Overhead cleaning

Cleaning elements precede and follow the actual ginning or flber-seed-separatlon process. Cleaning before ginning is referred to as seed-cotton cleaning or "overhead cleaning". Lint cleaners follow the gin stands in arrangements that vary from one manufacturer to another. 

Overhead Cleaning. A dryer is usually the first item on the seed-cotton side. One effect of a dryer is to increase the cleaning efficiency of cleaners. The dryer, though not a cleaner, is regarded as essential to the proper operation of cleaners. Dryers are discussed in more detail in the lint-cleaner section. 

Seed-cotton loss in overhead cleaning equipment can range from 0.2 percent upward (28) but should not be over 1.0 percent. The amount of overhead cleaning machinery needed depends on the trash content of incoming seed cotton. Stripper-harvested cotton with over 30 percent trash can benefit from three extractor stages in addition to the two cylinder stages normally used. 

The cracked products leave as overhead materials, and coke deposits form on the inner surface of the dmm. To provide continuous operation, two dmms are used while one dmm is on-stream, the one off-stream is being cleaned, steamed, water-cooled, and decoked in the same time interval. The temperature in the coke dmm is in the range of 415—450°C with pressures in the range of 103—621 kPa (15—90 psi). Overhead products go to the fractionator, where naphtha and heating oil fractions are recovered. The nonvolatile material is combined with preheated fresh feed and returned to the furnace. The coke dmm is usually on stream for about 24 hours before becoming filled with porous coke, after which the coke is removed hydraulically. 

The normal regeneration temperature in the still will not regenerate heat-stable salts or oxazolidone-2. Therefore, a reclaimer is usually included to remove these contaminants. A side stream of from 1 to 3% of the MEA circulation is drawn from the bottom of the stripping column, This stream is then heated to boil the water and MEA overhead while the heat-stable salts and oxazolidone-2 are retained in the reclaimer. The reclaimer is periodically shut in and the collected contaminants are cleaned out and removed from the system. However, any MEA bonded to them is also lost. 

In a less fortunate situation, air for the laboratory instruments came from an overhead distribution system, often with high air velocities which carried along contaminants. Servicing of this air cleaning system was both frequent and costly. 

All pipes and fittings are transported to the pickling process in which an overhead crane is used to lower them into an acidic pickle liquor solution that chemically cleans and etches the black oxide surface layer resulting in a clean, rust-resistant pipe. 

Procedure Switch on the ultrasonic cleaning tank filled with water and watch for the position of cavitation activity through the circular rings formed on the surface of water. Hold the Al-foil on the circular ring for 2-3 min and remove. Watch the foil against the light or through an overhead projector for the holes created on it as a result of cavitation. 

The filter unit was located entirely inside the respective buildings and was independent of the ventilation system. The unit consisted of a suction box (usually floor standing) to which the filter material was attached usually as a flat vertical surface of an area to give a face velocity of about 0.75 m/s. Dust collected on this surface and was removed with a vacuum cleaner. Cleaned air was directed into an overhead discharge duct with a permeable lower surface. The capacity of the fan in the filter unit was made the same order as that of the main ventilating fan. The overhead duct was located above and as near to the stock as possible so that the clean air flowed downwards towards the stock. This air did not cause a draught because it was discharged at a low speed (0.3 m/s) and as it was recirculated it was at the same temperature as the air in the room. 

The unreacted propylene is taken off the top of the reactor and cleaned up for recycling. By bubbling this stream through a dilute caustic solution (like sodium hydroxide, NaOH), the chlorine and HCl carried along with the propylene are removed by converting them to sodium chloride, NaCl, and water. The scrubbed propylene is then taken overhead (from the top of the fractionation column) and is ready as fresh feed or use elsewhere in the plant. 

Areas where combustible powders are handled in bulk quantities or areas containing dust-producing equipment should be cleaned on a regularly scheduled basis. Horizontal overhead surfaces, such as tops of beams, and concealed or other out-of-sight spaces where dust can accumulate, should be identified and included in the cleaning schedule or changed to minimize the potential for dust collection. 

The major discharges from sulfuric acid alkylation are the spent caustics from the neutralization of hydrocarbon streams leaving the alkylation reactor. These wastewaters contain dissolved and suspended solids, sulfides, oils, and other contaminants. Water drawn off from the overhead accumulators contains varying amounts of oil, sulfides, and other contaminants, but is not a major source of waste. Most refineries process the waste sulfuric acid stream from the reactor to recover clean acids, use it to neutralize other waste streams, or sell it. 

Reforming is a relatively clean process. The volume of wastewater flow is small, and none of the wastewater streams has high concentrations of significant pollutants. The wastewater is alkaline, and the major pollutant is sulfide from the overhead accumulator on the stripping tower used to remove light hydrocarbon fractions from the reactor effluent. The overhead accumulator catches any water that may be contained in the hydrocarbon vapors. In addition to sulfides, the wastewater contains small amounts of ammonia, mercaptans, and oil. 

One night, however, the two men were standing in a cemetery at midnight in the center of an intricately drawn magic circle designed for a necromantic ritual. John had on his clean black robe and was holding his three-foot wand. Kelley held a torch overhead so that John could read the elaborate invocation. As the ghost was summoned she stood before them outside of the protective circle. Her dress was white and transparent, as was her body, and she had only a skull for a face. 

Metraxt is an aqueous system developed to clean up metals on solid surfaces. Metraxt can be applied as a foam blanket that allows application to overhead, vertical, and horizontal surfaces. This technology is formulated to extract heavy metals from concrete, asphalt, and metal surfaces by bonding with them. 

As a final step in the fractionation sequence, the hexane fraction is separated into a dimeihyibutanes concentrate as a net overhead product and an -hexane-rich bottoms stream to be recycled for the further isomerization of ihe n-hexane and methylpentancs. Wilh economically practical fractionation, Hie methylpentanes split between the overhead and bottoms of the deisohexanizer column. For the Cs fraction, the boiling points of the two isomers are far enough apart to make a relatively clean split economically feasible. For the C<, fraction, the greater number of... 

Table I contains the elemental analysis of the T102 bottoms, the material brought overhead with toluene, the residue remaining after the toluene destraction, and the starting coal used at Wilsonville during Run 242. The toluene overhead represented 66.8 percent of the material charged to the FDU, and the residue accounted for 27.9 percent. Other material collected from the FDU includes 4.2 percent in the spent solvent and 2.7 percent recovered during cleaning of the FDV and separator with tetrahydrofuran. The total material balance is 101.6 percent. This number also includes any residual toluene or tetrahydrofuran in the various samples. The overhead collected from the five destractions was ground and combined before use in the reflux mode experiments.

The total cost includes (1) fixed charges on the equipment and fixed overhead expenses, (2) steam, materials, and storage costs which are proportional to the amount of feed and evaporation, (3) expenses for direct labor during the actual evaporation operation, and (4) cost of cleaning. Since the size of the equipment and the amounts of feed and evaporation are fixed, the costs included in (1) and (2) are independent of the cycle time. The optimum cycle time, therefore, can be found by minimizing the sum of the costs for cleaning and for direct labor during the evaporation. 

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