Clay raw materials for the glass and ceramic industries.
The “Surmin-Kaolin” SA Mineral Raw Materials Mines have been supplying clay raw materials to the ceramic industry for many years. A turning point in the company’s history came in 1956, when a decision was made to launch kaolin production in Poland. The related work began in 1957 with a geological survey of kaolin-bearing areas in Lower Silesia and the identification of three areas containing deposits. These were: the Wyszonowice-Sobótka area, with large reserves but kaolins containing a high level of impurities; the Świdnica area, comprising several residual kaolin deposits that were relatively pure but smaller and dispersed; and the Nowogrodziec area, comprising very large reserves of kaolin-bound sandstone in the form of old sedimentary deposits dating from the Upper Cretaceous, with the main Maria III deposit and several reserve deposits (Maria 1, Zofia, Czerwona Woda). The Maria III main deposit has documented 86 million Mg of kaolin raw material in industrial categories. The deposits were developed and construction of the first processing department was completed in 1963. At that time, a mining accident put the “Bolko” white-firing clay mine out of operation for an extended period. The ceramic industry was therefore deprived of its basic clay raw material from that mine. There was no other option. Part of the newly built plant had to be allocated to enriching the sorting waste accumulated at the mine and recovering white-firing clay from it. This was how Poland launched its first production of enriched clay, which proved to be an excellent ceramic raw material.
In 1972, a second processing department was launched, followed in 1974 by a then-modern drying and grinding installation. The plant achieved an annual production capacity of 50,000 Mg of enriched clay raw materials. A new period of development for the company began after 1989. Today, the plant is equipped to produce fourteen grades of kaolin, three grades of ceramic clay, and sands for the glass industry and construction.
In the near future, production of three new grades of kaolin and at least three new grades of enriched ceramic kaolin will begin. It is also expected that, as cooperation with domestic and foreign companies develops, production of various clay raw materials, higher-grade glass sands, and other highly processed raw materials for the glass and ceramic industries will expand intensively.
Kaolins for the ceramic industry
The main product manufactured for many years has been KOC kaolin in granulated form, with a moisture content of 14 + 2%. Its possible applications are limited. The production of sanitaryware now requires kaolin with a lower content of grains below 2 urn and characterized by faster build-up of the ceramic body on a plaster mold. KOCK kaolin meets these requirements. Its production technology is still being improved, particularly to obtain a smaller amount than before of material rejected by the 0.06 mm sieve, which carries most of the impurities. It is expected that in 1997 the amount rejected by the 0.06 mm sieve will be reduced to below 0.1%.
KOCK kaolin is also characterized by low green strength, amounting to 7 kG/cm2 for cast products. In some production technologies for ceramic wares and vitrified porcelain vessels, and in some cases also for ceramic tiles, these values are too low.
Plasticization produces KOCP kaolin, with green strength after drying of approximately 12 kG/cm2 in plastic forming and approximately 18 kG/cm2 in casting. This is a new grade currently being tested by customers. KOC kaolin is also characterized by a fairly high TiC2 content (0.6%) and an unfavorable Fe2C3 : Ti02 content ratio (1:1). Several years ago, FKW kaolin was introduced into continuous production; it is characterized primarily by high strength (30 kG/cm3). This kaolin is widely purchased by manufacturers of electrical porcelain and gres-type tiles. It contains a high level of coloring impurities (Fe2O3 : TiO2 at 1.0 : 1.1%), which limits its use in tableware porcelain production. More recently, an information series of Porcelanet kaolin was developed, offering high strength and good rheological properties; the amount of coloring impurities, Fe2O3 : TiO2, is 0.7% and can be reduced. In 1995, production began of kaolin with a low level of coloring impurities (particularly Fe2O3 – 0.4%), intended to stabilize ceramic glazes as an A1203 carrier. This kaolin is designated FPW/S.
High-quality, premium kaolins are expensive raw materials. The price barrier limits their use in small craft plants, so a range of inexpensive kaolins was introduced for such plants (three to five times cheaper than high-grade kaolins). MC, TK, and KS kaolins are also produced for customers who do not require very premium raw materials, and this range is expected to expand. The company will strive to produce kaolin grades at very low prices (around PLN 50/Mg at 1996 prices).
Other kaolins
In addition to ceramic kaolins, “Surmin-Kaolin” SA also produces kaolins for the polymer, paper, refractory-materials, and other industries. These kaolins can sometimes be used in ceramics. The most important are kaolins for polymers, as they are produced in a practically absolutely dry state, allowing precise weighing without any recalculation. This group includes KOM and KOG kaolins, as well as KOWS for glass-fiber production. FPW and FPB kaolins for the paper industry are characterized by low strength and an acidic reaction. However, they have significant ceramic advantages and are very easy to liquefy. With their properties suitably adjusted (pH – 7.8), these kaolins can form one of the components of ceramic bodies alongside other clay raw materials.
KOO kaolin, produced for the refractory-materials industry and for white cement production, is of interest to ceramists mainly because of its low price. When using this kaolin in ceramics, it should be borne in mind that it has unfavorable casting properties, particularly in winter. In every case where atypical kaolins are used in ceramics, their suitability should be tested very carefully.
Ceramic clays
The first ceramic clay produced in cooperation with the “Turów” Brown Coal Mine was TCI/W granulate. Comprehensive enrichment of clay from seam B at Turoszów and of processing products from the Maria III deposit made it possible to produce an inexpensive, good-quality white-firing ceramic raw material. The interesting properties of TCI/W granulate include the phenomenon of self-liquefaction, characteristic of Turoszów clays, while simultaneously retaining high whiteness after firing (80%). The most important factor, however, is the inexpensive production technology.
TC/W granulate was received very cautiously by customers, and its production is developing slowly. To this day, there are plants that do not want to or cannot use it in production.
Following TC1/W, a dolomitized variant, TCl/WD, intended for manufacturing wall tiles by the single-firing method, was launched in cooperation with the Jeleniogórskie Mineral Raw Materials Mines.
The third grade of ceramic clay, produced in cooperation with the Strzeblowskie Mineral Raw Materials Mines, is a completely sintering stoneware-type clay, TrM. It is currently being introduced for the production of floor tiles and building exterior coverings (facade tiles).
Sands and raw materials for the glass industry
The most important raw material supplied by “Surmin-Kaolin” SA to the glass industry is KOWS kaolin, which is an AI2O3 carrier. So far, it has only been used in the production of glass fiber. Economic conditions and the need to make maximum use of the mined material extracted from the mine have also led to interest in sand production. The “Surmin-Kaolin” company currently produces industrial sands. It also produces so-called aleurite, a fine-grained mixture of sand and kaolin intended for white cement production.
Recently, interest in sands has increased. Laboratory tests have produced class II glass sands according to the applicable standards, as well as sands approaching class Ia.
The development of glass-sand production is therefore planned in cooperation with the German company “Quarzwerke” and the glass-sand production plant in Osiecznica, along with the development of production and improvement of the quality of ceramic, construction, and aleurite sands.
Development plans
The “Surmin-Kaolin” SA Mineral Raw Materials Mines plan to expand the range of raw materials produced for the ceramic industry and other customers. We will improve the production of Porcelanet kaolin and reduce its impurity level. We also plan to produce ground, high-whiteness Bielfarb kaolin (whiteness 81 +- 1%) for the paints and coatings industry.
Inexpensive ceramic kaolins will be produced. At present, trial batches of Syriusz kaolin with good casting properties but a fairly high amount of material rejected by the 0.06 mm sieve (5 ? 2%), with a downward trend, are being supplied.
We intend to introduce new grades of enriched ceramic clays to the market: mechanically sorted Turoszów clay TGS, already in 1989, and soon TSC – ceramic clay and TGO – refractory clay. Intensive work is underway to develop technology for producing inexpensive enriched ceramic clays.
Kazimierz Marczewski
Zbigniew Muzal
Andrzej Pytliński