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Project: Steel Plant Automation – Melt Shop, Rolling Mill & Auxiliaries

1. Process Overview

This project provides a comprehensive, plant-wide automation solution for a complete steelmaking and rolling facility. The scope covers the control and monitoring of six primary production and utility areas:

  • 1. Melt Shop: Control of the Electric Arc Furnace (EAF), Continuous Caster Machine (CCM), and all associated ferroalloy and material transfer systems.

  • 2. Air Separation Unit (ASU): Management of the oxygen and nitrogen production process, including compressors, cryogenic refrigeration columns, and storage.

  • 3. Fume Treatment Plant (Dedusting): Control of the main furnace suction fans, baghouse cooling systems, and dust collection units.

  • 4. Water Treatment Plant (WTP): Automation of all water utility processes, including main pumps, sand filters, heat exchangers, reverse osmosis (RO) systems, and chemical injection skids.

  • 5. Compressed Air Station: Control of main plant air compressors and air dryers.

  • 6. Rolling Mills: Automation of the reheating furnaces, material preservatives, and the complete hot-rolling and cold-rolling mill stands.

2. VFD (Variable Frequency Drive) Application

VFDs are fundamental to this project for process control, energy savings, and asset protection. Drives will be engineered and integrated for the following high-demand applications:

  • Rolling Mills (Main Drives): Application of large-scale Medium Voltage (MV) VFDs for the main rolling stands. This is essential for:

    • Precise speed and torque control.

    • Coordinated speed synchronization (“cascading”) between mill stands.

    • High-inertia load management.

  • Fume Treatment Fans: MV VFDs for the main de-dusting fans to precisely control furnace draft, manage suction based on process needs (e.g., tapping, charging), and achieve significant energy savings.

  • Pumps (WTP & Hydraulics): Low Voltage (LV) VFDs for all major pump sets (WTP feed, RO, heat exchanger pumps) to maintain constant pressure and flow, optimizing the process and reducing energy waste.

  • Compressors (ASU & Air): Integration with or installation of MV/LV VFDs for the main air and oxygen compressors to manage output based on plant demand (load/unload).

  • Caster & Transfer Systems: LV VFDs for the Caster (strand withdrawal/straightener) and material transfer systems (conveyors, rollers) to ensure synchronized, variable-speed operation.

3. Control System Architecture

The technical solution is a plant-wide, distributed control system based on the Siemens SIMATIC S7-1500 platform, featuring a tiered CPU architecture for optimized performance and cost.

A. Controller CPU Configuration:

  • High-Performance (6x): CPU 1517-3 PN/DP

    • Designated for the most critical and high-speed process areas, such as the Main Rolling Mill Stands, Caster, and EAF controls.

  • Standard Process (12x): CPU 1515-2 PN

    • Used for large-scale auxiliary and utility units, such as the Fume Treatment Plant, WTP, and ASU.

  • Local Control (15x): CPU 1513-1 PN

    • Deployed for smaller, independent package units, local control stations, and I/O concentration.

B. I/O Module Bill of Materials:

  • Standard I/O:

    • Digital Input: 72 x (DI 32x24VDC)

    • Digital Output: 78 x (DQ 32x24VDC)

    • Analog Input: 92 x (AI 8xU/I/RTD/TC ST)

    • Analog Output: 84 x (AQ 8xU/I HS, 16-bit)

    • Combo Module: 25 x (AI 4xU/I/RTD/TC / AQ 2xU/I)

  • Technology & Motion Modules:

    • Purpose: These high-speed modules are specified for the advanced motion, synchronization, and cut-to-length applications in the Rolling Mills and Caster.

    • High-Speed Counter: 24 x (TM Count)

    • Positioning Control: 15 x (TM Position)

    • Counter Module: 10 x (Counter)