Dirk cenospheres – a natural dimension to materials engineering

Citation

(2003), "Dirk cenospheres – a natural dimension to materials engineering", Pigment & Resin Technology, Vol. 32 No. 1. https://doi.org/10.1108/prt.2003.12932aaf.002

Dirk cenospheres – a natural dimension to materials engineering

Dirk cenospheres – a natural dimension to materials engineering

Keywords: Materials, Engineering, Cenospheres

To design composite materials which expand the present capabilities of materials engineers and which also uses recycled waste products is the holy grail of today’s society. Where waste products were once seen as exactly that, perception is changing. From, how can I incorporate waste or recycled products into a compound for cost saving production, to how can these materials be used to enhance a composite product? Or to take it a step further, how can the unique characteristics of the recycled product influence materials engineering design in the future?

Cenospheres, a by-product of coal fired power stations, have the unique characteristics necessary to enable materials engineers, using novel manufacturing techniques, to create advanced materials within the various industries of plastics, ceramics, construction, automotive, energy and technology. They are believed to be an excellent replacement for other fillers such as glass spheres, calcium carbonate, clays, talc and other silica.

Versatile in application

The most intriguing properties of cenospheres, arising from their hollow structure, are their low density and low thermal and acoustic conductivities coupled with chemical inertness and high compressive strength, which results in a material which has a range of properties that translate to an extremely versatile material, suitable for a wide variety of applications.

Typical applications are said to include use in refractories, PVC flooring, oil well cements, mouldings, brakepads, phenolic resins, sound, thermal and fire retardant paints and coatings, epoxy resins, synthetic marbles, grouts, ultra lightweight ceramic tiles and body fillers.

Additionally they are a major component within low density cements, oil well drilling muds, gypsum board joint compounds and automotive sound dampening sheets. In fact cenospheres are such a unique product that they are said to be used in totally opposing situations such as a lubricant and an abrasive!

Created in the process of energy production where pulverised coal material is burnt, the vapourised inorganic material within the coal solidifies on leaving the furnace when it cools to form flyash, which is the term used to describe the inorganic solids which are prevented from exiting the power station via its chimneys by electrostatic precipitators.

Flyash is composed of chemically similar materials but one component, cenospheres, is present at around 1 per cent and claims this range of extraordinary properties.

The Dirk Group of companies, report that they have, by utilising their extensive expertise in recycling, and investing heavily in the processing facilities and infrastructure needed to process these materials, produced a high quality cenosphere product, “tecfil” a high grade, quality controlled material (Plate 1).

Plate 1 The Dirk Group of companies produced a high quality cenosphere product “tecfil” to fulfill the world-wide demands of customers and end users alike for a high grade quality material at the Nasik Plant

Production of a high grade material

At the purpose-built plant in Eklahare, India, local workers work to European standards to produce bulk quantities of IS019001 classified “tecfil” at a minimum rate of 600 tonnes per month, which will increase to 1,400 tonnes when the new Dirk plant is fully operational. Cenospheres for the “tecfil” product come from other Indian power stations to ensure a constant supply and eliminate the boom and bust production cycles often associated with production of this type of product which can impact on end user production output. Produced at a consistent rate throughout the year, eliminating seasonal variances the harvested cenospheres undergo a rigorous testing regime before they are uploaded and prepared for processing. If they do not pass the extensive quality control tests then they are rejected to ensure that the high quality of the “tecfil” product, on which the Dirk company has built it’s reputation, is maintained.

Product profile – tecfil

Cenospheres from different sources typically vary in colour and whilst this does not reflect any difference in chemical or physical properties it may be preferable for specific applications to use a single best match coloured product, which Dirk are able to supply on customers request. Cenospheres for “tecfil” vary from off-white (75 per cent) to light/medium grey (15 per cent) to dark grey (10 per cent) and are in most circumstances blended together to give a uniform colour after drying and screening.

The materials are sieved to both standard grades, namely Dirk tecfil T-150 and T-300, (where the numbers refer to the grade classification in microns) and contain a low inherent sinker volume of less than 2 per cent which characterises a consistently performing material.

The material is constantly sampled and quality tested within the Dirk laboratory to ensure that the end product meets the IS09001 standard, prior to packing.

Dirk reports that they have worked closely with many customers to develop, alongside tecfil, a progressive and expanding network of academics and industrial contacts spanning many technical fields including rubber, plastics, resins, abrasives, cementing and construction to advise on the uses of tecfil and also work with materials/design engineers in partnership to develop advanced materials which push back the boundaries of materials science.

Details available from Dirk European Holdings Ltd. Tel: +44 (0)151 608 8552; Fax: +44 (0) 151 608 7579; E-mail: gdirk@dirkgroup.com; Web site: www.dirkgroup.com