DE19612155C2 - Method and system for controlling a drying process - Google Patents

Description

The invention relates to a method and a system for Regulation of a drying process in which various variable energy flows with associated individual energy consumption and specific energy flow costs while achieving a predefined drying result of a product to be dried, especially paper.

Such processes are used for example in paper drying used, the drying on the one hand by Contact drying using a steam heated cylinder and on the other hand by convection drying by inflating hot air occurs. Here, the temperature can also be caused by gas generated and the amount of air or blowing speed is controlled by a supply air fan with an electric drive generated.

There are various ways of regulating such a process Methods, the main aim being that the required quality in terms of dryness and surface quality the corresponding throughput is reached.

Above all, the machine speed or the Energy supply to steam (steam pressure, steam quantity) as well Controlled gas temperature.

At regular intervals, such as B. weekly or monthly, the energy consumed during this period and its Costs according to energy sources in corresponding reports compiled.

Most of the time there is no information about the specific Hit energy costs for a particular product. A Minimizing energy costs is practically impossible because Changes in operating mode usually have a strong impact the result, d. H. the dryness or the  Have throughput.

When the product quality to be produced changes at short notice and even with short-term changes in energy prices either through another operation of the company's own Power plant or due to changed electricity prices is one Minimization not feasible.

The invention has for its object a method and a System for the drying process for one to be dried To create product, especially paper, with which the Use of the individual energy flows or carriers optimized and the total energy costs are minimized.

This is done with a procedure or with a system as in the Claims 1 and 12 achieved. Preferred further developments of the Processes are described in claims 2 to 11.

By continuously measuring the respective feed Energy flow, whose current consumption value is also displayed can be, and from which the total energy costs continuously an automatic comparison can be displayed quickly different driving styles with regard to their economy and also achieved a quick reaction to changes be, the gradual change in the division a rapid approach to the minimum results without the danger again to get into areas of higher total energy costs.

This is a particularly favorable variant of the invention characterized in that at least two energy flows for changing the Ratio of the supplied energy flows can be changed. This will have all influences on the production and the Product quality excluded, so for a given Production state by dividing the energy supply individual energy flows are regulated to a minimum cost.

A further development of the invention is characterized in that that the current specific energy cost of each  Energy flows continuously for the calculation of the Individual energy costs are specified, the current specific energy costs directly from one connected process control system, an in-house Computer system or a database. specially when changes in the specific energy costs for the individual energy flows can be controlled by an ongoing practically at any time a minimum of drying costs be achieved. Are the current values from the connected Process control system or another internal computer system taken over, z. B. on the current energy costs individual energy flows from an internal power plant or on the energy flow costs used for billing be used. Will the energy electricity costs come from a Database extracted, z. B. in a simple manner regular changes in electricity prices due to day / night electricity or Summer / winter tariffs are taken into account.

The energy flows can be regulated particularly advantageously, when the individual energy flows through different Forms of energy such as B. steam, oil, gas, electrical energy, be generated. Are the individual energy flows through Different forms of energy can be generated cheaper total cost minimum can be achieved than at Change of energy flows with the same type of energy, whereby only the different drying efficiency due to the respective energy flow affects the energy costs.

This is an advantageous development of the invention characterized in that with a predetermined change in Drying result or state of production, d. H. of Total energy requirements, all energy flows in the existing one Ratio can be changed evenly. By such Changing energy flows is a quick approach to that new total cost guaranteed.

This is a favorable variant of the invention characterized in that with a predetermined change in  Drying result or state of production, d. H. of Total energy demand, first with an increase in demand the energy flow with the lowest direct energy costs or when the demand is reduced, the energy flow with the highest individual energy costs is changed. At a Such change in energy flows will occur in every step Direction to the new total cost minimum the most cost-effective Distribution of energy flows found.

A particularly advantageous development of the invention is characterized in that when production changes and / or the energy flow costs of the individual energy flows Ratio of the individual energy flows according to the Settings when the cost minimum is reached at the same or similar production parameters / energy costs from previous ones Drying results or production conditions as a starting value adjusted and then regulated.

If there is a change in production data such as B. Leaf weight or dry matter content leads to one significantly changed drying behavior and a strong changed energy requirements. It is therefore particularly advantageous if based on experience with similar drying results or production states is used because these most likely already close to what you’re looking for Total cost minimum. The same applies to one sudden change in the cost of individual energy sources, such as this z. B. when switching from day electricity tariff to night electricity tariff (and vice versa) is the case. Here, too, it turns out to be particularly cheap if based on experience with similar ones Parameters is used.

This is an advantageous embodiment of the invention characterized in that when the cost minimum or one barrier of one of the regulated energy flows another Energy flow is changed, being particularly favorable first two energy flows (energy flow types) varied and after Reaching the minimum cost of additional energy flows  can be varied until the total energy cost minimum is reached.

By doing this, system-related limits, such as z. B. maximum permissible air temperatures or vapor pressures, not exceeded or fallen short of as well as when a "optimal" ratio of two energy flows Total energy cost minimum for drying reached. It is particularly beneficial if the increment of change of energy flows according to the changes in energy total costs are increased or decreased. With that is through a larger change in the energy flows during the starting process or after a production change or Change in energy costs to find the optimal one quickly Distribution of energy flows possible. When settling on the optimal division can then be smaller increments can be used, thereby avoiding fluctuations in operation become.

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

The process control system is used to control a drying process in particular an optimization system connected. Through the Separation of process control system and optimization system can can be achieved that the production settings constant remain and only the distribution of the drying energy the individual energy flows and / or types of energy varies and is optimized in terms of minimizing costs. Furthermore can thereby maintaining the previous system and the Drying system, if necessary, also without an optimization system operate.

The optimization system consists in particular of one Control unit with signal acquisition and an optimization computer  to vary the energy flows to achieve a cost minimums exists. With such a configuration the signal acquisition and acquisition of the corresponding Energy flow data advantageous from the actual optimization separate so that even if the optimization computer fails trouble-free operation is possible, whereby by Manual control an approximation to the total cost minimum is possible.

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

Fig. 1 illustrates an example of a drying process with the use of different energy flows and types of tissue is a 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 online quality measurement 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 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 consumption 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. B. oil can be measured.

The measured consumption values are transmitted to the process control system 16 on the one hand, but also to the optimization system 23 on the other hand.

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 the current specific energy flow 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 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 through the process and quality control system 5 , 16 , 17 , 18 . The optimization starts with start values, e.g. B. can come from previous optimization processes.

All steps of minimizing costs become production-neutral, d. H. without changing the production status. To do this, another is reduced when one energy flow is reduced Energy flow, advantageous with another type of energy, so far reinforced that the drying remains the same overall.

For example, a reduction in the blow-out speed (electrical energy) by a corresponding increase the vapor pressure or the blown air temperature (gas or Oil energy) compensated.

After an optimization step has been completed, the energy costs 27 are compared with those of the previous state. 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. H. the minimum cost for the variation of Found both types of energy, the same will happen in quick succession performed with all parameters so that an optimized Overall result comes about.

By adaptively adapting the search steps, a larger adjustment can be done in a short time, which is a quick Locating the minimum cost when starting. At the Swinging to the optimum is based on smaller increments switched to avoid fluctuations in operation.

The system is advantageous with "fuzzy logic methods" supported, making it a self-learning system acts, whereby the optimization period until reaching the Cost minimum is significantly reduced.

Fig. 2 now represents the flow of control of the individual energy flows by way of example.

In a first step, the ratio of gas consumption to the consumption of electrical energy in terms of Cost minimums are optimized.

When starting, the individual parameters, such as Blow-out temperature (s) and blow-out speed (s) for example, from previous same or similar ones Production states adopted. In the later course is Start value the last saved value of the corresponding parameters.

It now becomes a first result of the total energy cost determined. Now the blow-out speed is one Increment and at the same time the blow-out temperature incremented so that the total change is production neutral.

The choice of whether to increase or decrease a parameter  can also be made dependent on the energy cost situation become, d. H. with high electrical energy costs Blow-out speed reduced, with high gas or oil costs the blow-out temperature is reduced.

After the change is made dependent on the change of Parameters and the result (better / worse) the parameters changed in the same direction or in the opposite direction.

Has z. B. increases the blow-out speed and the blow-out temperature decreases, follow the arrow of the 1st query. was the result is successful, d. H. were lower energy costs achieved, you also follow the arrow in the second query, and the parameters are increased by one in the same way Increment changed.

If the result was unsuccessful, i. H. the energy costs were increased, follow the arrow and the Parameters are changed in the opposite direction.

The step size of the change can now also be reduced here because it is assumed that the minimum cost is between the last two values and a change around the same increments only go back to the previous result would lead back.

After changing the parameters there will be a certain waiting time adhered to the response time of the adjustment processes to be seen.

If there is a new cost value within the specified one Bounds, the relationship between two other energy flows, z. B. steam and gas, while maintaining what has already been achieved Ratio of electrical energy to gas or oil changed. This continues until a cost minimum is reached here too is. Then the ratio of electrical optimized for gas or oil energy.  

The invention is not limited to the examples. It can rather drying at one Multi-cylinder paper machine can be regulated. Here in increasingly even with constant specific energy costs a cost optimization by optimizing the individual Energy flows also achieved in the individual drying groups become. Other drying processes such as. B. Infrared drying can be integrated into the control.

Claims (12)

1. A method for controlling a drying process in which different, variable energy flows with associated individual energy consumption and specific energy flow costs are achieved with a predetermined drying result, a product to be dried, in particular paper
the individual energy consumption of the respective supplied energy flow is continuously measured,
the associated individual energy costs of the energy flows are determined on the basis of the measured individual energy consumption and the specific energy flow costs, and the ratio of the supplied energy flows to one another is maintained step by step while maintaining the drying result, while minimizing the total energy costs, which are the sum of the individual energy costs. 2. The method according to claim 1, characterized in that at least two energy flows to change the ratio of the supplied energy flows are changed. 3. The method according to claim 1 or 2, characterized in that the current specific energy cost of each Energy flows continuously directly from a connected one Process control system, another in-house computer system or a database and used for the calculation of the Individual energy costs are specified. 4. The method according to any one of claims 1 to 3, characterized characterized in that the individual energy flows through different forms of energy, such as B. steam, oil, gas, electrical energy are generated. 5. The method according to any one of claims 1 to 4, characterized characterized in that with a predetermined change in Drying result of all energy flows in the existing one Ratio can be changed evenly.   6. The method according to any one of claims 1 to 4, characterized characterized in that with a predetermined change in Drying result with an increase in demand first the Energy flow with the lowest direct energy costs or at Reducing the need for energy flow with the first highest individual energy costs is changed. 7. The method according to any one of claims 1 to 4, characterized characterized in that when the production and / or the change Cost of each energy flow is the ratio of each Energy flows according to the settings when the Minimum costs for the same or similar production pair meters / energy costs from drying results earlier than Start value is set and then regulated. 8. The method according to any one of claims 1 to 7, characterized characterized in that when the cost minimum or a Barrier one of the regulated energy flows another Energy flow is changed. 9. The method according to any one of claims 1 to 8, characterized characterized that first two energy flows varied and after Reaching the cost minimum further energy flows varies until the total energy cost minimum is reached. 10. The method according to any one of claims 1 to 9, characterized characterized in that the increment of change in Energy flows according to the changes in the Total energy cost is increased or decreased. 11. The method according to any one of claims 1 to 10, characterized characterized in that the change in energy flows to the Response time of the corresponding adjustment processes is adjusted. 1. An apparatus for performing the method according to claim 1.