Many
industrial processes require controlled incoming flow temperatures in
order to operate efficiently. ASC has examined a wide range of cases
where two flow streams of different temperature merge. The resulting
flow stream often contains significant temperature stratification which
degrades the performance of downstream equipment. In some instances,
this temperature stratification can also be a safety issue.
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Coal
pulverizers are designed to grind and dry wet coal to a fine powder
prior to combustion in a furnace. Hot incoming air provides the thermal
energy for drying and also the transport mechanism for the coal size
classification and delivery to the furnace. The inlet air temperature
is controlled using a tempering air stream, as shown in Figure 1.
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Figure 1. Typical pulverizer inlet ductwork,
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Airflow
Sciences designed a flow mixing device to optimally merge two streams
and obtain a resultant stream of more uniform temperature. A key
consideration was generating the mixing effect with minimal system
pressure loss. ASC's design effort resulted in the issue of U.S. Patent
Number 5,463,967.
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The
ASC mixer was designed using a computational fluid dynamics (CFD)
model. The CFD flow model helps optimize the mixer design for any specific duct
system geometry.
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| Flow Temperature Stratification Before and After Installation of Mixing Device Designed Using CFD Flow Model |
| Pulverizer Inlet Measurement |
Before |
After |
| Average Temperature |
534 degF |
573 degF |
| Minimum Temperature |
512 degF |
568 degF |
| Maximum Temperature |
574 degF |
581 degF |
| Maximum Delta T |
58 degF |
13 degF |
Table 1. Flow Mixing Device Performance
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The
ASC mixer was recently installed in a pulverizer inlet duct at ATCO
Power's Sheerness Station in Hanna, Alberta, Canada. Plant measurements
indicated a large temperature deviation (58 degF) in the pulverizer
inlet ductwork.
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After
installation of the ASC mixer, the temperature profile was re-measured.
The temperature deviation was reduced considerably, to 13 degF, with
the mixer in place. Results are shown in Table 1 and Figure 2. The
additional pressure loss caused by the mixer was barely measurable at
0.1 inches of water.
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If
you have a process that requires controlled, uniform inlet flow, give
us a call to discuss the applicability of the ASC mixer, which was designed using this CFD flow model.
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(734) 525-0300
