Clay raw materials for cement production
Clay raw materials are used for the production of the cement clinker as a supplement adjusting of a kiln input. The basic compound of a kiln input are carbonate rocks: limestones and marls. The optimum content of CaCO3 in a raw material for the clinker baking is 75-80%. In the case when the composition of the basic raw material differs from these values, various mineral additions are used. Clay raw materials reduce the CaCO3 content and increase the content of SiO2, Al2O3 and Fe2O3.
According to the classification used in a cement industry, clay raw materials are qualified to the law raw materials group. 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 the clay raw materials for cement production are relatively low. This is due to the two main factors: (1) at the stage of the documentation and exploitation of deposits of raw materials for cement industry the aim is to optimize the composition of raw material which reduces the necessity of the composition correction; (2) as a law raw material there are often waste raw materials used: the dust, the ashes, the blust furnace slag and others – they replace the natural raw materials.
Lithologically the explored deposits of raw materials for the cement industry represent mainly clays and clayslates, but also loams, loesses and silts.
Anticipated economic resources of clay raw materials deposits for the cement production as of the edn of 2018 amount to 279.641 million tonnes. They increased by 2.429 million tonnes (0.9%) in comparison with 2017 (Table 1).
In 2018 there was a new documentation with recalculated resources approved for a loessal loams deposit Buśno (2.543 million tonnes) designed for the cement production. There were previous borders of this deposit extended and the resources within the exploitation area updated. Till 2017 the resources of Buśno deposit were recorded in the chapter Building ceramics raw materials, however since 2012 the raw material from this deposit has been used for the production of cement clinker and the production of bricks has been suspended. On the basis of the decision approving the new documentation there was Lechówka dz.97/1,101/1 deposit crossed out from “The balance…” as the deposit area and its resources have been included into natural aggregates Lechówka deposit where the raw materials for the cement production are the accompanying raw material.
Deposits of clay raw materials for the cement production (together with building ceramics raw materials) are presented on the map.
There were 2 deposits in Lubelskie Voivodeship exploited in 2018: Buśno and Lechówka for the cement plant Chełm. The output amounted to 0.114 million tonnes. The output volume increased twofold in comparison with 2017. For the cement production in the cement plant Kujawy, as a low raw material, are quartz sands from Barcin-Piechcin-Pakość deposit (Kujawsko-Pomorskie Voivodeship) used – they are recorded in the chapter “Quartz sands for production of cellular concrete and lime-sand brick”. The output of these sands was equal about 0.143 million tonnes in 2018, being at least twice bigger than in 2017 (about 0.069 million tonnes; 0.040 million m3).
The figure below shows changes in resources and output of clay raw materials for cement production in Poland in the years 1989-2018.
Prepared by: Wojciech Szczygielski