Efficiency Of Combined Process Research Articles

Development of an Integrated Structure for the Tri-Generation of Power, Liquid Carbon Dioxide, and Medium Pressure Steam Using a Molten Carbonate Fuel Cell, a Dual Pressure Linde-Hampson Liquefaction Plant, and a Heat Recovery Steam Generator

Due to the increase in energy consumption and energy prices, the reduction in fossil fuel resources, and increasing concerns about global warming and environmental issues, it is necessary to develop more efficient energy conversion systems with low environmental impacts. Utilizing fuel cells in the combined process is a method of refrigeration and electricity simultaneous production with a high efficiency and low pollution. In this study, a combined process for the tri-generation of electricity, medium pressure steam, and liquid carbon dioxide by utilizing a molten carbonate fuel cell, a dual pressure Linde-Hampson liquefaction plant and a heat recovery steam generator is developed. This combined process produces 65.53 MW of electricity, 27.8 kg/s of medium pressure steam, and 142.9 kg/s of liquid carbon dioxide. One of the methods of long-term energy storage involves the use of a carbon dioxide liquefaction system. Some of the generated electricity is used in industrial and residential areas and the rest is used for storage as liquid carbon dioxide. Liquid carbon dioxide can be used for peak shavings in buildings. The waste heat from the Linde-Hampson liquefaction plant is used to produce the fuel cell inlet steam. Moreover, the exhaust heat of the fuel cell and gas turbine would be used to produce the medium pressure steam. The total efficiency of this combined process and the coefficient of performance of the refrigeration plant are 82.21% and 1.866, respectively. The exergy analysis of this combined process reveals that the exergy efficiency and the total exergy destruction are 73.18% and 102.7 MW, respectively. The highest rate of exergy destruction in the hybrid process equipment belongs to the fuel cell (37.72%), the HX6 heat exchanger (8.036%), and the HX7 heat exchanger (6.578%). The results of the sensitivity analysis show that an increase in the exit pressure of the V1 valve by 13.33% would result in an increase in the refrigeration energy by 2.151% and a reduction in the refrigeration cycle performance by 9.654%. Moreover, by increasing the inlet fuel to the fuel cell, the thermal efficiency of the whole combined process rises by 18.09%, and the whole exergy efficiency declines by 12.95%.

Combined aluminium sulfate/hydroxide process for fluoride removal from drinking water

In this study, aluminium hydro(oxide), AO was prepared from locally available aluminium sulfate, and used for fluoride removal from water by combining with Nalgonda Technique. The fluoride removal performance of the combined process was investigated as a function of contact time, proportion of alum-lime/AO dose, initial fluoride concentration and solution pH in series of batch experiments. The rate of fluoride removal was investigated using conventional kinetic models. The fluoride removal efficiency of the combined process was also tested for real water sample from selected community water supply system in the Rift Valley Region of Ethiopia. The removal of fluoride was rapid in the first 15 min. The combined process efficiency was about 93% with an optimum combined alum/AO dose (80 mg alum/mg F, 5 mg AO/mg F and lime = 35% of alum) using initial fluoride concentration of 15 mg/L. The optimum solution pH for fluoride removal was in the range of 5-9, which is suitable for practical application in the Ethiopia Rift Valley Region. Kinetic studies showed that the rate of fluoride removal by alum/AO can be well described by a pseudo-second-order rate equation with an average rate constant of 0.096 g/min . mg. The optimum dose required to attain 85-93% fluoride removal efficiency from real water sample was 90 mg alum/mg F, 5 mg AO/mg F, and 15% lime. Hence, the combined defluoridation process has higher fluoride removal efficiency than the Nalgonda Technique with an additional advantage of minimizing chemical dose. The reported removal efficiency of Nalgonda Technique is 70% at alum dose of 150-170 mg alum/mg F. Besides, sludge production is also minimized. Therefore, this process is highly efficient and could be applied in areas where the fluoride concentration is higher than 10 mg/L, both at household and community level. KEY WORDS : Nalgonda Technique, Aluminium sulfate, Aluminium hydroxide, Fluoride, Drinking water Bull. Chem. Soc. Ethiop. 2016 , 30(3), 391-401 DOI: http://dx.doi.org/10.4314/bcse.v30i3.7

Optimization of process factors for the efficient generation of biogas from raw vegetable wastes under the direct influence of plastic materials using Taguchi methodology

In this investigation, the combined process efficiency with respect to biogas generation was evaluated by Taguchi robust design using raw vegetable wastes (RVW) and waste plastics (WP) as the key components. The signal-to-noise (S/N) ratio was used to estimate the main effects, interaction effects, and optimal levels of the process factors. Among the various experimental combinations, statistical analysis of the optimized result showed that enhanced biogas production could be achieved with the plastic content (15%), height to diameter (h/D) ratio (30), water content (125 ml), and digestion period (18 week). The Taguchi methodology predicted a maximum biogas (24.83 m3/ton of RVW) could be generated with those selected process parameters under optimized condition. The experimental data showed that enhanced biogas production (24.16 m3/ton of RVW) was found with the optimized conditions.

Efficiency of combined process of ozone and bio-filtration in the treatment of secondary effluent

The present work was aimed at studying the efficiency of the combined process of biofiltration with ozonation to improve the quality of secondary effluent. The secondary effluent from the Dinapur Sewage Treatment Plant Varanasi, India was used in this work. The process of biofiltration with the plant species of Eichornia crassipes and Lemna minor, at a flow rate of 262 ml min −1 and plant density of 30 mg L −1 for 48 h, in combination with the process of ozonation with ozone dose of 10 mg L −1 and contact time of 5 min was applied. Results revealed that combined process was statistically most suitable for the highest degradation of physico-chemical and microbial parameters with improving BDOC value. The biofiltration process is able to remove highest percentage of toxic heavy metals from the secondary effluent without production of toxicity. This technique is highly recommendable for tropical wastewater where sewage is mixed with industrial effluents.

Canteen based composite food waste as potential anodic fuel for bioelectricity generation in single chambered microbial fuel cell (MFC): Bio-electrochemical evaluation under increasing substrate loading condition

Canteen based composite food waste, which is rich in organic constituents was evaluated as anodic fuel (substrate) in single chambered microbial fuel cell (MFC; mediator less; non-catalyzed graphite electrodes; open-air cathode) to harness electrical energy via anaerobic treatment. The performance of MFC was evaluated with anaerobic consortia as anodic biocatalyst under various increasing organic loading rates (OLR1, 1.01 kg COD/m 3-day; OLR2, 1.74 kg COD/m 3-day; OLR3, 2.61 kg COD/m 3-day). The experimental results illustrated the feasibility of bioelectricity generation from food waste along with treatment but depend on the applied organic load. The maximum power output was observed at OLR2 (295 mV; 390 mA/m 2), followed by OLR3 (250 mV; 311 mA/m 2) and OLR1 (188 mV; 211 mA/m 2). The variation in substrate degradation has also showed a relation with organic load applied (OLR1, 44.28% (0.47 kg COD/m 3-day); OLR2, 64.83% (1.13 kg COD/m 3-day); OLR3, 46.28% (1.39 kg COD/m 3-day)). The increase in loading from OLR1 to OLR2, the catalytic ability of biocatalyst increased from 7.5 mA (24 h) to 11.22 mA (24 h) along with the increase in power generation from 39.38 mW/m 2 to 107.89 mW/m 2. At the higher OLR (OLR3), the bioelectrocatalytic current decreased to 5.3 mA (24 h) along with decrement in power to 78.92 mW/m 2. The optimum organic load (OLR2) showed maximal catalytic activity and power output. Fuel cell behavior with respect to polarization, anode potential and bio-electrochemical behavior supported the higher performance of MFC at OLR2. Specific power yield was also observed to be higher at OLR2 (0.320 W/kg COD R) indicating the combined process efficiency. Volatile fatty acids generation and pH profiles also correlated well with the observed results.

Methodology of control of structure formation for development of hardening processes

Various processes of hardening heat treatment are considered, and a methodology for choosing the method for attaining the optimum hardening effect for the chosen material is presented. The efficiency of combined processes for ensuring high hardening parameters is demonstrated.

Recent Achievements in Combination of Ultrasonolysis and Other Advanced Oxidation Processes for Wastewater Treatment

A review of recent advancements in the combination of ultrasonolysis with other advanced oxidation processes is studied. This study is based on the recent achievements and developments in the field of water and wastewater treatment using ultrasonic irradiation by means of acoustic cavitation with other advanced oxidation technologies. The most important parameter in combined methods is the synergetic effect which is a variable relative to the type of contaminant(s) and other physicochemical properties. The synergetic effect has the key role in process intensification so that a higher synergetic effect provides a higher intensified process efficiency. Results showed that sonolysis is a method that can increase the synergetic percentage in lowering fixed and even operating cost of the wastewater remediation. The combination of photolysis, photocatalysis, Fenton, photo-Fenton, and ozonation processes with ultrasonolysis results in hydroxyl radical production and therefore, the degradation of the organic chemicals. The effect of various parameters on the efficiency of combined processes is investigated in the present study. The combined process performance and the synergetic effect depend on the operating conditions and wastewater characteristics. The synergetic effect can enhance the degradation of organic compounds up to 400%. For example, it has been proven that the sonophotocatalytic process shows over 80% improvement with respect to the photocatalysis alone.

Acetate and butyrate as substrates for hydrogen production through photo-fermentation: Process optimization and combined performance evaluation☆

Abstract Organic acids viz., acetate and butyrate were evaluated as primary substrates for the production of biohydrogen (H 2 ) through photo-fermentation process using mixed culture at mesophilic temperature (34 °C). Experiments were performed by varying parameters like operating pH, presence/absence of initiator substrate (glucose) and vitamin solution, type of nitrogen source (mono sodium salt of glutamic acid and amino glutamic acid) and gas (nitrogen/argon) used to create anaerobic microenvironment. Experimental data showed the feasibility of H 2 production along with substrate degradation utilizing organic acids as metabolic substrate but was found to be dependent on the process parameters evaluated. Maximum specific H 2 production and substrate degradation were observed with acetic acid [3.51 mol/Kg COD R -day; 1.22 Kg COD R /m 3 -day (92.96%)] compared to butyric acid [3.33 mol/Kg COD R -day; 1.19 Kg COD R /m 3 -day (88%)]. Higher H 2 yield was observed under acidophilic microenvironment in the presence of glucose (co-substrate), mono sodium salt of glutamic acid (nitrogen source) and vitamins. Argon induced microenvironment was observed to be effective compared to nitrogen induced microenvironment. Combined process efficiency viz., H 2 production and substrate degradation was evaluated employing data enveloping analysis (DEA) methodology based on the relative efficiency. Integration of dark fermentation with photo-fermentation appears to be an economically viable route for sustainable biohydrogen production if wastewater is used as substrate.

Acidogenic fermentation of vegetable based market waste to harness biohydrogen with simultaneous stabilization

Vegetable based market waste was evaluated as a fermentable substrate for hydrogen (H 2) production with simultaneous stabilization by dark-fermentation process using selectively enriched acidogenic mixed consortia under acidophilic microenvironment. Experiments were performed at different substrate/organic loading conditions in concurrence with two types of feed compositions (with and without pulp). Study depicted the feasibility of H 2 production from vegetable waste stabilization process. H 2 production was found to be dependent on the concentration of the substrate and composition. Higher H 2 production and substrate degradation were observed in experiments performed without pulp (23.96 mmol/day (30.0 kg COD/m 3); 13.96 mol/kg COD R (4.8 kg COD/m 3)) than with pulp (22.46 mmol/day (32.0 kg COD/m 3); 12.24 mol/kg COD R (4.4 kg COD/m 3)). Generation of higher concentrations of acetic acid and butyric acid was observed in experiments performed without pulp. Data enveloping analysis (DEA) was employed to study the combined process efficiency of system by integrating H 2 production and substrate degradation.

Optimization and evaluation of fermentative hydrogen production and wastewater treatment processes using data enveloping analysis (DEA) and Taguchi design of experimental (DOE) methodology

The combined process efficiency with respect to fermentative hydrogen (H 2) production and wastewater treatment was evaluated in a series of batch experiments to enumerate the role of selected factors viz., origin of inoculum, pre-treatment, inlet pH and feed composition under anaerobic microenvironment using mixed culture. H 2 production and substrate degradation were found to depend significantly on the selected factors with individual conditions to achieve effective process performance. Significantly diverse operational conditions were observed for both H 2 production and substrate degradation with respect to process efficiency. However, while dealing with H 2 production in association with wastewater treatment, both the parameters are important and balancing the conditions for combined effective performance is critical. Data enveloping analysis (DEA) was applied to evaluate the combined system performance with respect to the two output parameters (H 2 production and substrate degradation) based on relative efficiency. Among various experimental combinations studied, those with untreated anaerobic mixed inoculum under acidophilic conditions (inlet pH 5.5) using simple wastewater as fermentative substrate illustrated combined process efficiency with respect to H 2 production (1.919 m mol H 2/day; 0.52 mol H 2/kg COD R-day) and substrate degradation (substrate degradation rate, 4.56 kg COD/m 3-day). DEA methodology provide the relative efficiency of the system by integrating two output parameters. Further, design of experimental methodology (DOE) by Taguchi approach was applied to enumerate the role of selected factors on the H 2 production and substrate degradation with the final aim of optimizing the process. By adapting the derived optimum conditions, the performance with respect to H 2 production and substrate degradation could be enhanced by three fold.

Application of Flotation for the Separation of Metal‐Loaded Resins#

The separation of two typical Lewatit‐type ion exchange resins (TP208 and TP260) was studied by the application of flotation, following their preliminary use for ion exchange of zinc, a common heavy metal found in many wastewater streams. The major examined parameters were the specific type of resin and the respective ion exchange capacity, the required resin concentration for the efficient removal of metal, the influence of wetting on both processes (i.e., ion exchange and flotation), the effect of pH value on the removal of metal and on the regeneration of resin, the type and concentration of used surfactant (primary amine or quaternary ammonium were examined), as well as the effect of frother (ethanol) on flotation efficiency. The regeneration of resins was studied, with respect to the desorption of metal and to the elution of surfactant. The efficiency of combined process, which includes the removal of Zn(II) by ion exchange and the application of flotation for the subsequent solid/liquid separation of metal‐loaded resin, showed that almost 100% of zinc was removed and more than 95% of used resin was recovered by flotation in a single stage. The operation was also examined during multiple cycles, i.e., following regeneration of resin; the high efficiency of both processes remained rather constant. Many thanks are due to the European Union – Energy, Environment and Sustainable Development (5th Framework programme) for funding the METASEP research project (for more information see reference 28) with contract no EVK1‐CT‐2000‐00083 and to the coordinator Dr. V. Mavrov (Inst. Envir. Compatible Process Tech., Univ. Saarland). Also, to Ms. S. Pataroudi, chemist, for experimental collaboration.