A 20-L Furnace Test Method
to Determine the Combustion Gas Toxicity of Conveyor Belts

Maria I. De Rosa

U.S. Department of Energy
Pittsburgh Research Center
Pittsburgh, PA 15236

Under the U.S. Bureau of Mines, experiments were conducted with mine conveyor
belt samples in a 20-L furnace (1 g sample) and in a laboratory fire tunnel
{approximately 3,000 g sample) to measure and compare the major toxic gas
concentrations evolved during the combustion of the materials (1). The toxic
gas concentrations, measured simultaneously through a multi-port sampling device and
treated as yield values, included hydrogen chloride (HC1), hydrogen cyanide (HCN),
oxides of nitrogen (NO, treated as NO,), and carbon monoxide (CO).

The toxic gas yields measured in the 20-L furnace system are in good agreement
with similar yields measured in the laboratory fire tunnel system. Thus, either
system could be used to obtain the gas yield data for conveyor belts. However, the
20-L furnace system is preferred due to the smaller sample size and less time
required to set up and run an experiment. Good and direct correlations were found
between the percentage of chlorine, nitrogen and carbon contained in the original
materials and the HC], HCN, NO,, and CO gas yields. Both experimental systems
produced essentially the same results. The greater the percentage of chemical
contents, the higher were the corresponding toxic gas yield values.

Results also show that polyvinyl chloride (PVC) belts released higher HC1
concentrations because of the higher chlorine content while the styrene-butadiene
rubber (SBR) belts released higher CO, HCN, and NO, concentrations because of the
higher carbon and nitrogen contents.

Using the toxic gas yield data, a toxicity index (TI) parameter was calculated
for each belt material. The TI is a measure of the potential gas toxicity that a
belt can produce during a fire; the higher the TI value, the greater is the
potential toxicity. As expected, the TI was the highest for the PVC belts (1.06 and
1.22 m°/g for sample Pl, using the gas yields measured in the 20-L furnace and fire
tunnel, respectively), and the lowest for the SBR belts (0.39 and 0.43 m°/g for
sample S2, using the gas yields measured in the 20-L furnace and fire tunnel,
respectively). Also, using the TI values and a ratio of average mass loss burning
rates to ventilation airflow rates, a toxicity hazard (TH) parameter was calculated
for each belt material. The TH estimates the level of toxic gas hazard produced by
a burning belt in a ventilated system. In some cases, the mass loss burning rates
may be sufficiently great that a belt with a low TI actually produces a more severe
toxic gas hazard than a belt with a much higher TI. For example, using the ratio of
mass loss burning rates to ventilation airflow rates measured in the fire tunnel
system, the TH value calculated for belt S2, whose TI is 60 pct lower than the TI
for belt Pl, was higher (6.8) than the TH value calculated for belt Pl (6.1) because
of the greater mass loss burning rate of belt S2.

REFERENCE

1. De Rosa, M.I. A 20-L Furnace Test Method to Determine the Combustion Gas
Toxicity of Conveyor Belts. DOE RI 9626, 1996, 20 pp.

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Sampling
ports

Flowmeters

Furnoce

Impingers with Sampling

solutions

Temperoture
control Heating
element

Dota
ocquisition

To exhous!

To exhaust
4 Thermocouples

Flowmeters

Sompling
bag

Impingers with
solutions

igniter

ocquisition

Figure a: 20-L Furnace experimental system.
b: Laboratory fire tunnel experimental system.

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