11 Ot. 2021. The drying phase in the paper machine is the most energy-consuming process of a paper mill. Therefore, it is essential to invest in the optimization of the drying section energy consumption, which constitutes one of the principal direct costs of every paper mill.

In the past, drying cylinders were generally built of cast iron because it was an easy to find, low-cost material and above all easily machinable. Currently, the demand for higher machine speeds and wider paper size imposed by the market requires a proportional increase in the number of drying cylinders to maintain the same level of drying capacity. The use of modern steels and manufacturing techniques, make cast iron cylinders disadvantageous and their replacement can bring great benefits in terms of machine management, especially regarding energy saving. In our recent technical analysis, we explore the rationale for steel cylinders. The factors that most influence the heat exchange through the drying cylinder are:

• diameter, thickness and material of the cylinders
• operating pressure and temperature
• the condensate drain system

Given the limits on maximum operating pressure and thus on the maximum condensate that can be extracted with current technologies, it is logical to improve the efficiency of the drying by replacing the cast iron cylinders with steel ones. Changing from cast iron to steel brings four key advantages:

• Greater thermal efficiency, since reducing shell thickness leads to a significant increase in heat exchange;
• Greater useful drying surface, due to the enlargement of the working width, resulting from the smaller size of the heads;
• Faster attainment of the working temperature, due to the increased heat exchange;
• Increase of safety standards, linked to the higher safety coefficients used for steel

De Iuliis C&A (Paper Machinery) of Italy designs and manufactures machines, systems and components for the production of paper and board as well as central cylinders for flexographic printing systems. They are represented in the UK by Papermachine Consultancy Services. See the full article at: https://www.pm-consults.com/2021/10/05/djm-world-leaders-in-steel-cylinder-technology/ and / or call Mike Mason of PCS on 07884 556542