Economics, modern

Interest in the application of turboexpanders turbine to FCC unit is very high, and deservedly so. The power recovery turboexpander offers practical improvement in FCC unit operating economics. Modern designs that encompass the entire system have fully overcome problems and concerns that may have existed decades ago. Expander metallurgy is available to vastly reduce erosion rates experienced when... 

The critical role of agriculture cannot be overemphasized as an obvious axiom of the policy of self-reliance, which is the ability to feed its own population. Political slogans such as "Agriculture as Foundation" and "Industry Must Aid and Serve Agriculture" are just some indications of the primary importance accorded to agriculture. (A separate Ministry of Food was established on June 12, 1979, with Zhao Xinchu—full member of the 11th Central Committee of the CCP—as its first Minister.) Agricultural development will continue to be viewed as the fundamental basis for economic modernization, and the point of departure for pursuit of import substitution policies. 

At first sight, a simultaneous instrument may seem attractive as an alternative to buying separate units. A case has been made for this on economic grounds (initial purchase, running costs etc.) but the main advantages are technical, not economic. Modern simultaneous devices are capable of excellent performance, but it is still the case that they will not perform the individual measurement tasks as well as dedicated separate units. Their advantage lies in the unambiguous correlation of the two or more sets of information. 

At one time acetaldehyde was prepared on an industrial scale by this method Modern methods involve direct oxidation of ethylene and are more economical... 

A development of interest to the chemical industiy is the tubular precipitator of reinforced-plastic construction (Wanner, Gas Cleaning Plant after T1O2 Rotary Kilns, technical bulletin, Lurgi Corp., Frankfurt, Germany, 1971). Tubes made of polyvinyl chloride plastic are reinforced on the outside with polyester-fiber glass. The use of modern economical materials of construction to replace high-maintenance materials such as lead has been long awaited for corrosive applications. 

Selective gas permeation has been known for generations, and the early use of p adium silver-alloy membranes achieved sporadic industrial use. Gas separation on a massive scale was used to separate from using porous (Knudsen flow) membranes. An upgrade of the membranes at Oak Ridge cost 1.5 billion. Polymeric membranes became economically viable about 1980, introducing the modern era of gas-separation membranes. Hg recoveiy was the first major apphcation, followed quickly by acid gas separation (CO9/CH4) and the production of No from air. 

Modern day turbomachinery is built to last between 30-40 years. Thus, the keeping of basic maintenance records and critical data is imperative for a good maintenance program. Economic justification is always the controlling factor for any program, and maintenance practices are not different. 

Acetylene and ethylene compete as a chemical raw material. Ethylene is generally more economical, resulting in declining use of acetylene as a raw material. Calcium carbide, a raw material for acetylene has other uses. Treated with nitrogen, it gives calcium cyanamide, valuable as a fertilizer and weed killer, and a raw material for the production of melamine, used ir ng some modern plastics. 

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