Page 24 - Steel Tech India eMagazine Volume January 2021

81. Ŗ 01 Ŗ ,CPWCT[

180MW. Besides the sheer availability of such an plants only in areas where the energy cost is almost
amount of power, the operation of the EAF generates negligible.
FKUVWTDCPEGU ƀKEMGT VJCV TGXGTDGTCVG QP VJG WRUVTGCO Last but not least, many BF-BOF plants are used to sell
grid in inverse proportion to the short-circuit power of the BF slag to the concrete industry as an aggregate
VJG UCOG ECWUKPI JKIJ HTGSWGPE[ ƀWEVWCVKQPU QH VJG while the EAF slags, having high content of Iron oxide
CEVKXG RQYGT 'XGP EQPUKFGTKPI UVCVG QH VJG CTV ƀKEMGT (20-40% depending on process) and being strongly
EQORGPUCVKQP GSWKROGPV CDNG VQ TGFWEG VJG ƀKEMGT D[ basic, are not suitable for this purpose.
a factor up to 4, the areas where such a machine can
be installed are still quite limited. Power requirements A New Approach to Ironmaking: The HDRI-to-Hot
of even the largest BF-BOF plant are not comparable, Metal Route
and large infrastructural investments are required to Urged by several steelmakers, TENOVA began
KPETGCUG UKIPKſECPVN[ VJG VQNGTCDNG NQCF QH VJG RQYGT some years ago investigating a minimally impacting
grid. transitional solution to allow a gradual conversion of
+P CFFKVKQP VQ VJG KPHTCUVTWEVWTCN EQPEGTPU ſVVKPI C &4+ existing integral steelmaking plant. The purpose of
EAF route into an existing BF-BOF plant poses also VJG TGUGCTEJ YCU VQ ſPF C RTQFWEVKQP NKPG OKOKEMKPI
logistic issues. Should a plant be willing to consider a C DNCUV HWTPCEG DWV YKVJ UKIPKſECPVN[ NQYGT GOKUUKQPU
gradual transition, progressively weaning the plant from The objective was toeliminate the dependence from the
the dependence of liquid hot metal but keeping the de- coke while remaining able to process low-grade iron
gassing and casting lines as they are, the operation ore to produce an intermediate material compatible with
team would have to integrate within the existing liquid the existing downstream processes, while tackling all
steel stream a source characterized by a different logistic concerns related to the introduction of a DRI-
pace (about 45 minutes’ cycle time against around EAF line into an existing BF-BOF plant.
30 for typical BOF), with a different tapping size and 6JG ſTUV KVGO QH VJKU KPPQXCVKXG RTQFWEVKQP NKPG KU VJG
producing a liquid steel slightly different than the one ENERGIRON Zero Reformer module. This direct
produced in the preexisting facilities (even though DRI- reduction technology, developed by TENOVA and
EAF lines can be used to produce any kind of known now managed within the ENERGIRON consortium,
steel grades). uses a pressurized vessel to reduce iron ore pellets

Successful conversion to DRI-EAF route also requires to DRI. Within the ENERGIRON ZR module the same
changes in the choices of raw materials. The so-called iron pellets in the module act as a catalyst for the
DRI-grade pellets are formed by high-grade iron ore cracking of the methane and of the other hydrocarbons
concentrates, typically with iron content in excess contained in the feeding gas.The ZR operates at high
of 65%, and in the best ones the gangue is mostly pressureachieving metallization rates between 94 and
basic (CaO and MgO). EAF operation requires the 95%. It can produce DRI with Carbon content up to 5%
slag to respond to certain minimum criteria to allow (High-C DRI). The pellets can be charged directly inthe
for Phosphor removal, keep an adequate viscosity downstream melting unit at a temperature in excess of
throughout the whole process and prevent chemical u% TGFWEKPI UKIPKſECPVN[ VJG TGSWKTGF
erosion of the refractory lining of the crucible, typically The solution proposed by TENOVA uses an OSBF to
built with MgO-C bricks. If the pellets charged in the EAF complete the reduction of the iron oxide remaining in the
EQPVCKP UKIPKſECPV SWCPVKVKGU QH 5KNKEC CPF QT #NWOKPC pellets through a reaction with a portion of the carbon
theprocess will require more than equal addition of basic contained in the same and melt the pellets, separate the
ƀWZGU VQ MGGR VJG UNCI YKVJKP CEEGRVCDNG RCTCOGVGTU gangue from the iron and bring the liquid to the desired
CPF UKPEG VJG ƀWZGU TGSWKTG VYKEG CU OWEJ GPGTI[ CU temperature. A portion of the Silica contained in the
the iron to melt, this results in an increase of the electric gangue is also reduced to metallic silicon in the bath,
energy required by the process. achieving a composition of the liquid that is very close
Moreover, as oxygen is blown to achieve the desired to the hot metal produced by blast furnaces, while the
composition endpoint, the slag-steel equilibrium causes Sulphur content remains dramatically lower as natural
VJG EQPEGPVTCVKQP QH (G1 KP VJG UNCI VQ DG CNOQUV ſZGF gas (or hydrogen, or a mix of the two) is used to reduce
for a certain required %C, so the more slag needed, the iron instead of Coke (which brings Sulphur to the hot
the more Iron gets lost to the slag.High quantity of metal produced via the traditional blast furnace route).
gangue implies high-energy consumption and low OSBFsfeature a large static vesselwith semi-permanent
yield. Currently, low-grade pellets are used in DRI-EAF refractory lining, designed forlife cycles of severalyears.

22 STEEL TECH