Environmental concerns, design

Based on dryer cost alone, indirect-heat dryers are more expensive to build and install than direct-heat dryers designed for the same duty. As environmental concerns and resulting restrictions on process emissions increase, however, indirect-heat dryers are more attractive because they employ purge gas only to remove vapor and not to transport heat as well. Dust and vapor recovery systems for indirect-heat dryers are smaller and less cosdy to supply heat for drying, gas throughput in direct-heat dryers is 3—10 kg/kg of water evaporated indirect-heat dryers require only 1—1.5 kg/kg of vapor removed. System costs vary directly with size, so whereas more money may be spent for the dryer, much more is saved in recovery costs. Wet scmbbers ate employed for dust recovery on indirect-heat dryers because dryer exit gas usually is close to saturation. Where dry systems are employed, all external surfaces must be insulated and traced to prevent vapor condensation inside. 

Potential environmental concerns should be addressed through system design and monitoring. The following items are provided as a guide ... 

Solvents play an important role in organic synthesis. Choice of solvent is important in improving and deciding the chemical process. Selection of solvents should be such that it has minimal effect on the environment. Today chemists are interested in designing solvents which does not pose any risk to human health and the environment. The reason why solvents are of great environmental concern is that... 

Keywords Concentrate blending Concentrate transport regulations Environmental concerns Outfall design... 

Keywords Aquifer contamination Confining layer Costs Environmental concerns Receptor zones Site selection Well design Well drilling... 

Due to the capacity of deep wells to store injected waste for a long period of time, if the correct measures are taken in design, construction and operation, deep well injection can provide an effective and environmentally safe method of concentrate management. The major environmental concern for deep well injection is the potential for contamination of nearby aquifers, which may be used as a source of drinking water. Six pathways have been defined that describe the potential migration of concentrate that can cause contamination of aquifers (Shammas et al. 2009 United States Environmental Protection Agency 2002) ... 

Keywords Costs Environmental concerns Evaporation pond design Evaporation rate Liners Pond area Pond banks Pond depth Social impacts... 

Rodenticides are clearly designed to kill animals and, thus, with the exception of thiourea compounds, are toxic to humans and should be avoided. Environmental concerns occur when other animals consume a poisoned rodent and are in turn poisoned. Eagles, wolves, and other animals high in the food chain are particularly vulnerable. 

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. 

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