Viscosity sulfur burning

Sulfur burners are fed with 410 K molten sulfur, near the viscosity minimum but safely below the steep viscosity increase. Sulfur temperature is maintained by circulating 420 K steam through sulfur storage tank steam pipes just ahead of sulfur burning. Below ground or insulated above ground storage tanks are used. 

Elemental sulfur melts at 120 °C. It is easily melted with pressurized steam pipes and pumped molten around the sulfur burning plant. The molten sulfur temperamre is maintained around 140 °C to avoid a huge viscosity increase near 160 °C. 

The products manufactured are predominantiy paraffinic, free from sulfur, nitrogen, and other impurities, and have excellent combustion properties. The very high cetane number and smoke point indicate clean-burning hydrocarbon Hquids having reduced harmful exhaust emissions. SMDS has also been proposed to produce chemical intermediates, paraffinic solvents, and extra high viscosity index (XHVI) lubeoils (see Lubrication and lubricants) (44). 

Sulfur Trioxide Generation. For sulfur trioxide generation, high-purity sulfur (99.5% pure) is melted in a tank and then kept at 145-150°C to maintain its viscosity at the minimum and constant value. The molten sulfur is introduced into the sulfur burner by a special metering pump and then burned to SO2, using the dried air. The diluted SO2 gas (6-7%) leaves the burner at around 650°C and is cooled to 430°C before feeding to the converter. 

In screening chemical modifiers for sulfur one looks for more than transitory improvements in the physical properties (particularly tensile and impact strength), the burning characteristics, the color, and the odor. Changes in viscosity, surface tension, and supercooling tendencies are considered secondary areas. 

The viscosity of liquid sulfur increases rapidly with temperature. It is better to maintain the temperature of liquid sulfur between 125 and 130 °C for ease in pumping. The liquid can be easily sprayed through the nozzles of the spray guns installed in the burners for proper burning. At temperatures above 145-150 °C it becomes difficult to pump and spray. Hence, the steam pressure in the jackets of liquid sulfur lines, valves, pumps, etc., should be controlled at 3.5-4.0 kg/cm by means of a pressure regulator. A safety valve should be provided on the steam supply line and set to blow off (release steam) at 4.8-5.0 kg/cm. ... 

In SOs-sulfation, the gas may be delivered by an outside manufacturer in tank cars, is produced in-house by stripping from oleum, or is generated close to the sulfation unit by burning sulfur and oxidizing of the SO2 to SO3 by air with vanadium oxide as catalyst. The latter is the preferred method in modem plants. The SO3 is diluted with dry air to reduce reactivity. Falling film and cascade reactors are used to carry out s. Temperature control and adequate feed transport that respect the changes in viscosity during the process are the key criteria for these processes and for product quality (color). 

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