PRIME Deployment for Integrated Planning at the Reduction Division
UniSoma fully deployed PRIME – Process Industry Metaframe, at the Production Planning Department in Gerdau Açominas, for the integrated planning of the reduction area.
Gerdau Açominas is an integrated plant, covering reduction, steel making and rolling processes. In 2007, with the 2nd Blast Furnace start up, the unit completed another step of its installed capacity expansion plan, increasing production from 3 to 4.5 million tons of steel per year. Besides the blast furnace, which transforms basic raw material such as sinter, lump ore and coke into ping iron, other investments were made in the reduction area, among which a new sintering machine and a new set of coke-oven batteries.
The reduction area has, besides the previously mentioned equipments, yards for storing ores, intermediate products (such as sinter and coke) and internally generated by-products. Exposed to weather conditions, these materials undergo a degradation process. Due to this, before loading them into the blast furnace, a sifting process must be applied. The sifted materials (thin coke and raw metallic materials) are reused within the same area. Coke breeze, for example, is used as sintering fuel, complementing the imported anthracite. Other generated residual materials (ex: blast furnace powder, rolled-in scales etc) are reused in the sintering process, given its high chemical quality.
Part of the used iron ore is purchased from outside suppliers. However, Gerdau Açominas owns private mines (currently Várzea do Lopes e Miguel Burnier) which account for about 30% of the ore consumed by the plant. These materials are processed in beneficiating plants.
The Production Planning Department at Gerdau Açominas is responsible, among other things, for elaborating the “Monthly Reduction Production Schedule”. This process begins with the production schedule consolidation for various reduction area departments at the plant, namely, Blast Furnace, Sintering, Coke Plant and Mines/Beneficiating Plants.
Following this, the several independently generated production schedules assembled and are verified for inconsistencies. In the case that a problem is detected with products or by-products balances, the planning team negotiates with each one to review their production schedules, so as to obtain a feasible integrated plan. The sinter mix supply, for example, is determined by the sintering area. Its is determined according to a minimal cost criteria, respecting the physical-chemical constraints of the final product, but not taking ore supplying overtime. During the consolidation process, the daily material balance is calculated according to initial stock and receiving/consuming projections. In case a lack of material is identified, a new mixture is requested for the sintering area.
The monthly schedule was manually generated, through Excel®. To improve its integrated planning process, Gerdau Açominas hired UniSoma to customize and deploy PRIME (Process Industry Metaframe).
The projects biggest challenge was to replicate in PRIME all balance calculations of products and by-products considered in the process. Another important requirement identified at the beginning of the project was to enable an automatic system data feed, in order to minimize the manual entry.
PRIME is a generic and flexible decision support tool for tactical and operational planning at process industries. It was developed in AIMMS and based on UniSoma’s previous experiences in the steel industry.
As well as considering by-product generation possibilities for processes, PRIME allows for “variable income” for each process, as opposed to a fixed income defined by a typical BOM. This type of calculation is done with an embedded mathematical optimization model. The optimization model within PRIME is a Mixed Integer Programming model and determines, among others:
» the optimal production level for each process, according to pre-established limits;
» the consumption of raw materials in the various processes, according to fixed or variable BOM’s;
» the generation of (eventually alternatives) products in the various processes;
» purchase needs through firm or under analysis contractual agreements;
» by-product sales opportunities, also according to existing or future contracts;
» the strategic storage policy for several products.
The first phase of PRIME deployment consisted of identifying reduction area processes and its representation according to the applications data model. It also comprised in determining the processes products and by-products consumption and/or generation calculations according to PRIME’s flexible data model.
The bellow scheme illustrates a subset of processes identified during the initial survey. It shows the sinter production process with the use of blended material pile and the reuse of degradated metallic material in the same pile. This is an example of the “circular” calculation used for material balance in the application.
The next step consisted of customizing the system, according to planning area requirements, for both GUI and optimization model. Finally the application was integrated to the “Monthly Production Schedule” spreadsheet for (a) model data supply (production limits, maintenance times, specific coefficient and/or fixed consumption and/or generation) and (b) optimized production plan generation and presentation of management reports.
Gerdau S.A. is the 13th largest steel producer in the world and is market leader for the long steel segment in the Americas. Present in over 14 countries, its products supply civil construction, industry and agribusiness sectors.
Its Presidente Arthur Bernardes plant is located in Ouro Branco and Congonhas, in the Alto Paraopeba region, in the state of Minas Gerais. The plant has an installed capacity of 3 million tons of liquid steel per year.