Characteristics of reactivity and structures of palm kernel shell (PKS) biochar during CO_2/H_2O mixture gasification

Palm kernel shell(PKS)biochars with different levels of carbon conversion were initially prepared using a tube furnace,after which the reactivity of each sample was assessed with a thermogravimetric analyzer under a CO_2 atmosphere.The pore structure and carbon ordering of each biochar also examined,employing a surface area analyzer and a Raman spectroscopy.Thermogravimetric results showed that the gasification index R_sof the PKS biochar decreased from 0.0305 min^(-1) at carbon conversion(x)=20% to 0.0278 min^(-1)at x=40%.The expansion of micropores was the dominant process during the pore structure evolution,ad mesopores with sizes ranging from 6 to 20,48 to 50 nm were primarily generated during gasification under a CO_2/H_2O mixture.The proportion of amorphous carbon in the PKS biochar decreased significantly as x increased,suggesting that the proportion of ordered carbon was increased during the CO_2/H_2O mixed gasification.A significantly reduced total reaction time was observed when employing a CO_2/intermittent H_2O process along with an 83.46% reduction in the steam feed,compared with the amount required using a CO_2/H_2O atmosphere.

Energy and economic analysis of a hydrogen and ammonia co-generation system based on double chemical looping

In this work,a model of hydrogen production by double chemical looping is introduced.The efficiency benefit obtained was investigated.The chemical looping hydrogen generation unit is connected in series to the downstream of a chemical looping gasification unit as an additional system for 100 MWh coal gasification,with the function of supplementary combustion to produce hydrogen.Using Aspen Plus software for process simulation,the production of H_(2) and N_(2) in the series system is higher than that in the independent Chemical looping gasification and Chemical looping hydrogen generation systems,and the production of hydrogen is approximately 25.63%and 12.90%higher,respectively;The study found that when the gasification temperature is 900C,steam-carbon ratio is 0.84 and oxygen-carbon ratio is 1.5,the hydrogen production rate of the system was the maximum.At the same time,through heat exchange between logistics,high-pressure steam at 8.010×10^(4) kg·h^(-1) and medium-pressure steam at 1.101×10^(4) kg·h^(-1) are generated,and utility consumption is reduced by 61.58%,with utility costs decreasing by 48.69%.An economic estimation study found that the production cost of ammonia is 108.66 USD(t NH_(3))^(-1).Finally,cost of equipment is the main factors influencing ammonia production cost were proposed by sensitivity analysis.

Mechanism analysis and simulation of methyl methacrylate production coupled chemical looping gasification system

Nowadays,the efficient and cleaner utilization of coal have attracted wide attention due to the rich coal and rare oil/gas resources structure in China.Coal chemical looping gasification(CCLG)is a promising coal utilization technology to achieve energy conservation and emission reduction targets for highly pure synthesis gas.As a downstream product of synthesis gas,methyl methacrylate(MMA),is widely used as raw material for synthesizing polymethyl methacrylate and resin products with excellent properties.So this paper proposes a novel system integrating MMA production and CCLG(CCLG-MMA)processes aiming at"energy saving and low emission",in which the synthesis gas produced by CCLG and purified by dry methane reforming(DMR)reaction and Rectisol process reacts with ethylene for synthesizing MMA.Firstly,the reaction mechanism of CCLG is investigated by using Reactive force field(ReaxFF)MD simulation based on atomic models of char and oxygen carrier(Fe_(2)O_(3))for obtaining optimum reaction temperature of fuel reactor(FR).Secondly,the steady-state simulation of CCLG-MMA system is carried out to verify the feasibility of MMA production.The amount of CO_(2)emitted by CCLG process and DMR reaction is 0.0028(kg CO_(2))^(-1)·(kg MMA)^(-1).The total energy consumption of the CCLG-MMA system is 45521 kJ·(kg MMA)^(-1),among which the consumption of MMA production part is 25293 k(·kg MMA)^(-1).The results show that the CCLG-MMA system meets CO_(2)emission standard and has lower energy consumption compared to conventional MMA production process.Finally,one control scheme is designed to verify the stability of CCLG-MMA system.The CCLG-MMA integration strategy aims to obtain highly pure MMA from multi-scale simulation perspectives,so this is an optimal design regarding all factors influencing cleaner MMA production.

Simulation study on the gasification process of Ningdong coal with iron-based oxygen carrier

Chemical looping gasification(CLG) of Ningdong coal by using Fe_(2) O_(3) as the oxygen carriers(OCs) was studied,and the gasification characteristics were obtained.A computation fluid dynamics(CFD) model based on Eulerian--Lagrangian multiphase framework was established,and a numerical simulation the coal chemical looping gasification processes in fuel reactor(FR) was investigated.In addition,the heterogeneous reactions,homogeneous reactions and Fe_(2) O_(3) oxygen carriers' reduction reactions were considered in the gasification process.The characteristics of gas flow and gasification in the FR were analyzed and it was found that the experiment results were consistent with the simulation values.The results show that when the O/C mole rate was 0.5:1,the gasification temperature was 900℃ and the water vapor volume flow rate was 2.2 ml·min^(-1),the mole fraction of syngas reached a maximum value of the experimental result and simulation value were 71.5% and 70.2%,respectively.When the O/C mole rate was 0.5:1,the gasification temperature was 900℃,and the water vapor volume flow was 1.8 ml·min^(-1);the gasification efficiency reached the maximum value was 62.2%,and the maximum carbon conversion rate was 84.0%.

3 MW_(th)煤化学链气化商业示范装置的自热运行和参数分析

为实现MW_(th)规模化学链气化商业示范装置的自热运行,使用Aspen Plus进行模拟研究。通过实验数据,验证了过程模型的可靠性。考察了3 MW_(th)煤化学链气化系统的质量和热量平衡。通过分析反应器温度、蒸汽流率和温度、旋风分离器效率、载氧体活性成分含量等工艺参数对系统合成气产率、合成气组分浓度、合成气H_(2)/CO、固体循环流率等工艺性能的影响,确定了合成气产量最大化的自热操作条件。结果表明,3 MW_(th)煤化学链气化系统的净热功率越接近于0,系统越趋于自热运行。系统自热运行时的最佳操作条件为燃料反应器温度850℃、空气反应器温度950℃、蒸汽流率305.25 kg/h、蒸汽温度300℃、旋风分离器效率98%,系统的固体循环流率最小,约为10 555~10 580 kg/h,合成气总浓度(CO+H_(2))最大,约为75.1%。此外,使用活性成分含量较高的钛铁矿颗粒作为载氧体,有利于减少系统的固体循环流率。

Thermogravimetric characteristics of corn straw and bituminous coal copyrolysis based the ilmenite oxygen carriers

Herein,the co-pyrolysis reaction characteristics of corn straw(CS)and bituminous coal in the presence of ilmenite oxygen carriers(OCs)are investigated via thermogravimetry coupled with mass spectrometry.The results reveal that the participation of OCs weakens the devolatilization intensity of co-pyrolysis.When the CS blending ratio is<50%,the mixed fuel exhibits positive synergistic effects.The fitting results according to the Coats-Redfern integral method show that the solidesolid interaction between OCs and coke changes the reaction kinetics,enhancing the co-pyrolysis reactivity at the high-temperature zone(750e950
C).The synergistic effect is most prominent at a 30%CS blending ratio,with copyrolysis activation energy in the range of 26.35-40.57 kJ·mol^(-1).

Efficient CO_(2) adsorption and mechanism on nitrogen-doped porous carbons

In this work,nitrogen-doped porous carbons(NACs)were fabricated as an adsorbent by urea modification and KOH activation.The CO_(2) adsorption mechanism for the NACs was then explored.The NACs are found to present a large specific surface area(1920.72-3078.99 m2·g^(-1))and high micropore percentage(61.60%-76.23%).Under a pressure of 1 bar,sample NAC-650-650 shows the highest CO_(2) adsorption capacity up to 5.96 and 3.92 mmol·g^(-1) at 0 and 25℃,respectively.In addition,the CO_(2)/N_(2) selectivity of NAC-650-650 is 79.93,much higher than the value of 49.77 obtained for the nonnitrogen-doped carbon AC-650-650.The CO_(2) adsorption capacity of the NAC-650-650 sample maintains over 97% after ten cycles.Analysis of the results show that the CO_(2) capacity of the NACs has a linear correlation(R^(2)=0.9633)with the cumulative pore volume for a pore size less than 1.02 nm.The presence of nitrogen and oxygen enhances the CO_(2)/N_(2) selectivity,and pyrrole-N and hydroxy groups contribute more to the CO_(2) adsorption.In situ Fourier transform infrared spectra analysis indicates that CO_(2) is adsorbed onto the NACs as a gas.Furthermore,the physical adsorption mechanism is confirmed by adsorption kinetic models and the isosteric heat,and it is found to be controlled by CO_(2) diffusion.The CO_(2) adsorption kinetics for NACs at room temperature and in pure CO_(2) is in accordance with the pseudo-first-order model and Avramís fractional-order kinetic model.