Masters Theses

Date of Award

6-1984

Degree Type

Thesis

Degree Name

Master of Science

Major

Mechanical Engineering

Major Professor

H. Joe Wilkerson

Committee Members

William Johnson, James A. Eitner, W. Milligan

Abstract

The adverse effects of wear has continually plagued the operation of the TVA 20 MW Atmospheric Fluidized Bed Combustion Pilot Plant. Wear has caused serious problems in all aspects of the pneumatically fed below-bed coal feed system. This has given rise to the development of high wear resistant designs of feedline splitters, turning sections, and feed nozzles.

Wear testing of PVC feedline system components was conducted at The University of Tennessee to determine the wear characteristics of different designs. PVC was chosen for the feedline system component material to accelerate the wear testing results. A series of similar tests were conducted to determine the merit of the wear resistant designs. While the testing was limited in scope due to size, material, and operating constraints, the general wear characteristic test results have proven to be valuable in assessing new wear resistant designs.

For long radius PVC bend wear testing, the wear rate was found to be proportional to the cube of the transport velocity. A change in solids mass now rate also had a significant effect on the wear rate of the bends, about one half the effect of a change in transport velocity.

Wear testing of a standard 45 degree PVC wye showed that a 50 fold increase in the life of the wye compared to a long radius bend can be expected.

Two PVC floating valve caps with different recess depths were subjected to similar wear tests. It was found that a recess depth increase from 0.25 to 0.43 inches improved the wear resistance of the valve cap by a factor of six to seven.

Testing of a new 1:3 PVC feedline splitter design showed that the new splitter design was very resistant to wear. Testing also showed there was a relationship between the splitter's exit feedline lengths and the split equality. With equal exit feedline lengths, the split equality can be expected to be within ± 5 percent.

Two new steel feedline splitters were designed for replacement of the feedline splitters currently used at the TVA Pilot Plant: a 1:3 splitter design for compartments A-D, and a 1:6 splitter design for the modified recycle system. The 1:6 recycle splitter design was installed in the recycle system, and after 486 hours of operation, it has shown great promise. The 1:6 recycle splitter has not plugged, and more significantly, has not shown any observable signs of wear.

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