Energy Consumption and Energy Saving in the Heat-Setting and Dye-Fixation of Textile Fabrics on Stenters

Summary

Stenters are employed throughout the textile industries of the Community for the drying and heat-treatment of fabrics in open width, and the cost of the energy they consume is in the region of £30m per annum. In the processes of heatsetting and dye-fixation, performed at temperatures in the region of 200 degrees C, the energy consumption is typically 4 MJ (1.1. kWh) per kg of fabric. Consideration of the energy balance for these processes shows that 80 percent or more of this energy usage is discharged as hot air.

This exhaust is required to remove volatile impurities, which in the vapour phase are not injurious to the process; they become objectionable when they condense to a visible smoke and in this state may contaminate the fabric. Any significant reduction in energy consumption can only be achieved by reducing the exhaust flow rate, and this requires either that the process be operated with a higher atmospheric concentration of volatile matter or that the volatiles be removed from the recirculated air streams. This research programme has investigated these topics.

An impurity concentration of the order of 500 mg per kg air appears a reasonable target figure. Under these conditions the energy loss in the exhaust should generally be no greater than 1.6 or 2.0 MJ per kg of fabric and the total energy consumption about 2.5 MJ per kg. Recirculatory direct firing permits a further reduction in the total of 20 or 30 percent, and the optimum energy consumption for the process should therefore be in the region of 2 MJ per kg of fabric.