AISI Paper May 2007

PIZO Furnace Demonstration Operation
For Processing EAF Dust
Authors: James E. Bratina (R&D Engineer) and
Kim M. Lenti (Operations Manager)
Heritage Technology Group
7901 West Morris Street
Indianapolis, Indiana 46231
(317) 486-2983
Fax: (317) 486-2985
Heritage has developed a new technology (PIZO Process) for the upgrading of
oxide materials from the metals industry. Construction of a one ton per hour
demonstration facility for this process was completed in early 2006. This paper provides
a discussion of the operation of this demonstration facility while processing BOF sludge
and EAF dust to produce zinc, iron and slag products. The facility was operated from
January 2006 until September 2006 to gain detailed process and economic data to design
a full scale operating facility.
The Heritage Technology Group has been working with the steel industry for
several years in the evaluation of processes to use waste oxide feed materials for the
production of iron, zinc and slag products. After several bench and pilot programs in its
laboratory test facilities, it was determined that the PIZO (Pig Iron Zinc Oxide) Process
represented a method that could be used on a commercial scale.
Heritage began to make plans for the construction of a demonstration facility to
prove the PIZO Process concept and begin to evaluate design and operating parameters.
This paper is a description of the planning, installation and operation of the PIZO Process
by Heritage Technology Group.
The Heritage PIZO Process uses a continuous channel induction furnace as the
primary processing unit. The channel furnace contains a bath of molten iron to serve as a
heat sink to provide for the rapid heating of feed materials. The feed materials are a mix
of metal oxides and reductant materials usually in the form of briquettes. As the feed
materials are added to the furnace a portion of the metal oxides are reduced to their
elemental state. The first metals reduced are zinc, lead and cadmium, followed quickly
by iron and other metals. The operating temperatures of the PIZO furnace (2400 to 2700
degrees F) allow these reactions occur very quickly.
Volatile metals (zinc, lead, cadmium, etc.) formed in the furnace are vaporized at
the operating temperature of the furnace. The furnace is operated with a slight negative
pressure created by the product collection dust collector on the furnace. Vapors are
removed from the furnace by this negative pressure through a hood on the vapor outlet on
the furnace. As the vapors leave the furnace (see Pictures 1 and 2) they are combined
with dilution air, which provides oxygen to burn the metal vapors back to their oxide
state. The dilution air also provides some cooling of the vapors as it enters the dust
collection system. The metal oxide dust is collected as crude zinc product in a
conventional baghouse system. This product has a good value to zinc manufacturing
processes as crude zinc oxide.
The reduced iron produced by the process flows through the molten slag in the
furnace to combine with the molten iron bath in the furnace. As feed is added to the
furnace, the iron level in the bath increases, requiring a portion of the accumulated iron to
be removed from the bath. This iron is removed on a semi-continuous basis by rotating
the furnace forward and pouring it through a teapot spout into a receiving ladle (Picture
3). The iron product can be used directly as hot metal or poured into a pig machine for
sale as a dense iron product that will be similar to pig iron.
The final product from the PIZO Process is slag. The slag is a combination of the
refractory materials in the feed product such as silica, calcium, magnesium and
aluminum. These materials build up as a liquid slag that floats on the surface of the iron
bath. The liquid slag has to be removed on a semi-continuous basis from the furnace to
prevent its buildup in the furnace. The slag is removed by rotating the furnace backward
to allow it to flow from the iron surface through a port on the end wall of the furnace
(Picture 4). This slag is poured into a mold that can be removed from the furnace area for
storage (Picture 5). The slag product can be used as a slag conditioner or aggregate for
road construction.
The channel induction furnace provides the ideal device for the continuous feed of
raw materials to produce zinc, iron and slag products. These products are removed on a
continuous or semi-continuous basis. The inductors on the furnace provide an efficient
method for providing energy additions for the process.
Once Heritage made the decision to build a demonstration unit, there was still a
lot of work to be done and decisions to be made on how best to do it especially
economically and expeditiously. The following goals were set for the demonstration
PIZO Process:
 Demonstrate the technology worked
 Develop operating and design parameters for a commercial facility
 Produce products for evaluation.
The first decision made was that the PIZO demonstration system should use a
furnace that can be directly scaled to a commercial facility. As a result, Heritage worked
with Ajax Magnethermic to prepare an induction furnace design that would meet our
operating ideas and needs and could be scaled up. The furnace design selected was a 20ton channel induction furnace with an 1100 KW inductor. This represented a size that
would be 20 to 25% the size of the anticipated commercial system. The furnace would
be capable of processing 1 to 1.5 tons per hour of feed material compared to an
anticipated design of 4 to 6 tons per hour of feed.
The next issue for the demonstration facility was location. While the installation
of the demonstration facility at a green field location controlled by Heritage would be
possible, there would be many logistic issues. The decision was made to install the
demonstration facility at an operating gray iron foundry. The foundry would be able to
provide the trained manpower to operate the furnace and use the iron produced from the
process and provided the quickest time to start-up. After an extended search, the
Accucast Technology Foundry in South Bend, Indiana was selected as the site for the
From the initiation of the process, Heritage worked with the State of Indiana in
the evaluation of the economic and environmental value of the PIZO Process. The State
of Indiana provided a grant to assist in the construction of the demonstration facility
through the Department of Commerce.
The construction of the demonstration facility began in South Bend in mid-2005.
The foundry set aside a section of their building near their other coreless induction
furnaces. The main equipment installed for the demonstration facility included the
channel induction furnace, a product collection baghouse, new electrical equipment to
operate the furnace and the product feed system. The construction was completed in late
2005; with startup in early 2006.
Operation of the demonstration facility began in January of 2006. The initial feed
material to the process was a mixture of BOF sludge and blast furnace sludge. The
briquettes were produced using these feed materials at the Mittal Steel USA Indiana
Harbor East steel mill in East Chicago, Indiana. The demo facility was operated for
approximately 3 months, until April using the BOF briquette feed. During the initial
phase of operation approximately 100 tons of BOF feed materials were processed in the
furnace producing zinc, iron and slag products.
The initial phase of operation of the PIZO demonstration facility provided a good
operating basis. However, there was a compatibility problem between the slag being
made and the refractory that was used for the furnace and it became apparent the furnace
would have to be relined. The Heritage team took this opportunity to make some design
changes in the furnace that would permit more stable operation and testing of different
parameters during the next round of operation. Design modifications were made to the
furnace and it was relined during the spring and early summer. The changes were
completed in July and the furnace was restarted. The second phase of operation of the
PIZO Demonstration furnace included EAF briquettes as a feed material. A briquetter
was set up at Nucor’s steel mill in Crawfordsville, Indiana to make feed briquettes. This
was completed in time for the restarting of the furnace.
The second round of demonstration facility testing was completed in September,
2006. During this test program approximately 100 tons of EAF dust briquettes were
processed into zinc, iron and slag products. The zinc products were collected for
evaluation at zinc manufacturing processes and all of the iron produced was either used
directly by the foundry or pigged into molds for use at later times. Air emission testing
was also conducted for scale-up to commercial design.
The PIZO demonstration facility was installed to develop design and economic
information on the process to be able to determine the commercial viability of the
process. Some of the key information required included the composition of the products,
distribution of trace elements of interest, utility requirements, operating parameters for
the process, air emissions and other key process information.
One of the most important aspects of the PIZO Process operation was the ability
to produce three distinct saleable products – iron, zinc and slag – and no waste. This was
successfully demonstrated.
One key concern was the distribution of trace materials in the slag product. It is
important that the slag product not contain any lead, cadmium and zinc that are present in
the feed product. Even small quantities of these elements in the slag would severely limit
the possible end uses and make it more difficult to store and handle the slag at the
production facility. Table 1 provides a summary of the composition of key components
in the slag from the demonstration facility operation. Note the slag is very low in iron.
This is one of the benefits of the design of the PIZO furnace and its operating conditions.
The slag was tested for leachability according to Standard Toxic Characteristic
Leachability Procedure (TCLP). The results are shown in Table 2.
30% CaO
27% SiO2
20% MgO
6% Al2O3
4% Fe2O3
2% Na
1% S
< 0.1 ppm
< 0.1 ppm
0.1 ppm
TCLP Result
0.072 ppm (max)
Below Detection Limit
1 ppm (max)
Regulatory Limit
5 ppm
1 ppm
Not Applicable
The crude zinc oxide product should contain all of the volatile metals of interest
(lead, cadmium and zinc). Table 3 provides a summary of the typical composition of the
crude zinc product from the PIZO Process. The crude zinc product will be further
processed in other manufacturing steps to produce zinc, lead and cadmium products at
other facilities. It should be noted that the loss of iron product to the crude zinc product
is very low with iron composition in the crude zinc of less than 1.5%. This helps to
reduce the loss of iron from the process and provides a better feed material for down
stream zinc processing operations.
67% Zn
3.0% K
2.5% Cl
1.5% Fe
1.0% Pb
1.0% Na
0.5% S
0.2% F
0.02% Cd
The typical composition of the iron product is provided in Table 4. Overall
recovery of the iron units in the PIZO iron product is very good as demonstrated by the
low concentration of iron in the slag and crude zinc products. The composition of the
iron product is very dependent on the composition of the feed to the process. Some
elements such as copper, nickel and chromium are almost totally dependent on their
concentrations in the feed. Other components such as sulfur and phosphorus can be
adjusted through the use of different reductant and binder materials and through the
operation of the process.
94 TO 95% Fe
3% C
0.8% Mn
0.5% Cr
0.25% Cu
0.1% S
0.1% P
Heritage was extremely satisfied with the results obtained during the operation of
the PIZO demonstration facility in South Bend. A preliminary engineering design and an
economic evaluation of the process has been completed. Heritage is presently looking at
opportunities for the installation of the first commercial facility. The first commercial
PIZO facility will be built and operated by Heritage and its partners at a site to be
We would like to thank the numerous organizations and individuals that have
assisted in the completion of the test work at the Heritage PIZO Demonstration facility.
These organizations include the following:
Indiana Department of Commerce for their support and assistance in funding a
portion of the project in the form of a grant.
Accucast Technologies for their cooperation in the installation and operation of
the demonstration at their facility in South Bend.
Ajax Magnethermic for their assistance in the design of the channel induction
furnace used at the facility.
Mittal Steel USA Indiana Harbor East for allowing BOF and blast furnace
material from their facility to be used in briquettes used as feed for the process.
Nucor Steel Crawfordsville for allowing Heritage to make EAF dust briquettes at
their facility for use in the process.
Waltz Holst for providing onsite mechanical contractor support for the operation
of the PIZO facility.
The Heritage Group of companies that have provided analytical, logistic,
operation and economic support for the completion of the PIZO demonstration
facility program.