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Prof.Dr. lgi KAPDAN Dokuz Eyll University, Department of Environmental Engineering. Slide 2 Clean gas no CO 2 emmision Electricity can be produced by using Fuel Cell High Energy yield of 122 kj/g which is 2.75 times greater than hydrocarbon fuels So it is energy carrier of the future Slide 3 It is a widely used feed stock for the production Production of electronic devices Processing of steel Desurfilization of gasoline Methanol Hydrogenation of edible oils Plastics manufacturing Crude oil refining into petroleum Making polysilicone for wafer manufacture Ammonia-based fertilizers production Pharmaceutical production, etc. Slide 4 Growth rate of hydrogen need is 10% annually The contribution of hydrogen to total energy market will be 8-10% by year 2025 Hydrogen trasport system will be available by the year 2040 in USA Slide 5 It does not occur in nature as the fuel H 2. Rather, it occurs in chemical compounds like water or hydrocarbons that must be chemically transformed to yield H 2. It must be produced from a natural resource. Slide 6 Physical and Chemical Methods Steam Reforming of Methane ( SRM) Steam reforming of hydrocarbons ( SRH) Non catalitic partial oxidation of hydrocarbons (POX) Autothermal reforming Electrolyisis of Water Biological Methods Slide 7 >> 4 H2 + CO2). It is a relatively efficient process, and can be made still more efficient with harvest of the waste heat (commonly referred to as cogeneration) However, it produces moderate emissions of carbon dioxide which has got green house effect!!"> Hydrogen can be extracted or "reformed" from natural gas. A two-step process at temperatures reaching 1100C in the presence of a catalyst makes four parts hydrogen from one part methane and two parts water (CH4 + 2 H2O >>> 4 H2 + CO2). It is a relatively efficient process, and can be made still more efficient with harvest of the waste heat (commonly referred to as cogeneration) However, it produces moderate emissions of carbon dioxide which has got green house effect!! Slide 8 Hydrogen can be extracted from hydrogen-rich biomass sources like wood chips and agricultural waste. When heated in a controlled atmosphere, biomass is converted to synthesis gas, carbon monoxide (CO), carbon dioxide (CO 2 ), hydrogen (H 2 ). Slide 9 Water electrolysis involves passing an electric current through H 2 O to separate it into hydrogen (H 2 ) and oxygen (O 2 ). Electrolysis produces extremely pure hydrogen, which is necessary for some types of fuel cells. But a significant amount of electricity is required to produce a usable amount of hydrogen from electrolysis.types of fuel cells Slide 10 Biological Hydrogen Gas ProductionAlgaeWater is the sourcesRather slowOxygen inhibitionDark Fermentation Waste Materials are the sources Mild environmental conditions Higher hydrogen gas production wrt Algae Light Fermentation Organic acids are the source Light requirementNo Oxygen inhibitionSpecial microrganisms Sensitive to environemtal condtions. Slide 11 Green Algae: Scenedesmus, Chlamydomonas Hydrogenase enzyme catalyzes 2H + + 2Xreduced 6 H2 + 2Xoxidized (X is ferrodoxin) Ferrodoxin is reduced by water in dark Ferrodoxin is reduced by organic compunds in the cell during light Slide 12 Advatages Water is the reneawable source CO 2 fixation Light energy utilization Disadvantages Hydrogenase enzymes is inhibited by the oxygen produced Production stops within minutes when exposed to light Low rate of production Slide 13 Slide 14 Ads: Water splitting as in algae Higher hydrogen production compared to algae Nitrogenase and hydrogenase enzymes work together Disad: Works in nitrogen limited environment Irreversiable inhibition by oxygen Hydrogen consuption by hydrogen uptake activity Slide 15 Organic sustances Carbohydrate Proteins Fats Organic Acids Acetic Butyric Propionic H2 +CO2 CH4 Slide 16 A maximum of 4 moles of H2 per mole of glucose can be produced concurrently with the production of energy (206 kJ per mole of glucose) C 6 H 12 O 6 ( glucose) + 2H 2 O 2C 2 H 4 O 2 ( Acetic Acid) + 2CO 2 + 4H 2 The complete oxidation of glucose to H 2 and CO 2 yields a stoichiometry of 12 mole H 2 per mole of glucose but in this case no metabolic energy is obtained 2C 2 H 4 O 2 ( Acetic Acid) 2 CO2 + 8H2 Overall reaction Glucose 12 H2 Slide 17 Glucose Utilization Some of the gucose is used for microbail growth End products Some of the end products do not produce hydrogen Propionic acid Lactic acid Ethanol Acetone Microorganism Methanogens Homoacetogens Clostridium Environmental Conditions pH Temperature ORP Nutrients Inhibitions H2 CO2 Organic acid Substrate Slide 18 4 mol H 2 / mol glucose Maximum Theoretical yield 2.5-3 mol H 2 /mol glucose Actual Yield Slide 19 Strict anaerobes: Clostridia Rumen bacteria: Ruminococcus Thermophiles: Thermoanaerobacter, Thermococcus kodakaraensis KOD1 Facultative anaerobes Enterobacter: high growth rates and utilization of a wide range of carbon sources, H2 production by Enterobacter is not inhibited by high H2 pressures. E. Coli: capable of producing H2 and CO2 from formate in the absence of oxygen Citrobacter: produce hydrogen from CO and H20 by the water-gas shift reaction under anaerobic conditions coupled to CH4 production and CO2 reduction. Slide 20 T= 30-50 0 C, pH = 5-7 ( has to be well controlled), final pH in anaerobic hydrogen production is around pH=4.0 - 4.8 Gradual decreases in pH inhibit hydrogen production since pH affects the activity of iron containing hydrogenase enzyme low initial pH=4.0-4.5 causes longer lag periods High initial pH levels such as 9.0 decrease lag time; however lower the yield of hydrogen production Butyric acid is produced at pH =4.0-6.0. Concentration of acetate and butyrate could be almost equal at pH=6.5-7.0 Slide 21 Dissolved Oxygen concentration = 0 mg/L, ORP < -200 mV Products: Organic acids Media Composition: Iron is required for ferrodoxin synthesis Rich carbon source: 20g/L or more C/N ratio = 100/1 Slide 22 Slide 23 Slide 24 Slide 25 Organic Acids Acetic Butyric Lactic H2 +CO2 Slide 26 Nitrogenase enzyme. The activity of the enzyme is inhibited in the presence of oxygen, ammonia or at high N/C ratios The metabolism shifts to utilization of organic substance for cell synthesis rather than hydrogen production in the presence of high nitrogen concentrations resulting in excess biomass growth and reduction in light diffusion Hydrogenase enzyme in photo-fermentative bacteria is an uptake hydrogenase which utilizes hydrogen gas and therefore is antagonistic to nitrogenase activity Complately anaerobic conditions Light requirement No oxygen production so no risk of enzyme inhibition Low rate of hydrogen production. Slide 27 ORGANISMS PHOTO-HETEROTROPHIC, ANAEROBIC BACTERIA Rhodobacter sp: R. spheroides, R.capsulatus, R. Rubrum Rhodosprllum sp Rhodopseudomonos sp. Environmental Conditions: T = 30 0 C, pH = 7 SUBSTRAT : Organic acids Products: H 2, CO 2, BIOMASS Slide 28 Slide 29 Slide 30 CELLULOSE AND STARCH WASTES GRINDING DELIGNIFICATION HYDROLYSISEnzymatic/Acid NEUTRALIZATION GLUCOSE SYRUP STEP I: PRE-TREATMENT GRINDING (Dp < 300 mikron) DELIGNIFICATION (CELLULOSIC BIOMASS)COOKING (STARCH - GRAINS) HYDROLYSIS (ACID OR ENZYMATIC) NEUTRALIZATION PRODUCT IS GLUCOSE SYRUP WITH HIGH GLUCOSE CONTENT Slide 31 GLUCOSE SYRUP NUTRIENT ADDITION DARK FERMENTATION ORGANIC ACIDS H2 and CO2 separation Slide 32 ORGANIC ACIDS NUTRIENT ADDITION LIGHT FERMENTATION H2 and CO2 separation Slide 33 GRINDING DELIGNIFICATION HYDROLYSIS GLUCOSE SYRUP WASTEWATER PRE- TREATMENT DARK FERMENTATION ORGANIC ACIDS LIGHT-FERMENTATION CO 2, H 2 H 2 SEPARATION CELLULOSE AND STARCH WASTES TREATED WASTEWATER PRETREATMENT CO 2 H2H2 Slide 34 THREE STAGE PROCESS: SEQUENTIAL ACID HYDROLYSIS, DARK AND PHOTO FERMENTATIONS IN SEPARATE STEPS TWO-STAGE PROCESS: SIMULTANEOUS BIO-HYDROLYSIS AND DARK FERMENTATION FOLLOWED BY PHOTO FERMENTATION BIOMASS Dark Fermentation Dark Fermentation H 2 Separation Hydrolysis Photo- Fermentation BIOMASS H 2 Separation Bio-hydrolysis + Dark Fermentation Bio-hydrolysis + Dark Fermentation Photo- Fermentation Slide 35 SIMULTANEOUS BIOHYDROLYSIS, DARK AND PHOTO FERMENTATIONS WITH LIGHT CYCLING BIOMASS H 2 Separation Bio-hydrolysis + Dark Fermentation + Photo-Fermentation Bio-hydrolysis + Dark Fermentation + Photo-Fermentation SIMULTANEOUS BIOHYDROLYSIS AND PHOTO FERMENTATION BY SPECIAL RHODOBACTER SPECIES BIOMASS H 2 Separation Bio-hydrolysis + Photo-Fermentation Slide 36 1. BATCH OR CONTINUOUS SUSPENDED CULTURE REACTORS 2. BIOFILM OR IMMOBILIZED CELL REACTORS 3. HYBRID REACTORS: SUSPENDED-IMMOBILIZED CELL REACTORS DARK FERMENTATION: BIOFILM REACTORS( BIOFILTERS) ARE PREFERRED BECAUSE OF COMPACT SIZE PHOTO-FERMENTATION: SUSPENDED CULTURE REACTORS ARE PREFERRED DUE TO LIGHT PENETRATION Slide 37 Slide 38 Slide 39 Slide 40 Slide 41 Slide 42 SPECIFIC RATE OF H 2 GAS PRODUCTION: (g H 2 / g biomass.h) HYDROGEN YIELD: (moles H2/ moles substrate) PERCENT H 2 IN GAS MIXTURE COST OF H 2 PRODUCTION ($/ g H2) OBJECTIVE: IMPROVE THE RATE AND YIELD OF H2 PRODUCTION AND REDUCE THE COST