Overheads general

Fixed manufacturing costs inclnde manufacturing labor, plant maintenance, and other plant-related costs that do not vary with production volume. These costs, plus corporate services and associated overhead, generally contribnte 10-20% of total product cost. 

Suitable catalysts include the hydroxides of sodium (119), potassium (76,120), calcium (121—125), and barium (126—130). Many of these catalysts are susceptible to alkali dissolution by both acetone and DAA and yield a cmde product that contains acetone, DAA, and traces of catalyst. To stabilize DAA the solution is first neutralized with phosphoric acid (131) or dibasic acid (132). Recycled acetone can then be stripped overhead under vacuum conditions, and DAA further purified by vacuum topping and tailing. Commercial catalysts generally have a life of about one year and can be reactivated by washing with hot water and acetone (133). It is reported (134) that the addition of 0.2—2 wt % methanol, ethanol, or 2-propanol to a calcium hydroxide catalyst helps prevent catalyst aging. Research has reported the use of more mechanically stable anion-exchange resins as catalysts (135—137). The addition of trace methanol to the acetone feed is beneficial for the reaction over anion-exchange resins (138). 

The sulfate ester hydrolysate is stripped to give a mixture of isopropyl alcohol, isopropyl ether, and water overhead, and dilute sulfuric acid bottoms. The overhead is neutralized using sodium hydroxide and refined in a two-column distillation system. Diisopropyl ether is taken overhead in the first, ie, ether, column. This stream is generally recycled to the reactors to produce additional isopropyl alcohol by the following equiUbrium reaction ... 

The difference between life cycle costs and the traditional accounting cost is that traditional costs are fairly easy to quantify, whereas life cycle costs are usually difficult to quantify and are usually either lumped iato general overhead costs or ignored altogether. They are very real, however, and when examined ia detail and fully quantified, the economics of composites allow them to displace the traditional materials. 

More curved the boundary, less recycle requited (generally less favorable for minimum boiling azeotropes because of large overhead recycles). 

Medium Boiling Esters. Esterificatioa of ethyl and propyl alcohols, ethylene glycol, and glycerol with various acids, eg, chloro- or bromoacetic, or pymvic, by the use of a third component such as bensene, toluene, hexane, cyclohexane, or carbon tetrachloride to remove the water produced is quite common. Bensene has been used as a co-solvent ia the preparatioa of methyl pymvate from pymvic acid (101). The preparatioa of ethyl lactate is described as an example of the general procedure (102). A mixture of 1 mol 80% lactic acid and 2.3 mol 95% ethyl alcohol is added to a volume of benzene equal to half that of the alcohol (ca 43 mL), and the resulting mixture is refluxed for several hours. When distilled, the overhead condensate separates iato layers. The lower layer is extracted to recover the benzene and alcohol, and the water is discarded. The upper layer is returned to the column for reflux. After all the water is removed from the reaction mixture, the excess of alcohol and benzene is removed by distillation, and the ester is fractionated to isolate the pure ester. 

Indirect Manufacturing Costs Estimates for the cost of payroh overhead, control laboratoiy, general plant overhead, packaging, and storage facilities are best based on company records for similar processes. 

Companies usually include in the charge for overhead the following items operating supphes, supervision, indirect payroll expenses, plant protection, plant office, general plant overhead, and control laboratory. This overhead charge is frequently taken as an equivalent percentage of the direc t labor cost. 

Static and Flexible Budgets Overhead cost can significantly affect the profitability of a projec t and is the only cost outside the control of the project manager. The project is expected to contribute a definite amount toward the expenses of the company and will be charged this amount even if the production rate is zero. This is the fixecTcomponent of the overhead cost and will include directly allocable costs such as depreciation and a proportion of general costs such as office salaries and heating. 

Various types of overhead and underground distribution systems may be used depending on local conditions. Generally, an overhead system will incur only about 30 percent of the cost of an underground distribution system. 

Air-Cooled Overhead Condensers Air-cooled overhead condensers (AOC) have been designed and installed above distiUation columns as integral parts of distiUation systems. The condensers generally have incliued tubes, with air flow over the finned sur ces induced by a fan. PrevaUing wind affec ts both structural design and performance. 

Specification tor power driven overhead travelling cranes, semi-goliath and goliath cranes for general use... 

Petroleum products may be treated with various solvents for the removal by selective solubility of undesirable constituents or for the recovery of by-products. The solvent and solute must be separated to yield the desired product and to recover the solvent for reuse. The solvents normally boil at a lower temperature than the products from which they are to be removed and so are generally distilled off as overhead products. The pipe stills used for this service may be single-stage or multi-stage units, depending on the service involved. Some solvents can be removed by the use of steam heated stills. In other cases, the high temperature required necessitates the use of fired heaters and vacuum towers. 

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