Granular solid filters

Granular solid filters (see Fig. 16-4) are cleaned by backwashing with water. The backwashing is usually preceded by an air scouring to assure better cleaning.30 The backflow water rate should be fast enough to fluidize the bed. 

The filter application is typically applied to handling streams containing less than 100 to 200 mg/Liter suspended solids, depending on the required effluent level. Increased-suspended solids loading reduces the need for frequent backwashing. The suspended solids concentration of the filtered liquid depends on the particle size distribution, but typically, granular media filters are capable of producing a... 

The o-aminophenylpropiolic acid 4 (20 g) in water (60 mL) and aqueous ammonia (9 mL, d = 0.88) was added with shaking during 15 minutes to a mixture prepared from ferrous sulfate (220 g), water (440 mL), and aqueous ammonia (110 mL, d = 0.88). After 45 minutes, with occasional shaking but no external cooling, the suspension was filtered. The residue was washed with water, and the combined filtrates were treated with ammonium acetate (60 g) and made weakly acidic with acetic acid. The solution was then cooled to 0°C by addition of crushed ice, and then made acidic to Congo-red with concentrated hydrochloric acid (70-80 mL). Additional hydrochloric acid (20 mL, 2 N) was immediately added, and the turbid solution which resulted was diazotized with 20% aqueous sodium nitrite, after which the mixture was kept at 70°C. The cinnoline acid 6 was separated over 45 minutes as a dark brown, granular solid (12.5 g), m.p. 260-265°C. ... 

Granular bed filters are used in ten coil coating plants to remove residual solids from the clarifier effluent, and are considered to be tertiary or advanced wastewater treatment. Chemicals may be added upstream to enhance the solids removal. Pressure filtration is also used in this industry to reduce the solids concentration in clarifier effluent and to remove excess water from the clarifier sludge. Figure 7.4 shows a granular bed filter and Table 7.13 presents the heavy metal removal data of a lime clarification and filtration system. 

Granular bed filters are used in porcelain enameling wastewater treatment to remove residual solids from clarifier effluent (sedimentation effluent or flotation effluent). Filtration polishes the effluent and reduces suspended solids and insoluble precipitated metals to very low levels. Fine sand and coal are media commonly utilized in granular bed filtration. The filter is backwashed after becoming loaded with solids and the backwash is returned to the treatment plant influent for removal of solids in the clarification step.10-12... 

For the purification of water supplies and for waste water treatment where the solid content is about 10 g/m3 or less, as noted by Cleasby(23) granular bed filters have largely replaced the former very slow sand filters. The beds are formed from granular material of grain size 0.6-1.2 mm in beds 0.6-1.8 m deep. The very fine particles of solids are removed by mechanical action although the particles finally adhere as a result of surface electric forces or adsorption, as Ives 24 points out. This operation has been analysed by Iwasaki 25) who proposes the following equation ... 

Similar to filter backwash, the concentrate from these membranes requires treatment before it can be disposed of with the membrane concentrate. However, the total amount of solids produced after the treatment of filter backwash can be 60-80% greater than MF and UF concentrate due to the addition of coagulants prior to the granular media filters (Bergman 2007). 

A 50-liter three-neck reaction flask containing 30 liters of propionic acid was mixed with a solution of pyrrole (6.0 mol) dissolved in 583 ml of toluene and 2-pyridinecar-boxaldehyde (6.0 mol) dissolved in 432 ml toluene and then refluxed for 1 hour. The dark red-brown mixture was then stirred for 18 hours at ambient temperature and then filtered and concentrated. The residue was diluted with 5 ml toluene and then reconcentrated, this process being repeated three times. The residue was then added to 5 ml ethyl acetate and stirred 18 hours, filtered, diluted in CH2CI2, and purified with flash column chromatography on silica gel using CF C /triethylamine, 98 2, respectively. Relevant fractions were combined and concentrated and a black granular solid isolated, which was diluted with 10% aqueous ammonium hydroxide, and then stirred for 2 hours and filtered. The washed solids were dried and the product isolated as a deep metallic purple solid in 2% yield. 

Plants that bum good quality elemental sulfur or H2S gas generally have no facilities for purifying S02. Before the advent of relatively pure Frasch or recovered sulfur, however, hot gas purification was frequently used in which the S02 gas stream was passed through beds of granular solids to filter out fine dust particles just prior to its entering the converter. 

Amino-2,4,6-triiodo-N-methylisophthalamic acid (228.0 g, 4 mole) was added to stirred, heated dimethylacetamide (400 ml). When the temperature reached 95°C, adipoyl chloride (27.5 g, 0.15 mole) was added all at once, followed by an equal amount added slowly over a period of 15 min (a total of 55.0 g). After addition of the adipoyl chloride the solution was stirred at about 95°C for another 15 min, then poured into 2 L of hot water. As the above mixture cooled to room temperature a gum separated. The mother liquor was discarded and the gum was dissolved in water (2 L) with sufficient sodium hydroxide to complete solution. The solution was acidified with hydrochloric and acetic acids, treated with decolorizing charcoal and filtered. The filtrate was then strongly acidified with hydrochloric acid, which caused the separation of an apparently amorphous granular solid. This was filtered off, digested 0.5 h with hot ethanol (500 ml) collected, washed with ethanol and dried at 110°C. Yield of crude 5,5-(adipoyldiimino)-bis[2,4,6-triiodo-N-methylisophthalamic acid]. 

HCI gas was bubbled into a cooled solution of 5-methoxy-2-[(3,5-dimethyl-4-methoxy-2-pyridinyl)methylthiol]-lH-benzimidazole (50 g) in dichloromethane (250 ml) until no more precipitation was observed. The reaction mixture was warmed to 40°C and again cooled to 10°C. The solid was filtered under suction and washed with dichloromethane to yield the product (49 g) as a cream colored fine granular solid. Yield was 88.2% of theoretical. Melting point 144°-148°C. 

Also in this category is the matter of mechanical handling. The adsorbent must dump from filters, flow through driers and kiln tubes, and perform well in mechanical handling equipment. As has been shown,4 granular solids exhibit significant variations in these respects. 

Magnesium dihydride is a white, granular solid which decomposes at 310° to magnesium metal and hydrogen.11 It is stable indefinitely at room temperature when protected from moisture and oxygen. It is pyrophoric in air and reacts violently with water. The infrared spectrum of magnesium dihydride shows two broad envelopes. One is at 1400-800 cm-1, the other at 800-400 cm-1. The x-ray powder diffraction (nickel-filtered CuKa) pattern shows lines at 3.17 A (s) 2.50 A (m) 2.25 A (m) 1.67 A (w). 

Lithium trihydridozincate( 1 —) is a white, granular solid which slowly turns black on standing at room temperature. If it is stored at Dry Ice temperature, it remains white for an indefinite period of time. It is not soluble to any extent in ethereal solvents, and it is very sensitive to air and moisture. It is best identified by its x-ray powder diffraction (nickel-filtered CuKa) pattern. The predominant interplanar spacing and the corresponding relative intensities (estimated visually) are d = 6.25 A (m) 4.45 A (vs) 4.30 A (m) ... 

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