At the end of this module, you will be able to:
- Describe Yankee dryer shell design
- Describe steam distribution and flows into the dryer
- Describe condensate removal and flows out of the dryer
- Describe thermocompressor design and operation
- Describe pressure control
- Describe differential pressure control
- Identify condensate system issues
- Define Maximum Allowable Working Pressure (MAWP)
The following key questions are answered in this module:
What operating conditions affect the heat transfer from the dryer to the sheet?
The working steam pressure, condensate level in the dryer, dryer coating, and the dryer surface temperature affect the drying capacity of the Yankee.
What is blow-through steam?
Blow-through steam exits the dryer with the condensate and helps ensures adequate condensate removal.
What is a thermocompressor?
A thermocompressor uses high pressure motive steam to pull blow-through and flash steam from the condensate tank and create intermediate-pressure steam.
How is condensate removal controlled?
The differential pressure (dP) controls the flow of condensate and steam through the dryer. The dP is the difference between the ingoing steam pressure and the pressure on the outgoing side of the dryer.
How is dP controlled?
The dP can be controlled by setting a target dP and the thermocompressor opens and closes to maintain a constant dP. A second control method is measuring and controlling the flow of steam and condensate out of the dryer and adjust the dP to maintain a constant flow.
Below is a transcript of the video sample provided for this module:
Inside the yankee, the steam condenses and transfers its heat to the shell. The resulting condensate must be removed at the same rate as it forms in order to maintain the efficient transfer of heat to the sheet. The condensate removal equipment includes the condensate headers, soda straws, riser pipes, and central steam collection pipe. The condensate headers receive condensate collected by soda straws in the grooves of the shell. The condensate is carried away from the headers by the riser pipes to the central steam collection pipe. The soda straws are thin pipes that extend from the condensate headers into the centers of the grooves inside the dryer shell. Because the pressure inside the dryer is higher than the pressure inside the condensate headers, the condensate plus some steam, flows up the straws into the headers.
Use the additional resources and links below to learn more about this topic: