Science Teaching & Technology by Multimedia Science
Industrial Experience & the Science Classroom
The Electric Arc Furnace – Smoking is Bad for Your Health
After fifteen years as a chemical engineer, I made a career switch into high school science teaching. One of the pluses of entering the classroom from industry was that I could relate stories about the real world of work and use examples showing how the science was used during my career.
One of my favorite stories occurred in my first job working for Bethlehem Steel in Bethlehem. I was working in air pollution control and one of the problems I was assigned was cleaning up the electric arc steel furnace.
The electric arc steel furnace was used to make specialty steel like stainless steel. This furnace was several stories high, was filled with the steel making ingredients, and then three huge electrodes were lowered into the furnace. Electricity was used to melt the materials and while this was happening, the furnace’s top was open, and huge amounts of smoke rose upwards filling the furnace building.
Our engineering group’s assignment was to measure the velocity of the smoke as it left the furnace in order to design a ventilation system to remove the smoke. The first attempt to measure this velocity relied on a velocity measuring probe that could be placed in the rising smoke. You can probably guess who got the job of holding the probe.
Above the electric arc furnace was a movable platform crane that was used to load the material into the furnace. I was positioned on the platform with the velocity probe attached to a long pole so that it would extend over the railing and into the rising smoke. Unfortunately, I found that the crane did not stop or start smoothly, but jerked violently as the operator moved it back and forth trying to keep the probe in the smoke.
Well, I needed both hands to hold onto the probe and the box that indicated the results. But I also needed my hands to try to keep myself from either falling against the railing in front of me, which was red hot, or falling backwards into the electrical motor which would have fried me. There was also smoke all over the place rising into my face and into my eyes.
The end result was that I had to make a decision between falling into the furnace or letting go of the probe. I was able to watch it fall down into the furnace, disappearing into the semi-molten steel below.
OK, it was time for plan B. Somehow we got talking about our high school physics course where we measured the velocity of a moving object by using what is called a ticker or spark timer.
The moving object is attached to a piece of tape which runs through the timer. The timer makes marks on the tape at equal time intervals. These marks can then be measured to calculate the velocity or the acceleration of the moving object.
But how could this idea be applied in this situation? There was not any way to attach a piece of tape to the smoke! What we came up with was to hang a long 1 foot wide strip of aluminum from the ceiling along the side of the furnace. There were dots painted on the aluminum strip every meter. Then we blew up balloons and let them go, the balloons rising with the rising smoke. Finally, we took pictures of the balloon against the aluminum strip every second. What we ended up with was the vertical position of the balloon every second so that we could calculate its velocity.
While this worked, it was neither quick nor easy. The aluminum strip tended to blow around in the smoke and attract enough static electricity to give anyone holding it shock after shock. I found this out the hard way.
I find this story as a great introduction to the motion experiment using the ticker or spark timer. First, it answers to question, “When will we ever use this.” But it also illustrates the need for out of the box and creative thinking.
I use this story as part of my Click & Teach unit on Motion Graphing which is available at Teachers Pay Teachers.
Physics Motion Equations Unit – Click & Teach Bundle