John Grace

John Grace
University of British Columbia - Vancouver | UBC · Department of Chemical and Biological Engineering

About

608
Publications
53,526
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22,570
Citations
Citations since 2016
86 Research Items
9497 Citations
201620172018201920202021202202004006008001,0001,2001,400
201620172018201920202021202202004006008001,0001,2001,400
201620172018201920202021202202004006008001,0001,2001,400
201620172018201920202021202202004006008001,0001,2001,400

Publications

Publications (608)
Article
The charges acquired by polyethylene and glass particles fluidized by argon, nitrogen, and air at different humidity levels in acrylic and steel columns have been measured. Increased bed expansion at higher fluidization gas velocities lowered the space charge effect, allowing the particles to acquire more charges. The low dielectric strength of arg...
Article
This work presents a new dynamic modelling approach for calcium looping systems that allows explicit sorbent deactivation and purge/makeup. These are common in plant operations, but often neglected in modelling. This model adopts a Monte Carlo approach, tracking merely 100 particles between the carbonator and the calciner for 60 reaction cycles wit...
Article
Full-text available
Fluidized bed bioreactors are widely used in wastewater treatment applications. Such reactors employ gel beads or hard particles covered with a biofilm layer. These particles lose more energy due to deformation when they collide than particles with high mechanical resistance. This energy loss can result in heterogeneity in particle distribution, in...
Article
This paper investigates the effect of calcination temperature and duration on the cyclic CO2 capture performance of natural lime-based sorbents. Tests showed that increasing calcination temperature considerably reduced the sorbent reactivity over the first few calcination-carbonation cycles. No significant variation in performance was observed when...
Article
A jet attrition model is developed to predict the evolution of the particle size distribution in fluidized beds. This model predicts changes in particle size distribution due to impact attrition in the jet region as a function of operating parameters – temperature, particle impact velocity and time. The model provides good agreement with experiment...
Article
Full-text available
Landfill leachate is exposed to sunlight through on- and off-site leachate treatment and disposal to surface water bodies. Very little is known about the potential phototransformation of fluorotelomer compounds in landfill leachates, which can undergo environmental oxidation and produce perfluorocarboxylic acids (PFCAs). This study investigated pho...
Article
Mechanistic models are commonly used to simulate gas-fluidized bed reactors. Gas is assumed to pass through two compartments in parallel, one a dilute phase and the other a dense phase containing most, or all of, the particles, as well as interstitial gas. Interphase mass transfer plays a key role, since most of the gas passes through the dilute ph...
Article
Sphericity, a measure of how much a particle’s shape deviates from spherical, is useful as a shape factor when characterizing particulate materials. However, particle surface areas, required when determining the sphericity, are very difficult to measure. As a result, the circularity, derivable from microscopic views, is often measured instead and a...
Article
An iron‐based catalyst from bauxite residue (aka BR and red mud) was developed for removing biomass gasification tar. Its performance was investigated with naphthalene as the model tar compound. This was achieved by measuring the catalytic naphthalene conversion at five space velocities and at four temperatures in the 500°C‐800°C range, both in a N...
Article
The FluidBed model in Aspen Plus v10 is applied to simulate Calcium-looping for production of hydrogen-rich product gas from a bubbling fluidized bed carbonator of a dual fluidized bed (DFB) reactor. The predictions are compared with experimental results from a steady-state 20 kWth DFB biomass gasifier performing Ca-looping, fed with tar-free synga...
Article
Biotransformation of 6:2 fluorotelomer sulfonate (FTS) results in the formation of short-chain (C4 – C6) perfluorocarboxylic acids (PFCAs) in landfill leachate. Although leachate substrate concentrations (i.e., organic carbon, ammonia) vary widely, their effects on 6:2 FTS biotransformation and PFCAs formation are unknown. This study investigated t...
Article
The effects of chemical reactions on the attrition of oxygen carrier particles and CO2 sorbent based on a chemical looping reforming (CLR) process with intrinsic CO2 capture were analyzed. Iron/hematite as an oxygen carrier, and limestone/lime as a CO2 sorbent were tested in a jet attrition apparatus. Attrition tests were conducted with particles o...
Article
The effect of moisture on Shengli lignite breakage behavior and energy efficiency was studied experimentally using a standard Hardgrove mill fitted with a wattmeter. The grinding process concerned both the inputs, namely the occurrence and content of water and instantaneous energy consumption and the outputs, size-reduction and product fineness. Re...
Article
The spatial distribution of solid particles is a key factor affecting the performance of fluidized bed reactors. Non-invasive techniques including radioactive particle tracking (RPT) and positron emission particle tracking (PEPT) are deployed to measure the solids distribution. Different methods to calibrate the particle tracking measurements have...
Article
This paper presents a steady-state simulation of sorbent-enhanced steam methane reforming in turbulent fluidized bed reactors. The effects of different operating conditions are assessed, including reactor temperature, operating pressure, gas feed composition and sorbent/methane molar feed ratio. The potential system performance is also evaluated wh...
Article
This paper investigates the equilibrium performance of CaO hydration and CaCO3/Ca(OH)2 co-calcination in calcium-looping processes. A novel lime hydration configuration is proposed, introducing saturated steam as the reactivating reagent and direct-heat-removal medium. The proposed hydrator generates a substantial amount of superheated steam, used...
Article
To study the effect of particle properties on forces acting on immersed internals during start-up of fluidized bed reactors, forces on a horizontal slat were measured in fluidized beds of four types of particulate materials (i.e. FCC catalyst particles and three silica sands of different sizes). The forces were measured by strain gauges adhered on...
Article
Consumer products containing fluorotelomer polymers are a source of fluorotelomer compounds to the environment following their disposal at landfills. The fate and transformation of fluorotelomer compounds are unknown in landfill leachates. This study investigates the aerobic biotransformation of 8:2 fluorotelomer alcohol (FTOH) and 6:2 fluorotelome...
Article
Fluorotelomer compounds in landfill leachate can undergo biotransformation under aerobic conditions and act as a secondary source of perfluorocarboxylic acids (PFCAs) to the environment. Very little is known about the role of various microbial communities towards fluorotelomer compounds biotransformation. Using an inoculum prepared from the sedimen...
Article
This paper investigates the performance of combining limestone calcination with catalytic methane reforming and combustion in turbulent fluidized bed membrane reactors. The equilibrium performance of the process was evaluated using Aspen simulation, with a unique correlation to estimate the required gaseous feed composition for autothermal and comp...
Article
Efficient elimination of tar is a challenge to the development of biomass gasification as a viable clean energy technology. Catalytic reforming is effective in reducing biomass-derived tars. However, commercial metal-based catalysts are expensive and prone to deactivation. Developing economically viable and environmentally benign catalysts from ren...
Article
Simultaneous removal of three polycyclic aromatic hydrocarbons (acenaphthene, fluorene and fluoranthene) co-existing with three heavy metals (Ni, Pb and Zn) in artificially contaminated soil from the vicinity of an oil refinery was examined by column flushing of solutions containing Triton X-100 + Ethylenediaminetetraacetic acid (EDTA) and Tween 80...
Article
A dual-compartment slot-rectangular spouted bed (DSRSB) reactor was designed and built to torrefy sawdust. The effects on torrefaction performance of temperature from 240 to 300 °C, sawdust feedrate from 600 to 1400 g/h and oxygen concentration from 0 to 9 vol% were explored. The temperature difference between the adjacent compartments was limited....
Article
The solids circulation rate between two reactors is a key parameter in circulating fluidized bed reactor processes. This paper reports on attempts to establish the reliability of a novel thermal-tracing technique to provide useful solid circulation information for industrial-scale systems. A novel butterfly valve technique was developed to test the...
Article
Full-text available
NaA zeolite membranes were prepared on the inner surfaces of ceramic α-alumina tubes based on an aqueous phase synthesis in order to investigate the influence of different silica sources on NaA zeolite membrane synthesis and zeolite layer thickness with reference to the gas separation properties. SEM and XRD results indicated that zeolite prepared...
Article
Full-text available
This paper develops a simple, yet practical, steady-state kinetic reactor model for lime-enhanced biomass steam gasification in a dual fluidized bed reactor, one of the most promising technologies for sustainable production of hydrogen. The focus is on kinetic modeling of the bubbling fluidized bed gasifier, accounting for in situ sorbent carbonati...
Article
Operation of a dual fluidized bed, consisting of a riser as combustor and bubbling bed as gasifier, for synthesis gas production from a solid fuel requires determination of the solids circulation rate and char transfer rate. The performance relies on supplying sufficient heat from the combustor to the gasifier by circulation of solids between these...
Article
The attrition of binary mixtures of iron powder, as a representative oxygen carrier, and limestone, as a CO 2 sorbent, was investigated to examine the interactions of two different solid species. An air-jet apparatus based on ASTM D5757, with several improvements, was used to test particle attrition for various times (3, 6 and 12 h), temperatures (...
Article
Combined limestone calcination, catalytic methane reforming and combustion in a membrane reactor are simulated as a possible means to achieve autothermal and hydrogen-producing sorbent regeneration for calcium-looping technology. Aspen simulation is employed in order to analyze the equilibrium performance of the process, while a simple one-dimensio...
Article
Polybrominated diphenyl ethers (PBDEs) are present in biosolids and other solid wastes, as well as being detected in landfill leachates. As sand-bentonite mixtures are extensively used as basal liner materials for landfills, a sand-bentonite mixture was investigated by swelling tests and leaching column tests to determine whether it can effectively...
Article
This paper reviews the application of pulsed flow in fluidized and spouted beds, widely used in various industries. A number of pulsing studies have been performed to improve the performance of these beds, enhance mixing and promote homogeneity. One effective way to increase the efficiency is to pulse the incoming flow, removing inactive or dead zo...
Article
A computational model is developed to simulate evaporative spray injection into a hot gas–solid fluidized bed. Eulerian treatment of three phases is used, with a population balance model to account for variation in agglomerate sizes. Sub-models account for the interaction between droplets and hot particles, including momentum exchange, heat and mas...
Article
A probabilistic heat transfer model was developed that allows for the gradual evolution of bed-to-surface heat transfer coefficients with increasing superficial gas velocity when bubbling and turbulent flow structures co-exist. The model is based on the packet renewal theory and the probability of particle packets for the specific hydrodynamic regi...
Article
Full-text available
This study experimentally investigates the effects of gas extraction/addition, via multiple vertical membrane panels, on the hydrodynamics in different regions of a pilot-scale gas fluidized bed membrane reactor (FBMR), based on differential pressure signals measured at different vertical bed sections at high temperature. In a bed section where mem...
Article
Experiments were conducted to investigate the effect of adding fines on the tribo-charging of coarse glass beads. Four types of fines, i.e., copper, stainless steel, uncoated and silver-coated fine glass beads, mixed with 240–830 μm glass beads were conveyed by air through a stainless-steel spiral pipe acting as a tribo-charger. Regardless of the t...
Article
The interactions of bubbles and particles with fixed cylindrical tubes in two-dimensional fluidized beds were investigated by experiments and by simulations, based on results for single bubbles impinging on a tube. The experimental results based on PIV analysis support our previous force origin model and indicate that the model is able to successfu...
Article
A mathematical model that describes wet agglomerate breakage in a gas-solid fluidized bed was developed, utilizing the energy approach to assess agglomerate stability and the Kinetic Theory of Granular Flows (KTGF) to describe collisions between bed primary particles and agglomerates. Wet agglomerates are held together by liquid bridges that resist...
Article
Full-text available
Particle tracking methods using emitted radiation are attractive for following motion in opaque systems such as granular materials. Leading examples are Positron Emission Particle Tracking (PEPT) and Radioactive Particle Tracking (RPT). The application of such techniques sometimes requires the use of tracer particles which differ in size, density a...
Article
The effects of the pulsation frequency and slot dimensions on the hydrodynamic characteristics and the particle motion of sawdust of mean diameter 1.29 mm were investigated in a pulsed slot-rectangular spouted bed. Pulsation frequencies ranged from 1 to 5 Hz. The pulsed gas flow helped to mobilize the sawdust particles, regardless of the slot dimen...
Article
A slot-rectangular spouted bed (SRSB) reactor was employed to torrefy spruce-pine-fir sawdust in an oxidative atmosphere. The effects of torrefaction temperature (240-300 °C) and feed-gas oxygen concentration (3-9 vol.%) on torrefaction performance and solid product properties were investigated. Adding oxygen in the feed-gas led to more uniform tem...
Article
Experimental fluidization results were compared for three gas distributors with the same opening ratio but different orifice inclinations (30°, 45°, and 90°). Hydrodynamic studies were conducted with glass beads (diameter 154 μm) to evaluate the impacts of orifice inclination and static bed depth on pressure drop, pressure drop fluctuations, bed ex...
Article
Sawdust was subjected to torrefaction in a “semi-batch” slot-rectangular spouted bed (SRSB) reactor at temperatures from 240 to 330 °C and biomass feed rates from 220 to 710 g/h. Stable spouting of the sawdust was achieved in the slot-rectangular spouted bed, although the pressure drop across the reactor was observed to oscillate. Compared to the b...
Article
Full-text available
The effects of organic matter (80% humic and 15% fulvic acid) and coexistence of heavy metals (Ni, Pb and Zn) on sorption of three polycyclic aromatic hydrocarbons (PAHs)—acenaphthene, fluorene and fluoranthene—were examined for kaolinite, 60% kaolinite + 40% sand, and 43% kaolinite + 42% sand + 15% bentonite. In total 108 batch sorption tests of P...
Article
The effects of particle roughness and deformability on the fluid dynamics of liquid fluidized beds were investigated using a 190.5-mm-diameter column and particles with different surface finish and stiffness. Glass beads and plastic “BBs” coated using different techniques were employed as the rigid particles, while cooked starch pearls (tapioca) an...
Article
The effects of soil components such as clay minerals and as humic acids, as well as co-existing metals and polycyclic aromatic hydrocarbons, on desorption and mobility are examined. Three types of artificially blended clay and clay mineral mixtures (pure kaolinite, kaolinite + sand and kaolinite + sand + bentonite), each with different humic acid c...
Article
This paper provides a perspective on the current knowledge and potential areas of future research related to electrostatics in fluidized beds. Aspects addressed include characterization techniques, charge generation and dissipation mechanisms, interplay between the electrostatics and hydrodynamics, charge control methods, applications of tribo-elec...
Article
By incorporating reaction kinetics and reactor hydrodynamics, a steady-state two-phase one-dimensional reactor model for biomass steam gasification in the bubbling fluidized bed gasifier of a dual fluidized bed reactor is developed. The generic two-step kinetic model adopted for biomass pyrolysis allows for predicting tar generation and cracking, a...
Article
Gas-solid fluidized beds, by their nature, are associated with intense and frequent collisions of solid particles with each other and with the vessel wall, causing tribo-electrification. Accumulation of electrostatic charges in fluidized bed reactors can result in severe problems such as agglomeration, wall fouling, nuisance and hazardous discharge...
Article
A population balance model is developed for the growth of pre-formed agglomerates in a fluidized bed with several agglomeration mechanisms considered. Primary agglomeration takes place when dry particles collide with the wet surface of the original agglomerate. Secondary agglomeration occurs either by wet particles colliding with the dry surface of...
Article
NaA zeolite membranes were synthesised in the secondary growth hydrothermal method based on the seeding of the inner surface of a ceramic α-alumina tube. The impacts of crystallisation time and zeolite precursor concentration (in H2O) were investigated. The structure and stability of the prepared NaA zeolite membranes were also investigated with op...
Article
Different from traditional seeded method, NaA Zeolite membranes (NZMs) were prepared by in-situ synthesis onto the inner-side of porous α -alumina tubular supports in a hydrothermal synthesis reactor. The influences of pretreatment of porous tubular support, temperature, time and synthetic cycle for the synthesis of the zeolite membranes were inves...
Article
The potential application of palladium-ruthenium composite membranes to the separation of hydrogen from chlorosilane gases in silicon-based industries was investigated. Palladium and palladium-ruthenium composite membranes were deposited on pretreated porous stainless steel substrates by electroless plating. Hydrogen permeation tests and temperatur...
Article
Sawdust particles of different sizes (0.25-0.5, 0.5-1.0 and 1.0-2.0 mm) were torrefied in a continuous slot-rectangular spouted bed reactor. The effects of particle size and temperature were investigated on the properties of the torrefied product, such as proximate analysis, ultimate analysis, HHV, skeletal density, and energy yield. Temperature wa...
Article
A study was undertaken to evaluate the operation of a slot-rectangular spouted bed (SRSB) when pulsed air flow at different frequencies and static bed heights was used to spout biomass particles. A pulsed air stream injected at frequencies from 1 to 5 Hz was applied simultaneously with the main spouting air flow to fluidize millet particles of mean...
Article
To investigate the impact of the column wall material on entrainment and electrification of fines in the freeboard of fluidized beds, fine powders were entrained by air at atmospheric temperature and 205 kPa in columns of diameter 0.15 m made of stainless steel and acrylic. Under equivalent operating conditions, changing the column wall material ch...
Article
Experiments were conducted on a lab-scale fluidized bed to study the distribution of liquid ethanol injected into fluidized catalyst particles. Electrical capacitance measurements were used to study the liquid distribution inside the bed, and a new method was developed to determine the liquid content inside fluidized beds of fluid catalytic crackin...
Article
Iron-based oxygen carrier (IBOC) is widely used in chemical looping processes (CLP) due to many advantages, and the low-cost ones are prospective for industry application. However, research on the redox properties of the low-cost IBOCs during CLP is still rarely seen, compared to those on the well prepared ones. In this work, an experiment is imple...
Chapter
This chapter reviews the main steam methane reforming (SMR) process, as well as widespread attempts to improve the process by such measures as partial oxidation (POX), autothermal operation, hydrogen-permeable membranes, and sorbent-enhanced reforming. Dry reforming has been shown to be mechanistically analogous to steam reforming, with the water-g...
Article
A number of fluidized bed reactor processes operating at high temperature require that solid particles be circulated back and forth between two reactor vessels. Since the circulation rate strongly affects mass and energy balances, and therefore greatly influences hydrodynamics and performance of the system, a reliable technique for its accurate mea...
Article
Full-text available
A simple kinetic model is developed for biomass gasification in a bubbling fluidized bed (BFB) with steam as the fluidizing gas. The biomass pyrolysis is described by a two-step kinetic model in which the primary pyrolysis is modeled by three parallel first-order reactions producing non-condensable gas, tar (bio-oil) and char, and the secondary pyr...
Article
Layer inversion in gas-liquid-solid fluidized beds with binary solids was examined in a semi-acrylic column of 1.8m height and 0.21m inner diameter. Binary solid combinations were composed of polymer beads (PB, d p=3.3mm, ρ s=1,280kg/m3) and glass beads (GB, d p=0.385mm, ρ s=2500kg/m3). Five volumetric ratios (PB:GB=0.67:0.33, 0.6:0.4, 0.5:0.5, 0.4...
Article
We present the results from a series of jet-attrition experiments performed using a standard ASTM device (ASTM D5757-00) on naturally occurring ash-sized (< 2 mm) pumice, a product of explosive volcanic eruption comprising highly porous silicate glass. We investigate the effect of both feed grain size and attrition duration on the production of fin...
Article
Polybrominated diphenyl ethers (PBDEs) are still present in sewage sludge and sludge-amended soil, even though commercial PBDEs were prohibited or voluntarily phased out several years ago. In this study, levels and compositional profiles of seven major PBDE congeners in sludge are assessed in relation to their usage patterns in commercial products,...
Article
Existing methods of predicting entrainment from gas-fluidized beds, based exclusively on hydrodynamic variables and mechanisms, show extremely wide discrepancies in predictions and no correlation that can accurately predict entrainment. Based on simultaneous measurement of electrostatic charges in the freeboard region and entrainment, it is shown t...
Article
Conductive and non-conductive fine powders were entrained by air at atmospheric temperature and pressure in a fluidization column of diameter 0.15 m made of stainless steel. Under equivalent operating conditions, entrainment of the conductive particles was markedly higher than for non-conductive species. This finding cannot be explained by hydrodyn...
Article
A user-defined solver integrating the solid-gas surface reactions and the multi-phase particle-in-cell (MP-PIC) approach is built based on the OpenFOAM software. The solver is tested against experiments. Then, biomass-steam gasification in a dual fluidized bed (DFB) gasifier is preliminarily predicted. It is found that the predictions agree well wi...
Article
A correlation has been proposed for predicting local bed-to-surface heat transfer coefficients in conical spouted beds based on an experimental study conducted using beds made up of sand, sawdust, and their mixtures under various operating conditions, namely, different static bed heights and gas velocities over minimum spouting. A comparison of the...
Article
A comprehensive single particle model of biomass drying and pyrolysis is coupled with an ideal reactor model of a bubbling fluidized bed with nitrogen as the fluidizing gas. To predict biomass pyrolysis products yield and composition under steady-state operation, a two-step biomass pyrolysis kinetic mechanism is adopted with primary pyrolysis descr...
Article
A novel model is presented that incorporates the Arrhenius integral into one of the generalized extreme value (GEV) distributions to describe the pyrolysis of complex feedstocks. The model differs in structure from distributed activation energy models (DAEM), and its self-variable differs from Weibull mixture models. It is found that all first orde...
Article
A transportable fluidization column, operating under identical conditions at three different locations, was employed to compare three experimental solids flux measurement techniques for hydrodynamic characterization of gas-fluidized beds. This paper compares measurements of solids mass and momentum flux obtained by radioactive particle tracking at...
Article
Solids exchange between two adjacent chambers was studied in a dual-column slot-rectangular spouted bed with a suspended partition, a geometry potentially useful for scale-up. Solids transfer between the chambers was quantitatively evaluated by the Lacey mixing index and a solids exchange coefficient. Effects of partition position, superficial gas...
Article
Polychlorinated dibenzo-p-dioxins (PCDDs) are of global concern due to their persistence, bioaccumulation and toxicity. Although the fate of PCDDs in the environment is determined by their physical-chemical properties, such as aqueous solubility, vapor pressure, octanol/water-, air/water-, and octanol/water-partition coefficients, experimental prop...
Article
The Advanced Isoconversional (AIC) method involves minimization of a function which uses conversion data at a minimum of three heating rates to determine an activation energy ( ) at different values of conversion ( ). Reactions that can be described by a single model give an which is independent of , while reactions which are described by more than...