Integrated Intelligent Energy

Experimental investigation on the influence of particle diameter on co-combustion characteristics of pyrolyzed semi-coke and bituminous coal

YAN Yonghong, CHEN Dengke, SUN Liutao, PENG Zhengkang, SUN Rui

2020, 42(7): 1-10.

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The influence of fuel particle diameter on co-combustion characteristics of pyrolyzed semi-coke and bituminous coal was studied in a 350 kW pilot-scale pulverized coal combustion system.The variation of flue gas temperature and the mass concentrations of O2，CO and NO in the flue gas were measured along the furnace central axis and the primary combustion zone radial direction.According to the testing results，with the increase of blended fuel particle diameter，the jet flame ignition distance decreased first and then increased，while the overall combustion intensity was of an opposite change trend.When R90 is 20%，the ignition distance bottomed out at 164 mm and the overall combustion intensity reached the highest value.At the initial stage of combustion，the mass concentration of NO dropped with the enlarging particle size until it hit the bottom at 438 mg/m3 when the R90 was 20%.In this test，considering the ignition distance，combustion intensity and NO emission from the primary combustion zone comprehensively，it is found that pyrolyzed semi-coke and bituminous coal particle of this size is more conductive to co-combustion.

Effects of ashing method on ash physicochemical characteristics of coal-based solid fuel blends

MAO Qisen, WANG Chang′an, FENG Qinqin, ZHAO Lin,

2020, 42(7): 11-19.

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Ashing method and temperature have significant influences on the ash compositions of solid fuel. However，there are few studies on the ash characteristics of residual carbon and its blends with bituminous coal affected by ashing method. In the exploration on the influence of different ashing methods and temperatures on the ash physicochemical characteristics of coal-based solid fuel blends，the focus laid on the impact of the traditional ash preparation method（815 ℃）and the lowtemperature plasma ashing method（＜200 ℃）on physicochemical characteristics and reaction mechanisms of the ash generated from coal-based solid-fuel blends. The experimental results show that low-temperature ash of all samples，except residual carbon of coal − water − slurry gasification，has a large weight loss peak in 400-600 ℃ ，which is due to the combustion process of the incomplete oxidized organic matter in the low-temperature ash. The main difference between high-temperature ash and low-temperature ash is their formations of Ca element . The Ca in high-temperature ash mainly exists in the form of CaSO4，while that in low-temperature ash is of various forms，such as CaS and CaCO3. Iron element exists as FeS2 in low-temperature ash，while mainly exists in the form of Fe2O3 in high-temperature ash. The interaction of minerals in different fuels should be taken into account when ash samples characteristics of the blends after co-combustion are evaluated. The research is conductive to deepen the understanding of the ashing behaviors in the blending and burning process of solid fuels，and promote the large-scale，efficient and secure utilization of gasification residual carbon.

Effect of different blunt body extensive angles on semi-coke/bituminous coal co-combustion and NOx emission

SUN Liutao, YAN Yonghong, CHEN Dengke, PENG Zhengkang, SUN Rui

2020, 42(7): 20-27.

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The content of O2，CO，NOx and other gases，and the furnace temperature at different axial and radial positions in the downstream main combustion zone of a burner were measured in a 300 kW thermal pilot test furnace.Accordingly，the influence of the extensive angle of an once-through boiler´s blunt body on the ignition characteristics of Shenmu semi-coke and Shenhua bituminous coal co-combustion（semi-coke and bituminous coal were blended with a mass ratio of 45∶55）and NOx emissions was investigated. The results show that with the enlarging of the extensive angle，the ignition position gradually moves towards the upper chamber of the furnace，and the valley value of O2 volume fraction and the peak value of CO mass concentration，namely the strong reducing atmosphere，gradually move towards the furnace wall along the radical direction. When the extensive angle is 29°，the overall temperature of the furnace is considerably high，and the combustion is stable and the NOx emission is reduced.

Study on co-combustion and gaseous pollutants emission characteristics of pyrolysis semi-coke and lignite by TG-FTIR

DAI Ruowei, ZHAO Ruidong, QIN Jianguang, CHEN Tianju, WU Jinhu

2020, 42(7): 28-34.

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The co-combustion and gaseous pollutants emission characteristics of pyrolysis semi-coke and lignite under high heating rates（100-250 ℃/min）were investigated by thermogravimetric analyzer coupled with Fourier transform infrared spectrometer（TG-FTIR）.Results showed that adding lignite into blends could lower the ignition temperature and shorten the burnout time of the blends.All of the index for ignition，burnout and comprehensive combustion performance increased significantly with the increment of lignite blending ratio.Higher heating rates in TG experiments would lead to a higher ignition temperature and temperature at maximum weight loss rate.Meanwhile，the burning rates would also accelerated， which resulted in improved comprehensive combustion performance.The release temperature range of gaseous pollutants was consistent with the main weight loss stages. With the increase of lignite blending ratios，CO2 emission gradually decreased，while NO and NO2 emission generally increased，and the SO2 and CO emission fluctuated.In conclusion，cocombustion exerted certain suppression effect on NOx emission.

Combustion characteristics of semi-coke and its large-proportion co-combustion experimental research in a 660 MW unit

WANG Zhichao1，WANG Yingyan2，LI Yanjun3，TAN Kai3，JIANG Hua4，ZHAO Xiaopeng3，FENG Ping′an2，YAO Wei1*

2020, 42(7): 35-41.

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Based on the experimental research made on semi-coke and its blends with other coals by a one-dimensional flame furnace and a pulverized coal-air mixture flow furnace，semi-coke was proved to be of low volatile content on dry ashfree base，high net calorific value as received basis，low ash melting point，high impingement abrasion index，etc.The testing results showed that semi-coke´s ignition temperature was 710 ℃ ，and the burn-out rate was 97.41%；and the slagging index was 0.84，which indicated that semi-coke was a kind of fuel which was difficult to ignite，and easy to burnout and slag. The ignition and burn-out performances of semi-coke were between that of bituminous coal and lean coal， while its slagging performance was significantly stronger than that of conventional lean coal and anthracite.Dosing semicoke into the blends of different types of coal exerted effects on their ignition，burn-out and slagging characteristics. The cocombustion experiment made on a 660 MW bituminous coal boiler showed that 50%；is the upper limit of semi-coke ratio in the blend for the safe and stable operation of the boiler.Meanwhile，the boiler efficiency slightly increased and the content of unburned carbon in fly ash increased by 0.3 percent point，and the mass concentration of SO2 reduced by 56%，while the he mass concentration of NOx increased by 15%，and the output of coal mill decreased by 15%~20%.

Current status and progress of the clean and efficient utilization of pyrolysis semi-coke

ZHENG Shaowei，WANG Zhiqiang*，WANG Peng，CHENG Xingxing，XU Huanhuan

2020, 42(7): 42-49.

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Cascade utilization is one of the important methods for coal´s efficient and clean utilization. Semi-coke，a byproduct made from low-rank coal in pyrolysis，accounts for about 50% to 70% mass of raw coal and contains about 80% of the energy in raw coal. Thus，the clean and efficient utilization of semi-coke is a key to the cascade utilization of coal. Summarizing the current problems of semi-coke applied in China´s industries，the necessity to realize cascade utilization of low-rank coal by large-scale and clean combustion of semi-coke was analyzed，and the research progress on existed clean and efficient combustion technology of semi-coke was concluded.It provide a reference for future research in this field.

Study on operation characteristics of a 35 t/h preheating combustion boiler with pure ultra-low volatile carbon-based fuels

OUYANG Ziqu1，2，MAN Chengbo1，LI Zenglin4，LI Shiyuan1，2，3*，PANG Qingtao4，ZHU Jianguo1，2，FAN Zhigang4，LIU Jingzhang1

2020, 42(7): 50-56.

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Ultra-low volatile carbon-based fuels，such as semi-coke and gasified residual carbon，are produced in pyrolysis and gasification of low-rank coal.A preheating combustor and auxiliary systems were installed on a 35 t/h coal-fired boiler combusting pure ultra-low volatile carbon-based fuels，so as to stabilize and enhance the burning of ultra-low volatile carbon-based fuels and lower the emission of pollutants. In the experiments carried out on the boiler，using Shenmu bituminous coal，Shenmu semi-coke and gasified residual carbon，effects of fuel type，preheating temperature，secondary air equivalent ratio and boiler load on combustion characteristics and pollutant emission were studied. The results showed that the three fuels can burn stably，and so can the pure semi-coke powder with dry ash-free volatilization fraction of 4.30%，which indicated the good fuel adaptability of the boiler. Been preheated，all the combustion efficiencies of the three fuels exceeded 99%. With the rise of preheating temperature，the overall temperature of the furnace increased，and the NOx emission mass concentration decreased first and then increased，indicating that the increase of preheating temperature was conducive to the combustion and heat release of preheated fuel in the furnace.When the preheating temperature was 887 ℃，the minimum NOx emission mass concentration was 110.6 mg/m（3 standard state，φ（O2）=9%）.The preheated boiler has good combustion stability under low loads. As boiler load is lower，the NOx emission decreased and bottomed at 108.0 mg/m3（standard state，φ（O2）=9%），which reflects the advantages of preheating combustion technology in stabilizing combustion，burnout and low NOx emission.

Feasibility analysis on applying semi-coke molding technology in civil fuels

LI Yao1，2，3，XU Jie1，2，WANG Yichen1，2，CHEN Gang1，2，YANG Xiaoyan1，2，

2020, 42(7): 57-62.

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The feasibility of using semi-coke briquette as civil fuel was analysis from three aspects，semi-coke composition，molding technology and economy. In terms of composition，by comparing the indicators of current national standards for civil briquette with that of commercially available semi-coke products，it is found out that although the quality of semi-coke can be affected by various factors such as pyrolysis process，coal quality，particle size，etc.，the calorific value，total sulfur and volatile content indexes can always meet the corresponding requirements for the briquette coal. In terms of molding technology，the compound binder is mostly used in producing civil semi-coke making in conjunction with the cold-press molding technology of roller briquetting machine. The molded product is of good performance in combustion and pollutant emissions reduction. In terms of economy，the briquette is of considerable economic benefits under the current coal price system，no matter whether it is made from purchased semi-coke powder or made by a ranked coal clean conversion project which takes semi-coke civil briquette as its main product.

Review on the comprehensive resources utilization technology of coal gasification fine slag

SHI Zhaochen , DAI Gaofeng , WANG Xuebin , DONG Yongsheng , LI Pan ,

2020, 42(7): 63-73.

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Gasification is an effective way for clean and efficient utilization of coal.However，due to the poor performance and operation level of gasifier and its equipment at present，a large number of coarse gasification slag and fine gasification slag will be produced.The composition of the coarse gasification slag is similar to boiler ash and slag，which can be used as materials for buildings，road bridges and polyblends.However，gasification fine slag cannot be directly used as building and road materials for its high carbon content and high burning loss，which takes landfill disposal as its most important treatment method at present.This method not only wastes land，but also fails to recover the residual carbon，which is of poor economic and environmental performance.Economic，environmental and efficient processing of gasification fine slag is a major challenges for coal gasification enterprises.The basic physical and chemical characteristics of fine slag produced by a few typical gasifiers are summarized，including its high unburned carbon and silica-alumina contents，wide specific surface area and developed pore structure.Its research progress and application prospects in being processed by flotation separation technology and water treatment technology，and being taken as coal blends for combustion，soil amelioration，synthesic and preparation materials are compared.

Co-combustion characteristics and kinetics analysis of residual carbon from gasification and low-rank coals

ZHENG Hongyan, JIA Dingding, ZHAO Yan, FENG Zhihao, BAI Zongqing

2020, 42(7): 74-80.

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High-efficiency combustion of residual carbon from gasification（RCG）is key to its cascade utilization. Cocombusting it with coal is a promising method to lower the fire point and dent the difficulty in burn-out.Studying the cocombustion characteristics of RCG and three low-rank coals（YN lignite，HM long flame coal and SH non-caking coal）by thermogravimetric analysis，their featured parameters and interactions were obtained. Taking multiple scanning method， the co-combustion kinetics parameters of RCG and low-rank coals were analyzed. The results showed that the peak temperatures difference（DT）of co-combusted RCG and coals was narrowed down，compared with that of an individual fuel. And DT decreased with the mounting of RCG when it was co-combusted with SH coal and YN coal，which indicated apparent interactions between RCG and coals during co-combustion. The release and combustion of volatile matters could promote the combustion of RCG.The rich calcium and iron in Hami coal had a certain catalytic effect on the combustion of RCG. According to kinetics analysis，the apparent activation energy of the blended sample is lower compared to that of RCG，which implied the overall combustion performance could be improved by co-combustion of RCG and coals.

Research progress on flotation decarburization of gasified fine slag

WU Siping1，ZHAO Kai1，DONG Yongsheng2，WANG Xuebin3*，BAI Yonghui4，

2020, 42(7): 81-85.

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In order to reduce the mass fraction of unburned carbon which restricts the further processing and utilization of gasified fine slag，on the basis of current situation and research progress on the flotation process for gasified fine slag and its characteristics such as residual carbon，mineral composition and apparent morphology，the froth flotation process was adopted in the unburned carbon removal experiment taking Yulin gasified fine slag.The experimental results showed that the yield of final concentrate was 11.06% ，with 30 kg/t diesel oil as collector agent and and l10 kg/t sec-octanol as foaming agent and taking "one rough flotation and two cleanings"concentrate separation process . This flotation process is difficult. Considering the properties of gasified slag，it can be preliminarily judged that the high porosity and large specific surface of gasified slag can lead to high consumption of flotation agent and poor flotation index.

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