Changes in sulfur form during coal desulfurization with microwave:Effect on coal properties

The changes in sulfur form in coal were analyzed by sulfur K-XANES(K-edge X-ray absorption near edge structures) spectra before and after the coal microwave desulfurization in a Na OH solution. After the desulfurization, the pyritic sulfur content of coal decreased significantly from 53.6% to 39.2%, while the sulfate sulfur content increased from 17.3% to 34.6%. Only a small amount of thiophene sulfur(20.1–16.1%) was removed. Some sulfur-containing components were oxidized to sulfate sulfur. Under the optimum conditions, the ash content decreased, while the volatile content increased. The calorific value of coal slightly decreased with a slight variation in the amplitudes. The overall structure of coal did not change significantly based on Fourier transform infrared(FTIR) spectral analyses. Thus, the desulfurization of coal with microwave irradiation in a Na OH solution did not significantly change the properties of coal.

Factors Influencing Conversion of Pyritic Sulfur in Coal by Microwave Irradiation

The high sulfur coal from southwest of China was used to examine the influence of different factors such as irradiation time, particle size of coal, and leachant (Na2CO3, NaOH and CuCl22H2O)on the conversion rate of pyrite to pyrrhotite by microwave irradiation. Single factor experiment was performed firstly, then orthogonal test method was used to explore these factors. The result shows that the optimal treating conditions for the conversion are a treatment time of 3 min, a particle size from 0.086 mm to 0.102 mm, and a favorable leachant of sodium hydroxide. Under these conditions the conversion rate of pyrite can reach 45.7 %.

MOSSBAUER ANALYSIS ON THE MICROWAVE-MAGNETIC DESULFURIZATION OF RAW COAL

The selective dielectric heating of microwave energy to convert a portion of each pyrite particle to moderately magnetic pyrrhotite has been suggested to enhance the magnetic separation of inorganic sulfur from coal. The results for Mossbauer analyses show that the considerable amount of pyrrhotite produced during microwave irradiation, carrying with it some of non--magnetic pyrite (unconverted), ferrous sulfate, and troilite, is completely removed from coal after magnetic separation. The opthoum desulfurization efficiency can be attsined by appropriately controlling the irradiation time to maximize the amount of pyrrhotite formed pyrite decomposition.Excessive irradiation would be disadvantageous for improving magnetic separation due to the further decomposition of pyrrhotite to antiferromagnetic troilite.

Mssbauer Study of Coal Desulfurization by Microwave Irradiation Combined With Manetic-Separation and Chemical Acid-Leaching

^(57)Fe Mssbauer spectroscopy was used to study the mechanism and regularity of coal desulfurization by microwave irradiation combined with magnetic-separation and with chemical acid-leaching. The results of phase analyses show that the decomposing reaction of pyrite intrinsic in coal, caused by the selective dielectric heating of microwave electromagnetic energy, FeS_2→Fe_(1-x)S→FeS, consecutively progresses towards the right-hand side with increased irradiation time. The whole process of microwave desulfurization of raw coal consists of the initiation, the promotion, and the saturation stages. The optimum desulfurization efficiency for microwave irradiation combined with magnetic-separation treatment and with chemical acid-leaching treatment can be attained by appropriately controlling the irradiation time to enable the corresponding microwave treatment to lie in the promotion stage and the saturation stage, respectively.

TRACKING PYRITIC SULFUR DURING THE MICROWAVE- CHEMICAL DESULFURIZATION OF COAL USING MOSSBAUER SPECTROSCOPY

The transformations of pyrite in coal during the microwave-chemical treatment for desulfurization of coal was studied with Mossbauer spectroscopy of Fe. The results for phase analyses show that the selective dielectric heating by microwave energy can give rise to the thermal decomposition of pyrite FeS2 in coal to new phases, pyrrhotite Fe1-xS (0【x≤0.125) and troilite FeS which can be dissolved in dilute HC1 solution. Therefore the microwave irradiation combined with the acid washing treatment will be an effective method of desulfurization of coal.

INFLUENCE OF IRRADIATION TIME ON THE MICROWAVE DESULFURIZATION OF COAL

The microwave desulfurization is a novel and attractive physical method for coal cleaning, which is divided into two types: with and without leachant. The latter at first was proposed by Zavitsanos et al., they selected air or reducing gas as reacting atmosphere, and the desulfufization rates of 26.8—53.5% were obtained. It has substantial advantages

影响微波辐照脱硫过程因素的试验研究

应用微波辐照方法 ,采用单因子法考察了微波照射时间、煤粉粒径、浸提剂等因素对黄铁矿向磁黄铁矿转化效果的影响 .并应用正交试验考察各因素对黄铁矿转化效果的综合影响 ,优选出黄铁矿转化的最佳工艺条件为 :微波辐照 3min、加NaOH浸提剂、煤粉粒径为 0 .0 86～ 0 .10 2mm ,此时转化率可达到 4 5 .7%

微波预处理和微生物联合煤炭脱硫技术初探

将微波技术应用于微生物法煤炭脱硫,研究了煤粉粒径、煤浆浓度、初始pH值、嗜酸氧化亚铁硫杆菌(Acidi-thiobacillus ferrooxidans)接种量、微波辐照时间、脱硫周期等因素对微波预处理和微生物联合脱硫效果的影响,同时以单纯Acidithiobacillus ferrooxidans煤炭脱硫作对照。在煤样粒径为200目(<0.074 mm)、煤浆浓度为10%、初始pH为2.5、菌体接种量为10%、微波辐照时间3 min、脱硫周期4 d、温度30℃、摇床转速为160 r/min条件下,微波预处理和微生物联合作用对煤炭中全硫的脱除率可达51.3%。该结果表明,微波预处理和微生物联合煤炭脱硫技术可以大大缩短微生物脱硫周期,该研究结果可为开发新脱硫工艺提供参考。

微波辅助白腐真菌煤炭脱硫试验研究

将微波技术与生物技术相结合用于煤炭脱硫,采用微波功率1000 W、辐照时间80 s对煤样进行辐照处理后,考察了初始pH值、煤粉粒径和煤浆浓度对微波辅助白腐真菌脱硫效果的影响,以及脱硫过程中硫化物的转化规律。研究结果表明,微波辐照作用能够缩短脱硫周期,提高有机硫的脱除率。在初始pH值为4.5,煤粉粒径为80～120目,煤浆浓度为10%,浸出时间为3 d的条件下,煤中的全硫、无机硫和有机硫脱除率分别达到52.06%、51.61%和54.22%。

微波-化学方法除去原煤无机硫的穆斯堡尔谱研究

采用^(17)Fe穆斯堡尔谱学方法研究原煤中无机硫的形态和微波-化学方法脱硫的机理和规律.结果表明,煤中无机硫主要以黄铁矿形式存在.低铁硫酸盐则是原煤风化程度的一种表征;微波选择性介质加热,导致煤中黄铁矿与煤组分进行原位热化学反应,产生能溶于稀盐酸的铁硫化合物Fe_(1-x)S_x(0<x≤0.125)和FeS;适当增大微波辐照深度,使黄铁矿脱硫反应尽可能进行完全,再用稀盐酸处理,几乎能除尽煤中的无机硫.

金银花中绿原酸提取工艺的优化

对金银花中绿原酸的提取方法进行了比较研究,探讨了乙醇回流法的最佳提取方法和最佳工艺条件,并采用微波和酶液处理金银花以改进乙醇回流法。乙醇回流法最佳条件是加10倍量75%乙醇,回流提取1.5 h。对于乙醇回流法的改善,微波筛选的最佳工艺条件是:在600 W微波功率下,样品预浸时间24 h,辐射时间2 min。纤维素酶处理的酶用量为0.5%浓度2 mL,最适温度为40℃～50℃,最佳时间为3.0 h。试验表明:优选得到的工艺简单、稳定、可行,微波及酶液处理均能显著提高绿原酸的得率。

微波辐照增强原煤磁分离脱硫机理探讨

采用^(57)Fe穆斯堡尔谱学方法,研究微波-磁分离法脱硫机理及微波辐照深度对脱硫率的影响。结果表明,微波选择性介质加热,可以激励煤中顺磁性黄铁矿FeS_2热解,使其转化为非化学计量的磁黄铁矿Fe_(1-x)S(0<x≤0.125)和陨硫铁FeS;前者所含4C超结构相Fe_0.875S(即Fe_7S_8)具有亚铁磁性,极大地提高了无机硫矿物质的磁化率,因而增加原煤磁分离脱硫效果;适当控制微波辐照时间,使Fe_(1-x)S生成量最多,可得到最佳脱硫效果。

微波辐射法处理酸性黄染料废水的研究

采用微波辐射技术,建立了酸性黄染料废水的处理工艺,以颗粒活性炭为催化剂,考察了活性炭用量、微波辐射功率、微波辐射时间等因素对废水处理效果的影响.结果表明,质量浓度50mg/L的酸性黄染料废水50mL,活性炭用量2g,微波辐射功率800W,处理7min时,可以得到最佳的废水处理效果.

用穆斯堡尔方法研究辐照时间对原煤微波－磁脱硫的影响

穆斯堡尔谱分析表明：经磁场再分离后．全部磁黄铁矿携带部分非磁性的黄铁矿、硫酸亚铁、陨硫铁均被除去；适当控制辐照时间，使磁黄铁矿生成量达到最大时可得到最佳脱硫率；过深的辐照将使磁黄铁矿进一步分解为反铁磁性的陨硫铁．反而对磁分离脱硫不利。

微波辅助柠檬酸强化脱除煤炭中有机硫的实验研究

采用微波辅助柠檬酸强化脱除煤炭中的有机硫,考察了反应温度、微波辐照时间、柠檬酸浓度对有机硫去除的影响。结果表明,反应温度90℃,辐照时间420 s、柠檬酸浓度0.18 mol/L时,有机硫脱硫率为74.13%。脱硫后煤样的发热量仅降低0.23%,证明柠檬酸对煤的发热量影响极小。通过FTIR分析有机主体结构,仅在局部发生变化,硫醚、硫醇、亚砜类有机硫含量减少,柠檬酸对砜类有机硫无定向作用,磺酸基团被脱除。

温和条件下煤中有机硫的脱除

在超声波辐射或热处理条件下,考察碘甲烷对煤中有机硫的脱除效果,对碘甲烷和甲醇在煤中有机硫的脱除过程中的协同作用也进行了考察。随着碘甲烷用量的增加和加热时间的延长,有机硫的脱除率也随之增加。用GC/MS对脱除下来的有机硫化合物进行了检测。

微波辐照下煤的电化学脱硫研究

以北宿煤为原料,利用微波选择性加热的特点,考察了微波辐照时间、煤样粒径、NaOH等因素对高硫煤磁性强化磁选脱硫的影响,同时考察了微波-NaOH饱和溶液联合处理对北宿煤磁选脱硫的影响。研究表明,不同粒径的煤样的最大脱硫率存在一个最佳微波辐照时间,而微波-NaOH联合处理法脱硫效果更为显著。对煤样进行微波预处理后,可以根据需要控制NaOH饱和溶液用量达到较为理想的脱硫效果。

以稀碱和稀盐酸两步处理脱除煤中矿物质和硫——Ⅱ.脱硫作用及机理

选用兖州、东林和南桐高硫煤以稀碱和稀盐酸两步处理,在考察脱矿物质效果的同时研究了脱硫作用及机理。南桐煤全硫含量S_(td)为4.25%,在120～240℃以6W%NaOH水溶液处理,再在100℃以5W%HCl浸取,脱硫率从38.8%增加到62.4%,其中主要脱除的是S_s和S_p,S_o变化很小。当在370℃进行碱处理后,东林煤有机硫的脱除率达到50.6%,兖州煤则达到57.3%。文中还对无机硫和有机硫的脱除机理进行了初步研究。

活性焦脱硫脱硝技术及其改性方法研究进展

针对活性焦在烟气联合脱硫脱硝领域的广泛应用,介绍了活性焦脱硫脱硝技术及其反应机理,重点阐述了活性焦改性的反应机理及研究进展,包括酸碱改性、负载金属改性、高温热处理改性和微波改性。改性后活性焦的比表面积、孔道结构和表面化学官能团含量发生改变,使其脱硫脱硝性能提升。

复杂高硫煤化学脱硫试验研究

为降低复杂高硫煤中的全硫含量,采用有机溶剂萃取-稀硝酸处理两步法进行脱硫试验。在常温常压下,首先采用有机溶剂萃取脱除煤中的有机硫,再对萃取脱硫后的试样进行稀硝酸处理,以进一步脱除煤中的无机硫,降低试样硫分。试验结果表明,常温常压条件下,当原煤粒度为-200目、萃取剂为对甲酚、萃取时间为3 h时,煤样中的有机硫基本被完全脱除;对萃取脱硫后的试样进行1∶10稀硝酸处理脱硫,在试样粒度为-325目、搅拌速度300 r/min、反应时间2 h的条件下,最终产品硫分可由原煤6.28%降至0.73%,属于低硫煤。