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 James.firstname.lastname@example.org ABSTRACT 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. INTRODUCTION 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. DESCRIPTION OF THE PIZO PROCESS 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. INSTALLATION OF DEMONSTRATION FACILITY 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 demonstration. 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. DEMONSTRATION FACILITY OPERATION 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. RESULTS FROM THE DEMONSTRATION FACILITY 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. TABLE 1 TYPICAL COMPOSITION OF SLAG PRODUCED FROM PIZO PROCESS 30% CaO 27% SiO2 20% MgO 7%MnO 6% Al2O3 4% Fe2O3 2% Na 1% S TABLE 2 TCLP TESTING OF SLAG PRODUCED FROM PIZO PROCESS Metal Concentration Lead < 0.1 ppm Cadmium < 0.1 ppm Zinc 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. TABLE 3 TYPICAL COMPOSITION OF CRUDE ZINC OXIDE PRODUCT FROM PIZO PROCESS 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. TABLE 4 TYPICAL COMPOSITION OF IRON PRODUCT FROM PIZO PROCESS 94 TO 95% Fe 3% C 0.8% Mn 0.5% Cr 0.25% Cu 0.1% S 0.1% P FUTURE PLANS FOR THE PIZO PROCESS 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 determined. ACKNOWLEDGEMENTS 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.