Conversion of Paper-Mill Sludge Into Pelletized, Composite Activated Sorbent

This Phase I project will test the feasibility of converting paper mill sludge or filter-cake (FC), which is typically landfilled or incinerated and is a major environmental concern, into pelletized, composite sorbent of activated carbon and highly porous clay. There are currently more than 500 paper mills in the United States, each generating from 10 to more than 100 dry-tons of FC each day. The composite-activated sorbent (CAS) is especially suitable for purification of industrial wastewater, such as paper mill effluent prior to discharge. The proposed two-stage technique involves segregated fluidized-bed pyrolysis, with programmed heating at relatively low temperature, to maximize char yield (carbon retention is critical to low-carbon feedstock of FC), and combustion of pyrolysis gases at higher temperature, with H2O and CO2 as the main gaseous products. Low- temperature pyrolysis of solid FC avoids gaseous pollutants (e.g., dioxins), typical of incineration processes where solid is subjected to combustion temperatures. No solid residue remains because char is generated in the matrix of residual clay to form a composite activated solid, which with high-temperature heating, results in both activated carbon as well as calcination of the clay. Clay serves both as a binder and an active sorbent component. The CAS thus obtained has typical specific-surface-area of 600 m2/g, and nominal iodine-number of 600, comparable with high-grade commercial activated carbon for water purification. The full-scale process produces a medium heating-value, combustible fuel gas, which has energy well in excess of the needs of the process itself. Phase I efforts will demonstrate the effectiveness of the pelletized CAS product, provide measurement of its mechanical and physical properties, and indicate processing parameters that affect these properties. It also will measure gaseous compositions in the pyrolysis and activation stages.