Abtin Ataei

Production of hydrogen and syngas via pyrolysis of bagasse in a dual bed reactor

Abstract Pyrolysis of bagasse followed by thermal cracking of tar was carried out at atmospheric pressure using a dual bed reactor. The first bed was used for the pyrolysis and the second bed was used for thermal cracking of tar. Iron fillings were used as the packed bed material in the second bed. The effects of reaction time (20 to 40 min), reactor temperature (600 to 900 °C) and packed bed height (40–100 mm) on the product (char, tar and gas) yield and gas (H 2 , CO, CO 2 , CH 4 , C n H m ) composition were studied. Over the ranges of the experimental conditions used, the operating conditions were optimized for pyrolysis temperature around 850 °C, a reaction time of 30 min and packed bed height of 100 mm, thus we could obtain a gas richer in hydrogen and carbon monoxide and poorer in carbon dioxide and hydrocarbons. It was observed that compared with single bed process, dual bed process increased the gas yield from 0.397 to 0.750 m 3 /kg and decreased the tar yield from 0.445 to 0.268 g/g while the heating value of the product gas remained almost constant (10–11 MJ/m 3 ).

Comparison of sequential and simultaneous design and optimization in low-temperature liquefaction and gas separation processes

Abstract A great deal of attention has been paid to design and optimization of low-temperature liquefaction and gas separation problems over the past years, due to their difficult nature. In this paper, two approaches featuring sequential and simultaneous methods for selection and arrangement of sub-ambient separation systems and their associated refrigeration cycles are compared. The effect of ignoring heat integration within the separation system and between the separation and refrigeration systems is addressed as well as fixing the sequence order of separation. The optimization is carried out using two famous stochastic search methods i.e. Genetic Algorithm (GA) and Simulated Annealing (SA). Three case studies are examined to illustrate the significant differences between optimization results. Also, the design optimality is re-checked with respect to usage of different refrigerants and the resulting structure is verified by application of a comprehensive exergy analysis.

Optimum design of an off-grid hybrid renewable energy system for an office building

Although much attention has been paid to the utilization of hybrid renewable energy systems for either commercial buildings or residential ones, rare studies dealt with the application of off-grid hybrid renewable energy systems for commercial buildings. This paper presents a comprehensive study on the techno-economic performance of a stand-alone hybrid photovoltaic (PV)-wind-battery system for an office building located in Tehran, Iran. The Hybrid Optimization Model for Electric Renewables model was used to investigate the optimal design options and the techno-economic viability of the hybrid renewable energy system installed in that building. The proposed hybrid system based on renewable resources was designed to electrify the restrooms of the building. An optimal system configuration was chosen based on the total net present cost (NPC) and cost of energy (COE). The simulation results demonstrated that the optimum structure for the hybrid system for the primary load demand of 5.6 kW h per day, consists ...

Application of exergy analysis for quantification and optimisation of the environmental performance in wastewater treatment plants

This paper presented a new approach to estimate the degradation of environmental resources in a Wastewater Treatment Plant (WWTP) using exergy analysis. In first part, a method was described to calculate various quantities of the wastewater exergy. Furthermore, units were analysed to determine the most defective unit. In second part, a case study was analysed based on the environmental exergy concepts. Two environmental indexes include Environmental Exergy Efficiency (EEE) and the Total Pollution Rate (TPR) were considered for quantification of environmental impacts. In third part, the primary clarifier was determined as the most defective unit. At least, the optimised network was presented to performance improvement and environmental impacts reducing. EEE and TPR indexes were changed from 6.14 and 0.14 to 1.79 and 0.36, respectively. In addition, the results of this paper showed that exergy analysis can be used as a tool for quantification and optimisation of WWTP.

Performance analysis of a co-gasifier for organic waste in agriculture

BackgroundAgricultural waste has been proposed as an alternative energy resource to meet fossil fuel crisis, green house emission, and other environmental impacts worldwide. In Iran, rice husk and bagasse are main resources of biomass which can be used to produce syngas. This paper deals with a simplified model of combined gasification of coal and biomass processes considering chemical equilibrium.ResultsIt should be noticed that the CO2 which is produced from agricultural waste gasification is natural because the biomass absorbs CO2 from nature and gives it back after gasifying; however, mixing agricultural waste with coal leads to enrich syngas quality and gasifier efficiency.ConclusionsIn this regard, an advanced coding was developed to simulate the thermodynamics of the co-gasifier and to find the produced syngas composition. The effects of moisture content, steam-to-biomass ratio, and gasifier temperature are then discussed on the system performance. Additionally, co-gasification of rice husk/coal was compared with co-gasification of bagasse/coal. The results indicated that adding coal to biomass increases lower heating value of syngas from 4,694 kJ/Nm3 to 5,321 kJ/Nm3 and gasifier efficiency from 71.29% to 77.85%.

Comparative analysis of three numerical methods for estimating the onshore wind power in a coastal area

ABSTRACT Although there are many studies concerning the estimation of wind potential in different locations of Iran, an adequate evaluation of wind power for onshore locations of this country has not been investigated yet. The purpose of this research is to evaluate the potential of onshore wind in the south of Iran along the Gulf of Oman by comparing three Weibull numerical methods. In the first step, it became clear that the maximum likelihood method (MLM) compared to other methods represented the actual wind data with the lowest error rate and therefore it was selected as an accurate statistical distribution to model the wind speed of the investigated location. Using the MLM, the estimation of wind speed characteristics as well as the techno-economic evaluation of different wind turbines has been investigated. It was concluded that both technically and economically the studied area does not have sufficient wind power for the development of large-scale or grid-connected wind turbines. However, it may have enough power for non-grid-connected mechanical applications, such as wind generators for water pumping. Therefore, in the last part of this paper, an investigation of water pumping potential of the studied site by using adequate and modern wind turbines with lower start-up wind speed was recommended for future studies. Furthermore, it was suggested that the current methodology used in this research could be employed and extended in future studies to evaluate the wind potential of all onshore locations of Iran including onshore locations along the Persian Gulf and Caspian Sea.

Comparison of refrigerated warehouse energy demand with R-717 and R-507 using eQUEST model

ABSTRACT Natural refrigerant ammonia R-717 and synthetic azeotropic refrigerant R-507 (a blend containing 50% R-143a and 5% R-125 by weight) are used in a wide range of refrigeration systems especially in low-temperature applications. R-717 and R-507 are ozone friendly refrigerants, which have no Ozone Depletion Potential (ODP). Global Warming Potential (GWP) of R-717 and R-507 is equal to zero and 3300, respectively. The high amount of R-507 GWP demonstrates its negative effect on the Earth’s climate change. In this study, a refrigerated warehouse located in Cincinnati, Ohio was modeled and the total energy demand and Coefficient of Performance (COP) was evaluated by eQUEST using two scenarios. The R-717 and R-507 were used as refrigerant in the first and second scenarios, respectively. The results showed that using R-717 in the refrigeration system leads to a 15% energy saving and a higher COP compared to R-507 in all working conditions. The only exception is that at an evaporating temperature below −35°C which COP values of both refrigerants are approximately equal.