Howard EmpieProfessor School of Chemical and Biomolecular    Engineering Ph.D., University of Minnesota, 1969

Howard (Jeff) Empie obtained his B.S. degree from Syracuse University in 1964, his M.S. from MIT in 1965, and his Ph.D. degree from the University of Minnesota in 1969, all in Chemical Engineering. He worked for Hercules, Inc., at its corporate research center from 1969 to 1978 in process research and development. From 1979 to 1989, he worked for International Paper Company at its corporate center as a Senior Research Engineer in kraft chemical recovery and then as Group Manager. In 1989, he accepted a faculty position as Professor of Engineering in chemical recovery at IPST.

His current research interests include black liquor spraying systems, odor reduction, green liquor clarification, and alternative kraft liquor recovery processes, focusing on fluidized bed technology. He has taught courses at IPST in Reaction Engineering, Chemical Recovery, and Mass and Energy Balances.

Research Summary

Odor Reduction:

Odor reduction is an increasing desire of communities located in the vicinity of a kraft pulp mill. No commercially feasible technology exists at present which eliminates the odor without producing a by-product waste stream that requires additional treatment. A project is being conducted to investigate the use of mill-generated green liquor dregs to reduce H2S emissions in a waste gas stream to concentrations below the odor threshold. Being able to implement a process step that employs a sorbent that is self-generated, readily available (i.e., dregs), and does not produce a secondary waste stream that requires additional treatment should be an attractive low-cost alternative. Bench-scale experiments using mill-derived dregs in a packed-bed reactor have determined the rate of H2S removal as a function of several process parameters. Preliminary process calculations for a typical 1000 T/D recovery boiler show that the daily production rate of dregs can reduce H2S emissions to the required parts per billion level if the dregs can be regenerated and reused in a second cycle of H2S removal. Accordingly, a method using weak wash has been developed to meet this requirement, effectively further closing the mill sulfur balance.

As environmental regulations force paper mills to close up their water cycles and minimize freshwater use, effluent streams will have to be recycled internally and burned with the black liquor. This will lead to a buildup of nonprocess elements in the liquor cycle. Because these NPE's must be controlled at acceptable levels, maintaining dregs removal rates is a big concern with increased levels of NPE's. Presently, they are purged primarily with the green liquor dregs leaving the bottom of the green liquor clarifier. A fundamental study underway involves looking at the fluid dynamics of green liquor clarifier design in an attempt to learn how to improve dregs separation efficiency and increase clarifier capacity. Alternative feedwell designs are being evaluated, along with a novel idea on how to minimize backmixing at the feedwell outflow location.

Black Liquor Spraying:

A new method of spraying moderate-to-high viscosity fluids at rates with resultant drop sizes similar to black liquor at conventional and high solids is being developed to give a controlled drop size distribution that should result in lower carryover rates and an ability to fire higher solids liquors. The method, based on effervescent atomization technology, has been shown to work with a model fluid (corn syrup). Plans are being formulated to test the method on a commercial scale at a mill to be identified.

Deadload Reduction:

Deadload chemicals in kraft white liquor cause many drawbacks in the kraft liquor cycle, including reduced energy efficiency, reduced production capacity, and increased equipment scaling. Technology is being developed to virtually eliminate the two main components of this deadload, namely sodium carbonate and sodium sulfate.