Sulfur condenser

The Claus process is the most widely used to convert hydrogen sulfide to sulfur. The process, developed by C. F. Claus in 1883, was significantly modified in the late 1930s by I. G. Farbenindustrie AG, but did not become widely used until the 1950s. Figure 5 illustrates the basic process scheme. A Claus sulfur recovery unit consists of a combustion furnace, waste heat boiler, sulfur condenser, and a series of catalytic stages each of which employs reheat, catalyst bed, and sulfur condenser. Typically, two or three catalytic stages are employed. 

A sulfur condenser follows the reactor. These processes, ie, Superclaus or Parson s Hi-Activity process, can boost the overall sulfur recovery to up to 99.2%. 

The main processing steps in the Claus process are thermal conversion, sulfur condensation, reheat, and catalytic conversion. In the thermal conversion step, one-third of the feed H2S is oxidized by air ... 

Installation of sulfur de-entrainment devices in the Claus Plant sulfur condensers to allow them to be recycled in the Stretford process ... 

The pyrite sulfur is generally considered to be sulfur associated with iron pyrite, FeS2 In most cases only the second sulfur of the pyrite molecule can be considered to be in this class. This sulfur can be expelled from iron pyrite with moderate heating (approximately 500°C) to form iron sulfide, FeS, and elemental sulfur condensate in the cooler vapor space above the sample. 

A major component of the 3% sulfur loss in earlier multistage Claus plants was entrained sulfur mist in the process gas stream. Precise control of interstage sulfur condenser tempera-... 

Reverse-flow operation for Sulfur Production over Bauxite Catalysts by the Claus Reaction has been considered in Refs 9 and 31. The rate of H2S oxidation by SO2 on bauxite catalysts is very high even at ambient gas inlet temperature, but sulfur condensing at low temperatures blocks the active catalyst surface, and the reaction stops because of catalyst deactivation. In a reverse-flow reactor the periodic evaporation of condensed sulfur from the outlet parts of the catalyst bed occurs. Although it is difficult to remove all the sulfur condensed within the catalyst pellets at the bed edges, after a certain time a balance between the amount of sulfur condensed and evaporated is attained. Using a reverse-flow reactor instead of the two-bed stationary Claus process provides an equal or better degree of... 

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. 

Temperature and Pressure Specification. Since equilibrium conversion of sulfur dioxide to sulfur vapor increases with decreasing temperature, the reduction process was designed so that the primary reduction stage operates at the minimum temperature consistent with reaction kinetics which avoids sulfur condensation on the catalyst. Taking these factors into account, the primary catalytic reactor is operated at 350 °C (623°K). 

From the gas phase composition in Table II, it may be calculated that 79.4% sulfur dioxide is converted to sulfur vapor. Cooling this gas in the absence of a catalyst leads to no equilibrium shift other than that associated with sulfur vapor condensation this has been borne out in the Claus process. By cooling a gas stream of the composition cited in Table II to 140°C (413 K), equilibrium sulfur condensation corresponds to 78.4% first-stage recovery of liquid sulfur. 

The sulfur condenser was a 16 X 1 in. i.d.-stainless steel tube and had baffles every inch to facilitate the critical sulfur condensation. With an unheated condenser, sulfur condensed at the condenser exit and into... 

The major process equipment consists of a reactor vessel and a sulfur condenser. In the reactor vessel, sulfur dioxide-rich gases react with crushed coal to yield gaseous elemental sulfur. This sulfur is condensed from the gas stream in the sulfur condenser. The high-purity liquid sulfur effluent of the process is a nonpolluting by-product. 

Sample ports arranged at quarter point locations along the vertical reactor vessel permitted the gas composition to be monitored at different reactor locations, representing different gas residence times. The temperatures at each of these sample ports, as well as at the inlet and the outlet, were continuously monitored. The effluent gas of the reactor vessel passed through the sulfur condenser. The tail gases leaving the sulfur condenser were sampled and analyzed. 

Perfluorofuran is difficult to handle, tending to polymerize, but substitution in 70 occurs readily. Perfluorothiophene (11) undergoes attack ortho to sulfur. Condensed systems have been investigated in more detail ... 

Fig. 5.10. Two stage standard Claus plant, a) Combustion chamber (Jb) waste heat boiler (c) (1/2) reactor (

Fig. 5.13. Sulfreen process combined with Claus unit, (a) Reactor (b) heat exchanger (c) sulfur condenser (d) separator (e) blower... 

Catalysis by alumina is necessary to obtain good equilibrium conversions the thermal Claus reaction is fast only above 500°C (930°F) (Dowling et al., 1990 Chou et al., 1991). There is also a lower temperature limit, which is not caused by low rates but by sulfur condensation in the catalyst pores and consequent deactivation of the catalyst. The lower limit at which satisfactory operation is still possible depends on the pore size and size distribution of the catalyst with alumina-based catalysts having wide pores, the conversion proceeds satisfactorily at ca. 200°C (390°F) (Lagas et al., 1989 Luinstra and d Haiene, 1989). 

Cooling below the solubility limit for normal solubihty (increasing solubility with decreasing temperamre, such as wax deposits, gas hydrates, and sulfur condensation). The precipitation fouling occurs on the cold surface (i.e., by cooling the solution). 

Sulfer dew point temperature control for column overhead to avoid sulfur condensation. 

Elemental sulfur condensed and solidified in the exit line from the reactor and especially in the cold trap just before the gas chromatographic equipment. Certainly part of the hydrogen so produced was oxidized by metal oxides producing water (reverse step of Reaction 4) and probably some if not most of the sulfur formed was oxidized to SO2 as follows ... 

Bulk Recovery-Clous Process. The classic Claus process is the most common method of producing sulfur. Figure 2-8 is a simplified flow diagram of a typical Claus plant for a feed acid gas with greater than 50% H2S. The first thermal oxidation reaction is fast and takes place in a high-temperature (2,300-2,500°F) furnace-type reactor. The second reaction is relatively slow and requires several stages of catalytic reactors (400-500°F). The gas is cooled to condense and remove sulfur and is then reheated between reactors. The heat liberated by the reactions is used to make medium-pressure steam in the boiler and low-pressure steam in the sulfur condensers. 

It is customary to install mist-eliminadng devices after the last sulfur condenser to minimize entrainment of sulfur droplets into the incinerator. Installation of mist eliminators after each sulfur condenser is also of value, as catalyst deactivation caused by entrained sulfur may be a problem. Wire mesh pads, located in the outlet channel of the condenser, are usually used for sulfur mist elimination. 

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). 

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