EP1593090A2

EP1593090A2 - Multivariate, predictive regulation of a direct reduction process

Info

Publication number: EP1593090A2
Application number: EP04709993A
Authority: EP
Inventors: Franz GÖRNER; Bernhard Lang; Stephen Craig Montague
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2003-02-13
Filing date: 2004-02-11
Publication date: 2005-11-09
Anticipated expiration: 2024-02-11
Also published as: EP1593090B1; US20060149694A1; DE502004009504D1; RU2005128510A; RU2346327C2; DE10306024B3; ATE431952T1; WO2004072309A3; US7634451B2; MXPA05008624A; WO2004072309A2

Abstract

A property is measured for each of several products to be made at different points in time and from these measurements, the value of the product property is postulated. This is taken into consideration by determining a value for an input neurone of a neural network. Using the neural network, the property of the product to be manufactured is predicted. Independent claims are included for the following ; (1) plant; and (2) computer program product.

Description

description

Multivariate, predictive control of a direct reduction process

The direct reduction of iron ore to the product sponge iron in the form of DRI (Direct Reduced Iron) or HBI (Hot Briquetted Iron) preferably takes place in a shaft furnace using heated process gases. Put simply, chemical reactions occur that convert iron ore (Fe2θ3) and natural gas (CH4) into iron Fe, carbon dioxide CO2 and water H2O.

The shaft furnace is operated continuously by continuously adding raw material in the form of iron ore pellets from above and also continuously removing the sponge iron from below.

Methods for producing sponge iron are known for example from US 4,093,455, US 4,178,151, US 4,234,169 and WO 02/097138 AI. Further publications on this are Thompson, M.: "Control Innovations in MIDREX Plants: An Introduction" in "Direct from MIDREX", Ist Quarter 2001, pp. 3-4, 2001 and Görner, F., Bacon, F .: "Development of Process Automation for the MIDREX Process "in" Direct from MIDREX ", Ist Quarter 2002, pp. 3-5, 2002.

In the production of sponge iron, it is desirable to produce a product with as constant and precisely specified properties as possible. For this purpose, it is known to keep all influencing factors for the product sponge iron as constant as possible and thus to operate the process at a known working point. However, the assumption of a completely homogeneous iron ore as raw material is often not fulfilled in practice. Proceeding from this, the object of the invention is to predict a property of a product to be produced, in particular sponge iron produced by direct reduction.

This object is achieved by the inventions specified in the independent claims. Advantageous refinements result from the subclaims.

The inventions are based on the general idea of taking the product history into account when forecasting a value of a property to be predicted with the aid of a neural network, in that values are included in the forecast which have the property to be predicted in the case of products which have already been produced. Such values can be taken into account when determining an input variable of the neural network. Alternatively or in addition, it is also possible, when determining the same input variable or another input variable of the neural network, to take into account the difference between a value of the property measured at a specific point in time and a value of the property predicted for this point in time.

Correspondingly, in a method, in particular a manufacturing method, a value of a property of a product to be manufactured in the present and / or in the future, in particular measurable in the future, is predicted with the aid of a neural network. A value of the property, be it completely or with the aid of random samples, is measured for several products manufactured at different times in the past. The value of the property of the product to be manufactured in the present and / or future is then predicted from the values of the property measured for the times in the past in a pre-forecast. It is, so to speak a forecast of the impure, in which essentially only the values of the property measured for the times in the past are included.

This value predicted in the pre-forecast is taken into account when determining an input variable for an input neuron of the neural network. With the help of the neural network, the value of the property of the product to be manufactured in the present and / or future is finally predicted in the actual forecast.

The pre-forecast can preferably be made using a recursive filter. The recursive filter can be implemented relatively easily by doing a linear projection. More precise forecasts are possible by using a second neural network as a recursive filter, in particular a recurrent neural network. An additional mathematical description of the cause-effect relationship between the process parameters and the property is useful.

To determine an input variable of the neural network, a comparison between a value of the property measured for a point in time in the past and a value of the property predicted for this point in time can also be taken into account when determining an input variable for the neural network.

Accordingly, a prognosis of a value of a property of a product to be manufactured in the present and / or in the future, which can only be measured in the future, is carried out with the aid of a neural network. For this purpose, a value of the property is measured for a product manufactured at a certain point in time. Furthermore, a value of the property in the product manufactured at that point in time is predicted with the forecast. To do this, the forecast for the past must be chosen at random or sensible values can be initialized from an even more recent past. Then the difference between the measured and the predicted value of the property of the product at that time is formed. This difference is then used to determine an input variable for an input neuron of the neural network. With the help of the neural network, the value of the property of the product to be manufactured in the present and / or future is finally predicted in the forecast.

The goal of a good forecast is to intelligently control the manufacturing process of the product. In the method or by the method, therefore, parameters in the manufacturing process of the product to be manufactured are preferably changed until the value predicted in the prognosis of the property of the product to be manufactured corresponds at least approximately to a desired value of the property of the product to be manufactured.

Although the described method is generally suitable for all possible products, it is particularly relevant for those products whose properties cannot be measured during their manufacture or shortly afterwards, but only after a delay of possibly several hours. The method can be used particularly advantageously in continuous production processes.

The prediction method described is particularly suitable for the prediction of properties of sponge iron produced in the direct reduction method. Accordingly, the property can consist of one or more of the following quantities:

- The degree of metallization, i.e. the ratio between the absolute iron content in the iron ore and the released iron (Fe),

- the proportion by weight of the sponge iron, which is present as metallic iron (Fe), - the carbon content in the sponge iron.

Of course, it is within the scope of the invention to use the forecasting method to forecast not only one property but several properties of the product to be manufactured.

When forecasting with the help of the neural network, in addition to the history of the products that have already been manufactured, other parameters in the manufacturing process of the product to be manufactured should also be taken into account by influencing or representing input variables of input neurons of the neural network. Such parameters are in particular process temperatures, gas compositions of process gases used and / or properties of raw materials.

The invention further relates to an arrangement which is set up to carry out one of the aforementioned methods. Such an arrangement can be implemented, for example, by programming and setting up a computer or a computer system. A direct reduction system can also be part of the arrangement, in particular with a shaft furnace.

A program product for a data processing system, which contains code sections with which one of the described methods can be carried out on the data processing system, can be implemented by suitable implementation of the method in a programming language and translation into code executable by the data processing system. The code sections are saved for this purpose. A program product is understood to mean the program as a tradable product. It can be in any form, for example on paper, a computer-readable data medium or distributed over a network. Further essential advantages and features of the invention result from the description of an embodiment with reference to the drawing. It shows:

Figure 1 shows a shaft furnace for the production of sponge iron;

FIG. 2 shows a preliminary forecast of a value of a property of a product to be manufactured on the basis of values of the properties of products that have already been manufactured.

FIG. 3 shows a prediction of a value of a property of a product to be produced on the basis of a measured value of the property in the case of a product which has already been produced and a predicted value of the property in the case of this product which has already been produced.

FIG. 1 shows a shaft furnace 1 with a feed 2 for feeding iron ore pellets, which accumulate in one or more piles 3 inside the shaft furnace 1. The shaft furnace 1 also has means 4 for supplying reaction gases, in particular hydrogen and carbon monoxide, and means 5 for removing reaction gases, in particular carbon dioxide and water.

Inside the shaft furnace 1, the iron ore is reduced in a direct reduction under high temperatures and under the influence of the process gases to sponge iron, which is removed at the lower end of the furnace via a removal device 6 and transported away via a conveyor belt 7.

At regular intervals, for example every two to four hours, samples are taken of cooled products and examined in the laboratory for the properties of metallization and carbon content. The time difference from the completion of the development process to the evaluated sample is approx. 5 to 9 hours for the metallization and approx. 3.5 to 7.5 hours when enriched with carbon. This is because the metallization is completed as a sub-process of the manufacturing process, for example in the middle of the shaft furnace 1. However, the product produced remains in the shaft furnace 1 for a further approximately 3 hours to cool down until it leaves it at its removal device 6. The carbon enrichment sub-process is complete after about three quarters of the time, ie after about 4.5 hours. It also takes about 2 hours in the laboratory to measure the value of the metallization and measure the value of the enrichment with carbon. Provided that the measurement is carried out approximately every 4 hours, there is a dead time of 5 to 9 or 3.5 to 7.5 hours.

This would allow control interventions to be carried out on the running process, provided that all influencing factors have remained constant. For the previous 3.5 to 9 hours of the process, there is no longer any possibility of intervention. In practice, it is also not possible for various reasons to keep all influencing factors constant.

In FIG. 2 it can be seen that the value W_3 of a property, that is to say, for example, the metallization or the carbon content, of the product at the time t_3 can only be measured at the time t_3 + 5 hours. The same applies analogously to the value _2 of the property of the product at the time t_2 and the value W_] _ of the product at the time t_] _, which can also be measured only 5 hours after production.

From the measured values W_3, _2 and W_ι, which, for example, indicate a metallization of 94.1%, 94.2% and 94.3%, the value W ^v p _{Q of} the property of the product to be manufactured in the current one is now made in a pre-forecast V Forecast time tg. In the shown in Figure 2 In the exemplary embodiment, this is done simply by linear extrapolation, which is indicated by the dashed line. However, more complicated algorithms can also be used here.

The value W ^V _Q predicted in the pre-forecast is now taken into account when determining an input variable for an input neuron of a neural network.

In addition, as shown in FIG. 3, the difference between a value W_ι_ measured for a point in time t_χ in the past and a value Wp_ι predicted for this point in time with the actual forecast P is also taken into account in a second pre-forecast V.

This is done using the formula:

W ^{v '} ₀ = W_χ + α • (W ^p _! - W_ι)

With = {0; 1}, for example α = 0.25.

This value W ^{v '} g of a second pre-prognosis, taking into account the difference between the measured value. ^ And the value W ^p _ of the property of the product predicted with the forecast, is now used as an input variable for a second input neuron of the neuronal Network.

The input variables of further input neurons of the neural network are formed by further process parameters or are calculated taking other process parameters into account. Such process parameters are:

- The gas composition of all process gases (dry and wet) that are used in the direct reduction system, - quantitative and temporal statements for gases regarding flow rates (e.g. tons per hour) and temperature,

- all temperature measurements in and on the shaft furnace,

- properties that describe the raw material (porosity, chemical composition, size and shape of the pellets, density, temperature),

- properties that describe the product manufactured or to be manufactured (density, chemical composition, carbon content, iron content, content of metallic iron, degree of metallization),

- Mass flows of the raw material and the end product as well

- Air (temperature and humidity over time).

Approximately 100 measured and calculated input variables are advantageously included in the model formation.

In the case of the neural network, it has proven to be particularly advantageous to use an ensemble of neural networks and to evaluate its media. A combination of feed-forward networks with recursive filters is also advantageous.

The following are examples of preferred training methods for the neural network: the use of digital filters for the training data, automatic outlier removal, bagging, compliance with boundary conditions for monotony with regard to relevant control variables and the target variables.

The input variables of the neural network are preferably modeled ^* analytically ^* from the process parameters mentioned. This is done, for example, through the integration of quantities, the quantitative description of chemical conversion including the reaction kinetics using differential equations and a calculation of when which piece of material is where in the shaft furnace, using the product output per hour. Various linked software programs in Fortran, C, C ++ and MATLAB are advantageously used for execution. A user interface can be programmed in Visual Basic.

The following advantages result from the invention:

- The deviation from specified target values can be reduced. In practice, the standard deviation is reduced by approx. 40% in the metallization and approx. 30% in the carbon content.

- Minor deviations allow the shaft furnace to operate closer to the optimum, which benefits throughput and quality.

- A production increase of approx. 1% is achieved.

- Due to the more constant and higher material quality, the customers of the sponge iron, namely operators of electric arc furnaces, can operate their furnaces more efficiently. This advantage has an even greater impact than the advantages of operating the direct reduction system, so that correspondingly higher prices can be achieved for the product manufactured.

- The calculation of the material properties can replace laboratory samples.

- The calculations can be carried out at any time. This means, for example, current values can be calculated every 0.1 seconds instead of being analyzed in the laboratory every two to four hours.

- Since significant .chemical reactions are already completed in the first half or first third of the process of approx. 6 hours, the

Material properties are determined before the sponge iron is removed from the shaft furnace. This shortens the response times for regulating the material properties from 3.5 to 9 hours to the calculation time for the models, which is less than 0.1 seconds.

Claims

claims

1. Method, in particular manufacturing method, for predicting a value of a property of a product to be manufactured with the help of a neural network,

a value of the property is measured for several products manufactured at different times,

in which the value of the property of the product to be manufactured is predicted in a pre-forecast from the values of the property measured for the points in time,

in which the value predicted in the pre-forecast is taken into account when determining an input variable for an input neuron of the neural network,

- where with the help of the neural network the value of. Property of the product to be manufactured is forecast in the forecast.

2. The method of claim 1, wherein the pre-forecast is made with the aid of a recursive filter.

3. The method according to claim 1 or 2, wherein the recursive filter is a linear projection and / or contains.

4. The method according to any one of the preceding claims, wherein the recursive filter is and / or contains a second neural network, in particular a recurrent neural network.

5. The method, in particular according to one of claims 1 to 4, for predicting a value of a property of a product to be manufactured with the aid of a neural network,

- in which a value of the property of a product manufactured at a time is measured, a value of the property of the product manufactured at that point in time is predicted with the forecast,

- at which the difference between the measured and the predicted value of the property of the product is formed at this time,

in which this difference is taken into account when determining an input variable for an input neuron of the neural network,

- In which the value of the property of the product to be manufactured is predicted in the forecast using the neural network.

6. The method according to any one of the preceding claims, in which parameters in the manufacturing process of the product to be manufactured are changed until the value predicted in the forecast of the property of the product to be manufactured corresponds at least approximately to a desired value of the property of the product to be manufactured.

7. The method according to any one of the preceding claims, in which the product to be produced is produced with the aid of a direct reduction.

8. The method according to any one of the preceding claims, wherein the product to be produced is sponge iron and / or contains.

9. The method according to any one of the preceding claims, wherein the property is the content of metallic iron in the product to be produced.

10. The method according to any one of the preceding claims, wherein the property is the carbon content of the product to be produced.

11. The method according to any one of the preceding claims, in which further parameters in the manufacturing process of the product to be produced are taken into account in the prognosis with the aid of the neural network, in particular process temperatures, gas compositions of process gases used, properties of raw materials and / or by analytical calculations of the chemical conversions and Reaction kinetics determined parameters.

12. An arrangement which is set up to carry out a method according to at least one of the preceding claims.

13. Program product that, if it is on a

Data processing system is loaded and executed on it, a method according to one of claims 1 to 11 or a device according to claim 12 in force.