Systematic quality control of incoming raw materials and additives for paper manufacturing

The future of the paper industry is influenced by both technological and economic boundary conditions. Although a majority of paper grades have already reached an appreciably high quality level, there is a continued demand for ever-increasing paper qualities. Papermakers trying to meet this challenge have to provide for quality assurance of raw materials and additives used in the manufacturing operation. Chemical aids account for a minor share of the total furnish, but they are nevertheless decisive far undisturbed manufacturing and for certain quality features of the paper, such as brightness, chromaticity coordinates, hydrophobicity, wet and dry strength, printability etc. Production efficiency and product quality are crucially dependent on whether or not the chemical aids are in an appropriate condition. Besides, the level of active substances contained in the chemicals has to be monitored - not only in order to ensure economical use and optimized dosages of chemicals, but also to avoid production failures caused by overdosages. The downtime costs of modern high-performance plants are in the range of several ten thousands deutschmarks per hour. Depending on the paper grade produced, a one-hour downtime may result in production losses in the amount of up to 30,000 DM. These immense costs alone justify careful monitoring of the production materials. The research project was devoted to identifying options of optimum organisation of the qualify control of incoming raw materials and additives used in the paper industry, and to evaluate the significance of the various options. In Germany and Europe, a representative survey was conducted among paper mills to gain an overview of current ingoing quality control practices, and among chemical suppliers to verify their outgoing quality control schemes. The inquiry revealed an unexpected lack of interest in ingoing qualify control on the part of the industry. Within the framework of the project; a listing of measuring methods enabling systematic qualify control of incoming products was compiled. This listing primarily includes simple, but meaningful methods that may be applied in part before the raw materials and additives are unloaded at the mill site. It is recommended that reference samples are retained for complaints handling. Under the research project, a selection of parameters (i. e. solids, wet screening residues, pH or viscosity), which are basically relevant to the ingoing control of resources and additives, have been monitored in a number of paper mills over an extended period of time. The contribution presents the experiences gained in this connection.