The Effect of Using a Heating Tube in an Existing Spouted Bed Superheated Steam Dryer

Abstract

Interest in the use of biofuels, such as pellets and briquettes, has continued to grow in the European market in recent years. In order to manage the increased use of biofuels, the dryer capacity must also increase. One possible way of accomplishing this is to install heating tubes into the already existing dryers. Therefore, industrially relevant and appropriate design data, such as energy efficiency and a possible increase in the capacity of developing drying systems, are needed. This article presents the experimental results obtained from drying sawdust in a continuous spouted bed using a heating tube submerged in the bed; the results are compared with those obtained from a bed without using a heating tube. Superheated steam is used as the drying gas in all tests. The drying test is performed with an almost constant inlet moisture content and at three different inlet and outlet temperatures. The drying efficiency increases when the heating tube is turned on. Some explanations of the relation between inlet and outlet gas temperature and moisture content are presented.

Keywords:

• Drying efficiency
• Heating surfaces
• Heating tube
• Sawdust drying
• Spouted bed
• Superheated steam

ACKNOWLEDGMENTS

I thank Lars Pettersson for valuable help with the experiments; and Kamal Rezk, Dr. Roger Renström, Professor Bengt Månsson, and Karolina Schultz Danielsson for valuable help with the manuscript.