Bituminous Ash Research Articles

Slagging-fouling evaluation of empty fruit bunch and palm oil frond mixture with bituminous ash coal as co-firing fuel

The empty fruit bunch (EFB) and palm oil frond mixture, called EFFR, can be utilized as co-firing fuel for coal-fired power plants to reduce carbon emissions. However, the addition of EFFR can influence the ash deposition characteristic of power plant fuel due to its high chlorine and alkali content. This study evaluates the slagging-fouling propensity of EFFR when blended with bituminous ash coal in several compositions. Theoretical methods using indices and the SCK ternary phase diagram, experimental procedure with drop tube furnace combustion, and ash observation methods utilizing visual and instrumental observations are carried out. The results show that co-firing EFFR can effectively reduce ash deposition. The slagging-fouling risk tendency slightly increases, adding up to 15 wt% EFFR has a higher slagging tendency, while the addition of 20 wt% EFFR has a higher fouling tendency. According to a thorough evaluation, co-firing 5–20 wt% EFFR with bituminous coal is still acceptable.

Perbandingan Data Hasil Metode B&W dan GWC untuk Klasifikasi Slagging Abu Batu Bara LRC

Slagging classification is generally listed in coal COA in coal trading transactions using one of the methods of determining slagging classification so that coal is ensured boiler friendly (low/medium classification). The paper aims to prove the tendency of two methods of determining slagging classification (B&W and GWC) on the results of certain classifications in LRC coal. The research method uses a quantitative method by collecting LRC coal COA data on a coal-fired steam power plant for a year of coal receipt (81 lots) issued by a laboratory that has been accredited by KAN (National Accreditation Committee). According to the method of GWC, ashes of entire lots are classified as LRC ash. While the method of B&W, there are 62 lots of ash classified as lignitic ash and 19 lots of ash classified as bituminous ash. This research has shown that the GWC method shows 79 lots of ash (97.53%) has low and medium classification and 2 lots of ash (2.47%) have a high classification; the method from B&W shows 19 lots of ash (23.46%) has a low classification and 62 lots of ash (76.54%) has a severe classification.

Electrodialytic recovery of rare earth elements from coal ashes

Rare earth elements (REE) are critical raw materials crucial for modern technologies and used in a variety of industries. There is a need of investment in REE recovery from secondary sources. The present work was designed to assess the potential of the electrodialytic process to recover REE from coal ash. The content of REE was evaluated in bituminous and anthracite ash. Anthracite presented higher REE concentration (447 ppm vs. 138 ppm) and a triple concentration of critical REE compared with bituminous ash. Anthracite ash was treated aiming to test the REE recover potential, including differences between light REE (LREE) and heavy REE (HREE) fractions as well as the specific recovery of REE with high criticality. A two-compartment electrodialytic cell was tested with the matrix placed in the anode compartment and a cation-exchange membrane separating the compartments. Experiments lasted a maximum of 7 days applying different current intensities and pH adjustment in the catholyte (≈ 2). Three main steps are observed in the removal process 1) REE solubilization - from the solid to the liquid phase (anolyte); 2) REE mobilization - movement from the anolyte towards the cathode end; 3) REE removal - presence in the catholyte. The extent of each step observed for the REE depends on their individual position in the periodic table with HREE removal being more regulated by step 1 and LREE by step 2. At the best tested conditions (50 mA, 3 days, pH adjustment), more than 70% of REE were extracted from the ash with the catholyte enclosing up to ≈ 50% of LREE and HREE. Combining the high criticality of neodymium with its high concentration in anthracite coal ash (65 ppm), the electrodialytic treatment is highly recommended to concentrate this REE in the catholyte. The results demonstrated the proof-of-concept for electro-assisted extraction of REE from anthracite coal ash, opening perspectives to a selective recovery of these elements from secondary sources.

The melting potential of various ash components generated from coal combustion: Indicated by the circularity of individual particles using CCSEM technology

This work aims to investigate the melting potential of various inorganic ash components by CCSEM (computer-controlled scanning electron microscopy). Three pulverized coals (anthracite YQ, bituminous coal DT and lignite CF) were burned in a drop tube furnace (DTF) at 1300°C in simulated air atmosphere to generate ashes. The contents, chemical compositions and particle circularity of each mineral species in coals and ashes were identified by CCSEM. On the basis of that, the spherical particle number ratio and the thermal behaviors of ash components and their original minerals were correlated to illustrate the melting potential of ash components. Typical results are presented as below: The slight increase of content of basic elements in mullite-like phase is the major reason for its partial melting. K Al-silicate in anthracite and lignite ashes is generated from illite and tends to be melted as the low melting point of illite, but K Al-silicate in bituminous ash is mainly formed from thermally stable quartz and is unable to be melted. Iron oxide derived from mainly excluded siderite in lignite CF is difficult to be melted but that from excluded pyrite in bituminous coal DT is melted moderately, that is because of the different melting behaviors of decomposition products of siderite and pyrite (FeO or FeO–FeS, respectively).

Use of Ash in Hot Dense Mixtures

Bituminous ash produced by the oil industry is used in landfill in large quantities. Recycling ashes coming from the oil industry can have signifi-cant benefits for the environment and is an attractive option for highway construction because it saves material acquisition and disposal costs. An experimental study was undertaken to investigate the use of these ashes as a replacement for mineral filler in hot-mix asphalt concrete. Physical tests were performed on the bituminous ash to determine its gradation, specific gravity, and chemical composition. Two cases were considered for determining the ash proportion. To evaluate the effect of a reduction in asphalt binder, ash with a maximum particle size of 0.074 mm [i.e., passing the Number (No.) 200 sieve] was used as a replacement for the asphalt cement content at percentages of 0 (i.e., control mix), 5, 10, and 15 by total asphalt weight. Also, ash was used as a replacement of the fine aggregate at percentages of 0, 30, 50, and 70 by total aggregate weight. In both cases, the ash came from thermal desorption in the hydrocarbon processes. Mix design was accomplished according to the Marshall mix design method (ASTM D1559). The results of these studies showed that use of ash passing the No. 4 sieve improved asphalt concrete characteristics while it reduced the use of aggregates when the asphalt proportion was 4.5%. Likewise, use of 0.8% fine ash (i.e., finer than the No. 200 sieve) to reduce the asphalt content in the hot dense mixture also improved the performance of asphalt concrete.

Sulphate Durability of Plain and Fly Ash Mortars

ABSTRACTSulphate expansion and strength tests were performed on mortars containing equal proportions of Type 10 (ASTM Type I) Portland cement and fly ash as the cementitious material. Two intermediate-Ca subbituminous ashes, one high-Ca subbituminous ash and one bituminous ash were tested. Control mortars manufactured with Types 10 and Type 50 (Type V ASTM) cements and one mortar containing 50% replacement of cement with limestone powder were also examined. The period and temperature of curing prior to sulphate exposure and the concentration and pH of the attacking solutions were other test parameters. Results indicate that the two intermediate-Ca subbituminous ashes from Alberta Canada, combined with Type 10 cement produce mortars that show excellent long-term strength, acceptable short term strength, and are highly resistant to attack by aggressive sulphate solutions. In some cases durability of these mortars was better than the control mortar made with Type 50 cement. On the other hand, mortar made using the high-Ca ash showed very high susceptibility to sulphate attack; at the same time, mortars made with this ash showed good strength development. Qualitative x-ray diffraction analysis indicates the presence of more lime, magnesium and iron bearing crystalline compounds in the high-Ca ash than in the Alberta ashes. These appear to be responsible for the poor performance in sulphate environments.

Correlations of Chemistry and Mineralogy of Western U.S. Fly Ash

Fly ashes derived from low-rank coals mined principally in Montana, Wyoming and North Dakota are being studied by the Western Fly Ash Research, Development and Data Center [1]. Previous studies of the mineralogy of western U.S. fly ash by McCarthy et al. [1–3] using x-ray diffraction (XRD) form the framework of the present study. A database of chemical, mineralogical and physical properties, along with precursor coal characteristics, is being assembled. Based on studies to date of several hundred fly ash samples derived from lignite and subbituminous coals, as well as from several bituminous ashes, correlations of chemistry and mineralogy have been hypothesized and are being tested. These correlations are discussed below.