US-12624403-B2 - Optimal calculation method of energy operating condition in iron mill, optimal calculation device of energy operating condition in iron mill, and running method of iron mill

US12624403B2US 12624403 B2US12624403 B2US 12624403B2US-12624403-B2

Abstract

An optimal calculation method of an energy operating condition in an iron mill includes calculating, using a total energy operation cost of the iron mill within a predetermined period of time from a current time as an evaluation function, an operation condition of an energy facility in the iron mill as a decision variable such that a value of the evaluation function decreases, at each predetermined time within the predetermined period of time, based on actual values and estimated values of a generation amount and a used amount of energy utility for each of factories comprised in the iron mill. The method includes a step of calculating the decision variable by imposing an equality constraint such that the decision variable related to a power generation facility included in the energy facility is constant within a predetermined aggregation time.

Inventors

Tomoyoshi Ogasahara
Masahiro Uno
Koji Yoshihara
Kazushige YATSU

Assignees

JFE STEEL CORPORATION

Dates

Publication Date: 20260512
Application Date: 20210316
Priority Date: 20200331

Claims (4)

1 . An operating method of an iron mill using an optimal calculation method of an energy operating condition in the iron mill, the optimal calculation method being executed by an information processing apparatus configured to perform a periodic optimization process for an energy management system of the iron mill, the operating method comprising: defining time points, starting at a current time, within a predetermined period of time based on a predetermined cycle; defining a total energy operation cost of the iron mill within the predetermined period of time as an evaluation function, calculating an operation condition of an energy facility in the iron mill as a decision variable based on actual values and estimated values of a generation amount and a used amount of energy utility for each of factories comprised in the iron mill, wherein the decision variable is calculated such that the evaluation function decreases over the predetermined period of time, and controlling the operation of the power generation facility in the iron mill based on the calculated decision variable, wherein the energy utility for each of the factories includes gas, steam, and electric power, the energy facility includes a mixed gas production facility, a gas holder, a coke drying quenching facility, a top-pressure recovery turbine facility, and a power generation facility that uses by-product gas, heavy oil, or steam extraction, the operation condition includes an amount of the by-product gas, the heavy oil or the steam extraction used in each power generation facility, or a storage amount or a discharge amount of the gas holder, a designated time in the predetermined period is defined, and a series of time points after the designated time within the predetermined period are set to an aggregation period, the calculating includes: calculating the decision variable related to the power generation facility included in the energy facility at each of the time points from the current time to the designated time in the predetermined period, and within the aggregation period, calculating the decision variable by imposing an equality constraint such that the decision variable related to the power generation facility included in the energy facility is constant within the aggregation period.
2 . The optimal calculation method of an energy operating condition in an iron mill according to claim 1 , wherein the total energy operation cost includes a cost associated with use of heavy oil, city gas, and steam and a cost associated with purchase of electricity.
3 . The operating method of an iron mill according to claim 1 , wherein the calculating further comprises imposing a change rate constraint that allows the decision variable to change by a proportionally larger amount at the boundary of the aggregation period compared to changes between individual time points outside of the aggregation period.
4 . The operating method of an iron mill according to claim 1 , wherein the controlling the operation of the power generation facility includes controlling an amount of gas supplied within the iron mill.

Description

FIELD The present invention relates to an optimal calculation method of the energy operating condition in an iron mill, an optimal calculation device of the energy operating condition in an iron mill, and a running method of an iron mill. BACKGROUND In general, iron mills include a large number of factories and a plurality of power generation facilities from upper processes (blast furnaces, coke ovens, steelmaking processes, etc.) to lower processes (rolling processes, surface treatment processes, etc.), and the following energy (gas, steam, and power) operation is performed. That is, B gas (blast furnace gas) generated in a blast furnace, C gas (coke oven gas) generated in a coke oven, by-product gas such as LD gas (LD converter gas) generated in a converter, and M gas (mixed gas) obtained by mixing these by-product gases and adjusting a heat quantity are used in factories or power generation facilities. In a case where a gas supply amount is insufficient with respect to a factory demand (for example, a demand amount in a heating furnace of a rolling mill), it is supplemented with city gas to satisfy the factory demand. In addition, in a case where the gas supply amount to power generation facilities is insufficient with respect to a predetermined amount, it is supplemented with heavy oil. These supplemental fuels cost depending on the amount used. On the other hand, in a case where the gas supply amount is excessive with respect to the factory demand, the gas is detoxified by combustion and then released into the atmosphere, but this leads to energy loss and carbon dioxide emission and thus should be minimized. In order to reduce the cost and suppress the release, it is necessary to use a gas holder that is a storage facility for by-product gases or to appropriately adjust the gas distribution amount. As an example, in a gas holder, in a situation where the supply amount of by-product gases is larger than the demand amount, the storage amount (gas holder level) of the by-product gases is increased by storing the by-product gases in the gas holder in preference to releasing, thereby suppressing the release. On the other hand, in a situation where the demand amount for by-product gases is larger than the supply amount, the stored gas is discharged from the gas holder to satisfy the demand, thereby reducing the amount of supplementary fuel used. In addition, in a case where the demand amount of by-product gases is further larger than the supply amount, the output of power generation facilities is reduced. Moreover, in a case where it is still not possible to deal with the problem, the running level of the factory may be lowered. Steam is supplied by operations such as steam extraction from an exhaust heat recovery boiler from LD gas or a sintering furnace, a boiler of a coke drying quenching (CDQ) facility, and a turbine middle stage of a power generation facility (operation of obtaining steam from a turbine middle stage, the power generation amount is reduced) and is used in a factory (acid pickling tank heating in a cold rolling factory or a vacuum degassing facility). For an amount in shortage with respect to the steam demand, purchase is made from an external party. In addition, the power demand of the factory is satisfied by the amount of power generation in the CDQ, a top-pressure recovery turbine (TRT), and power generation facilities and power purchase from an electric power company. The amount of power purchased needs to be managed so as not to exceed the contract amount per hour (upper limit of the amount of power purchased). In addition, since the power purchase unit price varies depending on hours of the day, in a case where it is in hours when the unit price is high and there is an excess in the by-product gas supply amount, the operation conditions that minimize the cost varies depending on hours of the day or the supply and demand situation, such as setting the output of the power generation facilities high to reduce the power purchase amount. From such a background, technology for minimizing energy operation cost in an iron mill has been proposed (see Patent Literatures 1 and 2 and Non-Patent Literature 1). CITATION LIST Patent Literature Patent Literature 1: Japanese Patent No. 5862839Patent Literature 2: JP 2004-171548 A Non Patent Literature Non Patent Literature 1: Yujiao Zeng, Xin Xiao, Jie Li, Li Sun, Christodoulos A. Floudas, Hechang Li, “A novel multi-period mixed-integer linear optimization model for optimal distribution of byproduct gases, steam and power in an iron and steel plant”, Energy. 2018, vol. 143, p. 881-899. SUMMARY Technical Problem All of the technology described in Patent Literatures 1 and 2 and Non-Patent Literature 1 solve a mixed integer programming problem suitable for appropriately describing the operation condition or running rules of a plant in order to obtain the optimal energy operating condition of an iron mill or a plant. This mixed integer programming probl