Carbotechnick Solid fuel dosing for PFR lime kilns
Carbotechnik as specialist in dosing and combustion of solid fuels gives the best know-how to all different types of lime kilns, e.g. the very efficient PFR kilns of QualiCal, in order to guarantee the best performance of the kiln and therefore best quality of the burnt lime stone.
As the kilns exist in a very wide range compared to the lime output and the number of fuel lances it is important to have a dosing system which is highly flexible compared to the maximum amount of pulverized fuel which must be transported to the kiln and of course also to the number of outlets / pipes which go inside the kiln. The Carbotechnik dosing system suits perfectly these requirements, as it is possible to have from 1 up to 26 outlets in one machine, or 20 kg/h up to 20 000 kg/h, depending on what the client needs. The machines are designed and dimensioned according to customer requirements. Only the diameter of the machine varies, a fact which keeps the planning work for the client from one project to another very simple and helps reducing costs already at a very early stage of the project.
For the end customer, the lime plants, short and rare maintenance cycles are important. The Carbotechnik dosing machine needs only 1 maintenance a year, duration 1–2 days, this is an availability of 99.5 %. It is absolutely tight and shock pressure resistant up to 10 bara, designed in accordance with ATEX directives, so no dust gets out and the highest level of safety according fire and explosion is assured, no ATEX zone around the machine is necessary.
For the PFR lime kilns an exact distribution over the kiln cross-section dimension is absolutely important in order to avoid baking in hotter zones. Another key figure is to provide a given amount of combustible constantly over a predefined cycle time. How can the Carbotechnik dosing machine guarantee this?
The machine body has normally diameters of 1.5 to 2.6 m where the pulverised combustible is fluidised and mixed. It then has the same density everywhere and assures by that an exact calculation of the volume/mass transported to each lance. Discs with more than 480 holes are in the middle of the pulverized combustible inside the dosing machine. The fluidisation makes the solid fuel behave like a fluid, it flows immediately in the holes of the disc once they are empty. 60 holes are filled and blown out with combustible every second for each lance, compared to a rotary valve with 3 pockets per second a vast benefit in accuracy and smooth combustion. This technique guarantees also best emission levels for the Carbotechnik burners (low NOx and CO), which are mainly used for direct drying or in fire tube boilers.
All these benefits help pushing lime kilns to its limits according cost efficiency and best lime quality, a formula chosen by many clients worldwide. As partners in the QualiPool QualiCal and Carbotechnik cooperate since 2006 and have installed already 10 new PFR kilns with solid fuel as main combustible worldwide successfully.