Process equipment environmental concerns

Synthetic Processes. Traditional Solvay plants produce large volumes of aqueous, chloride-containing waste which must be discharged. This fact, in addition to a noncompetitive cost position, is largely responsible for the demise of U.S. synthetic plants. In countries other than the United States, waste is sent to the ocean, rivers, or deep underground wells. The AC and NA coproduct processes produce less aqueous waste than the traditional Solvay and NA mono processes. Related environmental concerns are added whenever a plant complex includes lime quarries and ammonia-producing equipment. 

The formulation of a carrier depends on four considerations (/) the carrier-active chemical compound (2) the emulsifier (J) special additives and (4) environmental concerns. Additional parameters to be considered in the formulation of a carrier product with satisfactory and repeatable performance arise from the equipment in which the dyeing operation is to be carried out. The choice of equipment is usually dictated by the form in which the fiber substrate is to be processed, eg, loose fiber, staple, continuous or texturized filament, woven or knot fabric, yam on packages or in skeins (see Textiles). 

The Chemical Process Industry (CPI) uses various quantitative and qualitative techniques to assess the reliability and risk of process equipment, process systems, and chemical manufacturing operations. These techniques identify the interactions of equipment, systems, and persons that have potentially undesirable consequences. In the case of reliability analyses, the undesirable consequences (e.g., plant shutdown, excessive downtime, or production of off-specification product) are those incidents which reduce system profitability through loss of production and increased maintenance costs. In the case of risk analyses, the primary concerns are human injuries, environmental impacts, and system damage caused by occurrence of fires, explosions, toxic material releases, and related hazards. Quantification of risk in terms of the severity of the consequences and the likelihood of occurrence provides the manager of the system with an important decisionmaking tool. By using the results of a quantitative risk analysis, we are better able to answer such questions as, Which of several candidate systems poses the least risk Are risk reduction modifications necessary and What modifications would be most effective in reducing risk ... 

Selection of a suitable method for silver removal depends on many factors what processes the company uses, what volume of wastes the company produces, what kind of training and technical knowledge the company s personnel has, whether the company wants to reuse the company s fixer or bleach-fix, how much the company wants to spend for recovery equipment, and what the environmental concerns are, such as how strict the effluent discharge limits are. Just considering these factors makes choosing a silver recovery method very much an individual decision for each company. 

A good design is both art and science. Creativity is needed to come up with a product concept that has either not been considered before or has been considered and abandoned. Discipline is needed to investigate and evaluate all the details to make sure that they fit together, which is an exercise in multiscale optimization the product structure is in the molecular scale of nanometers to micrometers, the process equipment is in centimeter to meter scales, marketing and finance are played in the meter to hundred kilometer scales, and environmental concerns are on a global scale. 

Reductions often pose scale-up concerns. The primary difficulty is that hydrogen is used or generated, which requires additional considerations and equipment for safe handling. At the end of a reaction, safely quenching any residual reducing capability is a concern on scale. Work-up can be tedious, especially if colloidal salts are formed. Disposing of metal salt by-products can be costly, and environmental concerns arise. Considerable attention to details is necessary to develop a reliable reduction for scale-up. In spite of these potential drawbacks, once the process has been developed and the appropriate equipment has been commissioned, reductions can be extremely reliable. 

Ever-increasing environmental concerns may make it necessary to evaluate the existing process to reduce emissions, operator exposure, limit waste disposal of filter aid, or reduce wash quantities requiring solvent recovery or wash treatment. Breakdown of an old piece of equipment often provides the opportunity and justification to improve plant conditions. New grass roots designs may have the tendency to revert to industry standards. This is also the opportunity to improve conditions or substantiate the current equipment of choice. 

The vinyl ester fimctionality of the epoxy vinyl esters provides outstanding hydrolysis and chemical resistance properties, in addition to the inherent thermal resistance and toughness properties of the epoxy backbone. These attributes have made epoxy vinyl esters a material of choice in demanding structural composite applications such as corrosive chemicals storage tanks, pipes, and ancillary equipment for chemical processing. Other applications include automotive valve covers and oil pans, boats, and pultruded construction parts. Significant efforts have been devoted to improve toughness and to reduce levels of styrene in epoxy vinyl ester formulations because of environmental concerns. In addition to Dow Chemical, other major suppliers of epoxy vinyl esters include Ashland, AOC, DSM, Interplastic, and Reichhold (DIG). 

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