Steady state simulation and exergy analysis of supercritical coal-fired power plant with CO₂ capture

Integrating a power plant with CO₂ capture incurs serious efficiency and energy penalty due to use of energy for solvent regeneration in the capture process. Reducing the exergy destruction and losses associated with the power plant systems can improve the rational efficiency of the system and thereby reducing energy penalties. This paper presents steady state simulation and exergy analysis of supercritical coal-fired power plant (SCPP) integrated with post-combustion CO₂ capture (PCC). The simulation was validated by comparing the results with a greenfield design case study based on a 550 MWe SCPP unit. The analyses show that the once-through boiler exhibits the highest exergy destruction but also has a limited influence on fuel-saving potentials of the system. The turbine subsystems show lower exergy destruction compared to the boiler subsystem but more significance in fuel-saving potentials of the system. Four cases of the integrated SCPP-CO2 capture configuration was considered for reducing thermodynamic irreversibilities in the system by reducing the driving forces responsible for the CO₂ capture process: conventional process, absorber intercooling (AIC), split-flow (SF), and a combination of absorber intercooling and split-flow (AIC + SF). The AIC + SF configuration shows the most significant reduction in exergy destruction when compared to the SCPP system with conventional CO₂ capture. This study shows that improvement in turbine performance design and the driving forces responsible for CO₂ capture (without compromising cost) can help improve the rational efficiency of the integrated system

Comparative antimicrobial activities of aloe vera gel and leaf

The comparative antimicrobial activities of the gel and leaf of Aloe vera were tested against Staphylococcus aureus, Pseudomonas aeruginosa, Trichophyton mentagraphytes, T. schoeleinii, Microsporium canis and Candida albicans. Ethanol was used for the extraction of the leaf after obtaining the gel from it. Antimicrobial effect was measured by the appearance of zones of inhibition.Antimicrobial susceptibility test showed that both the gel and the leaf inhibited the growth of S. aureus (18.0 and 4.0 mm, respectively). Only the gel inhibited the growth of T. mentagrophytes (20.0 mm), while the leaf possesses inhibitory effects on both P. aeruginosa and C. albicans. The results of this study tend to give credence to the popular use of both Aloe vera gel and leaf

Simplification of detailed rate-based model of post-combustion CO₂ capture for full chain CCS integration studies

As post-combustion CO₂ capture (PCC) technology nears commercialisation, it has become necessary for the full carbon capture and storage (CCS) chain to be studied for better understanding of its dynamic characteristics. Model-based approach is one option for economically and safely reaching this objective. However, there is need to ensure that such models are reasonably simple to avoid the requirement for high computational time when carrying out such study. In this paper, a simplification approach for a detailed rate-based model of post-combustion CO₂ capture with solvents (rate-based mass transfer and reactions assumed to be at equilibrium) is presented. The simplified model can be used in model-based control and/or full chain CCS simulation studies. With this approach, we demonstrated significant reduction in CPU time (up to 60%) with reasonable model accuracy retained in comparison with the detailed model

Biodiesel from microalgae : the use of multi-criteria decision analysis for strain selection

Microalgae strain selection is a vital step in the production of biodiesel from microalgae. In this study, Multi-Criteria Decision Analysis (MCDA) methodologies are adopted to resolve this problem. The aim of this study is to identify the best microalgae strain for viable biodiesel production. The microalgae strains considered here are Heynigia sp., Scenedesmus sp., Niracticinium sp., Chlorella vulgaris, Chlorella sorokiniana and Auxenochlorella protothecoides. The five MCDA methods used to evaluate different strains of microalgae are Analytic Hierarchy Process (AHP), Weighted Sum Method (WSM), Weighted Product Method (WPM), Discrete Compromise Programming (DCP) and Technique for the Order of Preference to the Ideal Solution (TOPSIS). Pairwise comparison matrices are used to determine the weights of the evaluation criteria and it is observed that the most important evaluation criteria are lipid content and growth rate. From the results, Scenedesmus sp. is selected as the best microalgae strain among the six alternatives due to its high lipid content and relatively fast growth rate. The AHP is the most comprehensive of the five MCDA methods because it considers the importance of each criterion and inconsistencies in the rankings are verified. The implementation of the MCDA methods and the results from this study provide an idea of how MCDA can be applied in microalgae strain selection

The relationship between some physicochemical parameters and plankton composition on fish production in ponds

The effect of physico-chemical parameters and plankton composition on fish production in ponds was investigated in six fish farms for eight weeks. The physicochemical parameters investigated were temperature=25-30 plus or minus C, transparency=0.45-0.57m, dissolved oxygen=3.0-10.9mg/l, pH=6.0-7.7, dissolved carbon dioxide=5.46-28.3mg/l, total alkalinity=44.37-80.0ppm, chemical oxygen demand=31.88-72.18mg/l and biological oxygen demand=0.66-48.34mg/l. Plankton composition varies and was made of four families of phytoplankton namely; Cyanophyceae, Chlorophyceae, Dinophyceae and Diatomida; and four families of zooplankton viz; Protozoa, Rotifera, Copepoda and Dinoflagellates. Farm 1 and 6 recorded the highest average weight of about 1.0kg and average total length of about 40.0cm for the two fish species. This study showed that fish yield was dependable on the quality and management of pond water characteristic

Nonparallel Emotional Speech Conversion

We propose a nonparallel data-driven emotional speech conversion method. It enables the transfer of emotion-related characteristics of a speech signal while preserving the speaker's identity and linguistic content. Most existing approaches require parallel data and time alignment, which is not available in most real applications. We achieve nonparallel training based on an unsupervised style transfer technique, which learns a translation model between two distributions instead of a deterministic one-to-one mapping between paired examples. The conversion model consists of an encoder and a decoder for each emotion domain. We assume that the speech signal can be decomposed into an emotion-invariant content code and an emotion-related style code in latent space. Emotion conversion is performed by extracting and recombining the content code of the source speech and the style code of the target emotion. We tested our method on a nonparallel corpora with four emotions. Both subjective and objective evaluations show the effectiveness of our approach.Comment: Published in INTERSPEECH 2019, 5 pages, 6 figures. Simulation available at http://www.jian-gao.org/emoga

Utilization of family planning services in a Nigerian tertiary hospital: a six year review

Context: Family planning is an integral part of maternal health as its uptake is a significant factor in the reduction of maternal mortality and in ensuring positive child health outcomes.Objectives: To describe prevalence and pattern of contraceptive use, and identify reasons for discontinuation among women accessing family planning facilities.Study design: A six year retrospective review of hospital records of new family planning clinic clients at the teaching hospital was conducted. Data was obtained from the client cards and proportions expressed as simple percentages.Results: A total of 1,284 clients accepted a family planning method during the period. Contraceptive prevalence rate in relation to hospital deliveries was 18·1%. Modal age group of clients was 31–40(50.4%), while modal parity was Para 2-3 (43·4%). A third of the clients sought contraception within 6 months of delivery. Intrauterine contraceptive device was the most common method (65.0%). Information on family planning was mainly from nurses (66.7%). Contraceptive discontinuation rate was 21.2%, mainly due to desire for another pregnancy (62%). Menstrual irregularity and husband's decision were some other reasons.Conclusion: There is an identified need for promotion of uptake of family planning methods. Involvement of men in contraception counselling and services is essential to improve its uptake and continuity.Keywords: Family planning, contraceptives, Ile-Ife, Nigeri

Market Design in the Presence of Repugnancy: A Market for Children

A market-like mechanism for the allocation of children in both the primary market (market for babies) and the secondary market (adoption market) will result in greater social welfare, and hence be more efficient, than the current allocation methods used in practice, even in the face of repugnancy. Since a market for children falls under the realm of repugnant transactions, it is necessary to design a market with enough safeguards to bypass repugnancy while avoiding the excessive regulations that unnecessarily distort the supply and demand pressures of a competitive market. The goal of designing a market for children herein is two-fold: 1) by creating a feasible market for children, a set of generalizable rules and principles can be realized for designing functioning and efficient markets in the face of repugnancy and 2) the presence of a potential, credible and efficient market in the presence of this repugnancy will stimulate debate into the need for such markets in other similar areas, especially in cases creating a tradable market for organs for transplantation, wherein the absence of the transaction is often a death sentence for those who wish to, but are prevented from, participating in the market

Community Greening in Pre and Post Climate Change Knowledge Era in Third World Cities: Case study of Lagos, Nigeria

This paper reviewed the efforts of the government in community greening during pre and post climate change era in third world cities using Lagos, Nigeria as a case study. This was with a view of understanding the importance green space as a measure of adaptation to climate change in recent years in the study area. The study reviewed secondary data on provision of green space in purposively selected scheme and master plan that pre-date climate change era. Primary data in the form of field observation of the location and size of green space initiated within the city in the post climate change knowledge era, particularly in the last past five (5) years were also considered. The study further reviewed contemporary law and policies of the government as an approach to community greening in the city during the pre-climate change era.Finding revealed that the government is keener toward the provision and maintenance of green space in the study area during the post climate change era than during the pre-climate change era. Within the past six years, 14 public parks and 128 landscape garden were created and maintained in the city. Nineteen (19) of these public parks and garden covers a total land area of 314409.43m2 (77.69 acres). Furthermore, an agency was established for the sole aim of promoting or increasing green area in the city. A fine of N50,000 ($318.5) or one year imprisonment is attached to felling of these trees. There was also massive tree planting exercise, between 2009 and 2010, when about 300,000 trees were planted across the city. The study recommended that the use of hard landscaping element around buildings should be discouraged and appropriate authorities should involve the available local associations and non-governmental organizations (NGO) in all their environmental programmes. It concluded that environmental benefits of providing green space should be given utmost priorities because of the importance of greening the environment during this post climate knowledge eraKey Words: Community, Cities, Greening, Climate Change and Third Worl

Autocratic Leadership Within West African Pentecostal Denomination

The purpose of this grounded theory study was to determine whether autocratic leadership theory best explains the nature of leadership in the West African Pentecostal/Charismatic Denomination (PCD) across West Africa and to compare the current leadership practices within the PCD to a biblical and theological framework. Since Africa is the fastest growing Christian continent in the world, it is important to give careful attention to matters arising within the church leadership. The researcher believes that this study helped shed light on leadership challenges within African Christianity, Christian education, and most importantly within the Pentecostal/Charismatic denomination. It also provides information that will advance the literature base within African Christianity as it relates to PCD. Based on the findings, the results suggests that autocratic leadership is the primary leadership structure within most PCD churches in the region. Seventy percent of the survey participants selected single structure leadership as the leadership style in their local church while the remaining thirty percent of the participants selected shared leadership. The majority, 70%, of the participants who perceived their church was governed by a group of individuals, are also of the opinion that single structure leadership is still presently practiced in their local church and that one single individual has the autonomous power to make key decisions. The findings revealed three types of leadership structure within PCD churches in West Africa