Developments Toward an Intelligent Electric Arc Furnace at - Tenova

CONCLUSIONS
The furnace performance at CMC Texas, during the EFSOP ® evaluation period (February 20 th to march 19 th , 2006) compared to
January 2006 is summarized in Table 1. The reduction in the power on time and the electrical energy consumption and the increase in
yield in particular resulted in an overall saving of 3.02 dollars per cast ton.
Table 1: EFSOP ® Performance Summary based on cast short tons.
Performance
Parameters
Baseline
EFSOP ®
Optimization
Difference
Power on time (min.) 37.94 37.45 0.49
Savings
Electricity, Kwh/t 376.75 367.52 9.23 $ 0.40
Gas, scf/t 236.98 227.83 9.15 $ 0.10
Carbon, lb/t 28.21 30.57 -2.36 - $ 0.22
Oxygen, scf/t 1131.88 1124.00 7.87 $ 0.02
Yield, % 91.83 92.33 0.5 $ 1.25
Productivity
Cast ton/POT
Overall performance,
$/ cast ton
($/t)
3.19 (t/min) 3.22 (t/min) 0.03 (t/min) $ 0.66
Many of the steel-making parameters in the EAF, due to limitations in sensor technology, are measured sporadically and possibly only
once or twice per heat. For example, bath carbon and temperature may be sampled once or twice per heat or sometimes not at all; slag
and bath residuals are sampled only once (if at all) and analysis is done off-line. Very little dynamic information exists for the steelmaker
to gauge the progress of the process from start to finish. The advantage provided to steel-makers by the EFSOP ® system is a
dynamic measure of chemical energy usage over the course of the heat and the corresponding link to the process. The goal of the
modeling effort explained above is to provide a tool that relates dynamic off-gas measurements to important steel-making
considerations and the operation of the furnace in general. The following modules are being developed to extend the capabilities of
the Goodfellow EFSOP ® system.
Enhanced water-leak detection: Above was described an empirical method determining the possible incidence of water-leaks in the
EAF. The gas-phase model, through a hydrogen balance is able to calculate water in-leakage into the EAF directly. Some tuning will
still be necessary to account for wet scrap, flashing of oils, etc. but it is expected that the method will be more accurate than the
empirical approach presented.
Cost-based post combustion: Presently, the control of post-combustion in the EAF is done through post-combustion ratios or other
similar measures of the extent of combustion in a fee-back loop to oxygen and methane rates. These simple methods do not take into
account the fact that the efficiency of post-combustion varies over the course of the heat. To account for this, constraints on the
maximum and minimum allowable rates of oxygen and methane are varied over the course of the heat. For example, if postcombustion
is deemed inefficient, then the maximum allowable oxygen rate is set lower to minimize oxygen usage during that
particular interval.
The mass/energy model may be used to estimate the efficiency of combustion within the EAF directly. This parameter, in turn, along
with costs for oxygen, methane and energy may be used to calculate the marginal benefit per unit of oxygen or methane. Feedback to
the burners can then be based on the cost/benefit of oxygen or methane usage accordingly.
Fume system control: In many EAF shops, the threat of explosions within the de-dusting system and other safety concerns have
resulted in over-drafting of the EAF. A larger than necessary ballast of air entering the EAF takes with it valuable energy and
represents a considerable in-efficiency in the operation of the EAF. A dynamic measure of off-gas composition, along with a
mass/energy balance makes it possible to calculate the amount of in-leakage air and the heat-load on the EAF fume system. This
information may be used to minimize (within safety constraints) the amount of air-in leakage into the EAF.
$ 2.21