AT404641B - METHOD FOR CONTROLLING AND / OR REGULATING A DRYING PROCESS, ESPECIALLY PAPER DRYING - Google Patents

Description

AT 404 641 B

The invention relates to a method for controlling and / or regulating a drying process for drying paper, in which different energy flows are supplied, these individual energy flows being variable.

Such methods are used for example in paper drying, the drying being carried out on the one hand by contact drying using a steam-heated cylinder and on the other hand by convection drying by means of blowing hot air. Here, the temperature can still be generated by gas and the air volume or blow-out speed is generated by a supply air fan with an electric drive. There are a wide variety of methods for controlling such a process, the main aim being to achieve the required quality in terms of dryness and surface quality with the corresponding throughput for given paper types. For this purpose, the machine speed and the energy supply of steam (steam pressure, steam quantity) and gas temperature are regulated. At regular intervals, e.g. Weekly or monthly, the energy consumed during this period and its costs are summarized according to energy sources in corresponding reports. Usually it is not possible to make a statement about the specific energy costs for a certain product. Minimizing energy costs is practically impossible, since changes in the operating mode usually have a strong impact on the result, i.e. have the dry content or the throughput. In the event of a short-term change in the product quality to be produced and also in the event of short-term changes in energy prices, either through a different mode of operation of the company's own power station or through changed electricity prices, minimization cannot be carried out.

DE 33 28 557 A1 (Krantz) describes a process for the heat treatment of textile goods. A method is described here in which the end of the drying process and the beginning of the fixing process take place without measuring the actual temperatures. A change in individual energy flows is not apparent from this document. Furthermore, EP 0 258 979 A (Albers) describes a device for the simultaneous exchange of heat and mass, among other things. also for drying. However, here too there is no indication of the regulation of several energy flows while keeping the drying output constant.

The invention has therefore set itself the goal of optimizing the use of the individual energy flows or carriers in such a way that the total energy costs result in a minimum.

This is done according to the invention in that the consumption of the individual energy flows is measured continuously and at least two energy flows are changed in such a way that there is no change in the production state, and when one energy flow is reduced, at least one other energy flow is amplified to such an extent that the drying remains the same overall. By continuously measuring the energy flows, whose current consumption values can also be displayed and from which the total energy costs can be displayed continuously, an automatic comparison of different driving styles with regard to their economy and also a quick reaction to changes can be achieved, the gradual change the division results in a rapid approximation to the minimum without the risk of re-entering areas of higher total energy costs. Furthermore, all influences on production and product quality are excluded, so that for a given state of production a distribution of the energy supply by individual energy flows is regulated to a minimum cost.

An advantageous development of the invention is characterized in that the change in the energy flows takes place step by step and the total energy costs are determined after each step and the step change for the next step is determined therefrom. This procedure allows the cost of energy flows to be optimized very quickly.

A favorable embodiment of the invention is characterized in that the energy flow with the highest energy costs is reduced, and subsequently the energy flow with the next highest energy costs can be reduced. In this way, a cost reduction with constant quality is always achieved in the control phase.

A further development of the invention is characterized in that the costs or specific costs of the individual energy flows are variable and are continuously specified for the regulation of the energy flows, the current specific costs being taken over directly from a connected process control system, another internal computer system or a database can. Especially with changes in the costs or specific costs for the individual energy flows, a minimum of drying costs can be achieved practically at any time by means of an ongoing specification. If the current values are adopted by the connected process control system or another internal computer system, e.g. the current costs of the individual energy flows from an in-house power plant or the energy costs used for billing can be used. If the energy costs are taken from a database, e.g. in a simple manner on regular electricity prices - 2

AT 404 641 B changes due to day / night electricity or summer / winter tariffs are taken into account.

The energy flows can be regulated particularly advantageously if the individual energy flows are caused by different forms of energy, e.g. Steam, oil, gas, el. Energy are generated. If the individual energy flows are generated by different forms of energy, a significantly lower overall cost minimum can be achieved than when changing energy flows with the same type of energy, only the different drying efficiency influencing the energy costs due to the respective energy flow.

An advantageous development of the invention is characterized in that with a predetermined change in the production state, i.e. of the total energy requirement, all energy flows are changed evenly in the existing ratio. Such a change in the energy flows ensures a rapid approximation to the new total cost minimum.

A favorable variant of the invention is characterized in that with a predetermined change in the production state, i.e. of the total energy requirement, if the demand increases, the energy flow with the lowest costs first, or if the demand decreases, the energy flow with the highest costs is changed first. With such a change in the energy flows, the most cost-effective division of the energy flows is found with every step in the direction of the new total cost minimum.

A particularly advantageous development of the invention is characterized in that when the production and / or the costs of the individual energy flows change, the ratio of the individual energy flows is set as the starting value and then adjusted when the cost minimum is reached with the same or similar production parameters / energy costs from previous production states is regulated. If the production data changes, e.g. Sheet weight or dry-held, this leads to a significantly changed drying behavior and a greatly changed energy requirement. It is therefore particularly advantageous to use empirical values for similar production states, since these are very likely already close to the total cost minimum sought. The same applies to a sudden change in the cost of individual energy sources, e.g. when changing from day electricity tariff to night electricity tariff (and vice versa) is the case. Here, too, it proves to be particularly advantageous if experience values with similar parameters are used.

An advantageous embodiment of the invention is characterized in that when the cost minimum or a barrier of one of the regulated energy flows is reached, a further energy flow is changed, two types of energy being varied in a particularly favorable manner and, after reaching the cost minimum, further types of energy can be varied until the Total cost minimum is reached. This procedure means that system-related limits, e.g. maximum permissible air temperatures or vapor pressures, not above or below and also when an " optimal " Ratio of two energy flows reached a total cost of drying.

It is particularly favorable if the step size of the change in the energy flows is increased or decreased in accordance with the changes in the result. A larger change in the energy flows during the start-up process or after a production changeover or change in energy costs makes it possible to quickly find the optimal distribution of the energy flows. When settling to the optimal distribution, smaller increments can then be used, which avoids fluctuations in operation.

An advantageous variant of the invention is characterized in that the change in the energy flows is adapted to the response time of the corresponding adjustment processes. By taking the different response times into account, an undesired influence on production is avoided.

The invention further relates to a system for controlling and / or regulating a drying process, in particular for drying paper, with a dryer to which the drying energy is supplied via different energy flows. According to the invention, an optimization system is connected to the process control system in order to achieve and regulate a desired product quality. By separating the process control system and the optimization system, it can be achieved that the production settings remain constant and only the distribution of the drying energy to the individual energy flows and / or types of energy varies and is optimized with regard to cost minimization. Furthermore, the previous system can be retained and the drying system can also be operated without an optimization system.

A favorable further development of the invention is characterized in that the optimization system consists of a control unit with signal acquisition and an optimization computer for varying the energy flows in order to achieve a minimum cost. Such a configuration enables the signal acquisition and acquisition of the corresponding energy flow data from. advantageously separate the actual optimization, so that even if the optimization computer fails, trouble-free operation 3

AT 404 641 B is possible, whereby an approximation to the total cost minimum is possible by manual control.

The invention will now be described by way of example in the following with reference to drawings, in which FIG. 1 shows an overall dryer system of a tissue machine with the corresponding regulators and FIG. 2 shows the flow diagram of the regulation of the individual energy flows.

1 shows, as an example of a drying process using different energy flows and types, a tissue drying system in which the method and the system are preferably used. In this case, the drying system 1 is fed the paper 2 and passed over a steam-heated drying cylinder 3, hot air being blown onto the paper from so-called drying hoods 4, 4 '. The paper 2 is subsequently passed through an on-line quality measuring system 5 and rolled up on a roller 6. The drying energy is supplied on the one hand to the drying cylinder 3 via a steam line 7, and on the other hand via hot air which is heated by gas burners 8, 8 'and inflated by fans 9, 9'. Fresh air is conducted via a supply air fan 10 via a so-called exhaust air heat exchanger 11 and preheated and subsequently fed to the fan 9 'of the second hood half. This fresh air is mixed in from the exhaust air line 12 of the second hood half. The rest of the exhaust air is fed to the fan 9 via an exhaust air fan 13 and mixed there with exhaust air 14 from the first hood half. The rest of the exhaust air 14 is passed by means of an exhaust air fan 15 over the exhaust air heat exchanger 11, in which the thermal energy is used to heat the fresh air. The process control system 16 continuously receives values of the moisture of the paper web from the quality measuring system 5, which is compared with the target value and is regulated via a speed control 18 of the drive of the drying cylinder 3 and thus of the entire drying system 1. Furthermore, an optimal use of energy for drying can be achieved by an exhaust air control 19, which controls the exhaust air fan 15 and thus the exhaust air quantity. The regulation described so far is product-related and does not take into account the energy cost situation. The current energy use of the individual energy flows is determined by a steam quantity measurement 20, gas quantity measurement 21, 21 'and current consumption measurement 22, 22' of the fans 9, 9 '. The consumption of other types of energy such as Oil can be measured. The measured consumption values are transmitted on the one hand to the process control system 16 and on the other hand to the optimization system 23. In order to minimize the total energy costs, the web speed 24 and the weight 25 are continuously measured and the production quantity is thus determined. The current total energy costs 27 can be determined at any time by entering 26 the current energy costs or specific energy costs 26, which can either be specified manually, taken from a database or taken directly from a process computer. Depending on the previous optimization step, the individual energy flows are then continuously varied. The optimization computer can work particularly efficiently if the drying capacity is not used to the utmost and thus the system-related limits are not reached as quickly, which means that there is still scope for optimization. This applies to many systems and in many production conditions. In addition, the permanent display of the current total energy costs 27 provides an effective means of checking the mode of operation and also the state of the system.

The regulation is now carried out in such a way that the proportion of the energy types is electrical gas or. Oil and steam energy is varied automatically until the total energy cost minimum is found. All other production settings remain constant, so that the machine control takes place as usual by the process and quality control system 5, 16, 17, 18.

The optimization starts with start values, e.g. can come from previous optimization processes. All steps to minimize costs become production-neutral, i.e. without changing the production status. For this purpose, when reducing an energy flow, another energy flow, advantageously with a different type of energy, is amplified to such an extent that the drying remains the same overall. For example, a reduction in the blow-out speed (electrical energy) is compensated for by a corresponding increase in the vapor pressure or the blown air temperature (gas or oil energy).

After an optimization step has been completed, a comparison of the energy costs 27 with those of the previous state is carried out. Depending on whether this has led to a reduction in price or an increase in price, the change for the next optimization step is derived from this. Is the optimum, i.e. found the cost minimum for the variation of the two types of energy, the same is carried out in rapid succession with all parameters, so that an optimized overall result is achieved.

By adaptively adapting the search steps, a larger adjustment can be carried out in a short time, which enables the cost minimum to be found quickly when starting off. The system is advantageously supported with “fuzzy logic methods”, so that it is a self-learning system, as a result of which the optimization period until the cost minimum is reached is significantly reduced. 4th

Claims (16)

AT 404 641 B Fig. 2 now uses an example to illustrate the process of regulating the individual energy flows. In a first step, the ratio of steam consumption to gas consumption is to be optimized with regard to the minimum cost. When starting up, the individual parameters, such as steam pressure and blow-out temperature (s), through which the respective energy input is determined, are adopted, for example, from previous identical or similar production states. In the later course, the start value is the last saved value of the corresponding parameter. A first result of the total energy costs is now determined. Now the steam pressure is reduced by one step and at the same time the blow-out temperature is increased by one step, so that the overall change is production-neutral. The choice of whether to increase or decrease a parameter can also be made dependent on the energy cost situation, i.e. with high steam costs, the steam pressure is reduced, with high gas or. The oil temperature will reduce the outflow temperature. After the change has been made, the parameters are changed in the same direction or in the opposite direction, depending on the change in the parameters and the result (better / bad). Was e.g. the steam pressure increases and the discharge temperature decreases, follow the left arrow of the 1st query. Was the result successful, i.e. If lower energy costs were achieved, the left arrow is also followed in the second query and the parameters are changed again by one step in the same way. If the result was unsuccessful, i.e. the energy costs have been increased, so you follow the right row in the 2nd query and the parameters are changed in the opposite direction. The step size of the change can now also be reduced here, since it is assumed that the cost minimum is between the last two values and a change by the same step sizes would only lead back to the previous result. After changing the parameters, a certain waiting time is observed to wait for the response time of the adjustment processes. If a new cost value results within given limits, the ratio of two other energy flows, e.g. electrical energy (air blowing speed) and gas (blow-out temperature), while maintaining the already achieved ratio of steam energy to gas or oil energy use. This continues until a cost minimum is reached here too. The ratio of steam energy to gas or Oil energy optimized. The invention is not restricted to the examples. Rather, the drying in a multi-cylinder paper machine can also be regulated. Here, even with constant specific energy costs, cost optimization can be increased by optimizing the individual energy flows in the individual as well. Dry groups can be reached. Other drying processes such as Infrared drying can be integrated into the control. 1. Process for controlling and / or regulating a drying process for paper drying, in which different energy flows are supplied, these individual energy flows being variable, characterized in that the consumption of the individual energy flows is measured continuously and at least two energy flows are changed in such a way that none Change in the production state takes place, with at least one other energy flow being amplified to such an extent that the drying remains the same overall when reducing an energy flow. 2. The method according to claim 1, characterized in that the change in the energy flows takes place step by step and determines the total energy costs after each step and from this the step change for the next step is determined. 3. The method according to claim 1 or 2, characterized in that the energy flow is reduced with the highest energy costs. 4. The method according to claim 3, characterized in that the energy flow with the next highest energy costs is subsequently reduced. 5. The method according to any one of claims 1 to 4, characterized in that the costs or the specific costs per unit of energy of the individual energy flows are variable and are continuously specified for the regulation of the energy flows. 6. The method according to claim 5, characterized in that the current specific costs of the individual energy flows continuously taken directly from a connected process control system, another 5 AT 404 641 B in-house computer system or a database and are specified for the regulation of the ratio of the energy flows. 7. The method according to any one of claims 1 to 6, characterized in that the individual energy flows through different forms of energy, such as. Steam, oil, gas, el. Energy are generated. 8. The method according to any one of claims 1 to 7, characterized in that with a predetermined change in the production state, i.e. of the total energy requirement, all energy flows are changed evenly in the existing ratio. 9. The method according to any one of claims 1 to 7, characterized in that with a predetermined change in the production state, i.e. of the total energy requirement, if the demand increases, the energy flow with the lowest costs first, or if the demand decreases, the energy flow with the highest costs is changed first. 10. The method according to any one of claims 1 to 7, characterized in that when changing the production and / or the cost of the individual energy flows, the ratio of the individual energy flows according to the settings when the cost minimum is reached with the same or similar production parameters / energy costs of previous production states as Start value is set and then regulated. 11. The method according to any one of claims 1 to 10, characterized in that a further energy flow is changed when the minimum cost or a barrier of one of the regulated energy flows is reached. 12. The method according to any one of claims 1 to 11, characterized in that first two types of energy are varied and further types of energy are varied after reaching the minimum cost until the total minimum cost is reached. 13. The method according to any one of claims 1 to 12, characterized in that the step size of the change in energy flows is increased or decreased in accordance with the changes in the result. 14. The method according to any one of claims 1 to 13, characterized in that the change in energy flows is adapted to the response time of the corresponding adjustment processes. 15. System for controlling and / or regulating a drying process for paper drying, with a dryer to which the drying energy is supplied via different energy flows, characterized in that an optimization system is connected to the process control system to achieve and regulate a desired product quality, with measuring devices for detecting the quantities of the individual energy flows and devices for regulating these energy flows are provided. 16. System according to claim 15, characterized in that the optimization system consists of a control unit with signal detection and an optimization computer for varying the energy flows depending on the result of the previous change in the energy flows. Including 2 sheets of drawings 6