Report No FR0317

Sept 1992

I BENEFITS

The selection of a sludge-drying process is shown to be dependent on many factors and must be made on a site-by-site basis. This report describes those factors which must be specified before selection of driers. Only then can the use of more energy efficient drying systems be considered.

II OBJECTIVES

To assess the potential for achieving more efficient sludge drying.

III REASONS

Drying by indirect or direct heating is an operationally proven technique to reduce the volume of sewage sludge. However, the energy efficiencies of the driers currently available could be improved, depending on the system of which they form a part, thus resulting in the saving of energy costs or increasing the potential for power generation.

An investigation of these new energy efficient driers is required.

IV CONCLUSIONS

The use of new improved energy efficient driers compared to proven driers is significantly more dependent on the specific requirements for a drying system at a sewage treatment works than the energy efficiency of the driers.

V RECOMMENDATIONS

It is recommended that the selection of a drier is based firstly on the specific requirements of sludge drying and then secondly on the energy efficiencies of particular driers. A comparison of individual manufacturers driers performance and costs will determine the use of improved energy efficient processes.

VI RESUME OF CONTENTS

The report briefly discusses the theory of drying and then reviews the different types of thermal drying process. The review includes indirect, direct and hybrid driers and, energy reduction processes.

A comparison of the driers and processes is made before a guide to the requirements for selecting a process is presented.

Copies of the report are available from FWR, price £15.00, less 20% to FWR Members.