Collection hoods

Coefficient of hood entry The coefficient describing the pressure drop that occurs when gases flow through a collecting hood or other enclosure. 

Laboratories are normally classified nonhazardous locations if the quantities of flammable and combustible liquids are within the requirements of NFPA. Normally a vapor collection hood is provided when sampling and measurements are conducted with exposed liquids. The primary concern is the exhaust of vapors and the storage and removal material saturated with liquids. The exhaust hood, ducting and a radius of 1.5 meters (5 ft.) from the exhaust vent should be considered an electrically classified area. 

The ISV process uses electricity to heat and melt soil and other earthen materials contaminated with organic, inorganic, and radioactive compounds. Organic compounds undergo pyrolysis (thermal decomposition in the absence of oxygen). The pyrolyzed compounds then migrate to the surface zone, where they are collected and oxidized in a collection hood. Inorganic and radioactive components are incorporated as oxides into a leach-resistant vitrified product. 

At the Ronnskar works of Boliden AB in Sweden, which include both a copper and a lead smelter, a cyclic process using water as the absorbent concentrates sulfur dioxide both to produce liquid sulfur dioxide and for feed to acid plants (20, 21). The process is reported to give an absorption efficiency of about 98% on gas containing 2% sulfur dioxide. Water is not normally a favorable solvent for such an application but can be used in this case because it is available at a low temperature, less than 5°C for most of the year. Recovery of sulfur dioxide from the complete smelter is to be increased from 90 to 95% by applying water-cooled collecting hoods and waste heat boilers to all the copper converters (20). 

Installing the melter above ground level. This arrangement was found to be better as it minimized exposure of workers to vapors from the melter. An exhaust fan with a collection hood is also provided on the grid where raw sulfiir is generally dumped. 

The new UL test method utilises a collection hood and duct system prescribed under various nationally recognised fire test procedures including the UL 1715 Standard [54]. The test structure is a masonry room measuring 2.4 m wide by 3.7 m long by 2.4 m high, with one 2.4 m wide open end. Heptane fuel burners are used to provide the internal fire source. The test method utilises oxygen consumption calorimetry to quantify the roof covering materials. 

Dust collection hood, exhaust blower, dust separator shall be available to cover the screen, fines collection etc. 

Dust collection hood over rotary screen with exhaust blower and scrabber/cy-clone separator... 

Figure 21.5 Portable collecting hood. (Courtesy My son Marketing Services Ltd)...

Dust control equipment includes collection hoods, fabric and fiber filters, reverse jet filters, wet and dry precipitators, cyclones, and scrubbers [27]. Selection depends on particle size and density of the material, volume and temperature of air to be treated, efficiency, economic considerations, and dust diaracteristics. Dusts that are sticky, fluffy, erosive, toxic, or combustible demand special consideration. The efficiencies of various types of collectors have been tabulated, along with a guide to selection for various applications [28]. This information is siunmarized in Tables 2-8 and 2-9. A combination of devices often will be more effective than a single t)q)e. 

Laboratories are normally classified as non-hazardous locations if the quantities of combustible materials are within the requirements of NFPA. Normally a vapor collection hood is provided when sampling and measurements are conducted with exposed hazardous materials. The primary... 

Non-Fugitive Dust (EL) There are no national enforceable standards such as PM 10 that are legislated for non-fugitive dust generated inside a conveyor such as bucket, screw or pneumatic, collecting hood and ducting, or inside a vessel such as a silo, bag filter, a storage or transportation tank. 

Handling of alumina and coke presents dusting problems. Hoods and exhaust systems collect the dust, which is then separated from the exhaust air either by cyclones, electrostatic precipitators, filter bags, or a combination of these methods, and recycled to the process (see Air pollution control PffiTHODS). 

The final ceU product contains 250—300 g/L H2SO in the last stages of electrolyte purification, and antimony and bismuth precipitate, resulting in heavily contaminated cathodes that are recycled through the smelter. Arsenic and hydrogen evolved at the cathodes at these later stages react to form arsine, and hoods must be provided to collect the toxic gas. 

One hundred grains (0.7S mole) of -methylacetophenonc is added to a mixture of 250 ml. (4 moles) of concentrated nitric acid (sp. gr, 1.42) and 1 1. of water in a 3-1. flask, and the mixture is refluxed in a hood for 4 hours. After the mixture has been cooled, the sticky, yellow solid is collected on a 14-cm. Biichner funnel, pressed down well, and washed with 300 ml. of cold water. 

Alloys of nonferrous metals, primarily the brasses (copper and zinc) and the bronzes (copper and tin), can cause an air pollution problem during melting and casting. The type and degree of emissions depend on the furnace and the alloy. Control systems consist of hoods over the furnaces and pouring stahons to collect the hot gases, ducts and fans, and baghouses or ESPs. 

The electric arc furnace process accounted for about 25% of the 1982 U.S. steelmaking capacity (14). Most of the raw material used for the process is steel scrap. Pollutants generated by the electric furnace process are primarily particulate matter and CO. The furnaces are hooded, and the gas stream containing the particulate matter is collected, cooled, and passed to a bag-house for cleaning. Venturi scrubbers and ESPs are used as control devices at some mills. Charging and tapping emissions are also collected by hoods and ducted to the particulate matter control device. 

A small amount of dimethylamine is always present in the crude product. This is removed before collection of the product by operating the column under total reflux for 1-2 hours. The vent of the still head should be connected to a hood during this operation. If foaming does not subside after this treatment the use of a 1-1. still pot is indicated. 

The use suction hoods to collect vapors and other fugitive emissions. 

Use doghouse enclosures where appropriate use hoods to collect fugitive emissions. 

---