An experimental investigation of flow and reaction processes during gas storage and displacement in coal

An advanced laboratory facility has been designed, developed and commissioned which offers an extensive capability for detailed study of various aspects of geoenergy problems in fractured rocks. It comprises i) a high pressure manometric sorption apparatus, ii) a high pressure triaxial core flooding system and iii) an ancillary system including pure and mixed gas supply and analysing units. The manometric sorption apparatus is capable of measuring adsorption/desorption isotherms of various gas species on powdered and intact samples. The triaxial core flooding system is capable of measuring the gas flow properties and deformation behaviour of coal samples, up to 0.1m diameter and 0.2m length. Deep underground conditions in terms of pore pressure and confining pressure can be replicated using the high pressure triaxial cell for depths up to 2000m. The laboratory facility has been designed and developed to produce high resolution data for a broad range of gas injection pressures (up to 20MPa) and temperature values (up to 338K). Appropriate pressure transducers and flow meters were selected and have been incorporated into the system following a series of detailed and thorough analyses performed to define and optimise the specifications of the measurement devices. Anthracite coal samples from the South Wales coalfield (6-ft seam measure) have been characterised and tested. Equilibrium and kinetic phenomena of the adsorption and desorption of different gases, i.e. nitrogen (N2), methane (CH4) and carbon dioxide (CO2), at injection pressures up to 7MPa have been studied. A series of core flooding experiments have been carried out on samples of 0.07m diameter and 0.12m length, at gas injection pressures up to 5.5MPa and confining pressures up to 6MPa. The absolute and relative permeability of the samples, to different gases and the permeability evolution with changes in the gas pressure and confining stress condition have been studied. The fate of adsorbed CO2 was studied via a sequential series of N2 and CH4 flooding experiments. The storage and displacement of N2 and CO2 in a sample saturated with CH4 at 5MPa pressure was investigated via another series of flooding tests. During the injection of the gases, the composition of the outflow gas was analysed. Modelling work has been carried out to further investigate the experimental results and processes involved in gas transport and reactions. The numerical model used, includes a theoretical approach for modelling the permeability evolution in coal. The results of the gas adsorption tests indicated a higher adsorption capacity to CO2 compared to CH4 and N2, i.e. 1.3 and 2.5 times higher, respectively. Also, different hysteresis behaviours were observed during the adsorption and desorption measurements, for the different gases studied. An improved understanding of the controlling mechanisms of gas adsorption rate and the kinetics of the processes has thus been achieved. From the results of the core flooding experiments, it was found that the permeability evolution of the coal sample to CO2, due to an increase in gas pressure, exhibited a different pattern compared to the other gases. A considerable reduction above a certain gas pressure value was observed. This was found to be related to coal matrix swelling induced by CO2 adsorption. The results of following N2 and CH4 flooding experiments showed a partial restoration of the initial permeability of the coal sample, indicating the stability of the adsorbed CO2 in the coal matrix during the period of analysis. The results of N2 and CO2 storage and displacement in coal showed that CO2 injection into coal was more efficient in terms of total CH4 recovery, gas displacement ratio, breakthrough time and amount of the gas storage than achieved through N2 displacements. The effect of swelling on the coal permeability however was found to be considerable. The application of the experimental results in the adopted theoretical model led to the identification of the major mechanisms controlling the behaviour of coal during gas displacement, together with the influential factors on flow behaviour. The results also highlighted coupled physico-chemical effects during carbon dioxide sequestration in coal. It is claimed that the work presented in this thesis has provided a new and comprehensive set of high resolution data. Various aspects related to high pressure flow and reaction of various gas species in coal have been studied. A detailed set of benchmarks have been produced that can be used for the development and validation of theoretical models. New insights into several phenomena related to carbon sequestration in coal are thus claimed to have been achieved

Construction Safety Ontology Development and Alignment with Industry Foundation Classes (IFC)

A pronounced gap often exists between expected and actual safety performance in the construction industry. The multifaceted causes of this performance gap are resulting from the misalignment between design assumptions and actual construction processes that take place on-site. In general, critical factors are rooted in the lack of interoperability around the building and work-environment information due to its heterogeneous nature. To overcome the interoperability challenge in safety management, this paper represents the development of an ontological model consisting of terms and relationships between these terms, creating a conceptual information model for construction safety management and linking that ontology to IfcOWL. The developed ontology, named Safety and Health Exchange (SHE), comprises eight concepts and their relationships required to identify and manage safety risks in the design and planning stages. The main concepts of the developed ontology are identified based on reviewing accident cases from 165 Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR) and 31 Press Releases from the database of the Health and Safety Executive (HSE) in the United Kingdom. Consequently, a semantic mapping between the developed ontology and IfcOWL (the most popular ontology and schema for interoperability in the AEC sector) is proposed. Then several SPARQL queries were developed and implemented to evaluate the semantic consistency of the developed ontology and the cross-mapping. The proposed ontology and cross-mapping gained recognition for its innovation in utilising OpenBIM and won the BuildingSMART professional research award 2020. This work could facilitate developing a knowledge-based system in the BIM environment to assist designers in addressing health and safety issues during the design and planning phases in the construction sector

Dataset of characterised construction safety risks and related treatments

The Safety Risk Library [1] is a structured database [2] that integrates knowledge drawn from multiple sources to address the problem of information disaggregation in the construction industry. This knowledge base maps construction safety risk scenarios to treatment suggestions that help designers implement the concept of prevention through design. In the context of the Safety Risk Library, risk scenarios are characterised by six data categories based on a formalised ontology [3]. To build the first iteration of the Safety Risk Library, nine different risk scenarios were identified and mapped to relevant risk treatments in focus groups. Subsequently, the Safety Risk Library was pilot tested in six construction projects, and user feedback and input were used to expand the list of risk scenarios and treatment prompts. Additionally, public press releases reporting construction accidents were analysed to identify and characterise risk scenarios, which were then mapped to appropriate treatment suggestions and included in the Safety Risk Library. This dataset can assist construction industry stakeholders in identifying, characterising, communicating and mitigating safety risks in construction projects. It can also be integrated into building information modelling environments to assist designers to implement prevention through design

BIM-based construction safety risk library

This paper presents a digital tool and Safety Risk library to assist designers in their health and safety work in BIM digital environments. Addressing an industry need for improved knowledge sharing and collaboration, the BIM Safety Risk library tool aligns with a Prevention through Design (PtD) approach that links safety risks to treatments via different risk scenarios. Motivated by continuing sub-optimal health and safety management processes, the research employs a conceptual framework rooted in construction guidance: structuring data via a 7-stage ontology to improve designer knowledge of issues and give access to an expanding safety knowledge base (the BIM Safety Risk Library). The tool facilitates tacit and explicit knowledge sharing in visual environments, enabling the construction industry to benefit from their health and safety data while providing an interactive learning tool for designers. The structuring of data also opens up possibilities for other digital advances (e.g. via automatic rule checking)

NaOH-benzoic acid modified biochar for enhanced removal of aromatic VOCs

This paper proposes a new alkali-acid-based treatment to enhance the capacity of biochar for the removal of toluene and p-xylene as the most abundant VOCs worldwide (BTEX) with acute toxicity to humans. We present the results of the a series of experiments on NaOH-modified benzoic-acid-activated biochar, pyrolysed from wheat straw and hardwood. Biochar samples were modified using the impregnation method and characterised by elemental analysis, scanning electron microscopy, FTIR spectroscopy, and BET surface area analysis. A bespoke experimental setup equipped with an inline GC-FID was utilised to study the adsorption and desorption processes. The proposed technique improved the structural properties of biochar, increasing specific surface area and pore volume while enhancing surface chemistry. Original samples’ SSAs (WS: 58.38 m2/g, HW: 19.92 m2/g) increased significantly post-treatment (WS: 121.72 m2/g, HW: 62.45 m2/g) due to alkalic digestion and were slightly reduced by benzoic acid modification. The treated biochar exhibited an improved surface chemistry, facilitating the formation of oxygen-containing groups acting as efficient sorbents for toluene and p-xylene molecules. Toluene adsorption increased from 32.5 mg/g (WS) and 27.6 mg/g (HW) to 125.3 mg/g (AWSBA3) and 83.3 mg/g (AHWBA3). P-xylene adsorption, higher due to its greater molar mass, remained elevated in modified samples. The treated biochar displayed promising regeneration potential of 88.4 %–97.6 % over five adsorption–desorption cycles. The enhanced adsorption and reusability of the treated biochar demonstrate the potential of the proposed modification method to effectively remove aromatic VOCs at low costs