Showing papers on "Coal published in 2015"

The geographical distribution of fossil fuels unused when limiting global warming to 2 °C

Abstract: Policy makers have generally agreed that the average global temperature rise caused by greenhouse gas emissions should not exceed 2 °C above the average global temperature of pre-industrial times. It has been estimated that to have at least a 50 per cent chance of keeping warming below 2 °C throughout the twenty-first century, the cumulative carbon emissions between 2011 and 2050 need to be limited to around 1,100 gigatonnes of carbon dioxide (Gt CO2). However, the greenhouse gas emissions contained in present estimates of global fossil fuel reserves are around three times higher than this, and so the unabated use of all current fossil fuel reserves is incompatible with a warming limit of 2 °C. Here we use a single integrated assessment model that contains estimates of the quantities, locations and nature of the world's oil, gas and coal reserves and resources, and which is shown to be consistent with a wide variety of modelling approaches with different assumptions, to explore the implications of this emissions limit for fossil fuel production in different regions. Our results suggest that, globally, a third of oil reserves, half of gas reserves and over 80 per cent of current coal reserves should remain unused from 2010 to 2050 in order to meet the target of 2 °C. We show that development of resources in the Arctic and any increase in unconventional oil production are incommensurate with efforts to limit average global warming to 2 °C. Our results show that policy makers' instincts to exploit rapidly and completely their territorial fossil fuels are, in aggregate, inconsistent with their commitments to this temperature limit. Implementation of this policy commitment would also render unnecessary continued substantial expenditure on fossil fuel exploration, because any new discoveries could not lead to increased aggregate production.

Reduced carbon emission estimates from fossil fuel combustion and cement production in China

Abstract: Nearly three-quarters of the growth in global carbon emissions from the burning of fossil fuels and cement production between 2010 and 2012 occurred in China. Yet estimates of Chinese emissions remain subject to large uncertainty; inventories of China's total fossil fuel carbon emissions in 2008 differ by 0.3 gigatonnes of carbon, or 15 per cent. The primary sources of this uncertainty are conflicting estimates of energy consumption and emission factors, the latter being uncertain because of very few actual measurements representative of the mix of Chinese fuels. Here we re-evaluate China's carbon emissions using updated and harmonized energy consumption and clinker production data and two new and comprehensive sets of measured emission factors for Chinese coal. We find that total energy consumption in China was 10 per cent higher in 2000-2012 than the value reported by China's national statistics, that emission factors for Chinese coal are on average 40 per cent lower than the default values recommended by the Intergovernmental Panel on Climate Change, and that emissions from China's cement production are 45 per cent less than recent estimates. Altogether, our revised estimate of China's CO2 emissions from fossil fuel combustion and cement production is 2.49 gigatonnes of carbon (2 standard deviations = ±7.3 per cent) in 2013, which is 14 per cent lower than the emissions reported by other prominent inventories. Over the full period 2000 to 2013, our revised estimates are 2.9 gigatonnes of carbon less than previous estimates of China's cumulative carbon emissions. Our findings suggest that overestimation of China's emissions in 2000-2013 may be larger than China's estimated total forest sink in 1990-2007 (2.66 gigatonnes of carbon) or China's land carbon sink in 2000-2009 (2.6 gigatonnes of carbon).

Drivers of the US CO2 emissions 1997-2013.

Abstract: Fossil fuel CO2 emissions in the United States decreased by ∼11% between 2007 and 2013, from 6,023 to 5,377 Mt. This decline has been widely attributed to a shift from the use of coal to natural gas in US electricity production. However, the factors driving the decline have not been quantitatively evaluated; the role of natural gas in the decline therefore remains speculative. Here we analyse the factors affecting US emissions from 1997 to 2013. Before 2007, rising emissions were primarily driven by economic growth. After 2007, decreasing emissions were largely a result of economic recession with changes in fuel mix (for example, substitution of natural gas for coal) playing a comparatively minor role. Energy-climate policies may, therefore, be necessary to lock-in the recent emissions reductions and drive further decarbonization of the energy system as the US economy recovers and grows.

Enrichment of U–Se–Mo–Re–V in coals preserved within marine carbonate successions: geochemical and mineralogical data from the Late Permian Guiding Coalfield, Guizhou, China

Abstract: We present multi-element data on the super-high-organic-sulfur (SHOS; 5.19 % on average) coals of Late Permian age from Guiding, in Guizhou Province, China. The coals, formed on restricted carbonate platforms, are all highly enriched in S, U, Se, Mo, Re, V, and Cr, and, to a lesser extent, Ni and Cd. Although the Guiding coals were subjected to seawater influence, boron is very low and mainly occurs in tourmaline and mixed-layer illite/smectite. Uranium, Mo, and V in the coal are mainly associated with the organic matter. In addition, a small proportion of the U occurs in coffinite and brannerite. The major carrier of Se is pyrite rather than marcasite. Rhenium probably occurs in secondary sulfate and carbonate minerals. The U-bearing coal deposits have the following characteristics: the formation age is limited to Late Permian; concentrations of sulfur and rare metals (U, Se, Mo, Re, V, and in some cases, rare earth elements and Y) are highly elevated; the U-bearing coal beds are intercalated with marine carbonate rocks; organic sulfur and rare metals are uniformly distributed within the coal seams; and the combustion products (e.g., fly and bottom ash) derived from the coal deposits may have potential economic significance for rare metals: U, Se, Mo, Re, V, rare earth elements, and Y.

Conversion of the greenhouse gas CO2 to the fuel gas CO via the Boudouard reaction: A review

Abstract: The remediation of carbon dioxide emitted into the atmosphere has become the topic of the day due to the enormous contribution of CO 2 to the devastating global warming. The Boudouard reaction, in which solid carbon (char) reacts with CO 2 to produce carbon monoxide (CO 2 (g)+C(s)↔CO (g)), is a straightforward route for the CO 2 emission mitigation. Through this reaction, the CO 2 coming from variety of combustion plants, including exhaust/flue gas and synthesis gas, can be upgraded to the fuel gas, CO. This work presents a review on the CO 2 gasification of char, from coal, biomass, municipal solid wastes, sewage sludge or any co-utilized blend of them, to produce CO through the Boudouard reaction. An outline of the most effective parameters on the char gasification rate is presented. The parameters which affect the char reactivity are reviewed as those related to the char and its structural features (surface area and porosity, active sites, mineral content, structural evolution of char during gasification, pyrolysis condition and carbon source) and operation parameters (use of catalyst, gasification temperature, gasification pressure and CO 2 partial pressure, char particle size and gasification heat source). The kinetics of the char gasification reaction is studied and several theoretical or semi-empirical kinetic models used to interpret the reaction rate data and calculation of kinetic parameters, specifically activation energy, are reviewed and discussed.

Coal fly ash as a resource for rare earth elements.

Abstract: Rare earth elements (REE) have been recognised as critical raw materials, crucial for many clean technologies. As the gap between their global demand and supply increases, the search for their alternative resources becomes more and more important, especially for the countries which depend highly on their import. Coal fly ash (CFA), which when not utilised is considered waste, has been regarded as the possible source of many elements, including REE. Due to the increase in the energy demand, CFA production is expected to grow, making research into the use of this material a necessity. As Poland is the second biggest coal consumer in the European Union, the authors have studied different coal fly ashes from ten Polish power plants for their rare earth element content. All the fly ashes have a broadly similar distribution of rear earth elements, with light REE being dominant. Most of the samples have REE content relatively high and according to Seredin and Dai (Int J Coal Geol 94: 67–93, 2012) classification can be considered promising REE raw materials.

Nonrenewable energy, renewable energy, carbon dioxide emissions and economic growth in China from 1952 to 2012

Abstract: This paper mainly investigates the relationship among energy consumption, carbon emissions and economic growth in China from 1952 to 2012 First, we implement unit root and cointegration analysis to test the stationary Furthermore, we analyze the mutual influence among energy consumption, carbon emissions and economic growth through Granger causality analysis Next, we also conduct static and dynamic regression analysis on the determinants of carbon emissions and economic growth Last, we predict the future influence of different energy consumption on carbon emissions and economic growth We find that coal has dominant impact on economic growth and carbon emissions GDP (Gross Domestic Product) has bi-directional relationship with CO2 (carbon dioxide) emission, coal, gas, and electricity consumption It is imperative to change energy consumption structure in China We had better decrease coal consumption rate It is significant to develop hydro and nuclear power in China

Energy Dissipation and Release During Coal Failure Under Conventional Triaxial Compression

Abstract: Theoretical and experimental studies have revealed that energy dissipation and release play an important role in the deformation and failure of coal rocks. To determine the relationship between energy transformation and coal failure, the mechanical behaviors of coal specimens taken from a 600-m deep mine were investigated by conventional triaxial compression tests using five different confining pressures. Each coal specimen was scanned by microfocus computed tomography before and after testing to examine the crack patterns. Sieve analysis was used to measure the post-failure coal fragments, and a fractal model was developed for describing the size distribution of the fragments. Based on the test results, a damage evolution model of the rigidity degeneration of coal before the peak strength was also developed and used to determine the initial damage and critical damage variables. It was found that the peak strength increased with increasing confining pressure, but the critical damage variable was almost invariant. More new cracks were initiated in the coal specimens when there was no confining pressure or the pressure was too high. The parameters of failure energy ratio β and stress drop coefficient α are further proposed to describe the failure mode of coal under different confining pressures. The test results revealed that β was approximately linearly related to the fractal dimension of the coal fragments and that a higher failure energy ratio corresponded to a larger fractal dimension and more severe failure. The stress drop coefficient α decreased approximately exponentially with increasing confining pressure, and could be used to appropriately describe the evolution of the coal failure mode from brittle to ductile with increasing confining pressure. A large β and small α under a high confining pressure were noticed during the tests, which implied that the failure of the coal was a kind of pseudo-ductile failure. Brittle failure occurred when the confining pressure was unloaded—an observation that is important for the safety assessment of deep mines, where a high in situ stress might result in brittle failure of the coal seam, or sudden outburst.

Supercritical water gasification research and development in China

Abstract: Supercritical water gasification is a promising technology to convert coal/biomass/organic wastes to hydrogen cleanly and efficiently Extensive investigations on supercritical water gasification were conducted in China State Key Laboratory of Multiphase Flow in Power Engineering (SKLMFPE) together with other universities/institutes established experimental device with the reactor type of quartz tube reaction system, tubular reactor and fluidized bed reactor The fluidized bed reactor system solved the blocking problems to guarantee continuous and stable gasification Typically Hongliulin coal as a typical coal in China was completely gasified in supercritical water fluidized bed system and the hydrogen yield was 775 mol per kg of coal A pilot scale demonstration plant for supercritical water gasification driven by solar concentration system was established with a handling capacity of 1 t/h and it proves the feasibility of the system scale up A novel thermodynamics cycle power generation system based on coal gasification in supercritical water was proposed with the obvious advantages of high coal-electricity efficiency and zero pollutant emission An Integrated Cooperative Innovation Center with the name of A New Type of High-efficient Coal Gasification Technology and its Large-scale Utilization was founded in order to vigorously enhance the industrialization of the technology

A Review of the Occurrence and Promising Recovery Methods of Rare Earth Elements from Coal and Coal By-Products

Abstract: Previous research indicates that coal and coal by-products are a potential source of critical elements including rare earth elements (REE) with estimated amounts in the range of 50 million metric tons. Despite the proven presence of elevated REE concentrations, commercial extraction and recovery have not been realized. This article provides a review of the abundance, mode of occurrence, and recovery methods of rare earth elements in coal and coal by-products. The feasibility of using established REE extraction and recovery technologies is discussed along with issues associated with their use with coal resources.