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Oxygen thermic lance tubes for mining applications

By Nita Karume :

An Oxygen Lance tube is a hollow electric resistance welded (ERW) tube manufactured from mild steel. It is available in various sizes and end finishes and is used in the steel making process.

The Lance tube is employed in the smelting industry, specifically in the mining. This is during the production of ferroalloys, copper, zinc and other ferrous and non ferrous metals industries. The tube is use to burn open large, bottom pouring smelting furnaces such as blast furnaces, basic oxygen furnaces as well as electric and induction furnaces. It is the most cost effective method available for tapping heats.

Lance tube is also used to remove carbon during the smelting process of various metals. The process involves injecting oxygen into the molten metal causing the impurities to be oxidized. This results in slag that floats to the top of the melt which can then be more easily removed.

Although efforts have been made to replace oxygen lances since they are annoying, dangerous and inefficient, nobody has worked to improve the way the traditional oxygen lances work. Development on drills and robotic arms, have failed to replace oxygen lances, which despite their negative side effects have been used for more than a century.

As such, companies such as TREFIMET are working to give relevance to matters normally disregarded in operations, but unmistakably vital, for example: if a furnace cannot be tapped, the pyro metallurgical process will not be completed, or if a rock can’t be melted, the crusher will stop the ore production process. Besides, if the task is difficult or prolonged, the plant availability will be reduced. Consequently, there will be a waste of energy and workers will be exposed to dangerous levels of thermal radiation and gases, as well as to work overload and physical injuries.

A simple observation makes evident that oxygen lances are inaccurate and dangerous; they also generate massive fumes and create a rain of melted material projected against the operator.

Advanced Thermal Lances

TREFIMET’s own manufacturing method allows for the existence of straight lances, free from curves or constrictions, and with several ducts inside. These ducts keep their cross-section through the lance and let the oxygen run freely from one end to the other. Therefore, the oxygen and iron mix efficiently to generate the exothermic reaction of all the iron content in the lance, being available to work 3,228 MJ /Fe kg.

These chemical reactions take place in the tip of the lance, projecting a flow or energy that always goes forward, and thanks to their unique design, TREFIMET lances can keep that energy focused on a targeted point. This is the great difference and improvement of the TREFIMET advanced thermal lance: it pierces forwards, as a drill would do.

TREFIMET has managed to develop advanced oxygen lance designs that offer the following advantages:

  • Energy is focused on the attack point, resulting in more accurate cuts or perforations.
  • Faster operations result in decreased operator’s exposure time and therefore increased safety.
  • Lower oxygen and lance consumptions.
  • Full length burning, thanks to its exclusive coupling system.
  • Less fumes and sparks are generated, making them easier to operate and your target is more visible.
  • Using TREFIMET advanced thermal lances, users will be benefit from improved equipment conditions, longer life cycles, reduced operational impacts, and increased operator safety.

Oxylance Thermic Torches or Exothermic Cutting equipment is an oxy/fuel cutting system that uses an alloyed steel pipe instead of a fuel gas to perform cutting operations. The Thermic Torch is consumed during the operation. Thermic Torches are more efficient on many materials because they burn at a tip temperature of 4000 c where an oxy/fuel gas torch has a tip temperature of 2700 c.

Exothermic cutting systems like the Oxylance Thermic Torches or Sure Cut Cutting Systems will cut virtually any metal, both ferrous and non-ferrous. Both the Large Burning Bars and the Sure Cut systems are faster than conventional oxy-acetylene or carbon arc gouging. Exothermic cutting requires no preheating or cleaning the material prior to cutting. It is easy to use and is cost effective for most applications. Unlike carbon arc gouging the Exothermic Cutting systems leaves no carbon residue on material being gouged. Additionally, the noise level of thermic torches compared to carbon arc gouging is a significant safety factor. The db rating for a Thermic Torch is below 95 decibels.

MINING INDUSTRY

The mining industry worldwide uses Exothermic Cutting or Thermic Lances for a wide variety of applications from smelter operations for opening tap holes and cutting slag as well as maintaining mining machinery and heavy equipment.

PIERCING FROZEN PINS

The Thermic Lance or Sure Cut system is ideal for removing frozen pins from heavy equipment. By piercing a hole through the center of the pin you heat the pin from the inside and then by removing material from the center of the pin you give it room to shrink for easy removal.

TIME WORK STUDY

Piercing a 32 mm od X 300 mm pin using 6 mm X 600 mm rod. Initial hole through the length of the pin took 16 seconds

Removing 100 mm diameter X 600 mm long pin from crane took 3 ea of the 9.5 mm X 900 mm Quick Connect rods. Initial pierce took 20 seconds. Increasing the hole in the center of the pin took additional 5 minutes. Cooling time and final removal, 25 minutes for a total of 30 minutes.

Removing a 125 mm X 400 mm pin from a paper mill roller: 6 each 9.5 mm X 1200 mm rods. Initial pierce took 35 seconds. Enlarging the hole enough for the pin to shrink took 15 minutes. Cooling time and removal took 30 minutes.

Cutting steel plate; Operators removing duct work from a coal fired power plant were able to cut up to 3 meters of 6 mm steel plate with one 9.5 mm X 1200 mm Sure Cut rod in 2 minutes.

Gouging a 20 mm fillet weld on 450 mm long welded joint took half of a 9.5 mm by 900 mm rod in less than 40 seconds. The 20 mm fillet was gouged to the root and the two pieces of plate were separated with one pass.

Cutting Stainless Steel Plate; 9.5 mm SS plate 1200 mm long cut in half in 2 minutes with one 9.5 mm X 1200 mm rod.

Heat Exchanger; 12 mm od Stainless Steel Tube Bundle 900 mm in diameter. 3 each 9.5 mm X 1200 mm QC rods. One complete cut through the heat exchanger took 6 minutes.

Aluminum Buss Bars; 50 mm thick X 200 mm wide aluminum buss bars cut in half with 1 each 9.5 mm X 600 rod in 45 seconds.

Although efforts to improve cut or perforation operations have been made by means of expensive mechanic (rotary or percussion) tools, it has not been possible to move away from using oxygen lances. In contrast, the performance and accuracy of the advanced thermal lances developed by companies such as TREFIMET has allowed the definite replacement of the traditional oxygen lances, thereby delivering the same result as if they have been carried out by a drill tip or a pneumatic hammer.

 

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