13.) On (1) Cryogenic plastic recycling / Kryo- Recycling

On (1) Cryogenic plastic recycling / Kryo- Recycling

http://en.wikipedia.org/wiki/Recycling

With the deep temperatures of the cryogenic recycling process ( down to -160°C) the mainly thermoplastic synthetic materials (more than 90% of the plastics used ( http://en.wikipedia.org/wiki/Plastic )) and elastomere ( http://en.wikipedia.org/wiki/Elastomer ) ( rubber products) are made brittle. They then easily can be ground to fine powder. Pulverizing ( http://en.wikipedia.org/wiki/Pulverizing ) makes fine sorting possible. Especially the fine pulverizing permits separating the plastic grains of the intact original mass, the inner part of the plastic products, from the grains of the altered surface layer. The grains of the intact original mass make real recyclates. The altered grains of the surface layer make material for downcycling ( http://en.wikipedia.org/wiki/Downcycling ).

The cryogenic recycling process / kryo recycling already has been extensively prepared ( 1 )( 31 )( 54 )( 55 ). It was not only tested on a laboratory scale, but also examined, found to be good, and shaped by specialists for refrigration technology and mechanical process and sorting technology and by industrial engineers. Mannesmann Anlagenbau AG (plant engineering) ( http://en.wikipedia.org/wiki/Mannesmann ) had been colaborating on it for more than 2 years until the cooperation was abruptly stopped due to the takeover of the corporation by Voadfone ( http://en.wikipedia.org/wiki/Vodafone ).

3 innovative process stages considerably reduce the previous operating costs for deep refigeration technology, crushing technology and sorting, so that the marketability of the plastic recyclates, as regards both price an quality, has been economically reviewed and can be predicted as certain.

* The new low- temperature refrigeration technology

http://en.wikipedia.org/wiki/Refrigeration

The new low- temperature refrigeration technology uses three natural gas fefrigiants

propane ( http://en.wikipedia.org/wiki/Propane ) +

ethane ( http://en.wikipedia.org/wiki/Ethane ) +

methane ( http://en.wikipedia.org/wiki/Methane

not in separate cycles, as in the conventional cascade technique, but as a mixture in a one- cycle system, as in the eco refrigerator "Greenfreeze". (In the book you will find a graphical picture of the sytem).

The main compressor ( http://en.wikipedia.org/wiki/Compressor ) only has to develop a pressure of 15 bar ( http://en.wikipedia.org/wiki/Bar_%28unit%29 ) to liquefy propane. the cascade like fall in temperature occurs without additional power consumption by fractional vaporizing of the refrigerant in a shunt circulit. The methane vaporaizing at -161°C, cools the grinding tunnel into which the scrap plastics, used tires or electronic parts, crushed into palm- sized pieces beforehand, are brought via a sluice. To utilize the vaporization enthalpy ( http://en.wikipedia.org/wiki/Enthalpy ) of the gases in the best possible way, they are returned to each particular preliminary stage according to the counterflow principle, which is only roughly outlined in Figure 10 (in the book). As a mixture they again reach the main compressor via Roots- type precompressor ( http://en.wikipedia.org/wiki/Roots_type_supercharger ) with a technically favorable high suction gas temperature.

To enable a compact construction of the grinding tunnel, the indirect cascade cooling of the grist is complemented by direct cooling according to the heat- pipe principle ( http://en.wikipedia.org/wiki/Heat_pipe ) in the tunnel. The latter increases the heat transition and provides for direct continuous frictional heat removal from the grist ( http://en.wikipedia.org/wiki/Friction ). Compared to the old Cryogen- recycling with liquid nitrogen ( http://en.wikipedia.org/wiki/Liquid_nitrogen ), the opening costs go down to approximately a tenth. The cost advantage considerably extends the range of economic applications.

The advantage of the hydrocarbon mixtures ( http://en.wikipedia.org/wiki/Hydrocarbon ) in the cooling cycle ( http://en.wikipedia.org/wiki/Cooling_cycle ) results from the tendency of gases to establish van der Waals interactions in mixtures ( http://en.wikipedia.org/wiki/Van_der_Waals_interaction ). These week bonding forces contribute to the formation of "molecule clusters" ( http://en.wikipedia.org/wiki/Molecule_cluster ) during condensation ( http://en.wikipedia.org/wiki/Condensation ), thus vaporization enthalpy. Overcoming the mixture- included van der Waals forces increases the volumetric refrigeration capacity and the energetic refigeration gain. These physical- chemical principles of innovative refrigation technology were presented and successfully defended by Prof. Rosin with the help of IP- spectroscopic analyses in 2 lectures at the University of Göttingen and before the VDI and VDE at Göttingen ( 54 )( 55 ).

The innovative refrigeration technology also passed the tests conductetd by industrial refrigeration engineers. in the mid- 1990s it was discussed in detail with refrigeration engineers of the company "Messer" (in Griesheim and Krefeld) and considered to be good. They would have liked to take part in the industrial realization if the mother company at taht time, Hoechst ( http://en.wikipedia.org/wiki/Hoechst / www.messer-group.com ) had allowed them to change from liquid nitrogen to the hydrocarbon mixtures. The cost advantages compared to conventional refigeration technology in the low- temperature field using liquid nitrogen were confrimed inter alia in feasibility studies ( 1 )( 31 ).

* The new grinding technology

The new grinding technology in the refogeration tunnel: The material, which is not shock- frozen but is gradually embritted, is caught between the central working rolls, which only partially project into the compact tunnel (in the book in figure 11 ).

The grinding pressure ( http://en.wikipedia.org/wiki/Grinding ) is reinforced by external supporting rollers. The roling mill ( http://en.wikipedia.org/wiki/Mill ) is simillar to the sendzimir mill proven in metallurgy and cement industry ( http://en.wikipedia.org/wiki/Metalurgy ). The roll guide, however, reacts flexibly to disturbing lumps or in case the grist ( http://en.wikipedia.org/wiki/Grist ) builds up in front of the roll gap. The desired grain size ( http://en.wikipedia.org/wiki/Grain_size ) can be adjusted variably - if required up to the finess of powder ( http://en.wikipedia.org/wiki/Powder ). Tire producers demand a grain size of less than 80 micrometers for rubber recyclates ( http://en.wikipedia.org/wiki/Tire ). It could be proven in electron- optical analyses that with the innovative grinding technology grinding down to a size of 20 micrometers is possible, if required - with the particle surface remaining rough and active, i.e., not being smoothed by friction heat ( http://en.wikipedia.org/wiki/Friction ).

Contraries like attached dirt or heavy substances like metal and minerals are removed parallel to the grinding process by air separation or sieves ( http://en.wikipedia.org/wiki/sieve ). the medium for direct cooling according to the heat- pipe principle ( http://en.wikipedia.org/wiki/Heat_pipe ) protects against dust explosions ( http://en.wikipedia.org/wiki/Dust_explosion ), e.g., during the fine grinding of used tires. It also prevents the secondary oxidation of the polymer chains at the intercrystaline breaking points. The flotation of the mixed powder at the end of the grinding process is guaranteed by special pin mills.

In principle the mechanical process engineering follows the good example set by Messer- Griesheim ( www.messergroup.com ) with its offers to recycling using liquid nitrogen: "On- line classifying with high flow rate and sharp separation boundaries up to the micrometer level" (Messer- Griesheim brochure).

The advantages of the innovative cryogenic recycling / kryo- recycling: it does without relatively expensive liquid nitrogen ( http://en.wikipedia.org/wiki/Liquid_nitrogen ) and offers the cost advantage of natural gas hydrocarbon mixtures, which can be used to optimum efficiency in the closed refrigant loop. The price advantages were professionally proved ( 1)( 31 ). For plastic processors and producers of tires and other technical rubber products, e.g., conveyer belts, sealing material and so forth, the success on the market can be regarded as assured - at the latest since the price for crude oil rose to mor than 100 dollars per barrel ( like in Summer 2008). (Also, incineration is not for free! It would be enough, if this technique would made working with a lower price than the WIPs, by regarding also the external costs. F. St.) http://en.wikipedia.org/wiki/Peak_oil

* The new separation and sorting technology

http://en.wikipedia.org/wiki/Separation

http://en.wikipedia.org/wiki/Sorting

www.spectro.de/pages/e/index.htm

The new separation and sorting technology: The different separation and sorting processes connected in series via conveyer belts, already start in the refrigeration tunnel. In the refrigeration tunnel, for example, advantage is taken of the fact that the well known electrostatic separation according to the ESTA process is not impaired by conductive water. Further methods partly correspond to the highly developed state of the art, e.g., the Messer Griesheim Cryoclass process. Additional innovativ processes improve the fine sorting of the mixed powder, which contains numerous types of material. A highly unmixed result, also sorted according to color, and very gentle treatment of the material preserving the active surface of the grain are possible.

The fine grinding makes it possible to separate the grains from the surface of the pastics parts, which often is changed and worn out, from the grains which still consist of completely intact base mass. Even after many years of use, the waste plastics only used up right at the surface, as a rule. 60 to 80% intact base mass remain which can be recompounded ( http://en.wikipedia.org/wiki/Compound ) using the well- developed methods of the state- of- art chemical technology. Suitable aditive mixtures for recompounding can be obtained from Ciba Spezialitätenchemie ( www.ciba.com ), if necessary ( 50 ). It has been demonstrated that the recompounding of recyclates can produce plastics of primary quality or with even better mechanical properties ( 62 ) - except that the products from recyclates are much cheaper for plastics processors because cryogenic recycling/ kryo recycling uses about 40 times less energy than the synthesis of new molding material.

* Outlook on kryo- recycling

A group of scientists and engineers who took the forecasts of a destructive climate change ( http://en.wikipedia.org/wiki/Climate_change ) and other damagings of the biosphere seriously at an early stage extensively prepared the cryogenic recycling/ kryo- recycling process decentrally for industrial use. In qualitative respects the results are encouragging. It has been proved that scrap plastics can be further processed into new high- quality products. Their incineration - often only after a single use - is not necessary. Even the grain from the surface layers, which often is changed by imprints or wear and tear, can be put to good use, for example , as material for protecting car underbodies against corrosion. This is more a downcycling ( http://en.wikipedia.org/wiki/Downcycling ) than a recycling ( http://en.wikipedia.org/wiki/Recycling ), but still a usefull further application of the material. The many disadvantages of the waste incineration plants (WIPs) - high termal emissions, high rate of conversion into toxins in slag, dust or flue gas - can be avoided. For the low temperatures, the use-friendly original material compostion of the products is not changed at all. And no new toxin emerge.

It is now time to embody the ( in 2008) 12- year development phase in an industrial pilot plant and optimize it. The pilot plant as well as future operating facilities with a capacity of one ton per hour or more and an eight hour working day can operate economically. The plant size should not exceed a capacity of five tons per hour so that the transport distances remain short.

As long, as the WIP lobby continues to pursue its inglorious goals, cryognic recycling/ kryo recycling unfortunately has only few prospects in this power game, because the scrap plastics cannot be obtained as long as politics and/ or economics do not permit let alone support this. (Politics only have power, because they are electetd. If they are not willing to beginn the kryo- recycling, we, the electors, should change the persons, which now have the chance, to do the best for the people. F.St. www.world-ecological-parties.org )

And yet is certainly that the advantages terms of the enrgy balance and costs will pay off:

**for our national economys, because plant engineering and plastics processing stay here - despite globalization - and do not have to relocate to low- wage countries;

**for the employed and unemployed, because the cost advantage will be obtained by technical means and with their good know- how and not merely through wage dumping;

**for the plastic producers, because on the one hand they can contribute their processing, knowledge to the reyclate buisiness/ quality assurance and, on the other hand, will likely able to sell even better, more expansive high- tech products with the offer of recycling on the world market.

The total amount of wastes that could be treated by cryogenic recycling / kryo- recycling comes to about 20 million tons per year in Germany. this corresponds to the decrease in German coal output from 47 million tons in 1997 to 26 million tons 2008. The value created from the high- quality waste would be plainly higher than that from coal mining. The number of jobs which would finance themselves through the conervation of material would be enormous!

( 1 ) Albrecht, M.; Grundlegende Berechnung einer Kältekaskade zur Tieftemperaturaufbereitung von kunststoffhaltigen Rückständen. Diploma thesis, Düsseldorf, University of Applied Sciences (1996) www.fh-duesseldorf.de

( 31 ) Hinrichs, H.F., S. Harig, H. Schütz: Durchführung einer Vorstudie über das Tieftemperaturverfahren zur Verwertung von Altreifen. KTB, Oberhausen and EKKU, Marl (1994)

( 50 ) Pfaender, R., H. Herbst, K. Hoffmann: Innovative Concept for the Upgrading of Recyclates by Restabilization and Repair Molecules. Macromolecular Symposium 97-111 (1998)

( 54 ) Rosin, H.: Chancen, die aus der Kälte kommen. Lecture: VDI, VDE zu Göttingen, Göttingen ( 19 feb. 1998)

http://de.wikipedia.org/wiki/Harry_Rosin / http://en.wikipedia.org/wiki/Harry_Rosin

( 55 ) Rosin, H.: Der Schlüssel zur globalen Kreislaufwirtschaft. Lecture: GDCh, VDI, VDE und Göttinger Colloquium für Fragen der Wissenschaft, technik und ethik, Göttingen (30 Nov. 2000)

( 62 ) Scott, G.: Polymers and Environment. RSC (1999)

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