SO2 cooler

Fig. 1. Flow diagram of production of sulfur dioxide from oleum 1, 30% oleum exchanger 2, SO vaporizer 3, reactor 4, coolant surge tank 5, coolant ckculatkig pump 6, coolant exchangers 7, sludge and acid pump 8, scmbber 9, SO2 cooler 10, gas cleaner 11, SO2 compressor 12, pulsation damper and 13, SO2 condenser. CM is the condensate FRC, flow recording controller PIC, pressure kidicatkig controller SM, steam TC, temperature recorder ...

Correct operation of the burner is essential for successful functioning of the total sulphonation plant. Unbumt sulphur may evaporate and will pass upstream with the process gas causing sulphur sublimation deposits in filters and catalyst tower ("yellow fever"). Subsequent local burning of sulphur can cause severe damage to equipment such as the SO2 cooler, the SO3 filter. 

The converter tower catalyst has to be preheated before plant start-up. A gas or oil-fired preheater (Ballestra) supplies the hot combustion gas which heats the dried process air, using the SO2 cooler as a preheater. A temperature of 4(X)°C in the catalyst tower is attained after about 3 hours. 

After the SO converter has stabilized, the 6—7% SO gas stream can be further diluted with dry air, I, to provide the SO reaction gas at a prescribed concentration, ca 4 vol % for LAB sulfonation and ca 2.5% for alcohol ethoxylate sulfation. The molten sulfur is accurately measured and controlled by mass flow meters. The organic feedstock is also accurately controlled by mass flow meters and a variable speed-driven gear pump. The high velocity SO reaction gas and organic feedstock are introduced into the top of the sulfonation reactor,, in cocurrent downward flow where the reaction product and gas are separated in a cyclone separator, K, then pumped to a cooler, L, and circulated back into a quench cooling reservoir at the base of the reactor, unique to Chemithon concentric reactor systems. The gas stream from the cyclone separator, M, is sent to an electrostatic precipitator (ESP), N, which removes entrained acidic organics, and then sent to the packed tower, H, where SO2 and any SO traces are adsorbed in a dilute NaOH solution and finally vented, O. Even a 99% conversion of SO2 to SO contributes ca 500 ppm SO2 to the effluent gas. 

H2O, I2 and SO2 are fed into a main reaction vessel (R-l), and continuously recirculated, by means of a pump P-1, in a loop where temperature control can be obtained through the cooler (or heater) C-l. Some of the products are intermittently fed to the liquid-liquid separator R-2 where the two acid phases are separated. The upper H2SO4 phase is purified by boiling in R-3, and then decomposed in a quartz cracker containing Fe2C>3 catalyst. 

Operation of the CLCD started by introducing 3 Kg of iodine and 1 Kg of water at room temperature in the main reaction vessel R-l. SO2 was then bubbled through at a rate of 3 liters/minute until there was evidence of formation of two separate liquid phases (20 minutes). The prime reaction products were kept circulating through the filter F-l and the cooler C-l by means of the pump P-1. Since the temperature had risen to only 45°C, no cooling was necessary. Intermittently, the liquid was fed to the phase separator R-2, allowed to rest 5-10 minutes to complete the separation and then the upper phase sent to the H2SO4 purification boiler R-3 and the lower phase to the degasser R-6. 

During operation of the loop, small quantities of sulfur were observed in the recycled liquids from the HI cracking coolers and small amounts of H2S were collected in the H2 purification traps. This was due to incomplete separation of the sulfur containing species (SO2 and H2SO4) from the lower phase prior to decomposition. The lower phase concentration and purification step (H3PO4 treatment), which is an integral part of the cycle, will eliminate this problem. This step will be tested in the Bench Scale Unit. 

The S02-ladened off-gas from the cooler and the air from the stripper are compressed and sent to a single-contact, single-absorption sulfuric acid plant. Ninety-six percent of the SO2 is converted to 98 sulfuric acid. Ten percent of this byproduct acid is recycled and used in the MgO FGD process but most is stored onsite and eventually sold as a byproduct. The tail gas from the acid plant containing the unconverted SO2 is recycled to the flue gas ducts ahead of the FGD system. 

Selective catalytic reduction (SCR) is typical performing in much cooler flue gas zones where the oxidation potential of nifrogen species is minimized. The cafalysf provides, on ifs surface, sites that permit the ammonia and NOx to react near perfect utilization. The extent of NO reduction is often limited by the local ammonia to NO ratio, the flue gas femperafure, fhe size of cafalysf, and the accepted unreacted ammonia slip. The catalyst size is limited by the available space, the resulting gas side pressure drop, the oxidation from SO2 to SO3, and so on. 

The S9 specifications on flue gas are probably easier to satisfy with an emulsion fuel than with coal, and do not depend significantly upon the surfactant formulation and emulsion manufacturing. The cooler flame results in less CO and NOjj in the flue gas, while the SO2 is removed as in coal-fired plants. In most cases, emulsified fuels create much less ash than eoal does. 

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%). 

Cooler 7 H2S scrubber 8 Gas purification 9 Benzole cold scrubber 10 Benzole column 11 Underground condensate tank 12 Tar separator 13 Phenol extraction 14 Benzole regeneration 15 NH3 separator 16 Ammonium sulfate slurry container 17 Filter 18 H2S separator 19 H2S combustion 20 SO2 oxidation 21 Absorption column 22 Dilution vessel... 

The BATF limit for sorbic acid in table wines is 300 mg/L, whereas OIV places a limit of 200 mg/L. In the case of wine coolers, the level is much higher, 1000 mg/L, or when used with benzoic acid, their combined concentrations are 1000 mg/L. In table wines, depending on alcohol, pH, SO2, and yeast titer, 100-200 mg/L are typically used. 

The use of sodium or potassium benzoate is approved by BATF for stabilization of wine coolers but not table wines. Although permitted for use at levels up to 1000 mg/L, sensory considerations require use at much lower levels. In wine coolers, benzoate is frequently used in combination with sorbate and SO2. The combination provides the needed level of antimicrobial activity at concentration levels that are generally not sensorially objectionable (Zoecklein et al., 1995). Carbonation may also enhance antimicrobial effects. In soft drinks, Schmidt (1987) reported linear decreases in the concentration of sodium benzoate required with increases in carbonation. 

A new heatup path is then calculated as described in Section 11.11. The result is a path nearly parallel to the 690 K path 30 K cooler at all % SO2 oxidized values, Fig. 11.6. 

Molten sulphur (150 C) from storage is pumped to the sulphur furnace where sulphur is converted with an excess of oxygen from the process air to SO2 (4-7% SO2 by volume in "air"). The fiimace outlet temperature of the S02/air varies with the percentage of SO2 in air between 600 and 700 C, indicating the strong exothermic character of the reaction. The S02/air flow is cooled in an indirect air cooler from 6(X)-700 C to about 420 C. 

SO2 is converted to SO3 in the so-called converter tower filled with 4 packed beds of V2O5 catalyst on a silica carrier. The reaction is highly exothermic and intermediate cooling of the process gas flow between the various beds with indirect air coolers is required. 

Due to the excess of caustic soda in the solution leaving the SO2 scrubber (pH 9-12), this liquid can also be used to neutralise liquid acid effluents that cannot be disposed of in an SO3 absorber and oleum/sulphuric acid ex the SO3 cooler system. To avoid SO2 formation due to decomposition of sodium sulphite (Na2S03), the pH should never be lower than 8. 

Apart from this, components such as SO2, NO2, NHj, CI2 and HCl occur as traces in air. However, they are almost completely retained by the spray cooler and molecular sieve adsorbers. Partly, SFg, CF4 and C2Fg break through as non-flammable compounds which are recovered in highly enriched sumps of Kr/Xe-plants. The component oil given in Table 2.10, is mainly generated by oil-lubricated compressors that are only used in very small plants nowadays. This imdesired oil-content can be reduced by means of suitable downstream hlters (e.g. activated carbon filters). An oil-load of the compressed air of0.005 mg of oil per standard cubic meter of air should not be exceeded at the inlet of the molecular sieve adsorbers. 

---