Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 52
Filter
1.
Sci Rep ; 14(1): 1962, 2024 01 23.
Article in English | MEDLINE | ID: mdl-38263453

ABSTRACT

Footprints represent a relevant vestige providing direct information on the biology, locomotion, and behaviour of the individuals who left them. However, the spatiotemporal distribution of hominin footprints is heterogeneous, particularly in North Africa, where no footprint sites were known before the Holocene. This region is important in the evolution of hominins. It notably includes the earliest currently known Homo sapiens (Jebel Irhoud) and the oldest and richest African Middle Stone Age hominin sites. In this fragmented ichnological record, we report the discovery of 85 human footprints on a Late Pleistocene now indurated beach surface of about 2800 m2 at Larache (Northwest coast of Morocco). The wide range of sizes of the footprints suggests that several individuals from different age groups made the tracks while moving landward and seaward across a semi-dissipative bar-trough sandy beach foreshore. A geological investigation and an optically stimulated luminescence dating of a rock sample extracted from the tracksite places this hominin footprint surface at 90.3 ± 7.6 ka (MIS 5, Late Pleistocene). The Larache footprints are, therefore, the oldest attributed to Homo sapiens in Northern Africa and the Southern Mediterranean.


Subject(s)
Hominidae , Animals , Humans , Africa, Northern , Morocco
3.
Pain ; 164(5): 1051-1066, 2023 05 01.
Article in English | MEDLINE | ID: mdl-36448978

ABSTRACT

ABSTRACT: The nucleus of the solitary tract (NTS) contains pro-opiomelanocortin (POMC) neurons that are 1 of the 2 major sources of ß-endorphin in the brain. The functional role of these NTS POMC neurons in nociceptive and cardiorespiratory function is debated. We have shown that NTS POMC optogenetic activation produces bradycardia and transient apnoea in a working heart-brainstem preparation and chemogenetic activation with an engineered ion channel (PSAM) produced opioidergic analgesia in vivo. To better define the role of the NTS POMC neurons in behaving animals, we adopted in vivo optogenetics (ChrimsonR) and excitatory/inhibitory chemogenetic DREADD (hM3Dq/hM4Di) strategies in POMC-Cre mice. We show that optogenetic activation of NTS POMC neurons produces time-locked, graded, transient bradycardia and bradypnoea in anaesthetised mice that is naloxone sensitive (1 mg/kg, i.p.), suggesting a role of ß-endorphin. Both optogenetic and chemogenetic activation of NTS POMC neurons produces sustained thermal analgesia in behaving mice that can be blocked by naloxone. It also produced analgesia in an inflammatory pain model (carrageenan) but not in a neuropathic pain model (tibial nerve transection). Inhibiting NTS POMC neurons does not produce any effect on basal nociception but inhibits stress-induced analgesia (unlike inhibition of arcuate POMC neurons). Activation of NTS POMC neuronal populations in conscious mice did not cause respiratory depression, anxiety, or locomotor deficit (in open field) or affective preference. These findings indicate that NTS POMC neurons play a key role in the generation of endorphinergic endogenous analgesia and can also regulate cardiorespiratory function.


Subject(s)
Analgesia , Pro-Opiomelanocortin , Mice , Animals , Pro-Opiomelanocortin/genetics , Pro-Opiomelanocortin/metabolism , Pro-Opiomelanocortin/pharmacology , Solitary Nucleus , Bradycardia , beta-Endorphin , Neurons , Naloxone/pharmacology , Pain
4.
Can J Neurol Sci ; 50(5): 703-709, 2023 09.
Article in English | MEDLINE | ID: mdl-36017730

ABSTRACT

OBJECTIVE: To characterize Parkinson's disease (PD) symptoms based on the presence, onset time, and severity of rapid eye movement sleep behavior disorder (RBD) and their association with impulse control disorders (ICD). BACKGROUND: RBD is a frequent non-motor symptom in PD, usually described as prodromal. The severity of RBD according to the start time and its relationship with ICD in PD needs further clarification. METHODS: A survey-based study was performed to determine the presence of RBD symptoms, their severity, and the temporal relationship with the PD onset. The survey included RBD1Q, the Mayo Sleep, and the RBDQ-HK questionnaires and questions about clinical characteristics, including ICD. Only PD patients with care partners spending night hours in the same room were included. RESULTS: 410 PD patients were included: 206 with RBD (50.2%) and 204 non-RBD (49.8%). The PD-RBD patients were younger and their daily levodopa dose was higher than the non-RBD group. Most of these patients developed RBD symptoms after the onset of clinical PD were younger at motor symptom onset and had higher scores in the hallucinations and psychosis subsection of MDS-UPDRS-I. RBD group had a more severe non-motor phenotype, including more ICD than those without RBD, mainly due to higher compulsive eating. CONCLUSIONS: In our study, most patients recognized RBD symptoms after the onset of the PD motor symptoms and the clinical features of PD with and without RBD were distinctive, supporting the hypothesis that PD-RBD might represent a variant pattern of neurodegeneration.


Subject(s)
Parkinson Disease , REM Sleep Behavior Disorder , Humans , Parkinson Disease/complications , Parkinson Disease/epidemiology , REM Sleep Behavior Disorder/etiology , REM Sleep Behavior Disorder/complications , Levodopa , Sleep , Surveys and Questionnaires
5.
Sci Total Environ ; 857(Pt 1): 159155, 2023 Jan 20.
Article in English | MEDLINE | ID: mdl-36206897

ABSTRACT

Over the years, the transformation of biomass into a plethora of renewable value-added products has been identified as a promising strategy to fulfil high energy demands, lower greenhouse gas emissions, and exploit under-utilized resources. Techno-economic analysis (TEA) and life-cycle assessment (LCA) are essential to scale up this process while lowering the conversion cost. In this study, trade-offs are made between economic, environmental, and technical indicators produced from these methodologies to better evaluate the commercialization potential of biomass pyrolysis. This research emphasizes the necessity of combining LCA and TEA variables to assess the performance of the early-stage technology and associated constraints. The important findings based on the LCA analysis imply that most of the studies reported in literature focussed on the global warming potentials (GWP) under environmental category by considering greenhouse gases (GHGs) as evaluation parameter, neglecting many other important environmental indices. In addition, the upstream and downstream processes play an important role in understanding the life cycle impacts of a biomass based biorefinery. Under upstream conditions, the use of a specific type of feedstock may influence the LCA conclusions and technical priority. Under downstream conditions, the product utilization as fuels in different energy backgrounds is crucial to the overall impact potentials of the pyrolysis systems. In view of the TEA analysis, investigations towards maximizing the yield of valuable co-products would play an important role in the commercialization of pyrolysis process. However, comprehensive research to compare the conventional, advanced, and emerging approaches of biomass pyrolysis from the economic perspective is currently not available in the literature.


Subject(s)
Biofuels , Pyrolysis , Biomass
6.
Bioresour Technol ; 364: 128087, 2022 Nov.
Article in English | MEDLINE | ID: mdl-36216287

ABSTRACT

Biomass pyrolysis has recently gained increasing attention as a thermochemical conversion process for obtaining value-added products, thanks to the development of cutting-edge, innovative and cost-effective pyrolysis processes. Over time, new and novel pyrolysis techniques have emerged, and these processes can be tuned to maximize the production of high-quality hydrogen. This review examines recent advancements in biomass pyrolysis by classifying them into conventional, advanced and emerging approaches. A comprehensive overview on the recent advancements in biomass pyrolysis, highlighting the current status for industrial applications is presented. Further, the impact of each technique under different approaches on conversion of biomass for hydrogen production is evaluated. Techniques, such as inline catalytic pyrolysis, microwave pyrolysis, etc., can be employed for the sustainable production of hydrogen. Finally, the techno-economic analysis is presented to understand the viability of pyrolysis at large scale. The outlook highlights discernments into future directions, aimed to overcome the current shortcomings.

7.
Article in English | MEDLINE | ID: mdl-35633037

ABSTRACT

OBJECTIVES: Caregiving burdens are a substantial concern in the clinical care of persons with neurodegenerative disorders. In the Ontario Neurodegenerative Disease Research Initiative, we used the Zarit's Burden Interview (ZBI) to examine: (1) the types of burdens captured by the ZBI in a cross-disorder sample of neurodegenerative conditions (2) whether there are categorical or disorder-specific effects on caregiving burdens, and (3) which demographic, clinical, and cognitive measures are related to burden(s) in neurodegenerative disorders? METHODS/DESIGN: N = 504 participants and their study partners (e.g., family, friends) across: Alzheimer's disease/mild cognitive impairment (AD/MCI; n = 120), Parkinson's disease (PD; n = 136), amyotrophic lateral sclerosis (ALS; n = 38), frontotemporal dementia (FTD; n = 53), and cerebrovascular disease (CVD; n = 157). Study partners provided information about themselves, and information about the clinical participants (e.g., activities of daily living (ADL)). We used Correspondence Analysis to identify types of caregiving concerns in the ZBI. We then identified relationships between those concerns and demographic and clinical measures, and a cognitive battery. RESULTS: We found three components in the ZBI. The first was "overall burden" and was (1) strongly related to increased neuropsychiatric symptoms (NPI severity r = 0.586, NPI distress r = 0.587) and decreased independence in ADL (instrumental ADLs r = -0.566, basic ADLs r = -0.43), (2) moderately related to cognition (MoCA r = -0.268), and (3) showed little-to-no differences between disorders. The second and third components together showed four types of caregiving concerns: current care of the person with the neurodegenerative disease, future care of the person with the neurodegenerative disease, personal concerns of study partners, and social concerns of study partners. CONCLUSIONS: Our results suggest that the experience of caregiving in neurodegenerative and cerebrovascular diseases is individualized and is not defined by diagnostic categories. Our findings highlight the importance of targeting ADL and neuropsychiatric symptoms with caregiver-personalized solutions.


Subject(s)
Cerebrovascular Disorders , Frontotemporal Dementia , Neurodegenerative Diseases , Activities of Daily Living , Caregivers/psychology , Humans , Ontario
8.
Arch Dis Child ; 107(8): 747-751, 2022 08.
Article in English | MEDLINE | ID: mdl-35172964

ABSTRACT

OBJECTIVE: European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) guidelines on coeliac disease (CD) recommend that children who have IgA-based antitissue transglutaminase (TGA-IgA) titre ≥10× upper limit of normal (ULN) and positive antiendomysial antibody, can be reliably diagnosed with CD via the no-biopsy pathway. The aim of this study was to examine the relationship between TGA-IgA ≥5×ULN and histologically confirmed diagnosis of CD. METHODS: Data including TGA-IgA levels at upper gastrointestinal endoscopy and histological findings from children diagnosed with CD following endoscopy from 2006 to 2021 were analysed. CD was confirmed by Marsh-Oberhuber histological grading 2 to 3 c. Statistical analysis was performed using χ² analysis (p<0.05= significant). RESULTS: 722 of 758 children had histological confirmation of CD. 457 children had TGA-IgA ≥5×ULN and 455 (99.5%) of these had histological confirmation for CD; the two that did not had eventual diagnosis of CD based on clinicopathological features. 114 of 457 had between TGA-IgA ≥5×ULN and <10×ULN, all had confirmed CD. The likelihood of a positive biopsy with TGA-IgA ≥5×ULN (455/457) compared with TGA-IgA <5×ULN (267/301) has strong statistical significance (p<0.00001). The optimal TGA-IgA cut-off from receiver operating characteristic curve analysis was determined to be below 5×ULN for the two assays used. CONCLUSION: 99.5% of children with TGA-IgA ≥5×ULN had histological confirmation of CD, suggesting that CD diagnosis can be made securely in children with TGA-IgA ≥5×ULN. If other studies confirm this finding, there is a case to be made to modify the ESPGHAN guidelines to a lower threshold of TGA-IgA for serological diagnosis of CD.


Subject(s)
Celiac Disease , Transglutaminases , Autoantibodies , Biopsy , Celiac Disease/diagnosis , Child , Humans , Immunoglobulin A , Transglutaminases/blood
9.
Turk J Chem ; 45(2): 452-462, 2021.
Article in English | MEDLINE | ID: mdl-34104056

ABSTRACT

A gas mixture representing oxy-fuel combustion conditions was employed in a thermogravimetric analyser to determine the effect of water vapor and SO2 concentration on limestone sulfation kinetics over the temperature range of 800 to 920 °C. Here, experiments used small samples of particles (4 mg), with small particle sizes (dp < 38 µm) and large gas flow rates (120 mL/min@NTP) in order to minimize mass transfer interferences. The gas mixture contained 5000 ppmv SO2, 2% O2, and the H2O content was changed from 0% to 25% with the balance CO2. When water vapor was added to the gas mixture at lower temperatures (800-870 °C), the limestone SO2 capture efficiency increased. However, as the temperature became higher, the enhancement in total conversion values decreased. As expected, Havelock limestone at higher temperatures (890 °C, 920 °C, and 950 °C) experienced indirect sulfation and reacted at a faster rate than for lower temperatures (800-870 °C) for direct sulfation over the first five minutes of reaction time. However, the total conversion of Havelock limestone for direct sulfation was generally greater than for indirect sulfation.

10.
J Foot Ankle Surg ; 60(5): 891-896, 2021.
Article in English | MEDLINE | ID: mdl-33785240

ABSTRACT

Numerous techniques have been described for first metatarsophalangeal joint (MTPJ) fusion. The aim of this study was to prospectively evaluate an innovative plating system which uses a cross plate compression screw. Thirty consecutive first MTPJ fusions in 28 patients were evaluated. All procedures were performed by a single fellowship trained consultant foot and ankle surgeon. Patient function was evaluated preoperatively at 6 and at 12 months using the Manchester-Oxford Foot Questionnaire (MOXFQ). Union rates and complications were recorded. Postoperative MOXFQ scores demonstrated significant improvement in all domains, with mean improvement at 12 months of 35, 27, 17 and 106 points for pain, walking/standing, social interactions and combined scores respectively (p value ≤.0001). In all 30 cases, clinical and radiological evidence of union was achieved by 6 months. Superficial infection occurred in 1 (3%) case. One (3%) case required plate removal due to soft tissue irritation. There were no plate failures. This evaluation study demonstrates that this cross-plate compression plating system is safe, provides high patient satisfaction and reliable union, with low complication rates. Prospective comparative research is now required to determine the optimal technique for first MTPJ fusion.


Subject(s)
Hallux Rigidus , Metatarsophalangeal Joint , Arthrodesis , Bone Plates , Bone Screws , Hallux Rigidus/diagnostic imaging , Hallux Rigidus/surgery , Humans , Metatarsophalangeal Joint/diagnostic imaging , Metatarsophalangeal Joint/surgery , Retrospective Studies , Treatment Outcome
11.
ACS Omega ; 5(50): 32498-32506, 2020 Dec 22.
Article in English | MEDLINE | ID: mdl-33376887

ABSTRACT

Oxyfuel combustion can reduce CO2 emissions from fossil fuels. Hence, it is currently being investigated for potential use in oil shale-fired power plants, which currently produce most of Estonia's electricity. Here, experiments were performed with kukersite oil shale for both oxyfuel and conventional combustion in a 60 kWth circulating fluidized bed combustor. In this paper, we provide data on the ash composition including mineral compositions and heavy metal concentrations. Oxyfuel conditions did not noticeably influence the concentrations of heavy metals in the ash but did have significantly lower amounts of free lime because of inhibition of the carbonate decomposition reactions. The results suggest that oxyfuel combustion would produce no significant problems in terms of the behavior of the ash or the fate of heavy metals contained in the ash.

12.
Molecules ; 25(21)2020 Oct 29.
Article in English | MEDLINE | ID: mdl-33138276

ABSTRACT

This study explores the use of a novel activating agent and demonstrates the production and characterisation of activated carbon (AC) from a combine palm waste (CPW) in 3:2:1 proportion by weight of empty fruit bunch, mesocarp fibre and palm kernel shell. The resulting biomass was processed by a microwave-assisted method using trona and compared with material produced by conventional routes. These results demonstrate the potential of trona ore as an activating agent and the effectiveness of using a combined palm waste for a single stream activation process. It also assesses the effectiveness of trona ore in the elimination of alcohol, acids and aldehydes; with a focus on increasing the hydrophilicity of the resultant AC. The optimum results for the conventional production technique at 800 °C yielded a material with SBET 920 m2/g, Vtotal 0.840 cm3/g, a mean pore diameter of 2.2 nm and an AC yield 40%. The optimum outcome of the microwave assisted technique for CPW was achieved at 600 W, SBET is 980 m2/g; Vtotal 0.865 cm3/g; a mean pore diameter 2.2 nm and an AC yield of 42%. Fourier transform infrared spectrometry analyses showed that palm waste can be combined to produce AC and that trona ore has the capacity to significantly enhance biomass activation.


Subject(s)
Bicarbonates/chemistry , Biomass , Charcoal/chemistry , Microwaves , Poaceae/chemistry
13.
Sci Rep ; 10(1): 8085, 2020 05 15.
Article in English | MEDLINE | ID: mdl-32415150

ABSTRACT

Since the 1990s the Mekong River delta has suffered a large decline in sediment supply causing coastal erosion, following catchment disturbance through hydropower dam construction and sand extraction. However, our new geological reconstruction of 2500-years of delta shoreline changes show that serious coastal erosion actually started much earlier. Data shows the sandy coast bounding river mouths accreted consistently at a rate of +2 to +4 km2/year. In contrast, we identified a variable accretion rate of the muddy deltaic protrusion at Camau; it was < +1 km2/year before 1400 years ago but increased drastically around 600 years ago, forming the entire Camau Peninsula. This high level of mud supply had sharply declined by the early 20th century after a vast canal network was built on the delta. Since then the Peninsula has been eroding, promoted by the conjunction of mud sequestration in the delta plain driven by expansion of rice cultivation, and hysteresis of long-term muddy sedimentation that left the protrusion exposed to wave erosion. Natural mitigation would require substantial increases in sediment supply well above the pre-1990s levels.

14.
BMJ Paediatr Open ; 4(1): e000617, 2020.
Article in English | MEDLINE | ID: mdl-32201745

ABSTRACT

BACKGROUND: Paediatric chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is common (prevalence 1%-2%). Two-thirds of children experience moderate or severe pain, which is associated with increased fatigue and poorer physical function. However, we do not know if treatment for CFS/ME improves pain. OBJECTIVE: Identify whether specialist treatment of paediatric CFS/ME improves pain. METHODS: We conducted a detailed search in MEDLINE, EMBASE, PsycINFO and the Cochrane Library. Two researchers independently screened texts published between 1994 and 24 January 2019 with no language restrictions. Inclusion criteria were (1) randomised controlled trials and observational studies; (2) participants aged <19 years with CFS/ME; and (3) measure of pain before and after an intervention. RESULTS: Of 1898 papers screened, 26 studies investigated treatment for paediatric CFS/ME, 19 of which did not measure pain at any time point. Only five treatment studies measured pain at baseline and follow-up and were included in this review. None of the interventions were specifically targeted at treating pain. Of the included studies, two showed no improvement in pain scores, one suggested an improvement in one subgroup and two studies identified improvements in pain measures in 'recovered' patients compared with 'non-recovered' patients. CONCLUSIONS: Despite the prevalence and impact of pain in children with CFS/ME surprisingly few treatment studies measured pain. In those that did measure pain, the treatments used focused on overall management of CFS/ME and we identified no treatments that were targeted specifically at managing pain. There is limited evidence that treatment helps improve pain scores. However, patients who recover appear to have less pain than those who do not recover. More studies are needed to determine if pain in paediatric CFS/ME requires a specific treatment approach, with a particular focus on patients who do not recover following initial treatment. PROSPERO REGISTRATION NUMBER: CRD42019117540.

15.
Sci Rep ; 9(1): 9236, 2019 06 25.
Article in English | MEDLINE | ID: mdl-31239484

ABSTRACT

The world's large rivers are under stress and experiencing unprecedented changes in hydrology, ecosystems, and fluvial sediment loads. Many of these rivers terminate at the great deltas of the world (home to 500 million people), which depend on fluvial sediments for their very existence. While fluvial sediment loads of large rivers have already been greatly modified by human activities, climate change is expected to further exacerbate the situation. But how does the effect of climate change on fluvial sediment loads compare with that of human impacts? Here, we address this question by combining historical observations and 21st century projections for one of the world's largest 25 rivers containing two mega dams; Pearl River, China. Our analysis shows that variations in fluvial sediment supply to the coast from the Pearl river over a ~150 year study period are dominated by human activities. Projected climate change driven 21st century increases in riverflow will only compensate for about 1% of the human induced deficit in sediment load, leading to the coastal zone being starved of about 6000 Mt of sediment over the remainder of this century. A similar dominance of human impacts on fluvial sediment supply is likely at other heavily engineered rivers.


Subject(s)
Climate Change , Environmental Monitoring/methods , Geologic Sediments/analysis , Human Activities/statistics & numerical data , Rivers/chemistry , China , Ecosystem , Humans , Hydrology , Water Movements
16.
Sci Total Environ ; 658: 1404-1415, 2019 Mar 25.
Article in English | MEDLINE | ID: mdl-30678000

ABSTRACT

Power generation and other industries using solid fossil fuels like coal, lignite, oil shale and peat are responsible for producing large quantities of solid residues that are often chemically reactive and/or unstable and are disposed in holding ponds and deposition sites. Stability and long-term behaviour of such deposits are typically studied in short-term laboratory experiments that cannot describe nor predict long-term changes taking place in these materials. Here, we study long-term (>40 years) transformations, in highly alkaline conditions, of the Ca-rich ash deposit in Estonia composed of oil shale processing residues from the Eesti power plant. Detailed mineralogical, chemical and micromorphological analyses using X-ray diffraction, X-ray fluorescence, 29Si nuclear magnetic resonance, scanning electron microscopy and other methods were applied in order to identify the composition of the waste with a focus on formation and transformation of semicrystalline phases in the deposit. The results show progressive formation of calcium-silicate-hydrate (C-S-H) type phase at the expense of silicate minerals and amorphous glass phases with increasing depth and age of the sediments, from about 25% in the upper part of the depository to over 60% in the oldest-deepest part. This demonstrates that over time the high alkalinity of the ash is responsible for initiating natural alkali-activation. The formation of C-S-H-type phases increases the mechanical strength of the sediment and ensures long-term stability of waste deposits. These findings may encourage the use of these ashes in binder or other construction material production or as construction aggregates.

17.
Biosens Bioelectron ; 123: 152-159, 2019 Jan 01.
Article in English | MEDLINE | ID: mdl-30177422

ABSTRACT

Here we report the first mediated microneedles-based biosensor for minimally invasive continuous sensing of lactate in the dermal interstitial fluid (ISF). To further demonstrate the capability of microneedle arrays as second generation biosensors we have functionalized gold microneedles with nanocarbons at which mediated electron transfer of lactate oxidase takes place. In particular the gold surface of the microneedles electrode has been modified in 3 subsequent steps: i) electrodeposition of Au-multiwalled carbon nanotubes (MWCNTs); ii) electropolymerization of the mediator, methylene blue (MB); iii) immobilization of the enzyme lactate oxidase (LOX) by drop-casting procedure. The resulting microneedle-based LOX biosensor displays an interference-free lactate detection without compromising its sensitivity, stability, selectivity and response time. The performance of the microneedle array, second generation biosensor for lactate detection was assessed in artificial interstitial fluid and in human serum, both spiked with lactate. The results reveal that the new microneedles lactate sensor holds interesting promise for the development of a real-time monitoring device to be used in sport medicine and clinical care.


Subject(s)
Biosensing Techniques , Lactic Acid/isolation & purification , Mixed Function Oxygenases/chemistry , Nanotubes, Carbon/chemistry , Electrodes , Enzymes, Immobilized/chemistry , Extracellular Fluid/chemistry , Gold/chemistry , Humans , Lactic Acid/chemistry , Needles
18.
Energy Convers Manag ; 163: 74-85, 2018 May 01.
Article in English | MEDLINE | ID: mdl-29725147

ABSTRACT

A probabilistic modelling approach was developed and applied to investigate the energy and environmental performance of an innovative sanitation system, the "Nano-membrane Toilet" (NMT). The system treats human excreta via an advanced energy and water recovery island with the aim of addressing current and future sanitation demands. Due to the complex design and inherent characteristics of the system's input material, there are a number of stochastic variables which may significantly affect the system's performance. The non-intrusive probabilistic approach adopted in this study combines a finite number of deterministic thermodynamic process simulations with an artificial neural network (ANN) approximation model and Monte Carlo simulations (MCS) to assess the effect of system uncertainties on the predicted performance of the NMT system. The joint probability distributions of the process performance indicators suggest a Stirling Engine (SE) power output in the range of 61.5-73 W with a high confidence interval (CI) of 95%. In addition, there is high probability (with 95% CI) that the NMT system can achieve positive net power output between 15.8 and 35 W. A sensitivity study reveals the system power performance is mostly affected by SE heater temperature. Investigation into the environmental performance of the NMT design, including water recovery and CO2/NOx emissions, suggests significant environmental benefits compared to conventional systems. Results of the probabilistic analysis can better inform future improvements on the system design and operational strategy and this probabilistic assessment framework can also be applied to similar complex engineering systems.

19.
J Vis Exp ; (128)2017 10 25.
Article in English | MEDLINE | ID: mdl-29155774

ABSTRACT

Calcium looping (CaL) is a post-combustion CO2 capture technology that is suitable for retrofitting existing power plants. The CaL process uses limestone as a cheap and readily available CO2 sorbent. While the technology has been widely studied, there are a few available options that could be applied to make it more economically viable. One of these is to increase the oxygen concentration in the calciner to reduce or eliminate the amount of recycled gas (CO2, H2O and impurities); therefore, decreasing or removing the energy necessary to heat the recycled gas stream. Moreover, there is a resulting increase in the energy input due to the change in the combustion intensity; this energy is used to enable the endothermic calcination reaction to occur in the absence of recycled flue gases. This paper presents the operation and first results of a CaL pilot plant with 100% oxygen combustion of natural gas in the calciner. The gas coming into the carbonator was a simulated flue gas from a coal-fired power plant or cement industry. Several limestone particle size distributions are also tested to further explore the effect of this parameter on the overall performance of this operating mode. The configuration of the reactor system, the operating procedures, and the results are described in detail in this paper. The reactor showed good hydrodynamic stability and stable CO2 capture, with capture efficiencies of up to 70% with a gas mixture simulating the flue gas of a coal-fired power plant.


Subject(s)
Calcium Carbonate/chemistry , Carbon Dioxide/chemistry , Oxygen/chemistry , Power Plants , Calcium Compounds/chemistry , Oxides/chemistry
20.
Faraday Discuss ; 192: 97-111, 2016 10 20.
Article in English | MEDLINE | ID: mdl-27485382

ABSTRACT

Four types of synthetic sorbents were developed for high-temperature post-combustion calcium looping CO2 capture using Longcal limestone. Pellets were prepared with: lime and cement (LC); lime and flour (LF); lime, cement and flour (LCF); and lime, cement and flour doped with seawater (LCFSW). Flour was used as a templating material. All samples underwent 20 cycles in a TGA under two different calcination conditions. Moreover, the prepared sorbents were tested for 10 carbonation/calcination cycles in a 68 mm-internal-diameter bubbling fluidized bed (BFB) in three environments: with no sulphur and no steam; in the presence of sulphur; and with steam. When compared to limestone, all the synthetic sorbents exhibited enhanced CO2 capture performance in the BFB experiments, with the exception of the sample doped with seawater. In the BFB tests, the addition of cement binder during the pelletisation process resulted in the increase of CO2 capture capacity from 0.08 g CO2 per g sorbent (LF) to 0.15 g CO2 per g sorbent (LCF) by the 10th cycle. The CO2 uptake in the presence of SO2 dramatically declined by the 10th cycle; for example, from 0.22 g CO2 per g sorbent to 0.05 g CO2 per g sorbent in the case of the untemplated material (LC). However, as expected all samples showed improved performance in the presence of steam, and the decay of reactivity during the cycles was less pronounced. Nevertheless, in the BFB environment, the templated pellets showed poorer CO2 capture performance. This is presumably because of material loss due to attrition under the FB conditions. By contrast, the templated materials performed better than untemplated materials under TGA conditions. This indicates that the reduction of attrition is critical when employing templated materials in realistic systems with FB reactors.

SELECTION OF CITATIONS
SEARCH DETAIL
...