Method for controlling operation of a blast furnace

Abstract: A method for controlling heat conditions in a blast furnace (32) wherein the heat conditions are inferred and judged in comparison of data output from sensor means (11) provided for the blast furnace with knowledge base means (21) (22) formed by accumulated experience on the operation of the blast furnace. The heat conditions are inferred and judged from levels of heat conditions and from levels of transition of heat conditions, wherein data regarding molten metal temperature and those regarding sensors are used. The inference and judgement are carried out by inference engine means (24) included in a small-scale computer (20).

Description: The present invention relates to a method for controlling operation of a blast furnace, and more particularly, to a method for controlling heat conditions in the operation, based on information output from sensor means provided for the blast furnace. It is well-known, as a method for controlling temperature of molten metal tapped out of a blast furnace, by means of estimation of the temperature, to persons in the art, that operational factors are controlled to optimum, by means of evaluating furnace operation conditions, on the basis of qualitative judgement on information output from sensor means provided for the blast furnace. Japanese Examined Patent Publication (KOKOKU) No. 30007/76, for example, describes a method for controlling blast furnace operation, wherein, in order to carry out optimum operation by means of amending a long cycle change appearing during computer control of blast furnace operation condition, heat balance of the blast furnace operation is controlled by means of humidity of blast air blown in through tuyeres. The humidity is determined by an equation modified by an amendment member of preventing Si-content in molten metal from making a long cycle change. The amendment member is determined by an amount of direct reduction computed from measured values which are continuously obtainable during the blast furnace operation. This method, however, is disadvantageous in that it requires an analysis model to be maintained by means of modification thereto in compliance with the changes the blast furnace undergoes through its life. In addition, the modification itself is quite a time-consuming and complicated task, as the analysis model is quite complex. US-A-4 248 625 describes a method of operating a blast furnace comprising the steps of selecting eight factors mathematically and statistically as effective in determining the operating condition of a blast furnace, sensing the eight factors as sample data, converting the sample data into variable factors, comparing the sample data and the variable factors with predetermined limiting factors, generating numerical non-dimension values corresponding to the level of satisfaction between the sample data or variable factors and the corresponding limiting values, multiplying the numerical non-dimensional values by predetermined corresponding weight allocation indices, summing separately the results of the multiplication for the sample data and the variable factors to form a numerical factor grand addition output and a variable factors grand addition output, summing the numerical factors grand addition output and the variable factors grand addition output to form an overall grand addition output and taking appropriate action to control the furnace based upon the values of the overall grand addition output, numerical factors and variable factors grand addition outputs and the numerical non-dimensional values. The article in IECON 1984, Vol. 2, 1984, pp. 883-888, Tokyo, Japan entitled "An automatic diagnosing system for the blast furnace operating conditions" by Saito et. alia describes a method of estimating the conditions inside a blast furnace. The inputs of sensors are analysed statistically (indexing) to obtain spatial and temporal indexes, i.e. indication of changes from reference values. The indexes are then ranked based on operator knowledge to obtain fuzzy sets. Based on the ranking, judgements can be made. It is an object of the present invention to provide a method for controlling heat conditions in blast furnace operation, wherein an analysis model can easily be modified in compliance with the changes of the blast furnace undergoes during its life. The object is solved by a method for controlling operation of a blast furnace, wherein the blast furnace includes sensor means which outputs first data, corresponding to conditions in said blast furnace, which method comprises the steps of: supplying a central processing unit with said first data outputted from said sensor means, and storing standard data corresponding to predetermined values of data corresponding to said conditions in said blast furnace; preparing true-and-false data by comparing said first data with said standard data; storing information on operation and control characteristics of said blast furnace based on accumulated actual knowledge and experience of at least one operator of said blast furnace, said information being stored as data in a knowledge base means; inferring and judging heat conditions in said blast furnace, on the basis of said true-and-false data and said data in said knowledge base means and formed by accumulated experience on the operation of the blast furnace; and controlling heat conditions in the blast furnace in accordance with results of said inferring and judging step. Preferred embodiments are shown in claims 2-16. Fig. 1 is a schematic representation illustrating a method for controlling heat conditions in a blast furnace according to the present invention; Fig. 2 is a schematic block representation showing an apparatus for performing the method of the present invention; Fig. 3 is a flow diagram showing the method of the present invention. Fig. 4 is a flow diagram showing inference and judgement process according to the method of the present invention; Fig. 5 is a flow representation showing a step method of judging levels of heat conditions in the blast furnace according to the present invention; Fig. 6 is a flow representation showing a step method of judging levels of transition of heat conditions in the blast furnace according to the present invention; and Fig. 7 is a graphic representation showing an example of the results of the blast furnace operation according to the present invention. An enbodiment according to the present invention will now be described, with reference to Figs. 1 to 4. Fig. 1 schematically represents a method for controlling heat conditions in a blast furnace according to the present invention. Reference numeral 10 denotes a large-scale computer. Computer 10 includes sequential processing means 12 which processes sequentially the data output from sensor means 11, sequential filing means 13, sensor-data processing means 14 and interface buffer means 15. Reference numeral 20 denotes a small-scale computer, which includes knowledge base means 21 for judging heat conditions of the blast furnace, knowledge base means 22 for judging actions in response to the heat conditions, common data buffer means 23 and inference engine means 24. Reference numeral 30 denotes a cathode ray tube (CRT), which displays the results calculated by the inference engine means. Reference numeral 31 denotes control devices which control heat conditions in the blast furnace. Fig. 2 schematically illustrates an apparatus for performing the method according to the present invention. Reference numerals 11a, 11b and 11c each indicate sensors corresponding to sensor means 11 shown in Fig. 1. Large-scale computer 10 includes the following devices: 41: interface 42: computer processing unit (CPU) 43: read only memory (ROM) storing program 44 and 45: random access memories (RAMs); and 46: interface CPU 42 and ROM 43, which store the programs to be executed by CPU 42, constitute sequential processing means 13 and sensor-data processing means 14, both shown in Fig. 1. RAM 44 constitutes sequential filing means 13 shown in Fig. 1. RAM 45 temporarily stores the data output from sensor means 11. RAM 45 and interface 46 constitute interface buffer means 15 shown in Fig. 1. In Fig. 2, small-scale computer 20 includes key board 47, interface 48, CPU 49, ROM 50, RAMs 51 to 53 and interface 54. CPU 49 and ROM 50, which store the programs to be executed by CPU 49, constitute inference engine means 24 shown in Fig. 1. RAMs 51 and 52 constitute, respectively, knowledge base means 22 and 23 also shown in Fig. 1. RAMs 51 and 52 can be altered by operating key-board 47. New data can be added to this data by inputting the new data by means of key-board 47 via interface 48. RAM 53 constitutes common data buffer means 23 as shown in Fig. 1. The data stored in RAM45 of large-scale computer 10 is transferred to RAM 53 via interface 46. The results obtained by CPU 49 are supplied to CRT 30, through interface 54 and are displayed. The operation of this embodiment according to the present invention will now be described, in conjunction with the flow diagram shown in Fig. 3. (1) Firstly, the first data output from sensor means 11 are read in a predetermined sequence by sequential processing means 12, and then stored in sequential filing means 13 (STEP 1). Actually, this work is completed by supplying the first data from sensors 11a, 11b, 11c and so forth to RAM 44, through interface 41, under the control of CPU 42. (2) The first data stored in sequential filing means 13 are processed by CPU 42, thereby forming second data showing operation conditions of the blast furnace. This processing step produces data showing a rate of change, comparison of levels, dispersion of values and integral values of the first data within a designated time interval. This work is actually carried out (STEP 2). (3) The second data obtained in STEP 2 are compared with standard data, thereby providing true-and-false data. The true-and-false data are stored in interface buffer means 15. More specifically, the data are stored in RAM 45 shown in Fig. 2 (STEP 3). (4) The true-and-false data stored in interface buffer means 15 are transfered to common data buffer means 23 (STEP 4). More precisely, the data stored in RAM 45 are transfered, through interface 46, to RAM 53. (5) Inference engine means 24 infers heat conditions in the blast furnace, based on the data stored in knowledge base means 21 and knowledge base means 22, and on the true-and-false data stored in common data buffer means 23 (STEP 5). This work is achieved as CPU 49 executes the programs, designated by the data stored in RAMs 51 and 52, and in RAM 53. Knowledge base means 22 is composed of knowledge units necessary for judging levels of furnace heat conditions, judging levels of transition of the furnace heat conditions, judging actions and amending the actions so as to infer efficiently. Each of those knowledge units indicates an operator's knowledge and experience on the controlling production process, in the form of "If ..., then ....". In this embodiment, the reliability of inference is raised by introducing to inference process a certainty factor (CF) value, which indicates the uncertainty degree of each rule for the operating production process. With reference to Fig. 4, inference engine means 24, firstly judges levels of furnace heat conditions and levels of transition of the furnace heat conditions, and then, judges amount of actions, based on the results of the preceeding judgements. Further, inference engine means 24 amends the amount of actions. (6) Subsequently, the amount of actions amended in STEP 5 is supplied, via interface 54, to CRT 30, and is displayed. At the same time, the amended amount is transferred to control devices 31, the humidity of blast air to be blown into the blast furnace being controlled. (7) Then, it is determined whether stop signal has been given or not. If "YES", the processing is stopped. If "NOT", it returns to STEP 1 (STEP 7). In the latter case, the aforementioned STEPs 1 to 7 are repeated at predetermined intervals of, for example, 2 minutes. With specific reference to Fig. 5, process of judging levels of heat conditions in a blast furnace will now be explained in detail. Knowledge units stored in knowledge base means 21 contain rules for molten metal temperature (KS-101, 102), rules for sensors (KS-103 to KS-108) and human judgement rules (KS-109, 110), as those for the controlling production process. (a) Rules for molten metal temperature These rules are for judging present levels of furnace heat conditions from present molten metal temperature. A rule for molten metal temperature, KS-101 judges furnace heat conditions, based on experiences statistically accumulated in the past operation of a blast furnace. A rule for molten metal temperature, KS-102 judges levels of furnace heat conditions by means of estimating the highest temperature of molten metal presently tapped out. This estimation is based on statistic calculation of the latest n pieces of molten metal temperature measured. Certainty factor (CF) values, CF-101 and CF-102, each, are obtained from rules for molten metal temperature KS-101 and KS-102, each. The rules of KS-101 and KS-102 are given weights. In this weighting, for example, v₁ is given to KS-101, and V₂ to KS-102. The sum of v₁ plus v₂ is set to be 1. A judgement value for levels of furnace heat conditions, CF-120 is obtained, in consideration of the weights of v₁ and v₂, from CF-101 and CF-102. (b) Rules for sensors Among these rules, there are tuyere nose temperature rule 103, a burden descent speed rule 104, a furnace top gas temperature rule 105, a gas utilization rule 106, a solution loss amount rule 107, and a pressure rule for air blown into a blast furnace 108. A certainty factor (CF) value is taken into consideration for each of the rules of 103 to 108. Weights of v₃, v₄, v₅, v₆, v₇ and v₈ are also given to the rules, each, and the sum of v₃ to v₈ equals 1. A judgement value for levels of furnace heat conditions, CF-130 is obtained, in consideration of the weights of v₃ to v₈, from CF-103 to CF-108. (c) Human judgement rules These rules includes a tuyere condition rule and a slag color rule. The tuyere condition rule inputs one selected from the items consisting of "as previously set", "obscure" "good", "ordinary" and "bad" (judgement on levels of furnace heat conditions CF-109). Similarly, the slag color rule inputs one selected from the items consisting of "as previously set", "obscure", "color number 1 to 5: (1; good, 2; ordinary, and 3 to 5; "bad") (judgement on levels of furnace heat conditions, CF-110). A judgement on levels of furnace heat conditions, CF-140 of certainty factor values is obtained, in consideration of the levels of CF-109 and CF-110. Each of the items ranks grades 1 to 7. Consequently, the judgement on each of the levels are determined by combination of items with grades, according to the matrix as shown in Table 1. (d) Judgement on levels of furnace heat conditions A certainty factor value (CF-150), as a sum of each level of furnace heat conditions, is judged from CF-120 drawn out of the rules for molten metal temperature, and from CF-130 out of the rules for sensors. In this judgement, CF-120 and CF-130 are given weights of V₁ and V₂. The sum of V₁ and V₂ equals 1. Thus, a judgement on levels of furnace heat conditions, CF-150 of certainty factor values, is obtained, in consideration of the weights of V₁ and V₂ as shown in Table 2. In this case, the levels of furnace conditions are composed of those 1 to 7. For example, when certainty factor value (CF-1) of levels of furnace conditions "1" (Extraordinarily Cooled) or "2" (Most Cooled) is a predetermined value, Wx or over, a human judgement rule is applied, wherein CF value for each of levels 1 to 7 for furnace heat conditions (a judgement on levels of furnace heat conditions CF-106) is taken into consideration. For the purpose of judgement on levels of furnace heat conditions, knowledge units are classified into three categories, i.e., rules for molten metal temperature, those for sensors and those for human judgement, by reason of the following: 1. Object of control, itself is molten metal temperature; 2. The molten metal temperature can be detected, by nature, approximately every 20th minute at best. The treatment of the information is different from that of the information output from sensors, since the sensors can gather information data every minute; 3. The molten metal temperature starts with low temperature, due to hearth bottom and troughs of a blast furnace being cooled, and increases gradually. Consequently, when the highest molten metal temperature in a tap, for example, is to be controlled, levels of furnace heat conditions must be judged, these additional affecting factors being taken into consideration; 4. When operation is successful, the behavior of the molten metal temperature and the work of sensors are correlated though there is time delay. But, when, for example, molten slag within the blast furnace increases in volume, thereby distribution of top gas being peripherally prevailed, the correlation between the behavior and the work becomes reverse. In this case, it is preferable to judge the levels of furnace heat conditions, separately based on rules for molten metal temperature and rules for sensors, each. 5. Human judgement rules are composed of two rules. In the case of operation being abnormal, it is recommendable to use the two rules separately. This easily enables certainty factor values for the abnormal conditions to be strengthened, and information unobtainable through sensor means to be grasped so as to decide an optimum action in response. Of course, in the case of operation being normal, automatic control is principally employed without use of human judgement. As shown in Fig. 6, for judgement on levels of transition of heat conditions in the blast furnace, knowledge units stored in knowledge base means 22 contain rules for molten metal temperature (KS-201, -202), rules for sensors (KS-203 to KS-208) and the other rules (KS-209, 210), as those for the controlling production process. Those rules take into consideration certainty factor (CF) values of C1 to C5, each, as shown in Table 3. (a) Rules for molten metal temperature These rules for molten metal temperature are a rule for comparison of the latest temperature of molten metal with the highest molten metal temperature in a previous tap (KS-201), and a rule for comparison of the high molten metal temperature in a previous tap with the hightest molten metal temperature in a tap immediatly before the previous tap. (b) Rules for sensors Among these rules, there are a tuyere nose temperature rule, a burden descent speed rule, an pressure rule for air blown into a blast furnace, a gas utilization rule, a solution loss amount rule and a furnace top gas temperature rule. CF values (CF-203 to CF-208), each, are taken into consideration for the rules. The CF values rank five grades as well. (c) The other rules The other rules are a rule for transition of contents of silicon and sulfur (KS-209) and a rule for index of furnace conditions (KS-210). CF values (CF-209, -210), each, are taken into consideration for the rules. (d) Judgement on levels of transition of furnace heat conditions In the case of the rules for molten metal temperature, the rules of KS-201 and KS-202 are given, respectively, weights of W₁ and W₂. The sum of the weights equals 1. A judgement on levels of transition of heat conditions in the blast furnace, CF-220 is obtained, in consideration of the weights, from CF-201 and CF-202. Similarly, the rules of KS-203 to KS-210 are given, respectively, weights of w₃, w₄, w₅, w₆, w₇, w₈, w₉ and w₁₀, and the sum of the weights of w₃ to w₁₀ is 1. A judgement on levels of transition of heat conditions in the blast furnace, CF-230 is obtained, in consideration of the weights, from CF-203 to CF-210. And then, a CF value (CF-240) of levels of transition of heat conditions in the blast furnace for each of five grades, is obtained by summing CF values of CF-220 and CF-230. Based on CF values for levels of furnace heat conditions (L1 to L7) and for levels of transition of furnace heat conditions (C₁ to C₅) obtained in such a manner as described in the above, amount of actions is judged as shown in Table 4. A CF value represented by "a ij " is given by the following formula: a ij = CF value for grade i of Furnace Heat Conditions x CF value for grade j of Transition of furnace Heat Conditions "a ij " thus obtained corresponds to amount of actions shown in Table 5. CF values for amount of actions shown in Table 4 are obtained by the afore-mentioned formula. However, if each CF value for levels of furnace heat conditions, or for levels of transition of furnace heat conditions is less than a predetermined value, it is desirable to count such a CF value as zero. In addition, if a CF value for amount of actions shown in Table 4 is more than a predetermined value, it is recommendable that amount of actions is output so as to make CF values in order of numbers small to large for operation guide. And, if the same action is output in plurality, it is recommendable that the largest CF value is to be displayed to an operator. An action amount, based on judgement on action; is amended when effect to sensors or furnace heat conditions by an action already taken or an additional affecting factor still remains. As such an additonal affecting factor, drop of unreduced ore and sudden change of coke moisture are considered. Actions and amount of actions are shown in Table 6 below: All actions are converted in amount to moisture action. According to the present invention, true-and-false data are prepared on the basis of the data output from sensor means 11 provided for a blast furnace, and then, inference, as an artificial inteligence, is carried out in comparison of the true-and-false data with knowledge base formed by accumulated experiences on the operation of the blast furnace. This gives advantages in that, (a) experience on the past operation can be made full use of, (b) a small capacity of computer processing units can be used, and (c) response to the changes the blast furnace undergoes during its life can easily be attained. Example Control of heat conditions was carried out for 20 days, employing a blast furnace with 4664 m³ inner volume, according to a method of the present invention. Judgements on furnace heat conditions were made every 20th minute and actions were instructed, based on the results of the judgements. An example of the above operation results is shown in Fig. 7. The operation of the blast furnace was carried out with air blast of 6,500 Nm³/min. and at a coke ratio of 514 kg/T-pig. Changes of typical data output from the sensor means, the results of judgement on levels of furnace heat conditions and the results of judgement on transition of levels of furnace conditions are illustrated in Fig. 7. Operational action in response to furnace heat conditions was carried out by means of controlling amount of steam. The amount of steam represented by a broken line is in compliance with instructions obtained from judgements on actions, and that of steam by a solid line, in compliance with actual actions. Actions of increasing amount of steam (a₁, a₂, a₃ and a₄), and actions of decreasing amount of steam (b₁, b₂, b₃ and b₄) were instructed, in accordance with judgements on actions. Actions of a₁, a₂, a₄, b₁, b₂ and b₄ were actually taken. The highest molten metal temperature representing a tap, was approximately 1500°C. The dispersion of molten metal temperatures was reduced from 9.16°C to 6.24°C by application of the present invention to control of furnace heat conditions. The range (maximum value minus minimum value) of molten metal temperatures was also reduced from 24.2°C to 14.3°C.

Claims: A method for controlling operation of a blast furnace, wherein the blast furnace includes sensor means which outputs first data, corresponding to conditions in said blast furnace, which method comprises the steps of: supplying a central processing unit with said first data outputted from said sensor means, and storing standard data corresponding to predetermined values of data corresponding to said conditions in said blast furnace; preparing true-and-false data by comparing said first data with said standard data; storing information on operation and control characteristics of said blast furnace based on accumulated actual knowledge and experience of at least one operator of said blast furnace, said information being stored as data in a knowledge base means; inferring and judging heat conditions in said blast furnace, on the basis of said true-and-false data and said data in said knowledge base means and formed by accumulated experience on the operation of the blast furnace; and controlling heat conditions in the blast furnace in accordance with results of said inferring and judging step. A method according to claim 1, characterized in that said step of inferring and judging heat conditions in the blast furnace includes inferring and judging levels of heat conditions in the blast furnace. A method according to claim 1 or 2, characterized in that said step of inferring and judging levels of heat conditions includes inferring and judging levels of the heat conditions, from molten metal temperature. A method according to claim 2 or 3, characterized in that said step of inferring and judging levels of heat conditions includes inferring and judging levels of heat conditions, based on data output from the sensor means provided for the blast furnace. A method according to claim 2, 3 or 4, characterized in that said step of inferring and judging levels of heat conditions includes inferring and judging levels of heat conditions, based on tuyere condition and slag colour. A method according to claim 4, characterized in that said inference and judgement, based on data output from the sensor means includes inferring and judging, based on at least one selected from the group consisting of: (a) data representing tuyere nose temperature; (b) data representing burden descent speed; (c) data representing blast air pressure blown into the blast furnace; (d) data representing gas utilisation ratio; (e) data representing solution loss amount pressure; and (f) data representing furnace top gas temperature. A method according to claim 1, characterized in that said step of inferring and judging heat conditions in the blast furnace includes inferring and judging levels of transition of heat conditions in the blast furnace. A method according to claim 7, characterized in that said step of inferring and judging levels of transition of heat conditions includes inferring and judging levels of transition of heat conditions, from molten metal temperature. A method according to claim 7 or 8, characterized in that said step of inferring and judging levels of transition of heat conditions includes inferring and judging levels of transition of heat conditions, based on data output from the sensor means provided for the blast furnace. A method according to claim 7, 8 or 9, characterized in that said step of inferring and judging levels of transition of heat condition, based on Si and S content in the molten metal. A method according to claim 9, characterized in that said inference and judgement, based on data output from the sensor means includes inferring and judging, based on at least one selected from the group consisting of: (a) data representing tuyere nose temperature; (b) data representing burden descent speed; (c) data representing blast air pressure blown into the blast furnace; (d) data representing gas utilisation ratio; (e) data representing solution loss amount pressure; and (f) data representing furnace top gas temperature. A method according to claim 1, characterized in that said step of inferring and judging heat conditions in the blast furnace includes inferring and judging levels of heat conditions, and inferring and judging levels of transition of heat conditions. A method according to claim 1, characterized by further comprising a step of processing data output from the sensor means. A method according to claim 1, characterized in that said step of inferring and judging heat conditions in the blast furnace includes taking certainty factor values into consideration. A method according to claim 1, characterized in that said step of controlling heat conditions in the blast furnace operation includes judging action amount from the results of judgement on level of furnace heat conditions and from the results of judgement on transition of furnace heat conditions. A method according to claim 15, characterized in that said action amount includes being amended, in consideration of effect by an action already taken and an additional affecting factor.

Inventors: ISHII TAKAHARU PATENT LICENCE, SAKURAI MASAAKI PATENT LICENCE, SHIBATA MOTOHIRO PATENT LICENC, WAKIMOTO KAZUMASA PATENT LICEN, ISHII, TAKAHARU PATENT & LICENCE AND, SAKURAI, MASAAKI PATENT & LICENCE AND, SHIBATA, MOTOHIRO PATENT & LICENCE AND, WAKIMOTO, KAZUMASA PATENT & LICENCE AND, Ishii, Takaharu Patent &amp; Licence and, Sakurai, Masaaki Patent &amp; Licence and, Shibata, Motohiro Patent &amp; Licence and, Wakimoto, Kazumasa Patent &amp; Licence and
Applicants: NIPPON KOKAN KK, NIPPON KOKAN KABUSHIKI KAISHA
Application year: 1987
Main classification: C21B5
IPC codes: C21B7, C21B5