Rotating Drum Reactor Research Articles

Development of a hybrid bifunctional rotating drum electrode system for the enhanced oxidation of ciprofloxacin: An integrated photoelectrocatalysis and photo-electro-Fenton processes

Mismanaged antibiotics ending up in aquatic environment due to inadequate conventional treatment urges the need to develop powerful advanced oxidation techniques. In this study, hybrid bifunctional rotating drum reactor (BRDR) has been developed and its potency in enhancing the degradation of ciprofloxacin has been demonstrated. BRDR is a hybrid reactor that integrates – photoelectrocatalysis (PEC) and photo-electro-Fenton (PEF) processes with UVA irradiation. It consists of MoS2-TiO2-coated carbon cloth as anode and Ferrocene-functionalized graphene-coated graphite felt as cathode. BRDR system significantly improved the removal efficiency (99.9 %) as compared to individual efficiencies of PEC (71 %) and PEF (78.8 %) processes. An increase in electrode rotation speed significantly enhanced the removal without external aeration (0.059 min−1 for 60 rpm). Maximum removal rate was achieved at pH 3 (0.061 min−1) followed by 7 (0.040 min−1) and 9 (0.020 min−1). The increase in applied potential from open circuit voltage to 1.5 V improved the removal rate from 0.005 min−1 to 0.040 min−1. The mechanism of reactive oxygen species production in BRDR system is elaborated. BRDR is demonstrated to be cleaner treatment system which excludes the external chemical addition, aeration, and sludge formation.

Development and Test of a Rotating Drum Reactor for the Simultaneous Hydration and Carbonation of Dry Biomass Bottom Ash

Carbonation of biomass ash allows for the final storage of CO2 as solid carbonates and may therewith contribute to supply energy with net negative greenhouse gas emissions. Accelerating the reaction under ambient temperature and pressure requires presence of water as reaction space. Therefore, dry-discharged ashes need to be humidified. Here we developed and tested a rotating drum reactor integrating hydration and carbonation of biomass bottom ash (BBA). The bed motion was evaluated with moist quartz sand (QS) as a model material. In the BBA carbonation experiments, liquid-to-solid ratios (L/S) between 0.1 and 0.3 were adjusted with two-fluid nozzles. The reactant gas (10 vol% CO2) was fed either simultaneously with or subsequently to humidification. The CO2 uptake was determined gravimetrically as well as using a gas balance and was compared to results obtained under fixed-bed conditions. In the rotating drum, a favorable slumping motion of the QS was identified at a rotation rate of 7 rpm and a fill level of 20 vol%. Thus, BBA carbonation tests were carried out under these conditions yielding a CO2 uptake between 22 and 31 g/kg within 2 h. Uptake was highest at L/S 0.1 and lowest at L/S 0.3. These results indicate that the rotating drum reactor reduces the required moisture content compared to fixed-bed carbonation. The CO2 feeding mode (simultaneous or subsequent) had only a minor effect on the cumulative CO2 uptake but provided valuable insight into the heat production by hydration and carbonation of BBA in the rotating drum system.Graphical

Full-scale accelerated carbonation of waste incinerator bottom ash under continuous-feed conditions

Bottom ash (BA) is the dominant residue derived from the incineration of municipal solid waste or refuse-derived fuel (RDF). Costs for the disposal of the material chiefly depend on the leachability of salts and trace metals which may be cut by ageing the BA for several months to promote carbonation via uptake of carbon dioxide (CO2). Enhanced exposure to CO2 sources has been referred to as accelerated carbonation. Here we report on the successful implementation of the accelerated carbonation of BA in a continuously fed full-scale rotating drum reactor. The reactor was operated with the fine fraction (< 20 mm) of BA from an RDF incinerator and the exhaust of a combined heat and power unit was used as the reactant gas. The system was tested in 15 experiments and the process efficiency was addressed by maximizing the reactor loading and minimizing the BA residence time. Results confirmed that the reactor loading depended on the rotation-normalized mass flow rate of BA where the slope and intercept of the characteristic varied with the design of the reactor discharge and the use of mixing tools. According to leaching test results, BA residence times as low as 60 min were sufficient to render the carbonated BA a non-hazardous waste and convert it to a material suited for geotechnical applications. This outperforms previous laboratory findings and opens new perspectives for implementing the accelerated carbonation at incinerator sites.

Теплотехнические характеристики процесса пиролиза отработанных шин

A significant annual growth in the number of spent car tires creates a serious environmental problem and calls for the need to continue searching for efficient resource-saving methods of their recycling. There is a growing number of efforts aimed at studying waste tire thermochemical conversion processes, including their pyrolysis to obtain valuable products, including a solid fraction (coke residue), liquid hydrocarbon fraction (pyrolysis oil), and noncondensable gaseous fraction (pyrolysis gas). Commercial and pilot pyrolysis plants and reactors are reviewed. A rotating drum reactor, shaft and screw reactors are the most promising solutions for implementing a continuous process. The development of new resource-saving solutions for the pyrolysis of waste tire requires knowledge of the thermal characteristics of this process, including information on the material and heat flows in the pyrolysis reactor. The composition and thermal properties of waste tire, as well as specific outputs, composition and fuel properties of pyrolysis product material flows, including pyrolysis gas, pyrolysis oil and coke residue, are presented. Information on the pyrolysis plant or reactor heat balance structure is either absent or incomplete. Based on the data available in the literature, the heat balance of a commercial pyrolysis plant equipped with screw reactors characterized by a specific thermal destruction heat of 0.640 MJ/(kg of tires) is drawn up and studied. The numerical analysis results correlate with the data published for the commercial-grade plant. Information on the pyrolysis chamber heat balance structure is correct enough for use in engineering practice. It has been found that the specific heat consumption for the pyrolysis process is 2.269 MJ/(kg of tires). This value can be used in numerically analyzing pyrolysis plants equipped with other designs of pyrolysis reactors.

Assessment of high-solid mesophilic and thermophilic anaerobic digestion of mechanically-separated municipal solid waste

Mechanically-sorted organic fraction of municipal solid waste (OFMSW) was tested to determine its biogas and biomethane generation efficiency. Methane production capability of OFMSW was examined in biochemical methane potential (BMP) tests. The factors affecting the high-solid anaerobic digestion (AD) of feedstock were investigated in a series of long-term semi-continuous digestion tests performed at dry mesophilic and thermophilic conditions in a continuously rotating drum reactor with working volume of 0.013 m3.OFMSW presented low biogas and methane generation capacity due to its contained non-biodegradable components and the low proteins and starch proportions. Dry mesophilic AD allowed only a relatively limited fraction of OFMSW volatile solids to be consumed for biogas and methane production. Reducing particle size favoured utilization of higher proportions of the available digestible organic substances, and concurrently promoted biogas and biomethane generation rate. Stability of methane generation was also significantly improved by particle downsizing. Small particles compensated the limited mass transfer and restricted distribution of methane production intermediate metabolites caused by water absence in the dry AD system. Dry thermophilic AD converted sufficient quantity of OFMSWs biodegradable content. The average methane released from dry thermophilic AD (0.176 m3kgVS−1) was higher than that of dry mesophilic AD of fine particles (0.148 m3kgVS−1) and much higher than that of dry mesophilic AD of same grain size (0.114 m3kgVS−1). High temperature proved more suitable for anaerobically digesting mechanically-sorted OFMSW.

Thermal and Torrefaction Characteristics of a Small-Scale Rotating Drum Reactor

The small-scale rotating drum reactor (SS-RDR) was designed and constructed without using purge gas for the purpose of household application. The thermal and torrefaction characteristics of SS-RDR were studied and compared with other reactor types. It was found that the heat loss at the reactor wall and heat loss from exhaust gas of the SS-RDR were in the range of 6.3–12.4% and 27.9–42.8%, respectively. The increase of flue gas temperature resulted in the decrease of heat loss at the reactor wall and the increase of heat loss from exhaust gas. The heating rate of the SS-RDR was in the range of 7.3–21.4 °C/min. The higher heating value (HHV) ratio, mass yield, and energy yield ofthe SS-RDR were in the range of 1.2–1.6, 35.0–81.0%, and 56.2–96.5%, respectively. A comparison of torrefaction characteristics of various reactor types on HHV ratio-mass yield-iso-energy yield diagram indicated that the torrefaction characteristics of the SS-RDR were better than that of the rotating drum reactor with purge gas.

The mathematical description of process of heat exchange particles of oil shale and ash the coolant in the semi-coking conditions in a rotating drum reactor installation with solid heat carrier

The article deals with the modeling of heat transfer process in a drum reactor of a semi-coking unit of oil shale with a solid coolant between ash and shale particles in the conditions of constant separation of vapor-gas products. The dominant role of the convective component of the process is revealed and the curves of heating of shale particles are obtained taking into account the endothermic effect.It is established that the smallest fraction of fuel warms up within 30-60 seconds and further serves as a source of heat for other fractions. In the interval of 400-600 seconds, the heating of the largest fraction is completed. The further stay of the shale mixture in the reactor is caused by the lagging rate of the thermal decomposition process from heat exchange, and the temperature decrease by 20-250C by the presence of the endothermic effect of the decomposition of organic matter.

Continuous-feed carbonation of waste incinerator bottom ash in a rotating drum reactor

Carbonation is a key process in the aging of waste incinerator bottom ash (BA). The reaction with CO2 decreases the BA alkalinity and lowers the leachability of amphoteric trace metals. Passive ageing over several months is usually performed in intermittently mixed BA heaps. Here we aimed at accelerating the process in a rotating drum reactor continuously fed with the BA and the reactant gas (10 vol-% CO2, volumetric flow rate 60 L/min). In one test, the gas was heated and humidified. Since carbonation depends on the specific CO2-supply, experiments were conducted at varied BA residence time (60, 80, and 100 min). Residence time was calculated by mass balancing and confirmed by the breakthrough time of two tracers. Leachates and solid phase properties of the treated BA served to evaluate the carbonation performance. The residence time of BA could be adequately controlled by the reactor loading and feed rate. A residence time of 80 min was sufficient to reduce the BA leachability such as to comply with the German regulatory standards for non-hazardous waste, whereas the untreated BA was hazardous waste. Decreased alkalinity was indicated by lower leachate pH and Ca(OH)2 contents of the BA as compared to the input. Leachate concentrations of amphoteric trace metals (Pb, Zn, Cu) decreased by at least one order of magnitude while oxyanions became slightly more mobile upon carbonation. In view of relatively short residence times and stable process performance, the rotating drum reactor seems promising for a full-scale implementation of BA carbonation.

Photocatalytic degradation of aniline using an autonomous rotating drum reactor with both solar and UV-C artificial radiation

The aim of this work was to evaluate the performance of a novel self-autonomous reactor technology (capable of working with solar irradiation and artificial UV light) for water treatment using aniline as model compound. This new reactor design overcomes the problems of the external mass transfer effect and the accessibility to photons occurring in traditional reaction systems. The UV-light source is located inside the rotating quartz drums (where TiO2 is immobilized), allowing light to easily reach the water and the TiO2 surface. Several processes (UV, H2O2, Solar, TiO2, Solar/TiO2, Solar/TiO2/H2O2 and UV/Solar/H2O2/TiO2) were tested. The synergy between Solar/H2O2 and Solar/TiO2 processes was quantified to be 40.3% using the pseudo-first-order degradation rate.The apparent photonic efficiency, ζ, was also determined for evaluating light utilization. For the Solar/TiO2/H2O2 process, the efficiency was found to be practically constant (0.638–0.681%) when the film thickness is in the range of 1.67–3.87 μm. However, the efficiency increases up to 2.67% when artificial UV light was used in combination, confirming the efficient design of this installation. Thus, if needed, lamps can be switched on during cloudy days to improve the degradation rate of aniline and its mineralization. Under the optimal conditions selected for the Solar/TiO2/H2O2 process ([H2O2] = 250 mg/L; pH = 4, [TiO2] = 0.65–1.25 mg/cm2), 89.6% of aniline is degraded in 120 min. If the lamps are switched on, aniline is completely degraded in 10 min, reaching 85% of mineralization in 120 min. TiO2 was re-used during 5 reaction cycles without apparent loss in activity (<2%). Quantification of hydroxyl radicals and dissolved oxygen allows a chemical-based explanation of the process. Finally, the UV/Solar/TiO2/H2O2 process was found to have lower operation costs than other systems described in literature (0.67 €/m3).

Simultaneous Production of Amyloglucosidase and Exo-Polygalacturonase by Aspergillus niger in a Rotating Drum Reactor.

Simultaneous production of amyloglucosidase (AMG) and exo-polygalacturonase (exo-PG) was carried out by Aspergillus niger in substrate of defatted rice bran in a rotating drum bioreactor (RDB) and studied by a 31×22 factorial experimental design. Variables under study were A. niger strains (A. niger NRRL 3122 and A. niger t0005/007-2), types of inoculum (spore suspension and fermented bran), and types of inducer (starch, pectin, and a mix of both). Solid-state fermentation process (SSF) was conducted at 30°C under 60-vvm aeration for 96h in a pilot scale. Production of AMG and exo-PG was significantly affected by the fungal strain and the type of inoculum, but inducers did not trigger any significant effect, an evidence of the fact that these enzymes are constitutive. The maximum activity of exo-PG was 84Ugdm-1 whereas the maximum yield of AMG was 886.25Ugdm-1.

Experimental evaluation of two different types of reactors for CO2 removal from gaseous stream by bottom ash accelerated carbonation

Low methane content landfill gas may be enriched by removing carbon dioxide. An innovative process, based on carbon dioxide capture and storage by means of accelerated carbonation of bottom ash is proposed and studied for the above purpose. Within this research framework we devoted a preliminary research activity to investigate the possibility of improving the way the contact between bottom ash and landfill gas takes place: this is the scope of the work reported in this paper. Two different types of reactors – fixed bed and rotating drum – were designed and constructed for this purpose. The process was investigated at laboratory scale. As the aim of this phase was the comparison of the performances of the two different reactors, we used a pure stream of CO2 to preliminarily evaluate the reactor behaviors in the most favorable condition for the process (i.e. maximum CO2 partial pressure at ambient condition). With respect to the simple fixed bed reactor concept, some modifications were proposed, consisting of separating the ash bed in three layers. With the three layer configuration we would like to reduce the possibility for the gas to follow preferential paths through the ash bed. However, the results showed that the process performances are not significantly influenced by the multiple layer arrangement. As an alternative to the fixed bed reactor, the rotating drum concept was selected in order to provide continuous mixing of the solids. Two operating parameters were considered and varied during the tests: the filling ratio and the rotating speed. Better performances were observed for lower filling ratio while the rotating speed showed minor importance. Finally the performances of the two reactors were compared. The rotating drum reactor is able to provide improved carbon dioxide removal with respect to the fixed bed one, especially when the rotating reactor is operated at low filling ratio values and slow rotating speed values. Comparing the carbon dioxide specific removal obtained by using the rotating reactor (35–37g/kgBA), in the best operating conditions, with that measured for the fixed bed reactor (21–23g/kgBA), an increase of about 61–66% is observed.

Characterization, optimization, and scale-up of cellulases production by trichoderma reesei cbs 836.91 in solid-state fermentation using agro-industrial products

The application of cellulases in saccharification processes is restricted by its production cost. Consequently, new fungal strains able to elaborate higher cellulases titers and with special activity profiles are required to make the process economical. The aim of this investigation was to find a promising wild-type Trichoderma strain for cellulases production. The Trichoderma reesei strain 938 (CBS 836.91) was selected among twenty strains on the basis of cellulase-agar-plate screening. Evaluation of the selected strain on six solid substrates indicated the highest activities to be obtained from wheat bran. Statistical analyses of the experimental design indicated a significant effect of pH and moisture on the generation of endoglucanase (EGA) and filter-paper (FPA) activity. Furthermore, a central-composite design-based optimization revealed that pH values between 6.4 and 6.6 and moisture from 74 to 94% were optimal for cellulases production. Under these conditions, 8-10 IU gds(-1) of FPA and 15.6-17.8 IU gds(-1) of EGA were obtained. In addition, cultivation in a rotating-drum reactor under optimal conditions gave 8.2 IU gds(-1) FPA and 13.5 IU gds(-1) EGA. Biochemical characterization of T. reesei 938 cellulases indicated a substantially higher resistance to 4 mM Fe(+2) and a slightly greater tolerance to alkaline pH in comparison to Celluclast(®). These results suggest that T. reesei 938 could be a promising candidate for improved cellulases production through direct-evolution strategies.

Copper extraction from coarsely ground printed circuit boards using moderate thermophilic bacteria in a rotating-drum reactor

The current work reports on a new approach for copper bioleaching from Printed Circuit Board (PCB) by moderate thermophiles in a rotating-drum reactor. Initially leaching of PCB was carried out in shake flasks to assess the effects of particle size (−208μm+147μm), ferrous iron concentration (1.25–10.0g/L) and pH (1.5–2.5) on copper leaching using mesophile and moderate thermophile microorganisms. Only at a relatively low solid content (10.0g/L) complete copper extraction was achieved from the particle size investigated. Conversely, high copper extractions were possible from coarse-ground PCB (20mm-long) working with increased solids concentration (up to 25.0g/L). Because there was as the faster leaching kinetics at 50°C Sulfobacillus thermosulfidooxidans was selected for experiments in a rotating-drum reactor with the coarser-sized PCB sheets. Under optimal conditions, copper extraction reached 85%, in 8days and microscopic observations by SEM–EDS of the on non-leached and leached material suggested that metal dissolution from the internal layers was restricted by the fact that metal surface was not entirely available and accessible for the solution in the case of the 20mm-size sheets.

Comparison of Fe2+ oxidation by Acidithiobacillus ferrooxidans in rotating-drum and stirred-tank reactors

Fe2+ oxidation by Acidithiobacillus ferrooxidans (At. ferrooxidans) under different solid contents by adding inert Al2O3 powder was examined in rotating-drum and stirred-tank reactors. The results show that the bioactivity of At. ferrooxidans in the stirred-tank is higher than that in the rotating-drum in the absence of Al2O3 powder, but the biooxidation rate of Fe2+ decreases markedly from 0.23 g/(L·h) to 0.025 g/(L·h) with increasing the content of Al2O3 powder from 0 to 50% (mass fraction) in the stirred- tank probably due to the deactivation of At. ferrooxidans resulting from the collision and friction of solid particles. The increase in Al2O3 content has a little adverse effect on the bioactivity of At. ferrooxidans in the rotating-drum due to different mixing mechanisms of the two reactors. The biooxidation rate of Fe2+ in the rotating-drum is higher than that in the stirred-tank at the same content of Al2O3 powder, especially at high solid content. The higher bioactivity of At. ferrooxidans can be maintained for allowing high solid content in the rotating-drum reactor, but its application potential still needs to be verified further by the sulfide bioleaching for the property differences of Al2O3 powder and sulfide minerals.

Feasibility Study of Ethanol Production from Food Wastes by Consolidated Continuous Solid-State Fermentation

To save the cost and input energy for bioethanol production, a consolidated continuous solid-state fermentation (CCSSF) system composed of a rotating drum reactor, a humidifier and a condenser has been developed. In this research, the feasibility of using this system for production of ethanol from food wastes was carried out. The ethanol conversion of bread crust and rice grain (uncooked rice) as substrates reached up to 100.9% ± 5.1% and 108.0% ± 7.9% (against theoretical yield), respectively. Even for bread crust, a processed starchy material which contained lower carbohydrate content than rice grain, the amount of ethanol obtained in a unit of CCSSF per year was higher due to easy saccharification and fermentation. The salt contained in potato chips directly affected yeast activity resulting to low ethanol conversion (80.7% ± 4.7% against theoretical yield).

Arsenopyrite bioleaching by Acidithiobacillus ferrooxidans in a rotating-drum reactor

A rotating-drum reactor with a gas-sparger of microfiltration ceramic membrane was used for arsenopyrite bioleaching by Acidithiobacillus ferrooxidans. The gas mass transport performance could be improved by adjusting the aeration rate and drum rotation speed, and high bioactivity of bacterial strains could be maintained at high pulp densities. Arsenopyrite bioleaching showed that higher pulp density could be allowed in the rotating-drum reactor, which was favorable to the reactor used in the bioleaching of sulfide minerals.

Development of a Rotating Drum Reactor with a Novel Temperature Control System for Solid State Fermentation

Development of a Rotating Drum Reactor with a Novel Temperature Control System for Solid State Fermentation

TECHNICAL AND ECOLOGICAL ASPECTS OF SHALE OIL AND POWER COGENERATION

The most substantial feature of shale oil and power cogeneration is the technology that uses the high-temperature solid phase from the ash separator of a circulating fluidised-bed (CFB) boiler as the heat carrier in the rotating drum reactor in oil shale retorting equipment rather than high-temperature ash from a single-purpose built-in semi-coke burning furnace. Retort products generated in the rotating drum reactor are separated from semi-coke in the separator and canalised into the condensing and cleaning equipment. Semi-coke is transported into the CFB furnace. All co-products generated in this technological process, such as phenol water, drying agent containing oil shale particles etc., are defused in the furnace of the CFB boiler. The application of such technology makes it possible to minimise the dangerous waste of shale oil production and guarantee the maximum use of oil shale energy.

Ethanol production from biomass by repetitive solid-state fed-batch fermentation with continuous recovery of ethanol

To save cost and input energy for bioethanol production, a consolidated continuous solid-state fermentation system composed of a rotating drum reactor, a humidifier, and a condenser was developed. Biomass, saccharifying enzymes, yeast, and a minimum amount of water are introduced into the system. Ethanol produced by simultaneous saccharification and fermentation is continuously recovered as vapor from the headspace of the reactor, while the humidifier compensates for the water loss. From raw corn starch as a biomass model, 95 +/- 3, 226 +/- 9, 458 +/- 26, and 509 +/- 64 g l(-1) of ethanol solutions were recovered continuously when the ethanol content in reactor was controlled at 10-20, 30-50, 50-70 and 75-85 g kg-mixture(-1), respectively. The residue showed a lesser volume and higher solid content than that obtained by conventional liquid fermentation. The cost and energy for intensive waste water treatment are decreased, and the continuous fermentation enabled the sustainability of enzyme activity and yeast in the system.

Oxygen transfer to slurries treated in a rotating drum operated at atmospheric pressure

The objective of this work was to determine (1) the effect of rotational speed (N) and lifters on the oxygen transfer coefficient (k (L)) of a mineral solution and (2) the effect of solids concentration of a slurry soil-mineral solution on k (L), at a fixed value N (0.25 s(-1)); in both cases the treatment was carried out in an aerated rotating drum reactor (RDR) operated at atmospheric pressure. First, the k (L) for the mineral solution was in the range 6.38 x 10(-4)-7.69 x 10(-4) m s(-1), which was of the same order of magnitude as those calculated for closed rotating drums supplied with air flow. In general, k (L) of RDR implemented with lifters was superior or equal to that of RDR without lifters. For RDR implemented with lifters, k (L) increased with N in the range 6.65 x 10(-4)-10.51 x 10(-4) m s(-1), whereas k (L) of RDR without lifters first increased with N up to N = 0.102 s(-1), and decreased beyond this point. Second, regarding soil slurry experiments, an abrupt fall of k (L) (ca. 50%) at low values of the solid concentration (C (v)) and an asymptotic pattern at high C (v) were observed at N = 0.25 s(-1). These results suggest that mass transfer phenomena were commanded by the slurry properties and a semi-empirical equation of the form Sh = f(Re, Sc) seems to corroborate this finding.