Sulphur burning

At high temperatures oxygen reacts with the nitrogen in the air forming small amounts of nitrogen oxide (p. 210). Sulphur burns with a blue flame when heated in air to form sulphur dioxide SO2, and a little sulphur trioxide SO3. Selenium and tellurium also burn with a blue flame when heated in air, but form only their dioxides, Se02 and Te02. 

Sulphur dioxide is formed together with a little of the trioxide when sulphur burns in air ... 

Figure 1. Simplified flow sheet for a sulphur-burning double-absorption sulphuric acid plant (3+1 layout).

As produced from the hydrometallurgical process the sulphur will always be contaminated with siliceous gangue and pyrite. In some cases, it will be upgraded for use in sulphur burning acid plants, but there will be a strong incentive to use the material in its impure state for sulphur extended asphalt highway construction and sulphur concrete applications. 

Solid sulphur, selenium, and tellurium inflame in fluorine gas at ordinary temp. sulphur burns to the hexafluoride, SF6. The reactivity of sulphur or selenium with fluorine persists at —187°, but tellurium is without action at this temp. Hydrogen sulphide and sulphur dioxide also burn in the gas—the former produces hydrogen fluoride and sulphur fluoride. Each bubble of sulphur dioxide led into a jar of fluorine produces an explosion and thionyl fluoride, S0F2, is formed but if the fluorine be led into the sulphur dioxide, there is no action until the sulphur dioxide has reached a certain partial pressure when all explodes. If the fluorine be led into an atm. of sulphur dioxide at the temp, of the reaction, sulphuryl fluoride, S02F2, is formed quietly without violence. Sulphuric acid is scarcely affected by fluorine. 

Sulphuric acid (98%) 400 000 tonnes Sulphur-burning process, followed by catalytic oxidation of S0-> (vanadium pentoxide catalyst). 

Sulphur burning 3. Glowing wood 4 13-5 oxygen. 16 oxygen. 

Directions (a) Touch a bit of sulphur with a hot platinum wire and bring the sulphur thereby into the flame. (1) Describe the odor of the substance formed. (2) Write the equation for the reaction which takes place when sulphur burns in the air. 

The bright appearance of galena would attract early man, for it often lay on or very close to the surface of the soil. Having already learned how to reduce copper ores in his primitive furnace, he would experience no difficulty in reducing galena. It was sufficient merely to roast it in air, whereby the sulphur burned off and the molten metal sank into the hearth. 

One source of trouble and a cause of spoilage of much fruit is contamination from sour and moldy boxes. When a box is used several times it becomes permanently infected and a cause of infection by spoilage organisms. This can be controlled without much difficulty by having a tight room in which the worst boxes are placed after they are emptied, with steam turned on to saturate the atmosphere and sulphur burned or sulphurous acid gas liberated to act as a disinfectant. This does not require a large place, much time, or expense. ... 

This is the gas produced when sulphur burns in the air in oxygen gas. It is best obtained pure by heating oil of vitriol with mercury or copper. Either of these metals deprives a part of the sulphuric acid of oxygen, and the oxide thus formed combines with the rest of the acid. Thus—... 

SOs vapours for subsequent production of 65 % oleum or liquid SO3 with some more equipments. Expansion of production capacity can be planned in the beginning by installing sufficiently big sulphur burning furnace, waste heat recovery boiler, converter, air blower, etc. These can be used as such in future. 

Figure 7.8 Sulphur-burning double absorption sulphuric acid process...

A variety of sulphonation reagents can be used for the sulphonation reaction SOa/air from sulphur burning and subsequent conversion of the S02/air formed SOs/air from stabilised liquid SO3 or SO3 stripped from 65% oleum with dried process air, 20% oleum and chlorosulphonic acid. 

If SOs/air with 10 volume % SO3 is raised, the SO3 partial pressure would be 0.1 X 760 = 76 mm Hg. The driving force for absorption will become very small when the concentration of 40% oleum is approached. 65% oleum cannot be made by absorption of SO3 from S03/air mixtures obtained from sulphur burning, because the required partial pressure of SO3 in air has to be higher than 214.9 mm Hg. The process to manufacture 65% oleum is therefore in practice as follows ... 

After preheating of the plant and initial sulphur burning, the conversion to SO3 will increase gradually with time. It takes about 0.5 hour before the conversion attains the desired level of 98-98.5%. During this period it is not possible to produce good quality organic acid product and therefore the SOj/SOj/air gas flow has to be diverted, without inftinging the limits on SO2/SO3 levels in the exhaust gas that are emitted to the atmosphere. 

An alternative to sulphur burning and subsequent SO2 conversion to SO3 is the use of stabilised liquid SO3. The use of stabilised liquid SO3 is restricted by the proximity of a supplier. This chemical should be transported and handled with great care. A simplified flowsheet is presented in figure 14. The stabilised liquid SO3 is transferred by a membrane metering pump from the day tank through a filter and into the vaporiser. The gaseous SO3 thus obtain is filtered to remove any remaining mist and then mixed with dried process air (dewpoint -60 C) to the required SO3 level. 

Sulphur-burning plants with waste heat boilers frequently have superheater tubes in the converter. In smaller plants, the tubes of one of the boiler sections may also be inside the converter. There is usually but a few inches clearance between the baffle plate under the tubes and the catalyst. When installing catalyst in the layers containing these tubes, it is best to use the manholes on each side of the converter. This will facilitate the final levelling of the catalyst and the covering layer of quartz pebbles. 

It may be necessary at some time to clean the catalyst in the converter because of increased pressure drop due to dust and scale from various sources being carried in the gas stream to the converter. In sulphur-burning plants, impurities in the sulphur will cause catalyst plugging. 

Sulphur flow problems Air flow problems Erratic sulphur burning... 

Sulphur burning plant and SO2 to SO3 conversion plant block diagram Air drying equipment Sulphur burner... 

Writing the second reaction in this manner makes sense if we have (as we actually do) an idea of the reaction equilibrium, possibly also of the reaction kinetics. Indeed, the reaction is reversible at higher temj ratures, it can proceed in opposite direction, and in an industrial sulphur burning unit, one finds only relatively small amount of SO3 in the outlet gas, although the reactivity (tendency to achieve equilibrium) increases with the temperature. On the other hand, from the standpoint of balancing proper the second reaction can be replaced by the scheme... 

To begin with an example, the reader is requested to turn now to Section 4.6, Fig. 4-2. First, the steady-state convention requires excluding from the set of nodes subject to balancing the inventories of sulphur and produced acids they are regarded as parts of the environment node. Now for instance the multicomponent balance of node B (sulphur burning unit)... 

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