Example: dental hygienist

Chemical Recycling of Polymer Materials - Weebly

ReviewChemical Recycling of Polymer MaterialsByFrank SasseandGerhard Emig*Dedicated to Prof. Dr. Ulrich Hoffmann on the occassion of his 60th birthdayAfter the first life cycle of plastics various Recycling processes are available for further utilization of these valuable Materials . Foran ecologically and economically satisfying solution the most suitable process has to be Chemical Recycling polymers are degraded to basic Chemical substances which can be reused in the petrochemical industry. Forsoiled waste plastics or waste plastics which could not be recycled until now, Chemical Recycling plays a key pyrolysis of acrylic polymers provides a good example for comparing a fluidized-bed reactor and a tubular reactor on thebasis of reactor modelling evaluations.

soiled waste plastics or waste plastics which could not be recycled until now, chemical recycling plays a key role. The pyrolysis of acrylic polymers provides a good example for comparing a fluidized-bed reactor and a tubular reactor on the

Tags:

  Chemical, Material, Plastics, Recycling, Polymer, Chemical recycling of polymer materials

Information

Domain:

Source:

Link to this page:

Please notify us if you found a problem with this document:

Other abuse

Transcription of Chemical Recycling of Polymer Materials - Weebly

1 ReviewChemical Recycling of Polymer MaterialsByFrank SasseandGerhard Emig*Dedicated to Prof. Dr. Ulrich Hoffmann on the occassion of his 60th birthdayAfter the first life cycle of plastics various Recycling processes are available for further utilization of these valuable Materials . Foran ecologically and economically satisfying solution the most suitable process has to be Chemical Recycling polymers are degraded to basic Chemical substances which can be reused in the petrochemical industry. Forsoiled waste plastics or waste plastics which could not be recycled until now, Chemical Recycling plays a key pyrolysis of acrylic polymers provides a good example for comparing a fluidized-bed reactor and a tubular reactor on thebasis of reactor modelling evaluations.

2 The used tubular reactor with internal mass transport is a simplified model for a rotarykiln. Relevant parameters for reactor design and scale-up are Problem of Polymer WastesThe problems of used polymers do not derive from thenecessity of saving natural resources, because only approx. 4 8 % of crude oil is used for Polymer production. Thepredominant portion of crude oil (86 %) is still worldwideused as a source of energy [1]. Therefore, it would be morereasonable to save natural resources by reducing necessity of Polymer Recycling is a result of theincreasing quantity of Polymer wastes with landfilling areasdecreasing at the same time, and of the understanding that aused Polymer is a valuable raw Legal Guidelines in GermanyThe further utilization of used polymers in Germany isregulated by several legal standards, , by acts, decrees andadministrative Germany, mainly three different laws regulate the field ofenvironmental care:lthe Recycling and Waste Act (Kreislaufwirtschafts- undAbfallgesetz, KrW-/AbfG),lthe Immission Act (Bundesimmissionsschutzgesetz,BimSchG),l the Chemicals Act (Chemikaliengesetz, ChemG).

3 Further rules that directly or indirectly influence therecycling of polymers are the acts, decrees and technical rulesfor packaging Materials , municipal waste, air pollution, waterand risk Quantity of Polymers UsedIn Germany, a total of 11 million tons of polymers wereproduced in 1995, which is about 10 % of the worldproduction. In the same year, 3 million tons of Polymer wastematerial were obtained, as depicted in Fig. 1. As polymermaterials are usually very longlived, the amounts of wasteobtained clearly delay behind Polymer production andproduct consumption. For this reason, an overproportionalincrease in Polymer wastes has to be expected accordingly inthe next years. Polymers have been applied as Materials on alarger scale only for 30 years, and the present waste has itsorigin mainly in short- and medium-term applications.

4 InGermany, a total of million tons of Polymer wastes wererecycled in 1995, which is roughly one half of all wastesobtained in an amount of 3 million tons. With million tonspackaging holds the largest share of the total amount ofpolymer wastes. The remaining million tons of wastes havetheir origin in the fields of automobiles ( tons),electronics ( tons), building ( tons), polymerprocessing and manufacturing ( tons) and others( tons). In the fields of building, electronics andautomobile approx. tons of Polymer wastes could berecycled ( material Recycling !). Related to the quantity ofmunicipal waste and commercial waste similar to municipalwaste of about million tons [2], the share of polymers isapprox.

5 8 or 20 The Polymer wastes which arerecycled come from production and manufacturing wastes(55 %) and from used products (45 %). Among the last, tons result from collections of the Dual SystemGermany' (DSD).Fig. 1 presents the ratios of production, consumption andwaste. Additionally, Fig. 1 also clearly shows that the bulkquantities of recycled Polymer wastes come from thepackaging sector, which is controlled by legal standards, andfrom processed manufacturing wastes, which can be recycledChem. Eng. Technol. 21(1998) 10, WILEY-VCH Verlag GmbH, D-69469 Weinheim, 19980930-7516/98/1010-00777 $ +.50/0777 [*] F. Sasse, Prof. Dr. G. Emig, Department of Industrial ChemistryI, Friedrich-Alexander-University of Erlangen-N rnberg, Egerland-stra e 3, D-91058 Erlangen, Germany.

6 Fax: 09131/8574210930-7516/98/1010-0777 $ +.50/0778 WILEY-VCH Verlag GmbH, D-69469 Weinheim, 19980930-7516/98/1010-00778 $ +.50/0 Chem. Eng. Technol. 21(1998) 10without economical or technological problems. Here isobviously a potential of used polymers which has not beenexploited so Quantities of Acrylic PolymersAcrylic polymers, polymethylmethacrylates (PMMA) andtheir copolymers, are not bulk polymers. Because of their highquality and optical properties, they are applied mainly in fieldswhere high transparency and colorfast properties arerequired. Examples are light coverings and automobile rearlights. In 1993, the world production totalled 1 million tons,divided in roughly one third on Europe, Japan and the USA[3]. Acrylic polymers are fabricated mainly as longlivedconsumer goods.

7 One-way articles of PMMA are used at mostfor hygienic reasons, , in the health care polymers will not be used as packaging Materials orappear in domestic Chemical Recycling ProcessesAt the end of the first life cycle of Polymer material variousprocesses for the Recycling of used polymers are an ecological point of view a convincing optimalsolution for the Recycling problem cannot be found as allrecycling processes use up energy and raw Materials . Thechoice of the most suitable process has to be made byconsidering ecological and economical criteria. Yet, eachspecial waste problem has to be solved for its own. In thefollowing, the usual Recycling terminology will be explained inmore detail.

8 material Recycling ' can be described as the reprocessingof used plastics as Polymer raw Materials in a physicalprocess (remolding or regrinding processes). The chemicalstructure of the polymers is not changed. For this purpose,above all classified and clean Polymer wastes obtainedduring Polymer production and processing are well suited. Inthe case of postconsumer wastes, Materials as collectedwithin the German DSD system, above all bottles and sheetscan be used. Chemical Recycling ' is understood as the conversion ofplastic Materials into low-molecular products which can bereused as raw Materials for the production of high-qualitychemical products. Here the slogan oil Polymer oil/gases Polymer ' gets a real meaning.

9 The advantage of chemicalrecycling is the possibility of using mixed and/or soiled wastematerials. Here, processes which convert certain polymerclasses into monomer fractions are of special a wider sense, the use of polymers as reduction agent(reduction process) in a blast furnace for steel production canalso be regarded as a Recycling badly soiled small-sized and mixed Polymer wastes theenergetical usage may be a useful alternative. In this case thehigh energy content of the Polymer material is exploited ( ,in the cement production).In the following, the material Recycling as well as theenergetical usage will not be discussed. Processes of chemicalrecycling usually need an integrated flow of material andenergy within the framework of Chemical industry because oftheir appreciable complexity.

10 Therefore, the processes knowntoday are all integrated into larger Chemical complexes. Often,these larger plant sites also guarantee the further utilization ofall products and residuals generated. Only in this way aneconomical operation is possible. A further requirement foran economical operation of a process is the guaranteed supplyof feed material . The further extension of the BASF pyrolysisprocess had to be stopped, because the amount of polymerwaste of t/a needed as a minimum feed rate could notbe guaranteed by the DSD organization [4]. Meanwhile, a realcompetition for the available Polymer Materials can beobserved in this market sector. The most important processesfor the Chemical Recycling of Polymer Materials , which aboveall are processing Polymer wastes from the DSD-system, are in the order of the quantities utilized in 1995 [5] 1.


Related search queries