| Abstract [eng] |
During Master's thesis project, the hemihydrate production process of phosphoric acid was modernised. A hemi-dihydrate phosphoric acid production process, which produces phosphoric acid with a higher concentration and a lower impurity content was designed. The production yield of phosphorus pentoxide increases from 95.8 % to 98.9 %. The quantity of the final product is higher with the same amount of raw materials. Phosphoric acid is the main raw material for mineral fertilisers. So far, no substitute for mineral fertilizer has been produced to meet the market demand. As phosphate rock resources are limited, it is important to use them as efficiently as possible. As the demand for fertilisers grows, it is useful not only to improve fertilizer production processes and look for substitutes for mineral fertilisers, but also to pay more attention to the research on fertilizer raw materials. Phosphate rocks from Kirov, Covdor, Morocco-Casablanca and South Africa have been studied for more efficient and cleaner phosphoric acid production. The mass fraction of phosphorus pentoxide in the rocks ranged from 32.3 % to 38.8 %. The phosphate rock from Covdor was selected for the project. The rock was found to contain 36.6 % mass fraction of phosphorus pentoxide, the lowest impurity content, and the finest particle fraction. Considering that the phosphogypsum produced by the phosphoric acid semi-dihydrate process is cleaner, drier and has better processing properties it is more suitable for reuse. The amount of recycled phosphogypsum is expected to increase and the landfill area to decrease. The estimated cost of the project for the modernisation of the phosphoric acid production equipment is EUR 17.8 million. The theoretical savings of EUR 4.7 million per year due to the reduction in phosphate rock consumption and the increase in production yield were estimated, and the project would pay for itself in 3.8 years. In contrast, when the mass fraction of phosphorus pentoxide in the phosphate rock and energy costs are taken into account, the annual savings are reduced to EUR 3.8 million. Therefore, the payback period is extended to 4.7 years. This project is not only viable because of the higher quality phosphoric acid and more efficient use of raw materials. After 4.7 years, the project is expected to add EUR 3.8 million annually to the company's budget. This money is intended to be used for modernisation of the company and improvement of the quality control department, thus making the work of the departments more efficient, and eliminating human error. The thesis consists of 51 pages, 13 figures, 18 tables and 36 references cited to illustrate it. |
