THE EFFECT ON THE THERMAL EFFICIENCY OF LIME ADDED TO THE COMBUSTION CHAMBER FOR RETENTION ON SULPHUR

ABSTRACT

In order to prevent the emission of SO_x, with the flue gas, certain amount of the sulphur of the coal can be retained by adding an adequate amount of lime in the combustion chamber. In this study, two series of experiments were conducted by adding lime at the molar ratios of CaO/S = 0·5 to 2·0 using Ankara-Beypazan lignites, which have around 5 % sulphur content as received form. In one of the series lime was added directly in to the lump coal, and in the other, coal was briquetted together with lime using molasses as binder. It was observed from the experimental results that the increase in the lime ratio leads to an increase in the retained sulphur percentage while it leads to a considerable decrease in thermal efficiency. In order to retain 50 % of sulphur, it was necessary to add lime into lump coal at a CaO/S molar ratio of at least 1,1. This minimum ratio was 0·70 for briquetted coal. When lime was added at these ratios, the thermal efficiencies in the first case dropped to as low as 82 % and to 92 % in the second.     

The long‐term effects of arteriovenous fistula creation on the development of pulmonary hypertension in hemodialysis patients

The aim of this prospective study was to evaluate long‐term effects of arteriovenous fistula (AVF) on the development of pulmonary arterial hypertension (PAH) and the relationship between blood flow rate of AVF and pulmonary artery pressure (PAP) in the patients with end‐stage renal disease (ESRD). This prospective study was performed in 20 patients with ESRD. Before an AVF was surgically created for hemodialysis, the patients were evaluated by echocardiography. Then, an AVF was surgically created in all patients. After mean 23.50 ± 2.25 months, the second evaluation was performed by echocardiography. Also, the blood flow rate of AVF was measured at the second echocardiographic evaluation. Pulmonary arterial hypertension was defined as a systolic PAP above 35 mmHg at rest. Mean age of 20 patients with ESRD was 55.05 ± 13.64 years; 11 of 20 patients were males. Pulmonary arterial hypertension was detected in 6 (30%) patients before AVF creation and in 4 (20%) patients after AVF creation. Systolic PAP value was meaningfully lower after AVF creation than before AVF creation (29.95 ± 10.26 mmHg vs. 35.35 ± 7.86 mmHg, respectively, P: 0.047). However, there was no significant difference between 2 time periods in terms of presence of PAH (P>0.05). Pulmonary artery pressure did not correlate with blood flow rate of AVF and duration after AVF creation (P>0.05). In hemodialysis patients, a surgically created AVF has no significant effect on the development of PAH within a long‐term period. Similarly, blood flow rate of AVF also did not affect remarkably systolic PAP within the long‐term period.     

Investigation of catalytic effects of the proton and Lewis acids on oligomerization and chemical polymerization of pyrrole

Protonation and oligomerization mechanisms of pyrrole monomer were elucidated in the presence of acid such as HBF₄ and Lewis acid such as AlCl₃, FeCl₃ in acetonitrile solutions, using experimental methods such as UV-vis and AA spectroscopy and semi-empirical AM1 calculations. It was observed that pyrrole interacts with proton and Lewis acids on similar mechanisms to produce pyrrole oligomers. The theoretical studies predicted that the both types of acids add to the pyrrole ring on Cβ atom. These studies also showed that FeCl₃, which is used as oxidative agent in the chemical polymerizations, adds to the polypyrrole chain as well.     

Economics of herbaceous bioenergy crops for electricity generation: Implications for greenhouse gas mitigation

This paper examines the optimal land allocation for two perennial crops, switchgrass and miscanthus that can be co-fired with coal for electricity generation. Detailed spatial data at county level is used to determine the costs of producing and transporting biomass to power plants in Illinois over a 15-year period. A supply curve for bioenergy is generated at various levels of bioenergy subsidies and the implications of production for farm income and greenhouse gas (GHG) emissions are analyzed. GHG emissions are estimated using lifecycle analysis and include the soil carbon sequestered by perennial grasses and the carbon emissions displaced by these grasses due to both conversion of land from row crops and co-firing the grasses with coal. We find that the conversion of less than 2% of the cropland to bioenergy crops could produce 5.5% of the electricity generated by coal-fired power plants in Illinois and reduce carbon emissions by 11% over the 15-year period. However, the cost of energy from biomass in Illinois is more than twice as high as that of coal. Costly government subsidies for bioenergy or mandates in the form of Renewable Portfolio Standards would be needed to induce the production and use of bioenergy for electricity generation. Alternatively, a modest price for GHG emissions under a cap-and-trade policy could make bioenergy competitive with coal without imposing a fiscal burden on the government.     

NATURAL ZEOLITES IN AIR DRYING

The local clinoptilolite from Bigadis region in Turkiye, was used for air drying in packed column. The effective diffusion coefficient of water in natural zeolite was found as 5×10^-10 m² s^-1 from isothermal uptake measurements. Effects of packing height and airvelocity on breakthrough curves were studied.     

Web based medical decision support system application of Coronary Heart Disease diagnosis with Boolean functions minimization method

Heart and vein diseases are one of the most important health problems. The number of the people who died of heart and vein diseases is more than the number of the people who died of all other health problems and natural disasters. In order to decrease this number, the intervention must be started very earlier and people must be informed about this subject. In this study, Medical Expert System has been used all the probabilities of CHD has been determined (9 symptoms, 2⁹ = 512 different occasions) and from these probabilities, an accuracy table has been formed. This accuracy table has been simplified with the Boolean functions simplifying methods. 94 rules have been achieved by the Boolean functions minimization method. The rules achieved have formed the Expert System’s rule base. 303 patients’ values have been compared with the realized Expert System. The Medical Expert System which was formed as a result of the evaluation has evaluated men with 86.5%, women with 84.5% and in general with 86.1% accuracy rate.     

A GPU-assisted hybrid model for real-time crowd simulations

In this paper, we propose two new techniques for real-time crowd simulations; the first one is the clustering of agents on the GPU and the second one is incorporating the global cluster information into the existing microscopic navigation technique. The proposed model combines the agent-based models with macroscopic information (agent clusters) into a single framework. The global cluster information is determined on the GPU, and based on the agents' positions and velocities. Then, this information is used as input for the existing agent-based models (velocity obstacles, rule-based steering and social forces). The proposed hybrid model not only considers the nearby agents but also the distant agent configurations. Our test scenarios indicate that, in very dense circumstances, agents that use the proposed hybrid model navigate the environment with actual speeds closer to their intended speeds (less stuck) than the agents that are using only the agent-based models.