On-Line Study on Single Felting and its Effect on the Paper Mill Heat and Power Economy

Abstract

When, in a paper dryinr machine, drive groups equi pped wi th conventi ona1 fabri cs are refitted with single felting, changes in the specific evaporation rate as well as in the functionin0 of the steam and condensate systems are evident. To observe the resultina chanoes and to make an analysis of the-changed conditions, an on-line study was made on two production machines.The measurements taken indicate that the sheet cools some 2.5 to 8.0 QC while passing the bottom cylinders, on the outward side of the fabric. Specific evaporation rates measured for single feltin9 were approx. 70 percent of the corresponding evaporation figures for a conventional double fabric configuration. Despite this, the annual output of the machine may increase, due to smoother machine operation. However, if the instantaneous drying intensity is to remain unchanged, an increase of a few tenths of a bar in the machine supply steam pressure will be required. This results in a power loss at the power plant, and a corresponding additional cost, in case the machine operating efficiency is not improved.This presentation further examines the combining of the pressure duration curves of two machines, and the feasibility of target adaptive back pressure control, whereas a general rise of the pressure level also increases fluctuation and thereby makes control more desirable.