Dust removal

Hydroxyisoquinolines. Hydroxy groups in the 5-, 6-, 7-, and 8-position show phenoHc reactions for example, the Bucherer reaction leads to the corresponding anainoisoquinolines. Other typical reactions include the Mannich condensation, azo-coupling reactions, and nitrosation. Both 0-methyl and /V-methyl derivatives are obtained from the methylation of 1-hydroxyisoquinoline, indicating that both tautomeric forms are present. Distillation of various hydroxy compounds, eg, 1- and 4-hydroxyisoquinoline, with zinc dust removes the oxygen. Treatment of 1-isoquinolinol with phosphoms tribromide yields 1-bromoisoquinoline [1532-71 -4] (178). 

Centrifugal Separation Centrifugal force can be utilized to enhance particle collection to several hundredfold that of gravity. The design of cyclone separators for dust removal is treated in detail in Sec. 17 under Gas-Solids Separations, and typical cyclone designs are shown in Fig. 17-43. Dimension ratios for one family of cyclones are given in Fig. 17-36. Cyclones, if carefully designed, can be more efficient on hquids than on solids since liquids coalesce on capture and are easy to drain from the unit. However, some precautions not needed for solid cyclones are necessary to prevent reentrainment. 

The cleaning cycles are usually controlled by a timing device which deactivates the section being cleaned. The dusts removed during cleaning are collected in a hopper at the bottom of the baghouse and then removed, through an air lock or star valve, to a bin for ultimate disposal. 

Other industries of interest are (1) the manufacturing of spices and flavorings, which may use activated carbon filters to remove odors from their exhaust stream (2) the tanning industry, which uses afterburners or activated carbon for odor removal and wet scrubbers for dust removal and (3) glue and rendering plants, which utilize sodium hypochlorite scrubbers or afterburners to control odorous emissions. 

Other Considerations Leakage of cold air into a settling chamber can cause local gas quenching and condensation. Condensation can cause corrosion, dust buildup, and plugging of the hopper or dust removal system. The use of thermal insulation can reduce heat loss and prevent condensation by maintaining the internal device temperature of the above the dew point (EPA, 1982). No pretreatment is necessary for settling chambers. 

The term three-phase fluidization requires some explanation, as it can be used to describe a variety of rather different operations. The three phases are gas, liquid and particulate solids, although other variations such as two immiscible liquids and particulate solids may exist in special applications. As in the case of a fixed-bed operation, both co-current and counter- current gas-liquid flow are permissible and, for each of these, both bubble flow, in which the liquid is the continuous phase and the gas dispersed, and trickle flow, in which the gas forms a continuous phase and the liquid is more or less dispersed, takes place. A well established device for countercurrent trickle flow, in which low-density solid spheres are fluidized by an upward current of gas and irrigated by a downward flow of liquid, is variously known as the turbulent bed, mobile bed and fluidized packing contactor, or the turbulent contact absorber when it is specifically used for gas absorption and/or dust removal. Still another variation is a three-phase spouted bed contactor. 

As the filter accumulates dust, the pressure loss increases, and the dust removed improves the normal separation. Another effect can be seen with electrostatically charged filter material. During operation, the impurities neutralize the material, and the filter s capacity to separate is reduced. Figure 9.3" shows exam-... 

As a simple and efficient particle separation device, cyclone collectors can be used for anything from dust removal in a fluid stream to material collection in the fluid conveying system. However, the cyclone is not suitable or economical for the separation of extremely small particles (say, less than 1 /xm), which frequently occur in industrial processes. It is recommended that the size of particles to be separated in an industrial ventilation cyclone be in the region of around 10 to 100 p.m. However, for the purpose of aerosol sampling, the size of particles to be separated may be much less than 10 jxm. 

Suggested Air-to-Cloth Ratios for Dust Removal from Air Type of Dnst Ratio... 

To improve the efficiency of collection, several units can be installed in series. The plate type unit is the most common design for dry dust removal, while pipe design is mainly for removal of liquid or sludge particles and volatilized fumes. The plates/pipes are the collecting electrodes, with the discharge electrodes suspended between the plates or suspended in the pipes [41,53,57],... 

FPN No. 1) The quantity of combustible dust that may be present and the adequacy of dust removal systems are factors that merit consideration in determining the classification and may result in an unclassified area. 

Methods of dust removal depend mainly on the particle size of the dust and the temperature and moisture content of the gas. The methods used are broadly divided into dry methods and wet methods. The dry methods involve the use of gravity and baffle chambers, cyclones, filters, and electrostatic precipitators, while the wet methods involve the use of spray towers and venturi scrubbers. In principle, wet cleaning is preferred to dry cleaning because of the excessive wear associated with and the difficulty in handling the fine dusty material removed in the dry methods. The wet methods, however, must be followed by such operations as filtration, drying of filter cakes, and recycling of water. 

Use of low-NO, burners to reduce NO, emissions from burning fuel in ancillary operations use of dry SO-, and dust removal systems in hue gases... 

Rosin, P., Rammler, E., and Intelmann, W., Principles and Limits of Cyclone Dust Removal, Zeit. Ver. Deutscher Ing., 76 433ff (1932)... 

Ciborowski, J., andZakowski, L., Dust removal in a fluidized bed II. Electrostatic effects in a fluidized bed and their effect on dust-removal process efficiency, Inz. Chem., 5 753-762 (1975) English translation in Int. Chem. Engrg., 17 538-548(1977)... 

Rudnick, S.N., W.C. Hinds, E.F. Maher, and M.W. First, Effect of Plateout, Air Motion and Dust Removal on Radon Decay Product Concentration in a Simulated Residence, Health Phvs. 45 463-470... 

Safety aspects of drum storage, pellet screening, dust removal, reactor loading and unloading, and activation of process catalysts are discussed [1], and reprocessing aspects are considered, with disposal as a last resort [2], Hydrogenation catalysts introduce their own problems [3],... 

So far there has been little research and development work on dust collection systems which are self cleaning and can be cheaply installed in livestock buildings. The papers suggest that improved livestock environment by dust removal can have an economic advantage in terms of earlier marketing of pigs. 

The American Textile Industry Involvement with cotton dust as a workplace hazard began over ten years ago with Industry studies to determine whether the Industry had such an Illness problem. Then followed major dust removal and ventlllatlon efforts. The Industry developed a work practices and medical surveillance program which was presented to OSHA. 

Measurable quantities of cotton dust were extracted from small cotton lint samples by means of high-velocity air jets. Dust removed in this manner was sized by a wire-mesh screen that restricted the flow of particles larger than the openings in the screen. Particles smaller than the openings in the screen were collected for gravimetric analysis. 

Figure 8. Cumulative distribution curves of distributions shown in Figure 7. Key , cotton control O, 0.60% Milube N-32 A, distribution of dust removed from card room atmosphere when Milube N-32 is added to cotton.

The technology licensors have taken different approaches to improving dust removal efficiency, but the designs are all based on the fundamentals discussed above. 

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