Evaluation of Energy Consumption in the Mercury Treatment of Phosphor Powder from Spent Fluorescent Lamps Using a Thermal Process

Abstract

Abstract:In a pilot-plant-scale thermal mercury treatment of phosphor powder from spent fluorescent lamps, energy consumption was estimated to control mercury content by the consideration of reaction kinetics. Mercury content was analyzed as a function of treatment temperature and time. The initial mercury content of the phosphor powder used in the thermal process was approximately 3500 mg/kg. The target mercury content in the phosphor powder thermal process of the phosphor powder was 5 mg/kg or less at 400 • C or higher because the target mercury content was recommended by Minamata Convention and Basel Convention. During thermal processing, the reaction rate was represented by a first order reaction with the Arrhenius equation. The reaction rate constant increased with temperature from 0.0112 min −1 at 350 • C to 0.0558 min −1 at 600 • C. The frequency factor was 2.51 min −1 , and the activation energy was 6509.11 kcal/kg. Reaction rate constants were used to evaluate the treatment time required to reduce mercury content in phosphor powder to be less than 5 mg/kg. The total energy consumption in a pilot-plant-scale thermal process was evaluated to determine the optimal temperature for removing mercury in phosphor powder.

Feasibility study of fluorescent lamp waste recycling by thermal desorption

“…Total Hg (THg) in CFL samples ranged from 125.4 to 151.3 mg kg −1 , with a very low variation coefficient of 6.9% observed over the 5 sampling days. These figures are much lower than those for spent CFL bulbs in other studies: 1430–13,300 mg kg −1 (Raposo et al 2003 ) and 3418.34 ± 269.26 mg kg −1 (Choi and Rhee 2017 ). Considerable Hg concentrations can be found in fluorescent glass bulbs, ranging greatly around the world from 8.27% (Jang et al 2005 ), 13.66% (Rey-Raap and Gallardo 2013 ) and 16.27% (dos Santos et al 2010 ) to 21.6% (Taghipour et al 2014 ) and 50% (Hobohm et al 2017 ).…”

“…This study, as well as others (Jang et al 2005 ; Rey-Raap and Gallardo 2013 ; Taghipour et al 2014 ; Hobohm et al 2017 ), highlights the large amounts of Hg trapped in glass, which requires a high temperature of 437 °C to achieve a recovery rate of at least 70%. Some research describes the impact of thermal recovery treatment times on these waste products (Choi and Rhee 2017 ), with an optimal treatment time of 360 min at 400 °C for phosphorous powder using the reaction rate constant and activation energy. These promising results are dependent on the fractionation of Hg compounds in waste, especially those trapped in glass.…”