EPA/600/A-93/187
Evaluation of Carbon Black Slurries as Clean Burning Fuels
by
Ravi K. Srivastava*
Acurex Environmental Corporation
4915 Prospectus Dr.
Durham, NC 27713
William P. Linak
Combustion Research Branch, MD-65
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
April 14,1993
Prepared for presentation at the
86th Annual Meeting
Air & Waste Management Association
Denver, CO
June 13-18,1993
* Corresponding author
Tel: (919) 541-2692
Fax: (919) 541-1887

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Abstract
The Hydrocarb process is being evaluated as a method of producing methanol, hydrogen-rich fuel gas, and
carbon black from coal, biomass, or municipal waste feedstocks. Since carbon black has significant heating value
(33.78 x 106 J/kg, 14,100 Btu/Ib) and contains neither sulfur, nitrogen, nor inorganic ash, there is potential for its
use as a clean burning fuel or fuel extender in boilers and industrial furnaces. To obtain a preliminary assessment of
this potential, a series of experiments was performed to examine the pumpability, atomization, and combustion
characteristics of slurries made of mixtures of carbon black with No. 2 fuel oil and methanol. Carbon black/No. 2
fuel oil and carbon black/methanol slurries with carbon black contents of up to 50 and 45 weight percent,
respectively, were pumped and atomized by means of a peristaltic pump and air atomizing scheme and burned in an
82 kW (280,000 Btu/hr) laboratory combustor. Measurements of slurry spray droplet size distributions indicated
mean droplet diameters of approximately 100 and 30 |im for the carbon black/No. 2 fuel oil and carbon
black/methanol mixtures, respectively. Particulate emissions from the combustion of slurries containing 47 weight
percent carbon black in No. 2 fuel oil and 42 weight percent carbon black in methanol were approximately 40 and 28
mg/dsm3, respectively. These particulate emissions are significantly higher than corresponding emissions from
"base case" No. 2 fuel oil and methanol tests (0.75 and 0 mg/dsm3, respectively). However, in spite of the increased
particulate emissions, carbon monoxide emissions from all tests were similar (less than 50 ppm dry, corrected to 0
percent oxygen, for furnace stoichiometric ratios of 1.05 or greater). In addition, at 20 percent excess air, nitric oxide
emissions from the combustion of the carbon black/No. 2 fuel oil and carbon black/methanol (approximately 50 and
15 ppm, respectively) were significantly lower than those measured from the combustion of No. 2 fuel oil and
methanol (105 and 30 ppm, respectively).
Introduction
The Hydrocarb process (Steinberg, 1987, 1990; Steinberg et al., 1991; Borgwardt, 1992) is
being evaluated by the U.S. Department of Energy and U.S. Environmental Protection Agency as a two-step method
for converting carbonaceous raw materials to particulate carbon and hydrogen-rich fuel gas or synthesis gas. In the
first step of the process, carbonaceous raw materials, such as coal, biomass, or municipal wastes, are hydropyrolized
to yield methane-rich process gas with smaller equilibrium concentrations of carbon monoxide (CO), carbon dioxide
(CO2), water (H2O), hydrogen sulfide (H2S), nitrogen (N2), and solid ash residue. In the second step, methane is
thermally cracked to produce fine particulate carbon (carbon black) and hydrogen gas. A portion of the hydrogen-rich
gas is recycled to the hydropyrolizer, while the remaining is withdrawn as a clean medium heating value fuel gas or
converted to methanol.
The carbon black product from the thermal cracking step has an average particle size between 1 and 2 jim
diameter and is essentially free of ash, sulfur, oxygen, and other impurities. Since carbon black has significant
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heating value (32.78 x 10^ J/kg, 14,100 Btu/lb), it can be burned as a powder, in a manner similar to burning
pulverized coal, or it can be slurried for use in liquid fuel combustors. Alternatively, portions of the carbon black
can be sequestered to reduce the atmospheric CO2 burden. In contrast to energy intensive coal gasification or
liquefaction processes, Hydrocarb's hydropyrolysis (endothermic) and thermal cracking (exothermic) steps result in a
relatively overall energy neutral process.
In a preliminary assessment of carbon black for use as a fuel, Koppel et al. (1988) describe results of
differential thermogravimetric analyzer (DTGA) tests. Their results show that carbon black's lack of a volatile
component requires higher ignition temperatures (approximately 660 °C) for stable combustion compared to those
typically required for a pulverized high volatile bituminous coal (approximately 400 °C). However, this study also
concluded that, because of its small particle size, carbon black's burning rate was higher than that of a high volatile
bituminous coal.
Preparation procedures and physical, thermal, and theological properties of slurries of carbon black with
water, methanol, and oil have been documented by Wei and Steinberg (1989). In addition, general combustion
properties of slurries made of mixtures of carbon black and JP-I0 (aviation fuel) have been examined in bench scale
gas turbine combustors (Bruce et al., 1979; Bruce and Mongia, 1980) and well-stirred reactors
(Salvesan, 1979). These studies have shown that, to attain good combustion efficiencies, carbon black slurries
require greater residence times than those needed by conventional liquid fuels.
Mechanisms of carbon black slurry combustion have been examined to gain a better understanding of these
residence time requirements. Szekely and Faeth (1982a, 1982b) have shown that, for slurries made of
mixtures of carbon black and JP-10, combustion of individual slurry droplets (400-1000 Jim diameter) in a turbulent
diffusion flame is a two stage process, similar to combustion of coal slurries. In the first stage, the slurry liquid
evaporates leaving a porous agglomerate of carbon black particles. In the second stage, the carbon black agglomerate
bums in a similar manner as a coal char particle. Measurements showed that heat-up and combustion times for these
agglomerates required 90 to 95 percent of the slurry droplet's lifetime. As with coal char combustion, post flame
quenching of the carbon black agglomerate yields poor carbon burnout Motivated by these findings, flat flame
burner studies of agglomerate combustion have been conducted (Szekely and Faeth, 1982a, 1982b; Szekely
et al, 1984). In the first of these studies, agglomerate temperature, diameter, mass, and velocity were measured
as a function of residence time for initial agglomerate sizes representative of practical combustion conditions (10-75
(im diameter). These measurements were compared with a variable-density, shrinking-sphere agglomerate reaction
model and shown to correlate satisfactorily. The study concluded that the density of the agglomerates and the
empirical parameters used in the model varied with the extent of carbon reaction, but these variables were relatively
independent of the initial agglomerate diameter and flame conditions. The second study extended these investigations
to include blends of carbon black particles of different sizes. The combustion of blends containing 50 weight percent
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each of 70 and 300 nm particles was found to take 10 to 50 percent longer than monodisperse panicles at similar
combustion conditions. However, it was concluded that improved atomization through proper blending would
produce smaller droplet sizes, and smaller agglomerates would reduce residence time requirements.
To provide a preliminary assessment of the issues associated with the use of carbon black slurries as fuels
for boilers and industrial furnaces, the U.S. EPA's Air and Energy Engineering Laboratory (AEERL) conducted a
series of pilot-scale tests based on carbon black slurry samples provided by the U.S. DOE's Brookhaven National
Laboratory (BNL). In these tests, pumpability, atomization, and combustion characteristics of these sluiries were
examined using an 82 kW (280,000 Btu/h) horizontal tunnel combustor. These results are intended to complement
previous smaller scale research efforts examining properties and combustion characteristics of carbon black slurries,
and provide data for future larger scale combustor-fuel development efforts. Specific objectives include evaluation of
pumping and atomization potentials for several carbon black formulations with No. 2 fuel oil, methanol, and water;
examination of maximum pumpable slurry concentrations; assessment of flame ignition and stability; and
quantification of gaseous and particulate pollutant emissions as functions of excess oxygen.
Experimental Approach
Combustion Apparatus
Experiments were performed using the small semi-industrial scale 82 kW (280,000 Btu/hr, rated) horizontal
tunnel combustor illustrated in Figure 1. This 396.2 cm (156 in.) long, modular, steel-shell, refractory-lined
research combustor was designed for the evaluation and characterization of fuels and combustible wastes. The 50.8
cm (20 in.) inside diameter (I.D.) burner section allows near-burner zone aerodynamic simulation of natural gas and
fuel oil flames. Quartz observation windows permit visualization of flame shapes, spray patterns, and burner
operation. Following the burner section, the 25.4 cm (10 in.) LD. back sections are equipped with numerous access
ports permitting temperature measurements, time (position) resolved gaseous and aerosol sampling, and injection of
various agents. However, for the research results presented here, gaseous and particulate samples were taken only
from the stack locations indicated in Figure 1. These sampling locations are downstream of a water-cooled heat
exchanger designed to protect the 20.3 cm (8 in.) I.D. stainless steel exhaust stack from excessive heat. From the
experimental unit, exhaust gases are routed to a central facility air pollution control system (APCS) consisting of an
afterburner, water quench, baghouse, and acid gas scrubber. The APCS is designed to control air emissions and meet
the requirements of the facility's Resource Conservation and Recovery Act (RCRA) Research, Development, and
Demonstration (RD&D) and air pollution permits.
Fuels and combustion air are introduced into the burner section through an International Flame Research
Foundation (IFRF) type moveable block variable air swirl burner. Air swirl is controlled by adjustment of the
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internal block spacing, permitting various turbulent diffusion flame types (shapes) to be generated ranging from long
axial (type A) low swirl flames to short bushy (type C) high swirl flames. Fuel is introduced through an
interchangeable injector, positioned along the center axis of the burner. Swirling air, passing through the annulus
around the fuel injector, promotes flame stability and attachment on the water-cooled quarl. For the research results
presented here, however, only one flame type was examined. This high swirl (type C) flame with internal
recirculation was produced with a burner block setting of 7 (on a 0 to 8 scale), resulting in a Swirl Number of
approximately 1.48 as defined by Beer and Chigier (1983).
To accommodate the atomization of viscous slurries, a special twin fluid (air atomizing) injector was
constructed. As shown in Figure 2, this injector incorporates a central fuel/slurry tube and annular atomizing air.
A convergent tip promotes fuel/slurry atomization. Flow rates of the fuel/slurry and atomizing air streams are
controlled independently. As mentioned above, the development of a slurry pumping and atomization system was an
objective of this research, and is further discussed below.
Gas samples extracted from the stack location identified in Figure 1 are continuously analyzed to
determine concentrations of the combustion gases; oxygen (C>2), CO, CO2, and nitrogen oxide (NO). These routine
continuous emission monitor (CEM) measurements are made to verify combustion conditions, maintain steady-state
requirements, monitor pollutant species, and serve as independent checks of air and fuel flows. In addition to CEMs,
selected combustion tests quantified particulate emissions by EPA Modified Method 5 (U.S. EPA, 1986).
Several unshielded thermocouples are located along the length of the furnace to monitor centerline gas temperatures.
One such thermocouple is located in the burner section, 22.9 cm from the burner quarl. Temperatures monitored at
this location determine the characteristic combustion temperature reported in later sections.
Carbon Black Slurries
Table 1 describes the five carbon black slurry samples received from Brookhaven National Laboratory, and
included for testing. In these samples, carbon black is mixed with No. 2 fuel oil or methanol to act as a fuel
extender or mixed with water to produce a "pumpable liquid" fuel for potential boiler and industrial furnace
applications. These slurries are identified in Table 1 as samples 1-5. To provide baseline comparisons,
experiments with unadulterated "base case" No. 2 fuel oil (sample A) and methanol (sample B) were also planned. In
addition, tests were included to examine slurry mixtures with higher concentrations of carbon black (within pumping
and atomizing limits). These additional samples are identified as A1 and A2, and B1, B2, and B3 to represent
additional carbon black/No. 2 fuel oil and carbon black/methanol mixtures, respectively. No additional caibon
black/water slurries were examined. Table 2 summarizes the 12 carbon black mixtures considered.
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Development of a Slurry Pumping and Atomization System
To augment the 1 L slurry samples received from Brookhaven National Laboratory, a commercial carbon
black was purchased and additional quantities of slurries were formulated per the information given in Table 1. Of
the five slurries received for evaluation, sample 4, the carbon black/No. 2 fuel oil formulation (see Table 1)
seemed most promising in terms of its heating value and potential ignitability (high volatile content). In addition,
based on its relatively high viscosity (see Table 1), sample 4 would also likely be more difficult to pump and
atomize than samples 1,2, or 3 (sample 5 presented unique problems). Based on these considerations, the
development of a pumping and atomizing scheme was initiated using sample 4. As expected, sample 4 appeared
fairly viscous (similar to thick pancake batter) and did not flow freely. In addition, it was believed that the presence
of the carbon black particles in suspension made this slurry abrasive to pumping equipment analogous to similar
behavior seen for coal-water slurries (Miller and Schmidt, 1984). Several types of pumps were evaluated,
including diaphragm, screw, and gear types. None of these pumping systems were successful in pumping this
slurry. In all such trials, persistent clogging of pump flow passages and/or erosion of pump seals occurred. Finally,
a peristaltic pump was tried and found to provide reliable, adjustable, and accurate flows and pressures through
nominal 0.64 cm (0.25 in.) flexible Tygon tubing. In this type of pumping arrangement, component erosion is
eliminated by preventing contact between slurry and pump parts. Peristallic pumps have been used previously to
pump coal-water slurries in small scale applications (Breault et al., 1991).
Efforts were made to obtain pressure atomization nozzles suitable for slurry applications. Unfortunately
none of the manufacturers contacted offered such nozzles within the design flow rates and existing burner dimensions.
In addition, none of the available hollow cone or centrifugal pressure nozzles typically used for distillate fuel oil
atomization were suitable for use with the slurry. Experiments with these designs quickly ended with high pressure
drops and nozzle clogging. Twin-fluid atomizers, however, have been used previously to atomize coal-water slurries
(Sommer and Melick, 1991), and a technique based on the modified designs described by Marshall (1954)
was employed here. This design uses compressed air to disintegrate a stream of viscous fluid. The fabricated twin-
fluid atomizer is illustrated in Figure 2. Together, the peristaltic pump and twin-fluid atomizer were used to
produce a fine spray for a slurry flowrate of approximately 5.6 kg/hr (required to yield a 58.6 kW firing rate for
sample 4). The atomizing air flow and pressure required for this atomization arrangement were approximately 28.6
L/min and 205.52 kPa, respectively.
It should be noted that the pumping and atomizing system developed here describes just one successful
method of delivering these slurries for these laboratory scale tests. It is likely that other pumping and atomizing
arrangements are possible, especially at larger scale. However, the dimensions of the small IFRF type burner used
here severely limited the tubing sizes and nozzle diameters that could be used. These small spaces prevented the use
of pressure atomizing devices and likely promoted plugging, high pressure drops, and premature pump wear. In fact,
it is unlikely that a peristaltic pump arrangement would be suitable or practical for larger scale applications.
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Table 2 identifies 12 samples for which pumping and atomizing tests were conducted using the peristaltic
pump and twin-fluid atomizer described above. As mentioned previously, these samples include the five samples
received from Brookhaven National Laboratory, "base case" No. 2 fuel oil and methanol samples, and five additional
carbon black/fuel formulations included to examine pumpability limits. As seen in Table 2, the three carbon
black/water and carbon black/water/No. 2 fuel oil slurries (samples 1,3, and 5) were not pumpable. These slurries
were too viscous to flow within the pumping arrangement. Likewise, efforts to pump samples A2 and B3 (samples
containing highest carbon-black concentrations) produced similar results. Sample B2, a 50/50 mixture of carbon
black and methanol would flow; however, its atomization resulted in unstable uncontrollable flow rates. The six
remaining samples (A, 4, Al, B, 2, Bl) were each pumpable and could be atomized to produce suitable sprays for
further combustion testing. Table 2 summarizes atomizing air pressures, flow rates, and siurry flow rates for these
six samples to yield a nominal 58.6 kW (200,000 Btu/hr) combustor load. Samples AI and Bl represent the
maximum carbon black concentrations in No. 2 fuel oil and methanol, respectively, that could be pumped and
atomized with the chosen pumping and atomizing arrangement. No further efforts were made to examine carbon
black/water mixtures. It should be noted that this study did not examine the effects of numerous dispersants or
stabilizers that might be added to improve the fuel handling properties. It is likely that the proper selection of these
additives may have permitted the pumping of the carbon black/water mixtures and improved the characteristics of the
No. 2 fuel oil and methanol samples. However, a parametric examination of dispersants and stabilizers was deemed
to be outside the scope of this research.
While the particle size distribution (PSD) of the atomized slurry is a function of many factors including
slurry viscosity, surface tension, density, fluid velocities and flow rales, and measurement location, Figure 3
presents typical droplet PSDs produced by the pneumatic atomizer shown in Figure 2 for the six pumpable
samples. These droplet PSDs were measured with a Fraunhofer diffraction particle sizing technique (Cornillaut,
1972; Swithenbank et al., 1977), using the slurry and atomizing air flow rates presented in Table 2. The
sampling location was 10.16 cm from the nozzle tip. Figure 3 shows that both the No. 2 fuel oil and methanol
(solid symbols) produce distributions with similar mean particle size (approximately 40 Jim diameter). The
methanol, however, produces a slightly narrower distribution. In comparison to the "base case" PSDs, the PSDs for
the slurries (open symbols) are most interesting. Both carbon black/No. 2 fuel oil mixtures produce PSDs with
larger mean diameter (approximately 100 jim) compared to the base case No. 2 fuel oil. Conversely, both carbon
black/methanol mixtures produce PSDs with mean diameters (approximately 30 (im) slightly smaller than the base
case methanol. This behavior is likely due to differences in viscosity, surface tension, and density between the
samples (Marshall, 1954). The PSDs produced, however, indicate effective atomization and the production of
fine sprays for the six pumpable slurries.
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Combustion Emissions
Before each combustion tesl, the combustor was fired (preheated) overnight using natural gas (58.6 kW).
Prior to the introduction of a slurry, the natural gas flame was turned off, and the gas injector replaced with the
pneumatic atomizer. A small secondary pilot flame (28.3 L/min natural gas, 331.6 L/min air) was established at a
location perpendicular to the burner flow to provide an ignition source (see Figure 1). Next the combustion air,
slurry, and atomizing air flows were established. Finally, after a stable flame was visually confirmed, the pilot
flame was shut off. All six samples tested produced stable self-sustaining flames.
Figures 4, 5, and 6 present the CO, NO, and characteristic combustor temperatures, respectively,
measured for the six samples tested as functions of excess air values ranging from 0 to 55 percent. A combustor
load of 58.6 kW was maintained for all tests. CO and NO concentrations are presented dry, corrected to 0 percent
oxygen. Combustor temperatures have not been corrected for radiation effects. Comparison of CO emissions
(Figure 4) between the base case No. 2 fuel oil and methanol tests and their corresponding carbon black slurries
indicates similar behavior. No difference was seen in CO emission between the base case fuels and slurries. With
excess air values greater than 5 percent, CO emissions were consistently less than 50 ppm for all samples tested.
These emissions are similar to those produced by the combustion of a medium volatile pulverized bituminous coal
in a dry bottom boiler (U.S. EPA, 1988).
Figure 7 presents particulate emissions taken from four samples. These data are presented dry as measured
(20 percent excess air). In contrast to the CO data, the particulate data show significant differences between the base
case fuel and carbon black slurries. While No. 2 fuel oil and methanol produce particulate emissions of 0.75 and 0
mg/dm3, respectively, the two carbon black/No. 2 fuel oil and carbon black/methanol slurries examined produce
substantially increased particulate emissions of 40 and 28 mg/dm3, respectively. Presumably, these increased
emissions are the result of incomplete carbon burnout. For comparison, uncontrolled combustion of a medium
volatile pulverized bituminous coal in a dry bottom boiler at 50 percent excess air with a nominal 10 percent ash
content would produce particulate emissions of approximately 500 mg/dm3 (U.S. EPA, 1988).
In contrast to the increased particulate emissions shown in Figure 7. Combustion of the sluny samples
produced reduced emissions of NO compared to the base case fuels. Figure 6 shows that at 20 percent excess air,
NO emissions from the carbon black slurries are approximately half of the emissions from the corresponding base
case fuels (50 vs. 105 ppm for No. 2 fuel oil, and 15 vs. 30 ppm for methanol). Also, the NO emissions for the
slurries are less dependent on excess air level compared to the base case fuels. These results are consistent with a
fuel staging mechanism to limit NO formation. The carbon black likely acts to delay combustion, thereby limiting
peak temperatures and thermal NO formation. Since carbon black and methanol contain no fuel bound nitrogen, and
No. 2 fuel oil contains very little (approximately 0.02 weight percent), it is unlikely that mechanisms involving
fuel bound nitrogen are responsible. However, the characteristic combustion temperatures presented in Figure 6 do
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not show significant differences at the one location measured. Uncontrolled combustion of a medium volatile
pulverized bituminous coal in a dry bottom boiler at 50 percent excess air would produce NO emissions of
approximately 750 to 1250 ppm depending on the fuel nitrogen content (U.S. EPA, 1988).
Summary
Of the 12 samples proposed for testing, 6 samples including base case No. 2 fuel oil and methanol, and 2
mixtures each of carbon black/No. 2 fuel oil and carbon black/methanol were suitable for combustion experiments.
These slurries with carbon black contents of up to 50 and 45 weight percent, respectively, were pumped and atomized
by means of a peristaltic pump and air atomizing scheme and burned in an 82 kW laboratory combustor. Higher
carbon black concentrations were examined, but were not pumpable, nor were any of the carbon black/water mixtures
tested. Measurements of slurry spray droplet size distributions indicated mean droplet diameters of approximately
100 and 30 |im for the carbon black/No. 2 fuel oil and carbon black/methanol mixtures, respectively. Particulate
emissions from the combustion of slurries containing 47 weight percent carbon black in No. 2 fuel oil and 42
weight percent carbon black in methanol were approximately 40 and 28 mg/dsm^, respectively. These particulate
emission are significantly higher than corresponding emissions from the base case No. 2 fuel oil and methanol tests
(0.75 and 0 mg/dsm3, respectively) and likely result from incomplete carton burnout. However, in spite of the
increased particulate emissions, CO emissions from all tests were similar (less than 50 ppm dry, corrected to 0
percent oxygen, for furnace stoichiometric ratios of 1.05 or greater). In addition, at 20 percent excess air, NO
emissions from the combustion of the carbon black/No. 2 fuel oil and carbon black/methanol (50 and 15 ppm,
respectively) were significantly lower than those measured from the combustion of No. 2 fuel oil and methanol (105
and 30 ppm, respectively).
The results from these experiments indicate that carbon black slurries are difficult to pump and atomize, and
when burned produce significantly increased particulate emissions compared to conventional liquid fuels. However,
measured NO emissions were notably lower compared to the same liquid fuels.
Acknowledgments/Disclaimer
Portions of this work were conducted under EPA Contract 68-DO-0141 with Acurex Environmental Corp.
The research described in this article has been reviewed by the Air and Energy Engineering Research Laboratory, U.S.
Environmental Protection Agency, and approved for publication. The contents of this article should not be construed
/
to represent Agency policy nor does mention of trade names or commercial products constitute endorsement or
recommendation for use.
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References
Beer, J.M, and Chigier, N.A., Combustion aerodynamics, Robert E. Krieger Publishing Co., Malabar, FL (1983),
Borgwardt, R.H., "A technology for reduction of CO2 emissions from the transportation sector," Energy Convers.
Mgml., 33(5-8), 443-449 (1992).
Breault, R.W., Grimanis, M.P., and Zografos, A.I., "Effect of coal type and benefaction process on storage,
handling, and atomization," 7th Annual Coal Preparation, Utilization, and Environmental Control Contractors
Conference Proceedings, Pittsburgh, PA, July (1991).
Bruce, T.W., Mongia. H.C., Steams, R.S., Hall, L.W., and Faeth, G.M., "Formulation properties and combustion
of carbon slurry fuels," Proceedings of Sixteenth JANNAF Combustion Meeting, CPIA Pub. No. 308,679-717
(1979).
Bruce, T.W. and Mongia, H.C., "Compound cycle turbofan engine task IX: carbon slurry fuel combustion
evaluation program," Air Force Wright Aeronautical Laboratories AFWAL-TR-80-2-35, March (1980).
Cornillaut, J., "Particle size analyzer," Appl. Opt,, 11(2), 265-268 (1972).
Koppel, PJE., Steinberg, M., and Grohse, E.W., "Economical clean carbon fuel," Power-Gen '88 Exhibition and
Conference for Solid and Fossil Fuel Power Generation, Orlando, FL, December (1988).
Marshall, W.R. Jr., "Atomization and spray drying," AIChE Monograph Series (1954).
Miller, J.E. and Schmidt, F„ eds., "Slurry erosion, uses, applications, and test methods," ASTM Special Technical
Publication 946, June (1984).
Salvesan, R.H., "Carbon slurry fuels for volume limited missiles," Air Force Aeronautical Propulsion Laboratories
AFAPL-TR-79 -2122, November (1979).
Sommer, T.M. and Melick, T.A., "Utilization of coal-water fuels in fire tube boilers," 7th Annual Coal
Preparation, Utilization, and Environmental Control Contractors Conference Proceedings, Pittsburgh, PA, July
(1991).
Steinberg, M., "The Hydrocarb process - conversion of carbonaceous materials to clean carbon and gaseous fuel,"
Brookhaven National Laboratory Report 40731 (1987).
Steinberg, M,, "Biomass and Hydrocarb technology for the removal of atmospheric CO2," Brookhaven National
Laboratory Report 44410 (1990).
Steinberg, M., Grohse, E.W., and Tung, Y„ A feasibility study for the coprocessing of fossil fuels with biomass by
the Hydrocarb process," EPA-600/7-91-007 (NTIS DE91-011971), U.S. EPA, Air and Energy Engineering
Research Laboratory, Research Triangle Park, NC (1991).
Swithenbank, J., Beer, J.M., Taylor, D.S. Abbot, D., and McCreath, G.C., "A laser diagnostic technique for the
measurement of droplet and particle size distribution," Prog. Astronaut. Aeronaut,, 53,421-447 (1977).
Szekely, G.A, Jr. and Faeth, G.M, "Combustion properties of carbon slurry drops," AIAA /„ 20(3), 422-429
(1982a).
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Szekely, G.A. Jr. and Facth, G.M., "Reaction of carbon black slurry- agglomerates in combustion gases," 19th
Comb. (Im.) Symp., Comb. Inst., Pittsburgh, 1077-1085 (1982b).
Szekcly, G.A. Jr., Turns, S.R., and Facth, G.M., "Effects of carbon-black properties on combustion of carbon-black
slurry agglomerates," Combust. & Flame, 58, 31-43 (1984).
Wei, G. and Steinberg, M., "Carbon black slurries preparation and characteristics," Brookhaven National Laboratory
Report 43732, December (1989).
U.S. EPA, Method 0010, modified method 5 sampling train in "Test methods for evaluating solid waste, vol. II:
field manual physical/chemical methods, 3rd ed.," EPA-SW-846 (NTIS PB88-239223), U.S. EPA, Washington,
DC (1986).
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PB89-128631), Supplement B (1988).
Table 1. Carbon black slurry samples received from Brookhaven National Laboratory.
Sample
Composition
Heating value
Viscosity
Density

(weight %)
(106 J/kg)
(cp)
(a/cm3)
1
44% CBV55% water/1% No. 2 fuel oil
14.65
75
1.30
2
42% CB/58% methanol
26.17
51
1.06
3
51% CB/49% water
16.70
118
1.34
4
47% CB/53% No. 2 fuel oil
37.98
140
1.18
5
60% CB/40% water
19.70
752
1.43
Carbon black.
Table 2. Pumping and atomizing results for various fuel and carbon black slurries.1
Sample
Composition
Slurry
Atomizing
Atomizing
Remarks

(weight %)
flow rate
air pressure
air flow rate



(g/min)
(kPa)
(m3/hr)

A
100% No. 2 fuel oil
81.19
192.32
1.68

4
47% CB2/53% No. 2 fuel oil
92.69
205.42
1.72

Al
50% CB/50% No. 2 fuel oil
93.68
210.24
1.73

A2
55% CB/45% No. 2 fuel oil
-
-
-
unable to pump/atomize
B
100% methanol
156.02
188.88
1.68

2
42% CB/58% methanol
134.54
206.11
1.72

B1
45% CB/55% methanol
133.63
217.82
1.80

B2
50% CB/50% methanol
131.51
-
-
unstable flow
B3
60% CB/40% methanol
-
-
-
unable to pump/atomize
1
44% CB/55% water/1% No. 2 fuel oil
-
-
-
unable to pump/atomize
3
51% CB/49% water
-
-
-
unable to pump/atomize
5
60% CB/40% water
-
-
-
unpumpable
1 Samples A and B represent unadulterated "base case" fuels. Samples 1,2,3,4, and 5 correspond to Hydrocarb
samples received from Brookhaven National Laboratory. Samples Al, A2, B1, B2, and B3 represent other carbon
black/fuel compositions. Based on pumping and atomizing results, samples A, 4, Al, B, 2, and B1 were determined
suitable for further experimentation as combustion fuels. Samples Al and B1 represent maximum carbon black
concentrations that could be successfully atomized.
^Carbon black.
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A To air pollution control system

Gas sample
port
Igniter/pilot flame
Quartz observation windows
Modular refractory
sections
IFRF moveable block
burner
Atomizing air
Carbon black slurry
Combustion air
39.37 in.
Thermocouple
Figure 1.
EPA horizontal tunnel combustor.

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Injector tip
Slurry tube
center support fins
Injector tube
Atomizing air
T
15.875 mm 5.334 mm
0.625 in. 0.21 In.
i
Slurry tube
5.08 mm/0.20 In.
6.35 mm/0.25 In.

m.
W/M
- Injector tube length - 45.7 cm/18 in.
2.54 cm
Carbon black slurry
1 in.
H
Figure 2.	Fuel/slurry air atomizing injector.

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c
ffi
2
0)
CL
sz
D)
1®
10
8,
(a) carbon biack/No. 2 fuel oil droplet PSD
• No. 2 fuel oil
d 47% carbon black/53% fuel oil ^ p
A 50% carbon black/50% fuel oil A A
(b) carbon black/methanol droplet PSD
• methanol
~ 42% carbon black/ g ^
fl
58% methanol
A 45% carbon black/ 0
55% methanol
0
i
B
fl-
6
B«
6 •
6 €
&
i i i i i
10
100
1000
Particle diameter (jim)
Figure 3. Fuel/slurry droplet particle size distributions produced by the fuel/slurry air atomizing injector.
14

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1500 —
1250 J
1000:
(a) carbon black/No. 2 fuel oil mixtures
• No. 2 fuel oil
O 47% carbon black/53% No. 2 fuel oil
A 50% carbon black/50% No. 2 fuel oil
6
750.
500
250:
x*
offlrm* ^3 . rofl—.—fui,—go , ~, t\ n
1500
1250
1000 J
750
500
250 4
(b) carbon black/methanol mixtures
• methanol
~ 42% carbon black/58% methanol
A 45% carbon black/55% methanol
L. .......
0 10 20 30 40 50 60
Calculated excess air (%)
Figure 4.	Carbon monoxide emissions versus excess air for six fuel/slurry mixtures.
15

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150
125
ioo:
75
50
25 J
IP1

~
~
A
rP
~
O
A
150.
125.
100.
75
50
25J
(a) carbon black/No. 2 fuel oil mixtures
• No. 2 fuel oil
~ 47% carbon black/53% No. 2 fuel oil
A 50% carbon black/50% No. 2 fuel oil
(b) carbon black/methanol mixtures
• methanol
~ 42% carbon black/58% methanol
A 45% carbon black/55% methanol

~0
A
—T—
10
20
30
A
—i—
40
50
Calculated excess air (%)
60
Figure 5.
Nitric oxide emissions versus excess air for six fuel/slurry mixtures.
16

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1600
(a) carbon black/No. 2 fuel oil mixtures
• No. 2 fuel oil
~ 47% carbon black/53% No. 2 fuel oil
A 50% carbon black/50% No. 2 fuel oil
1500 4
1h
1400
1300
1600
A *
* a • B
A
~
—r
(b) carbon black/methanol mixtures
• methanol
~ 42% carbon black/58% methanol
i	A 45% carbon black/55% methanol
1500. a
n
A
1400.
1300
• /
O#
~
~	A	D
A
~
—i	1	.	1 	»	1	<	1-	-¦	-	i	1—
0 10 20 30 40 50 60
Calculated excess air (%)
Unshielded centeriine combustion chamber temperatures versus excess air for six fuel/sluny
mixtures.
17

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go
-J
Particulate emissions (mg/dsm3)
o
No. 2 fuel oil
o
CO
0
1
o

47% carbon black/53% No.2 fuel oil j
'.'.'A'.'.',','.1.1."" .v.1 ,.1,' ¦	m i ¦>>>.>. .>.>.1.1.1
Ol
o
ro
o
-o
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0 TECHNICAL REPORT DATA
Pi IL il.lt J-,- Jr~ 1U4 U (Please read luttructions on the re terse before complci
	
1 RfcPORT NO. 2.
EPA/600/A-93/187
3.
4. TITLE AND SUBTITLE
Evaluation of Carbon Black Slurries as Clean Burning
Fuels
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
?. AUTHOB(S)
R.K. Srivastava (Acurex) and W. P. Linak (EPA/
AEERL)
8, PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Acurex Environmental Corporation
4915 Prospectus Drive
Durham, North Carolina 27713
10, PROGRAM ELEMENT NO,
11. CONTRACT/GRANT NO.
68-DO-0141
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory-
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper; 1/91-1/93
14. SPONSORING AGENCY CODE
EPA/600/13
15. supplementary NOTesAEERL project 0fficer is William P. Linak, Mail Drop 65, 919/
541-5792. For presentation at 86th Annual Meeting, AWMA, Denver, CC, 6/13" 18/93.
.^:.tPi™*cIr,The paper describes the results of the combustion of carbon black slurries.
(NCTE: The Hydrocarb process is being evaluated as a method of producing methanol
hydrogen-rich fuel gas, and carbon black.) Since carbon black has significant heating
value (33.78 million J/kg, 14,100 Btu/lb) and contains neither sulfur, nitrogen, nor
inorganic ash, there is potential for its use as a clean burning fuel or fuel extender
in boilers and industrial furnaces. To obtain a preliminary assessment of this poten-
tial, experiments were performed to examine the pumpability, atomization, and com-
bustion characteristics of slurries made of mixtures of carbon black with No. 2 fuel
oil and methanol.^Qarbon black/No. 2 fuel oil and carbon black/methanol slurries
with carbon black contents of up to 50 and 45 weight percent, respectively, were
pumped and atomized by means of a peristaltic pump and air atomizing scheme and
burned in an 82 kW (280,000 Btu/hr) laboratory combustor. Measurements of slurry
spray droplet size distributions indicated mean droplet diameters of about 100 and 30
micrometers for the carbon black/No. 2 fuel oil and carbon black/methanol mix-
tures, respectively. Particulate emissions from the combustion of slurries contai-
ning 47 weight percent carbon black in No. 2 fuel oil and 42 weight percent carbon
black in methanol were about 40 and 28 mg/ds cu m, respectively.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSAT1 Field/Group
Pollution Carbinols
Carbon. Black Combustion
Slurries Fuel Oil
Coal
Biomass
Wastes
Pollution Control
Stationary Sources
Hydrocarb Process
Municipal Waste
Methanol
13B 07C
11G 2 IB
21D
06C, 08A
14 G
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
19
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form "
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