Aysel T. Atimtay

Combustion of Volatile Matter in Fluidized Beds

The change of the volatiles burn-out time has been investigated for different particle sizes, superficial velocities, volatile matter content and masses charged. The results have shown that the volatiles take about 3–12 sec to burn for the particle size(1.52–3.06mm) and velocity range (0.38–0.58m/s) studied. The radial velocity of the volatiles coming out of a particle was found to be close to Umf. The surface flux of volatiles increases with particle size. The volatiles affect the combustion characteristics of the remaining char.

Chemical composition of rainwater at EMEP station in Ankara, Turkey

Abstract The chemical characteristics of rainfall and its seasonal variation at the EMEP (The Cooperative Programme for Monitoring and Evaluation of the Long-Range Transmission of Air Pollutants in Europe) station located in Cubuk, Ankara were studied for the period between September 1994 and December 1996. The station is located in a rural area about 50 km north of Ankara and is considered as a background station for air pollution. The rainwater samples collected were analyzed for pH, major ions concentrations and conductivity. Seasonal variations for some major ions are pronounced. Generally, maximum concentrations appeared in winter or autumn, and minimum concentrations in spring or summer seasons. The average pH of rainwater samples is around 6.3 due to neutralization. Only about 4% of the rain samples had a pH below 5.0 and about 15% of the total rainwater samples had a pH below 5.6. This reflects strong inputs of alkaline species to rainwater samples in this location. The average pH of the samples higher than 5.6 observed in rural area of Ankara is due to a high loading of calcium ions in the form of CaCO 3 because of the alkaline nature of the soil. There is a strong relationship between pHs and other ions in summer. However, in winter, a weak relationship is found between SO 4 2− , NO 3 − , Na + and Mg 2+ . On the other hand, relationships between the conductivity and SO 4 2− concentration are stronger in summer than in winter. The low concentrations of H + found in rainwater samples from Cubuk suggests that an important portion of H 2 SO 4 and HNO 3 have been neutralized by alkaline particles in the atmosphere. Weak correlations are found between the hydrogen ions and SO 4 2− or NO 3 − ions for all seasons because of neutralization of these ions with alkaline particles. The dust-rich local and surrounding limestone environment might have caused the high concentration of Ca 2+ in Cubuk area. The relatively high concentration of NH 4 + observed at Cubuk is suspected to be due to surrounding agricultural activity. This agricultural activity has been found to be effective not only in spring, but also in autumn and winter to cause neutralization of the rainwater.

Cleaner energy production with integrated gasification combined cycle systems and use of metal oxide sorbents for H2S cleanup from coal gas

World primary energy demand increases with increases in population and economic development. Within the last 25 years, total energy consumption has almost doubled. In order to meet this demand, research into new sources of energy as well as improving the efficiency of energy production technologies is being carried out. In both cases, the production of clean energy is very important because of environmental concerns and regulations. Integrated gasification combined cycle (IGCC) technology seems to be one of the most promising technologies for production of energy by using fossil fuels, especially coal. Hot gas desulfurization is a crucial issue in the development of the IGCC system. This paper reviews the importance of clean energy production, the IGCC technology and focuses on the development of several metal oxide-based sorbents used for desulfurization of the hot coal gas in the IGCC system.

Effect of freeboard extension on co-combustion of coal and olive cake in a fluidized bed combustor

In this study, flue gas emissions and combustion efficiencies during combustion and co-combustion of olive cake and coal were investigated in a bubbling fluidized bed. Temperature distributions along the combustion column and flue gas concentrations of O(2), CO, SO(2) and NO(x) were measured during combustion experiments. Two sets of experiments were performed to examine the effect of fuel composition, excess air ratio and freeboard extension on flue gas emissions and combustion efficiency. The results of the experiments showed that coal combustion occurs at lower parts of the combustion column whereas olive cake combustion takes place more in the freeboard region. As olive cake percentage in the fuel mixture increased, CO emissions increased, SO(2) and NO(x) emissions decreased. Additionally, flue gas emissions could be lowered with the freeboard extension while burning biomass or biomass/coal mixtures. Noticeable decrease in CO emissions and slight increase in combustion efficiencies were observed with a column height of 1900 mm instead of 900 mm.

An investigation on gas mixing in a fluidized bed

Abstract The radial dispersion of gas in a fluidized bed of 10 cm diameter, charged with resin beads, was investigated using a new strip staining technique with bromine as tracer. Paper strips containing KI, which were placed in tubes with capillary tips, provided stains which had previously been calibrated against air—bromine mixtures flowing under similar conditions in the bed. A similar trend of the concentration profiles related to the two-dimensional diffusion model was obtained.

Desulfurization of hot coal gas

World Energy Resources, Their Use and the Environment.- Overview of Clean Coal Gas Technologies and Current Status of the Air Blown Gasification Cycle.- Assessment of Coal Gasification Processes - Relevance to Sorbent Development.- Effects of Process Conditions on Thermodynamics of Gasification.- Application of IGCC Technology to Power Generation.- Hot Gas Cleaning - An Overview.- Survey of Desulfurization Processes for Coal Gas.- Removal of H2S from Coal Gas: Effect of Various Parameters on the Desulfurization Efficiency.- Hot Gas Cleaning, Sulfiding Mechanisms in Absorption of H2S by Solids.- Kinetics of Sulfidation Reactions Between H2S and Bulk Oxide Sorbents.- Performance Analysis of ZnO-Based Sorbents in Removal of H2S From Fuel Gas.- Performance of Manganese-Based Sorbents in High Temperature Coal Gas Desulfurization.- In-situ Desulfurization of Coal Gas with CaO-Based Sorbents.- Stabilization and Regeneration of Spent Sorbents.- Mixed Metal Oxide Sorbents.- Development of Supported Sorbents for H2S Removal from Fuel Gas.- Regeneration of Sulfided Sorbents and Direct Production of Elemental Sulfur.- Elemental Sulfur Recovery from SO2-Rich Streams.- Experience of Regenerable Sulfur Sorbents in Real Fuel Gas Systems.-

Co-firing of pine chips with Turkish lignites in 750kWth circulating fluidized bed combustion system

Two Turkish lignites which have different sulfur levels (2-2.9% dry) and ash levels (17-25% dry) were combusted with a Turkish forest red pine chips in a 750kW-thermal capacity circulating fluidized bed combustor (CFBC) system. The combustion temperature was held at 850±50°C. Flue gas emissions were measured by Gasmet DX-4000 flue gas analyzer. Two lignites were combusted alone, and then limestone was added to lignites to reduce SO2 emissions. Ca/S=3 was used. 30% percent of red pine chips were added to the lignites for co-firing experiments without limestone in order to see the biomass effects. The results showed that with limestone addition SO2 concentration was reduced below the limit values for all lignites. CO emissions are high at low excess air ratios, gets lower as the excess air ratio increases. During co-firing experiments the temperature in the freeboard was 100-150°C higher as compared to coal combustion experiments.

Security of Industrial Water Supply and Management

Water Integration for Recycling and Recovery in Process Industry J.J. Klemes et al.- Water Networks - Theory and Practice P. Glavic , M. Bogataj.- Water Conservation in the Chemical Process Industry - Mass Integration Approach P. Raskovich.- Technological Advances in Industrial Water Safety and Security A. Vaseashta.- Water Footprinting: A Tool to Develop and Manage Water Stewardship for Business A.J. Wyness.- Color Removal with Natural Materials for Reuse of Wastewater in Textile Industry A. Atimtay.- Reuse of biologically treated process water - Industrial Water Management in the Paper and Sugar Industry O.Nowak, P. Enderle.- Water Consumption in Paper Industry - Reduction Capabilities and the Consequences K. Olejnik.- Wastewater Reuse in Textile Industry F.G. Babuna.- Water Reuse Strategies: Iron and Steel Industry Case Study U. Yetis ,V. Cagin.- Environmental Friendly Technologies For Wastewater Treatment: Biosorption of Heavy Metals Using Low Cost Materials and Solar Photocatalysis V. Vilar.- Closing Water Cycles in Industry: Theory and Implementation J.K. Staniskis.- An Energy Saving Process for the Reactivation of Activated Carbon Saturated with Organic Contaminants R.A. Sierka.- Industrial Wastewater Treatment in Egypt: Difficulties and Proposed Solutions D.S. El Monayeri et al.- Industrial Wastewater Reuse Applications in Romania L.D. Gatalatchi.- Opportunities and Experience Implementing the Recycling Methods for Industrial Water Supply in Bulgaria P. Stoychev.- Subject Index.

Comparison of fuel value and combustion characteristics of two different RDF samples.

Generation of Municipal Solid Waste (MSW) tends to increase with the growing population and economic development of the society; therefore, establishing environmentally sustainable waste management strategies is crucial. In this sense, waste to energy strategies have come into prominence since they increase the resource efficiency and replace the fossil fuels with renewable energy sources by enabling material and energy recovery instead of landfill disposal of the wastes. Refuse Derived Fuel (RDF), which is an alternative fuel produced from energy-rich Municipal Solid Waste (MSW) materials diverted from landfills, is one of the waste to energy strategies gaining more and more attention. This study aims to investigate the thermal characteristics and co-combustion efficiency of two RDF samples in Turkey. Proximate, ultimate and thermogravimetric analyses (TGA) were conducted on these samples. Furthermore, elemental compositions of ash from RDF samples were determined by X-Ray Fluorescence (XRF) analysis. The RDF samples were combusted alone and co-combusted in mixtures with coal and petroleum coke in a lab scale reactor at certain percentages on energy basis (3%, 5%, 10%, 20% and 30%) where co-combustion processes and efficiencies were investigated. It was found that the calorific values of RDF samples on dry basis were close to that of coal and a little lower compared to petroleum coke used in this study. Furthermore, the analysis indicated that when RDF in the mixture was higher than 10%, the CO concentration in the flue gas increased and so the combustion efficiency decreased; furthermore, the combustion characteristics changed from char combustion to volatile combustion. However, RDF addition to the fuel mixtures decreased the SO2 emission and did not change the NOx profiles. Also, XRF analysis showed that the slagging and fouling potential of RDF combustion was a function of RDF portion in fuel blend. When the RDF was combusted alone, the slagging and fouling indices of its ash were found to be higher than the limit values producing slagging and fouling.

Investigation of Combustion Kinetics of Five Waste Wood Samples with Thermogravimetric Analysis

In the present study, combustion mechanisms, thermal kinetics, and phases of combustion were investigated for untreated pine and treated MDF, plywood and particleboard samples. Waste wood samples were combusted in air at 10, 20 and 30°C/min heating rates in TGA. As a result of TG analysis, thermal decomposition of treated samples was observed at lower temperatures as compared to the untreated pine sample because of the catalyzing effects of the chemicals in the samples. Therefore, there were less flammable products, lower weight losses in the main oxidation region, decrease in the max. weight loss temperatures and formation of more char for treated samples as compared to untreated pine sample. In other words, chemicals used during production of these samples lead to decrease in the combustibility of the treated samples. Thermal kinetic constants for the samples were calculated by using Coats Redfern and Broido Methods. In order to find out the mechanisms responsible for the oxidation of the waste wood samples, six solid state mechanisms of Coats Redfern Method were tested.