Digital Magazine

German company develops recovery concept for plastics

A German company has reported developments in the use of gasification in the chemical recycling of plastics waste.

According to Rheinbraun AG, Koln, Germany, the high-temperature Winkler (HTW) process represents a further development of the Winkler gasification principle. Solid feed stocks are gasified in a fluidized bed at elevated pressures of up to 30 bar using oxygen or air. As practical experience has shown, a great variety of feed stocks is suitable for the HTW process, including different types of coal, peat, biomass and wastes.

The company has made a lot of investigations on the use of the HTW process for the gasification of plastics at their 30-tons/hr., 10-bar gasification plant. Some 800 tons have been gasified so far. From September 1994, they have started with the continuous operation of up to 3 tons/hr., and engineering work is in progress to increase to 10 tons/hr.

Rheinbraun AG and RWE Entsorgung AG belong to RWE AG. The RWE Entsorgung 1992/1993 annual report states:

"Our activities for the recovery of old plastics are concentrated on industrial-scale processes for the recovery of raw materials and for the manufacturing of secondary products. Gasification is one of the process lines we're following. In it, mixed plastic fractions are converted into a synthesis gas under temperatures of approximately 1000 [degrees] C.

"In cooperation with ESPAG Energiewerke Schwarze Pumpe AG and the RWE Group Company Rheinbraun AG, we're studying the use of plants previously used for coal gasification. The development work in the field of hydriding of plastics, which we're performing in close cooperation with RWE-Gesselschaft fur Forschung und Entwicklung mbH, Wesseling, are concentrated on processes for liquification. With the help of this pretreatment stage, the use of old plastics in existing refineries should be made possible.

"Our affiliated company, Sicowa, has developed a further recovery concept for mixed plastics, whereby fine-grained filler materials suitable for use in construction material products are manufactured from old plastics. For the further development of the process and for marketing, we founded Proku Kunststoffveredelung GmbH, Essen, in January 1993. It's a joint company of RWE Ensorgung, Pro Mineral and Sicowa."

Methanol is produced in the Rhienbraun AG gasification plant and is used as a raw material for some chemicals.

* A British manufacturer of polyethylene films has recently moved into east polypropylene film production to serve hygiene, medical and food packaging markets.

Taco Holdings' films range in thickness from 15 to 250 microns and width up to 1,800 mm, supplied in reels to converters' requirements. This can call for multislitting of thin, 18-micron, soft and stretchy films to widths as narrow as 25 mm. It can also call for producing wider reels for packaging and technical applications from 30 to 250 micron.

Taco has installed a specially-built Dusenbery model 735 slitter with the new cast polypropylene line at Winsford, Cheshire, UK.

The slitter is customized to take 1,800 mm-wide mill rolls and is controlled by the latest Dusenbery touch screen. Instead of pressure-sensitive membranes overlaid on the monitor screen, the glass itself responds to a finger touch. The result is a brighter, clearer image and a more durable system.

The range of film thicknesses is achieved by specialized rewind tension controls and modular winding systems that will give hard or soft finished reels.

The specification even allows Taco to extend the range of polypropylene film thicknesses up to 600 microns and five layers of coextruded films. Its performance is central to plans to develop its technology into new products and wider markets, according to the company.

* A manufacturer from Molsheim, France, has introduced three bagmaking machines.

Holweg offers the RS-25 that can make over 300,000 bags in an 8-hr. shift. It has a simplified size changeover system, that's possible in 15 or 20 min.

The main feature of this machine is that all-sized parts for one bag size, such as the perforating tool and tube-forming parts, are preset off the machine.

The perforating tool is interchangeable like the plate cylinder in a flexographic printing press. The perforating blades are preset so it isn't necessary to make further adjustments when starting the machine. The tube is formed around a former plate that controls the web by using a vacuum to ensure it follows the exact shape of the plate.

The CP-28/TS machine has been designed for thermosealed bags with high thickness materials. The main applications are for microwave popcorn bags and chicken bags. The main feature is in the sealing drum allowing a very long sealing time with high-precision temperature control. The output of the machine is 200 bags/min. or 400 bags/min., depending on the length of the bags.

Holweg's IF-526 in-line flexo printer can reach speeds up to 300 m/min. It features 360 [degrees] length register and is driven by driving belts. All settings are on the operator's side, and sleeve stereos and doctor blades can be set with chamber.

* A Saudi Arabian thermoplastic-material manufacturer is currently producing 1.9-million tons of plastics materials.

In 1993, the project introducing 200,000 million tons annual capacity of polypropylene was started.

Sabic, Saudi Arabia, has become a manufacturer of high-density polyethylene, linear low-density polyethylene, polyvinyl chloride, polystyrene and polypropylene.

"I expect plastics demand to rise roughly 1.5 times as fast as the world economy," Abdullah S. Nojaidi, president of Sabic Marketing Ltd, said. "By 1994, linear low-density polyethylene will be growing 10.5% annually, with polypropylene growing at 6% per year. Conventional low-density polyethylene will rise less than 1% annually.

"New applications will pump up linear low-density polyethylene consumption," he said. "The easy-flow properties of Unipol 11 linear low-density polyethylene allows users to run it on equipment made to process conventional low-density polyethylene. This should speed linear low-density polyethylene penetration in Europe, where converts have stayed with low-density polyethylene rather than alter equipment.

Nojaidi predicted polyethylene demand will rise 4.4% annually overall between 1993 and 2003. "Like many other resins, widening global recycling will limit the growth of virgin polyethylene production." he said.

"Linear low-density polyethylene will lead the polyethylene parade, climbing 10.5% annually as it continues to chip away market share from conventional low-density polyethylene. High-density polyethylene demand will rise about 4.5% annually, while conventional low-density polyethylene will grow less than 1% per year.

"Compared with the polyolefins, polystyrene technology has remained little changed," Nojaidi said. "Overall, Sabic expects polystyrene demand to rise about 3.8% per year through 2003. Demand will be held down by environmental demands for wider polystyrene recycling.

"The demand for polyvinyl chloride will rise 5% annually through 2003. Towards the end of the decade, maturing Pacific Rim economies may begin to build their own chlorine and PVD-VCM-EDC facilities," he said. "Sabic sees an interesting year ahead with plastics markets and prices improving as demand begins to mop up the excess supply from 1995 onwards."

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