Filters liquid-solid

Heat a mixture of 49 g. of acetylmethylurea (3) and 50 ml. of concentrated hydrochloric acid, with hand stirring, on a steam bath until it is apparent that no more solid is dissolving (4) and continue the heating for 3—4 minutes longer the total time of heating on the steam bath should be 8-12 minutes. Dilute the solution with 50 ml. of water and cool below 10° in an ice bath. Run in slowly and with stirring a cold saturated solution of 38 g. of A.R. sodium nitrite in 55 ml. of water below the level of the liquid. Keep the mixture in the ice bath for 5-10 minutes, filter the solid at the pump and wash it with 8-10 ml. of ice-cold water. Dry the nitrosomethylurea (pale yellow crystals) in the air or in a. vacuum desiccator (5) the yield is 34 g., m.p. 12 124°. 

While research has developed a significant and detailed filtration theory, it is still so difficult to define a given liquid-solid system that it is both faster and more accurate to determine filter requirements by performing small-scale tests. Filtration theoiy does, however, show how the test data can best be correlated, and extrapolated when necessary, for use in scale-up calculations. 

In many important cases of reactions involving gas, hquid, and solid phases, the solid phase is a porous catalyst. It may be in a fixed bed or it may be suspended in the fluid mixture. In general, the reaction occurs either in the liquid phase or at the liquid/solid interface. In fixed-bed reactors the particles have diameters of about 3 mm (0.12 in) and occupy about 50 percent of the vessel volume. Diameters of suspended particles are hmited to O.I to 0.2 mm (0.004 to 0.008 in) minimum by requirements of filterability and occupy I to 10 percent of the volume in stirred vessels. 

Semidry Scrubbers The advantage of semidry scrubbers is in that they remove contaminants by way of a solid waste that is easier to dispose of (less expensive). Initially, the scrubbing medium is wet (such as a lime or soda ash slurry). Then a spray dryer is used to atomize the slurry into the gas which evaporates the water in the droplets. As this takes place, the acid in the gas neutralizes the alkali material and forms a fine white solid. Most of the white solids are removed at the bottom of the scrubber while some are carried into the gas stream and have to be removed by a filter or electrostatic precipitator (discussed later). Although semidry systems cost 5-15% more than wet systems, when combined with a fabric filter, they can achieve 90-95% efficiencies. Dry scrubbers are sometimes used in a very similar fashion, but without the help of gas-liquid-solid mass transfer, these systems use much higher amounts of the solid alkali materials. 

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... 

Wakeman, R.J., 1990a. Pressure filters. In Solid-liquid separation, 3rd edition. Ed. L. Svarovsky. Oxford Butterworth-Heinemann. 

Evaporate the dried chloroform solution to a residue, add to the residue 400 ml of liquid ammonia, stir and allow the excess ammonia to evaporate, triturate the residue with hexane to form a crystalline solid, continue trituration with water, and filter the solid to yield substantially pure 2-sulfamyl-4-chloro-nitrobenzene. Recrystallize from aqueous methanol. 

Figure 4-78. Tubular in-line pressure filter with reusable elements. The flow unfiltered liquid enters the inlet port, flows upward, around, and through the media, which is a stainless steel or fabric screen reinforced by a perforated stainless steel backing. Filtered liquid disch lrges through the outlet (top) port. Because of outside-to-lnside flow path, solids collect on the outside of the element so screens are easy to clean. By permission, Ronningen-Petter Engineered Filter Systems, Bulletin RP-2.

When a slurry flows through a filter, the solid particles become entrapped by the filter medium which is permeable only to the liquid. Either of two mechanisms are used cake filtration or depth filtration. 

The filtrate that is back-pulsed from the dome first expands the filter socks thereby cracking the cake. The movement of the socks and the subsequent liquid flow through them serves to dislodge the filter cake solids from the GORE-TEX membrane surface. Because of the expanded PTFE material of the membrane, the cake releases from... 

The environmental impact of the proposed GATS process appears to be minimal. All handling and processing of agent will be conducted indoors in sealed rooms that are vented through HEPA and carbon filters. Liquid and solid waste streams will be relatively small and manageable and will be subjected to hold-test-release procedures. 

Anaerobic Filter. An anaerobic filter consists of packed support media that traps biomass as well as facilitates attached growth of biomass as a biofilm (Fig. 8). Such a reactor configuration helps in the retention of suspended biomass as well as gas-liquid-solid separation. The flow of liquid can be upward or downward, and treatment occurs due to attached and suspended biomass. Treated effluent is collected at the bottom or top of the reactor for discharge and recycling. Gas produced in the media is collected underneath the bioreactor cover and transported for storage or use. Volumetric loading rates vary from 5 to 20 kg COD/m day with HRT values of 0.5-4 days. 

A solution of 300 g. (2.4 moles) of technical dimethyl aniline in 1050 cc. of concentrated hydrochloric acid is placed in a large jar or crock and finely divided ice added until the temperature has fallen to 5 °. The contents of the jar are then stirred mechanically, and a solution of 180 g. (2.6 moles) of sodium nitrite in 300 cc. of water is slowly added from a separating funnel, the stem of which dips beneath the surface of the liquid. The addition takes one hour, and the temperature is kept below 8° by the addition of ice if necessary. When all the nitrite has been added the mixture is allowed to stand one hour and then filtered. The solid -nitrosodimethylaniline hydrochloride is washed with 400 cc. of 1 1 hydrochloric acid and then with 100 cc. of alcohol. After drying in air, it weighs 370-410 g. (80-go per cent of the theoretical amount). 

Evaporate the dried chloroform solution to a residue, add to the residue 400 ml of liquid ammonia, stir and allow the excess ammonia to evaporate, triturate the residue with hexane to form a crystalline solid, continue trituration with water, and filter the solid to yield substantially pure 2-sulfamyl-4-chloro-nitrobenzene. Recrystallize from aqueous methanol. Mix together 4.4 grams of ammonium chloride, 18 ml of methanol, 9 ml of water and 3.0 grams of 2-sulfamyl-4-chloro-nitrobenzene. Heat the mixture to reflux. Add portionwise 4.4 grams of iron filings during a period of about IV2 hours. Cool the mixture and filter. Concentrate the filtrate to a residue. Triturate the residue with 15 ml of water and filter the solid. Recrystallize the solid from aqueous methanol to yield substantially pure 2-sulfamyl-4-chloroaniline. 

Solid particles are in the range of 0.01 to 1.0 mm (0.0020 to 0.039 in), the minimum size limited by filterability. Small diameters are used to provide as large an interface as possible to minimize the liquid-solid mass-transfer resistance and intraparticle diffusion limitations. Solids concentrations up to 30 percent by volume may be handled however, lower concentrations may be used as well. For example, in hydrogenation of oils with Ni catalyst, the solids content is about 0.5 percent. In the manufacture of hydroxylamine phosphate with Pd-C, the solids content is 0.05 percent. 

Laskin-Type Nozzle Generator. A third type of atomizer, the Laskin-type nozzle generator, is used to create test atmospheres of particulate or aerosol and vapor mixtures. A pure liquid or melt is used, and no solvent is necessary. Again, this is important for evaluating filter and solid sorbent combination sampling trains. 

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