Municipal solid waste (MSW)'s 40-60 % carbon content makes it a feedstock for biofuel production via pyrolysis. One challenge in the conversion process is MSW fouling due to thermal decomposition. The accumulated deposit on the injection screw often leads to plugging and constriction. This study examined the morphology and composition of the MSW fouling deposit and conducted a thermal simulation to understand the temperature gradience of the injection screw. Surface modifications including smoothening and anti-adhesion coating were proposed for the injection screw to address the deposit problem. For evaluating the candidate mitigations, a bench-scale fouling test was developed with the gas environment, temperature, and sliding speed relevant to the contact interface between the MSW particles and the screw. Results suggested that a smoother screw surface could reduce the grip and a non-metallic coating with a lower surface energy could decrease adhesion, consequently leading to less fouling. Specifically, reducing the roughness from 2 to 0.6 and then to 0.2 mu m proportionally decreased the amount of deposit, and the diamond-like-carbon, CrN, and NiCr-CrC composite coatings effectively hindered the fouling process. This study provides fundamental insights into the MSW fouling and proof-of-concept of potential mitigations through the screw surface modification.

Abstract We preview two processes that facilitate using formic acid (HCOOH) as a liquid hydrogen carrier to store renewably‐generated electrical energy and then release it to generate electrical power cleanly for backup or emergency applications. First, we show that simultaneously oxidizing an organic solute (typically a waste stream) can assist the electrochemical synthesis of formic acid by lowering the cell potential. The electrolyser comprises a hybrid 3‐chamber PEM stack that reduces CO₂ via a gas‐diffusion cathode boosted by the oxidation of aqueous methanol. However, the extent of the boosting needs to be optimized across the whole operation of the cell. Next, we present results from an intensified reactor for decomposing formic acid back into H₂ and CO₂ at elevated pressure so that the H₂ can be used in a fuel cell. The reactor combines three operations: Vaporization of the formic acid, its decomposition, and separation of the product stream. Their close coupling affords energy savings and a compact design that could be mounted on a mobile skid. We briefly discuss the electrode catalyst that facilitates the first process and two thermally activated catalysts (Ir supported on covalent triazine framework and Pd supported on carbon) that enable the second process.

•First review of oxygenate vapor pressure measurement and prediction.•Specifies vapor pressure measurement methods suitable for use with oxygenates.•Reviews methods to predict fuel vapor pressure.•Compares many model outputs to measured RVP for real oxygenate-gasoline blends.

The Characterization and Valorization of Aqueous Phases Derived from Liquefaction and Upgrading of Bio-Oils project developed processes to extract value from the organics within aqueous streams derived from biomass direct liquefaction processes. The focus of the project was twofold. First, we characterized a diverse set of aqueous streams from numerous processes and feedstocks. The characterization effort served to inform this project toward development around the most prevalent compounds to maximize versatility and impact. We analyzed diverse streams from hydrothermal liquefaction of lignocellulosic, algal, and waste feedstocks; catalytic fast-pyrolysis aqueous phases; fast-pyrolysis aqueous phases; and aqueous phases produced by hydroprocessing of fast-pyrolysis bio-oil. Second, thermochemical catalytic processes were developed to convert aqueous-phase organics into useful products. These processes focused mostly on organic acids and specifically acetic acid, which was found to be ubiquitous from the characterization effort. A LaxZryOz catalyst was discovered and developed for the ketonization of acids to ketones in the condensed aqueous phase. A dual-bed steam reforming process was developed to convert acids and other organics to hydrogen for bio-oil hydroprocessing. The dual-bed reforming process consisted of a ketonization step followed by a steam reforming step with Co as the active metal. The dual-bed process significantly reduced the rate of coke deposition versus direct steam reforming of the organic acids and beneficially produced CH4 below the equilibrium value. Finally, we demonstrated direct conversion of aqueous-phase organics to olefins over a ZnxZryOz catalyst. Each thermochemical catalytic process was demonstrated with process-derived aqueous mixtures. Model compounds were used to benchmark performance and optimize conditions, but emphasis was placed on utilizing “real” aqueous streams whenever possible. A liquid-liquid extraction process using methyl tert-butyl ether as the solvent was developed to segregate dissolved inorganic species and sugars from desirable light oxygenates such as acids and alcohols. Furthermore, a carbon treatment to remove color bodies was employed after it was found the presumably heavy organic chromophore species deactivated catalysts. These economic separation processes allowed for the successful demonstration of stable catalytic processing in the condensed-phase ketonization, dual-bed reforming, and direct olefin production processes for tens to hundreds of hours, which were limited only by the quantity of feed available. Techno-economic analysis of these processes demonstrated the impact possible when capturing “waste” organics as valuable products. The condensed-phase ketonization process for converting aqueous stream acids to ketones followed by reduction and dehydration to olefins sold as a co-product resulted in the reduction of the minimum fuel selling price by about 13% compared to the anaerobic-digestion, aqueous-phase treatment base case (3.74 to 4.29/GGE). The dual-bed reforming process was commensurate in price to the anaerobic digestion base case (4.24 versus 4.29/GGE). However, the need for external natural gas to produce hydrogen for bio-oil hydroprocessing was eliminated, thereby lowering the carbon impact of the process.

We report here on an experimental study to produce refinery-ready fuel blendstocks via catalytic hydrodeoxygenation (upgrading) of pyrolysis oil using several biomass feedstocks and various blends. Blends were tested along with the pure materials to determine the effect of blending on product yields and qualities. Within experimental error, oil yields from fast pyrolysis and upgrading are shown to be linear functions of the blend components. Switchgrass exhibited lower fast pyrolysis and upgrading yields than the woody samples, which included clean pine, oriented strand board (OSB), and a mix of pinon and juniper (PJ). The notable exception was PJ, for which the poor upgrading yield of 18% was likely associated with the very high viscosity of the PJ fast pyrolysis oil (947 cp). The highest fast pyrolysis yield (54% dry basis) was obtained from clean pine, while the highest upgrading yield (50%) was obtained from a blend of 80% clean pine and 20% OSB (CP8OSB2). For switchgrass, reducing the fast pyrolysis temperature to 450 degrees C resulted in a significant increase to the pyrolysis oil yield and reduced hydrogen consumption during hydrotreating, but did not directly affect the hydrotreating oil yield. The water content of fast pyrolysis oils was also observed to increase linearly with the summed content of potassium and sodium, ranging from 21% for clean pine to 37% for switchgrass. Multiple linear regression models demonstrate that fast pyrolysis is strongly dependent upon the contents of lignin and volatile matter as well as the sum of potassium and sodium. (C) 2016 Elsevier Ltd. All rights reserved.

This report summarized the results obtained in FY2017 Q3 of a collaborative effort between researchers at NREL, PNNL, and INL to develop rapid screening methods and models to predict the fact pyrolysis conversion performance of a range of biomass materials.

Hydrothermal liquefaction (HTL) is a viable thermochemical process for converting wet solid wastes into biocrude that can be hydroprocessed to liquid transportation fuel blendstocks and specialty chemicals. The aqueous byproduct from HTL contains significant amounts (20-50%) of the biogenic feed carbon, which must be valorized to enhance economic sustainability of the process on an industrial scale. In this study, aqueous fractions produced from HTL of food industry wastes, municipal wastes, and biomass cultivated on wastewater were characterized using a wide variety of analytical approaches. Organic species present in these aqueous fractions were identified using two-dimensional gas chromatography equipped with time-of-flight mass spectrometry. Identified compounds include organic acids, nitrogen compounds, alcohols, aldehydes, and ketones. Conventional gas chromatography coupled with flame ionization detection and liquid chromatography utilizing refractive index detection were employed to quantify the identified compounds. Inorganic species in the aqueous streams were also were quantified using ion chromatography and inductively coupled plasma optical emission spectroscopy. The concentrations of organic compounds and inorganic species are reported, and the significance of these results are discussed in detail.

Efficient conversion of all components in lignocellulosic biomass is essential to realizing economic feasibility of biorefineries. However, lignin cannot be fermented using biochemical routes. Furthermore, high lignin and high ash residues from simultaneous saccharification and fermentation (SSF) is difficult to thermochemically process due to feed line plugging and bed agglomeration. In this study a corn stover SSF digester residue was thermally pretreated at 300 degrees C for 22.5 min and gasified in a fluidized bed gasifier to study the effect of thermal pretreatment on its processing behavior. Untreated, pelletized SSF residue was gasified at the same conditions to establish the baseline processing behavior. Results indicate the thermal pretreatment process removes a substantial portion of the polar and non-polar extractives, with a resultant increase in the concentration of lignin, cellulose, and ash. Feed line plugging was not observed, although bed agglomeration occurred at similar rates for both feedstocks, suggesting that overall ash content is the most important factor affecting bed agglomeration. Benzene, phenol, and polyaromatic hydrocarbons in the tar were present at higher concentrations in the treated material, with higher tar loading in the product gas. Total product gas generation is lower for the treated material, although overall gas composition does not change. (C) 2016 Published by Elsevier

Residues high in lignin and ash generated from the simultaneous saccharification and fermentation of corn stover were thermally pretreated in an inert (N-2) atmosphere to study the effect of time and temperature on their softening points. These residues are difficult to feed into gasifiers due to premature thermal degradation and formation of reactive liquids in the feed lines, leading to plugging. The untreated and treated residues were characterized by proximate and ultimate analysis, and then analyzed via TGA, DSC, C-13 NMR, Py-GC-MS, CHNO/S, and TMA. Interpretation of the compositional analysis indicates that the weight loss observed during pretreatment is mainly due to the thermal decomposition and volatilization of the hemicelluloses and amorphous cellulose fractions. Fixed carbon increases in the pretreated material, mostly due to a concentration effect rather than the formation of new extra poly-aromatic material. The optimal processing time and temperature to minimize the production of carbonyl groups in the pretreated samples was 300 Cat a time of 30 min. Results showed that the softening point of the material could be increased from 187 degrees C to 250 degrees C, and that under the experimental conditions studied, pretreatment temperature plays a more important role than time. The increase in softening point was mainly due to the formation of covalent bonds in the lignin structures and the removal of low molecular weight volatile intermediates. (C) 2016 Elsevier B.V. All rights reserved.

The aqueous fraction generated from hydrothermal liquefaction (HTL) of algae contains approximately 20–35% of the total carbon present in the algal feed. Hence, this aqueous fraction can be utilized to produce liquid fuels and/or specialty chemicals for economic sustainability of HTL on an industrial scale. In this study, aqueous fractions produced from HTL of freshwater and saline-water algal cultures were analyzed using a wide variety of analytical instruments to determine their compositional characteristics. Organic chemical compounds present in eight aqueous fractions were identified using two-dimensional gas chromatography equipped with time-of-flight mass spectrometry. Identified compounds include organic acids, nitrogen compounds and aldehydes/ketones. Conventional gas chromatography and liquid chromatography methods were utilized to quantify the identified compounds. Inorganic species in the aqueous stream from HTL of algae also were quantified using ion chromatography and inductively coupled plasma optical emission spectroscopy. The concentrations of organic chemical compounds and inorganic species are reported. The amount quantified carbon ranged from 45 to 72% of the total carbon in the aqueous fractions.

Two-dimensional gas chromatography coupled with time-of-flight mass spectrometry is a powerful tool for identifying and quantifying chemical components in complex mixtures. It is often used to analyze gasoline, jet fuel, diesel, bio-diesel and the organic fraction of bio-crude/bio-oil. In most of those analyses, the first dimension of separation is non-polar, followed by a polar separation. The aqueous fractions of bio-crude and other aqueous samples from biofuels production have been examined with similar column combinations. However, sample preparation techniques such as derivatization, solvent extraction, and solid-phase extraction were necessary prior to analysis. In this study, aqueous fractions obtained from the hydrothermal liquefaction of algae were characterized by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry without prior sample preparation techniques using a polar separation in the first dimension followed by a non-polar separation in the second. Two-dimensional plots from this analysis were compared with those obtained from the more traditional column configuration. Results from qualitative characterization of the aqueous fractions of algal bio-crude are discussed in detail. The advantages of using a polar separation followed by a non-polar separation for characterization of organics in aqueous samples by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry are highlighted.

This research investigates the bed agglomeration phenomena during the steam gasification of a high-lignin residue produced from the simultaneous saccharification and fermentation (SSF) of corn stover in a bubbling fluidized bed. The studies were conducted at 895 degrees C using alumina as bed material. Biomass was fed at 1.5 kg/h, while steam was fed to give a velocity equal to 2.5 times the minimum fluidization velocity, with a steam/carbon ratio of 0.9. The pelletized feedstock was co-fed with a cooling nitrogen stream to mitigate feed line plugging issues. Tar production was high at 50.3 g/Nm(3), and the fraction of C10+ compounds was greater than that observed in the gasification of traditional lignocellulosic feedstocks. Carbon closures over 94% were achieved for all experiments. Bed agglomeration was found to be problematic, indicated by pressure drop increases observed below the bed and upstream of the feed line. Two size categories of solids were recovered from the reactor: +0.25 mm and -0.25 mm. After 2.75 h of experiment, 61.7 wt % was recovered as -0.25 mm particles and 38.2 wt % of the recovered reactor solids were +0.25 mm. A sizable percentage (31.8 wt %) was +0.841 mm. The -0.25 mm particles were mainly formed by the initial bed material (Al2O3). Almost 50 wt % of the +0.841 mm particles was found to be formed by organics. The unreacted carbon remaining in the reactor resulted in a low conversion rate to product gas. Inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) confirmed that the large agglomerates (+0.841 mm) were not encapsulated bed material but rather ungasified feedstock pellets with sand particles attached to it.

Feedstock composition can affect final fuel yields and quality for the fast pyrolysis and hydrotreatment upgrading pathway. However, previous studies have focused on individual unit operations rather than the integrated system. In this study, a suite of six pure lignocellulosic feedstocks (clean (no bark) pine, whole-tree (including bark) pine, tulip poplar, hybrid poplar, switchgrass, and corn stover) and two blends (equal weight percentages whole-tree pine/tulip poplar/switchgrass and whole-tree pine/clean pine/hybrid poplar) were prepared and characterized. These materials then underwent fast pyrolysis and hydrotreatment. Although some feedstocks showed a high fast pyrolysis bio-oil yield, such as tulip poplar at 60%, high yields in the hydrotreater were not always observed. Results showed overall fuel yields of 17% (switchgrass), 20% (corn stover), 24% (tulip poplar, blend 1, blend 2), 25% (whole-tree pine, hybrid poplar), and 27% (clean pine). Simulated distillation of the upgraded oils indicated tha...

In this study the aqueous phases resulting from the hydrothermal liquefaction (HTL) of biomass and the hydrotreatment (HT) of fast pyrolysis bio-oils were analyzed via TC, COD, GC-MS, GC-FID, HPLC, and ICP-OES to determine the organic and inorganic species present and the quantitative amounts of each. This work is necessary to address a significant knowledge gap in the literature related to the aqueous phases from thermochemical processes. Results showed that water from the hydrotreatment of eight different bio-oils contained less than 1 wt% total carbon, in many cases less than 0.2%. Negligible organic carbon was observed. HTL samples contained between 1 and 2 wt% carbon. Due to the large volume of water added to the HTL feedstock and the dilute samples generated, this accounts for 34-45% of the total carbon sent to the reactor. The majority of this carbon was present as acids, with glycolic acid and acetic acid having the highest concentrations. Alcohols, specifically methanol and ethanol, were also present. Numerous ketones were observed, consisting of mainly acetone and cyclopenta-ones. The amount of the total carbon identified and quantified in the HTL samples ranged from 64 to 82%. Inorganic species present in the HT samples were sodium, silicon, and sulfur. The highest levels of sulfur were observed in the grasses and agricultural residue (corn stover). The HTL samples exhibited much higher inorganic content, with very high levels of sodium and potassium. Alkali and alkali earth metals, as well as sulfur, were also present at levels high enough to raise concerns for the use of catalysts in downstream upgrading or reforming processes. (C) 2015 Elsevier Ltd. All rights reserved.