The work herein describes a novel technique, a rotating packed bed (RPB) combined with a charged device, to remove fine particles from gas steam. Experiments were carried out to investigate the effects of different operating conditions, including the packing type, packing thickness, rotation speed, gas–liquid volumetric ratio, initial fine particle concentration, and voltage, on the removal efficiency of fine particles from a gas stream. Results show that total removal efficiencies of fine particles and particles with a size of less than 2.5 μm (PM2.5) can reach up to 99 and 96%, respectively, under the operating conditions of packing thickness of 60 mm, rotation speed of 1000 rpm, gas–liquid volumetric flow ratio of 400, voltage of 40 kV, and use of a fine metal gauze packing. In addition, a correlation to predict PM2.5 removal efficiency was established, and results show that the predicted values of outlet PM2.5 concentrations are in agreement with experimental data, with deviations of ±20%. This work demonstrates that the removal process of fine particles has a low pressure drop and higher removal efficiency of fine particles. Consequently, it provides a fast and efficient alternative approach for removal of fine particles from gas steam.

•Catalytic oxidative absorption of H2S from a simulated COG in a RPB was explored.•Na2CO3 solution doped with a commercial “888” catalyst was used as the absorbent.•Effect of operating conditions on the removal efficiency of H2S was studied.•RPB exhibited higher H2S removal efficiency than the compared packed column.The shortage of low-sulfur coking coal will bring about an increasingly high hydrogen sulfide (H2S) in the coke oven gas (COG) in the near future. This work investigated the removal of hydrogen sulfide (H2S) from a simulated coke oven gas (COG) by catalytic oxidative absorption in a rotating packed bed (RPB). Sodium carbonate (Na2CO3) solution doped with 20 mg L−1 of a commercial “888” catalyst was used as the absorbent. The removal efficiency of H2S was evaluated under various operating conditions including rotation speed of the RPB (N), liquid-gas ratio (L/G), inlet H2S concentration (cH2S,in), temperature (T) and Na2CO3 concentration (cNa2CO3) in an attempt to optimize the conditions. The results were validated by comparison with those of separate experiments conducted in a packed column comprising a high-efficiency laboratory packing of Dixon rings. The comparison results reveal that the RPB exhibited higher H2S removal efficiency than the packed column, indicating it as an efficient gas-liquid contactor with a greater potential to remove H2S from COG.

•Sulfonation of alkylbenzene using novel RPB reactor.•High alkylbenzene sulfonated ratio in RPB.•Modeling of mixing and reaction process in RPB.This article presents modeling and experimental study on the sulfonation of alkylbenzene to synthesize alkylbenzene sulfonate in a rotating packed bed (RPB) reactor. The effects of some important operating and reactor parameters, such as rotating speed of RPB reactor, liquid flow rate, SO3 molar concentration in sulfonating agent, reaction temperature, and packing thickness of RPB on the alkylbenzene sulfonated ratio were investigated. In addition, a coalescence-redispersion mathematical model was established to predict alkylbenzene sulfonated ratio in RPB, and the validity of the model was confirmed by the fact that most of the predicted alkylbenzene sulfonated ratio agreed well with the experimental data with a deviation within 12%. The experimental and numerical results showed that an improvement of the alkylbenzene sulfonation performance in RPB reactor could be achieved by optimizing the RPB rotating speed and total reactant liquid flow rate, decreasing the SO3 concentration in sulfonating agent and properly increasing the react temperature and RPB packing thickness.Download high-res image (102KB)Download full-size image

This study investigated the absorption performance of CO2 into a diethylenetriamine (DETA)-based solution containing piperazine (PZ) or 1-(2-aminoethyl)piperazine (AEPZ) as an activator in a packed column with Dixon rings. The effects of various operation conditions such as the activator concentration, gas flow rate, liquid flow rate, CO2 partial pressure, and solution temperature on overall gas-phase volumetric mass-transfer coefficient (KGav) were explored. Results indicate that the presence of PZ in DETA solution yields a better enhancement effect on KGav than AEPZ, and, thus, a combination of 5%PZ+25%DETA solution is expected to be a promising absorbent for CO2 absorption. The results further show that KGav increases with an increase in the liquid flow rate and a decrease in CO2 partial pressure and first increases and then decreases with an increase in solution temperature. On the other hand, the gas flow rate has an insignificant effect on KGav. A simplified empirical correlation for KGav as a function of the operation parameters has been proposed, and most of the calculated values are in agreement with the experimental data with a deviation within ±15%.

This article presents systematic investigations on the mass-transfer characteristics, including the overall gas-phase volumetric mass-transfer coefficient (KGa) and the height of mass-transfer unit (HTU), of the CO2 absorption process into a mixture of diethylenetriamine (DETA) and piperazine (PZ) solution in a rotating packed bed (RPB). The effects of operating conditions, including PZ concentration, rotation speed, liquid volumetric flow rate, gas volumetric flow rate, gas treatment capacity of packing, inlet CO2 mole fraction, temperature, CO2 loading of lean solution, and distributor specification on KGa and HTU in the RPB, were systematically studied. Also, a comparison of CO2 absorption performance between the packed column with Dixon rings packing and the RPB is presented. Results indicate that both KGa and HTU were significantly affected by rotation speed, liquid volumetric flow rate, gas volumetric flow rate, temperature, and lean CO2 loading while the PZ concentration, inlet CO2 mole fraction, and liquid distributor had minimal effect on KGa and HTU. It was noted that a RPB exhibits better mass-transfer performance compared to a packed column with Dixon rings packing.

CdTe-based quantum dots (QDs) with high photoluminescence quantum yields (PL QYs) were synthesized in a short time (less than 45 minutes). Mercaptosuccinic acid (MSA) was employed as a stabilizer and N2H4 as a growth promoter to accelerate the growth of CdTe and CdSexTe1−x QDs. Red-emitting CdTe QDs with a PL QY of 25% were obtained and the highest PL QY reached 55%. CdSexTe1−x QDs with emission peak positions of 518 nm to 750 nm were obtained. The rapid growth of QDs depends on the interaction between MSA and Cd2+, and N2H4 plays a key role in accelerating the growth to a certain level. Thus, the QD particle size can be controlled by manipulating N2H4 concentration in solution. A low N2H4 concentration seems feasible to obtain high-quality QDs.

The effects of erythorbic acid (EA) and ethanol on the aqueous formation of cadmium telluride (CdTe) quantum dots (QDs) were explored in this work. Without N2 protection, CdTe QDs were synthesized with cadmium chloride and sodium hydrogen telluride as the Cd source and Te source, respectively, together with EA and with 3-mercaptopropionic acid (MPA) as the co-passivating ligand. The experimental results indicated that the use of the oxygen scavenger, i.e., EA, was critical for the formation of the CdTe QDs with reasonably good optical properties. Including ethanol during the synthesis improved the photoluminescence intensity. To attain good optical properties, it is also important to tune experimental parameters such as pH, temperature, reaction time, molar ratio of MPA/Cd, and sodium borohydride dosage. The very reason that EA promoted formation of CdTe QDs is because of its reducibility and passivation on the QD surface. The present study suggests that the use of EA and ethanol could be a practical means to promote the photoluminescence of CdTe.

•Erythorbic acid (EA) was employed in aqueous synthesis of CdS quantum dots (QDs).•EA acted as an oxygen scavenger and passivating ligand in the synthesis.•EA enhanced the optical properties of CdS QDs and the mechanism was discussed.•This route offers an easy and green pathway for producing QDs with good dispersion.The effect of erythorbic acid (EA) on the aqueous formation of CdS quantum dots (QDs) at room temperature was explored in this work. Without N2 protection, CdS QDs were synthesized in water by a one-pot non-hot-injection approach at room temperature. The Cd and S sources were CdCl2 and Na2S, respectively, together with 3-mercapto-propionic acid (MPA) as the passivating ligand. The experimental results indicate that the use of the oxygen scavenger, i.e., EA, was critical for the formation of the CdS QDs with reasonably good optical properties, and it is also important to tune experimental parameters such as MPA-to-Cd molar ratios, pH, and reactant concentrations. The mechanism about the EA promoted formation of CdS QDs was discussed in terms of NMR, IR, in situ absorption, and photoemission studies. The very reason for the EA promoted formation of CdS QDs is due to its reducibility and passivation on the QD surface (particularly in alkaline environment). The present study suggests that the use of EA could be a practical means to enable the room-temperature formation of QDs in water.

•Nano-CaCO3 was synthesized in a microporous tube-in-tube microchannel reactor.•The reactor has a high throughput capacity.•The reactor exhibits excellent mass transfer and micromixing effect.•Nano-CaCO3 particles have an average size of 28 nm with narrow size distribution.In this work, nano-CaCO3 particles with tunable size have been synthesized via CO2/Ca(OH)2 precipitation reaction in a microporous tube-in-tube microchannel reactor (MTMCR) with a throughput capacity up to 400 L/h for CO2 and 76.14 L/h for liquid. The overall volumetric mass-transfer coefficient (KLa) of CO2 absorption into Ca(OH)2 slurry in the MTMCR has been deduced and analyzed. To control the particle size, the effect of operating conditions including initial Ca(OH)2 content, gas volumetric flow rate, liquid volumetric flow rate, micropore size, and annular channel width was investigated. The results indicated that the mass transfer in the MTMCR can be greatly enhanced in contrast with a stirred tank reactor, and the particle size can be well controlled by tuning the operating parameters. The nano-CaCO3 particles with an average size of 28 nm and a calcite crystal structure were synthesized, indicating that this process is promising for mass production of nanoparticles.Download full-size image

•A rotating packed bed combined with a stirred tank reactor (STR) was employed as a reactor for the synthesis reaction.•The effects of different operating conditions on heavy alkyl benzene sulfonate (HABS) content were investigated.This study presents the synthesis of heavy alkyl benzene sulfonate (HABS) via liquid–liquid reaction of heavy alkylbenzene (HAB) with dilute liquid sulfur trioxide (SO3) in a rotating packed bed (RPB) combined with a stirred tank reactor (STR). The effects of different operating conditions including high gravity level (G), total liquid flow rate (QL), SO3 concentration (ζ), SO3 dosage (φ), reaction temperature (T) and reaction time (θ) on HABS content (η) were investigated, and the results revealed that high HABS content of about 88% was achieved under the optimal operating conditions including G of 59, QL of 62.8 L h−1, ζ of 30%, φ of 1.1, T of 45 °C and θ of 4 min. The results indicated that the sulfonation reaction was basically achieved in the RPB of the combined reactor, and the time of the synthesis process was shortened.Schematic diagram of the experimental set-up for sulfonation of HAB &z.rtrif; 1-tank for HAB, 2-tank for sulfonating agent, 3-pump, 4-flow meter, 5-RPB reactor, 6-tank for products, 7-water bath temperature control system.Download high-res image (94KB)Download full-size image