Sulfur filtering

Gas chromatograph for fused-silica capillary or packed columns, equipped with a flame photometric detector (with sulfur filter), Hewlett-Packard, Carlo Erba, or equivalent... 

To a flask are added 200 gm (2.6 moles) of ammonium thiocyanate, 59 gm (1.0 mole) of 85% hydrazine hydrate, and 25 ml of water. The solution is refluxed for 3 hr under nitrogen, cooled, the sulfur filtered, and the filtrate allowed to cool for 10-18 hr. The product crystallizes slowly on standing and is filtered. The crude product, on recrystallization from a 1 1 water-ethanol mixture, gives 46 gm of thiosemicarbazide, m.p. 180°-182°C. Evaporation of the mother liquor to half its volume and then cooling give an additional 5 gm of product. The total yield is 57%. 

Carbon disulfide in air may be analyzed by NIOSH (1984) Method 1600. Between 3 and 25 L of air at a flow rate of 10-200 ml./min is adsorbed over coconut shell charcoal, desorbed with benzene, and injected into a GC equipped with a flame photometric detector with a sulfur filter. The chromatography column consists of 5% OV-17 on an 80/100 mesh Gas Chrom Q support. 

A sulfur filter along with a standby filter can also be provided to ensure that only filtered sulfur is fed to the plant. This has the following advantages ... 

Use of efficient hot gas filters and sulfur filters to minimize the deposition of ash on the catalyst surfaces. 

Most sulfuric acid plants the world over have the problem of disposal of settled sulfur sludge. Modem plants have a sulfur filter and the filter cake containing 50-70% sulfur is a sludge disposal problem. This can be converted to SO2 and subsequently converted to 98% sulfuric acid by the process described with minor modifications. NEAT has applied for an international patent for the same. 

S02 conversion systems. Hot gas filter (optional—since sulfur filters will be used) and catalytic converters with internal supports for catalyst of the conventional (potassium promoted) and cesium promoted types. 

Steam is also consumed in the plant for keeping the sulfur in the settling and pumping sections in a molten state, for heating the sulfur filter jacket, and for keeping the sulfur pumps and feed lines hot. 

A sulfur filter and two centrifugal pumps are provided for filtering the raw sulfur. Metering pumps are provided to ensure a steady sulfur feed to the burner. This will help in maintaining steady process conditions, very essential for efficient plant operations. 

Two tests [2] are used to determine the porosity of gold contacts used in outdoor equipment (1) a nitric acid vapor test (exposure of gold-plated specimens in a desiccator containing 300 mL nitric acid for 1 h at 24 3°C and a maximum relative humidity of 60 %) tmd (2) an alkaline polysulfide test (the specimen is immersed for 60 s in a solution made of sodium sulfide, water, and excess flower of sulfur, filtered and diluted to a specific gravity of 1.142, and made alkaline with sodium hydroxide). 

The algorithm isotopic pattern filter is based on the accurate m/z of ions, where the m/z differences of selected isotopic ion-pairs (e.g. M-t 1 M and M+2 M, where M is the monoisotopic peak and M -h 1 and M+2 are the first and the second isotopic peak) must fall into the pre-assigned accurate mass tolerance window (e.g. 5 ppm), so satisfying the predefined relative abundance criteria. These filters are based on the isotopic pattern deviation between the empirically measured spectrum and the theoretical spectrum. The application of carbon, chlorine, bromine or sulfur filters also allows reduction of the number of proposed elemental compositions that would fit for a certain mass-accuracy window, as their presence in the molecule produces a characteristic isotopic distribution. The additional information obtained from the isotopic signature reduces dramatically the number of proposed calculated empirical formulae to a number typically below 5. The reduced number of elemental compositions can be searched in databases using elemental composition as the search criterion (e.g. Merck Index, Chemindex, catalogues of standards manufacturer, and Google). 

The main justification for diesel fuel desulfurization is related to particulate emissions which are subject to very strict rules. Part of the sulfur is transformed first into SO3, then into hydrated sulfuric acid on the filter designed to collect the particulates. Figure 5.21 gives an estimate of the variation of the particulate weights as a function of sulfur content of diesel fuel for heavy vehicles. The effect is greater when the test cycle contains more high temperature operating phases which favor the transformation of SO2 to SO3. This is particularly noticeable in the standard cycle used in Europe (ECE R49). 

The precipitated cellulose acetate is filtered from the dilute (25—36%) acetic acid. The acetic acid and salts remaining from the sulfuric acid neutrali2ation are removed by washing. The wet polymer is typically dried to a moisture content of 1—5%. The dilute acetic acid obtained from the washing and precipitation steps caimot be used in other stages of the process. Its efficient recovery and recycle are an economic necessity. 

Pollutants. The problems posed by ak pollutants are very serious. Within a museum, measures can be taken to remove harmful substances as efficiently as possible by means of the installation of appropriate filter systems in the ventilation equipment. Proposed specification values for museum climate-control systems requke filtering systems having an efficiency for particulate removal in the dioctyl phthalate test of 60—80%. Systems must be able to limit both sulfur dioxide and nitrogen dioxide concentrations <10 /ig/m, and ozone to <2 /ig/m. ... 

Od condensed from the released volatdes from the second stage is filtered and catalyticady hydrotreated at high pressure to produce a synthetic cmde od. Medium heat-content gas produced after the removal of H2S and CO2 is suitable as clean fuel. The pyrolysis gas produced, however, is insufficient to provide the fuel requirement for the total plant. Residual char, 50—60% of the feed coal, has a heating value and sulfur content about the same as feed coal, and its utilisation may thus largely dictate process utdity. 

Phenolphthalein. Alophen, Ex-Lax, Feen-a-Miat, Modane, and Phenolax are trade names for phenolphthaleia [77-09-8] (3,3-bis(4-hydroxyphen5l)-l-(3ff)-l isobensofuranone) (10). It is a white or faintiy yellowish white crystalline powder, odorless and stable ia air, and practically iasoluble ia water one gram is soluble ia 15 mL alcohol and 100 mL diethyl ether. Phenolphthaleia may be prepared by mixing phenol, phthaHc anhydride, and sulfuric acid, and heating at 120°C for 10—12 h. The product is extracted with boiling water, then the residue dissolved ia dilute sodium hydroxide solution, filtered, and precipitated with acid. 

In this process, any sulfur present in the coal exits the gasifier as hydrogen sulfide which is removed by various processes such as a Hohnes-Stretford unit where the sulfide is absorbed and regenerated. The resulting sulfur is filtered out as a cake (39 wt %) which is sold as a valuable feedstock (see Coal CONVERSION PROCESSES, GASIFICATION SULFURREMOVAL AND RECOVERY). 

The products of reaction are pumped to a filter press for separation into a sodium sulfate solution and a filter cake having a low moisture content. The filter cake is then ready to be processed for the recovery of lead. The filtrate from the process contains an excess of sodium carbonate, and can be neutralized using the sulfuric acid drained from the batteries. 

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