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《Fuel Processing Technology》2001,72(3):185-198
The dry beneficiation of three types of Slovakian brown coal, namely Ci'gel, Handlova', and Nova'ky coal was conducted via triboelectrostatic separation. Three different types of separators—parallel plate, cylindrical and louvered plate—were used for this study. It was found that a parallel plate separator could reduce the ash contents of Ci'gel and Handlova' coals. The poor quality of separation for the Nova'ky coal studied is probably due to the particle–particle interactions and surface oxidation states of the coal. 相似文献
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In this study, a new concurrent flotation column that simulates the plug flow reactor was designed with the use of a static mixer, a froth separator column and an optional additional bubble generator for fly ash beneficiation. The objective was to improve the efficiency and effectiveness of unburned carbon removal from fly ash by minimizing energy costs. Cleaning tests were performed with and without the additional bubble genarator. Without the additional bubble generator unburned carbon in the ash product could be reduced to only 2.53%. Incidental loss of carbon particles and insufficient bubble generation were the main causes of poor carbon separation performance. By turning on the additional bubble generator it was aimed to assist bubble generation, to compensate bubble rupture and to recapture the detached or free carbon particles leaving the froth phase. With the additional bubble generator and under optimized conditions a froth product with 95% carbon recovery and a cleaned ash product with less than 1% unburned carbon was obtained. The separation process through the static mixer (feeder) and the separator column and the energy consumption of the unit were analyzed. It was seen that around 80% energy could be saved with the concurrent flotation column compared to conventional flotation. 相似文献
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Influence of fly ash fineness on strength, drying shrinkage and sulfate resistance of blended cement mortar 总被引:4,自引:0,他引:4
In this paper, the influence of fineness of fly ash on water demand and some of the properties of hardened mortar are examined. In addition to the original fly ash (OFA), five different fineness values of fly ash were obtained by sieving and by using an air separator. Two sieves, Nos. 200 and 325, were used to obtain two lots of graded fine fly ash. For the classification using air separator, the OFA was separated into fine, medium and coarse portions. The fly ash dosage of 40% by weight of binder was used throughout the experiment. From the tests, it was found that the compressive strength of mortar depended on the fineness of fly ash. The strength of mortar containing fine fly ash was better than that of OFA mortar at all ages with the very fine fly ash giving the highest strength. The use of all fly ashes resulted in significant improvement in drying shrinkage with the coarse fly ash showing the least improvement owing primarily to the high water to binder ratio (W/B) of the mix. Significant improvement of resistance to sulfate expansion was obtained for all fineness values except for the coarse fly ash where greater expansion was observed. The resistance to sulfuric acid attack was also improved with the incorporation of all fly ashes. In this case the coarse fly ash gave the best performance with the lowest rate of the weight loss owing probably to the better bonding of the coarse fly ash particles to the cement matrix and less hydration products. It is suggested that the fine fly ash is more reactive and its use resulted in a denser cement matrix and better mechanical properties of mortar. 相似文献
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The gas transport, triboelectrostatic beneficiation of coal combustion fly ash into carbon-rich and ash-rich products was studied relative to the effect of ash surface moisture. Increasing the humidity to which the ashes from American and Italian coal-fired utilities were exposed under process and ambient conditions affected carbon and ash separability. The effect of humidity and particle surface moisture became more important as particle size decreased: particles greater than 75 μm in diameter were nearly unaffected whereas particles smaller than 45 μm experienced up to a four-fold change in their separability upon changing their surface moisture contents. Although particle size influences the moisture adsorption, which in turn affects tribocharging, the decrease in adhesive forces between carbon and ash from otherwise intractable clusters during drying also may be a factor influencing triboelectrostatic beneficiation performance. 相似文献
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为提高粉煤灰的综合利用率,减少资源浪费,利用传导感应电选试验台进行粉煤灰分选试验研究,通过改变极板板型、极板电压、极板间距、颗粒粒径等参数研究分选效果的影响因素,对分选产物进行对比。研究结果表明:凹型电极板的碳分选效果相对优于凸型电极板;精灰烧失量随电压增加呈先上升后降低的趋势;板间距增大会削弱板间电场强度及影响颗粒运动;粒径越小灰的烧失量越低,且不易分选。对分选产物分析表明,对于粒径48μm的粉煤灰分选效果较为理想,而对于细灰的效果则欠佳。分选中精灰烧失量最大可达21.89%,碳回收率最高达53.02%。 相似文献
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通过筛分和破碎两种方式分别获得粒径区间为0.6~1.18 mm、0.3~0.6 mm的粉煤灰渣,并用其等体积替代对应粒径区间的细骨料,分析粉煤灰渣对砂浆工作性和强度的影响,探究粉煤灰渣的最优替代粒径区间。结合扫描电镜(SEM)、能谱分析(EDS)等方法分析了粉煤灰渣替代细骨料后砂浆试件的强度变化机理。基于砂浆最优替代粒径区间结果,验证了砂浆混凝土试件的强度和抗冻性。研究结果表明:分别以筛分方式和破碎方式得到的0.3~0.6 mm粒径区间粉煤灰渣替代对应区间细骨料后,其砂浆试件强度均与基准组(未替代)基本一致;而以筛分方式得到的0.3~0.6 mm粒径区间粉煤灰渣替代对应区间细骨料后,其混凝土试件强度和抗冻性与基准组基本一致。在水泥提供的氢氧化钙环境下粉煤灰渣表面生成水化硅酸钙,从而增加了水泥和粉煤灰渣界面胶结强度,强化水泥与粉煤灰渣界面区域,凹凸不平的粉煤灰渣表面与水泥浆咬合嵌锁,保证了试件的强度。 相似文献
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Triboelectrostatic separation of fly ash and charge reversal 总被引:1,自引:0,他引:1
John P. Baltrus 《Fuel》2002,81(6):757-762
Triboelectrostatic separation has been investigated as a method for separating unburned carbon from coal combustion fly ash. It was found that when a fly ash is exposed to moisture before it undergoes separation, the charging properties of the components of the fly ash change significantly. The mineral and carbon components of the fly ash appear to charge oppositely to how they were charged before exposure to moisture. A correlation was found between the degree of charge reversal and the relative amounts of leachable ions, especially calcium and sodium ions, present on the surface of the ash. 相似文献
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This paper investigated the characteristics of inorganic elements in ashes from biomass gasification power generation (BGPG) plant. The ash samples of the gasifier ash, separator ash and wet scrubber ash were collected in a 1 MW circulating fluidized bed (CFB) wood gasification power generation plant. Particle size distribution of ashes was determined by gravimetric measurement and super probe analyzer. The concentrations of trace elements and major ash-forming elements, such as As, Al, Ca, Cd, Cr, Cu, K, Mg, Na, Ni, Pb, Ti in different ashes as a function of particle size were determined by Inductive Coupled Plasma Spectrometer. The concentrations and distribution coefficient and enrichment factors of the inorganic elements in ashes were studied. X-ray fluorescence spectrometer and X-ray powder diffraction were used to provide information on the characteristics of the ashes. The results showed that most of the trace elements had an enrichment tendency in the finer size particles. A considerable amount of the ashes was residual carbon. Most of the volatile e.g. halogen elements and alkali elements existed mainly in wet scrubber ash and enriched in fly ash. Most of the Si, Ni, Pb, Zn, Cr, Cd were found in separator ash, indicating an enrichment of heavy metal elements in separator ash. K, S, Mn, Cu mainly existed in gasifier ash. 相似文献
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通过分析循环流化床锅炉粉煤灰的特点,得出需水量及烧失量过高是制约飞灰分选的关键。为了改善粉煤灰活性,降低飞灰含碳量,并控制额外投资成本,是实现粉煤灰综合利用的新途径。 相似文献
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This study was to investigate the catalytic effect of inorganic compositions present in fly ash carbons, high-unburned-carbon content fly ashes from coal-fired power plants, on the development of surface area during steam activation. Through this work, the relationships between the concentrations of alkali metals (Na and K) and a mixture of metals, Na-K-Ca and Na-K-Fe, in fly ash carbon and the surface areas of the produced activated carbon were studied.Six fly ash carbons were selected as feedstocks for activated carbon. SEM/EDS studies showed that there are two groups of inorganic particles present in fly ash carbons, in terms of the way they are associated with carbon particles: inorganic particles that exist as free single particles, and inorganic particles that are combined with the carbon particles. A series of froth flotation tests was conducted to separate the individual inorganic particles from the fly ash carbons. The concentration of the inorganic particles was analyzed using ICP-AES before and after froth flotation separation. Studies showed that the Na-K, Na-K-Ca, and Na-K-Fe which are combined with carbon particles had catalytic effects on the development of the surface areas of activated carbons. The higher the concentration of these catalytic particles, the more significant effects they had on the development of the surface areas with increasing carbon burn-off levels. 相似文献
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This study covers the triboelectrostatic separation of Polyvinylchloride (PVC) materials from mixed plastics such as polyethylene
terephthalate (PET), polyethylene (PE), polypropylene (PP), and polystyrene (PS). The PVC material generates hazardous hydrogen
chloride gas resulting from the combustion in the incinerators. The laboratory scale triboelectrostatic separation system
consists of a fluidized-bed tribocharger, a separation chamber, a collection chamber and a controller. Negative and positive
surface charges can be imparted to the PVC and PET particles, respectively, due to the difference of triboelectric charging
series between the particles in the fluidized-bed tribocharger. They can be separated by passing through an external electric
field. A highly concentrated PVC (91.9%) can be recovered with a yield of about 96.1% from the mixture of PVC and PET materials
in a single stage of processing. For the removal of PVC from the two-component mixed plastics such as PVC/PET, PVC/PP, PVC/PE
or PVC/PS, separation results show the recovery of 96–99% with the pure extract content in excess of 90%. The triboelectrostatic
separation system using the fluidized-bed tribocharger shows the potential to be an effective method for removing PVC from
mixed plastics for waste plastic recycling. 相似文献
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针对粉煤灰中未燃炭含量过高不利于大规模综合利用的问题,从理论上分析了浮选回收粉煤灰中未燃炭的基本原理,采用全浮选流程对粉煤灰中未燃炭进行了浮选回收试验,探讨了影响粉煤灰中未燃炭浮选效果的主要因素,确定了适宜的工艺条件。试验结果表明,采用全浮选流程可以使粉煤灰中可燃物降至4.1%左右。 相似文献