J. O. L. Wendt

University of Utah | UOU · Department of Chemical Engineering

The objective of this study was to understand the synergistic effect of sulfur dioxide (SO2) emission reduction during the combustion of biomass-coal blends in comparison to pure coal by recording the gaseous SO2 concentrations, analyzing the composition of combustion ash by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), an...

Torrefied wood originating from beetle-killed trees is an abundant biomass fuel that can be co-fired with coal for power generation. In this work, pulverized torrefied wood, a bituminous coal (Sufco coal) and their blended fuel with a mixing ratio of 50/50 wt.%, are burned in a 100-kW rated laboratory combustor under similar conditions. Ash aerosol...

A combustion model, originally developed to simulate the destruction of chemical warfare agents, was modified to include C1-C3 fluorinated organic reactions and kinetics compiled by the National Institute of Standards and Technology (NIST). A simplified plug flow reactor version of this model was used to predict the destruction efficiency (DE) and...

Wildfires in the western United States destroy human settlements, properties, and wildlife and cause uncontrolled release of carbon dioxide every year. A major contributing factor to theses wildfires are bark beetle-killed standing trees. These dead trees can be utilized as co-combusting fuel in coal-fired utility boilers, thus reducing the chance...

Recent measurements in scenarios representative of second generation atmospheric pressure oxy-coal combustion systems have shown a significant increase in ash deposition rates in comparison to combustion in air. However, the causative mechanisms behind this increase have not been well understood. To fill this void, well-characterized experiments in...

This work details a model for evaluating the relative ash deposition propensity of various solid fuels without the complicated spatial considerations included in CFD modeling. Four deposition mechanisms are included, namely: inertial impaction, thermophoresis, condensation, and eddy impaction. This model has been validated and shown to effectively...

Arsenic is a harmful trace element and its behavior under several combustion conditions is of interest. Though the mechanisms regarding arsenic capture and transformation in combustion systems are well known, it is still worth investigating the dominant factors for particular fuels and combustion conditions. Considering the widely application of bi...

Due to the urgent needs to reduce anthropogenic carbon dioxide emissions there is an increasing interest in the use of alternative fuels. For this reason, there is a need for new knowledge on how to design and adapt existing heat and power plants to biogenic and waste-derived fuels. This work relates to co-firing of biomass and coal and the sulfati...

The focus of this paper is on effects of chlorine and sulfur on coal ash deposition rates, under practically relevant but systematically controlled combustion conditions. This problem is important, not so much for coal, but to understand and predict deposition rates for biomass combustion where chlorine contents can be high. To this end, ash deposi...

Biomass and waste derived fuels contain large amounts of sodium, potassium, and chlorine that form NaCl and KCl, that is, compounds that cause operational problems, such as slagging, fouling, and high-temperature corrosion. Therefore, alkali chlorides are the main reasons that explain why steam parameters are less advanced and efficient in biomass...

This paper is concerned with the effect of pressure on the particle size distribution and the size-segregated composition of the sub-micron ash aerosol created during oxy-coal combustion under near practical self-sustaining combustion conditions. The problem is important because pressurized oxy-coal combustion has been proposed as one promising tec...

The future use of coal as a fuel for power generation in the US depends on the availability of financially viable technologies for capture and storage of CO2 emissions from power plants. Key second-generation candidates for CO2 capture include high temperature and pressurized oxy-firing of coal, which has the potential to increase efficiency, lower...

A temperature-controlled ash deposition probe was applied to collect temporally resolved deposit samples in a 100kW rated down-fired pilot scale combustor under two atmospheres: 1) air condition, 2) with 70% O2 as inlet gas (named as OXY70). The mineral compositions, particle size distributions (PSDs) as well as the partitioning of arsenic in the i...

Managing the risk of ash deposition is still a priority for oxy-fuel combustion of biomass-coal blends. This is especially a concern when high inlet O2 concentrations are adopted to reduce the amount of recycled flue gas, which results in higher combustion temperatures and lower gas flow rates. Such changes are expected to affect ash formation and...

This paper is concerned with the formation of ash aerosols and their subsequent deposition on a heat transfer surface during the combustion of petroleum coke. The subject is of interest for two reasons: first, petroleum coke is a good alternate fuel for power plants, and fouling has been identified as a challenging problem, especially under fuel ri...

Pressurized oxy-fuel combustion in fluidized bed is one of advanced clean coal technologies. CoMPared with conventional air combustion in atmospheric pressure, it not only can improve the overall plant efficiency, but also can reduce the cost of CO2 capture. However, there is no available studies on the particulate matters formation during pressuri...

Utilization of biomass when combined with carbon capture and sequestration (CCS) is one feasible solution for ‘Bio-energy with carbon capture and storage’ (BECCS), which can reduce the CO2 emissions in the atmosphere. Rice husk is a unique biomass resource because its ash content is typically higher than 15% and more than 88% of these mineral matte...

Ultrafine ash particles play an important role in establishing a sticky inner deposit layer on heat transfer surface for power plants, but it is still unclear whether a thin surface alkali coating on these ultrafine particles might control this deposition behavior. In this research we used a high resolution FE-TEM/STEM equipped with twin SDD EDX de...

This paper presents a synthesis of a large body of experimental data on growth rates of ash deposits from the air- and oxy-combustion of multiple pulverized solid fuels, including coal, biomass and their blends. The experimental data were obtained from 35 tests in a 100kW (rated) entrained-flow combustor that allowed self-sustained combustion of so...

Pulverized rice husks are co-fired with natural gas in a 100 kW (rated) down-fired oxy-fuel combustor (OFC) under two conditions: 1) air combustion (denoted as Air); 2) oxy-combustion with 70% O2 and 30% CO2 in the inlet oxidant gas (denoted as OXY70). Studied in this paper are: 1) mechanisms governing the partitioning of inorganic matter within th...

A 100kW rated down-fired pilot scale combustor was used to explore sub-micron coal ash aerosol formation for two coals under various air and oxy-combustion atmospheres. Particle size distribution (PSD) data were obtained through isokinetic sampling and then by electron mobility and light scattering particle sizing. The submicron portion of the PSD...

The alkali content in the ash is commonly thought to be the “bad actor” in determining coal ash deposition rates on boiler heat transfer surfaces. This paper reports results of 16 tests in which ash aerosol deposition rates were measured for three coals, burned under air-fired and oxy-fired combustion conditions. A 100kW down-fired laboratory combu...

Pulverized bituminous coal was burned in a 10 W externally heated entrained flow furnace under air-combustion and three oxy-combustion inlet oxygen conditions (28, 32, and 36%). Experiments were designed to produce flames with practically relevant stoichiometric ratios (SR = 1.2–1.4) and constant residence times (2.3 s). Size-classified fly ash sam...

This paper is concerned with deposition rates of coal ash on a vertical surface in a 100 kW rated down-flow laboratory coal combustor. At that scale, flow in the post flame where deposition occurs, is laminar, and the deposits on a vertical surface are similar to the early, sticky, inner deposits on horizontal surfaces. Therefore the problem addres...

Deposition of ash on heat transfer surfaces is a major factor in determining boiler performance. Deposits so formed consist of tightly bound “inside” deposits close to the heat transfer surface and loosely bound “outer” deposits that are easily dislodged. This paper describes research focusing on both the composition of inner and outer deposits, an...

Many coal-fired power plants now burn coal blends instead of a single raw coal because of required low sulfur attainment levels. Mineral matter for the coal blends is likely to be different from that for their parent coals and is unlikely to be predictable from simple averaging rules. The problem is important because deposit buildup alters the char...

Ash aerosol and ash deposit formation during oxy-coal combustion were explored through experiments in a self-sustained 100 kW rated down-fired oxy-fuel combustor. Inlet oxidant conditions consisted of 50% inlet oxygen with CO2 (hereafter denoted as OXY50 conditions). A Berner low pressure impactor (BLPI), a scanning mobility particle sizer (SMPS),...

To improve cost competitiveness with conventional power plants, gasification plants need to improve plant economics, efficiency, and increase plant availability. The current syngas coolers used in Integrated Gasification Combined Cycle (IGCC) plants offer high efficiency, but their reliability is generally lower than other process equipment used in...

A 37 kW down fired pilot scale laboratory combustor, specially modified to allow recycle of both dirty and cleaned flue gas, was used to investigate aerosol formation under air- and oxy-coal combustion conditions. The focus was on emission of soot or black carbon, formation of fine and ultra-fine particulate matter, and partitioning and vaporizatio...

Prediction of ash deposition characteristics under oxy-firing conditions helps to determine how retrofit to oxy-combustion might affect boiler performance. To obtain data to help achieve this end, a novel temperature-controlled ash deposition probe was designed to collect temporally resolved deposit samples in a 100 kW rated down-flow test furnace...

Past research on flame stability and stand-off distance under oxy-coal combustion conditions has used a 100kW pulverized coal test rig with a co-axial turbulent diffusion burner, and has been described at previous Pittsburgh Coal Conferences. These studies were for one specific coal, namely a Utah Bituminous Coal. The purpose of the research descri...

Previous works on flame stability and stand-off distance under oxy-coal combustion conditions has been conducted with a co- A xial turbulent diffusion burner for different rank coals in a 100kW pulverized coal test rig at the University of Utah. The pilot-scale results indicate that oxygen partial pressure and coal compositions have a significant e...

Metal fuel borne catalysts (FBCs) can be used with diesel fuels to effectively reduce engine out particle mass emissions. Internationally, metal FBCs are used for both on-road and off-road applications, although current regulations in the U.S. restrict their on-road use. Although metal FBCs are intended to be used with specialized diesel particulat...

Oxy-coal combustion allows the concentration of oxygen in each burner stream to be controlled as an independent variable. Input concentrations of oxygen and the way it is injected can have significant impacts on the turbulent mixing and flame stability in coaxial turbulent jets. Whereas previous studies have quantified the effects on flame stabilit...

In this paper we report on our latest results based on double-side contacted p-type Si solar cells characterised by a dielectric passivated rear surface and local point contacts – our so-called Q.ANTUM technology. In addition to our confirmed 19.5% efficient world record multi-crystalline Si solar cell we present a new Q.ANTUM module with record en...

In this paper we present the latest R&D results of Q.Cells' high-efficiency solar cell and module concept Q.antum that is currently transferred into mass production. The current work is focused on solar cells and modules produced in our Reiner-Lemoine Research Center. Our optimized rear passivation concept in combination with innovations on the fro...

Crude glycerol is an abundant by-product of biodiesel production. As volumes of this potential waste grow, there is increasing interest in developing new value added uses. One possible use, as a boiler fuel for process heating, offers added advantages of energy integration and fossil fuel substitution. However, challenges to the use of crude glycer...

A new high-temperature, mineral non-carbon based dispersed sorbent derived from paper recycling products has been shown to capture mercury at high temperatures in excess of 600°C. The sorbent is consisted of kaolinite/calcite/lime mixtures. Experiments have been conducted on chemi-sorption of elemental mercury in air on a packed bed. The sorption o...

Oxy-fuel combustion is one of more promising technology for CO2 capture in a coal combustion power plant. For a newly designed oxycoal combustion power plant, using high O2 concentrations and lower recycling ratios will decrease the size of the power plant thereby reducing the capital cost as well as increasing the overall efficiency. Ash depositio...

Experiments were performed in University of Utah's 1.5MW and 100kW pulverized coal furnaces and a 300kW circulating fluidized bed to investigate the suitability of carbon traps for mercury measurement under high CO 2 environments produced by oxycombustion. The difference in mercury emission and speciation between air- and oxy-fired conditions was a...

A down-fired laboratory combustor, designed for 100kW, was used to determine effects of switching from air to oxy-firing on soot, unburned carbon and ultrafine particle emissions from practical pulverized coal flames. Of interest here were potential effects of substitution of the N2 in air by CO2 in practical, swirling, pulverized coal, turbulent d...

This paper is directed towards understanding how composition of the coal transport medium (primary CO2 and O2) affects the observed ignition stand-off distance in 40kW co-axial turbulent diffusion, oxy-coal flames, supported in a specially designed combustion test rig, rated at 100kW. First, a methodology to define and quantify the observed ignitio...

Line of Sight Soot Measurements in Staged and Unstaged Air and Oxy-Coal Flames Curtis Stimpson, Trevor Blanc, and Dale R. Tree Brigham Young University Will Morris and Yost Wend University of Utah Andrew Fry Reaction Engineering Incorporated Oxycombustion is a technology that has the potential to enable the capture of CO2 produced coa...

Ash deposition is still an unresolved problem when retrofitting existing air-fired coal power plants to oxy-fuel combustion. Experimental data are quite necessary for mechanism validation and model development. This work was designed to obtain laboratory combustor data on ash and deposits from oxy-coal combustion, and to explore the effects of oxy-...

The effects of oxy-coal combustion on the near-field aerodynamics of simple, co-axial turbulent diffusion flames have been investigated. Experiments were carried out in a specially designed 40kW (100kW nominally) combustion test rig. Results from two sets of experiments are presented, with each set using once-through CO2, without H2O, plus added O2...

The purpose of this study is to clarify the fundamental features of NO x formation in oxy-coal combustion. The pure effects of various factors related to oxygen concentration, flame temperature and flame shape on NO x formation are investigated by experimental and theoretical analysis, resulting in the following conclusions: (1) In oxy-coal combust...

In this paper we report on latest results from our pilot production of multi-crystalline (mc) p-type Si cells in the Reiner-Lemoine Research Center at Q-Cells. The cells are double-side contacted and feature a lowly doped emitter, a fineline-printed Ag grid in combination with plating as front metallization and a dielectric passivated rear with loc...

Crude glycerol is an abundant by-product of the transesterification process used for biodiesel production. Recently, there has been investigation into the viability of crude glycerol as a boiler fuel for process heating. The main challenges of glycerol combustion involve its low energy density, high viscosity, and high auto-ignition temperature. Pr...

In July 2008, the U.S. EPA proposed to regulate the underground injection of carbon dioxide (CO2) for the purpose of geologic sequestration (GS) under the Safe Drinking Water Act (SDWA). Elements of this proposed rule will build upon existing Underground Injection Control (UIC) regulations, with modifications to address the unique nature of CO2 inj...

This paper is directed towards understanding how composition of the coal transport medium (primary CO2 and O2) affects the ignition stand-off distance in 40kW co-axial turbulent diffusion, oxy-coal flames, supported in a specially designed combustion test rig, rated at 100kW. First, a methodology to define and quantify the ignition behavior of labo...

Oxyfuel combustion is an attractive option for coal-based power generation with CO2 capture. However, there are a number of engineering challenges that must be addressed before this technology can be successfully deployed. Ash deposition is one that has significant impacts on power plant design and operation but has not been well investigated under...

The behavior of Se during coal combustion is different from other trace metals because of the high degree of vaporization and high vapor pressures of the oxide (SeO) in coal flue gas. In a coal-fired boiler, these gaseous oxides are absorbed on the fly ash surface in the convective section by a chemical reaction. The composition of the fly ash (and...

The field of photovoltaic (silicon solar cells) is an important driver for regenerative energy techniques. The technology and efforts regarding efficiency factor, quality, and costs are still under development. Currently, typical silicon solar cells are connected to so called strings by two or three solder coated copper ribbons. The common intercon...

Although remarkable progress has been made in developing technologies for the clean and efficient utilization of coal, the biggest challenge in the utilization of coal is still the protection of the environment. Specifically, electric utilities face increasingly stringent restriction on the emissions of NO and SO, new mercury emission standards, an...

This paper is concerned with the sequestration of mercury, cadmium, lead, sodium and potentially other volatile and semi-volatile metals by high-temperature mineral, non-carbon based dispersed sorbents. The focus here is on kaolinite and lime powders (for Pb, Cd, and Na), and on intimate kaolinite/calcite/lime mixtures (for Hg), both of which under...

This work is concerned with sequestration of elemental Hg at high temperatures (900–1100 °C) on a sorbent that is mineral based, rather than carbon based. This sorbent consists of an intimate mixture of CaO, CaCO3, and Al2O3–2SiO2, and is manufactured in industrially relevant quantities (metric tons) from residues produced in paper recycling proces...

The behavior of selenium in coal-fired power plants is relevant to air emissions of this hazardous air pollutant and to release of selenium in wastewater. A fundamental, predictive model for selenium interactions with fly ash was developed and validated against pilot-scale combustion data. The selenium distributions in fly ash in pilot-scale combus...

In order to investigate sorption properties of sorbents, packed bed experiments were conducted. The focus here is on chemi-sorption of elemental mercury in air on a packed bed, consisting of kaolinite/calcite/lime mixtures, hereafter referred to as MinPlus, which is the name under which it is marketed. Sorption occurs at temperatures between 600°C...

The hypothesis that health effects associated with coal combustion fly-ash particles are exacerbated by the simultaneous presence of iron and soot was tested through two sets of experiments. The first set created prototype particles from complete and partial combustion, or oxygen free pyrolysis of a high iron Illinois bituminous coal in an external...

The purpose of this research is to better understand and to scale the effect of partial pressures of O2 and CO2, two additional degrees of freedom for oxy-coal combustion, on coal jet ignition and flame stability in the near burner zone. A novel methodology is developed to quantify the flame stability and flame length by introducing an image proces...

Non-equilibrium effects resulting from the slow relaxation of inertial particles to statistical equilibrium with flow fluctuations in turbulence are known to have important consequences, but they are not readily incorporated into models. Here, a simple analysis of these effects predicts −2/3 power-law dependence of the particle deposition rate on S...

The purpose of this research is to understand and predict the effects of the near burner zone environment on ignition characteristics of a turbulent axial pulverized coal jet. In oxy-coal combustion this environment consists of O2 and CO2 (instead of N2). Ultimately it is planned to provide data for subsequent simulation validation studies that can...

A bench scale disperse phase, entrained-flow reactor, was employed to investigate elemental mercury (Hg) adsorption on non-carbon based sorbents. The major parameters varied for the Hg adsorption test were reaction temperature, sorbent feeding rate, gas compositions, and mineral composition of sorbents. The sorbent receiving the greatest attention...

Diesel exhaust and especially diesel exhaust particles (DEP) are a health concern because of their complex chemistry, small size, and ubiquitous presence in urban environments. As part of a research program designed to relate diesel exhaust properties to adverse health effects, a series of inhalation exposure studies were conducted to investigate t...

The combustion of coal liberates arsenic, selenium, cadmium, and cesium into the environment. These toxic metals, which are discharged with the flue gas or collected with fly ash, may vaporize in the hot portions of the combustor then return to the solid phase in cooler zones of the process downstream. Understanding the mechanisms by which toxic me...

Gas-phase reactions between elemental mercury and chlorine are a possible pathway to producing oxidized mercury species such as mercuric chloride in combustion systems. This study examines the effect of the chemistry of a commonly used sample conditioning system on apparent and actual levels of mercury oxidation in a methane-fired, 0.3 kW, quartz-l...

Ultrafine coal fly-ash particles, defined here as those with diameters less than 0.5 μm, typically comprise less than 1% of the total fly-ash mass. These particles are formed primarily through ash vaporization, nucleation, and coagulation/condensation mechanisms, which lead to compositions notably different compared to other fine or coarse particle...

A suite of six coals, of widely differing As, Se, Ca, Fe, and sulfur contents, was burned under self-sustaining conditions in a 17kW downflow laboratory combustor. Size segregated ash-laden aerosol samples were isokinetically withdrawn and collected on a Berner low pressure impactor. Correlations between trace element concentration (As or Se) and t...

The fate of toxic metals released during pulverized coal combustion is an environmental concern for commercial coal-fired combustor operators. Antimony's behavior is one of the more intriguing of the regulated metals of concern because previous studies often report markedly different partitioning results. A study performed to characterize the parti...

The removal of mercury vapors under high temperature combustion or gasification conditions is an important problem for coal combustion and gasification technologies. Whereas previous work has shown that carbon based sorbents can capture mercury, primarily through physi-sorption at low temperatures (less than 200°C) the present work is concerned wit...

Regulations in the U.S. on the control of mercury emissions from industrial and utility boilers have spurred an interest in better understanding the behavior of mercury in combustion flue gas. Pilot- and full-scale studies have shown that the addition of halogen compounds such as chlorine and bromine to combustion systems influences the chemistry o...

This paper presents a method for integrating two-phase flow into the vector formulation of the One-Dimensional Turbulence model (ODT) without the introduction of any additional free parameters into the model. ODT is an unsteady turbulent flow simulation model implemented on a one-dimensional domain, representing flow evolution as observed along a l...

The impacts of NO and SO2 on speciated mercury measurements from a wet chemical conditioning system were investigated. A reactor previously used to elucidate the impact of chlorine on mercury oxidation in combustion products was used. NO injected directly into the KCl impinger of the conditioning system was shown to reduce mercury oxidation by 44%...

Primary ultrafine participate matter (PM) is produced during pulverized coal combustion by the nucleation and heterogeneous condensation of vapor-phase species. This differs from the mechanisms that control the formation of the supermicron fly ash that is heavily influenced by the fragmentation and coalescence of aluminosilicate phases derived from...

Sorption of cesium and strontium on kaolinite powders was investigated as a means to minimize the emissions of these metals during certain high-temperature processes currently being developed to isolate and dispose of radiological and mixed wastes. In this work, nonradioactive aqueous cesium acetate or strontium acetate was atomized down the center...

This paper is concerned with health effects of the ash aerosol formed from the co-combustion of municipal sewage sludge (a CO2 neutral, ostensibly ‘green’ biomass fuel) with pulverized coal. To study, and mitigate, possible lung injury caused by inhalation of these ash particles, it is useful to employ ‘Health Effects Engineering’, which involves c...

An 18kW, cylindrical (inside diameter=15-cm), 6-m high, laminar, downflow furnace was used to investigate the mechanisms governing reactive scavenging of cadmium vapors from combustion environments, by hydrated lime and kaolinite powder sorbents. Two major physical mechanisms dominate the reaction rate and sorbent utilization during the capture of...

Oxy-fuel combustion of pulverized coal provides additional degrees of freedom that can be used to control flame stability and minimize NOx emissions. One such degree of freedom is the partial pressure of oxygen, PO 2, in the transporting fluid, which would normally consist of recycled flue gas. This paper presents results of research directed at co...

The need for inexpensive, effective NOx control has spawned numerous technological advances, with the comeback of coal reburning technology, becoming an attractive technology for many utilities. The industry continues to reinvent itself through innovative developments such as oxygen-enhanced reburning and in-situ gasification of biomass to generate...

The potential use of sorbents to manage ultrafine ash aerosol emissions from residual oil combustion was investigated using a downfired 82 kW laboratory-scale refractory-lined combustor. The major constituents were vanadium (V), nickel (Ni), iron (Fe), and zinc (Zn). The overall ash content of residual oil is very low, resulting in total ash vapori...

High temperature mechanisms of interaction between a dispersed kaolinite aerosol and vaporized sodium and lead were investigated using experimental data obtained from an 18 kW downflow furnace. The validity of using aerosol size fractionation to determine the extent of reaction between metal and substrate was confirmed through a series of specializ...