Heat recovery from vacuum blowers on a paper machine
A papermaking process including the steps of forming a wet paper web on a papermaking machine, pulling vacuum through the web to remove water from the web and thereby generate discharge air, and diverting at least a portion of the discharge air through a control loop to a hot air drying system within the papermaking process to aid in drying the web, wherein the vacuum is generated by centrifugal blowers.
1. A papermaking process comprising:
forming a wet paper web on a papermaking machine;
pulling vacuum through the web at at least one point along the papermaking process to remove water from the web and thereby generate discharge air; and
diverting at least a portion of the discharge air through a control loop to a hot air drying system disposed at a second point within the papermaking process to aid in drying the web, wherein the vacuum is generated by centrifugal blowers.
2. The process of claim 1 , further comprising the step of controlling humidity of hot air within the hot air drying system.
3. The process of claim 2 further, wherein the step of controlling humidity
comprises: detecting humidity of the hot air within the control loop; and
controlling speed of an exhaust fan within the hot air drying system based on the detected humidity so as to adjust the humidity of the hot air to a predetermined level.
4. The process of claim 3 , wherein the step of controlling humidity further comprises controlling position of a fresh air damper within the control loop based on the detected humidity.
5. The process of claim 1 , further comprising the step of controlling pressure of the discharge air diverted to the hot air drying system.
6. The process of claim 5 , wherein the step of controlling pressure comprises:
detecting pressure of the discharge air; and
controlling position of a damper within the control loop based on the detected pressure so as to adjust the pressure of the discharge air to a predetermined level.
7. The process of claim 1 , further comprising the step of controlling pressure of hot air within the hot air drying system.
8. The process of claim 7 , wherein the step of controlling pressure of hot air comprises:
detecting pressure around a hot air impingement hood within the hot air drying system;
controlling position of a vacuum exhaust damper within the control loop based on the detected pressure so as to adjust the pressure of hot air to a predetermined level.
9. The process of claim 8 , wherein the step of controlling pressure of hot air further comprises controlling speed of a discharge air supply fan based on the detected pressure.