Table of Content

25 October 2020, Volume 42 Issue 10

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Kinetic analysis on thermal conversion made by carbon dioxide and crude coke oven gas

ZHANG Jian, ZHANG Baoxu, PENG Ruifeng, CHEN Yumin

2020, 42(10):  1-12. 

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The heat in hot steel slag could be recycled through dry reforming of coke oven gas，and coke oven gas（COG）
and carbon dioxide from coke ovens and steel plants could be utilized simultaneously. Kinetic analysis and mechanism
study on thermal conversion process of carbon dioxide and COG were made. Effects of temperature，volume flow ratio of
CO2 to COG at inlets（ψ），volume flow of COG at inlets（qVCOG（in）），pressure（p）and reaction atmosphere on dry reforming
process were investigated quantitatively，and reactants conversion and products formation mechanism in the process were
analyzed. The calculation results demonstrate that，in order to obtain the product gas with a hydrogen-carbon ratio of 2，
1 600 — 2 100 K is the suitable range for reaction temperature and 0.16 — 0.21 is the suitable range for ψ for direct dry
reforming process of crude COG when p is 0.1 MPa and qVCOG（in） is 1 cm3/s. At this time，the yield of syngas（γsyn）is 0.76 —
0.92，and conversion rates of tar and CO2 are 90% and 80%，respectively. Adding H2O into the reforming medium can
facilitate tar conversion slightly，but decrease the conversion rate of CH4 and CO2，as well as syngas yield. Addition of O2
would increase the reaction temperature，CH4 conversion rate and syngas yield.

Experimental study on SO2 reduction to elemental sulfur with powdered activated carbon in a drop-tube reactor#br#

FENG Tai, YAN Luyu, LIU Zhi, XU Tianming, ZHOU Binxuan, ZHAO Xiqiang, MA Chunyuan

2020, 42(10):  13-21. 

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In view of sulfur resources shortage in China and the problem that SO2 recycling cannot be realized by current
desulfurization technology，a method was proposed to reduce SO2 to elemental sulfur by using activated carbon powder as
reducing agent under gas-solid two-phase flow. The effects of reaction temperature，molar ratio of C/SO2，and concentration
of CO，H2，CO2 and water vapor on the reaction were studied. The results show that higher reaction temperature and C/SO2
molar ratio are conducive to improving the reduction efficiency and reaction rate of SO2 by activated carbon，and have little
effect on COS generation and lead to a high selectivity of elemental S. The addition of CO and H2 can significantly improve
the conversion rate of SO2，but a large number of S-containing by-products are generated during the reaction，leading to a
decrease in the selectivity of elemental S. CO2 has little effect on the whole reaction. The addition of H2O affects the Claus
reaction balance，resulting in the increase of H2S production and the significant decrease of the selectivity of elemental S.
The economic analysis indicates that the main cost of the process includes energy consumption for heating and reaction
material consumption of activated carbon. Every 1 g removed SO2 can produces 0.38 g sulfur，and consumes 0.16 g
activated carbon and 1.7 kJ energy. This study provides theoretical support for the carbothermal reduction of SO2 in
fluidized beds.


Effect of activated coke diameter on SO₂ adsorption in fixed-bed and entrained-flow reactors

ZHANG Mengze, LIU Zhi, ZHANG Liqiang, LI Yang, ZHOU Binxuan, MA Chunyuan, DONG Yong

2020, 42(10):  22-27. 

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Flue gas desulfurization（FGD）by activated coke（AC）is of great potential in the recycling technology. AC
particles with smaller diameter are superior to the one with larger diameter in cost and absorptive mass transfer. Proven by
the tests on AC with different particle diameters，the SO2 adsorption rate of AC increased with the decrease of AC's particle
size both in the fixed-bed and entrained-flow reactors，since the mass transfer resistance of AC with smaller diameter is
lower than that with larger diameter.Taking AC with the same particle size，the adsorption rate of AC in the entrained-flow
reactor was higher than AC in the fixed-bed reactor by two orders of magnitude. Broken into smaller particles，the total
specific pore volume and total specific surface area of AC is greatly increased. The increased specific surface area is mainly
brought by the additional medium and large pores（pore diameter > 2 nm），who improve the diffusion of SO2 on the surface
and inside of AC.The pores also facilitate the migration and storage of the by-products from adsorption process and raise the
adsorption rate of AC.


Structure and function of important C/O intermediates in semi‐coke DeNOx systems

FAN Chuigang, LI Songgeng,

2020, 42(10):  28-35. 

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Temperature programmed rising test(TPR)and constant temperature test for deNOx were conduct on semi ‐ coke
pyrolyzed from coals of different ranks from 11 regions in China.Based on their deNOx efficiencies,the 11 types of coke can
be divided into two groups.By means of BET pore analysis,X-Ray Photoelectron Spectroscopy（XPS）,Transmission Electron
Microscope（TEM）and X-Ray Fluorescence（XRF）,it is found that the two groups exhibit significantly different adsorption
isotherms, micro layered structure, and pore size distribution in terms of the physical characteristics; and chemically, the
amount of C—O single bond and alkaline earth metals(can be as great as 2~4 times of magnitude)varies differently in two
groups of samples.It is also found that their component has clear and simple linear correlation with denitration efficiency
indexes of the 11 types of coke (absolute value of linear correlation |r| sways within 0.841~0.992). Comprehensively
analyzing the simulation results and metal modification controlled tests，preliminary speculation was made that the
difference in semi‐coke's denitration effect under different conditions could be led by C—O single bond on its surface and
its chemical behavior in the reaction system during the denitration process.


Research progress in amino-modification porous solid adsorbents applied in CO₂ adsorption

HU Xiaofu, SHEN Jianyong, WANG Hua, ZHANG Xiqian, XIA Huaipeng

2020, 42(10):  36-40. 

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As the core component in CO2 capture by adsorption，solid adsorbents are of low raw material loss，low energy
consumption，weak corrosiveness，good cycling stability，simple operation，environment friendly performance and other
benefits.Thus，it will be widely used.Compared with conventional solid adsorbents，amino-modification porous solid adsorbents
have better adsorption selectivity and higher adsorption efficiency，and have become the hot-spot in this field.The amino-
modification porous solid adsorbents prepared in different conditions are introduced，which include material for amino-
modification porous molecular sieves，amino-modification porous carbon and material for amino-modification organic
frameworks.The application of the materials in the latest CO2 capture technology and in other new materials development is
prospected.


Study on the characteristics of Hg⁰ re-emission and mercury removal by ionic liquid in WFGD systems

XU Jialing, BAO Jingjing, YU Jianghuai, LUO Ziling, SUN Licheng

2020, 42(10):  41-47. 

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To further improve the mercury removal efficiency of wet flue gas desulfurization（WFGD）systems，the
characteristics of Hg0 re-emission and the mercury removal performances of different ionic liquids were studied at low SO32-
concentrations. Based on a bubble reactor，the effects of SO32- and metal ions（Fe2+，Fe3+ and Cu2+）on the characteristics of
Hg0 re-emission in WFGD systems were investigated under N2 atmosphere. The mercury removal performances of three
ionic liquid additives（HMIM［PF6］，BMIM［PF6］and BMIMCl）were also studied，and the optimal operating conditions
for the best-performing additives were obtained. The results indicate that increasing SO32- concentration at a relatively low
level can intensify the reduction of Hg2+ ，whereas Hg0 re-emission is significantly inhibited with excess concentration of
SO32- . It is also found that Fe2+ ，Fe3+and Cu2+can facilitate Hg0 re-emission. The three ionic liquid additives above show
effective inhibitions on Hg0 re-emission in the order of BMIMCl＞BMIM［PF6］＞HMIM［PF6］. Further experiments were
carried out on BMIMCl to obtain its optimal condition for inhibiting Hg0 re-emission. The optimal condition for BMIMCl is
at a mass concentration of 10 g/L，a lower pH value and a desulfurization liquid temperature at 50 ℃.


Study on mercury removal by activated coke

AN Donghai, WANG Luyuan, CHENG Xingxing, DONG Yong

2020, 42(10):  48-55. 

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Powdered activated coke was prepared from Xinjiang Heishan lignite by a drop-tube reactor. The physical
features and surface morphology of the coke samples were examined by Brunauer-Emmett-Teller（BET）measurements
and Scanning Electron Microscope（SEM），and the Hg0 adsorption capacity of the activated coke was studied in a bubble
reactor. The results show that the specific surface area of the activated coke is 402.1 m2/g，and its carbon consumption rate
is 42.18%. The specific surface area of the pore accounts for 77.5% of the total specific surface area，with an average
diameter of 2.10 nm. The average Hg0 adsorption efficiency of the activated coke is 85% within 3 h. The desorption capacity
of the used activated coke was further investigated through thermal desorption method，and the deep curing was carried out
on the desorbed Hg0 and the influencing factors on HgS synthesis were systematically analysed. The results showed that Hg0
was mainly adsorbed physically by the activated coke，with assistant of chemical adsorption. O2 could barely promote the
HgS synthesis，while SO2 and H2O had inhibiting effect on HgS synthesis.


Effect of sorbent on the chromium transformation in Zhundong coal

SUN Yingwen, LI Xiaoyu, CHEN Juan, HAN Jun

2020, 42(10):  56-63. 

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In order to control the formation and emission of chromium generated from coal combustion，combustion tests
were carried out on Zhundong coal with different adsorbents. The effects of four different sorbents（CaO，Al2O3，Fe2O3，
kaolin）on the retention of chromium in ash were investigated through experiments，and the thermodynamic calculation was
conducted to reveal the influence of sorbents on Cr retention，leaching and thermodynamic equilibrium transformation. The
results show that adsorbent CaO or Fe2O3 reacts with chromium compounds to generate chromate，showing a favorable Cr
retention rate which can exceed 80%，while the Cr retention rate with adsorbent Al2O3 or kaolin is quite low. The leaching
rate of Cr in burning ash is the lowest with adsorbent Fe2O3. The Cr in the ash generated from Oxy-fuel combustion can be
better leached，compared to that generated from Air combustion，and the leaching rate of Cr in fine ash is higher than that
in coarse ash.From the perspectives of Cr capture efficiency and low leaching rate, Fe2O3 is the most effective chromium
adsorbent.


Numerical study of the emission from co-combustion of large-proportion semi-coke and pulverized coal

ZHAO Yang, CHEN Bing´an, WANG Pengxiang, LI Xianda, SUN Rui, SUN Shaozeng

2020, 42(10):  64-72. 

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Semi-coke is a product obtained from dry distillation of raw coal，and is of high calorific value and low volatile
content. At present，semi-coke，as a by-product of coal chemical industry，has not been fully utilized.Studying the blending
and co-combustion of semi-coke with pulverized coal will improve its economic benefit. However，the difficulties of the co-
combustion lay on the poor ignition conditions，low burnout rate and high NOx emission.In the study on co-combustion of
pulverized coal blended with large-proportion semi-coke，the effect of coal powder feeding method，blending ratio and
secondary air distribution on the temperature field，NO mass fraction field and CO mass fraction field in a furnace was
analyzed by numerical simulation.The results show that the optimal blending ratio of semi-coke is 40%；under the condition
of even air and powder distribution. When the fuel is stratified，the semi-coke arranged on the upper part of the burner will
make furnace temperature and NO mass fraction soar ，which can be improved by optimize the secondary air distribution .


Experiment on preheating combustion of ultra-low volatile carbon-based fuel by an internal circulation preheater

SONG Wenhao, LI Shiyuan, OUYANG Ziqu, LIU Jingzhang

2020, 42(10):  73-80. 

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On the basis of preheating combustion technology，an internal circulating preheater for the stable combustion of
fine powdered fuel was proposed，which was aimed at the clean and efficient utilization of ultra-low volatile carbon-based
fuel.The operating characteristics of the internal circulating preheater was investigated on an internal circulating preheater
cold test rig，a 2 MW internal circulating preheating combustion pilot test rig and a 16 MW preheater testing platform
successively.Also，the characteristics of preheating，combustion and NOx emission of ultra-low volatile carbon-based fuel
were discussed.The results showed that the material balance and a stable circulation could be established in the internal
circulating preheater when fluidizing air velocity was in the range of 1.50—2.25 m/s. A stable preheating process was
realized by preheating the fuel in the internal circulating preheater steadily and continuously to 850 ℃ and above，thereby
meeting the requirement of the preheating combustion process.The high-temperature gas fuel mainly included N2，H2，CO，
CH4 and CO2. And 57.08% of nitrogen element was released in the internal circulating preheater. Proven by testing，the
combustion efficiency was higher than 97%，and NOx emission reduced to 112.7 mg/m（3@6% O2）.


Primary study on the pilot-scale experiment of preparation for powdered activated coke from lignite

WANG Tao, LIU Ke, ZHANG Zhen, ZHOU Binxuan, MA Chunyuan

2020, 42(10):  81-87. 

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Flue gas desulfurization（FGD）using activated coke is one of the main technologies for sulfur recovery.In view of
the high cost of activated coke in the desulfurization process of the current shaped particle activated coke moving bed，a
one-step powdered activated coke（PAC）preparation process for FGD was proposed and developed，which can carbonize
and activate pulverized coal ly.Based on the basic research data from the laboratory，a pilot-scale experimental device and
system with a PAC output of 30 kg/h was built，and a preliminary test for the rapid preparation of PAC was made.
Comparative analysis of the results from the pilot-scale experiment and experimental study was conducted.Under the pilot-
scale experimental conditions，the PAC yield prepared from Mengdong lignite was 38%，lower than that under experimental
condition.The pores of the PAC from the pilot-scale experiment were mainly micropores，whose pore volume and specific
surface area were better than the PAC from two lab experiments. The adsorption capacity of PAC from the pilot-scale
experiment was 6.1% per two hours.It was lower than that in two lab experiments，which should be caused by the difference
in particle size and pore structure. The volume fraction of combustible components（CO+H2+CH4）in pyrolysis gas，a by-
product in PAC preparation process in the pilot-scale experiment，was 7.3%，higher than that in lab experiments.The results
of the pilot-scale experiments preliminarily verified the feasibility of the process of PAC rapid preparation from lignite.


Review of biomass power generation technology coupled with large coal-fired boilers in Europe

LAN Fengchun, LI Xiaoyu, LONG Hui

2020, 42(10):  88-94. 

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Biomass power generation technology coupled with coal-fired boilers，a widely applied technology in Europe，is
an effective method to lower the CO2 emission of coal-fired power plants. Investigated the application of biomass power
generation technology coupled with large coal-fired boilers in Netherlands，Finland，the United Kingdom and other
European countries，the development of this technology and some typical cases of European power plants were described，
and the main technical routes were summarized.UK was pointed out to be the country with the most developed coupling
power generation technology. This technology proposed in the 14th Five-Year Plan should be taken seriously and be
considered as a main technique to be developed in China. It is concluded that the technical routes coupling 15%~40%
（mass fraction）biomass in co-combustion is adaptive for the large coal-fired boilers coupled with biomass in China.And
further recommendation on the technology is also proposed.


Devolatilization and nitrogen conversion characteristics of the mixture of semi-coke and bituminous coal

YU Qiang, WANG Minghao, GUAN Jingyu, JIA Geng

2020, 42(10):  95-98. 

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In order to apply semi-coke to large-proportion co-combustion in pulverized coal boilers and reduce NOx
emission，the study on devolatilization and nitrogen conversion characteristics of bituminous coal and semi-coke blends
under different mixing proportions are made on a dropping tube furnace. The results show that under certain temperature，
the release rate of volatile matters is related to the mixing proportion and the residence time in the furnace. The release rate
of volatile matters decreases as the mixing proportion of semi-coke increases，and accumulates with the increase of the
residence time. The maximum release rate of volatile matters is greater than that in proximate analysis. And with the
increase of the blending proportion of semi-coke，the char nitrogen from the blend shows an upward trend，and the volatile
nitrogen shows a downward trend. When the proportion of semi-coke exceeds 50% of the blend，the char nitrogen of the
blend increases by 6.08% compared with that of the raw coal，thus the difficulty of NOx emission control increases.