Effect Of Residence Time Research Articles

Green Synthesis of 3-Hydroxybutyraldehyde from Acetaldehyde Catalyzed by La-Ca-Modified MgO/Al2O3

3-hydroxybutyraldehyde (3-HBA) is mainly employed to synthesize 1,3-BDO (1,3-butanediol), which is one of the most important components in cosmetics moisturizers. In this study, a series of composite oxide catalysts were prepared by bringing alkaline earth metal Ca and rare earth metal La to the composite oxide MgO/Al2O3, which were made through the co-precipitation method. These catalysts were applied in the synthesis of 3-HBA through acetaldehyde (AcH) condensation. The structure, texture, and acidic properties of these catalysts were characterized using various characterization methods, and the effects of catalyst composition, reaction temperature, reaction pressure, and residence time on the conversion of AcH were investigated as well. The results showed that the introduction of Ca and La weakened the acidic property and enhanced the basic property, which favored the AcH condensation to synthesize 3-HBA. At a temperature of 20 °C, pressure of 200 kPa, and residence time of 70 min, 0.5%La-2.3%Ca-2MgO/Al2O3 exhibited a better catalytic activity, and the conversion of AcH reached 95.89%. The selectivity and yield of 3-HBA were 92.08% and 88.30%, respectively. The stability test indicated that the high AcH conversion could be maintained for 5 h.

Flow synthesis of PVP capped gold nanoparticles in capillary microreactor

Flow synthesis of ultrafine colloidal gold nanoparticles (AuNP) of size below 5 nm in a microreactor is reported. The gold precursor along with trisodium citrate and an additional stabilizing agent (PVP) are premixed and infused using a syringe pump into a PTFE microbore tube kept immersed inside a hot oil bath using a syringe pump. The synthesized AuNP are mostly spherical in shape. Systematic studies are conducted to investigate the effects of residence time, reaction temperature, citrate to gold ratio, presence of additional stabilizing agent and gas induced flow segmentation on the average particle size and polydispersity index. An increase in residence time is seen to reduce average particle size. Smaller sized and more monodispersed AuNP are seen to form at higher reduction temperature. An increase in citrate to gold ratio is seen to have an insignificant effect of average particle size and polydispersity index. Presence of PVP is seen to reduce average particle size and polydispersity index. Smaller and more monodispersed AuNP are seen to form when the single phase aqueous flow is segmented by gas infused through a separate syringe pump. A mechanistic picture of the synthesis process is proposed to explain the experimental trends.

Effects of flow on uranium speciation in soils impacted by acidic waste fluids

Radioactive acidic liquid waste is a common byproduct of uranium (U) and plutonium (Pu) enrichment and recycling processes whose accidental and planned release has led to a significant input of U into soils and sediments across the world, including at the U.S. DOE's Hanford site (WA, USA). Because of the particularly hazardous nature of U, it is important to predict its speciation when introduced into soils and sediments by acidic waste fluids. Of fundamental importance are the coupled effects of acid-driven mineral transformation and reactive transport on U speciation. To evaluate the effect of waste-fluid residence time and co-associated dissolved phosphate concentrations on U speciation in impacted soils and sediments, uncontaminated surface materials (from the Hanford Site) were reacted with U-containing synthetic acidic waste fluids (pH 2) amended with dissolved phosphate concentrations in both batch (no flow) and flow-through column systems for 7–365 days. By comparing dissolved U behavior and solid phase speciation as a function of flow regimen, we found that the availability of proton-promoted dissolution products (such as Si) to sequester U into uranyl silicates was dependent on waste fluid-sediment contact time as uranyl silicates were not detected in short contact time flow-through systems but were detected in no-flow, long contact time, reactors. Moreover, the dominance of uranyl phosphate as neoprecipitate U scavenger (principally in the form of meta-ankoleite) in phosphate amended systems confirmed the importance of phosphate amendments for an efficient sequestration of U in the soils and sediments. Overall, our experiments suggest that the formation of uranyl silicates in soils impacted by acidic waste fluids is likely to be limited unless reaction products are allowed to accumulate in soil pores, highlighting the importance of investigating soil U speciation in flow-through, transport-driven systems as opposed to no-flow, batch systems. This study provides insights into uranium speciation and its potential changes under acidic conditions for better prediction of risks and subsequent development of efficient remediation strategies.

Liquid-fed waste plastic pyrolysis pilot plant: Effect of reactor volume on product yields

A unique waste plastic pyrolysis pilot plant was used for fast pyrolysis (1–5 s vapor residence time) of HDPE at 600 °C. A dissolution pre-treatment step dissolved the high-density polyethylene (HDPE) in recycled pyrolysis wax to create a liquid feed to the pyrolysis reactor, avoiding clogging and bridging of the plastic particles that is common in alternative feeding strategies. Three different reactor volumes were tested to determine the effect of residence time on product distribution. Pyrolysis products were cooled through a series of two condenser to separate the products into three groups: a heavy, waxy product (> C15), a lighter liquid product (C6-C15), and a gaseous product (C1-C6). GC/MS analysis was used to characterize the composition of each product. Multiphysics modeling was conducted to estimate the residence time in the reactor and compare the pilot plant results to previously published micropyrolysis research. It was found that residence time had a significant effect on product distribution, with an increase from 1 to 4.5 s of residence time causing a 9 wt% drop in wax (C20-C30) production and a 11 wt% increase in light oil (C5-C10) production. The trends for product distribution as a function of residence time were found to be consistent between both the pilot plant and micropyrolysis systems, demonstrating that the pilot plant system can be “tuned” to produce the desired pyrolysis product.

Experimental and Theoretical Studies on Water-Added Thermal Processing of Model Biosyngas for Improving Hydrogen Production and Restraining Soot Formation

The upgrading of biosyngas to convert methane into syngas is a necessary step for hydrogen production from biomass. However, this process is highly energy-demanding. In this study, a model biosyngas containing H2, CH4, CO, and CO2 were thermally treated between 1200 and 1500 °C. The gas mixture, comprised of H2 (33 vol %), CH4 (12 vol %), CO (28 vol %), CO2 (25 vol %), and He (2 vol %), was diluted with argon and the effect of reaction temperature (1200–1500 °C), water addition (0–44.3 mol %), and residence time (23, 46, and 76 μs in corresponding to flow rates of 1500, 2500, and 5000 mL/min at normal temperature and pressure, respectively) were studied. A possible reaction scheme for the upgrading of the model gas is proposed based on the kinetic simulation with CHEMKIN. The main reaction pathways involve dry reforming of methane and reverse water-gas shift (WGS) reactions. The kinetic simulation explained the finding that CO production was negatively influenced by the water content via the WGS reaction. The main side reaction is the methane pyrolysis reaction which causes the formation of carbon. The carbon formed in the reforming was characterized by SEM and Raman spectroscopy. SiO2 needle-like microdomains are observed at the top of the reactor heating zone, while the central part of the heating zone was covered by carbon with a disordered, amorphous, low-density soot structure. It is proposed that the SiO2 species formed by the chemical reaction between the reactor wall material and the reactants act as a support to anchor the carbon formed.

Effect of process variables on producing biocoals by hydrothermal carbonisation of pine Kraft lignin at low temperatures

Lignin from pulping is recovered in a wet form, making it ideal for hydrothermal carbonisation (HTC). This study investigates the effects of temperature (200–280 °C), residence time (1–6 h), and water to biomass mass ratio (2:1–6:1) on the composition of the resultant biocoal and the extent of alkaline and alkaline metal removal during HTC of pine Kraft lignin (PKL). Consistent with studies on other biomass materials, temperature exhibited the most significant effect on biocoal yield and properties, followed by residence time showing a marginal effect and varying the water to lignin mass only affecting alkaline and alkaline earth metals removal. Biocoal yields were in the range of 76–95 % (80–97 % on a carbon basis) and, compositionally, the biocoal obtained corresponded to sub-bituminous (220–260 °C) and high volatile bituminous coals (280 °C). Gas yields are low with the gas comprising mainly CO2 (98 v/v). The optimum temperature, time and biomass to water ratio for alkaline and alkaline earth metals removal was 260 °C, 3 h and 5:1 under which 93–95 % for sodium (Na) and potassium (K) and 75–80 % for magnesium (Mg) and calcium (Ca) removal were achieved. Solid-state 13C Nuclear Magnetic Resonance (NMR) revealed that during HTC, the oxygen-containing bonds of esters, ethers, and carboxylic groups were dissociated to produce lower-molecular weight including phenolic compounds dissolved in the process water. These findings have shown that the HTC is a promising alternative thermochemical route for coalification of wet PKL to a low ash coal-like fuel similar to sub-bituminous coal in rank that has potential applications for carbonisation.

Avermectin Toxicity to Benthic Invertebrates is Modified by Sediment Organic Carbon and Chemical Residence Time.

Chemicals used in sea lice management strategies in salmonid aquaculture include the avermectin class of compounds that can accumulate and persist in the sediments underneath salmon farms and directly impact nontarget benthic fauna. The effects of sediment organic carbon content and chemical residence time (CRT) on the lethal and sublethal toxicity of emamectin benzoate (EB; formulation: Slice®) and ivermectin (purified) and a combination of both were examined in two benthic invertebrates, the amphipod Eohaustorius estuarius and the polychaete Neanthes virens. In both species, increased sediment organic carbon content significantly reduced lethal toxicity, a modulation that was more pronounced for ivermectin and combination exposures. At a CRT of 4 months, lethal toxicity was reduced in E. estuarius but was unaffected in N. virens. Sublethal toxicity in N. virens (burrowing behavior) was modulated by sediment organic carbon and CRT in a similar manner to the trend in lethal toxicity. Inconsistencies in behavior (phototaxis) in E. estuarius made conclusions regarding toxicity modification by sediment organic carbon or CRT inconclusive. Our results indicate that environmental factors including sediment organic carbon content and the time compounds reside in sediments are important modifiers of chemotherapeutant toxicity in nontarget benthic species and should be considered when regulatory decisions regarding their use are made.Environ Toxicol Chem 2022;41:1918-1936. © 2022 SETAC.

Green synthesis optimization of graphene quantum dots by Doehlert design for dye photodegradation application

In this work, graphene quantum dots (GQDs) were synthesized by hydrothermal carbonization (HTC) of brewer’s spent grains. Doehlert matrix design was used to evaluate the effects of temperature and residence time on the GQDs’ properties, including their photocatalytic activity, totaling 9 experiments. Methyl orange (MO) was used as a model molecule for the photodegradation assays. The GQDs presented pH values smaller than 3.13, high electric conductivity (1.0–3.0 mS cm−1) and positive Zeta Potential values. The GQDs sample, when excited by UV light at 365 nm, emitted a blue color, confirming their self-doping with nitrogen. Hexagonal rings in zigzag edge structures were observed using Transmission Electron Microscopy. The GQDs presented quantum yields ranging from 0.3 % to 4.9 %. The GQDs produced at 150 °C for 14 h presented the best photocatalytic performance. The photodegradation of the MO occurred by a first-order mechanism, which comprises two stages. The stage 1 is attributed to the adsorption of MO by the GQDs and stage 2 is attributed to the degradation of the MO by eBC− and/or O2- radicals. Finally, it can be concluded that GQDs with photocatalytic activity were produced by green synthesis, collaborating for a circular and sustainable dynamic in industrial processes.

Syngas production from two-step CO2 gasification of low rank coal in an entrained flow reactor

Using CO2 as feedstock for syngas production is one hot topic in the field of clean energy due to the concern of global warming. Hence, two-step gasification (pyrolysis first and then subsequent char gasification) behaviour using CO2 as reactant was investigated under entrained flow conditions for one Inner Mongolia lignite and two Victorian brown coals (Maddingely and Morwell). The effects of CO2 concentration (5–30% CO2) and residence time(0–23 s) were assessed in the low temperature ranges of 700–1000 °C. High temperature improved H2 and CO yield in entrained flow pyrolysis. The higher CO2 concentration and longer residence time enhanced gasification syngas yield and carbon conversion. Three coal chars required around 23 s of residence time for 100% conversion under 20% CO2 and 1000 °C. It indicated that entrained flow gasification of the three chars was preferably performed above 1000 °C for industrial applications. Fe-rich Victorian brown coal achieved better pyrolysis performance than Inner Mongolia lignite because of the inherent catalytic effect of Fe oxides in coal. Morwell coal char achieved the best char-CO2 gasification performance due to higher gasification reactivity and better pore structure. This study provides essential information for the optimization of entrained flow gasifiers toward syngas production using CO2 as feedstock.

Bacterial colonisation dynamics of household plastics in a coastal environment

Accumulation of plastics in the marine environment has widespread detrimental consequences for ecosystems and wildlife. Marine plastics are rapidly colonised by a wide diversity of bacteria, including human pathogens, posing potential risks to health. Here, we investigate the effect of polymer type, residence time and estuarine location on bacterial colonisation of common household plastics, including pathogenic bacteria. We submerged five main household plastic types: low-density PE (LDPE), high-density PE (HDPE), polypropylene (PP), polyvinyl chloride (PVC) and polyethylene terephthalate (PET) at an estuarine site in Cornwall (U.K.) and tracked bacterial colonisation dynamics. Using both culture-dependent and culture-independent approaches, we found that bacteria rapidly colonised plastics irrespective of polymer type, reaching culturable densities of up to 1000 cells cm3 after 7 weeks. Community composition of the biofilms changed over time, but not among polymer types. The presence of pathogenic bacteria, quantified using the insect model Galleria mellonella, increased dramatically over a five-week period, with Galleria mortality increasing from 4% in week one to 65% in week five. No consistent differences in virulence were observed between polymer types. Pathogens isolated from plastic biofilms using Galleria enrichment included Serratia and Enterococcus species and they harboured a wide range of antimicrobial resistance genes. Our findings show that plastics in coastal waters are rapidly colonised by a wide diversity of bacteria independent of polymer type. Further, our results show that marine plastic biofilms become increasingly associated with virulent bacteria over time.

Hydrothermal liquefaction of municipal sludge: Coupling effects of temperature and time on nitrogen migration

Biocrude derived from hydrothermal liquefaction of municipal sludge has a high nitrogen content, which limits its direct use. This work explored coupling effects of reaction temperature and residence time on N transformation during hydrothermal liquefaction of municipal sludge. The results showed that 350 ℃ and 40 min were the optimal conditions, which led to the highest biocrude yield, HHV, energy recovery, and N removal efficiency after hydrothermal liquefaction of municipal sludge within 200–350 ℃ for 10–50 min. More than 60 wt% N in municipal sludge was distributed in the aqueous phase and NH4+ was the richest substance after hydrothermal liquefaction. Also, N transformation pathways were clarified by correlating the effects of reaction temperature and residence time on N distribution.

Nitrogen-rich soybean protein isolate derived “Self-Doping” carbon nano-onions for luminescence properties

Carbon nano-onions (CNOs) were successfully obtained for the first time through a simple one-pot Microwave hydrothermal carbonization (MHTC) method at low temperature by using biomass macromolecules as the raw materials. The effects of different reaction temperatures and residence times on the characteristics and yield of CNOs were studied. High-resolution transmission electron microscopy (HRTEM) images reveal CNOs with a regular concentric carbon shell structure with 10–20 layers, obvious crystal characteristics, and the lattice spacing of 0.34 nm. X-ray photoelectron spectroscopy and photoluminescence spectroscopy were applied to reveal the effects of different nitrogen forms and hybrid structures of carbon on the fluorescence properties of CNOs. Results showed that reaction temperature affected the structure of CNOs mainly by regulating the degree of carbonization, and residence time mainly affected the aromatization of CNOs. In addition, nitrogen self-doping CNOs prepared at low temperature also have good fluorescence performance. Most strikingly, the stable blue light emission by nitrogen self-doping CNOs could be the combination of the fluorescence of the carbon shell sp2 structure and that of surface functional groups. Taking advantage of the above unique fluorescent behavior, CNOs are prepared as fluorescent anticounterfeiting printing to achieve data encryption and decryption.

Release characteristics of alkali and alkaline earth metals in nascent char during rapid pyrolysis

The release law of alkali and alkaline earth metals (AAEMs) during coal pyrolysis is crucial for controlling scaling, corrosion and slagging in the utilization of high AAEMs coal. To approximate entrained-flow bed gasification process, a free-falling reactor was used for coal pyrolysis to study the release characteristics of AAEMs in nascent char. Effects of pyrolysis temperature, residence time and atmosphere were investigated. The cumulative release of Na, Ca and Mg at 1100 °C was 68.0%, 47.5% and 69.8%, respectively. As pyrolysis temperature increased from 900 °C to 1100 °C, the release of Na, Ca and Mg increased by 7.0 %, 3.5% and 5.3%, respectively. The cumulative release of AAEMs increased with the pyrolysis residence time, but the release rate decreased significantly in middle and late stages. The promoted thermal decomposition of functional groups by CO2 resulted in a lower char yield. CO2 promoted Na release in early stage and Ca and Mg release in late stage. Furthermore, release of AAEMs was associated with char structure evolution in rapid pyrolysis. The presence of CO2, high temperature and prolonged residence time led to enhanced particle fragmentation, increased surface cracks, and intensified thermal decomposition of functional groups, resulting in the migration of AAEMs in carbon matrix to char surface and the release of AAEMs organically bound to carbon matrix.

Annual water residence time effects on thermal structure: A potential lake restoration measure?

Innovative methods to combat internal loading issues in eutrophic lakes are urgently needed to speed recovery and restore systems within legislative deadlines. In stratifying lakes, internal phosphorus loading is particularly problematic during the summer stratified period when anoxia persists in the hypolimnion, promoting phosphorus release from the sediment. A novel method to inhibit stratification by reducing residence times is proposed as a way of controlling the length of the hypolimnetic anoxic period, thus reducing the loading of nutrients from the sediments into the water column. However, residence time effects on stratification length in natural lakes are not well understood. We used a systematic modelling approach to investigate the viability of changes to annual water residence time in affecting lake stratification and thermal dynamics in Elterwater, a small stratifying eutrophic lake in the northwest of England. We found that reducing annual water residence times shortened and weakened summer stratification. Based on finer-scale dynamics of lake heat fluxes and water column stability we propose seasonal or sub-seasonal management of water residence time is needed for the method to be most effective at reducing stratification as a means of controlling internal nutrient loading.

Sophisticated interplay of operating conditions governs flow field transition and optimal conversion inside tangentially fired gasifiers

A computational model is developed to simulate reacting environment inside the pilot-scale, tangentially-fired, Mitsubishi Heavy Industry entrained-flow coal gasifier. Using this comprehensive model, the impact of three operating parameters, namely, swirl number (SN), reactor pressure and mass throughput on the gasifier flow field and coal gasification process is investigated. We demonstrate that for given values of any two of these parameters, it requires a threshold value of the third parameter to form the central recirculation zone (CRZ), the absence of which lowers char conversion. Therefore, a modified SN incorporating the combined effect of conventional SN, reactor pressure and mass throughput on the onset of CRZ formation is proposed for tangentially-fired gasifiers. Furthermore, the impact of variation in reactor pressure and mass throughput on char conversion is shown to be mediated through the corresponding change in particle residence time and pressure effect on kinetics. The results demonstrate that the operating parameters interact in a complex state space that governs the gasifier flow physics and optimal operation.

Conversion of Waste Corn Biomass to Activated Bio-Char for Applications in Wastewater Treatment

This study proposes the conversion of waste corn grains contaminated by deoxynivalenol (also known as vomitoxin), a mycotoxin produced by plant pathogens, into a value-added product. Batches of 500 g of contaminated corn grains were pyrolyzed in a batch reactor by thermal treatment at temperatures up to 500°C with a 15°C/min heating rate and generating condensable vapors, gases and solid bio-char. The bio-char produced was subsequently activated in a furnace at 900°C, using CO2 as an activation agent, at different residence times. The effect of activation residence time on the characteristics of the activated bio-char, varying it from 0.5 to 3 h, was investigated. Characterization tests included BET surface area, SEM, TG-FTIR, pH, and XRD on both bio-char and activated bio-char. BET results illustrated a significant increase of the surface area from 63 to 419 m2g−1 and pore volume from 0.04 to 0.23 cm3g−1 by increasing the activation time from 0.5 to 3 h. SEM images visually confirmed a considerable increase in pore development. The pH significantly increased from 6 to 10 after activation, due to the elimination of acidic functional groups. The proximate analysis showed the stable carbon of the activated char reaching approximately 90 wt%, making it promising for catalyst/adsorbent applications. The adsorption performance of activated bio-char was tested by utilizing three different model molecules with different characteristics: methylene blue, methyl orange, and ibuprofen. Among all activated bio-char samples, activated bio-char with 3 h activation time showed the highest adsorption capacity, with a total adsorption (25 mg/g of activated bio-char) of methylene blue after 5 min. The results showed that the adsorption capacity of the activated bio-char was similar to that of valuable commercial activated carbon.

Modeling Study of the Slag Behaviors Based on Temperature-Time-Viscosity of Crystalline Slag in an Entrained-Flow Gasifier.

The crystal growth process has an important influence on the viscosity of the slag, which affects the characteristics of the slag layer on the wall of the gasifier. The slag flow and heat transfer model based on temperature–time–viscosity of crystalline slag were established, to predict the slag behaviors and protect gasifier. The results showed the overall viscosity of the slag after considering the residence time effect was higher than that when using the measured viscosity–temperature curve value. The liquid slag thickness, solid slag thickness, and residence time increased after the slag viscosity amendment, while the slag flow velocity and heat flux density decreased. Moreover, several types of crystallized slag were constructed to study the effects of crystal morphology and degree of crystallization difficulty on slag behaviors. The result indicated that the difficulty and crystal morphology of the slag crystallization cannot be ignored when using crystallized slag in gasification.

Supercritical water gasification of lignocellulosic biomass: Development of a general kinetic model for prediction of gas yield

• A general kinetic model of biomass supercritical water gasification was developed. • The kinetic model was validated successfully based on results from real biomass. • Temperature played the most important role in producing gaseous species. • The effect of residence time on gas formation was found to be minor. • SCWG of lignin produced the highest yield of hydrogen. Supercritical water gasification (SCWG) utilizes water as the reaction medium to convert biomass into a mixture of gases (i.e., H 2 , CO 2 , CO, CH 4 , and other short-chain hydrocarbons) at typical operating temperature ≥ 400 °C and pressure ≥ 23 MPa. Understanding kinetics of SCWG processes is critically important for future development and scale-up application of the SCWG technology. Thus, this study aimed to develop a general kinetic model to predict the yields of gases from SCWG of various lignocellulosic feedstocks with varying contents of cellulose, hemicellulose and lignin. The model was established based on the experimental results from K 2 CO 3 -catalyzed SCWG of various biomass model compounds including cellulose, xylan and lignin at 450–550 °C for 10–50 min, followed by validation of the model using the experimental data obtained from SCWG of real biomass (i.e., corn stalk and pinewood) under same reaction conditions. The validation results showed that the general kinetic model developed could accurately predict the yields of gases from real biomass SCWG and the quantitative influences of temperature and residence time on the gas yield in biomass SCWG. Additionally, the kinetic model has been validated other SCWG data in the literature obtained with various facilities and different lignocellulosic biomass feedstocks. The development of the general kinetic model provides an applicable way to assess the potential of SCWG of various lignocellulosic biomass feedstocks for producing combustible gases at various conditions.

Experimental Investigation on the Pore Structure Evolution of Coal in Underground Coal Gasification Process

Underground coal gasification (UCG) has been shown to be a promising method for deep coal resources. A series of complicated chemical reactions can induce a considerable change in the pore structure of coal and thus promote the UCG process in turn. Currently, most studies on the effect of elevated temperature on the pore structure of coal were not involved in an air atmosphere, bringing a series of difficulties to understanding the pore structure evolution of gasified coal in the UCG process. The objective of this work was to investigate the pore structure evolution of coal heated in nitrogen and air atmospheres at elevated temperatures. Thermogravimetry tests were first conducted to gasify coal samples, and then, the method scanning electron microscopy was used to observe the microscopic morphology of the pore structure. Besides, the effect of final temperature, atmosphere, pressure, and residence time on the thermal dynamics of coal at elevated temperatures was comprehensively discussed. Results indicated that the temperature range of a heating process of coal can be classified into three stages, 25–320 °C, 320–750 °C, and 750–1000 °C. For the three temperature ranges, drying, primary pyrolysis, and secondary pyrolysis can dominate, respectively, under a nitrogen atmosphere, while the combustion and gasification process will prevail at a high temperature under an air atmosphere. Because of mass loss, the coal was becoming porous during the heating process. Compared with the intact structure of coal when the temperature is lower than 300 °C, the pore space can interconnect under moderate-temperature conditions (500 °C) like a honeycomb, and then, only an ash framework remained under a higher-temperature condition (700 °C) under an air atmosphere. In comparison, the coal heated in a nitrogen atmosphere can gradually turn into a porous char. This investigation can provide some new insights into the pore structure evolution of gasified coal and contribute to the mechanisms of a UCG process.

Torrefaction of walnut oil processing wastes by superheated steam: Effects on products characteristics

Walnut oil production waste (WOPW) is a by-product of walnut oil processing. The organic waste is rich in holocellulose and lignin, showing good potential to be converted by thermal process to valuable products. Superheated steam (SHS) torrefaction is a recently proposed thermal process enabling fast and unformal biomass heating, resulting in high-quality solid products as direct fuel. The potential of SHS to torrefy lipids and proteins (being rich in WOPW) is attractive for broader application of SHS torrefaction to upgrade more biomass wastes. SHS torrefaction was studied in this work to upgrade WOPW for solid products with different reaction temperatures (200, 250, 300 °C) and residence times (20, 40, 60 min). The lowest weight yield was 43.64 wt% under the severest treatment of 300 °C and 60 min, accompanied with the highest energy enhancement of 1.34 (reaching HHV of 27.03 MJ/kg). Response surface method is employed to reveal the effects of temperature and residence time. Residence time of 40 min under 300 °C was supposed to be an ideal condition to upgrade WOPW with HHV of 26.68 MJ/kg and in the range of coal from Van Krevelen diagram. Combustion indices (e.g., fuel ratio, combustion index, and volatile ignitability) indicated that the aforementioned torrefied WOPW had favourable properties as co-firing material. On the other hand, combustion behaviours analysis demonstrated that SHS torrefied WOPW could perform well as direct fuel. Aqueous effluent was also condensed and analyzed, where products from lipids and proteins were massively presented, giving an insight into the decomposition of those two constitutes undergoing SHS torrefaction.