Condensation of sulfur

During preparation of zinc ethylsulfinate, addition of diethylzinc to liquid sulfur dioxide at — 15°C leads to an explosively violent reaction. Condensation of sulfur dioxide into cold diethylzinc leads to a controllable reaction on warming. 

The exhaust gas must have a temperature of > 300 °C at the exit of the kiln to prevent condensation of sulfuric acid in the ducting. Energy can be saved by recirculating some of the gas to the combustion chamber of the kiln and mixing it with the fuel gases as a partial replacement for air. Alternatively, it can be used for concentrating the dilute acid (see Section 2.1.3.5). The gas then goes to the waste-gas purification system. 

All air preheaters are subject to corrosive attack caused by condensation of sulfur trioxide. At a 150-ppm sulfur in the fuel gas, operating... 

During their residence time in the atmosphere, mineral dusts become coated by sulfates, nitrates, and other species (Dentener et al. 1996 Buseck and P6 sfai 1999 Zhang and Carmichael 1999 Song and Carmichael 1999 Buseck et al. 2000). These coatings are formed through chemical reactions such as the oxidation of SO2 and NO2 at the gas-solid interface, as well as by condensation of sulfuric and nitric acids. Once coated, the hygroscopic dusts act as cloud condensation nuclei and further oxidation reactions can take place in the aqueous medium (Wurzler et al. 2000). Subsequent evaporation of the cloud droplet yields a coated particle. 

The last anion to be discussed is nitrate. In the marine aerosol, nitrate is associated mainly with coarse particles. This fact is apparent in Fig. 7-21, but it has also been observed by Savoie and Prospero (1982). Sea water contains insignificant amounts of nitrate, so that the particulate nitrate must derive from the gas phase, that is, from gaseous nitric acid. As a gas-to-particle conversion process, one would expect the condensation of nitric acid to take place in the accumulation mode. The volatility of HN03 is much greater than that of H2S04, however. It appears that the condensation of sulfuric acid prevents the simultaneous condensation of nitric acid in the same size range. In this connection one should remember that with... 

FIGURE 10.16 Estimates for the characteristic time required for the condensation of sulfuric acid vapor on preexisting particles (r ) and the characteristic time required for nucleation of H2SO4-H2O aerosols (xs) as a function of relative humidity. Two H2SO4 production rates... 

This decomposition takes place in the high-temperature thermal plasma zone, which is followed by clusterization and condensation of sulfur in the lower-temperature zones usually on the discharge periphery ... 

Only a small amount of sulfur trioxide can have an adverse effect as it brings about the condensation of sulfuric acid and causes severe corrosion. Although diminution of the excess air reduces sulfur trioxide formation considerably, other considerations, such as soot formation, dictate that the excess air level cannot be lowered sufficiently to eliminate sulfur trioxide entirely. 

To control the catalyst bed temperature in high sulfur fuel applications, as shown in Fig. 2.16 a bypass is often installed for the SCR catalyst as well as for the boiler [14]. This keeps the catalyst at high temperatures even during low-load operation or idling and avoids condensation of sulfuric acid in the catalyst during start-up. 

All air preheater heat exchangers are subject to corrosive attack caused by the condensation of sulfur trioxide. Refineries must burn fuel gas with less than 160 ppm of sulfur. Regardless of the calculated dew point of the sulfur trioxide, operating experience has shown that a minimum temperature of 300 F-350°F in the outlet flue gas is required to minimize corrosion and fouling of the heat exchanger. Uneven cooling of the flue gas results in the need to keep the flue gas 50°F-100°F hotter than its calculated dew point. 

All air preheaters are subject to corrosive attack caused by condensation of sulfur trioxide. At a 150-ppm sulfur in the fuel gas, operating experience shows that a minimum temperature of 350 to 400°F minimizes corrosive attack. Uneven coohng in the preheater results in the need to keep the flue-gas outlet temperature 50 to 100°F above the calculated SO dew point. The flue-gas outlet temperature can be... 

Another Claus plant operating problem is condensation of sulfur on the catalyst resulting in rapid deactivation. This can be avoided by maintaining the temperature in the catalytic converters above the sulfur dew point of the gas mixture. Should sulfur condense on the catalyst, raising the gas temperature 50°F is usually sufficient to vaporize the condensed sulfur and reestablish catalyst activity (Norman, 1976). 

Introduction, This process, which was developed by AMOCO Canada Petroleum Company. Ltd. in the early 1970s, has been described by Goddin et al. (1974). Nobles et al. (1977), Rccd (1983), and Lim et al. (1986). The Cold Bed Adsorption (CBA) process is a sub-dewpoint" sulfur recovery process and is quite similar in principle to the Sulfreen process, as the Claus reaction is al.so carried out at sufficiently low temperatures to cause condensation of sulfur on the catalyst. However, unlike the Sulfreen proce.ss, where a closed loop of inert gas is used to desorb the adsorbed sulfur, a hot gas slipstream from the Claus unit is used for this purpose. 

Condensation of sulfuric acid from SO3, H20(g), H2S04(g), O2, N2, CO2 gas requires prior injection of solid nanoparticles into the gas. Without these particles ... 

A typical modem Claus sulphur recovery plant uses several reactors to achieve the equilibrium conversion of hydrogen sulfide. The complex gas nux-ture from the furnace is cooled to condense sulfur and then reheated before it enters the first catalyst reactor. There are generally three catalytic reactors in series contaitung a catalyst in series, with coolers at each reactor outlet to condense sulfur as it forms. Typical operating conditions are shown in Table 2.9. Inlet and outlet temperatures in each reactor are controlled at levels high enough to prevent condensation of sulfur on the catalyst. 

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