Secondary operational problems

Secondary operational problems—issues created or responded to during a process upset other than the primary problem. 

Currently, large volumes of off-gas hydrogen are either flared, burned as fuel, or routed to secondary operations within the chemical and petroleum refining industries. Such off-gas streams represent a potentially significant source of hydrogen that, if economically recoverable, could partially satisfy the near term (1988-1990) hydrogen supply problems in the U,.S. 

The preferred methods have shown exptl promise to date, while the others have objections, among which are high cost, inefficiency, operating hazards, or creation of secondary pollution problems. The identity and toxicity of all of the destruction products have not been completely determined in many cases, which must be done before any process is approved for general use... 

Wastewater treatment systems can be classified, in addition to pretreatment, as preliminary, primary, secondary, and tertiary (advanced) treatments. Pretreatment of industrial wastewater is required to prevent adverse effects on the municipal wastewater treatment plants. Preliminary treatment is considered as any physical or chemical process that precedes primary treatment. The preliminary treatment processes may consist of influent screening and grit removal. Its function is mainly to protect subsequent treatment units and to minimize operational problems. Primary treatment is defined as the physical or chemical treatment for the removal of settleable and floatable materials. The screened, degritted raw wastewater from preliminary treatment flows to the primary clarification tanks, which are part of the primary treatment facilities. Secondary wastewater treatment is the process that uses biological and chemical treatment to accomplish substantial removal of dissolved organics and colloidal materials. The secondary treatment facilities may be comprised of biological reactor and secondary clarification basins. Tertiary (advanced) wastewater treatment is used to achieve pollutant reductions by methods other than those used in primary and secondary treatments. The objective of tertiary wastewater treatment is to improve the overall removal of suspended solids, organic matter, dissolved solids, toxic substances, and nutrients. 

The activated sludge plant often has operational problems, which could be attributable to unusual characteristics of the influent wastewater or could be because of improper design and operation. These problems can be characterized by two factors low soluble BOD removal and poor settling of solids in the secondary settling tank. 

Dioxin monitoring and abatement In order to allow the full implementation of primary measures for dioxin prevention, there is a need for a better understanding of the contribution of the process parameters to the formation of dioxins. This requires the monitoring of dioxin emissions for various installations and under varying conditions. Additionally, there is a need for research on the use and effectiveness of secondary measures in the foundry industry. Secondary measures (e.g. additive injection, catalytic filter bags) have been implemented in other sectors (e.g. steel, waste incineration, non-ferrous metals production), but there is very little experience of their performance and of possible operational problems which may occur in applying then in foundries... 

The materials used for most of the low- to moderate-pressure process tooling do not lend themselves well to mechanical removal of cores. Therefore, holes are machined as secondary operations or cores are manually operated, removed, and emplaced by hand. This procedure takes more time than mechanically operated cores. However, since these are not generally high-speed processes, the additional time is not normally a problem. 

With respect to secondary-circuit operation problems arose by the steam generator leaks in 1973-1975. For ensuring the required coolant quality after the leaks prolonged operation of coolant-purification systems was called for. A great quantity of impurities, mainly of sodium-water interaction products, had accumulated in cold traps so that the operating efficiency of the traps began to decrease. To restore purification system performance, regeneration work on four secondary circuit cold traps and coolant preparation system cold traps was carried out. 

The development of an alternative fabrication technique that would solve these issues would have commercial benefits. Researchers have demonstrated that embossing techniques offer solutions to many of the previously detailed problems [3]. Localized heating coupled with embossing has been demonstrated by many researchers to fabricate micro-features on thermoplastic substrates. However, this process produces undesired flash which must be removed with costly secondary operations [4]. Because the substrate is only locally heated, the material that is displaced during the embossing caimot be captured by the embossing tool to form a flat surface. It is possible to heat the entire surface of the substrate and reform the flash to a flat surface, but this is not desirable because it increases the heat input. 

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