Atmospheric Chemistry Modelling of Amine Emissions from Post Combustion CO2 Capture Technology

Emissions from post combustion CO2 capture plants using amine solvents are of concern due to their adverse impacts on the human health and environment. Potent carcinogens such as nitrosamines and nitramines resulting from the degradation of the amine emissions in the atmosphere have not been fully investigated. It is, therefore, imperative to determine the atmospheric fate of these amine emissions, such as their chemical transformation, deposition and transport pathways away from the emitting facility so as to perform essential risk assessments. More importantly, there is a lack of integration of amine atmospheric chemistry with dispersion studies. In this work, the atmospheric chemistry of the reference solvent for CO2 capture, monoethanolamine, and the most common degradation amines, methylamine and dimethylamine, formed as part of the post combustion capture process are considered along with dispersion calculations. Rate constants describing the atmospheric chemistry reactions of the amines of interest are obtained using theoretical quantum chemistry methods and kinetic modeling. The dispersion of these amines in the atmosphere is modeled using an air-dispersion model, ADMS 5. A worst case study on the UK's largest CO2 capture pilot plant, Ferrybridge, is carried out to estimate the maximum tolerable emissions of these amines into the atmosphere so that the calculated concentrations do not exceed guideline values and that the risk is acceptable

An investigation into the stress-permeability relationship of coals and flow patterns around working longwall faces

This research aimed to establish a physical relationship between applied stress and permeabilities of different coals. Seven different coals, ranging from medium volatile to high volatile bituminous, were tested for stress-permeability relationship under simulated subsurface stress conditions. Prior to the experimental investigations, the stress conditions around a working longwall face were considered in order to achieve an accurate simulation of the stresses experienced underground. Laboratory stress-permeability experiments were carried out by passing nitrogen gas through a triaxially stressed cylindrical coal specimen. A slightly modified conventional triaxial testing apparatus was used for this purpose. The stress conditions employed simulated the stresses created in the front abutment zone, the crushing zone, the stress relief zone and the recompaction zone of a working longwall face. A number of specimens of the seven different coals were tested under such stress conditions and stress-permeability curves were obtained for each specimen. The effect of moisture and the direction of gas flow in relation to the direction of bedding planes and major fracture lines were also considered in laboratory investigations. A relationship between the stress-permeability behaviour and the rank of coals used was established. Combining the general pattern of stress-permeability behaviour obtained in this research together with the stress conditions created around a working longwall face a model was produced which presents the stress-permeability profiles of coal seams in the vicinity of the workings. From these profiles it was possible to suggest the flow patterns of gas around working longwall faces

Implementation of horizontal well CBM/ECBM technology and the assessment of effective CO2 storage capacity in a Scottish coalfield

Acknowledgements The authors wish to thank Composite Energy Ltd., the BG Group, Scottish Power and the Royal Bank of Scotland for their funding and contributions towards the research reported in this paper.Non peer reviewedPublisher PD

Evaluation of parameters affecting the energy accumulation in longwall mining

The elastic strain energy accumulation in a retreating longwall mining panel is dependent on several parameters which have been identified using elastic theory for beams in an elastic supporting medium. The identified parameters were varied to identify the parameters that have a strong influence on the elastic strain energy accumulation. Upon sensitivity analysis, mining depth, length of cantilever roof in the goaf, coal seam thickness, roof thickness, Young’s modulus of coal seam and roof were identified as the main influencing parameters. The analytical equations were validated by comparing the results with previous studies and a case-specific numerical model. The results obtained from analytical equations were comparable with those obtained from a numerical model. The developed analytical equations will provide a handy tool to make daily, weekly and monthly prediction of areas of high elastic strain energy accumulations inside the solid coal pillar. Hence, the paper finds direct application in improving the safety of people working in coal mines, minimising machine downtime and production delays

Gas-driven rapid fracture propagation and gas outbursts under unloading conditions in coal seams

Copyright © 2018 ARMA, American Rock Mechanics Association. Coal and gas outbursts have long posed a serious risk to safe and efficient production in coal mines. It is recognised that the coal and gas outbursts are triggered by excavation unloading followed by gas-driven rapid propagation of a system of preexisting or mining-induced fractures. Gas-filled fractures parallel to a working face are likely to experience opening first, then expansion and rapid propagation stages under unloading conditions. This research aimed to identify the key factors affecting outburst initiation and its temporal evolution during roadway developments. Specifically, the response of pre-set fractures in a coal seam sandwiched between rock layers to roadway development is simulated using a geomechanical model coupled with fracture mechanics for fracture opening and propagation. In addition, kinetic gas desorption and its migration into open fractures is considered. During simulations outburst is deemed to occur when the fracture length exceeds the dimension of a host element. The findings of this research suggests that the simulated coal and gas outburst may be considered as a dynamic gas desorption-driven fracture propagation process. The occurrence of coal and gas outbursts is found to be influenced mainly by the coal properties, fracture attributes, and initial gas pressure and the in situ stress conditions

Discrete element modelling of hydraulic fracture interaction with natural fractures in shale formations

Research presented in this paper aimed at establishing a better understanding of natural fracture (NF)/hydraulic fracture (HF) interaction mechanisms and fracture network development in naturally fractured and nonhomogeneous shale formations through numerical modelling using the two-dimensional particle flow code (PFC2D). Hydraulic fracture propagation was firstly modelled in a 30 m x 30 m model representing intact rock by bonded particle method (BPM), which served as a base case in the research. Then a single, deterministic natural fracture was embedded into the same model by a smooth joint contact model (SJM) to investigate different NF/HF interaction mechanisms under a range of different conditions by varying the angle of approach, differential horizontal stress, and the mechanical properties of a fracture within the model. Based on the parametric research findings, number and diversity of natural fractures in the model were increased both deterministically and stochastically, and the results are compared and discussed

Multiple-panel longwall top coal caving induced microseismicity: Monitoring and development of a statistical forecasting model for hazardous microseismicity

Continuous microseismic monitoring was carried out around 9 producing longwall top coal caving (LTCC) panels with concurrently recorded daily face advance rates at Coal Mine Velenje in Slovenia over a 27-month monitoring period. The monitoring results suggested that spatial and magnitude characteristics of microseismicity are dominated by those of underlying fractures, while microseismic event rate is under the combined effects of local natural fracture abundance and mining intensity. On this basis, a data-driven yet physics-based forecasting methodology was established for LTCC induced hazardous microseismicity, which is above a given threshold of energy magnitude and within a certain distance to the longwall face. Statistical analyses were first conducted to characterise temporal, magnitude and spatial characteristics of long-term recorded microseismicity, based on which a short-term forecasting model was developed to calculate the probability of hazardous microseismicity considering the three characteristics. The model developed was employed to forecast the likelihood of hazardous microseismicity at one of these LTCC panels, and the forecasted results were supported by the monitoring. This statistical model has important implications in the evaluation of mining-induced hazards, and it can be used to optimise longwall face advance rates to minimise the risk of hazardous microseismicity in burst-prone deep-level mining sites

Parametric analysis of slotting operation induced failure zones to stimulate low permeability coal seams

The main constrain for effective gas drainage in coal mines is the low permeability nature of coal reservoirs. As coal mining activities are extending to deeper subsurface, the ever-increasing in situ stress conditions is anticipated to result in much lower permeability and more challenges for gas emission control in coal mines. In recent years, hydraulic slotting using high-pressure waterjet along underground gas drainage boreholes, as a general solution to stimulate low permeability coal seams, has become increasingly favourable. This paper presents a systematic investigation into the sensitivity of borehole slotting performance to a number of field and operational parameters. A wide range of geomechanical properties, in situ stress conditions, slot geometry and spacing of multiple slots were considered in a series of numerical simulations. The relations between these key parameters and the failure zone size/volume induced by slotting were quantified. The effect of different parameters in improving slotting performance has also been ranked, which provides theoretical base for mine operators to optimise slotting operations