kenneth davey - Academia.edu (original) (raw)
Papers by kenneth davey
Advanced Energy Materials
Chemical Engineering Science
ABSTRACT A novel Friday 13th (Fr 13) risk assessment is used for the first time to investigate th... more ABSTRACT A novel Friday 13th (Fr 13) risk assessment is used for the first time to investigate the fuel-to-steam efficiency of a coal-fired-boiler (CFB). The aim was to quantitatively determine the risk to reduced CFB efficiency in the face of naturally occurring random (stochastic) changes in key parameters. Data from a new commercial plant in East Java, Indonesia are used. The approach was to define an underlying unit-operations model based on the indirect heat-loss method, together with an efficiency risk factor (p). Process behaviour is simulated using a refined Monte Carlo (Latin Hypercube) sampling of 20 key input parameters that include coal feed and quality. The CFB is expected to operate at an efficiency of η=82.82%. Below 77.82% the process is characterized as ‘fail’ due to the greater coal needed to produce steam quantity and quality, and the potential for damage to the boiler. Results reveal an underlying risk of 73 failures in CFB efficiency per 10,000 operations. This equates on average to three failures each year over a prolonged period. This new information cannot be obtained from alternative hazard and risk approaches. A number of changes to the CFB to cut efficiency failures are illustrated using Fr 13 methodology. It is shown to be a practical design tool for improving process reliability and costs. A major benefit is that it can be used in design synthesis and analysis. Findings will be of benefit to operators and manufacturers of boiler equipment.
European Journal of Engineering Education
Advanced Functional Materials
Advanced Energy Materials
Advanced Energy Materials
Angewandte Chemie International Edition
Advanced Science
coordination geometry. [9,10] Several strategies however have been developed to prepare stable MO... more coordination geometry. [9,10] Several strategies however have been developed to prepare stable MOFs in aqueous solution. For example, postsynthetic metal metathesis (PSM) has been extensively applied to d 10 metals-based MOFs. [11] In addition, stable paddle-wheel type MOFs can be made through modular and stepwise synthesis. [12] However, these two methods are complicated, and involve a period of several weeks. As a consequence, only a limited number of MOFs have been reported which are used as electrocatalysts in acid and alkaline solution. [13-15] This is because transition-metal-based MOFs readily collapse in these relative harsh environments. The result is a destroyed host-framework and loss of active sites. Therefore, designing new MOFs with intrinsic stability is important for their applications in electrocatalysis field. Boron imidazolate frameworks (BIFs) are a subclass of MOFs that are made from boron imidazolate ligands and d 10 metal cations. [16] Uniformly distributed 3/4-connected boron components keep the framework rigid. Some specially designed BIFs, for example, BIF-89, are therefore stable in common solvents such as water and dimethylformamide (DMF). This means these are, potentially, alkaline-resistant electrocatalysts for oxygen evolution reaction (OER). [17] BIF-89 however showed poor OER activity because the coordinated Cd atoms in the framework are electrocatalytically inert. Fe 3+ immersed BIF-89 (Fe@BIF-89) works as an effective OER electrocatalyst in alkaline solution because advantage is made of the uncoordinated carboxylic groups to stabilize the incorporation of the Fe 3+ cation. It is widely known that Coor Fe-based materials exhibit good electrocatalytic performance because of highly reactive catalytic sites. [18-21] We proposed therefore to rationally design a bimetallic system containing Co-based BIFs incorporated with Fe 3+ to achieve synergistically enhanced OER activity. We report a new Co-based red-block crystal of CoB(im) 4 (ndc) 0.5 (BIF-91, im = imidazolate, ndc = 2, 6-naphthalenedicarboxylate) that was successfully synthesized by reaction of H 4 ndc with cobalt (II) acetate tetrahydrate and presynthesized KB (im) 4 ligand. Notably, the presence of bridging ndc acid ligands in the BIF-91 molecular channels decreased its porosity and increased the density of coordination bonds. BIF-91 therefore kept its original crystallinity in strong alkaline Metal-organic frameworks (MOFs) have significant potential for practical application in catalysis. However, many MOFs are shown to be sensitive to aqueous solution. This severely limits application of MOFs in electrocatalytic operations for energy production and storage. Here, a Co (II) boron imidazolate framework CoB(im) 4 (ndc) 0.5 (BIF-91, im = imidazolate, ndc = 2,6-naphthalenedicarboxylate) that is rationally designed and successfully tested for electrocatalytic application in strong alkaline (pH ≈ 14) solution is reported. In such a BIF system, the inherent carboxylate species segment large channel spaces into multiple domains in which each single channel is filled with ndc ligands through the effect of zeolite channel confinement. These ligands, with strong CH•••π interaction, act as a rigid auxiliary linker to significantly enhance the structural stability of the BIF-91 framework. Additionally, the π-conjugated effect in BIF-91 stabilizes dopant Fe (III) at the atomic scale to construct Fe-immobilized BIF-91 (Fe@BIF-91). Due to the synergistic effect between Fe (III) guest and Co (II) in the framework, the Fe@BIF-91 acts as an active and stable electrocatalyst for the oxygen evolution reaction in alkaline solution.
Angewandte Chemie International Edition
Advanced Energy Materials
Chemical Engineering Science
ABSTRACT A novel Friday 13th (Fr 13) risk assessment is used for the first time to investigate th... more ABSTRACT A novel Friday 13th (Fr 13) risk assessment is used for the first time to investigate the fuel-to-steam efficiency of a coal-fired-boiler (CFB). The aim was to quantitatively determine the risk to reduced CFB efficiency in the face of naturally occurring random (stochastic) changes in key parameters. Data from a new commercial plant in East Java, Indonesia are used. The approach was to define an underlying unit-operations model based on the indirect heat-loss method, together with an efficiency risk factor (p). Process behaviour is simulated using a refined Monte Carlo (Latin Hypercube) sampling of 20 key input parameters that include coal feed and quality. The CFB is expected to operate at an efficiency of η=82.82%. Below 77.82% the process is characterized as ‘fail’ due to the greater coal needed to produce steam quantity and quality, and the potential for damage to the boiler. Results reveal an underlying risk of 73 failures in CFB efficiency per 10,000 operations. This equates on average to three failures each year over a prolonged period. This new information cannot be obtained from alternative hazard and risk approaches. A number of changes to the CFB to cut efficiency failures are illustrated using Fr 13 methodology. It is shown to be a practical design tool for improving process reliability and costs. A major benefit is that it can be used in design synthesis and analysis. Findings will be of benefit to operators and manufacturers of boiler equipment.
European Journal of Engineering Education
Advanced Functional Materials
Advanced Energy Materials
Advanced Energy Materials
Angewandte Chemie International Edition
Advanced Science
coordination geometry. [9,10] Several strategies however have been developed to prepare stable MO... more coordination geometry. [9,10] Several strategies however have been developed to prepare stable MOFs in aqueous solution. For example, postsynthetic metal metathesis (PSM) has been extensively applied to d 10 metals-based MOFs. [11] In addition, stable paddle-wheel type MOFs can be made through modular and stepwise synthesis. [12] However, these two methods are complicated, and involve a period of several weeks. As a consequence, only a limited number of MOFs have been reported which are used as electrocatalysts in acid and alkaline solution. [13-15] This is because transition-metal-based MOFs readily collapse in these relative harsh environments. The result is a destroyed host-framework and loss of active sites. Therefore, designing new MOFs with intrinsic stability is important for their applications in electrocatalysis field. Boron imidazolate frameworks (BIFs) are a subclass of MOFs that are made from boron imidazolate ligands and d 10 metal cations. [16] Uniformly distributed 3/4-connected boron components keep the framework rigid. Some specially designed BIFs, for example, BIF-89, are therefore stable in common solvents such as water and dimethylformamide (DMF). This means these are, potentially, alkaline-resistant electrocatalysts for oxygen evolution reaction (OER). [17] BIF-89 however showed poor OER activity because the coordinated Cd atoms in the framework are electrocatalytically inert. Fe 3+ immersed BIF-89 (Fe@BIF-89) works as an effective OER electrocatalyst in alkaline solution because advantage is made of the uncoordinated carboxylic groups to stabilize the incorporation of the Fe 3+ cation. It is widely known that Coor Fe-based materials exhibit good electrocatalytic performance because of highly reactive catalytic sites. [18-21] We proposed therefore to rationally design a bimetallic system containing Co-based BIFs incorporated with Fe 3+ to achieve synergistically enhanced OER activity. We report a new Co-based red-block crystal of CoB(im) 4 (ndc) 0.5 (BIF-91, im = imidazolate, ndc = 2, 6-naphthalenedicarboxylate) that was successfully synthesized by reaction of H 4 ndc with cobalt (II) acetate tetrahydrate and presynthesized KB (im) 4 ligand. Notably, the presence of bridging ndc acid ligands in the BIF-91 molecular channels decreased its porosity and increased the density of coordination bonds. BIF-91 therefore kept its original crystallinity in strong alkaline Metal-organic frameworks (MOFs) have significant potential for practical application in catalysis. However, many MOFs are shown to be sensitive to aqueous solution. This severely limits application of MOFs in electrocatalytic operations for energy production and storage. Here, a Co (II) boron imidazolate framework CoB(im) 4 (ndc) 0.5 (BIF-91, im = imidazolate, ndc = 2,6-naphthalenedicarboxylate) that is rationally designed and successfully tested for electrocatalytic application in strong alkaline (pH ≈ 14) solution is reported. In such a BIF system, the inherent carboxylate species segment large channel spaces into multiple domains in which each single channel is filled with ndc ligands through the effect of zeolite channel confinement. These ligands, with strong CH•••π interaction, act as a rigid auxiliary linker to significantly enhance the structural stability of the BIF-91 framework. Additionally, the π-conjugated effect in BIF-91 stabilizes dopant Fe (III) at the atomic scale to construct Fe-immobilized BIF-91 (Fe@BIF-91). Due to the synergistic effect between Fe (III) guest and Co (II) in the framework, the Fe@BIF-91 acts as an active and stable electrocatalyst for the oxygen evolution reaction in alkaline solution.
Angewandte Chemie International Edition