Glass Melting Technology: A Technical and Economic ... - OSTI

SCM was developed by the Gas Institute (GI) of the National Academy of Sciences of
Ukraine and was commercialized a decade ago for mineral wool production in Ukraine
and Belarus. Five 75 ton/day melters are in operation. These commercial melters use
recuperators to preheat combustion air to 575°F. All melters operate with less than 10
percent excess air and produce NOx emissions of less than 100 vppm (at 0 percent O2)
along with very low CO emissions.
In SCM (shown below), fuel and oxidant are fired directly into the molten bath from
burners attached to the bottom of the melt chamber. High-temperature bubbling
combustion inside the melt creates complex gas-liquid interaction and a large heat
transfer surface. This significantly intensifies heat exchange between combustion
products and processed material while lowering the average combustion temperature.
Intense mixing increases the speed of melting, promotes reactant contact and chemical
reaction rates, and improves the homogeneity of the glass melt product. The melter can
handle a relatively non-homogeneous batch material. The size, physical structure, and
especially homogeneity of the batch do not require strict control. Batch components can
be charged premixed or separately, continuously or in portions.
Figure 3.A.1. Submerged Combustion Melter schematic.
A critical condition for SCM operation is stable, controlled combustion of the fuel within
the melt. Simply supplying a combustible fuel-oxidant mixture into the melt at a
temperature significantly exceeding the fuel’s ignition temperature is insufficient to
create stable combustion. Numerous experiments conducted on different submerged
combustion furnaces with different melts have confirmed this. Cold channels are formed
that lead to unstable combustion and excessive melt fluidization. A physical model for
the ignition of a combustible mixture within a melt as well as its mathematical
description show that for the majority of melt conditions that may occur in practice, the
ignition of a combustible mixture injected into the melt as a stream starts at a significant
distance from the injection point. This, in turn, leads to the formation of cold channels of
frozen melt, and unstable combustion. To avoid this type of combustion, the system must
be designed to minimize the ignition distance. This can be achieved in three ways: 1) by
flame stabilization at the point of injection using special stabilizing devices, 2) by
153