Sulfur feed streams

Thermal polymerization is not as effective as catalytic polymerization but has the advantage that it can be used to polymerize saturated materials that caimot be induced to react by catalysts. The process consists of the vapor-phase cracking of, for example, propane and butane, followed by prolonged periods at high temperature (510—595°C) for the reactions to proceed to near completion. Olefins can also be conveniendy polymerized by means of an acid catalyst. Thus, the treated olefin-rich feed stream is contacted with a catalyst, such as sulfuric acid, copper pyrophosphate, or phosphoric acid, at 150—220°C and 1035—8275 kPa (150—1200 psi), depending on feedstock and product requirement. 

In two processes under development as of 1997, the sulfur dioxide stream reacts with reduciag gas over a proprietary catalyst to form elemental sulfur. Both processes have achieved a sulfur recovery of 96% ia a single reactor. Multiple reactor systems are expected to achieve 99+% recovery of the feed sulfur. The direct sulfur recovery process (DSRP), under development at Research Triangle Institute, operates at high temperature and pressure. A similar process being developed at Lawrence Berkeley Laboratory is expected to operate near atmospheric pressure. 

A selective poison is one that binds to the catalyst surface in such a way that it blocks the catalytic sites for one kind of reaction but not those for another. Selective poisons are used to control the selectivity of a catalyst. For example, nickel catalysts supported on alumina are used for selective removal of acetjiene impurities in olefin streams (58). The catalyst is treated with a continuous feed stream containing sulfur to poison it to an exacdy controlled degree that does not affect the activity for conversion of acetylene to ethylene but does poison the activity for ethylene hydrogenation to ethane. Thus the acetylene is removed and the valuable olefin is not converted. 

A. Vannice ( Exxon Research and Engineering Co.) Would a more sulfur-tolerant catalyst be a significant improvement in the overall methanation process If so, what would be the maximum tolerable sulfur concentrations in the feed stream ... 

SuRe [Sulphur recovery] A version of the Claus process in which the capacity of the plant is increased by using air enriched in oxygen in the production of the sulfur dioxide. There are two versions SURE SSB [Side Stream Burner], and SURE DC [Double Combustion], In the first, a small portion of the feed stream containing hydrogen sulfide is burnt sub-stoichiometrically in a second burner in the second, the hydrogen sulfide is oxidized in two stages, with cooling and sulfur separation between them. Both of these... 

The feed stream containing H2S is incinerated with air to oxidize all sulfur compounds to SO2. The heat of combustion is partially recovered by raiding medium-pressure steam (400-600 psig) in a waste heat boiler. The gas is washed and demisted, then dried with concentrated H2S0i. The gas is then compressed, preheated, and enters a fixed-bed catalytic reactor. In the reactor SO2 is converted to S0a ... 

Calcium sulfate crystals were precipitated in a Continuous Mixed Suspension Mixed Product Removal (CMSMPR) crystallizer by mixing of calcium phosphate and sulfuric acid feed streams. The formed calcium sulfate hydrate (anhydrite, hemihydrate and dihydrate) mainly depends on the temperature and the solution composition. The uptake of cadmium and phosphate ions in these hydrates has been studied as a function of residence time and solution composition. In anhydrite, also the incorporation of other metal ions has been investigated. The uptake was found to be a function of both thermodynamics and kinetics. 

SO2 components of the process gas stream. None, however, directly attack the problem of removal of other sulfur values in the gas such as CS2, COS and entrained sulfur mist. These sulfur components can easily exceed 1% of the total sulfur feed and failure to remove them from the process stream can frustrate any attempt to achieve 99%+ recovery even when the Claus reactants, H2S and SO2, have been reduced to low ppm levels. 

The Uthmaniyah plant would produce 326,000 b/d of NGL, 1,140 tons/day of sulfur, and 445 MM of residue gas from a 1,485 billion cfd feed stream. 

Incineration can be applied to all contaminants that have high heat content. It eliminates odor and leachate problems, which are usually associated with landfills, but metals can react with other elements in the feed stream, such as chlorine or sulfur, and form more volatile and toxic compounds. The process has high maintenance and operation costs. Straitz et al. (1995) reported that incineration is a reliable, cost-effective approach to treat VOCs and a wide range of objectionable gas. Chaouki et al. (1995) conducted experiments that examined the effect of fluidized bed combustion on the properties and characteristics of a soil contaminated with PCBs. Particle size distribution and PCB contents were determined before and after a 30-minute incineration. The incineration promoted agglomeration soil, increases in soil pH, and decreases in the PCB content to undetectable levels. 

The process centers on a fixed-bed downflow reactor that allows catalyst replacement without causing any interruption in the operation of the unit (Figure 9-28). Feedstock is introduced to the process via a filter (backwash, automatic) after which hydrogen and recycle gas are added to the feedstock stream which is then heated to reactor temperature by means of feed-effluent heat exchangers whereupon the feed stream passes down through the reactor in trickle flow. Sulfur removal is excellent (Table 9-18), and substantial reductions in the vanadium content and asphaltenes content are also noted. In addition, a marked increase occurs in the API gravity, and the viscosity is reduced considerably. 

The example shown in Fig. 39 illustrates the treatment of an aluminum anodizing bath waste stream by Donnan dialysis. Sulfate ions and protons freely permeate from a feed stream of aluminum sulfate and sulfuric acid across... 

A desulfurization step is necessary in the reforming of natural gas because natural gas is odorized with a sulfur-containing substance - usually methyl mercaptan. This step will prevent damage to (i.e., deactivation of) the nickel or platinum catalysts in downstream processes. Some of these feed streams may also contain chlorides that are not only poisons to the downstream catalysts, but they may also contribute to stress corrosion in the reactors or piping. 

Hydrogen sulfide is recovered from natural gas or refinery gases by absorption in a solvent or by regenerative chemical absorption.1819 In either case a concentrated hydrogen sulfide stream is produced that is treated further by the Claus process. A typical Claus plant has a feed stream of at least 45 percent H2S, but with modifications can handle streams containing as little as 5 percent H2S. For gas streams with low concentrations of hydrogen sulfide, direct conversion of the hydrogen sulfide to sulfur is accomplished in the solvent system, for example, the Stretford process or CrystaSulf process. 

The most significant impurities in the feed streams to a typical alkylation unit are ethylene, dlolefins, sulfur compounds and water. Corrosion Inhibitors and other chemicals used in upstream processing can also be present in some cases, and these can have harmful effects. The amount of each iaqiurlty that reaches the alkylation reactor varies considerably from refinery to refinery. If accurately determined and properly accounted for, these impurities can explain an appreciable percentage of the acid make-up reported by various operating units. The impurity data shown in Table I can be used to evaluate the merit of Improved upstream process control and/or more efficient feed pretreatment methods. 

Diolefins also occur in relatively small concentrations in olefin feed streams. Their concentration increases as cracking severity increases, such as in fluid coking. As in the case of ethylene, the butadienes do not appear to react with isobutane in the presence of strong sulfuric acid. The dienes are believed to form reaction products, most of which are acid soluble, and if this general premise is accepted the fresh acid make-up rate for a dilution range of 98.5 to 90.0% (wt.) can be calculated to be 2465 pounds of acid per barrel of butadiene. Industry practice is to use rates in the range of 1890 to 4200 pounds per barrel. 

In making all operating and design decisions. It Is Important to keep in mind the definition of the true reaction zone. Fundamentally, this Is the Interfaclal area between the immiscible hydrocarbon and acid catalyst liquid phases in the reactor. Reactants and products flow across this boundary. The olefins In the feed stream react Instantaneously with the sulfuric acid catalyst and combine with the relatively small amount of isobutane present In solution In the acid catalyst to form alkylate. Alkylate passes out through the Interfaclal surface reaction boundary into the hydrocarbon phase while Isobutane passes in to resaturate the catalyst. To suppress undesirable polymerization and other reactions It Is necessary to ... 

Figure 9 illustrates the effect of changing limestone average size, r , in the feed stream on the dependence of limestone feed rate, F, and on sulfur absorption efficiency, risAE plots refer to a constant value of 1c3(Tq). 

The main drawbacks of the Ni-YSZ anode are intolerance to the sulfur compounds as low as 2 ppm in H2 steam and a substantial polarization loss at low temperatures (< 600 °C). The majority of the H2 SOFCs require the use of a ZnO-based sorbent to remove H2S in the H2 feed stream. The alternative to Ni anode is the perovskite which possess both electric conductivity and oxidation activity at high temperature. Perovskite such as Sro.5Lao.4Ti04 has shown excellent resistance to sulfur poisoning, however, its overall performance is a factor of 5 less than that of the Ni-cermet. ... 

Olefins can also be conveniently polymerized by means of an acid catalyst. Thus, the treated, olefin-rich feed stream is contacted with a catalyst (sulfuric acid, copper pyrophosphate, phosphoric acid) at 150 to 220°C (300-425°F) and 150-1200 psi (10-81 atmospheres), depending on the feedstock and product requirement. 

Corrosive reaction streams. In some application environments, the reactive or corrosive nature of one or more of the reaction components in a membrane reactor can pose a great technical challenge to the selection as well as the design of the membrane element Feed streams often contain some Impurities that may significantly affect the performance of the membrane. Therefore, attention should also be paid to the response of the selected membrane material to certain impurities in the reactant or product streams. Care should be taken to pretreat the feed streams to remove the key contaminants as far as the membrane is concerned in these cases. For example, palladium alloy membranes can not withstand sulfur- or carbon-containing compounds at a temperature higher than, say, 500 C [Kamcyama et al., 1981]. Even at lOO C, the rate of hydrogen absorption (and, therefore, permeation) in a pure palladium disk is... 

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