Academic literature on the topic 'Fossil sinters'

Dominating globally and within Ukraine, the blast-furnace practice for iron production requires iron ore sintering preparation wherein the significant amount of fossil fuel is consumed, accompanied by harmful emissions into the environment. Pursuing the purpose to mitigate this negative impact, we address the promising direction of biomass utilisation for a partial replacement of fossil fuels in iron ore sintering. This paper considers the benefits of fossil fuels substitution with biomass, the world practice of biomass utilisation in iron ore sintering and the scope of the biomass energy potential in Ukraine. The study for obtaining sinters with the use of raw biomass fuels (sunflower husk, walnut shell) and charcoal has been carried out via lab-scale sintering pot. The influence of various biomaterials types on the process of iron ore sintering have been investigated and the obtained sinter quality in comparison with the conventional types of the fuels allows establishing the feasibility of replacing 25 % of coke breeze by charcoal or by walnut shell. The sunflower husk application is possible if preliminary preparation of the material for increasing bulk density is assumed to be carried out, for instance, by pressing.

<p class="AMSmaintext">Dominating globally and within Ukraine, the blast-furnace practice for iron production requires iron ore sintering preparation wherein the significant amount of fossil fuel is consumed, accompanied by harmful emissions into the environment. Pursuing the purpose to mitigate this negative impact, we address the promising direction of biomass utilisation for a partial replacement of fossil fuels in iron ore sintering. This paper considers the benefits of fossil fuels substitution with biomass, the world practice of biomass utilisation in iron ore sintering and the scope of the biomass energy potential in Ukraine. The study for obtaining sinters with the use of raw biomass fuels (sunflower husk, walnut shell) and charcoal has been carried out via lab-scale sintering pot. The influence of various biomaterials types on the process of iron ore sintering have been investigated and the obtained sinter quality in comparison with the conventional types of the fuels allows establishing the feasibility of replacing 25 % of coke breeze by charcoal or by walnut shell. The sunflower husk application is possible if preliminary preparation of the material for increasing bulk density is assumed to be carried out, for instance, by pressing.</p>

The Early Devonian Rhynie and Windyfield cherts of northeast Scotland originated as siliceous sinters deposited by hot springs. Silicification affected both subaerial and subaqueous environments, preserving a diverse terrestrial and freshwater biota. Cherts originally deposited in small shallow pools can be recognised on the basis of both texture and fossil content. Textures comprise clotted and microcoprolitic textures, bacterial coatings on plant axes that can be stromatolitic, and a variety of bacterial and fungal meshworks. The crustacean Lepidocaris, the euthycarcinoid Heterocrania, the charophyte alga Palaeonitella, and chytrid fungi are typical elements of the aquatic biota. Observations of modern hot springs in Yellowstone National Park, Wyoming, U.S.A., demonstrate that shallow ponds and streams on low-angle outwash areas and dormant vent orifices provide suitable environmental analogues. Textures comparable to those described from Rhynie are recorded from Yellowstone sinters, but examples of the rapid and complete silicification of delicate organic structures as seen in a few of the Rhynie chert beds have not been noted. Petrographic textures comparable to those seen in the cherts of freshwater origin from Rhynie occur in modern stream sinters at Yellowstone, where they form from waters at 20–28 °C and with a pH of 8.7. This similarity occurs despite differences in environment at Yellowstone, such as the oxidizing surface environment, water table fluctuations, complex modern vegetation, fixing of silica by diatoms, and climatic extremes. Thus there are close similarities between textures seen in the Rhynie cherts and Yellowstone sinters deposited in freshwater pools and streams by hot springs.

The Early Devonian Rhynie cherts represent the surface deposits of a subaerial hot spring system. Historically palaeobotanists have studied the exceptionally preserved early land plants contained within the cherts by mounting thin sections of the rock on glass microscope slides. Investigation of plant morphology and life habitat has relied on reconstruction from consecutive serial sections with the inherent loss of information at the blade width scale. Here we detail the previously unrealised potential for some of the Rhynie chert beds to respond well to mechanical preparation. Recognition that some chert beds may be prepared in this way provides an additional technique for the continued investigation of the flora and fauna of this important fossil locality. The technique might find wider application in the investigation of other more recently discovered fossil-bearing sinters worldwide.

The Ixtacamaxtitlán area in northern Puebla (central Mexico) contains middle Miocene Cu-Mo-Au porphyry/skarn and Pliocene low-sulfidation Au-Ag epithermal deposits that are geologically associated with the evolution of the Trans-Mexican Volcanic Belt (TMVB). In this paper, a new 40Ar/39Ar age (2.87 ± 0.41 Ma) is provided for rhombohedral alunite from a kaolinite + alunite ± opal ± cristobalite ± smectite advanced argillic alteration assemblage. This age contributes to the definition of a metallogenic province that is confined to the TMVB, a relevant feature for regional exploration. A ~12 My gap is established between the formation of the Cu-Mo-Au porphyry/skarn and low-sulfidation Au-Ag epithermal deposits, which rules out the possibility that their overlapping was the result of telescoping. Advanced argillic alteration is conspicuous throughout the mineralized area. This alteration assemblage consists of a widespread kaolinite-rich blanket that underlies silica sinters, polymictic hydrothermal breccias, and an alunite-rich spongy layer that consists of vertical tubular structures that are interpreted as the result of gas venting in a subaerial environment. The above indicate a shallow hypogene origin for the advanced argillic alteration assemblage—that is, formation by the partial condensation within a phreatic paleoaquifer of acidic vapors that were boiled-off along fractures that host epithermal veins at depth. The formation of the spongy alunite layer and silica sinters is interpreted to have been synchronous. Within the alunite-rich spongy layer, tubular structures hosted microbial consortia dominated by fungi and possible prokaryote (Bacteria or Archaea) biofilms. Such consortia were developed on previously formed alunite and kaolinite and were preserved due to their replacement by opal, kaolinite, or alunite. This means that the proliferation of fungi and prokaryotes occurred during a lull in acidic gas venting during which other organisms (i.e., algae) might have also prospered. Periodic acidic gas venting is compatible with a multi-stage hydrothermal system with several boiling episodes, a feature typical of active geothermal systems and of low-sulfidation epithermal deposits. The microstructures, typical for fungi, are mycelia, hyphae with septa, anastomoses between branches, and cord-like groupings of hyphae. Possible evidence for skeletal remains of prokaryote biofilms is constituted by cobweb-like microstructures composed of <1 µm thick interwoven filaments in close association with hyphae (about 2.5 µm thick). Bioweathering of previously precipitated minerals is shown by penetrative biobrecciation due to extensive dissolution of kaolinite by mycelia and by dissolution grooves from hyphae on alunite surfaces. Such bioweathering was possibly predated by inorganically driven partial dissolution of alunite, which suggests a lull in acidic gas venting that allowed living organisms to thrive. This interpretation is sustained by the occurrence of geometrical dissolution pits in alunite covered by hyphae. Fungal bioweathering is particularly aggressive on kaolinite due to its relatively poor nutrient potential. Such delicate microstructures are not commonly preserved in the geological record. In addition, numerous chalcopyrite microcrystals or microaggregates are found within the alunite layer, which could be related to sulfate reduction due to bacterial activity from the sulfate previously released by fungal bioweathering of alunite. Hydrogeochemical modeling constrains pH to between ~3.2 and ~3.6 and temperature to between 53 and 75 °C during the stage in which fungi and other organisms thrived. These waters were cooler and more alkaline than in earlier and later stages, which were characterized dominantly by steam-heated waters. The most likely process to account for this interlude would be mixing with meteoric water or with upwelling mature water that did not undergo boiling.

Insects are the most diverse macroorganismic group to ever inhabit the planet, constituting a major share of the animal biomass in terrestrial and freshwater ecosystems. Since their first appearance in the fossil record some 400 million years ago, they have expanded ecologically into almost every niche except the ocean below the photic zone. When fossilized, their chitinous exoskeletons typically are well preserved, as evidenced by a respectable fossil record. They are found notably in lacustrine shales and amber but also occur in siderite nodules, lithographic limestone, sinter deposits, asphalt, and various glacial deposits. Insect fossils are major subjects in phylogenetic studies but are used to a lesser extent in understanding past ecological associations and reconstruction of ancient environments.

The Improvement of Calcium Oxide Catalyst for Biodiesel Synthesis The development of industrial’s sector resulted in increasing demand for fuel. Fuel used is obtained from fossil fuel which is limited, and it produces several harmful gases to environment. To overcome these obstacles, the research on alternative energy resources has begun. Biodiesel has become more attractive because of its environmental benefits and it is made from renewable resources. Biodiesel is produced from vegetable oil by transesterification reaction. The aim of this research is development of CaO become super base CaO as heterogeneous for biodiesel synthesis by transesterification. The activities of both catalysts were tested by transesterification reaction in batch reactor at 60–65 oC for 4 hours. Both of those catalysts were characterized; include crystallinity by XRD, strength of base and surface area by BET method. Those solids have the basic strength about 10–11, crystalline structures, and the surface area of super base CaO about 7.7 m2/g and CaO about 9.6 m2/g. The content of methyl ester in biodiesel produced reaches 98.8%. According to SNI (minimal 96.5 %-wt) and ASTM, biodiesel of this reaction can be used as renewable energy source. Keywords: CaO, super base CaO, transesterification, biodiesel Abstrak Berkembangnya industri di dunia mengakibatkan meningkatnya kebutuhan akan bahan bakar. Selama ini bahan bakar yang digunakan diperoleh dari bahan bakar fosil yang jumlahnya terbatas, terlebih lagi hasil pembakaran bahan bakar fosil cenderung tidak ramah lingkungan. Untuk mengatasi berbagai kendala yang ditimbulkan dari penggunaan bahan bakar fosil, penelitian terhadap sumber energi alternatif mulai dilakukan. Biodiesel menarik perhatian dunia karena hasil pembakarannya lebih ramah lingkungan dan berasal dari sumber yang terbarukan. Biodiesel dihasilkan dari minyak nabati melalui reaksi transesterifikasi.Penelitian ini mengembangkan katalis CaO menjadi katalis CaO super basa untuk reaksi transesterifikasi pembentukan biodiesel. Aktivitas katalis CaO dan katalis CaO super basa tersebut diuji melalui reaksi transesterifikasi di dalam reaktor partaian pada suhu 60–65 oC selama 4 jam. Karakterisasi padatan meliputi uji kristalinitas dengan metode XRD, uji kekuatan basa, dan uji luas permukaan dengan metode BET. Hasil penelitian menunjukkan bahwa padatan memiliki kekuatan basa berkisar 10–11, bersifat kristalin, dan memiliki luas permukaan sebesar 7,7 m2/g untuk CaO super basa dan 9,6 m2/g untuk CaO. Kadar metil ester biodiesel yang dihasilkan mencapai 98,8%. Kadar metil ester menurut SNI (minimal 96,5 %-b) dan ASTM, biodiesel dari reaksi ini dapat digunakan sebagai sumber energi terbarukan. Kata Kunci: CaO, CaO super basa, transesterifikasi, biodiesel

In the iron-ore-sintering process, the use of biomass charcoal instead of coke breeze can reduce the emission of flue gas pollutants and alleviate the energy crisis of fossil fuels. However, the direct application of biomass charcoal to iron ore sintering is bound to affect the sinter properties. The effects of biomass charcoal addition on the sintering ore properties and flue gas pollutants emission were studied through sintering cup and related performance test experiments. Meanwhile, the influence mechanism of biomass charcoal instead of coke breeze on iron ore sintering was expounded. The experimental results show that with an increase in biomass charcoal, the vertical sintering rate increased, the internal pore structure developed rapidly, and the pollutant emission decreased gradually. When the biomass charcoal content was less than 40%, the sinter strength and yield were stable and slightly improved with the increase in biomass charcoal. When the biomass charcoal content was higher than 40%, the metallurgical properties of sinter degraded sharply, making it difficult to meet the production requirements. The comprehensive effect of biomass charcoal on the sinter suggests that the suitable biomass charcoal addition was 40%; under this condition, the reduction in SO2 and NOx was 28.2% and 25.7%, respectively.

The question of what composed the Earth's oldest fossils is the subject of current debate. At present, taphonomical determination of Archean silicified microfossils is largely based on morphological comparisons with extant microorganisms. This method has significant shortcomings because little is known about which types of bacteria silicify, what physical changes are induced on those species during mineralization, and, most importantly, what their preservation potential is. Terrestrial hot springs may help resolve these uncertainties because the silica-supersaturated geothermal fluids mineralize a wide variety of natural microbial communities and thus lead to the formation of numerous distinct biofacies. Some of these biofacies are reminiscent of Archean siliceous stromatolites from which the oldest microfossils were recovered. We suggest that by integrating molecular techniques that characterize the indigenous microbial populations growing in different biofacies with electron microscopy, we may be able to assess better what types of ancient microbes could have become fossilized.