www.as‐se.org/ijpres International Journal of Power and Renewable Energy Systems Volume 1, 2014
Energy Global Challenges for Future: Combined study of Hydrogen Production and Utilization from Industrial Wastewater Omprakash Sahu Department of Chemical Engineering, KIOT, Wollo University, Kombolcha (SW) Ethiopia *Correspondence Email: ops0121@gmail.com, Tel: +251933520653 Received 26 March 2014; Accepted 24 June 2014; Published 11 July 2014 © 2014 American Society of Science and Engineering Abstract: Hydrogen is not found in free‐state in nature. It is normally combined with other elements such as carbon, oxygen, sulfur, chlorine and so on. Hydrocarbons are a common resource, and steam reforming of hydrocarbons (methane) is a popular method of present day hydrogen production. However, producing hydrogen from hydrocarbons does not address the environmental concerns as the problem gets merely shifted from the automotive tailpipe to some remote location where hydrogen is produced. In order to have environment friendly hydrogen we must be able to produce it from renewable resources. Presently the studies focus on production of hydrogen with reduction of waste from the environment. Waste water generated from sugar industry was used for the production of hydrogen. The color 78% and COD 72% reductions with 55% of hydrogen was generated. The hydrogen supplied to alkaline fuel cell for generation of electricity. Keywords: Biomass; Current; Effluent; Fuel Cell; Hydrogen
Introduction Presently world facing two issues first one how to reduced the waste and second how increase the energy production. Energy resources such as coal, oil and natural gas are being consumed at an accelerated rate with fear of depletion in the next few decades. It is reported that some of the oil rich countries would fail to meet the world energy demand in the next few decades. There is also a concern about the environmental pollution caused by the use of fossil fuels. According to a recent study the world CO2 emissions from fossil sources have increased by 24.4% from 1990 to 2004 [1]. Apart from CO2, other contaminants such as CO, NOx, and Sox are released during the combustion of fossil fuels. These contaminants cause acid rains, deplete the stratospheric ozone layer and are also known to be carcinogenic. According to an EPA study, vehicles in the US account for 65% of total oil consumption and result in 78% CO, 45% NOX and 37% Volatile Organic Compound (VOC) emissions [2]. Among all the air pollutants emitted by the combustion of fossil fuels, CO2 alone accounts for 99% (by weight) of the total emissions [3. The average surface temperature of earth has increased by 0.6oC over the past two centuries [4]. If this trend continues it may eventually lead to higher sea levels and significant changes in global precipitation patterns. The trend in the transportation sector in industrialized countries is towards more vehicles, more freight transport by road and larger and heavier passenger vehicles. Furthermore, developing countries like China and India with large population and growing economies are expected to add to the rapid growth in vehicle usage for transportation applications [5]. This would further lead to large scale emissions which may drastically change the global weather patterns, thus affecting mankind and environment. The world energy demand has been steadily increasing over the last few decades. According to a recent study conducted by the US Department of Energy, the world energy demand is expected to increase to 722 quads (Quadrillion BTU) by 2030 from the present demand of 421 quads (2003) [6], a 71% increase largely due to growth in developing countries. According to the same study fossil fuels will continue to supply much of the increment in projected demands; however, depletion of fossil reserves is a matter of concern. Although oil would remain an important energy source, its share in total energy consumption would decrease from 38% in 2003 to 33% in 2030. This is largely in response to the higher world oil prices which would be driven by rapid depletion of oil reserves in many parts of the world. Among all sectors, transportation and industry continue to be the major oil consumers. Alternate fossil sources such as natural gas are also limited. According to a recent study conducted by British Petroleum, the
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International Journal of Power and Renewable Energy Systems Volume 1, 2014 www.as‐se.org/ijpres
Reserves to Production ratio (R/P) of natural gas in the US is less than 10 [7]. Hence, developing alternate energy carriers is necessary. In recent years, hydrogen has gained recognition as a potential substitute to fossil fuels. Hydrogen is an important raw material for chemical, petroleum and agro‐based industries [8]. The demand for hydrogen in the hydro treating and hydrocracking of crude petroleum is steadily increasing [9, 10]. Hydrogen is catalytically combined with various intermediate processing streams and is used in conjunction with catalytic cracking operations to convert heavy and unsaturated compounds to lighter and more stable compounds. Large quantities of hydrogen are used to purify gases such as argon that contain trace amounts of oxygen. This is done by catalytic combination of oxygen and hydrogen followed by removal of the resulting water. In the food and beverages industry, it is used for hydrogenation of unsaturated fatty acids in animal and vegetable oils, to produce solid fat and other food products [11]. Hydrogen is also used as a carrier gas in the manufacture of semi conducting layers in integrated circuits. The pharmaceutical industry uses hydrogen to make vitamins and other pharmaceutical products. Hydrogen is mixed with inert gases to obtain a reducing atmosphere which is required for many applications in the metallurgical industry such as heat treating steel and welding. It is often used in annealing stainless steel alloys, magnetic steel alloys, sintering and for copper brazing. It is also used as a reducing agent in the float glass manufacturing industry. As a fuel, hydrogen is considered to be very clean as it releases no carbon or sulfur emissions upon combustion. The energy contained in hydrogen on a mass basis (120 MJ/kg) is much higher than coal (35 MJ/kg), gasoline (47 MJ/kg) and natural gas (49.9 MJ/kg) [12]. However, on a volumetric basis hydrogen has lower energy density. Moreover chemical energy stored in hydrogen can be directly converted into electricity by a fuel cell. The conversion efficiency of a fuel cell is higher than conventional combustion engines, thereby making fuel cells attractive energy conversion devices (and hence hydrogen an attractive fuel) for transportation and stationary applications. Hydrogen has long been a fuel of choice for the jet propulsion and space industry [13]. NASA has been using liquid hydrogen to fuel the space shuttle’s main engine and hydrogen fuel cells provide onboard electric power. The space crew even drinks the water produced by the fuel cell’s chemical process. Many experts predict that hydrogen will eventually power tomorrow’s industries and thereby may replace coal, oil and natural gas [14]. However it will not happen until a strong framework of hydrogen production, storage, transport and delivery is developed. All the steps must be technically feasible and economically viable. So many methods are available for hydrogen production like combustion, pyrolysis, electrolysis, hydrolysis, biological etc. But they are not focus on reduction of waste. Second thing was production of energy, but involves in some side product. So some alternative was introduced for the production of hydrogen and minimization of pollution. In this regard’s an attempted has been made to treat the waste water with electrocoagulation and generate the power with fuel cell. The main object of the study is to treat the municipal waste water by electrocoagulation with hydrogen production and utilization of hydrogen for fuel cell. Material and Method: Material: The waste water was collected from sugar industry and preserved at 20oC. Method: Electrocoagulation: The aluminium cylindrical reactor with a height of 40 cm and diameter of 3.5 cm was used as cathode while the three pairs of iron rods (o.d. = 1.25cm, height:34 cm) were used as anode and placed in the centre of the reactor. Fuel Cell: The experiments were carried out in a 7cmx7cm stainless steel plate in which a special new designed electrolyte carrier plate (Silicon) is fitted with bolts. The cathode (5cmx5cm) and anode (5cmx5cm) is placed in front and back side of electrolyte carrier. Analytical: Parameters: The pH value, electrical conductivity (EC) and total dissolved solids (TDS) were measured by PHT‐027 ‐ water quality multiparameter monitor (Kelilong Electron). The colour was determined according to the 8025 APHA platinum‐cobalt standard method (adopted from Standard Methods for the Examination of Water and Wastewater) using the HACH DR890 colorimeter (Hach Company, Loveland, Colorado, USA). Hydrogen production: Cumulative hydrogen gas was calculated using the following equation: Vn= (QxXH2)+Vn‐1 (1) Where Vn is the volume of hydrogen gas at n hours; Q is the flow rate of total gas; XH2 is the concentration of
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hydrogen gas in total gas; Vn‐1 is the volume of hydrogen gas in total gas. The electrical energy supplied to the system was calculated using the following equation Ee=VIt (2) Where Ee is the electrical energy supplied by the DC power supply (J); V is the DC voltage applied; I is the current (A) and t (hour) is the duration of the DC voltage applied to the system. The amount of produced hydrogen gas was calculated using the following equation: PVH2= (m/M)RT (3) Where P denotes pressure in atm; VH2 denotes volume of the cumulative hydrogen calculated from equation (1); m denotes the mass of the cumulative hydrogen (g); M is the molar mass of hydrogen (2 g /mol); R is the gas constant (0.082 L atm. mol‐1 K‐1), T is denoting the room temperature (298 K). Result and Discussion: Reduction of Pollution Parameter: To determine the effect of time on pollution reduction parameter was carried out at 1 Volt, 10mm electrode distance and 6.5 pH initial conditions. The result represent in Fig. 1. It was found that maximum 78% of color and 72% of COD reduction at 240 min. respectively. The reduction parameters are increase with increase in time. Initially when time is 30, 60, 90, 120, 150, 180, and 210 min. the color 12, 20, 28, 37, 45, 56, 64% and COD 10, 16, 25, 33, 41, 52, 60 was found. This might be attributed to the fact that large amounts of metal ions were generated at long electrolysis times which can react with the dissolved oxygen in the wastewater. This leads to lowering the amount of oxygen and increase the hydrogen in the treated wastewater [15].
FIG.1: EFFECT OF TREATMENT TIME ON COLOR AND COD REDUCTION
Hydrogen Production: To determine the hydrogen production treated waste water and normal water was used which shown in Fig. 2. The reactor was designed to make pretreatment of sugar industry waste water in a closed container specially equipped with a gas collection system. In reactor 2 ampere current and 4 voltage at 10mm electrode was fixed. The pH WW after treatment was found 6.9 at 120 min. this might be due to formation of the Al (OH)3XH2O at anode of reactor in aluminium electrode. Which is a very reactive agent for flocculation/coagulation of and production of hydrogen. The normal water was taken at pH 7.1. The maximum 55% of hydrogen gas was found from waste water and 30% with normal water. The production of hydrogen was increase with increase in treatment time. When time was 30, 60, 90, 120, 150, 180 the hydrogen production from waste water 8, 15, 21, 27, 36, 48% and from normal water 2, 7, 10, 13, 16, 22 was found after that it became constant [16].
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International Journal of Power and Renewable Energy Systems Volume 1, 2014 www.as‐se.org/ijpres
FIG. 2: HYDROGEN PRODUCTION FROM TREATED WATER AND NORMAL WITH RESPECT TO TIME
Efficiency of Fuel Cell To determine the effect of hydrogen on fuel cell was carried out at 3mole electrolyte concentration and 45oC temperature. The current voltage result of alkaline fuel cell shown in Fig. 3. at four different fuel concentrations. The CVs shows that the peak current decreases with the increase in hydrogen concentration. However the current density increases with the increase in hydrogen concentration form 15% to 25%. And on further increase in concentration of hydrogen to 48% the current density increases slightly. In this case initial increase in current density may be because of the increase in hydrogen concentration. But the availability of OH ion at catalyst site decrease with the further increase in hydrogen concentration .As a result the hydrogen oxidation reaction suffer due to lesser availability of adsorbed OH‐ on the catalyst sites. Consequently the current density at higher ethanol concentration decrease [17].
FIG. 3: CURRENT DENSITY AND CELL VOLTAGE CHARACTERISTIC OF ALKALINE FUEL CELL
Conclusion Sugar Industry effluent can be treated by using environment friendly electrocoagulation and hydrogen gas can be
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obtained as revenue to compensate the treatment cost of SIWW. From the result it was found that by electrocoagulation method 78% of color reduction and 72% of COD can be attempt. The hydrogen production was 55% at 210 min of the treatment. The alkaline fuel cell shows 16 Am‐2 and 1.1 voltages when hydrogen was feed in 45%. EC of SIWW can be performed by using small area as compared to the conventional aerobic/anaerobic pond system. Hydrogen gas was also found helpful to remove the suspended solids towards surface. This study is presenting an approach towards environment friendly treatment of POME and hydrogen production as an alternative energy. REFERENCE:
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