Thermal cracking processes convert larger molecules into smaller, more valuable products, without a catalyst, allowing for transforming residual oils or waste plastics into useful compounds. Fluid coking, a thermal cracking process utilizing a fluidized bed of hot particles, processes approximately 1 million barrels of residual oil daily. This study aims to understand the formation and breakage of wet agglomerates in fluidized beds, which are known to impact the efficiency of thermal cracking by promoting coke formation and fouling. A model is proposed to predict wet agglomerate formation, drying, and breakage. Experiments in a scaled-down cold model of the reactor provided data to validate the model. The study investigated the effects of spray nozzle penetration and the addition of a baffle on agglomerate behaviour. Results indicate that increased nozzle penetration reduces wet agglomerate formation, and adding a baffle increases agglomerate drying time and promotes breakage, reducing the amount of liquid reaching the reactor outlet. The combined approach of optimizing nozzle penetration and adding a baffle significantly improves fluid coker operation by minimizing the detrimental impact of wet agglomerates.

Internal cyclones use diplegs to recycle solids to the dense fluidized bed in most industrial fluidized beds. Poor dipleg operation can greatly increase particle losses from cyclones. Experiments with a 0.6 m diameter column and large group A particles showed that at low gas velocities in the fluidized bed, gas slugs rose through the dipleg, causing the emission of solids pulses; this issue was resolved by adding an elbow termination at the bottom of the dipleg. At high gas velocities, the dipleg backed up. A new model showed that dipleg backup resulted from large pressure fluctuations in the fluidized bed near the bottom of the dipleg. Momentarily, the local bed pressure became higher than the pressure in the dipleg, and fluidized solids flowed from the bed into the dipleg. Consequently, the dipleg was modified: the dipleg diameter and height were increased, and aeration and an elbow termination were added to the dipleg.

Biochar, unwashed and washed with a solution of Triton and hydrogen peroxide, was wet drum granulated using molasses binder solutions. Unwashed biochar was very hydrophobic and granulation proceeded through forming liquid marbles and layering. Washing reduced the hydrophobicity of the biochar. The effectiveness of the wash depended on the biochar source; it significantly reduced the hydrophobicity of biochar from woodchips and moderately reduced the hydrophobicity of biochar from flower digestate. Therefore, washed biochar from woodchips was granulated using a hydrophilic mechanism, while washed biochar from digestate was granulated according to a combination mechanism of liquid marbles collapsing and then coalescing. The change in granulation mechanism produced stronger and denser granules with higher yields of granules in the 1–4 mm optimal size range. Washing and then granulating biochar created a product that could be further tailored for optimal soil amendment.

Fluid Coking is a pyrolytic process that converts heavy oils to lighter hydrocarbons with hot fluidized coke providing the required heat. This study measures liquid accumulation due to vapor saturation in a pilot-scale Fluid Coking Reactor and determines the impact of vapor saturation on liquid product yield and quality. The accumulated liquid due to vapor saturation is estimated by measuring the pressure drop of the hot filter through which hydrocarbon vapors leave the reactor; it can measure accumulated liquid of less than 1 % of the bed mass. Liquid accumulation can be reduced by increasing the bed temperature, reducing the reactor pressure, or decreasing the liquid feedrate. In addition, liquid accumulation is mitigated by the reaction of heavy accumulated liquid to lighter compounds.

Washing biochar modifies its properties for use as a soil amendment. The important biochar properties for use as a soil amendment are hydrophilicity, adsorption, and stability. Biochar was obtained with intermediate pyrolysis at 400 degrees C of three different feedstocks: woodchips, Bayview Flowers Digestate, and Storm Fisher Digestate biomass. A simple wash with an aqueous surfactant solution improved the properties of the biochar for soil amendment, with a non-ionic surfactant combined with oxidizing hydrogen peroxide being the most effective. The improved properties included the removal of tars and possible modification of surface properties that increased hydrophilicity and adsorption and decreased leaching of any hydrocarbons that could negatively impact the surroundings. As a result, the washed biochar will exhibit better water retention and a more hospitable environment for the growth of beneficial microorganisms. In addition, by making the biochar more hydrophilic, a wash will make its granulation easier, reducing dust emissions during its application and allowing its formulation with enhancement additives. Although many post-pyrolysis treatments of biochars have been investigated, the proposed wash is simple and effective, with beneficial advantages for downstream processing and application as a soil amendment.

Adsorbents for wastewater treatment were produced from industrially obtained hydrochars using pyrolysis, CO2, and steam activation. Both pyrolysis and CO2 activation were studied between 400 to 900 °C, with a holding time of 1 or 2 h. Steam activation was carried out between 600 to 900 °C for a holding time of 2 h. Pyrolysis, CO2, and steam activation yields were in the ranges of 44–72, 26–51, and 14–59 wt.

Liquid injection into a gas-solid fluidized bed has been applied in various industries, such as coating and granulation processes in pharmaceutical and food industries, reactor cooling in polyolefin production, fluid catalytic cracking, and fluid coking in the petroleum industry. A new experimental method has been successfully developed to monitor the vaporization rate of a liquid injected into a fluidized bed. In addition, it can be used to determine the mass of liquid accumulated in the bed at a steady state. With this new method, measurements have identified three phenomena that may increase the amount of liquid accumulated at steady state in a fluidized bed. (1) Gas mixing affects vaporization when the bed temperature is lower than the liquid boiling point. In liquid-rich regions of the bed, local vapour may build up, limiting the vaporization rate. Consequently, suitable emulsion to bubble gas transfer reduces the amount of accumulated liquid. (2) Solids mixing: hot particles from the rest of the bed must mix with the wetted particles to provide enough heat for vaporization. Good solids mixing reduces the amount of accumulated liquid. (3) Wet agglomerates formation: liquid trapped within wet agglomerates takes much longer to vaporize. The amount of accumulated liquid can be reduced by injecting the liquid in a well-agitated bed region, operating at a higher bed temperature, or increasing the flowrate of atomization gas.

Agglomerate formation is an issue in several industrial fluidized bed processes, such as fluidized coating, fluid coking, biomass combustion, biomass gasification, and silicon refining. Vigorous bubbling can help reduce agglomeration, but is not intense enough to break strong agglomerates. Moreover, increasing the fluidization velocity of the whole bed may have undesirable outcomes, such as increased elutriation. High-velocity gas jets will also attrit the bed particles. This paper focuses on using low-velocity (10-30 m/s) horizontal gas jets to break agglomerates in a fluidized bed. A gas jet cycles, and the shear from the emulsion solids displaced by the expanding jet cavity helps break agglomerates. Equipment configurations that provide a high fraction of broken agglomerates for a typical agglomerate will be effective for other agglomerates of various strengths. Agglomerate breakage can be enhanced by increasing the jet nozzle flowrate or the flow of gas bubbles into the jet cavity.

Many industrial fluidized bed processes use particles as small as possible, i.e., at the boundary between groups A and C. Two exceptions are polyethylene reactors and fluid cokers, where the particles are at the boundary between groups A and B and bubbles are larger. This paper presents a study of particle entrainment from a fluidized bed of coke particles operated at high gas velocity and using a large column to avoid slugging. The gas bubble velocity near the bed surface remained constant over a broad range of gas velocities, ranging from bubbling to turbulent fluidization. Measurements indicated that the TDH could be obtained from this bubble velocity. Particle agglomeration affects particle entrainment at lower gas velocities, as demonstrated by adding an antistatic additive to the bed particles. While several correlations provide reasonable estimates of the flux of particles entrained above the TDH, considering particle agglomeration improves the predicted flux.

The jiggled bed reactor (JBR) is a new multiphase laboratory-scale microreactor consisting of a sealed container attached to a piston that is rapidly moved up and down by a pneumatically powered actuator. Particles and fluids in the container are mixed by this up and down motion instead of mechanical agitators or a fluidizing gas. This alternating motion provides intense mixing of all phases (gas, liquid, or solid) and intense contact between phases. Small rods inside the solids bed are heated by induction, allowing for excellent control of bed temperature and heating rate. The JBR is inexpensive and easy to operate, and it has been applied to catalytic gasification of bio-oil, biomass pyrolysis, activated carbon production, high-pressure oil hydrogenation, and hydrocarbons adsorption. Experiments demonstrated that solids mixing depends on the reactor platform maximum accelerations during both up and down strokes. A minimum acceleration, 55 m(2)/s for the tested JBR, was required to achieve good solids mixing. A physical model was developed to predict the reactor platform motion and its maximum acceleration. It requires a few preliminary experiments (around 10) to obtain its four empirical parameters. The model can then determine how to adjust the actuator compressed air pressure or modify the equipment to eliminate performance bottlenecks.

Biochar is a valuable product of pyrolysis. A new rotating heater pyrolysis reactor (RHP) was developed to process a variety of biomass feedstocks of up to 30 L and produce biochar batches of several kilograms. The RHP design was simple, allowing for easy construction, low-cost operation, and low energy consumption. Biochar produced from softwood woodchip biomass in the RHP for 2-3 h was determined to have physical and chemical properties comparable to biochar produced from a conventional batch pyrolysis reactor at temperatures between 375-425 degrees C.

The fluidized bed has been widely applied in different industrial processes because of its inherent advantages like excellent heat and mass transfer and mixing. In the Fluid Coking TM process, wet agglomerates carry the unreacted liquid to the stripper, which causes fouling and decreases the efficiency. The cumulative distribution of the formation-to-stripper time for wet agglomerates or particles is a very vital factor in the performance of fluidized bed reactor. A novel method based on the Eulerian-Eulerian approach was applied in the bubbling fluidized bed to track the particle travel time. In addition, the effects of design parameters (gas distributors and baffles) and operating conditions (superficial gas velocity) on the particle travel time in a bubbling fluidized bed were investigated. The results show that the particle travel time can be increased by either a baffle with a fluxtube or a modified gas distributor.

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GasbubbledistributionisconsideredoneofthemostcriticalfactorsaffectingtheIndustrialFluidCokingTMprocesssinceitinfluencestheformationofwetagglomeratesthatcausesfoulinginthestrippersection.Amulti-phaseEulerian-Euleriantwo-fluidmethod(TFM)coupledwiththekinetictheoryofthegranularflow(KTGF)wasusedtoinvestigatethehydrodynamicsofabubblingfluidizedbed;thegoalistoincreasetheflowofgasbubblesintothefirsthalfofthejetcavityformedwhenliquidissprayedintothefluidizedbed,thusreducingtheformationofwetagglomerates.Thenumericalsimulationsunderdifferentsuperficialgasvelocities,differentgasdistributorgeometries,anddifferentgasdistributorinclinedangleswerecarriedout.Theresultsshowedthatthepredictedbubbledistributionsattheinjectionlevelunderthelabandcommercialoperatingconditionsaresimilaralthoughtheparticlesandgasesaredifferentunderthosetwooperatingconditions.Moregasbubblescanbedirectedtothefirsthalfofthejetcavitybyeitherincreasingthegassuperficialvelocity(directingaround20%moregastothespecifiedarea)orusingtheproposednewgasdistributor(directingaround30%moregastothespecifiedarea).Theeffectoftheinletgasdistributorconfigurationonthebubbledistributionismuchmoresubstantialwhentheinclinedangleofthegasdistributorislarge. (c) 2021InstitutionofChemicalEngineers.PublishedbyElsevierB.V.Allrightsreserved.

Solids mixing plays an essential role in industrial processes. In this study, solids mixing in the bubbling fluidized bed were investigated numerically by the Eulerian-Eulerian method. The solids mixing behaviour in the bubbling fluidized bed was studied via comparison of the dispersion coefficient of particles (the mixing index). The study mainly compared the effects of design parameters (gas distributor and baffles) and operating conditions (superficial gas velocity) on the solids mixing in the bubbling fluidized bed. A baffle can improve the vertical dispersion coefficient in the upper section, while the inlet gas distributor configuration more affects the lower section. Combining both a baffle and a gas distributor does show noticeable improvement in the solids mixing.

Biochar is a carbon-rich material that is a co-product of the thermochemical conversion of biomass to liquid or gaseous products. A possible high-value application of biochar is the production of activated carbon. Biochar from biomass can be physically activated with a mild oxidant such as steam or carbon dioxide. A new model is proposed to describe the physical activation of pyrolytic biochar to activated carbon. The primary model assumption is that activation deepens but does not widen the pores. Measurements confirmed that the average pore diameter remained at about 1.9 nm. The new model successfully predicts the yield and specific surface area of activated carbon produced from olive residues. The pyrolysis conditions significantly impact the quality of the activated carbon. For example, biochar produced at higher heating rates contains more pores that, when cleared by physical activation with carbon dioxide, provide an activated carbon with a higher specific surface area, reaching about 1300 m2/g.

Conventional adsorbents for vapors are designed for high capacity and low-pressure drop, resulting in relatively slow vapor adsorption. Current adsorption measurement methods were, therefore, developed to characterize adsorption on a time scale of minutes. However, faster vapor adsorption is relevant for processes such as FLUID COKINGTM, where fouling within the cyclones can cause a shut-down. Hydrocarbon adsorption on hot coke particles could mitigate cyclone fouling. Therefore, a new measurement method was developed to characterize the fast adsorption of vapors on hot coke particles. It uses a vertically oscillating gas-solid contacting system to provide excellent particle-gas contact, well-mixed conditions, and well-controlled isothermal conditions. Equilibrium adsorption uptake of coke is more than an order of magnitude lower than for activated carbon. However, adsorption is much faster with coke, with an adsorption time constant of about 1 min. Significant adsorption of vapors on coke particles could, therefore, take place in Fluid Cokers.

In processes such as Fluid Coking (TM), agglomerate formation should be minimized since it reduces the yield of valuable products, and degrades operability because of the fouling of internals. An experimental model, consisting of an aqueous solution of gum arabic with a dye, has been successfully developed to simulate the formation of agglomerates in the Fluid Coking (TM) process, where bitumen is sprayed into a fluidized bed of coke particles The particles wetted by a spray could be predicted by assuming that all the particles in the wake of bubbles formed from the tip of the spray jet have been wetted by the injected liquid. The transfer of liquid from particles wetted with the spray to dry bed particles was relatively ineffective, as the number of wet particles increased by only 50%. With successive liquid injections, the proportion of the liquid trapped in agglomerates increases in latter injections: large agglomerates from earlier injections accumulate above the grid and are carried by gas bubbles into the spray jet cavity, where they seed fresh agglomerates. (C) 2020 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.