TABLE OF CONTENTS Louis Theodore, Eng.Sc.D.
Professor
Department of Chemical Engineering
Manhattan College
Bronx, NY
A particulate-settling chamber is installed in a small heating plant that uses a traveling grate stoker. Determine the overall collection efficiency of the chamber, given the following operating conditions, chamber dimensions, and particle-size distribution:
Chamber width: 10.8 ft (3.29 m)
Chamber height: 2.46 ft (0.75 m)
Chamber length: 15.0 ft (4.57 m)
Volumetric flow rate of contaminated air stream: 70.6 std ft 3/s (2.00 m 3/s)
Flue-gas temperature: 446 F
Viscosity of air stream at 446 F: 1.75 10 -5 lb/(ft)(s) [2.60 10 -5 (N)(s)/m 2]
Flue-gas pressure: 1 atm (101.3 kPa)
Particle concentration: 0.23 grains/std ft 3 (8.13 grains/m 3)
Particle specific gravity: 2.65
Standard operating conditions: 32 F, 1 atm (273 K, 101.3 kPa)
Particle-size distribution on the inlet dust:
| Particle size range, ?m | Average particle diameter, ?m | grains/std ft 3 | grains/m 3 | Weight % |
|---|---|---|---|---|
| 0 20 | 10 | 0.0062 | 0.219 | 2.7 |
| 20 30 | 25 | 0.0159 | 0.562 | 6.9 |
| 30 40 | 35 | 0.0216 | 0.763 | 9.4 |
| 40 50 | 45 | 0.0242 | 0.855 | 10.5 |
| 50 60 | 55 | 0.0242 | 0.855 | 10.5 |
| 60 70 | 65 | 0.0218 | 0.770 | 9.5 |
| 70 80 | 75 | 0.0161 | 0.569 | 7.0 |
| 80 94 | 87 | 0.0218 | 0.770 | 9.5 |
| 94+ | 94+ | 0.0782 | 2.763 | 34.0 |
Assume that the actual terminal settling velocity is one-half of the velocity given by Stokes law.
1. Express the collection efficiency E in terms of the particle diameter d p by employing the terminal settling velocity for Stokes law. Since the actual...
