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ENERGY RESEARCH CENTER

LEHIGH ENERGY UPDATE

Vol. 33, No. 1 June 2018 www.lehigh.edu/energy

FOSSIL ENERGY – FLEX-FUEL ANALYSIS WITH LIBS

There is a renewed interest in developing fuel conversion systems, capable of running on a variety of fuels, and easily deployable for distributed generation applications. These kind of reactors will be faced with feedstock materials with large inherent variability in composition and other important properties. It is important to get a handle on the fuel quality variability, since it affects fuel conversion system operation and control, maintenance and availability, and the extent and treatment of environmental pollution associated with the system. Typically, laboratory analyses of fuel samples are performed, which require utilization of an array of equipment and procedures. However, these laboratory analyses cannot be performed fast enough to provide fuel information that can be incorporated in operational schemes or control logics.

The Lehigh University Energy Research Center (ERC) and the Energy Research Company (ERCo), of New Jersey, have developed a laser-based approach for rapid analysis of fuels. This approach consists of a combination of LIBS, or Laser-Induced Breakdown Spectroscopy, and advanced Artificial Intelligence (AI) techniques. LIBS is a type of plasma emission spectrometry in which a material sample

WATER-ENERGY NEXUS – NOVEL TECHNOLOGY FOR REMOVAL OF TOXIC METALS FROM IMPAIRED WATER SOURCES

A major issue currently facing society is the demand not only for clean drinking water but also for water that can be recycled for industrial applications. Target applications include coal-fired effluent streams, such as from wet flue gas desulfurization (WFGD) systems, as well as municipal wastewater sources and agricultural drainage. There is strong interest in water cleaning technologies capable of removing most toxic species of these pollutants; for example, mercury in its cationic states, Hg(I) and Hg(II), and selenium in its anionic forms, Se(IV) and Se(VI), as well as nitrate in treated wastewater. Current coal-fired plant impaired wastewater treatment practices include the addition of copious amounts of acid, base and chemicals like organo sulfides and ferric chloride to precipitate the regulated metals and metalloids. From a sustainability viewpoint, this process is very inefficient, produces sludge and imparts high dissolved solids into the treated water. Additional thermal treatment of the wastewater is energy intensive, and it is associated with high treatment costs.

Lehigh University and Air Products are working on the development of a novel water treatment technology based on a new class of low-cost sorbents, known as Hybrid Ion Exchange Zirconium Oxide Nanomaterials or HIX-NanoZr, which exhibit specific affinities toward both toxic metals, metalloids and nitrates. The project team includes Drs. Arup SenGupta and Carlos Romero, and Zheng Yao from Lehigh University, and Drs. Vipul Dholakia and Ranajit Ghosh from Air Products.

HIX-NanoZr are essentially polymeric cation and anion exchange resins within which Zr(IV) or ZrO2 nanoparticles have been irreversibly dispersed for sorption enhancement, robustness, regenerability and reuse. Prof. SenGupta, lead faculty in the project, explains, “Zirconium is innocuous, relatively inexpensive and poses no health hazard whatsoever. Despite this, widespread use of ZrO2 has been limited due to its poor mechanical strength and unsatisfactory attrition resistance in fixed-bed or any flow-through systems. However, new developments, and recent field applications and testing at Lehigh University have

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is vaporized during a laser pulse, forming a plasma, for sample elemental composition detection. Light emitted from the plasma is transmitted to a grating spectrometer, where the spectrum is recorded using intensified charge-coupled device arrays. Robert De Saro President of ERCo says, “In principle, LIBS can detect most elements in the sample, limited by the amount present and the specific LIBS configuration chosen.”

A series of projects has provided the opportunity to test the combined LIBS-AI technique on different feedstocks of interest in flex-fuel conversion systems. These projects were supported by the Department of Energy (DOE), the New York State Research & Development Authority (NYSERDA), and utility companies and industrial partners. “These projects have allowed an assessment of the capabilities of LIBS, fitted with advanced algorithms, for fuel identification and determination of fuel properties,” says ERC’s director, Dr. Carlos Romero, who was co-principal investigator of the projects. The fuels tested include different ranks of coal and coal refuse, different ranges of biomass (residues, energy crops and woody biomass), and municipal solid waste (MSW).

An experimental LIBS set-up was engineered for measurement of a range of fuels. The optical set-up consisted of an excitation Nd:YAG (neodymium-doped yttrium aluminum garnet) laser, a sample chamber with motorized XY stage, optical spectrometer, and a computer. The laser used in the LIBS system yields coincident 10 ns pulses, at a repetition rate of 10 Hz. The spectrometer contains an Echelle type grating that allows for high resolution spectra to be collected over a broad wavelength range of 200 to 780 nm. “Software was developed to process the spectral data and a number of filtering techniques were applied to assure the data quality, while targeting inorganic components of interest in the sample – such as Si, Al, Fe, Na, Ca, Mg, K, Ti, as well as C and S,” says Joseph Craparo of ERCo, who led the LIBS system development. Atomic lines were identified for all elements of interest, which were both sensitive to concentration changes and strong enough to be detected over the background noise inherent in the optical and detection

Comparison of LIBS and Standardized Heating Value Data for a Range of Feedstocks

FOSSIL ENERGYcontinued from page 1

systems. Signal-to-background (S/B) and signal-to-noise (S/N) ratios in the range from 8 to 280 were register for the entire set of fuels tested in the program. Craparo explains, “Typically, a line with S/B and S/N of 3 or greater is suitable for measurement.”

“Different AI techniques were used to relate spectral data to corresponding sample properties, such as supervised artificial neural networks, support vector machine and self-organizing Kohonen maps,” says Zheng Yao of the ERC, who led the data processing part of the project. The use of advanced models provided a more robust method to develop calibration curves for the different elements of interest, and a way to obtain high order fuel properties from the elemental composition, such as ash content, fuel calorific value, and ash fusion temperatures. The coefficient of variation, defined as the ratio of the standard deviation to the mean value (σ/μ) for all elements of interest ranged from approximately 0.01 to 0.40. The figure below shows a diagram of data processing steps and heating value results for a range of biomass and coal feedstocks. The range of heating values encompasses values from 6,600 Btu/lb for rice hulls to 13,100 Btu/lb for Illinois coal. The combined root-mean square error (RMSE) of the measurements is ± 15.25 Btu/lb, or a relative accuracy of approximately ± 0.20%, in reference to the average heating value for the entire range. Yao adds, “Averaged heating value results from ten independent LIBS measurements of MSW indicated a RMSE of ± 4.50%.”

De Saro concludes, “Recent developments in advanced laser and optics have provided the opportunity of bringing LIBS to applications that require accurate detection of low concentrations of analytes. Distributed generation systems operating on flex-fuel mode represent one of those applications, where the value proposition justifies engineering these devices for rugged field operation.” Romero adds, “The integration of LIBS with advanced data processing techniques offers a powerful combination that provides fuel identification capabilities, and greater calibration and measurement accuracy.”

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now clearly established that nanoscale ZrO2 particles can be introduced inside both polymeric cation and anion exchange resins, producing hybrid materials with high sorption capacity due to high surface area to volume ratio. The hybrid polymeric particles offer durability and excellent flow-through properties in fixed-bed processes without needing the addition of chemicals like organo sulfides, HCl and ferric chloride.”

Dr. Dholakia, Gas Applications Technology Manager at Air Products, adds, “The goal of the current project is to study the underlying sorption/desorption mechanisms of the material, and fully evaluate the impaired water treatment capabilities of the concept, using simulated and actual WFGD samples in the laboratory. The regeneration performance of the system, with pressurized CO2, is also being evaluated.”Yao adds, “The plan is to move to a larger, pilot-scale unit for testing in side-stream mode at a utility company.

A diagram of the proposed novel water treatment system by Lehigh and Air Products is shown on the figure below, together with a photograph of the current laboratory scale setup. The proposed concept includes a three-column system to remove mercury, arsenic and selenium, at different pHs,

but without any external addition of acid and base. At slightly acidic pH, the system can selectively remove arsenate and selenite anions, while at alkaline pH, cationic cadmium, mercury, zinc, etc. can be absorbed very selectively.

Romero, director of the Energy Research Center (ERC), explains, “Simply by swinging pH through the use of carbon dioxide and lime, the HIX-NanoZr can be regenerated and reused for tens of cycles.” Weak-acid cation (WAC) exchange fibers in the middle cell would reduce the pH to around 5.0 through removal of alkalinity, thus enhancing the arsenic removal capacity of HAIX-NanoZr.

Some background results are included in the figure below. The figure on the left illustrates the HAIX-NanoZr material. The figure on the right shows the effectiveness of this material in removing arsenic from contaminated water, over several thousands of bed volumes. Subsequently, the HAIX-NanoZr material was amenable to regeneration at slightly alkaline pH through the use of lime, an innocuous and readily available chemical routinely used in FGD systems. Arsenic removed can be safely contained as Fe(III) or calcium arsenate, which has been demonstrated in arsenic-inflicted rural communities around the world.

According to Dr. Ghosh, Applications Technology Director at Air Products, “The appealing part of a system, using HIX-NanoZr materials, is that they are amenable to regeneration and reuse for many cycles using only carbon dioxide (CO2), lime and plant waste heat, depending on the required acidity or basicity of the application. Air Products is focused on developing safe and sustainable technologies using industrial gases, and this project aligns with that goal.”

WATER-ENERGY NEXUScontinued from page 1

Impaired Water Treatment Scheme and Laboratory Setup for Treatment of Both Toxic Metal Cations and Anions Through pH Manipulation

Schematic and SEM-TEM Photograph of Hybrid Anion Exchanger Nanomaterial (HAIX-Nano) and Arsenic Removal Performance of the Material for 6000 Bed Volumes

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