Reheating furnaces are used in steel mills for heating steel pieces
(Billets, blooms, slabs or ingots) to temperatures of around 2200 F or 1200 C,
making them suitable for Hot Rolling. There are different types of continuous
reheat furnaces. The most common types are Pusher, Walking Beam, Walking Hearth, Rotary Hearth
and Roller Hearth. We have more than 50 years of combined experience in Continuous Reheat Furnaces. Over the years we have
developed simulation software to size, analyze and design furnaces, off-line software
models to determine optimal setpoints and on-line, and Level 2 software for complete
automation. We also do Reheat Furnace Study and Data Analysis for energy efficiency,
performance increase, and quality enhancement.
Reheat Furnace Analysis Software
FurnXpert Continuous Reheat Software offers the ability to design, simulate and size Walking Beam, Walking Hearth, Pusher,
Rotary Hearth, and Roller Hearth furnaces. The modules of the Reheat Furnace Software are Furnace Configurator,
Parts Configurator, Parts Placement, and Profile Generator. The idea is to perform what-if analysis with different Process Parameters.
The software calculates temperature rise of the steel stocks along the furnace length during heating in each furnace zones. Additionally,
it calculates heat to steel stocks, refractory and skid losses, opening losses, heat requirement in each furnace zones, total fuel
consumption, furnace efficiency and skid mark on the steel slabs. The analysis can be done for constant production or combination
of production and delays.
HeatXpert Off-Line Software
HeatXpert off-line software is used to manage optimum heating strategy for Walking Beam, Walking Hearth, Pusher, Rotary Hearth,
Roller Hearth Furnaces used in Steel Reheating. It has been developed specifically for furnace operators, to determine optimum
furnace settings. Using this software, one can generate operating setpoints during constant production and operating delays while processing
any size, shapes and grades of steel in continuous reheat furnaces.
Key Features
Recipe/Set-point Management (determination of optimum zone temperatures during constant production) The system
offers the ability to create setpoint recipes (zone setpoint temperatures) for various grades and shapes of steel
at different production rates.
In order to raise charge temperature according to a prescribed heating pattern, temperature setpoints for each heating
zones are determined on the basis of billet size and production rate. There are different sets of recipe tables based on
billet size and metallurgy. HeatXpert Off-line model has the option to create tables to be printed or stored in soft documents. The other
alternative is to input the production rate or product movement rate (push/walk/rotation), charge shapes and grades
of the product. The software then calculates the setpoints and displays it on the computer screen.
Delay Setpoint Management (determination of optimum zone temperatures during delays) The system offers the ability to
create setpoint(zone setpoint temperatures) for various grades and shapes of steel at different delay time.
The software handles 2 kinds of Delays. 1. Scheduled Delays, 2. Unscheduled Delays. Scheduled delays are planned
and usually occur after a specific billet has been discharged. They usually take place due to maintenance work such
as roll change, suspending mill production for a period of time. Unscheduled delays occur due to a problem that has
caused the furnace to halt, stopping billet processing. These problems generally occur due to a furnace breakdown or
problems within the Hot Rolling process.
HeatXpert On-Line Level 2 Supervisory Software
HeatXpert Level 2 software system is very unique in a way that it comes packaged and requires very minimal customization,
thereby reducing the total development cost to the end user. The HeatXpert Level 2 software can be connected to a Level 1
SCADA system easily. It can completely reside on the back ground and display the results on a Level 1 HMI screens or if
required HeatXpert comes with its own set of HMI screens. The primary modules in our Level 2 system are as follows:
Setpoint Management (Determination of Optimum Furnace Temperature) In our on-line setpoint management module the furnace
temperature in each zone is determined by real time heat transfer calculations. The setpoint calculation is a reverse transient
computation to determine furnace profile from actual (computed) and target temperature profile of the billets and billet movement
rate in order to achieve desired discharge temperature with minimum fuel consumption and scale formation. The algorithm takes into
account delayed heating in order to optimize energy and minimize scale and decarburization formation. The on-line system has the capability of
storing and modifying different heat curves for different grades of steel. Each curve has its own target billet temperature, zone
setpoint limits as a function of charge temperature and production rate.
Delay Management (Scheduled and Unscheduled) Scheduled delays are planned and usually occur after a specific billet has been discharged.
The delays usually take place due to maintenance work such as roll change or suspending mill production for a period of time.
Unscheduled delays occur due to a problem that has caused the furnace to halt, stopping billet processing. These problems generally occur
due to a furnace breakdown or a snag in the Hot Rolling process. The delay setpoint is directly proportional to the length of the delay.
Longer the delay duration, more the temperature setpoint is reduced. However, a check is made to ensure that the zone setpoint is never
reduced below a preset, minimum zone setpoint value or average temperature of the hottest billet inside the zone. The zones automatically
ramp up whenever the drop in the zone temperatures divided by the ramp rate is greater than the time left for the delay to end. This ensures
that the furnace is ready when the delay is over. Unscheduled delays are unexpected delays. Since the delays are unexpected, the end time is
usually not known in advance. When such delays are encountered, the zone setpoints are reduced to force the burner to reduce the firing rate.
As the furnace temperature goes down, the setpoints are further reduced until either minimum zone setpoint is reached or hottest billet tempearture in the zone is reached.
Mathematical Model The mathematical model consists of a finite difference heat transfer algorithm, which calculates temperatures throughout
the thickness of billets at different positions along the length of the furnace. These temperatures are obtained by solving the system of heat
transfer equations. The mathematical model executes at a predetermined time interval or steps. At each calculation step, the model determines
the amount of heat that has diffused inside the billets since the previous calculation step. The Heat Transfer calculations take into account
Steel Grades, Product Dimensions, Charge Tempeartures, Charge Postions inside the Furnace, Furnace Profile, and Product Tempeartures at the last step.
Communication Tracking information should come from the tracking computer to our HeatXpert system. HeatXpert system calculate the setpoints
and send them to the supervisory system or PLC. The process variables come from the supervisory system or PLC to our HeatXpert system. HeatXpert System
can reside on the same computer as the supervisory system or could be a different computer. In the same computer data passing will be relatively simpler.
Reheat Furnace Study and Data Analysis
We do Reheat furnace study and Audits with an objective to Improve Furnace Controllability, Increase Production Rate, Improve Product Quality and
Increase Fuel Consumption. The specific areas we concentrate are refractory conditions, Burner firing and controls, Optimum Heating
Parameters and Furnace Design. Our study includes on site furnace inspection during opeartion and complete report on our finding with receommendations.
We also specialize in operational data annalysis to look into the historical process data, identify patterns and relationships among discrete process steps and inputs,
and then optimize the factors that prove to have the greatest effect on yield.
