Abstrakt: The dissertation focus on issues concerning phosphorus recovery from alternative sources. This problem is highly up-to-date because of the scarcity of phosphate raw materials and its prices rise. The subject ... więcejThe dissertation focus on issues concerning phosphorus recovery from alternative sources. This problem is highly up-to-date because of the scarcity of phosphate raw materials and its prices rise. The subject of the experiments were mineral remains from thermal utilization of sewage sludge ash. The materials from seven of the eleven Polish thermal utilization plants were characterized taking into account possibility of its utilization as an alternative phosphorus source.
Extractions of the phosphate compounds from the sewage sludge ash (SSA) with nitric and phosphoric acid were conducted in the laboratory scale. As a result, the best materials were chosen for the next stage of the experiment, that was conducted in the great-laboratory scale.
In the great-laboratory scale it was tested what is the influence of the solid residue washing procedure, concentration of phosphoric acid and cooling of the system on the extraction efficiency.
The experiment of in-process recycling was conducted as well. The modifications of the procedure were applied in the subsequent step where the extractions of the selected SSA were conducted in the microtechnical scale in the reactor of 50 liters volume.
The extracts that were obtained in the extraction step were neutralized in order to obtain fertilizers in the form of precipitate CaHPO4•2H2O and ammonium phosphates. The properties of the products were analyzed in the term of their usage as valuable fertilizer products.
The final part of the work was the two-step phosphorus recovery process conducted in the microtechnical scale with in-process recycling. |