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Improvement of Oxy-FBC Using Oxygen Carriers: Concept and Combustion Performance Robin W Hughes, Dennis Y. Lu, and Robert T Symonds Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b01556 • Publication Date (Web): 21 Aug 2017 Downloaded from http://pubs.acs.org on August 22, 2017
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Energy & Fuels
Improvement of Oxy-FBC Using Oxygen Carriers: Concept and Combustion Performance
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Robin W. Hughes, Dennis Y. Lu*, Robert T. Symonds,
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Natural Resources Canada, CanmetENERGY, 1 Haanel Drive, Ottawa, Ontario K1A 1M1,
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Canada
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*Corresponding author. Tel.: +1 (613) 996-2760
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E-mail address:
[email protected] 11
Abstract
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Fluidized bed combustors generally exhibit good mixing characteristics, but there can be
13
localized regions where there is insufficient oxygen to fully combust the fuel. Through
14
incorporation of an oxygen carrier into a high pressure, pulverized fuel based oxy-fluidized bed
15
combustor it should be possible to reduce or eliminate regions with insufficient oxygen present to
16
complete combustion. In this paper we investigate the use of a Canadian ilmenite ore based
17
oxygen carrier to enhance combustion performance and sulphur capture for atmospheric and
18
pressurized oxy-FBC systems. The paper includes a description of potential pressurized system
19
configurations with a discussion of related benefits and potential challenges.
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CanmetENERGY’s 50 kWth pilot scale atmospheric pressure oxy-fluidized bed combustor
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(oxy-FBC) was used to demonstrate the concept of oxygen carrier assisted combustion using two
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Canadian coals with under bed fuel and sorbent injection. The CO emissions were significantly 1
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reduced by replacing the inert bed material with the oxygen carrier (ilmenite ore); with CO
2
concentrations in the flue gas reduced up to 30 vol% and 13 vol% when burning Highvale coal
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and Poplar River coal, respectively. The improvement in combustion was even more pronounced
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in the bed region, in particular, under conditions of low excess oxygen and / or low bed
5
temperature. Analysis of solid samples (XRD) and flue gas condensates (acidity) have provided
6
further evidence of the oxygen carrier improving combustion performance and reducing the risk
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of bed agglomeration.
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Keywords: Keywords: Oxy-fuel combustion, PFBC, ilmenite ore, combustion performance, emissions, CO2 capture
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Energy & Fuels
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Introduction
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Increase in CO2 emissions in recent decades due to human activities, such as the combustion
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of fossil fuels, is believed to be the main contributor to climate change [1]. Immediate measures
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are needed to reduce CO2 emissions to the atmosphere. Carbon capture and storage (CCS) has
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been proposed as a major climate change mitigation technology that can reduce CO2 emissions
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from fossil fuel-fired facilities [2]. CCS processes consist of three stages: CO2 capture,
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transportation, and storage. The first stage is the most challenging due to the high cost of
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currently available technolgies.
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Oxy-fuel combustion is a technology class for capturing CO2 from large-scale fossil fuel-fired
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facilities with the potential to reduce CO2 emissions and meet CCS requirements [3]. Earlier
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techno-economic assessments indicated that oxy-fuel combustion is the most energy and cost
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efficient of the carbon capture technologies [4]. In oxy-fuel combustion, the fuel is combusted in
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an O2/CO2 atmosphere producing a CO2-rich flue gas with impurities such as SOx, NOx, Hg and
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H2O. When the combustion proceeds in a fluidized bed system, such as oxy-FBC (fluidized bed
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combustion), inherent advantages can be realized, e.g. fuel flexibility, moderate combustion
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temperature, and low impurity generation [5-6]. Furthermore, the fluidized bed configuration
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enables in-situ SO2 capture via sulphur removing sorbents, such as limestone or dolomite [7-9].
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This results in reduced corrosion risk to system components caused by acid attack after the
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formation of SO3 at high partial pressures of SO2 and steam [10-11]. CIUDEN's 30 MWth CFB
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boiler, supplied by Foster Wheeler and located at the Technology Development Centre for CCS in
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Spain, is the first of its kind for executing test runs at large pilot scale under oxy-combustion
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conditions. This plant demonstrated that CFB technology is suitable for oxy-combustion due to
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its operating flexibility and allows in-situ injection of calcium-based sorbents for efficient SO2 3
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capture [12].
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Although success has been achieved from a technical perspective with oxy-FBC units
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operating at atmospheric pressure, the high capital cost associated with them has thus far
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restricted the commercial success of the technology. This has motivated the development of
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pressurized technologies with net efficiencies 15 to 25% higher than their atmospheric pressure
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counterparts, which is expected to meet or exceed 20% cost reduction targets [13]. Oxy-fired
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pressurized fluidized bed combustion (oxy-PFBC) is a technology currently under development
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with the purpose of combusting fuel to generate heat, for use in applications such as steam and
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power production, while producing a pure stream of carbon dioxide that can be geologically
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sequestered thereby avoiding the emission of greenhouse gases and other pollutants [13-14].
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When combined with a supercritical CO2 Brayton cycle and an advanced CO2 processing unit,
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the technology is expected to produce power at an attractive cost of 82 $USD/MWh with 98%
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CO2 capture, which is highly competitive with other advanced power generation technologies
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with carbon capture and storage [15-16].
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Several studies have focused on improving fluidized bed combustion processes using reactive
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bed materials. These improvements include reduced emission of unburned hydrocarbons,
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enhanced sulphur capture, improved NOX reduction, increased agglomeration resistance, and
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reduced corrosion issues. Thunman et al. [17] found that by introducing ilmenite (Fe-Ti based
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oxygen carrier) to a 12 MWth circulating fluidized bed (CFB) boiler for biomass combustion, the
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concentrations of CO, NO, and hydrocarbon were reduced significantly. This was attributed to
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enhanced oxygen distribution throughout the bed via intermittent reduction and oxidation of
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ilmenite causing variations in oxygen partial pressures in different regions of the combustor. A
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later study by Corcoran et al. [18] noted that the structure of ilmenite particles injected into a 4
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CFB boiler for biomass combustion experienced structural and chemical changes due to the
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diffusion of potassium from the ash into the core of the ilmenite particles. This was found to
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improve the bed material agglomeration resistance and reduce corrosion issues. The introduction
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of an iron-based oxygen carrier into a bubbling fluidized bed for CH4 combustion with air has
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also been shown to accelerate the combustion of CH4, CO and H2 [19].
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In this paper, we investigate oxygen carrier assisted combustion for atmospheric and
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pressurized FBC systems, including a description of potential system configurations including
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benefits and potential challenges. Results and discussion of pilot-scale oxygen carrier assisted
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oxy-fluidized bed combustion tests performed with under bed fuel and sorbent injection are
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presented.
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Oxygen Carrier Assisted Oxy-PFBC Process Description
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A potential configuration of an oxy-PFBC system incorporating oxygen carrier assisted
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combustion is depicted in Figure 1, with the legend describing the components in Table 1. A
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summary of candidate reactants and their preferred characteristics are provided in Table 2. The
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system is a potential enhancement to the oxy-PFBC technology under development by the Gas
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Technology Institute (GTI), Natural Resources Canada - CanmetENERGY, Linde and other
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collaborators modified to incorporate oxygen carrier assisted combustion [13].
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The fuel and the sulphur removal sorbent are pressurized and injected into the combustor
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using a motive gas that pneumatically conveys them through one or more injectors depending on
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the firing rate of the combustor. The motive gas will typically be purified carbon dioxide that is
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generated within the associated CO2 processing unit.
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F IGURE 1. O XYGEN CARRIER ASSISTED OXY-PFBC PROCESS FLOW DIAGRAM
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T ABLE 1. LEGEND FOR OXYGEN CARRIER ASSISTED OXY-PFBC PROCESS FLOW DIAGRAM.
Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Description Fuel hopper Sorbent hopper Fuel and sorbent conveying gas Fuel and sorbent injectors Primary oxygen supply Recycled flue gas from recycled flue gas blower Distributor Fluidized bed containing oxygen carrier and potentially inert bed material In bed heat exchanger – transfer heat to heat transfer medium for example water, steam, supercritical CO2, process fluid, air, glycol mixture In bed oxidant injectors Inert bed material hopper Oxygen carrier hopper Inert bed material and oxygen carrier blender Inert bed material and oxygen carrier injection hopper 6
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Freeboard Freeboard convective heat exchanger PFBC pressure vessel Bed solids removal Conventional particulate separation device(s) – for example cyclone, impaction separator, filter, bag filters Fly ash removal and pressure let-down Flue gas cooler – direct (for example a water spray) or in-direct cooling (for example a heat exchanger) Flue gas condensate removal vessel – may be combined with 21 or separate Flue gas condensate to processing CO2 processing unit CO2 product Removed impurities stream – gas, liquid or solid streams are possible depending on the technology employed Recycled flue gas to recycled flue gas blower Recycled flue gas blower
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T ABLE 2. OXYGEN CARRIER ASSISTED OXY-PFBC REACTANTS AND PREFERRED CHARACTERISTICS.
Reactant Type Fuel
Sulphur removal sorbent Inert bed material Oxygen carrier
Candidate materials examples Pulverized – fine material Coal, petroleum coke, biomass, waste products, gaseous hydrocarbons Pulverized – fine material Limestone, lime, calcium hydroxide, dolomite (calcium and magnesium bearing rock) Crushed – coarse material Sand, ash, olivine Crushed – coarse material Natural and synthetic materials Ilmenite (iron-titanium ore), synthetic materials composed of Ni, Cu, Mg, Fe, Mn, on alumina, silica, etc. It is preferred that the oxygen carrier: • Heat of reaction is endothermic when it is reduced. • Is attrition resistant. • Resistant to poisoning by the fuel constituents including ash and sulphur species.
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High pressure oxygen (O2) is combined with recycled flue gas, which is primarily composed 7
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of carbon dioxide (CO2) and water vapour (H2O). Mixing of the O2 with recycled flue gas is done
2
to avoid localized hot spots within the combustor; injection of pure oxygen without moderating
3
gas could result in temperatures above the melting point of the fluidized bed materials and
4
process equipment, which would cause process failure. The mixture of oxygen and recycled flue
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gas passes through a distributor at the bottom of the fluidized bed.
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The fuel and oxygen mix within the fluidized bed resulting in fuel combustion with an
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associated release of heat. In general, the products of the complete combustion of the fuels are
8
carbon dioxide (CO2), water/steam (H2O), sulphur dioxide (SO2), sulphur trioxide (SO3), nitrogen
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dioxide (NO2), nitrogen monoxide (NO), and nitrous oxide (N2O).
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When combined with water in the presence of oxygen, sulphur species can form sulphuric acid
11
(H2SO4). It is desirable to remove the sulphur species within the combustor to avoid corrosion of
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the components via acid attack [20]. This can, in part, be done via sulphur removal sorbent [21].
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Calcium bearing materials are used which react with the sulphur species in the presence of
14
oxygen to form calcium sulphate (CaSO4), with the fraction of time that the sorbent particle is
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under oxidizing versus reducing conditions affecting the rate of conversion [11, 22]. In this
16
configuration, the sulphur removal sorbent is pulverized to enhance the rate of reaction which
17
will tend to maintain local sulphur species concentrations at low levels, thereby avoiding
18
localized corrosion. Since the sulphur removal sorbent is fine it will be continuously blown into
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the freeboard and consequently blown out of the combustor [23]. Many of the fuels used in oxy-
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PFBC technology will contain ash; this ash will be very fine, since the fuel was pulverized, and
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will normally be blown into the freeboard and out of the combustor with the sulphur sorbent.
22
In localized regions where fuel-oxidant mixing is relatively poor, for example at fuel injectors, 8
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there may be insufficient oxygen to fully combust the fuel [24-25]. The products of incomplete
2
combustion include the products of complete combustion mentioned above as well as a variety of
3
reduced species including hydrocarbons (HCs), carbon monoxide (CO), hydrogen sulphide
4
(H2S), and ammonia (NH3). These species are not desirable in the flue gas of a combustor since,
5
if in sufficient quantity, they can later mix with oxygen resulting in explosions within the
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downstream equipment [26]. The metal alloys used in components in the combustor typically
7
have a protective oxide layer that prevents corrosion, however, these species can reduce the metal
8
oxide layer, thereby increasing corrosion rates of components [27]. Corrosion of these
9
components can result in increased erosion rates and component failure [28]. Incomplete
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combustion reduces the amount of heat that can be recovered from the combustor since a portion
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of the fuel has not been burnt and, therefore, the overall efficiency of the system is reduced.
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Several reduced species, i.e. not fully oxidized species, can decrease the effectiveness of the CO2
13
processing unit in the removal of impurities required to meet pipeline specifications [29].
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Typically, to limit or avoid localized regions with insufficient oxygen, large-scale combustors
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incorporate a multitude of fuel and oxidant injection points such as the Tidd facility that had 64
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fuel injection points [30]. As the number of injection points increases the cost and complexity of
17
the combustion system is also increased, negatively affecting cost of construction, cost of
18
operation, and reliability. Therefore, there is a trade-off in technical and economic performance of
19
the system based on the ability of the system to transfer sufficient oxygen to complete
20
combustion throughout the combustion region.
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F IGURE 2. ILLUSTRATION OF IN- BED REGIME PROPOSED FOR OXY -PFBC
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The in-bed portion of a pressurized fluidized bed combustion system is depicted in Figure 2.
4
Following the flow of fluidizing gas from the bottom to the top of the combustor, several regions
5
are identified (A through D). In region A, the oxygen and recycled flue gas are heated through
6
contact with the bed material. The bed material in this region that is in a reduced state will react
7
with the molecular oxygen to form a metal oxide with a higher oxidation state. For a generic
8
mono-metallic oxygen carrier the oxidation reaction proceeds according to [31]: 1/2 →
9 10
Eq 1
With Me representing a metal atom. This exothermic reaction will aid in rapidly heating the gas to the desired temperature.
11
In region B, fuel and sulphur sorbent are injected into the bed using a motive gas. Typically, a
12
jet will be formed in which the fraction of bed material is lower than in other portions of the bed
13
on a per unit volume basis [32]. In this region fuels will pass through a series of stages including
14
drying, pyrolysis, and finally char oxidation [33]. These stages will overlap in various locations 10
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within region B. In the drying stage moisture that is present in the fuel will be evolved. In the
2
pyrolysis stage species including H2, CO, CO2, H2O, H2S, CH4 and higher hydrocarbons will be
3
evolved from the fuel particle or droplet. If these species reach region C before being oxidized,
4
then they may remove the protective oxide layer on the heat exchanger tubes located in region C
5
resulting in corrosion and subsequently erosion. The oxygen carrier will be present on the
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periphery of, and to some extent within, region B where it will oxidize these species. For a
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gaseous hydrocarbon fuel, CnHm, such as is present in pyrolysis products, reduction of the oxygen
8
carrier will proceed via [31]: 2 → 2
9
Eq 2
For carbon monoxide, reduction of the oxygen carrier will proceed via: →
Eq 3
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With similar analogues for hydrogen and other combustible gases including sulphur containing
11
compounds. Due to the endothermic nature of these reactions for many oxygen carriers, peak
12
fuel temperatures will be reduced resulting in a decreased risk of liquid ash formation and hence
13
bed agglomeration [34]. Bed agglomeration can lead to serious process upsets and damage to the
14
combustion system. It should be noted that multiple fuel injectors may be present at a given
15
elevation and fuel injectors may be present at multiple elevations. When considering Ca-based
16
sorbents for sulphur capture in oxidizing environments at the high partial pressures of CO2
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present in the combustor, sulphation will proceed through direct sulphation via [35]: 1 → 2
18
Eq 4
The rate of this reaction is dependant on SO2 concentration, but it is only dependant on oxygen 11
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concentration when oxygen partial pressure is quite low [36].
2
incorporation of an oxygen carrier in the combustor maintains the oxygen partial pressure at a
3
relatively higher level throughout the dense bed region than occurs with an inert bed material
4
then we can expect that the rate of sulphation will increase and sulphur capture will improve.
5
CaSO4 and CaS have been shown to not be thermodynamically stable under certain reducing
6
conditions that can occur in the dense phase of fluidized bed combustors. The effect of reducing
7
conditions on decomposition and stability of CaSO4 along with the influence this has on sulphur
8
capture in air-fired fluidized bed combustors are explained by Lyngfelt & Leckner [37]. Figure
9
3 provides a phase diagram for the system O2, SO2, H2O, CaS, CaCO3 and CaSO4 with the partial
10
pressure of H2O set to 0.1 bar and the partial pressure of CO2 set to 0.85 bar that has been
11
generated in FACTSage software. The H2O and CO2 partial pressures have been set in this phase
12
diagram to represent a potential CO2 concentration in an oxy-fluidized bed combustor operating
13
at atmospheric pressure. Lyngfelt and Leckner provided a similar phase diagram for conditions
14
where indirect sulphation is expected i.e. at relatively low CO2 partial pressures. The phase
15
boundaries are in nearly identical locations for high and low CO2 partial pressures despite the fact
16
that in one case CaCO3 is present, while in the other CaO is present. We should point out that in
17
reproducing the equivalent chart provided by Lyngfelt & Leckner we have identified a
18
discrepancy in the region with partial pressure of oxygen less than 10-15 and SO2 concentration
19
less than 100 ppm that we are not able to explain. If the oxygen carrier tends to maintain the
20
oxygen partial pressure at levels above the phase boundary between CaCO3 and CaSO4 then we
21
can expect improved sulphur capture.
If we presume that the
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F IGURE 3. PHASE DIAGRAM FOR THE SYSTEM O 2, SO 2, H 2O, C AS, C ACO 3 AND C ASO 4: PRESSURE IS IN BAR,
3
PARTIAL PRESSURE OF CO 2 HAS BEEN SET TO 0.85 BAR AND PARTIAL PRESSURE OF H 2O HAS BEEN SET TO 0.1 BAR.
4
In region C, the heat exchanger tubes are immersed in oxidized oxygen carrier, which will
5
oxidize reduced species in the region. The oxygen and inert bed material transfer heat to the heat
6
exchange tubes in this region. This region is characterized by typically good gas/solids
7
contacting; however, the contacting of regions with varying gas composition can be poor and
8
plumes of unconverted gaseous fuels can persist [38-40]. The likelihood of a plume of reduced
9
gas passing through this region without being oxidized is reduced when oxygen is available via
10
the solid oxygen carrier. It should be noted that multiple heat exchange tube banks may be
11
present in the combustor.
12
In region D, we depict an optional secondary oxygen injector. Secondary oxygen injection 13
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may be incorporated to enhance oxygen distribution throughout the fluidized bed. This may be
2
necessary to avoid excessively high oxygen partial pressures in region A, which will result in
3
high local temperatures adjacent to region B [41]. The oxygen carrier may be oxidized in region
4
D releasing heat. It should be noted that multiple oxidant injectors may be present at a given
5
elevation and oxidant injectors may be present at multiple elevations within this region.
6
Over time the oxygen carrier will attrite and form finer material that is blown out of the
7
fluidized bed [42] and may continue to oxidize combustible species in the freeboard. It is
8
expected that the rate of attrition of the oxygen carrier may be greater than inert bed material, so
9
it may be beneficial and sufficient for only a portion of the fluidized bed material to be composed
10
of oxygen carrier, while the remainder could be inert bed material [17-18, 43]. An important
11
aspect of this technology is the requirement to maintain fluidizing gas superficial velocity below
12
approximately 1.5 m/s to limit impact force of the oxygen carrier particles on each other and on
13
system components; thereby, limiting the rate of attrition [44]. This can be achieved in a high
14
throughput unit through pressurization of the combustor [45].
15
An important differentiation between this technology and oxygen carrier assisted combustion
16
in the literature is the elevated pressure of operation. At atmospheric pressure, the rates of
17
reaction (reduction and possibly oxidation) of many oxygen carriers that are resistant to
18
poisoning by fuel ash components and are non-toxic are relatively low [46]. The rates of reaction
19
are a function of partial pressure of the reactants, so at elevated pressure reaction rates are
20
increased [47-51]. Figure 4 provides an indication of the relative rates of reaction of an ilmenite
21
ore at various pressures [51].
14
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F IGURE 4. E FFECT OF PARTIAL PRESSURE ON REDUCTION OF ILMENITE AT ELEVATED PRESSURES, ( A): CH 4 PARTIAL
3
PRESSURE , AND ( B): CO PARTIAL PRESSURE .
4
At elevated pressure the size of bubbles in fluidized beds can be reduced, which will result in
5
reduced mass transfer resistance and hence improved contacting of oxidizing and reducing gas
6
species with the oxygen carrier [49]. A third benefit of pressurization on the fluidized bed is the
7
depth of penetration of fuel and oxidant jets into the fluidized bed increasing the distribution of
8
reactants across the combustor. For a horizontal jet, the equation by Merry [50] provides an
9
indication of the increase in jet penetration with pressure through the change in the fluid density
10
term, ρf: *.
# $ 4.5 ! 5.25 " ) %& #' ( '
*.
#+ " ) #'
' *. ,
Eq 5
11
This equation provides relationships required for the practical development of this technology,
12
since it provides an estimate of the length of the regions B and D based on system geometry and
13
process conditions. While this equation provides jet length for horizontal jets, there are similar
14
equations for inclined and vertical jets which are also possible orientations for jets entering
15
regions B and D [32]. With the operating conditions considered in this study the equation 15
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provides a jet length of less than zero, so it is expected that the jet length is negligible. However,
2
based on potential conditions in an oxy-PFBC system the jet length is predicted to be on the order
3
of a meter in length.
4
Referring again to Figure 1, the flue gases and fine particulate material flow upwards from the
5
fluidized bed into the freeboard region which contains a convective heat exchanger for extracting
6
heat from the flue gas and solids prior to a particulate removal device. Following the particulate
7
removal device is a heat exchanger which may be combined or separate from a condensate
8
removal vessel. The flue gas then passes through a CO2 processing unit where impurities and
9
water are separated from CO2 prior to compression and transport of the CO2 via pipeline. A
10
portion of the CO2 is recycled to the combustor via a recycle gas blower originating from before
11
the condensate removal vessel or from within the CO2 processing unit.
12
Through elimination of reducing zones in the combustor it may be possible to reduce the
13
number of fuel and/or oxidant injectors. This would reduce the cost and complexity of the
14
combustor, and create the possibility of operating with lower excess oxygen. Typically,
15
combustion systems inject more oxygen than is required for complete combustion to reduce the
16
presence of regions where reducing conditions prevail or at least to minimize the emissions of
17
reduced species. In air blown combustors an improvement in performance could occur due to
18
reduced parasitic electric losses related to reduced air blower power requirements. However, in
19
oxy-fired units designed for carbon capture and storage reducing the excess oxygen requirement
20
is more important. Typically, the oxygen is produced using a cryogenic air separation unit (ASU)
21
which has both a large power requirement and high capital cost [51-52]. Reducing excess
22
oxygen decreases the consumption of oxygen that is unnecessary to complete combustion.
23
Furthermore, the oxygen content of the CO2 product must be in the low ppm range to meet 16
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Energy & Fuels
1
pipeline specifications [29].
2
processes, both of which add to process cost and depending on technique may increase
3
greenhouse gas emissions [53]. Operation with reduced excess oxygen can reduce the cost and
4
emissions associated with oxygen removal from the CO2 product.
This can be achieved through catalytic deoxidation or distillation
5
A risk that is inherent in combustion technologies is the potential for interruptions in oxidant
6
supply or sudden increases in fuel flow to generate brief periods when there is insufficient
7
oxygen available to complete combustion. If this happens then there may be periods when there
8
is a sufficient fraction of reducing gas species in the flue gas to generate an explosive atmosphere
9
in downstream equipment, which if it detonates, could result in catastrophic damage to the
10
system [54]. It should be recognized that the presence of oxidized oxygen carrier in the fluidized
11
bed provides a buffer of oxygen supply within the fluid bed which can reduce the risk associated
12
with interruptions in gaseous oxygen supply or sudden increases in fuel flow. The extent of this
13
buffer is dependent on the oxygen carrying capacity of the carrier.
14
3
15
3.1 Materials
Experimental
16
Two types of pulverized coal were used, namely Highvale and Poplar River. Highvale is a
17
sub-bituminous coal from Alberta, Canada that is fired in the Keephills and Sundance generating
18
stations, while Poplar River is a lignite coal from Saskatchewan, Canada that is currently fired in
19
the Poplar River generating station. The fuel proximate analyses (ASTM D7582, ISO 562),
20
ultimate analyses (ASTM D5373, ASTM D4239), fusibility properties (ASTM D1857), and
21
calorific values (ISO 1928) are provided in Table 3, while the major and minor oxide analyses
22
(ASTM D4326) are provided in Table 4. 17
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1
The oxygen carrier used in this work is UKTO ilmenite ore, a beneficiated massive rock
2
produced from raw ilmenite ore after removing most of its gangue material by gravity separation.
3
The upgraded rock ilmenite was roasted under oxidizing atmosphere at 900-1000°C to remove all
4
sulphides and sulphosalts. The ilmenite ore was supplied by Rio Tinto Iron & Titanium, Québec,
5
Canada. The material was crushed and sieved to a particle size of 425-869 µm. The chemical
6
composition of the ore measured by X-ray fluorescence (XRF) analysis (ASTM D4326) can be
7
found in Table 4. The phases present in the ilmenite ore were measured by X-ray diffraction
8
(XRD) and the compounds are provided in Table 5. A sand (99.8 wt-% in SiO2), which was used
9
as a reference bed material, was sieved to a particle size of 600-1040 µm. For SO2 capture, a
10
pulverized local limestone (KK Karson) was used. The composition of the limestone was
11
measured by XRF and is provided in Table 4.
12
T ABLE 3. P ROXIMATE, ULTIMATE, FUSIBILITY PROPERTIES, AND HEATING VALUE OF THE TEST
13
FUELS ON AN AS TESTED BASIS .
Proximate Moisture TGA Ash Volatile Fixed Carbon Ultimate, db Carbon Hydrogen Nitrogen Total Sulfur Oxygen by Difference Gross calorific value (HHV) Fusibility, Oxidizing Initial Spherical Hemispherical Fluid Fusibility, Reducing Initial Spherical
Highvale
Poplar River
wt% wt% wt% wt%
4.25 23.14 29.32 43.29
4.20 16.64 38.20 40.96
wt% wt% wt% wt% wt%
53.0 3.27 0.76 0.32 15.26
54.9 3.42 0.77 1.03 19.01
MJ/kg
20.39
21.34
°C °C °C °C
1321 1341 1343 1368
1235 1249 1254 1302
°C °C
1252 1349
1171 1199 18
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Energy & Fuels
Hemispherical °C Fluid °C
1357 1413
1252 1313
1 2
T ABLE 4. MAJOR AND MINOR OXIDES ANALYSES OF THE TEST FUELS, LIMESTONE AND ILMENITE ON AN
3
AS TESTED BASIS.
SiO2 Al2O3 Fe2O3 TiO2 P2O5 CaO MgO SO3 Na2O K2O Barium Strontium Vanadium Nickel Manganese Chromium Copper Zinc Loss on Fusion Total
wt% wt% wt% wt% wt% wt% wt% wt% wt% wt% wppm wppm wppm wppm wppm wppm wppm wppm wt% wt%
Poplar River 33.40 20.41 6.87 0.71 0.06 18.95 5.48 11.98
