Reaction Mechanism of Coal Chemical Looping Process for Syngas Production with CaSO₄ Oxygen Carrier in the CO₂ Atmosphere

Liu, Yongzhuo,Guo, Qingjie,Cheng, Yu,Ryu, Ho-Jung American Chemical Society 2012 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.51 No.31

<P>Chemical looping combustion process for gaseous and solid fuel has been investigated widely. Recently, particular attention is paid to syngas and hydrogen generation from natural gas or solid fuels. CaSO<SUB>4</SUB> has been proved to be a promising oxygen carrier for the chemical looping process with the merit of low price and environmental friendliness. The reaction mechanism of coal and pure CaSO<SUB>4</SUB> for syngas production in the CO<SUB>2</SUB> atmosphere was investigated using the simultaneous thermal analyzer in this paper. First, the thermodynamic analysis of reaction between coal and CaSO<SUB>4</SUB> with different mass ratios was carried out respectively in N<SUB>2</SUB> and CO<SUB>2</SUB> atmospheres. It predicted that the CO<SUB>2</SUB> can promote the reactions, while the coal-CaSO<SUB>4</SUB> mass ratios affected the fate of sulfurous gaseous species greatly. Subsequently, thermogravimetric experiments were conducted by the peak fitting technique. It concluded that the drying and pyrolysis of the coal were main reactions before 800 °C, while the complex reactions, including the reaction between CaSO<SUB>4</SUB> and coal char, gasification of coal char, and the decomposition of CaSO<SUB>4</SUB>, occurred during 800–1100 °C. The reaction kinetics and types of the reaction between coal and CaSO<SUB>4</SUB> for syngas in the CO<SUB>2</SUB> atmosphere were explored by isoconversional method. It indicated that the complex processes were controlled by the diffusion of gas–solid or solid–solid first, followed by parallel competing reactions. Finally, the reaction residues between coal and pure CaSO<SUB>4</SUB> with different mole ratios were analyzed using scanning electron microscopy and energy dispersive spectrometer (SEM-EDS).</P>

Performance of Ca-Based Oxygen Carriers Decorated by K₂CO₃ or Fe₂O₃ for Coal Chemical Looping Combustion

Guo, Qingjie,Liu, Yongzhuo,Jia, Weihua,Yang, Mingming,Hu, Xiude,Ryu, Ho-Jung American Chemical Society 2014 ENERGY AND FUELS Vol.28 No.11

<P>Chemical looping combustion (CLC) of coal is an attractive technology with inherent CO<SUB>2</SUB> separation and high energy utilization efficiency. The large-scale preparation of a cheap oxygen carrier with high attrition resistance challenges the scale-up step of CLC reactor systems. To improve the reactivity between the CaSO<SUB>4</SUB>/bentonite (CaBen) oxygen carrier and coal, CaSO<SUB>4</SUB>–Fe<SUB>2</SUB>O<SUB>3</SUB>/bentonite (CaFeBen) and CaSO<SUB>4</SUB>–K<SUB>2</SUB>CO<SUB>3</SUB>/bentonite (CaKBen), decorated by Fe<SUB>2</SUB>O<SUB>3</SUB> and K<SUB>2</SUB>CO<SUB>3</SUB>, respectively, were prepared in this work. The active component content, multi-cycle reactivity, and enhancement mechanism of two decorated oxygen carriers were investigated in a fluidized bed with steam as the gasification–fluidization medium. Finally, three types of coals, including lignite, bitumite, and anthracite, were used as fuel. The addition of Fe<SUB>2</SUB>O<SUB>3</SUB> and K<SUB>2</SUB>CO<SUB>3</SUB> can improve the reactivity of the CaBen oxygen carrier but degrade the attrition resistance slightly. The multiple-cycle experiments indicated that Fe<SUB>2</SUB>O<SUB>3</SUB> itself is the oxygen carrier for coal CLC with high reactivity, while K<SUB>2</SUB>CO<SUB>3</SUB> acts as the catalysis for coal gasification. The carbon conversion rate of the three coals that reacted with the CaKBen oxygen carrier was higher than that with CaFeBen as the oxygen carrier because of catalysis of potassium on the coal gasification reaction. However, the CaKBen oxygen carrier particles were seriously sintered, and the potassium content in the oxygen carrier reduced with the increasing redox cycles. The coals with high volatile and ash contents have a high instantaneous rate of carbon conversion reacted with two decorated oxygen carriers.</P>

Coal Chemical Looping Gasification for Syngas Generation Using an Iron-Based Oxygen Carrier

Guo, Qingjie,Cheng, Yu,Liu, Yongzhuo,Jia, Weihua,Ryu, Ho-Jung American Chemical Society 2014 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.53 No.1

<P>The chemical-looping gasification (CLG) of coal is a clean and effective technology for syngas generation. Sharing principles with chemical-looping combustion (CLC), CLG also uses oxygen carriers to transfer lattice oxygen to the fuel. Investigations into CLG with different O/C ratios are carried out in a fluidized bed reactor with steam used as the gasification–fluidization medium. The effect of the active component content of the oxygen carrier on the gas selectivity is performed, and reaction mechanisms between the Fe<SUB>2</SUB>O<SUB>3</SUB> oxygen carrier and coal with steam as the gasification agent are discussed. Moreover, we also assessed the reactivity of the CaO-decorated iron-based oxygen carrier particles in multicycle reactions. The carbon conversion efficiency is increased from 55.74 to 81% with increasing O/C ratio, whereas the content of H<SUB>2</SUB> first decreases and then increases. The addition of CaO can increase the carbon conversion efficiency and the gasification rate substantially and reduce the generation rate of H<SUB>2</SUB>S from 1.89 × 10<SUP>–3</SUP> to 0.156 × 10<SUP>–3</SUP> min<SUP>–1</SUP>. Furthermore, X-ray diffraction (XRD) images indicate that the CaO-decorated iron-based oxygen carrier particles were completely regenerated after six redox cycles. Finally, the peak fitting of gasification reaction rate curves is used to explore the reaction mechanism between coal char and the CaO-decorated iron-based oxygen carrier, indicating that the reactions in the CLG include three stages: the complex reactions involved an oxygen carrier, coal char, and steam; the gasification of coal char; and the reduction of Fe<SUB>3</SUB>O<SUB>4</SUB> to FeO. The two-segment modified random pore model (MRPM) fits the experiment data well.</P>

Cell-Penetrating Peptide-Modified PLGA Nanoparticles for Enhanced Nose-to-Brain Macromolecular Delivery

Lu Yan,Huiyuan Wang,Yifan Jiang,Jinhua Liu,Zhao Wang,Yongxin Yang,Shengwu Huang,Yongzhuo Huang 한국고분자학회 2013 Macromolecular Research Vol.21 No.4

Macromolecular drugs become an essential part in neuroprotective treatment. However, the nature of ineffective delivery crossing the blood brain barrier (BBB) renders those macromolecules undruggable for clinical practice. Recently, brain target via intranasal delivery have provided a promising solution to circumventing the BBB. Despite the direct route from nose to brain (i.e. olfactory pathway), there still are big challenges for large compounds like proteins to overcome the multiple delivery barriers such as nasal mucosa penetration, intracellular transport along the olfactory neuron, and diffusion across the heterogeneous brain compartments. Herein presented is an intranasal strategy mediated by cell-penetrating peptide modified poly(lactic-co-glycolic acid) (PLGA) nanoparticles for the delivery of insulin to the brain, a potent therapeutic against Alzheimer’s disease. The results revealed that the cell-penetrating peptide can potentially deliver insulin into brain via the nasal route, showing a total brain delivery efficiency of 6%. It could serve as a potential treatment for neurodegenerative diseases.

Rapid removal of low concentrations of mercury from wastewater using coal gasification slag

Liangyan Duan,Xiude Hu,Deshuai Sun,Yongzhuo Liu,Qing-Jie Guo,Tongkai Zhang,Botao Zhang 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.7

Coal gasification slag (CGS) is a carbon-containing solid waste used as an adsorbent to remove low concentrations of mercury from wastewater in a series of batch tests to assess its adsorption properties and safe storage. The results showed that the adsorption of mercury on CGS was a very rapid and efficient process, and adsorption equilibrium was reached in only 10-40 min. A pseudo-second-order kinetics model provided a better fit to the equilibrium data. The adsorption capacity on CGS was just slightly below the value of active carbon. CGS showed the highest mercury removal efficiency at a solution pH of 4. Although the presence of other metal cations and anions affected the adsorption, CGS showed good selectivity for mercury ions. The adsorption of mercury was not affected by low concentrations of Cr3+ or Cu2+. The negative interference of anions on the removal efficiency followed the order: Cl>H2PO4 > CO3 2. The adsorption mechanism related to the functional groups included ion exchange, precipitation, coordination complexation, and surface complexation. Mercury adsorbed on CGS leached very slowly in weakly acidic or basic solution. All results of the study indicate that CGS is an economical and safe adsorbent for potential industrial applications.