Adjusting the melting and crystallization behaviors of ferronickel slag via partially replacing of SiO2 by B2O3 for mineral wool production.

Utilization of ferronickel slag as a raw material for mineral wool production not only conserves natural resources, but also achieves the sustainable development for the ferronickel industry. In order to utilize the ferronickel slag more efficiently, the melting and crystallization behaviors of the slag with the partial replacement of SiO2 by B2O3 were investigated in this paper. The results show that the initial and complete melting temperatures decreased with B2O3 substitution for SiO2, which indicates that the addition of B2O3 can reduce the energy consumption during the melting process. The incubation time of the slag in the Time Temperature Transformation (TTT) diagram increased, whereas the initial crystallization temperature in the Continuous Cooling Transformation (CCT) diagram decreased when SiO2 was substituted by B2O3. In addition, the main crystalline phases precipitated in the slags were columnar MgSiO3 and Mg2SiO4. The weakening of crystallization ability caused by the substitution of B2O3 for SiO2 will be beneficial for the improvement of fiber quality when the ferronickel slag is used as a raw material for mineral wool production.

Evaluation of particle penetration factors based on indoor PM2.5 removal by an air cleaner.

The particle penetration factor is an important parameter to determine the concentration of indoor particles. In this paper, a mathematical model for calculating this parameter was established by combining with the decay of the indoor PM2.5 and CO2 concentrations measured in a bedroom with an air cleaner. The convergence of the penetration factors was analyzed under different working conditions. The results show that the particle penetration factors converge to stable values within the range of 0.69 to 0.84 close to the value from the empirical formula when the indoor PM2.5 concentration decays to stable values. When the role of particle deposition is ignored, the penetration factors at the low and middle airflow modes are 0.78 and 0.69, respectively. The particle penetration factors are mainly determined by the clean air delivery rate (CADR) of the air cleaner, clearance airflow, and I/O ratio during the balanced phase when the roles of indoor particle deposition and exfiltration can be ignored. This work can provide a convenient method for the calculation of the particle penetration factor.

Study on the durability of concrete with FNS fine aggregate.

As a by-product of nickel production, the ferronickel slag (FNS) puts a lot of pressure on the environment. It is becoming more and more urgent to deal with the increasing FNS. The aim of this study is to explore the durability of concrete with FNS fine aggregate. Two kinds of FNS with different storage time were selected. The radioactivity detection, XRD test and stability detection of FNS were conducted to ensure FNS can be used as construction materials. Then the durability of concrete with 13%, 27%, 40% and 50% FNS (by weight of fine aggregate) was investigated, respectively. It was found that the properties of concrete prepared from FNS with different storage time had little difference. The results indicated that 27% FNS replacement showed improvement in resistance to sulfate attack by 22% but the resistance to chloride ion penetration was not significantly influenced. Moreover, 40% FNS addition brought a 33% abrasion reduction than that of original concrete. SEM analysis showed that FNS produced more C-S-H gels and improved the microstructure of concrete. This study indicated that proper content of FNS can be used as fine aggregate and it was beneficial to the durability of concrete, especially to the abrasion resistance.

Selective recovery of chromium from ferronickel slag via alkaline roasting followed by water leaching.

Chromium was selectively recovered from ferronickel slag by roasting the slag with addition of Na2O2, followed by water leaching. The thermodynamic analysis revealed that in the presence of Na2O2 at appropriate temperatures, the Cr2O3 in the ferronickel slag can be converted to NaCrO2, instead of Na2CrO4, which prevents the formation of highly toxic Cr (VI). The experimental results confirmed that under the optimal alkaline roasting and water leaching conditions of the mass ratio of ferronickel slag to Na2O2 of 1, roasting temperature of 600 °C, roasting time of 1 h, leaching temperature of 50 °C, leaching time of 1 h, and liquid-to-solid ratio of 10 mL/g, 92.33% of Cr was leached with 64.28% of Na and 11.16% of Si and only 0.06 wt % Cr was left in the leaching residue. The high leaching percentage of Cr was a result of the transformation of Cr2O3 in the ferronickel slag to NaCrO2 with a loose structure during alkaline roasting that was beneficial to water dissolution. Compared to the traditional alkaline roasting process, the proposed more environmentally friendly method did not produce toxic Cr (VI) during recovery of chromium and the resulting residue has potential to be used as a good construction material.

Two new species of Verruconis from Hainan, China.

Two new species of the genus Verruconis, V.hainanensis and V.pseudotricladiata, were described using combined morphological and DNA sequence data. The DNA sequences of respective strains including nuclear ribosomal DNA genes (nuSSU, ITS, nuLSU) and fragments of three protein-coding genes (ACT1, BT2, TEF1) were sequenced and compared with those from closely-related species to genera Ochroconis and Verruconis (Family Sympoventuriaceae, Order Venturiales). Morphologically, both species showed typical ampulliform conidiophores and conidiogenous cells, features not seen in other species of Verruconis. The conidia of V.hainanensis are fusiform and those of V.pseudotricladiata are Y or T shaped, similar to old members of a closely-related genus Scolecobasidium. The addition of these two new species provides a new perspective on the heterogeneity of Scolecobasidium.