Installation of Praxair’s CoJet® Gas Injection System at
Sumikin Steel and other EAFs with Hot Metal Charges Prented at the AISTech 2008 Iron & Steel Technology Conference and Exposition, Pittsburgh, PA
Larry Cates
Praxair, 1500 Polco Street, Indianapolis, IN 46222,
嘉佑集
Kuniharu Fujimoto
Yasukazu Okada
Hiroyoshi Okano
Sumikin Steel, Wakayama Plant, 1850 Minato, Wakayama, Japan
代办收入证明Eiji Hirooka
Air Water, Inc., 20-16 Higashi Shinsaibashi 1-Chome, Osaka City, Osaka, Japan
INTRODUCTION
During the last few years the u of blast furnace hot metal in electric arc furnaces has incread substantially, especially in Asia. Due to the rising price of scrap and the incread availability of hot metal produced from ore, it has become more economical in certain locations to charge substantial quantities of hot metal. This paper describes some of the issues with using hot metal in electric arc furnaces and the benefits of using coherent jet oxygen injection technology on the furnaces. The paper will focus on the installation of the CoJet system for Sumikin Steel, Wakayama Works.
The multifunction CoJet® gas injection system [1-3] includes oxygen injection, carbon injection, preheating, and post-combustion, integrated in one, water cooled, wall mounted injector to provide chemical energy to an EAF in the most effective way to reduce production cost and improve productivity.
The CoJet® gas injection system was developed to inject oxygen in the form of a lar like coherent
jet at supersonic speeds into the steel bath. The oxygen jet from a coherent injector travels significantly farther than an oxygen jet from a conventional supersonic lance. Hence, coherent jet injectors can be positioned well above the bath in the sidewall of the furnace, and still carry out effective injection. When the coherent jet of oxygen produced by the nozzle impinges on the molten steel bath, the concentrated momentum of the oxygen jet dissipates in the steel as fine bubbles, providing deep penetration and effective slag-metal mixing. This results in high efficiency injection and decarburization.
Up to now, Praxair has installed its CoJet® gas injection system on ven furnaces using hot metal charges in Japan, China, India, and North America. Some of the furnaces have ud up to ~80% hot metal, with the elimination of electric power altogether. One of the common objectives of such installations is to increa the hot metal ratio while maintaining/improving the tap-to-tap time with significantly higher blow rates. A typical result from one customer using high levels of hot metal is illustrated below. Previously to the installation of CoJet this customer injected oxygen through a retractable side wall lance.
梦到和男朋友吵架Baline CoJet®
Tap wt. 90t 95t
% Hot Metal 30% 70-90%
Kwh/ton: 280 ~
60 58
Tap-to-tap,
min:
Table 1
SUMIKIN STEEL INSTALLATION
Five furnaces in Japan, both scrap and hot metal bad, have been equipped with CoJet® systems since early 2006 by Praxair, working in partnership with Air Water, Inc, a Japane industrial gas supplier. In February 2007, Praxair and Air Water, Inc commissioned a new CoJet system installation at Sumikin Steel, Wakayama Works, in Osaka, Japan on an EAF. This project resulted in a reduction in electrical power consumption of 12% and reduced tap to tap time of 6% during the first month of operation.
Sumikin Steel is located about 60 km south of Osaka, Japan. The plant contains a meltshop and a hot strip rolling mill (HSM). The plant produces 300,000 tons of “H” shapes (beams) each year.
The EAF at Sumikin is a nominal 100 ton (tap weight) furnace supplied by JP Steel Plantech Co. in 1990. Direct Current (DC) power is supplied to the furnace at 53 MW maximum power. Prior to the installation of the CoJet system, oxygen was injected through a water-cooled lance from the wall and consumable lance pipes through the slag door.
Sumikin Steel decided to install the CoJet system in order to:
•increa oxygen injection rates
•reduce power on time
维持秩序•reduce tap to tap time
•reduce electrical power consumption
•increa productivity
•increa flexibility for hot metal charging
Under normal operation about 30% of the total charge is made up of hot metal supplied from the
blast furnace at Sumitomo Metal Industry. However, as much as 80% of the charge could be hot
metal depending on economic conditions. As of the writing of this paper, however, Sumikin
Steel has not charged more than 31% hot metal.
Safety of the operating personnel was also a primary factor in the decision to install the CoJet®system. Operators are no longer required to handle oxygen injection or carbon injection pipes in
front of the working door during operation, thus reducing the time that they need to be near the furnace.
Table II lists results for important operating parameters before installation of the CoJet system
and the average for the first six months of operation after the installation of the CoJet system.
Baline
CoJet®
Tons/hr 88 91
Hot Metal (tons) 30 30
Tap to Tap Time (minutes) 68.0 63.8
Power (KWH/t) 349 304
Oxygen (NM3/t) 24 34
COG (NM3/t) 0 10
Yield (%) 92.9 92.9
人生路上Slag (kg/t) 93 93
Injection Carbon (kg/t) 2.9 2.6
Gunning (kg/t) 3.5 2.6
Electrode Consumption (kg/t) 1.2 1.0
Table II
Coke oven gas (COG) is ud for burner and shroud fuel for the CoJet injectors. COG has
proved to be very effective for u in CoJet injectors, although it must be cleaned to remove the
sulfur in order to prevent erosion of the copper portions of the injectors and water cooled panels.
高中函数In most cas it is also necessary to increa the pressure to allow its u for CoJet injectors. At Sumikin, no additional cleaning was required, however, a new compressor station was installed
by Air Water, Inc to provide sufficient pressure.
The control system equipment ud for this installation makes significant u of Japane
sourced equipment, including Mitsubishi PLCs and Yokagawa instrumentation. The HMI
system is bad on “Wonderware” software, which includes a convenient dual language function
for displaying operator screens in both Japane and English languages. This basic control
package has been ud for all of the CoJet systems installed so far in Japan by Praxair and Air Water.
The piping, coke oven gas compressor station, and CoJet® system control equipment were installed by Air Water, Inc during December 2006-February of 2007. Final installation of the CoJet system equipment was completed during a three day outage in February. This was followed by two weeks of commissioning and optimization by Praxair and Air Water.
Photo 1 – Burner flame at the primary test (2007.2)
Photo 2 – Hi Fire Rate at the primary test (2007.2)
Photo 3 – COG Compressor
Photo 4 – COG Receiver Tank
书房的英语ISSUES WITH USING HOT METAL IN EAFs
Electric arc furnaces are designed to accommodate rapid charging of large amounts of scrap and heating with electrical energy. Therefore, a relatively wide, shallow furnace is required. Basic oxygen furnaces (BOFs), on the other hand are designed to u small amounts of scrap and high rates of oxygen injection to remove the high amounts of carbon prent in the hot metal. The furnaces are taller than the typical EAF vesl to accommodate the reactions encountered when using high rates of oxygen injection.
The u of hot metal in the EAF therefore requires special consideration in the placement of oxygen injectors, injection rates, and operating practices to allow sufficient oxygen to be delivered, while preventing excessive skulling, slopping, and eruptions. Praxair has studied the effects extensively in order to determine the best arrangements for high hot metal consumption.
山谷风
Praxair has studied a number of EAFs using hot metal for 35% to 90% of their total metallic charge, and compared the results of their operation with each other and with Basic Oxygen Furnaces (BOF). This study included factors such as:
