Clay raw materials for cement production
Clay raw materials are used to provide alumina and silica to the charge for the cement kiln and thus counterbalance too high content of CaCO3 in limestones and marls. The optimum content of CaCO3 in the kiln charge is 75-80%. When CaCO3 exceeds these values, various mineral additions are added to reduce its content at the advantage of SiO2, Al2O3 and Fe2O3.
Clay raw materials are qualified to the law raw materials group. According to the classification used in a cement industry: law raw materials contain <42% CaO (<75% CaCO3), normal raw materials contain 42-45% CaO (75-80% CaCO3) and high raw materials contain >45% CaO (>80% CaCO3).
The advancements in a development and current exploitation of these raw materials are relatively low. This is due to the two main factors: (1) attempts to achieve the optimum composition of mined major raw material (in this case – limestones and marls) and, in this way, to diminish the problems with its correction, usually made by the operators at the development stage, that is at the stage of works performed to open a mineral deposit for exploitation, and (2) a replacement of natural clay raw materials with mineral waste raw materials such as ash from heat and power plants, blast furnace slag and similar ones.
Lithologically the explored deposits of raw materials for the cement industry represent loams, clays, loesses and silts.
In 2017 anticipated economic resources of clay raw materials deposits for the cement industry increased by 0.402 million tonnes (0.1%) in comparison with 2016 and were reported to be equal 277.21 million tonnes (Table 1).
In 2017 there was a documentation of the natural aggregates deposit Lechówka approved where clay raw materials for the cement industry (clays and silts) are the co-occurring raw material. Within the deposit borders, except for new documented areas, there are also 6 already documented fields including 5 natural aggregates deposits with clay raw materials for the cement production: Lechówka dz.99, Lechówka dz. 102/1, 99, Lechówka dz.86, Lechówka dz. 104/1, Lechówka dz.97/1,101/1. For 4 of them (except for the last listed above) there were new documentations with settled resources elaborated and the deposits were crossed out from “The balance…”.
There was also Pawłów deposit crossed out from “The balance…” – as a result of a new documentation with settled resources approved in 2000 (the verification and harmonization process of the deposits information).
Deposits of clay raw materials for the cement production (together with building ceramics raw materials) are presented on the map.
The exploitation of deposits described in this chapter has been carrying out only in the Lubelskie Voivodeship area for the Chełm cement factory. In 2017 the output was recorded for Lechówka dz. 102/1, 99 and Lechówka dz. 104/1 deposits from which 0.007 million tonnes of raw materials were produced.
Moreover, for the cement production in the Chełm cement factory there were used about 0.057 million tonnes (0.029 million m3) of clayey raw material from Buśno deposit (Lubelskie Voivodeship). The raw material from Buśno deposit has been used for the cement kiln production since 2012, whereas the production of building ceramics was abandoned due to its unprofitability. The deposit is still placed in the chapter Building ceramics raw material – according to the way of raw material using described in the geological documentation.
The Kujawy cement plant also uses – as so-called “law raw material” – sands from Barcin-Piechcin-Pakość deposit (Kujawsko-Pomorskie Voivodeship), which is placed in the chapter Quartz sands for the production of the cellural concrete and lime-sand brick. The output amounted to about 0.069 mln tonnes (0.040 thousand m3) in 2017.
The figure below shows changes in resources and output of clay raw materials for cement production in Poland in the years 1989-2017.
Prepared by: Wojciech Szczygielski
Table 1. Clay raw materials for cement production - million tonnes