Modeling of strippers for CO₂ capture by aqueous amines

textThis work evaluates stripper performance for CO₂ capture using seven potential solvent formulations and seven stripper configurations. Equilibrium and rate models were developed in Aspen Custom Modeler (ACM). The temperature approach on the hot side of the cross exchanger was varied between 5 - 10°C. The results show that operating the cross exchanger at a 5°C approach results in 12% energy savings for a 7m MEA rich solution of 0.563 mol/mol Alk and 90% CO₂ removal. For solvents with [Delta]H[subscript abs] < 60 kJ/gmol CO₂, stripping at 30 kPa is more attractive than stripping at 160 kPa. Normal pressure (160 kPa) favors solvents with high heats of desorption. The best solvent and process configuration, matrix with MDEA/PZ, offers 22% and 15% energy savings over the baseline and improved baseline, respectively, with stripping and compression to 10 MPa. The energy requirement for stripping and compression to 10 MPa is about 20 % of the power output from a 500 MW power plant with 90% CO2 removal. Rate model results show that a 'short and fat' stripper requires 7 to 15% less equivalent work than a 'tall and skinny' one. The optimum stripper design could be one that operates between 50% and 80% flood at the bottom. Stripping at 30 kPa and 160 kPa require 230 s and 115 s of effective packing volume to get an equivalent work 4% greater than the minimum. Stripping at 30 kPa with [Delta]T = 5°C was controlled by mass transfer with reaction in the boundary layer and diffusion (88% resistance at the rich end and 71% resistance at the lean end) and mass transfer with equilibrium reactions (84% resistance at the rich end and 74% resistance at the lean end) at 160 kPa. The model was validated with data obtained from pilot plant experiments at the University of Texas with 5m K⁺/2.5m PZ and 6.4m K⁺/1.6m PZ under normal pressure and vacuum conditions using Flexipac AQ Style 20 structured packing. Foaming was experienced during tests. The effective packing height was 5.09m for 5m K⁺/2.5m PZ and 6.47m for 6.4m K⁺/1.6m PZ.Chemical Engineerin

Testicular histo-morphometry and semen parameters of West African Dwarf bucks

This study evaluates the gross and histo-morphometry of the testes as well as the semen parameters of West African Dwarf (WAD) goats bred and raised in Abeokuta, Ogun State, Nigeria. Five apparently healthy WAD bucks were used for this study were electro-ejaculated once weekly for two weeks. Testicular weight, gonadosomatic index, seminiferous tubular diameter and seminiferous epithelial height were measured using standard techniques. Semen parameters which included volume, colour, motility and concentration as well as scrotal circumference were also determined using standard procedures. All data were recorded as mean ± standard deviation, subjected to descriptive statistics and Pearson’s correlation analysis at p &lt; 0.05. Our findings revealed that the testicular gross morphometric values significantly correlate with the histometric values with normal testicular histo-architecture suggestive of typical spermatogenesis. Furthermore, the scrotal circumference showed positive relationship with both the gross and histometric parameters of the testis. However, there was no significant correlation between scrotal circumference and semen parameters. This information could improve understanding of reproduction in the WAD buck.Keywords: Semen evaluation, Spermatogenesis, Testicular morphometry, Reproduction, WAD goa

Effect of season on reproduction in west African Dwarf Bucks

This study was conducted to determine effects of season on some reproductive parameters of WAD bucks. Nine apparently healthy WAD bucks, aged between 18 and 24 months and weighing 8-15 Kg, were used to evaluate the effect of seasonal variations on Live-Weight (LW), Rectal Temperature (RT) and Scrotal Circumference (SC) between January and December, 2013. Semen was collected monthly by electro-ejaculation method and evaluated for spermiogram using standard techniques. Results were compared between and within groups using analysis of variance for repeated measures. Values are significant at p ˂ 0.05. Seasonal variation significantly (p ˂ 0.05) affected RT and SC except total sperm morphological abnormalities. Means for the total sperm morphological abnormalities were 7.42 ± 3.21% (late dry), 3.42 ± 0.36% (early rainy), 6.33 ± 0.33% (late rainy) and 7.25 ± 1.18% (early dry). The total morphologically abnormal spermatozoa reported for the seasonal study was 6.10%. It was thus concluded that seasons does not have significant effect on the spermiogram of WAD buck, however, they appeared to be most fertile during the early and late rainy seasons and least potentially fertile during early and late dry seasons.Keywords: Spermiogram, Season, Buck, Rectal temperature, Reproductio

Diagnosis and surgical management of acanthomatous ameloblastoma in a 5-month-old female Boerboel puppy

A five-month-old female Boerboel puppy presented with a rapidly expanding fibrous growth around the canine tooth of the right maxilla was diagnosed as having acanthomatous ameloblastoma based on findings from skull radiography, cytology of fine needle aspiration, biopsy and histopathology of resected growth. Lateral radiograph of the skull revealed moderate osteolysis of the maxilla with presence ofun-erupted maxillary canine teeth. Cytology of fine needle aspirate from the growth showed clusters of epithelial cells that were&nbsp; hyperchromatic and showing palisade arrangement. The mass was surgically resected using diathermy instrument following general anaesthesia using combination of intramuscular injection of xylazine (0.5mg/kg), and intravenous injection of propofol (4mg/kg). Post-operative management included Ibuprofen suspension (100mg) administered for 3-days, intravenous vincristine (0.5mg/m2 ) once weekly and oral cyclophosphamide (50mg) was administered twice weekly for six weeks. Histopathology of the growth showed odontogenic epithelium embedded in pulp ectomesenchyme. Features of odontogenic epithelium include palisading epithelium with anti-basilar nuclei and centrally located cells having features of stellate reticulum. This is probably the first reported case of acanthomatous ameloblastoma in a Boerboel puppy that was successfully managed. Keywords: Acanthomatous, Ameloblastoma, Boerboel-puppy, Chemotherapy, Odontoi

Carbon capture from natural gas combined cycle power plants: Solvent performance comparison at an industrial scale

Natural gas is an important source of energy. This article addresses the problem of integrating an existing natural gas combined cycle (NGCC) power plant with a carbon capture process using various solvents. The power plant and capture process have mutual interactions in terms of the flue gas flow rate and composition vs. the extracted steam required for solvent regeneration. Therefore, evaluating solvent performance at a single (nominal) operating point is not indicative and solvent performance should be considered subject to the overall process operability and over a wide range of operating conditions. In the present research, a novel optimization framework was developed in which design and operation of the capture process are optimized simultaneously and their interactions with the upstream power plant are fully captured. The developed framework was applied for solvent comparison which demonstrated that GCCmax, a newly developed solvent, features superior performances compared to the monoethanolamine baseline solvent

Cost-effectiveness of pin-in-fibreglass cast versus Kirschner-Ehmer type I external skeletal fixator in the management of transverse radius-ulna fractures in dogs

The cost of medical care is an important issue all over the world. With worsening global economy and the poverty inherent in low earning  economies in the third world countries, economic considerations have always remained a major determinant factor in the choice of treatment. In this study, the cost-effectiveness of pin-in-fibreglass cast fixator (PFCF) was comparatively evaluated against a commercially available fixator  (Kirschner-Ehmer type I external fixator) (KESF) in the management of induced closed transverse mid-shaft radius-ulna fractures in dogs. Four adult (2 males and 2 females) dogs with closed transverse mid-shaft radius-ulna fractures were used for this study. These dogs were randomly assigned to two groups (A and B) with each group made up of two dogs. Radius-ulna fractures were created in all the dogs under injectable anaesthesia as follows: Group A; PFCF, and Group B; KESF. A cost analysis was performed using the duration of operative and post-operative procedures, duration of morbidity period, direct and indirect labour cost, and cost of dog-hour lost during the morbidity period as economic indices. The overall duration of the operative and the entire post-operative procedures were 5.5±0.14 and 22±0.21 hours (1:4.4) for PFCF and KESF (P&gt;0.05) respectively. The morbidity period was 9 and 8 weeks for PFCF and KESF respectively. The average cost of medical care (in 2015 $1 US ≈ N198 Nigerian Naira) was$81.8 and $294 (1:3.6) for PFCF and KESF respectively. The cost benefit analysis based on the economic loss due to dog-hour lost during the morbidity period were$990. 9 and $1103 (1:1.1) for PFCF and KESF respectively. In conclusion, PFCF is faster and easier to perform, and more economical than the KESF technique despite the longer morbidity period associated with it. This is accounted for by the lower cost of fixative and hospital charges.Keywords: Dog, Cost effectiveness, Pin-in-fiberglass cast, Kirschner-Ehmer external fixative, Radius-ulna, fracture

A comparative study of MEA and DEA for post-combustion CO2 capture with different process configurations

This paper presented a comparative study of monoethanolamine (MEA) and diethanolamine (DEA) for post-combustion CO2 capture (PCC) process with different process configurations to study the interaction effect between solvent and process. The steady state process model of the conventional MEA-based PCC process was developed in Pro/II® and was validated with the experimental data. Then ten different process configurations were simulated for both MEA and DEA. Their performances in energy consumption were compared in terms of reboiler duty and total equivalent work. The results show that DEA generally has better thermal performances than MEA for all these ten process configurations. Seven process configurations provide 0.38%–4.61% total energy saving compared with the conventional PCC process for MEA, and other two configurations are not favourable. For DEA, except one configuration, other process configurations have 0.27%–4.50% total energy saving. This work also analyzed the sensitivities of three key parameters (amine concentration, stripper pressure and lean solvent loading) in conventional process and five process modifications to show optimization strategy

Process modelling, validation and analysis of rotating packed bed stripper in the context of intensified CO2 capture with MEA

Rotating packed bed (RPB) system has applications in CO2 removal using chemical solvents which can reduce the size about ten times compared to common packed bed (PB) system. In this study, RPB stripper using monoethanolamine (MEA) solution is modelled in gPROMS® software. The model has been validated using experimental data from literature and show good agreement. In addition to stripper modelling and validation, the process analysis is accomplished in this study by assessing the influence of four parameters namely rotor speed, reboiler temperature, flow rate of rich liquid, and pressure on desorption efficiency and desorption energy

CO2 Capture by Absorption With Potassium Carbonate Quarterly Report

The objective of this work is to improve the process for CO{sub 2} capture by alkanolamine absorption/stripping by developing an alternative solvent, aqueous K{sub 2}CO{sub 3} promoted by piperazine. CO{sub 2} mass transfer rates are second order in piperazine concentration and increase with ionic strength. Modeling of stripper performance suggests that 5 m K{sup +}/2.5 m PZ will require 25 to 46% less heat than 7 m MEA. The first pilot plant campaign was completed on June 24. The CO{sub 2} penetration through the absorber with 20 feet of Flexipac{trademark} 1Y varied from 0.6 to 16% as the inlet CO{sub 2} varied from 3 to 12% CO{sub 2} and the gas rate varied from 0.5 to 3 kg/m{sup 2}-s

Epidemiological and Entomological Evaluations after Six Years or More of Mass Drug Administration for Lymphatic Filariasis Elimination in Nigeria

The current strategy for interrupting transmission of lymphatic filariasis (LF) is annual mass drug administration (MDA), at good coverage, for 6 or more years. We describe our programmatic experience delivering the MDA combination of ivermectin and albendazole in Plateau and Nasarawa states in central Nigeria, where LF is caused by anopheline transmitted Wuchereria bancrofti. Baseline LF mapping using rapid blood antigen detection tests showed mean local government area (LGA) prevalence of 23% (range 4–62%). MDA was launched in 2000 and by 2003 had been scaled up to full geographic coverage in all 30 LGAs in the two states; over 26 million cumulative directly observed treatments were provided by community drug distributors over the intervention period. Reported treatment coverage for each round was ≥85% of the treatment eligible population of 3.7 million, although a population-based coverage survey in 2003 showed lower coverage (72.2%; 95% CI 65.5–79.0%). To determine impact on transmission, we monitored three LF infection parameters (microfilaremia, antigenemia, and mosquito infection) in 10 sentinel villages (SVs) serially. The last monitoring was done in 2009, when SVs had been treated for 7–10 years. Microfilaremia in 2009 decreased by 83% from baseline (from 4.9% to 0.8%); antigenemia by 67% (from 21.6% to 7.2%); mosquito infection rate (all larval stages) by 86% (from 3.1% to 0.4%); and mosquito infectivity rate (L3 stages) by 76% (from 1.3% to 0.3%). All changes were statistically significant. Results suggest that LF transmission has been interrupted in 5 of the 10 SVs, based on 2009 finding of microfilaremia ≥1% and/or L3 stages in mosquitoes. Four of the five SVs where transmission persists had baseline antigenemia prevalence of >25%. Longer or additional interventions (e.g., more frequent MDA treatments, insecticidal bed nets) should be considered for ‘hot spots’ where transmission is ongoing