Sulfur retention time

Relatively high (typically 980—1200°C) temperatures are required to decompose spent acids at reasonable burner retention times. Temperatures depend on the type of spent acid. A wide variety of spent acids can be processed in this way, but costs escalate rapidly when the sulfuric acid concentration in spent acid (impurity-free basis) falls below about 75%. A few relatively uncontaminated spent acids can be reused without decomposition by evaporating the excess water in concentrators, or by mixing in fresh sulfuric acid of high concentration. Weak spent acids are frequently concentrated by evaporation prior to decomposition. 

In AFBC units, heat is removed from the flue gas by a convection-pass tube bank. The particulates leaving the boiler with the flue gas consist of unreacted and spent sorbent, unburned carbon, and ash. Multiclones after the convection pass remove much of the particulate matter and recvcle it to the combustor, increasing the in-furnace residence time an improving combustion efficiency and sulfur retention performance. Bubbling PFBC units do not have convection-pass tube banks and do not recycle solids to the boiler. 

In a continuous process, ground PET bottles (830 parts) in an aqueous slurry were pumped into an autoclave equipped with a stirrer and maintained at 450-550 psig pressure and 191-232°C. Ammonium hydroxide (300 parts) solution consisting of water (7857 parts), ethylene glycol (493 parts), and ammonium sulfate (918 parts) was introduced into the reactor. The retention time in the reactor varied from 5 to 45 min. The aqueous diammonium terephthalate and edtylene glycol solution was withdrawn from the reactor and filtered while hot to remove solid impurities such as pigments, pieces of metal caps, labels, and cap liners. Hie filtrate was acidified widi sulfuric acid solution to liberate the TPA product. Hie recovered TPA usually had a purity of 99% or higher. 

Hexavalent chromium reduction through the use of sulfur dioxide and sodium metabisulfite has found the widest application in the metal finishing industry. It is not truly a treatment step, but a conversion process in which the hexavalent chromium is converted to trivalent chromium. The hexavalent chromium is reduced through the addition of the reductant at a pH in the range of 2.5-3 with a retention time of approximately 30-40 min (Figure 9.7). 

Alkylation of toluene and acetylene in the presence of sulfuric acid is accomplished in the four-stage reactor of the sketch. Retention time in each stage is 10 min, temperature is 41 F and pressure is 50 psig. On the assumption that the liquid always is saturated with acetylene, the reaction is first order with respect to toluene. At the conditions shown, the reaction is estimated 95% complete. Find the specific reaction rate. 

Strength. The only other possibility was to change the polarity of the bonded phase therefore, a CN column with equivalent polarity as silica itself was chosen and tailing eliminated as demonstrated by the peak shapes in Figure 4. Using the CN column and an eluent of 25 75 acetonitrilerwater with 0.035% sulfuric acid (v v v), good peak shapes were obtained with no change in retention time with variation in sample concentration. 

Orthophthalaldehyde (OPA) in combination with a thiol is the reagent of choice for derivatization, despite its inability to react with proline, hydroxyproline, and the sulfur-containing amino acids. Another drawback of the reagent is the instability of the reaction products, making an automated derivatization system coupled to an automated injector, and constant retention times an absolute necessity. Taking into account these considerations, the HPLC analysis will be of use to every biochemical genetics laboratory for biological fluids other than urine. The system has also a... 

The progress of hydrolysis of the various silanes in an ethanol solution was determined by following the drop in the ethoxysilane and the rise of siloxane dimer with GC. Sulfuric acid was used to catalyze this series. During the reaction, the only silane species present in observable quantities were the ethoxysilane and the dimer. No measurable amounts of silanol were observed (the silanols were prepared and their retention times are known). This fits with the idea of the hydrolysis being the rate determining step. 

The upper laminite sample from NR-10 (151.5 m), besides the 2-tetradecylthiophene, contains an isomer with an identical mass spectrum which according to the slightly shorter retention time may have a methyl-branched carbon skeleton (Figure 4a). Small amounts of a thienylhopane are present in all samples studied, but sulfur-bearing steroids could not be detected despite the abundance of sterenes in the saturated hydrocarbon fractions. 

The Microbial Mat. The "intermediate fraction of the extracts and pyrolysates of the kerogens of a modem and buried mat were analysed by GC with coupled FID and FPD and GC-MS. In the extract of the modem mat, two isomers of a C20 thiophenic isoprenoid (compounds I and II) already reported in the literature (11-12) are the most abundant organic sulfur compounds (Figure 5B). The "intermediate" fraction of the pyrolysate of the corresponding sample, is also dominated by the same two isomers of thiophenic isoprenoids that exhibit a similar internal ratio as in the extract. The presence of a third isomer was detected in smaller quantity (compound III)(13). Other thiophenic compounds are present in the sample and were tentatively identified using mass spectra data, GC retention time, and literature (14-16). They are similar to the compounds found in the "intermediate" fraction of the pyrolysate of the buried mat (Figure 5D). 

Figure 2 shows the results of the pyrolysis experiments conducted with the Spanish lignite at 750-960°C at residence times of 0.52-0.72 sec. It is seen that under the pyrolysis conditions used, 60 - 70% of the sulfur in this coal appears in the gaseous products as H2S, COS, and CS2. As in the previous sulfur study (1), the principal sulfur gaseous product at all temperatures is H2S, with some CS2 formed at T >840°C. The CS2 is apparently formed at the expense of the H2S, by any of several reactions H2S may react with the carbon of the coal and/or the methane evolved in the pyrolysis of the coal to form CS2- A small amount of COS is detected at all temperatures trace amounts of SO2 are also detected. Moreover, the total sulfur yield appears to reach a maximum about 900°C. The decrease in sulfur volatilization as pyrolysis temperature is increased above 900°C is attributed to sulfur retention in the char due to the reaction of H2S with coke or char to form more stable thiophenic structures (2). GC/MS analysis of the tars (diluted to 10 ml) from the pyrolysis at 750 and 850°C did not reveal any sulfur-containing structures. Tars from the pyrolysis at 900 and 950°C, however, contain dibenzothiophene. 

Without retention time data for authentic standards, all that GLC-FID/FPD analysis can tell us is the number and distribution of the sulfur compounds in the various samples. It cannot tell us what the individual sulfur compounds are. To obtained this information we turn to GC-MS analysis. 

The performance of the system is tested by injecting 2 xl of OPCW check mixture running the Performance Check Injection method. The composition of the mixture is given in Annex 2. The retention times of the series of nine hydrocarbons in the check mixture are used by AMDIS for calibration of the RI the other seven compounds are used for assessing the performance of the GC and MS part of the system. Two components of the check mixture, chloromethylaniline and dibenzothiophene, are used for evaluation of isotopic ratios for chlorine and sulfur measured by the mass spectrometer. The example chromatogram of the check mixture is presented in Figure 5. 

As further proof of the model study a laminate containing DAA was heated in the presence of an odorless cooked ham or in the presence of cystein, a sulfur-containing amino acid, to produce the off-odor. The identity of this off-odor was then characterized by GC separation with subsequent sniffing detection and comparison with the retention time of compound I. 

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