Search

Green liquor dregs (GLD) are a major waste of the pulp and paper industry, and their correct classification is important to finding alternatives to landfill disposal. In the European Union, the met...

Waste lubricant oil (WLO) is an absolute hazardous entry in the European List of Waste that requires proper treatment. Solvent extraction is one of the most effective deasphalting processes for the regeneration of WLO, with a strong contribution to the circular economy. This study aims to propose a new methodology for the selection of solvents for WLO regeneration, which balances technical, economical, and greenness criteria. The method involves two phases for screening a list of 154 solvents. In the first phase, five criteria were used: water and acidic properties; selectivity toward the base oil and flocculation capacity; number of carbon atoms between three and five; melting point lower than 10 °C and a boiling point between 60 and 130 °C; and yield greater than 85%. In the second phase, three metrics of sustainability were employed: greenness, efficiency, and cost. Globally, a score was attributed to each solvent based on the assessment of the individual metric. From a list of 154 solvents, 1-butanol,...

The generalized parametric sensitivity criterion was used to obtain runaway diagrams for one- and two-dimensional heterogeneous models and a one-dimensional pseudo-homogeneous model. The simulation work was based on the partial methanol oxidation to formaldehyde, which occurs in a fixed-bed reactor, with two distinct catalytic zones. At the inlet of the reactor, the catalyst was diluted with inert packing followed by a region with pure catalyst. This activity profile induces a reduction in the parametric sensitivity of the process to temperature runaway, when compared to a uniform activity bed, and the sensitivity functions reach a minimum when the inlet temperature is in the range of 530−540 K. The dilution of the catalytic bed leads to an enlargement of the stable region of operation, which allows a gain in the critical methanol concentration of 20% for a feed temperature of 530 K (industrial operating temperature), higher gains being possible (40%) for higher inlet temperatures. Moreover, depending on the particular set of the operating conditions, one or two hot spots can be developed, one in each zone of the bed, it being important to follow both because one or the other can determine the critical conditions of the system. The additional mass flux by intraparticle convection leads to an increase in the parametric sensitivity when compared with the case where diffusion is the only mechanism taken into account.