Continuous Hydrothermal Reactor Research Articles

Modelling and numerical analysis on residence time distribution characteristics in continuous high-pressure hydrothermal reactor

Residence time distribution (RTD) is significant for reflecting fluid mixing and materials dispersion inside continuous high-pressure hydrothermal reactor. In this work, a model is proposed to precisely fit RTD data in continuous hydrothermal reactor, and the model parameters can be used to analyze the characteristics of RTD. A series of RTD data under different working conditions are obtained by numerical simulation and analyzed by the proposed model to investigate the effects of natural convection, momentum ratio and forced flow on RTD. It is found that appropriate natural convection and momentum ratio are beneficial to fluid mixing and materials dispersion. On the other hand, excessive natural convection and too high or too low branch inflow may lead to the extension of average residence time and materials delay or stagnation. Forced flow is negatively correlated with average residence time but has little influence on materials dispersion and delay.

Measurement, Modelling and Analysis of Residence Time Distribution Characteristics in a Continuous Hydrothermal Reactor

Measurement, Modelling and Analysis of Residence Time Distribution Characteristics in a Continuous Hydrothermal Reactor

Hydrolysis of Dimethyl Methylphosphonate (DMMP) in Hot-Compressed Water.

Dimethyl methylphosphonate (DMMP) is often used as a chemical surrogate for organophosphate nerve agents, as it exhibits similar physiochemical properties while having significantly lower toxicity. Continuous hydrolysis of DMMP in hot-compressed water is performed at temperatures from 200 to 300 °C, pressures of 20 and 30 MPa, and residence times from 30 to 80 s to evaluate the effects of pressure and temperature on reaction kinetics. DMMP hydrolysis is observed to follow pseudo-first-order reaction behavior, producing methylphosphonic acid and methanol as the only detectable reaction products. This is significant for the practical implementation of a continuous hydrothermal reactor for chemical warfare agent neutralization, as the process only yields stable, less-toxic compounds. Pressure has no discernible effect on the hydrolysis rate in compressed liquid water. Pseudo-first-order Arrhenius parameters are determined, with an activation energy of 90.17 ± 5.68 kJ/mol and a pre-exponential factor of 107.51±0.58 s-1.

Establishment and performance of a plug-flow continuous hydrothermal reactor for biocrude oil production

It is critical important for continuous production of biocrude oil and scale-up of hydrothermal liquefaction (HTL) technology. Pickering emulsion associated with solid (e.g. ash, char etc.) content is currently identified as a challenge for products recovery. Here, we investigated the continuous biocrude oil production from Spirulina sp., swine manure wastewater-fed Chlorella sp., and biogas wastewater-fed Chlorella sp. with quite different ash content ranging from 5.85% to 26.9%. The continuous reactions were evaluated at 300 °C with a flow rate of 45 mL·min−1 and a solid content of 18%. All the samples were converted into biocrude oil without obvious clogging issues. Subsequent analysis proves the feasibility of steady continuous HTL operation regarding the product yields, nutrients recovery, energy recovery as well as biocrude oil properties. The highest biocrude oil yield (42.3%, dw) was obtained with Spirulina sp. while the highest energy recovery (68.6%) and carbon recovery (59.7%) of biocrude oil were obtained from swine manure wastewater-fed Chlorella sp. Results reveal that higher ash content related to Pickering emulsion led to lower biocrude oil recovery rate. Further studies should focus on addressing the issue, especially for large-scale continuous HTL products separation system.

Production of xylose enriched hydrolysate from bioenergy sorghum and its conversion to β-carotene using an engineered Saccharomyces cerevisiae

A new bioprocess has been developed that allows for producing β-carotene from the xylose portion of bioenergy sorghum. Bioenergy sorghum was pretreated in a pilot-scale continuous hydrothermal reactor followed by disc refining. Xylose was extracted using low-severity dilute acid hydrolysis. A xylose yield of 64.9% (17.4 g/L) was obtained by hydrolyzing at 120 °C for 5 min with 2% sulfuric acid. The xylose-enriched syrup was separated and concentrated to either 32 g xylose/L (medium-concentrated hydrolysate, MCB) or 66 g xylose/L (high-concentrated hydrolysate, HCB). The non- (NCB), medium-, and high-concentrated xylose syrup were neutralized and fermented to β-carotene using Saccharomyces cerevisiae strain SR8B, which had been engineered for xylose utilization and β-carotene production. In HCB, MCB, and NCB cultures, the yeast produced β-carotene titers of 114.50 mg/L, 93.56 mg/L, and 82.50 mg/L, which corresponds to specific yeast biomass productions of 7.32 mg/g DCW, 8.10 mg/g DCW, and 8.29 mg/g DCW, respectively.

Nucleation and Growth of Cobalt Oxide Nanoparticles in a Continuous Hydrothermal Reactor under Laminar and Turbulent Flow

Cobalt oxide (Co3O4) nanoparticles were synthesized from aqueous solutions of cobalt(II) acetate using a laboratory scale continuous hydrothermal flow synthesis reactor incorporating a confined jet (coaxial) mixer. By changing the concentration of the precursor combined with operating under flow rate conditions expected to result in a laminar or turbulent mixing, the size of the crystallites could be controlled in the range of 6.5–16.5 nm (median). A quench stream was employed to rapidly cool down the nascent stream of nanoparticles and to elucidate the mechanisms of nucleation and growth. The results show a clear correlation between increasing precursor concentration and crystallite size, which at lower concentrations in particular, decreased in laminar flow and increased in turbulent flow. The smallest particles of 6.5 nm (median) were produced at a precursor concentration of 0.1 M (at a rate of 20 g·h–1). The materials were characterized using a range of analytical methods including powder X-ray diffra...

Highly Sensitive ZnO Nanorod- and Nanoprism-Based NO2 Gas Sensors: Size and Shape Control Using a Continuous Hydrothermal Pilot Plant

Continuous hydrothermal flow synthesis of crystalline ZnO nanorods and prisms is reported via a new pilot-scale continuous hydrothermal reactor (at nominal production rates of up to 1.2 g/h). Different size and shape particles of ZnO (wurtsite structure) were obtained via altering reaction conditions such as the concentration of either additive H2O2 or metal salt. Selected ZnO samples (used as prepared) were evaluated as solid oxide gas sensors, showing excellent sensitivity toward NO2 gas. It was found that both the working temperature and gas concentration significantly affected the NO2 gas response at concentrations as low as 1 ppm.

A combinatorial nanoprecursor route for direct solid state chemistry: Discovery and electronic properties of new iron-doped lanthanum nickelates up to La4Ni2FeO10 − δ

We describe a simple nanoprecursor route for direct solid-state combinatorial synthesis and discovery of heterometallic materials compositions which are normally difficult to make in a single step. Using a combinatorial robot (incorporating a continuous hydrothermal reactor), co-precipitated nanoprecursors containing different amounts of La, Ni and Fe oxides were made. These samples were divided into two identical cloned libraries, which were heat-treated to bring about solid-state transformations at either 1348K or 1573K for 12h. In each case, experimental conditions were designed to form the corresponding La4Ni3−xFexO10 phases (x=0.0–3.0) directly without comminution. Such materials are difficult to make without multiple heating and grinding steps. The heat-treated samples from each library were embedded into a wellplate and analysed by powder X-ray diffraction methods in order to elucidate trends in phase behaviour. Several hitherto unknown phase-pure Ruddlesden Popper type La4Ni3−xFexO10 compositions were identified and their DC electrical conductivities measured.