Computers, recycling

Jackson, D. Industries Agree on Computer Recycling, Waste Age, May 1, 2002, URL http // www.wasteage.com/magazinearticle.asp7magazinearticleid = 148084 magazineid= 12 siteid = 27 releaseid = 10166moc. 

The computer effort required for convergence depends on the number and complexity of the recycles ia the dowsheet, the nonlinearities ia the physical properties, and the nonlinearities ia the calculation of phase or chemical equiHbria. In sequential-modular simulators these calculations are converged one at a time, sequentially, and ia a nested manner. In equation-oriented simulators they are converged as a group and, ia the case of complex dow sheets involving nonideal mixtures, there could be significant reduction ia computer effort. 

Fig. 4.7. If the bar is repeatedly zone refined from left to right then more and more of the impurity will be swept to the right-hand end of the bar. A large number of zone-refining passes may be needed to make the left-hand half of the bar as pure os we need. The right-hand half is cut off and recycled. Note that eqn. (4.9) con only be used to calculate the impurity distribution produced by the first pass. A computer program has to be written to handle each subsequent pass.

The following flowsheet represents the simplest connections combined with good, inexpensive manual regulation required to execute valid experiments. This is the recommended minimum starting installation that can be expanded and made more sophisticated as need and budgets permit. The other extreme, a fully computer controlled and evaluated system that can be run without personnel will be shown later. The concepts, mentioned in Chapter 3, are applied here for the practical execution of experiments in recycle reactors. 

Computers permeate all areas of the plastics industry from the concept of a product design, to raw material, to processing, to marketing, to sales, to recycling, to government and industry regulations, and so on. Computers have their place, but most important is... 

F45 32.2 Computed assuming that 96% of oceanic biota recycled within upper 300 m... 

One technical difficulty that does beset recycling is that in many applications a variety of polymers are employed together in a complex way. It therefore becomes essential to distinguish between the various types of polymer in order to separate them. One system proposed (but not yet introduced anywhere in the world) is for the individual polymer components of complex articles such as automobiles to be identified using computer-scannable bar codes on each individual polymer component. 

Eastman chemical engineers provided innovative solutions to key steps in the methyl acetate process. Computer simulations were used extensively to test ways to minimize the size of the reactors and recycle streams, to maximize yields and conversions, and to refine the methyl acetate in a minimum number of steps. 

MITI is currently undergoing research to develop technology for the recycling of non-flammable plastics such as those used in business machines and computers. Their National Institute for Resources and Environment plans to decompose, without the production of harmful substances, non-flammable polymers by means of liquid phase hydrocracking, and to recover from them light oils such as benzene, toluene and xylene. The key to the technology, it is claimed, lies in the development of a catalyst which will be able to combine hazardous substances such as bromine and chlorine contained in the waste plastics. 

Recycled fibre such as newspaper, coloured paper, computer paper and is usually heavily contaminated with microorganisms. 

But, computational difficulties can arise due to the iterative methods used to solve recycle problems and obtain convergence. A major limitation of modular-sequential simulators is the inability to simulate the dynamic, time dependent, behaviour of a process. 

Shredded circuit boards. Circuit boards are metal boards that hold computer chips, thermostats, batteries, and other electronic components. Circuit boards can be found in computers, televisions, radios, and other electronic equipment. When this equipment is thrown away, these boards can be removed and recycled. Whole circuit boards meet the definition of scrap metal, and are therefore exempt from hazardous waste regulation when recycled. On the other hand, some recycling processes involve shredding the board. Such shredded boards do not meet the exclusion for recycled scrap metal. In order to facilitate the recycling of such materials, U.S. EPA excluded recycled shredded circuit boards from the definition of solid waste, provided that they are stored in containers sufficient to prevent release to the environment, and are free of potentially dangerous components, such as mercury switches, mercury relays, nickel-cadmium batteries, and lithium batteries. 

In the early 1980s, the world witnessed the sale of the first personal computers. Its transition from the relatively bulky and slow first units to the sleek, speed demons has made the computer truly revolutionary. With each improvement in computers, however, comes the increasing problem of what to do with the ever increasing number of computer e-wastes. The U.S. EPA estimates that nearly 250 million computers will become obsolete in the next five years in the United States alone. Unfortunately, only approximately 10% of these old computers that are retired each year are being recycled. This presents a substantial concern because toxic elements such as lead, cadmium, mercury, barium, chromium, beryllium as well as flame retardant, and phosphor are contained in a typical computer and there would be potential harm if there was a release of these elements into the environment.1... 

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