Experimental study on the activation of coal gasification fly ash from industrial CFB gasifiers

Coal gasification fly ash(CGFA)is an industrial solid waste from the coal circulating fluidized bed(CFB)gasification process,and it needs to be effectively disposed to achieve sustainable development of the environment.To realize the application of CGFA as a precursor of porous carbon materials,the physicochemical properties of three kinds of CGFA from industrial CFB gasifiers are analyzed.Then,the activation potential of CGFA is acquired via steam activation experiments in a tube furnace reactor.Finally,the fluidization activation technology of CGFA is practiced in a bench-scale CFB test rig,and its advantages are highlighted.The results show that CGFA is characterized by a high carbon content in the range of 54.06%–74.09%,an ultrafine particle size(d50:16.3–26.1 μm),and a relatively developed pore structure(specific surface area SSA:139.29–551.97 m^(2)·g^(-1)).The proportion of micropores in CGFA increases gradually with the coal rank.Steam activation experiments show that the pore development of CGFA mainly includes three stages:initial pore development,dynamic equilibrium between micropores and mesopores and pore collapse.The SSA of lignite fly ash(LFA),subbituminous fly ash(SBFA)and anthracite fly ash(AFA)is maximally increased by 105%,13%and 72%after steam activation;the order of the largest carbon reaction rate and decomposition ratio of steam among the three kinds of CGFA is SBFA>LFA>AFA.As the ratio of oxygen to carbon during the fluidization activation of LFA is from 0.09 to 0.19,the carbon conversion ratio increases from 14.4%to 26.8%and the cold gas efficiency increases from 6.8%to 10.2%.The SSA of LFA increases by up to 53.9%during the fluidization activation process,which is mainly due to the mesoporous development.Relative to steam activation in a tube furnace reactor,fluidization activation takes an extremely short time(seconds)to achieve the same activation effect.It is expected to further improve the activation effect of LFA by regulating the carbon conversion ratio range of 27%–35%to create pores in the initial development stage.

Steam gasification reactivity of a high-sodium coal fly ash obtained from a pilot scale CFB gasifier

Circulating fluidized bed （CFB） gasification has several advantages for the utilization of low rank coals. However, the carbon content of fly ash is usually very high, which greatly infuences the gasification efficiency. The purpose of this research is to investigate the gasification reactivity of a high-sodium Zhundong （ZD） coal fly ash obtained from a pilot-scale 2.5 t/d CFB gasification system. The experiments were carried out in a thermogravimetric analyzer with steam as gasification agent, and fast pyrolyzed ZD char was also investigated as a reference sample. The results show that increasing temperature accelerates the gasification rate both for fly ash and ZD char. Fly ash has higher gasification rate at the initial gasification stage. On the contrary, ZD char has higher reaction rate even at higher carbon conversion stage. Via distributed activation energy model, the average activation energy of ZD char and fly ash is calculated to be 94.4 and 91.2 kJ/mol, respectively. The integrated model study reveals that the reaction order of ZD char is about 0.74, whereas the reaction order of fly ash decreases from 1 to 0.59 when temperature increases from 900 to 1050 ℃. The gasification reactivity of ZD coal fly ash is quite different with literature research on those fly ashes with rarely little catalytic elements in coal ashes. The interesting results are related with the unique properties of ZD coal fly ash and the transformation of sodium during gasification process.

POLICIES AND REGULATIONS FOR PROMOTING MANURE MANAGEMENT FOR SUSTAINABLE LIVESTOCK PRODUCTION IN CHINA:A REVIEW

Livestock numbers in China have more than tripled between 1980 and 2017.The increase in the number of intensive livestock production systems has created the challenges of decoupled crop and livestock systems,low utilization of manures in croplands,and subsequent environmental pollution.Correspondingly,the government has enacted a series of policies and regulations to increase the sustainability of livestock production.This paper reviews the objectives of these policies and regulations and their impacts on manure management.Since 2017 there have been two policy guides to speed up the appropriate use of manures,three action plans for increasing manure recycling,and one technical guide to calculate nutrient balances.Requirements of manure pollution control and recycling for improved environmental performance of livestock production systems were included in three revised environmental laws.Most recent survey data indicate that the utilization of livestock manures was 70%in 2017,including that used as fertilizer and/or for production of energy.The targets for manure utilization are 75%in 2020 and 90%in 2035.To achieve these targets and promote‘green livestock production’,additional changes are needed including the use of third-party enterprises that facilitate manure exchange between farms and a more integrated manure nutrient management approach.

Effects of pressure on flow characteristics in a pressurized circulating fluidized bed

The effects of operating pressure on the gas-solid flow characteristics in a pressurized circulating fluidized bed(CFB)gasification system were studied by experiment and simulation.Elevated operating pressure was found to increase the particle uniformity in the axial and radial directions.Experiments and simulations both showed that as the operating pressure increased,the pressure drops along the riser height decreased.The experimental pressure drops at the same locations decreased when the operating pressure increased,but the opposite trend was observed in the simulation results.A proper drag model must be developed for the accurate simulation of pressurized CFB operation,and the accuracy of electrical capacitance tomography(ECT)measurement and cross-correlation analysis should be improved for better prediction of the particle circulation flux.

GREENHOUSE GAS EMISSIONS FROM LIVESTOCK IN CHINA AND MITIGATION OPTIONS WITHIN THE CONTEXT OF CARBON NEUTRALITY

Animal husbandry is a major source of greenhouse gas(GHG)emissions in agriculture.Mitigating the emissions from the livestock sector is vital for green development of agriculture in China.Based on National Communication on Climate Change of United Nations,this study aims to investigate the characteristics of GHG emissions of animal husbandry during 1994 to 2014,introduce major emission reduction technologies and their effectiveness,and investigate options for emission reduction for the livestock sector in China.It proposes that control of pollution and carbon emissions can be realized through increased animal productivity,improved feed quality and recycling of animal manure.This paper thus concludes with suggestions of green and lowcarbon development of animal husbandry,including the research and development of new technology for emission reduction and carbon sequestration of the livestock sector,enhancement of monitoring and evaluation,and establishment of emission reduction and carbon sequestration standards.

阳树脂粉末对阀冷系统6063铝合金的腐蚀影响研究

通过浸泡实验及电化学实验研究了阳树脂粉末对阀冷系统6063铝合金腐蚀影响。结果表明,直流电流会加速试样腐蚀;阳树脂粉末也会加速阀冷系统6063铝合金腐蚀。阳树脂粉末会溶出有机磺化物与SO4^2-,有机磺化物可增强溶液的腐蚀性,故浸泡前期腐蚀速率增大;较高浓度的SO4^2-在一定程度抑制铝合金的腐蚀,导致浸泡后期腐蚀速率减小,但是腐蚀速率仍然较大。电化学实验中6063铝合金自腐蚀电位先降低后升高,自腐蚀电流密度先增大后减小。EIS谱中低频区感抗弧出现,同时容抗弧半径增大,意味着铝合金表面吸附大量的SO4^2-,在一定程度抑制铝合金的腐蚀。

LIVESTOCK AND POULTRY MANURE MANAGEMENT FROM THE PERSPECTIVE OF CARBON NEUTRALITY IN CHINA

The rapid growth of the livestock and poultry production in China has led to a rise in manure generation,which contributes to the emissions of GHGs(greenhouse gases including CH_(4),N_(2)O and CO_(2))and other harmful gases(NH_(3),H_(2)S).Reducing and managing carbon emissions has become a critical global environmental imperative due to the adverse impacts of GHGs.Unlike previous reviews that focused on resource recovery,this work provides an unique insight of transformation from resource-oriented manure treatment to integration of resource recovery with pollution reduction,carbon accounting and trading,focusing on the sustainable development of manure management system.Considering the importance of accounting methodologies for carbon emission and trading system toward carbon neutrality society,suggestions and strategies including attaching high importance to the development of more accuracy accounting methodologies and more practical GHG emission reduction methodologies are given in this paper.This work directs the establishment of carbon reduction methodologies and the formulation of governmental policies for livestock and poultry manure management system in China.

VALORIZATION OF LIVESTOCK WASTE AND CARBON NEUTRALITY

Livestock production has rapidly developed along with improvements in living standards and people’s desire for a better life.Intensive livestock production is important to guarantee supply of meat,eggs and milk,and even vegetable production,in the modern society of China.Recently,the Ministry of Agriculture and Rural Affairs jointly with the National Development and Reform Commission,the Ministry of Finance,and the Ministry of Natural Resources in China formulated and released the National Modern Facility Agriculture Construction Plan(2023‒2030)[1],which proposed the construction of modern animal husbandry facilities with efficient and intensive operations,encouraging the development of three-dimensional facility farms for pigs and poultry,and promoting using multistory buildings according to local conditions.However,large-scale livestock and poultry farms have faced many challenges impacting its green and sustainable development,such as production environment,air quality,manure and sewage treatment and resource utilization.