Energy-efficient yankee dryer hood system

• US 8,132,338 B2
• Filed: 04/06/2010
• Issued: 03/13/2012
• Est. Priority Date: 05/03/2006
• Status: Expired due to Fees

• Current Assignee: GPCP IP Holdings LLC
• Original Assignee: Georgia-Pacific Consumer Products LP (KOCH Industries Incorporated)
• Inventors: Deem, Charles E., Hunter, Mark S., Hodkiewicz, Donald J., Monroe, Steven W., Thomson, Scott M., Barrie, Thomas H., Jadin, Timothy D., Gardner, Steven M., Giannunzio, Scott L.
• Primary Examiner(s): Gravini, Stephen M.
• Application Number:
  US12/754,656
• Publication Number:
  US 20100192403A1
• Time in Patent Office: 707 Days
• Field of Search: 343/80, 343/81, 344/13, 344/44, 344/54, 344/66, 344/97, 162/274, 162/198
• US Class Current: 34/454
• CPC Class Codes: D21F 5/044 using air hoods over the cylinders
• CPC Class Codes: D21F 5/181 on Yankee cylinder

Abstract

A paper machine configured as a swing machine capable of producing both light and heavy grades providing a Yankee hood split into a wet end half and a dry end half, at least one hood half being a flex-hood half wherein the supply for that half is capable of being run with either combustion heat or recycled heat and is capable of either recirculating the exhaust from the hood or discharging it to the atmosphere. The heater for the flex-hood half comprises both a primary combustion heat source and an indirect heat source capable of extracting by-product heat from another operation. The exhaust system for the flex hood half is capable of being run in either a straight through mode or in a recirculating mode.

Claims

1. A method for operating a paper machine for manufacture of absorbent paper, comprising the steps of providing a paper machine having:

(a) a forming loop comprising a headbox and a translating foraminous support;

(b) a dryer section adapted to receive absorbent paper from said forming loop; and

(c) a reel adapted to receive absorbent paper from said dryer system;

and a dryer section comprising;

(i) a rotable Yankee dryer cylinder internally heated by steam;

(ii) a wet end hood section encompassing a portion of said Yankee dryer cylinder adjacent Ruining loop;

(iii) a dry end hood section encompassing a portion of said Yankee dryer cylinder adjacent said reel;

(iv) a dryer system exhaust;

(v) a wet end hood supply duct having a process heat exchanger, a first exhaust gas heat exchanger and a first burner disposed therein adapted to supply heated air to said wet end hood section;

(vi) a wet end hood exhaust duct adapted to receive air from said wet end hood section;

(vii) a wet end return duct adapted to supply air from said wet end hood exhaust duct to said wet end hood supply duct;

(viii) a first diverter damper system connected between said wet end hood exhaust duct and said wet end return duct, said first diverter damper being operable to selectively direct a quantity of moisture laden air exhausted from said wet end hood section to said wet end hood supply duct or alternatively to said dryer system exhaust through said first exhaust gas heat exchanger;

(ix) a dry end hood supply duct having a second process heat exchanger, a second exhaust gas heat exchanger and a second burner disposed therein adapted to supply heated air to said dry end hood section;

(x) a dry end hood exhaust duct adapted to receive air from said dry end hood section;

(xi) a dry end return duct adapted to deliver air from said dry end hood exhaust duct to said dry end hood supply duct; and

(xii) a second diverter damper system connected between said dry end hood supply duct and said dry end return duct, said second diverter damper system being operable to selectively direct air exhausted from said dry end hood section to said dry end hood supply duct or alternatively to said dryer system exhaust through said second exhaust gas heat exchanger;

and controlling the position of said first diverter damper system to bleed in sufficient air to maintain the humidity in the air supplied to said wet end hood section in the range of between 0.2 and 0.7 pounds of water per pound of dry air at a temperature of over 550°

F.;

while controlling said second diverter damper system to pass fresh make up air though one of said process heat exchangers and one of said exhaust gas heat exchangers to said dry end hood section at a temperature of between 350°

F. and 450°

F.; and

exhaust air from said dry end hood section to the atmosphere through an exhaust gas heat exchanger.

2. A method for operating a paper machine for manufacture of absorbent paper, comprising the steps of providing a paper machine having:

(a) a forming loop comprising a headbox and a translating foraminous support;

(b) a dryer section adapted to receive absorbent paper from said forming loop; and

(c) a reel adapted to receive absorbent paper from said dryer system;

wherein said dryer section comprises;

(i) a rotable Yankee dryer cylinder internally heated by steam;

(ii) a wet end hood section encompassing a portion of said Yankee dryer cylinder adjacent forming loop;

(iii) a dry end hood section encompassing a portion of said Yankee dryer cylinder adjacent said reel;

(iv) a dryer system exhaust;

(v) a wet end hood supply duct having a first burner disposed therein adapted to supply heated air to said wet end hood section;

(vi) a wet end hood exhaust duct adapted to receive moisture laden air from said wet end hood section;

(vii) a wet end return duct adapted to supply air from said wet end hood exhaust duct to said wet end hood supply duct;

(viii) a dry end hood supply duct having a second burner disposed therein adapted to supply heated air to said dry end hood section;

(ix) a dry end hood exhaust duct adapted to receive moisture laden air from said dry end hood section;

(x) a dry end return duct adapted to deliver air from said dry end hood exhaust duct to said dry end hood supply duct;

(xi) at least one of said supply ducts having an air to air heat exchanger disposed therein adapted for heating air supplied therethrough; and

(xii) a diverter damper system adapted to direct moisture laden gas exhausted from one of said hood halves to said heat exchanger and heat air supplied though one of said supply ducts;

comprising the steps of passing moisture laden air from said wet end hood section exhaust duct to said wet end hood supply duct at a temperature of over 550°

F. and a moisture content of between 0.2 and 0.7 pounds of water per pound of air, while passing fresh air through an air to air heat exchanger to said wet dry end hood half at a temperature of between 350°

F. and 450°

F. and discharging air from said dry end hood half to the atmosphere through an air to air heat exchanger.

3. A method of operating a paper machine having a Yankee dryer with a hood which is split between a wet end hood half and a dry end hood half, comprising the steps of:

(a) recirculating air from said wet end hood half through a burner and back to the wet end hood half while introducing sufficient make up air to;

maintain the temperature of the stream returned to said wet end hood half at over about 550°

F.; and

(ii) maintain the humidity of the air stream returned to said wet end hood half at between about 0.2 and 07 pounds of water per pound of air;

while

(b) passing fresh air to said dry end hood half at a temperature of between 350°

F. and 450°

F.; and

discharging said air from said dry end hood half to the atmosphere through an air to air heat exchanger.