You can fire glass in a ceramic kiln, but it may require experimentation.
The first time we fired glass in a fusing seminar at Paragon, we used an 8-sided ceramic kiln with Kiln Sitter shutoff. The pieces turned out quite well.
Here are basic ideas that you could try:
1) Coat the shelves with kiln wash or glass separator. They must be smooth. Shelf imperfections will appear on the underside of glass.
2) Load several shelves evenly throughout the kiln. Position them so that you can see a shelf through each peephole. You will need to watch the glass as it fuses.
3) Draw a diagram of the kiln interior showing the position of each shelf and the elements. The diagram may help you to obtain more even firing the next time by changing the way you load the kiln if necessary.
4) The wider the side-fire ceramic kiln, the slower you must fire the glass. Experimentation will help you develop a firing schedule. If you fire too fast, the glass toward the outer edge of each shelf will fuse hotter than the glass toward the center. This is because the heat radiates toward the glass from the sidewalls. As you slow down the firing, the temperature throughout the kiln will become more uniform.
5) During the first 500 degrees F., leave out the peephole plugs and lift the lid to the venting position. After the venting period, insert the peephole plugs and lower the lid.
6) As the interior begins to turn dark red, watch the glass through the peepholes. Use firing safety glasses. Look at the glass more frequently the closer the glass gets to its fusing temperature.
6) When the glass has fused, turn off the kiln and allow it to cool to room temperature.