Manufacturing method of a steel product

Abstract

A method to manufacture a steel product in a steelmaking plant including several different tools, the method including the definition of at least two manufacturing routes using different tools and the calculation of the expected level of CO2 emissions associated to each of this defined manufacturing routes.

Description

The invention is related to a method of manufacturing steel.

BACKGROUND

The steel industry, like many other human activities, is a source of CO2 emission in the atmosphere. Many technologies are implemented or under development to decrease those CO2 emissions at different levels of the production, through for example recycling of blast furnace, coke oven or converter top gas. This recycling may be performed, after appropriate treatments, by injection into another steelmaking device or use as syngas for other productions.

These technologies aim to decrease direct CO2 emissions of the manufacturing of steel products.

SUMMARY OF THE INVENTION

However, customers of such steel products, such as car makers, also have to reduce the carbon footprint of their products and to do so request steel products fulfilling all their usual standards in terms of physical properties and quality, but also in terms of carbon footprint. This CO2 carbon footprint is not limited to the direct emissions of the manufacturing process itself.

There is so a need for a method allowing to determine and reduce the CO2 footprint of steel products.

The present invention provides a method wherein a steel product is to be manufactured in a steelmaking plant comprising several manufacturing tools, the method including the steps of defining at least two different manufacturing routes using tools allowing to manufacture the steel product, calculating, for each defined manufacturing route, an expected level of CO2 emissions to manufacture the steel product according to each manufacture route, such calculation being done considering all CO2 contributions associated to raw materials, energy sources and processes used for manufacturing the steel product according to each manufacture route, and producing the steel product using the tools according to the manufacturing route=having the lowest calculated expected level of CO2 emissions.

The method of the invention may also comprise the following optional characteristics considered separately or according to all possible technical combinations:

• • the method further comprises a first step of target definition wherein a maximum level of CO2 emissions is predefined for the manufacturing of the steel product and the producing step is performed only if the lowest expected level of emissions is inferior or equal to the predefined maximum level, otherwise new manufacturing routes are defined and new associated expected level of CO2 emissions are calculated.
  • raw materials are chosen among scrap, iron ore, coal, coke, sinter feed, pellets, gases
  • scrap is of different types and is chosen among old scrap, new scrap, prime scrap, home scrap, pit scrap, shredded, plates and structure scrap, heavy melting scrap, cast scrap, coil scrap or busheling scrap.
  • energy sources are chosen among renewable electricity, electricity produced by internal recycling of exhaust gas from the steel manufacturing process or by capture of heat released by products from the steel manufacturing process.
  • processes are chosen among direct reduction processes, hydrogen-based ironmaking, steel electrolysis, blast furnace with top-gas recycling, blast furnace with top-gas conversion, electric-arc-furnace steelmaking, converter steelmaking, scrap melting.
  • the method further includes a step, after production step of establishing a certificate for the manufactured steel indicated the level Eexpi of CO2 emissions associated to its manufacturing route.
  • the tools are chosen among a coking plant, a sintering plant, a direct-reduction plant, a blast-furnace, an electric-arc furnace, a converter, a ladle, a H2 production plant, a chemical plant, a biotech plant, a power plant, a ladle, a furnace, a casting plant, a rolling plant, gas cleaning devices, heat recovery devices, hot stoves.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will emerge clearly from the description of it that is given below by way of an indication and which is in no way restrictive, with reference to the appended FIGURES in which:

FIG. 1 is a flowchart of a method, according to the invention, for manufacturing steel

DETAILED DESCRIPTION

FIG. 1 represents a flowchart of a method to manufacture a steel product according to the invention. A steel product P is to be manufactured into a steelmaking plant S comprising several manufacturing tools T_x. A manufacturing tool maybe a combination of several equipment. For example, a blast furnace with top-gas recycling is one tool, even if it comprises a blast furnace, gas treatment devices and gas heating devices. The tools T_x may be chosen among a coking plant, a sintering plant, a direct-reduction plant, a blast-furnace, an electric-arc furnace, a converter, a ladle, a H2 production plant, a chemical plant, a biotech plant, a power plant, a ladle, a furnace, a casting plant, a rolling plant, gas cleaning devices, heat recovery devices, hot stoves.

In a first step 100, at least two different manufacturing routes MRi allowing to manufacture the product P and using tools Tx are defined. For example, i=3, MR₁ uses tools T₁, T₂, T₃ which are respectively a blast furnace with top gas recycling, a steelmaking unit with a converter and a continuous caster, MR₂ uses tools T₂, T₃ and T₄, T₄ being a hydrogen-based blast furnace, MR₃ uses tools T₅, T₆ and T₃ wherein T₅ is an electric arc furnace and T₆ is a secondary metallurgy unit.

In a second step 110, an expected level of CO2 emissions Eexp_i to manufacture the steel product P according to each manufacture route MR_i is calculated considering all CO2 contributions associated to raw materials, energy sources and processes used for manufacturing the steel product according to each manufacture route MRi.

Raw materials may be of different types. They may include coal, coke, iron ore, biomass, sintered ore, agglomerates, pellets, direct-reduced iron (DRI), scrap, mineral additions, such as limestone or dolomite, alloying elements but also gases such as oxygen or hydrogen. Scrap maybe of different typologies among, notably, old scrap, new scrap, prime scrap, home scrap, pit scrap, shredded, plates and structure scrap, heavy melting scrap, cast scrap, coil scrap or busheling scrap. In a preferred embodiment, raw materials are selected among biomass, cold-bonded pellets, direct-reduced iron, scrap, mineral additions, alloying elements, oxygen and hydrogen.

By considering all CO2 contributions linked to raw materials, it is meant that all CO2 emissions linked to the production of those raw materials before they are used into the steel manufacturing process is taken into account. For example, when considering iron ore, all CO2 emissions related to the mining extractions and ore processing have to be included into the calculation. Same for the scrap, even it is the recycling of an existing product, it has a CO2 footprint coming from its former life which has to be considered into the calculation. Depending on its typology, CO2 footprint may differ from one scrap to another.

Energy sources may also be various. They include electricity coming from renewable energy, such as from solar panels or windmills, but also electricity produced by power plant, which may use gases resulting from the steelmaking process, such as blast furnace gases or converter gases. It also includes any fuel, either gaseous or solid, fossil or organic, which may be used into the steel manufacturing process. In a preferred embodiment energy sources are chosen among renewable electricity, electricity produced by internal recycling of exhaust gas from the steel manufacturing process or by capture of heat released by products from the steel manufacturing process.

In order the calculation to be the most accurate it is important to not count a CO2 impact twice. For example, if coke is considered as a raw material to the converter process and its impact included into the raw materials impact, it must not be considered as a fossil fuel and included into the energy sources impact.

Processes include all different processes performed along the manufacturing route and their associated CO2 emissions. It includes pig iron production, liquid steel production and finishing processes. Pig iron production includes coking, sintering, pelletizing, blast furnace process, but also direct reduction and shaft furnace processes. Liquid steel production covers decarburization, dephosphorization and all secondary metallurgy or ladle treatments allowing to turn pig iron into liquid steel and adjust the composition of the liquid steel for further steps, it also includes the electric-arc-furnace steelmaking process. Finishing processes include notably casting, heating, rolling, cooling, coiling, shaping, levelling, welding, coating. When considering CO2 impact of a process, all by-products recycling or emission reduction technologies applied to said process has to be taken into account for the calculation. For example, blast furnace process without top-gas recycling does not have the same CO2 impact as the same blast furnace process wherein top-gas is not released to the atmosphere but rather re-injected into.

In a preferred embodiment, processes are chosen among direct reduction processes, hydrogen-based ironmaking, steel electrolysis, blast furnace with top-gas recycling, blast furnace with top-gas conversion, electric-arc-furnace steelmaking, converter steelmaking, scrap melting. By hydrogen-based ironmaking it is meant any ironmaking process, such as a direct-reduction process or a blast-furnace process wherein the reducing gas is mainly composed of hydrogen. Blast-furnace with top-gas recycling means a blast furnace process wherein top-gas exhausting from the blast furnace is at least partly re-injected into the blast furnace after appropriate treatments. Blast furnace with top-gas conversion means a blast furnace process wherein top-gas exhausting from the blast furnace is at least partly used to produce a syngas which is then further used in chemical, biochemical or power plants

Once this expected level of CO2 emissions Eexp_i is calculated, all Eexp_i are compared and the product P is manufactured 120 into the steelmaking unit according to the manufacturing route MR_i having the lowest expected level of emissions Eexp_i.

The method may also comprise an additional step 130, after the manufacturing step 120, of establishing a certificate for the manufactured steel indicated the level Eexp_i of CO2 emissions associated to its manufacturing route.

With the method according to the invention it is thus possible to produce the steel product P with a reduced carbon footprint and to determine said carbon footprint.

Claims

1-8. (canceled)

9: A method of manufacturing a steel product P in a steelmaking plant S comprising several manufacturing tools Tx, the method comprising the following steps: defining at least two different manufacturing routes MRi using tools Tx allowing to manufacture the product P;calculating, for each defined manufacturing route MRi, an expected level of CO2 emissions Eexpi to manufacture the steel product P according to manufacture route MRi, the calculation being done considering all CO2 contributions associated to raw materials, energy sources and processes used for manufacturing the steel product according to each manufacture route MRi; andproducing the steel product P using tools Tx according to the manufacturing route MRi having the lowest calculated expected level of CO2 emissions Eexpi.

10: The method as recited in claim 9 further comprising including a first step of target definition wherein a maximum level of CO2 emissions Emax is predefined for the manufacturing of the steel product P and the producing step is performed only if Eexpi is inferior or equal to Emax, otherwise new manufacturing routes MRi are defined and new associated expected level of CO2 emissions Eexpi are calculated.

11: The method as recited in claim 9 wherein raw materials are chosen from the group consisting of scrap, iron ore, coal, coke, sinter feed, pellets, and gases.

12: The method as recited in claim 11 wherein the scrap is chosen and of different types and chosen from the group consisting of: old scrap, new scrap, prime scrap, home scrap, pit scrap, shredded, plates and structure scrap, heavy melting scrap, cast scrap, coil scrap and busheling scrap.

13: The method as recited in claim 9 wherein the energy sources are chosen from the group consisting of: renewable electricity, electricity produced by internal recycling of exhaust gas from the steel manufacturing process and electricity produced by capture of heat released by products from the steel manufacturing process.

14: The method as recited in claim 9 wherein the processes are chosen from the group consisting of: direct reduction processes, hydrogen-based ironmaking, steel electrolysis, blast furnace with top-gas recycling, blast furnace with top-gas conversion, electric-arc-furnace steelmaking, converter steelmaking, and scrap melting.

15: The method as recited in claim 9 further comprising a step, after the production step, of establishing a certificate for the manufactured steel indicated the level Eexpi of CO2 emissions associated to its manufacturing route.

16: The method as recited in claim 9 wherein the tools Tx are chosen from the group consisting of: a coking plant, a sintering plant, a direct-reduction plant, a blast-furnace, an electric-arc furnace, a converter, a ladle, a H2 production plant, a chemical plant, a biotech plant, a power plant, a ladle, a furnace, a casting plant, a rolling plant, gas cleaning devices, heat recovery devices, and hot stoves.