Part load operation of natural gas fired power plant with CO₂ capture system for selective exhaust gas recirculation

This work investigates base and part load operation of natural gas combined cycle power plant integrated with post-combustion CO2 capture plant and selective exhaust gas recirculation scheme. Decarbonizing of natural gas combined cycle power plant is complex due to the higher flue gas flow rate with the least CO2 content ~ 3–4 vol% with residual 20% O2 and 77% N2 content. Therefore, the effect of series, parallel and hybrid selective exhaust gas recirculation is examined, a concept where selectively CO2 can be recycled back and mixed into the ambient air to the inlet feed of the compressor thereby reducing the flue gas flow rate and enhancing CO2 content at the inlet of capture plant. The study is novel in a way that part-load performance at 80, 60 and 40% for parallel and hybrid scheme of selective exhaust gas recirculation is analyzed through process simulation in Aspen Plus for 606 MW commercial-scale natural gas combined cycle power plant coupled with an amine-based CO2 capture plant. It is found that the simulation results of power plant and CO2 capture plant model agrees well with the experimental results. Further, the performance results show the viability of base and part load operation of natural gas combined cycle power plant integrated with CO2 capture plant by enhancing the CO2 concentration for hybrid configuration to approximately 19 vol%. For parallel configuration, CO2 content increases to around 13–14 vol% at 70% recirculation ratio in comparison to 6.6 vol% for simple EGR at 35% ratio. It is found that the selective exhaust gas recirculation offers more stable combustion by maintaining O2 content at 19 vol% at combustor inlets for parallel and hybrid cases and the flue gas flow rate reduces to 68 and 70%, respectively thus reducing the size of the capture plant. The specific reboiler duty for hybrid, parallel, and series configuration reduces to 3.19, 3.25, and 3.31 MJ/kg CO2, respectively in comparison to 3.54 MJ/kg CO2 for base case natural gas combined cycle power plant coupled with MEA-based CO2 capture unit. Whereas for 80 to 40% load change, the specific reboiler duty drops from 1.78% to 1.14% for parallel and hybrid configurations, respectively. In conclusion, hybrid selective exhaust gas recirculation configuration shows less efficiency penalty from base load to 40% part load and results in a decrease in specific reboiler duty in comparison to parallel configuration. Therefore, the study is innovative in an aspect that part-load performance at 80, 60 and 40% is performed, and results show a similar pattern as of baseload operation.</p

Design and operation of a 20 kWth fluidised bed combustor for biomass oxy-fuel combustion

Due to growing concerns about climate change, the heat and power sector is continuously facing challenges to reduce CO2 emissions. Carbon capture and storage (CCS) is one of the short-medium term measures that can mitigate CO2 emissions emitted from fossil fuels utilisation. Oxy-fuel combustion is a promising technology for CSS that can be integrated into the new and the current fleet of power plants. Biomass is a carbon neutral renewable source of energy that can replace fossil fuels. If the biomass is utilised as a fuel in oxy-fuel combustion it could lead even to negative CO2 emissions. Although the sintering and agglomeration problems associated with the combustion of non-woody biomasses in the fluidised beds are still major issues, fluidised beds have emerged as one of the best among the other proven biomass combustion technologies, mainly due to their fuel flexibility, low SOx and NOx emissions. However, oxy-fuel combustion technology in fluidised beds is in the early stages of development and still needs a lot of research for improvement before its application on full-scale power plants. In this work basic combustion fundamentals of different biomass fuels in terms of energy production were studied using thermogravimetric analysis (TGA) under air, N2, CO2 and selected oxy-fuel (30%O2/70%CO2) reaction environments. Then a 20 kWth bubbling fluidised bed combustor (BFBC) was designed, manufactured and successfully tested for a range of biomass fuels under air and oxy-fuel combustion environments. The agglomeration and sintering behaviour of these biomass fuels during combustion under air was also investigated using different analytical techniques such as SEM-EDX, XRD and XRF. The biomass fuels investigated in this study include domestic wood, industrial wood, miscanthus, wheat straw and peanut shell pellets. The BFBC testing of these biomass fuels focused on the influence of operating conditions, the effect of excess air level and fuel feed rate on the hydrodynamics, temperature profiles and emissions, NOx, CO2 and CO within the BFBC. Air staging can be very effective in reducing NOx emissions of non-woody biomass fuels especially when the secondary air was injected at the higher level with an overall low excess air level. A maximum NOx reduction percentage of 30% was achieved for the non-woody biomasses during air staging combustion. The non-isothermal TGA analyses under N2 and CO2 showed almost identical weight loss (R), reactivity (RM) and activation energy (Ea) profiles in devolatilisation zones. However, when devolatilisation occurred under CO2 conditions at temperatures higher than 700 oC, an additional weight loss was observed for all biomass fuels, being indicative of the contribution of CO2-char gasification reactions. Under air and oxy-fuel (30%O2/70%CO2) results showed almost similar profiles for R, RM and Ea. In oxy-fuel atmospheres, by replacing N2 with CO2 a slight increase in the maximum rate of weight loss (RMax) was observed in both reaction zones for all studied biomasses. The unstaged and staged air combustion experiments in the 20 kWth BFBC showed that higher excess air always led to higher NOx emissions for any of the biomass fuels tested because less CO and char were available in the reactor to promote NOx reductions. Due to the consequence of the high volatile matter content of the biomass fuels, the maximum temperatures were achieved at the top of the dense bed and/or beginning of the freeboard, which suggests that the main combustion reaction takes place in this part of the combustor. Air staging leads to higher temperatures in the freeboard, especially at low excess air levels, as a result of additional combustion in the freeboard under staged air conditions. Air staging can be very effective in reducing NOx emissions of non-woody biomass fuels especially when the secondary air was injected at the higher level with an overall low excess air level. A higher percentage of carbon in ash was obtained while working under air staging conditions than that of without air staging combustion. The results of oxy-fuel combustion tests in the 20 kWth BFBC showed that oxy-fuel combustion was different from air combustion in several ways, including reduced gas temperatures, delayed flame ignition, increased CO emissions under 21%O2/79%CO2 and 25%O2/75%CO2 oxy-mixtures. Many of these parameters were associated with differences in properties of the main diluting gases CO2 and N2 in oxy-fuel and air combustion respectively. In order to match the biomass oxy-fuel combustion gas temperatures to those of air combustion, the oxygen concentration in the mixture of O2/CO2 has to be increased to 30% or higher. Moreover, the oxy-fuel combustion with 30%O2/70%CO2 has shown higher efficiencies than air, which indicates biomass fuels can be successfully combusted in the BFBC under oxy-fuel combustion conditions. The agglomeration and sintering behaviour was observed under continuous air combustion conditions in the 20 kWth BFBC. The analysis using SEM-EDX, XRD and XRF concluded that the potassium present in wheat straw was mainly responsible for agglomeration, which was detected in the form of KCl and K2O in the bed material and cyclone ash samples

Formal and Executable Specification of Random Waypoint Mobility Model Using Timed Coloured Petri Nets for WMN

The wireless mesh network (WMN) is an emerging and cost-effective alternative paradigm for the next generation wireless networks in many diverse applications. In the performance evaluation of routing protocol for the WMN, it is essential that it should be evaluated under realistic conditions. The usefulness of specific mobility protocol can be determined by selection of mobility model. This paper introduces a coloured Petri nets (CP-nets) based formal model for implementation, simulation, and analysis of most widely used random waypoint (RWP) mobility model for WMNs. The formal semantics of hierarchical timed CP-nets allow us to investigate the terminating behavior of the transitions using state space analysis techniques. The proposed implementation improves the RWP mobility model by removing the “border effect” and resolves the “speed decay” problem

Implications of advanced wastewater treatment: Electrocoagulation and electroflocculation of effluent discharged from a wastewater treatment plant

In this research, wastewater treatment was inspected on a pilot-scale wastewater treatment plant by electrochemical techniques, electrocoagulation (EC), electroflotation (EF) and electrophoretic deposition (EPD). The wastewater samples have been characterised by applying different parameters to determine optimum working conditions of the electrocoagulation reactor. Two electrodes have been tested separately with an outflow coming from primary and secondary sedimentation tank. The outflows from these tanks are introduced in EC reactor then EC reactor efficacy is determined for the removal of chemical oxygen demand (COD), suspended solids, micropollutants and amount of coagulants in agglomerates at different current densities. The amounts of suspended solids (SS) in influent and effluent streams were determined by the membrane filtration technique. The operational applied current values range from 1–4 A in the case of COD removal by Fe and Al. While for SS aggregation the applied current ranges from 0.5–3 A and inflow rate was tested from 250 to 500 L/h. The pH of outflows increased by increasing applied current and both of these parameters were found a positive increase in the amount of SS aggregations after EC treatment. Furthermore, the COD removal efficiency was found to be 56–57 % and 12–18 % in case Fe and Al electrode respectively after EC treatment. The results showed that applied current is the most effective parameter, whereas the aluminium electrodes have produced more amounts of flocs and bubbles in comparison to iron electrodes at similar amount of current density

Future of ammonium nitrate after Beirut (Lebanon) explosion

Ammonium nitrate (NH4NO3) is a chemical compound that is mostly found as a colorless and/or white to gray crystalline solid, odorless beads, and easily soluble in water. The molecular weight, specific gravity, melting, and boiling point of NH4NO3 are 80.06, 1.725, 169.51 °C, and 210 °C, respectively (Rao, 2014). Higher temperature (>210 °C) easily decomposes NH4NO3 and producing toxic gasses, especially nitrogen oxides, and may also cause an explosion (Han et al., 2015). At room temperature, pure NH4NO3 neither flammable or combustible, but when heated, normally, it is decomposed into non-explosive gases such as oxygen. Nevertheless, it can also be decomposed into explosive material by detonation (Xia et al., 2019). Ammonium nitrate is strongly oxidant that easily detonates under certain circumstances, which include higher temperature (>210 °C), confinement, and impurities (Health Safety Executive, 2004).The authors would like to appreciate the valuable comments from the editors and anonymous reviewers to improve the quality of this study. The authors confirm that no funding was received for his work

Digital Storytelling: A Pedagogical Approach to Enhance Young Learners Social-Emotional Skills

This qualitative research examines the pedagogical potential of digital storytelling in promoting the social-emotional competence of young students. With an emphasis on technology integration in education, the study investigates how digital storytelling can promote social skills and emotional intelligence, empathy, self-awareness, and interpersonal skills among elementary school students. The study was qualitative in nature. Before the intervention, we conducted an in-depth needs assessment to determine the student's specific social-emotional issues. The research involved intensive interviews with parents and teachers to gain insight into where assistance was needed. Based on the interview findings, we focused on enhancing students' social skills, self-management, relationship skills, problem-solving abilities, self-awareness, and time-management skills. Research was conducted in the Government Primary School in District Shangla, KPK, Pakistan. The study duration was six weeks (April- May 2024). The sample size was grade 5th students. There were 57 grade 5th students, of whom 33 were boys and 24 were girls. In the participants' group, the mean age was 10-11 years, and they had varied academic and family backgrounds. This specific age group is important for social-emotional development. The findings demonstrate how digital storytelling can create emotionally charged, relatable, and immersive learning experiences that help young learners improve their social-emotional skills. According to the study's findings, students who engaged in digital storytelling showed significant increases in empathy and comprehension because they could relate to the characters' sentiments and circumstances. Students' communication and self-expression skills increased significantly, and they demonstrated greater confidence in expressing their ideas and feelings. Collaborative digital storytelling projects that honed interpersonal and cooperation skills facilitated effective student collaboration. The study discovered that their self-awareness increased when participants engaged in reflective activities and shared stories about their feelings and experiences. Based on the study's findings, digital storytelling is an effective pedagogy to apply in promoting young learners' social-emotional skills. By applying technology and storytelling, instructors can design learning experiences that are relevant, engaging, and empathetic. This strategy assists students in holistically developing their social-emotional talents while also providing them with the tools they need to deal with the problems of social interactions in the digital age. Future research could examine the long-term impacts of digital storytelling on students' social-emotional development and its use in a variety of educational settings

Green synthesis and biological evaluation of novel 5-fluorouracil derivatives as potent anticancer agents

This study reports the formation of 5-FU co-crystals with four different pharmacologically safe co-formers; Urea, Thiourea, Acetanilide and Aspirin using methanol as a solvent. Two fabrication schemes were followed i.e., solid-state grinding protocol, in which API and co-formers were mixed through vigorous grinding while in the other method separate solutions of both the components were made and mixed together. The adopted approaches offer easy fabrication protocols, no temperature maintenance requirements, no need of expensive solvents, hardly available apparatus, isolation and purification of the desired products. In addition, there is no byproducts formation, In fact, a phenomenon embracing the requirements of green synthesis. Through FTIR analysis; for API the Nsingle bondH absorption frequency was recorded at 3409.02 cm−1 and that of single bondCdouble bondO was observed at 1647.77 cm−1. These characteristics peaks of 5-FU were significantly shifted and recorded at 3499.40 cm−1 and 1649.62 cm−1 for 5-FU-Ac (3B) and 3496.39 cm−1 and 1659.30 cm−1 for 5-FU-As (4B) co-crystals for Nsingle bondH and single bondCdouble bondO groups respectively. The structural differences between API and co-crystals were further confirmed through PXRD analysis. The characteristic peak of 5-FU at 2θ = 28.79918o was significantly shifted in the graphs of co-crystals not only in position but also with respect to intensity and FWHM values. In addition, new peaks were also recorded in all the spectra of co-formers confirming the structural differences between API and co-formers. In addition, percent growth inhibition was also observed by all the co-crystals through MTT assay against HCT 116 colorectal cell lines in vitro. At four different concentrations; 25, 50, 100 and 200 µg/mL, slightly different trends of the effectiveness of API and co-crystals were observed. However; among all the co-crystal forms, 5-FU-thiourea co-crystals obtained through solution method (2B) proved to be the most effective growth inhibitor at all the four above mentioned concentrations

TAXONOMIC AND OTOLITH SHAPE PARAMETERS OF NINE SYMPATRIC CATFISHES COMMERCIALLY HARVESTED IN PAKISTAN

Točna reorganizacija uzgojnih vrsta ključna je za odgovarajuće praćenje ribarstva, ali se često na bilježi. U ovoj studiji pokušalo se dati točan opis vrsta na temelju taksonomije riba i parametara oblika otolita devet vrsta morskih somova iz Pakistana. Lapilus, najveći otolit somova, uključuje položaj umba, strukturu prednje mezijalne projekcije (amp), incisura linea basalis (ilb) i oznake sulcus lapilli (slm) kod devet ariidnih somova. Analiza diskriminativne funkcije provedena je pomoću dvadeset i dva morfometrijska parametra devet vrsta, a pokazala je značajne varijacije između duljine maksilarih brkova, adipozne duljine i preorbitalne duljine, koji su istaknuti kao osnovni diskriminirajući znakovi. Za vrste bez brkova, kao što su Batrachocephalus mino i Osteogeneiosus militaris, utvrđeno je da su udaljene. Taksonomska svojstva rodova Netuma i Plicofollis preklapaju se zbog kratke duljine masne peraje. Ipak, vrste Arius arius, Sciades sona i Nemapterxy caelatus razlikovale su se po umjerenoj duljini masne peraje. Preorbitalna duljina Netuma bilineata ima kratku i zaobljenu njušku, dok N. thalassina ima dugu i šiljastu njušku, što je karakteristika obje vrste. Podudarna upotreba taksonomije riba i parametara oblika otolita učinkovit je alat za identifikaciju soma koji pomaže u odgovarajućim programima uzorkovanja i upravljanju ribarstvom u Pakistanu.Accurate reorganization of harvested species is essential for appropriate fisheries monitoring but is often unnoticed. In this study, an attempt was made to provide an accurate species description based on fish taxonomy and otolith shape parameters of nine sea catfishes living in Pakistan. The lapillus, the largest otolith of catfishes, includes the position of the umbo, the structure of the anterior mesial projection (amp), the incisura linea basalis (ilb) and sulcus lapilli marks (slm) in nine ariid catfishes. Discriminant function analysis was performed using twenty-two morphometric parameters of nine species, and showed significant variations between the length of the maxillary barbel, adipose length and preorbital length, which were highlighted as basic discriminating characters. Species without barbells, such as Batrachocephalus mino and Osteogeneiosus militaris, were found to be distant. The taxonomic characters of the genera Netuma and Plicofollis overlapped due to a short adipose fin length. Nevertheless, species Arius arius, Sciades sona and Nemapterxy caelatus differed in a moderate adipose fin length. The preorbital length of Netuma bilineata has a short and rounded snout, while N. thalassina has a long and pointed snout, which is a distinguishing characteristic of both species. The coincident use of fish taxonomy and otolith shape parameters is an effective tool for catfish identification which helps in appropriate fisheries sampling programs and management in Pakistan whenever implemented

Non-Timber Forest Products Collection Affects Education of Children in Forest Proximate Communities in Northeastern Pakistan

Non-timber forest products (NTFPs) are crucial in driving the economy of communities living inside or around forests. The scarcity of business and employment opportunities often push the forest proximate communities to tap a range of NTFPs for earning their livelihoods. In many forest-based communities around the world, children are actively involved in NTFPs collection, which is likely to affect the socioeconomic paradigms of these children. We aim to investigate how the NTFP collection venture affects the education of the children involved in the forest proximate communities of Azad Jammu and Kashmir (AJK), Pakistan. A stratified sampling followed by a series of focus group discussions and one-to-one interviews were carried out to collect information on collection behaviour, patterns, income generation, and other socioeconomic variables. We used a binary logistic regression model to explain children’s state of attending schools using a range of socioeconomic variables. The empirical evidence showed that 42% of the NTFP-collecting children were not going to school, and nearly two-thirds were working in unfavourable working environments. The regression model showed that the role and behaviour of contractors, along with factors like household conditions, were important factors in employing children for long working hours. The study has implications for reforming policies regarding the nexus of income generation and education in the forest-based communities

Adverse drug reaction monitoring and reporting among physicians and pharmacists in Pakistan:A cross-sectional study

Background: The success of a reporting system of adverse drug reaction (ADR) depends on the knowledge, attitudes, and practices of the health care professionals. However, due to a lack of knowledge and poor contribution by healthcare workers, ADR remains underreported. To improve safety, proper identification and ADR reporting is necessary. Objective: This study was carried out to determine knowledge, attitude, and practices of ADR among physicians and pharmacists working in Pakistan and the factors which encourage and discourage effective reporting. Methods: A cross-sectional study was conducted using a pretested questionnaire. Questionnaires were distributed among 333 physicians and 34 pharmacists with a 95.5% response rate. The Statistical Package for Social Science (SPSS) was used for data analysis. Results: Pharmacists have more knowledge regarding ADR compared to physicians (47.1% vs. 13.8%, p < 0.001). Pharmacists also have a positive attitude compared to physicians (97.1% vs. 76.3%, p < 0.001). No significant difference was noticed in ADR practice by physicians and pharmacists (12.3% vs. 11.8, p = 0.92). The seriousness of ADR was the main factor that encouraged nearly all pharmacists to report, whereas among physician’s, seriousness and the unusualness of reaction, the new drug involvement, and confidence in diagnosis were the factors which encouraged them to report ADR. Conclusion: Overall, pharmacists had more knowledge and a positive attitude regarding ADR reporting compared to physicians, but practices of ADR reporting remained the same among both. Therefore, it is suggested that educational interventions, along with training programs, should be developed