Factors affecting the electrical resistivity of kraft recovery boiler precipitator ash

Abstract

The electrical resistivity of ash particles is an important parameter that determines the efficiency of electrostatic precipitators. This systematic study examines the resistivity of recovery boiler precipitator ash as a function of electrical field strength, time of exposure, particle composition, and gas composition and temperature. Synthetic ash and actual ash samples from several pulp mills are used. The results show that most ash samples tested had a resistivity between 109 and 1010 Ω·cm, but one of the samples had an unusually high resistivity, 1012 Ω·cm. The resistivity increases with temperature up to about 140°C, then decreases. At a given temperature, the resistivity decreases with increasing moisture and sulfur dioxide concentration in the gas. Resistivity also increases with an increase in chloride content in the ash, but is not affected by the carbonate, sulfate, and potassium contents. The results imply that recovery boilers burning liquors with high solids and high chloride contents produce ash with higher resistivity, making it more difficult for electrostatic precipitators to capture.

Assessment of Mixed Amendments of CaCO3/Na2SO4 Ratio on the pH Buffer Capacity and Exchangeable Sodium Percentage of Soils with Contrasting Properties

“…In production, an additive called "white liquor" is used, composed mainly of sodium and sulfur in their active forms as sodium hydroxide (NaOH) and sodium sulfide (Na 2 S) [13]. This liquor can be reclaimed through the recovery cycle, reaching an efficiency level of up to 97% [14]. After wood cooking, this additive is converted into "green liquor" containing a large proportion of these elements in the form of sodium carbonate (Na 2 CO 3 ) and sodium sulfate (Na 2 SO 4 ), representing approximately 80% of the total solid waste [14,15].…”

“…This liquor can be reclaimed through the recovery cycle, reaching an efficiency level of up to 97% [14]. After wood cooking, this additive is converted into "green liquor" containing a large proportion of these elements in the form of sodium carbonate (Na 2 CO 3 ) and sodium sulfate (Na 2 SO 4 ), representing approximately 80% of the total solid waste [14,15]. In the recovery cycle, Na 2 CO 3 is converted back to NaOH, using calcium oxide (CaO) obtained from calcination of lime sludge [13].…”