Sustainable and Clean Utilization of Yellow Phosphorus Slag (YPS): Activation and Preparation of Granular Rice Fertilizer

Abstract

Yellow phosphorus slag (YPS) is a typical industrial solid waste, while it contains abundant silicon micronutrient required for the growth of rice. The key scientific problem to use the YPS as rice fertilizer is how to activate the slag efficiently during the phosphorite reduction smelting process. In this work, an alkaline rice fertilizer from the activated YPS was successfully prepared to use the micronutrients. Thermodynamic analyses of SiO2-CaO, SiO2-CaO-Al2O3, and SiO2-CaO-Al2O3-MgO systems were discussed to optimize the acidity for reduction smelting. Results showed that the reduction smelting followed by the water quenching process can realize the reduction of phosphorite and activation of YPS synchronously. Ternary acidity m(SiO2)/(m(CaO) + m(MgO)) of 0.92 is suitable for the reduction smelting and activation of the slag. After smelting, the molten YPS can be effectively activated by water quenching, and 78.28% P, 90.03% Ca, and 77.12% Si in the YPS are activated, which can be readily absorbed by the rice roots. Finally, high-strength granular rice fertilizers with a particle size of Φ2–4 mm were successfully prepared from the powdery nitrogen-phosphorus-potassium (NPK) and activated YPS mixture.

Processing of phosphorites with extraction of phosphorus, obtaining calcium carbide and ferroalloy

“…The confidence limit, which is used for determination of the adequacy of the regression equations, in our case is 95%, i.e. the calculation error is no more than 5% (Inkov et al, 2003).…”

“…After determining the capacity, the CaC2 concentration in the calcium carbide was found using the transformed equation (Inkov et al, 2003).…”

“…The slag is a waste product (46-50% of CaO,.0% of Р2O5, 2-3% of CaF2); it is stored in dumps, occupies land, and worsens the ecology of the region due to the dust formation (Bazhirov et al, 1998). There are some methods for processing phosphorus-containing slags and using them for the production of fertilizers (Hou et al, 2021), brick (Kovkov et al, 2009), silicon dioxide (Bochevskaya et al, 2019), cement (Suleimenov et al, 1980), and concrete products (Khudyakova et al, 2009). However, phosphorus slag has a limited demand in the construction industry due to the fact that it contains P2O5 (up to 3%), which forms a poisonous gas -phosphine -in a humid medium (Bazhirov et al, 1998).…”

“…There is a liquid-phase reduction of phosphorus, its transition to the gas phase and oxidation to P2O5. In addition to these new processes (Suleimenov et al, 1980;Kovkov et al, 2009;Khudyakova et al, 2009;Bochevskaya et al, 2019;Hou et al, 2021), a method was described for using shungite during the phosphorites' electric smelting, which, due to the presence of carbon and silicon dioxide, makes it possible to replace some of the coke and quartzite (Konevsky et al, 1974).…”

Transition of Phosphorus Into Ferrophosphorus and Fluorine Into Gaseous Calcium Fluorides During the Production of Ferroalloy, Calcium Carbide and Phosphorus From Phosphorite

“…т фосфора. Стабильному развитию фосфорной электротермии в Казах-стане в значительной степени способствует наличие двух фосфоритоносных бассейнов: Каратауского и Актюбинского, с балансовыми запасами 483 млн т по Р 2 О 5 [2]. Фосфор из фосфоритов производится в электропечах при температуре 1400-1500 0 С.…”