures, molten complexes of vanadium, sodium, and sulfur are produced that will corrode all currently available metals used in the construction of these parts of the plant. TTie presence of trace amounts (ASTM D-1318) of vanadium (ASTM D-1548, IP 285, IP 286) in fuel oil used in glass manufacture can affect the indicator of the finished product. 

Depending upon the source of the cmde oil, the refining process, and the fuel grade, varying amounts of sulfur may be present in different types of fuel oils. Combustion of the sulfur containing fuel oils produces sulfur oxides, which pollute the atmosphere and cause corrosion problems in boiler equipment. They may form sodium and vanadium complexes, and such deposits on external surfaces of superheater tubes, economizers, and air heaters cause equipment corrosion and loss of thermal efficiency. 

The sulfur released from the coal forms SO2 with a minor amount of SO3 and reacts with the volatilized alkalis to form Na2S04 vapors, which then condense together with fly ash on the pendant superheater and reheater tubes in the boiler. Most of the ash passes through the unit (Lee et al. 2007). 

Coal is a complex and relatively dirty fuel that contains varying amounts of sulfur and a substantial fraction of noncombustible mineral constituents, commonly called ash (Chawla et al. 2011). Table 3.4 shows the common types of corrosion in coal-fired furnaces. High temperatures (above 1000 F) of the superheater/reheater favor the formation of low-melting compounds. 

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