Patent EP-1186706-A2 (EP)
Inventor: GEHR VOLKER DR
IPC: D21B1/32
Filed: 2001-08-17
Abstract: Processing comprises stage(s) with set chemical and physical developments, using measurements to give characteristic values used with condition models. The measurements for process stage(s), affecting target values in final product, are registered and/or evaluated on-line. They are used (in)directly to control/optimize process(es) by setting the use of chemicals, auxiliary agents, energy and/or waste disposal and emissions. To prepare the fiber or used paper materials, for papermaking, they are processed by flotation, bleaching and/or dispersion. The processing of fibers for paper production uses mathematical or production economics algorithms to derive the characteristic values from the on-line measurements. With a flotation process, values relating to the raw materials are taken to determine at least part of the measured values and the characteristic values e.g. the ash content, material density, optical characteristics, dirt particles, residual ink, pH values, temperatures, flow rates, currents, powers, the level of the material in the container, additives and/or stickies in the feed, usable material and/or rejected material and/or the derived characteristic values e.g. increase in the degree of whiteness, reaction or throughput times, specific work, loss of solids and/or loss of ash and/or production economics values e.g. the costs of chemicals, additives, water, raw material, energy, losses and/or disposal and/or computed values for the technology and the economics of production to be taken into account. The target values are set in advance for the maximizing, minimizing and/or cost containment of the production volumes, the mechanical and/or optical characteristics and/or the costs for operating, the raw materials and/or finishing. With a flotation process, the target values preferably include at least one of the given target areas from a constant quality of the end product from the process, constant loss of solids and/or minimum operating costs especially at a constant quality level. To control or optimize the flotation process, at least one process parameter is affected e.g. the air content of the paper fiber suspension in at least one process stage and especially in the primary and/or secondary stage, the overflow volume in at least one and/or other of the two stages, the bubble size, chemicals present and/or the like. At least one process parameter is adjusted and at least generally compensated for raw material deviations affected by the characteristic values for the end product. For the control or optimizing of at least one process, by acting on several process parameters, at least a part of the characteristic values are assessed or weighted to act on the parameters. At least two process stages and/or at least two processes are combined into a common optimized module. A compressed or reduced number of characteristic values in a module are used to control one or more processes. At least part of the target and characteristic values are transformed into a unified basis by a computer, using the volume price as the unified basis. With combined process stages and/or processes, the target values are taken from preferably at least one of the constant optical characteristics, constant ash volume, minimal and/or constant dirt points, minimal loss, minimal use of added chemicals and/or minimal energy consumption.. At least part of the target values are weighted to control and optimize the process. The weighting is by assessment through cost aspects and/or by optimizing costs. With combined process stages and/or processes, at least part of the measured and characteristic values are from at least one of the material density, ash concentrations, filling level in the container, overflow volumes, amount of residual ink present, amount of residual peroxide present, temperatures, pH values, dispersion work, dwell times, optical characteristics and mechanical characteristics. At least one sensor gives at least part of the measured values and characteristic values. The sensor is especially for measurement of the degree of whiteness, on-line dirt measurement, measurement of the material density, monitoring the flow rate and/or the level of the material in the container.