HYDROGEN FROM BIOMASSSS

Transcription

1 HYDROGEN FROM BIOMASSSS Submitted By SHAIKH AMIR B. PAWAR SUDHIR R. NOOKALA HARSH. 1

2 SR.NO PARTICULARS PAGE NO. 1 INTRODUCTION 4 2 BIOMASS AS A RENEWABLE SOURCE 6 3 PROCESS CONCEPT 9 4 PRODUCTION OF BIO-OIL 11 5 PRODUCTION OF HYDROGEN 14 6 ADVANTAGES OF PROCESS 17 7 CONCLUSION 18 8 BIBLIOGRAPHY 19 2

3 ABSTRACT: Many efforts have been made to produce an alternative to natural gas. One leading idea is that of renewable hydrogen. Hydrogen is the prototype of the environmentally cleanest fuel of interest for power generation using fuel cells. At present, hydrogen is produced almost entirely from fossil fuels such as natural gas, naphtha and inexpensive coal. However these processes are not environment friendly as carbon emissions are always associated with them. Biomass as a product of photosynthesis is a renewable source that can be used for sustainable production of hydrogen. However, direct production of hydrogen from biomass by gassification/water gas shift technology is unfavorable economically, except for very low cost feed stocks and very large plants. The approach proposes an alternative strategy with potentially better economics resulting from the combined production of hydrogen with valuable co-products. The proposed strategy can be applied to any lignocellulosic biomass either from agriculture or from forest operations. The process involves the thermo-chemical conversion of biomass to hydrogen by catalytic steam reforming of specific fractions derived from fast pyrolysis and aqueous/steam process of biomass. Bio-oil (as a whole or it s selected fractions) can be converted to hydrogen via catalytic steam reforming followed by a water gas shift conversion step. Fast pyrolysis, a technology near commercial scale, could be carried out in a regional network of plants that would supply bio-oil to a central reforming facility. The preferred option is to separate biooil into a lignin-derived fraction, which could be used for producing phenolic resins or fuel additives and a carbohydrate derived material that would be steam reformed to produce hydrogen. The co-product strategy can also be applied to residual fractions derived from pulping operations and from ethanol production. Hydrogen can be generated from these fractions that are currently available in most pulp mills and that will available in future. 3

4 1. Introduction: It is widely acknowledged that hydrogen is an attractive energy source to replace conventional fossil fuels, both from the environmental and economic standpoint. It is often cited as a potential source of unlimited clean power. When hydrogen is used as a fuel it generates no pollutants, but produces water, which can be recycled to make more hydrogen (Figure 1.1). Fig1.1 HYDROGEN ENERGY SYSTEM Apart from its use as a clean energy resource, hydrogen can be used for various other purposes in chemical process industries. It is used as a reactant in hydrogenation process to produce lower 4

5 molecular weight compounds. It can also be used to saturate compounds, crack hydrocarbons or remove sulfur and nitrogen compounds. It is a good oxygen scavenger and can therefore be used to remove traces of oxygen to prevent oxidative corrosion. In the manufacturing of ammonia, methanol and synthesis gas, the use of hydrogen is well known. The future widespread use of hydrogen is likely to be in the transportation sector, where it will help reduce pollution. Vehicles can be powered with hydrogen fuel cells, which are three times more efficient than a gasoline-powered engine. As of today, all these areas of hydrogen utilization are equivalent to 3% of the energy consumption, but it is expected to grow significantly in the years to come. The commercially usable hydrogen currently being produced is extracted mostly from natural gas. Nearly 90% of hydrogen is obtained by steam reformation of naphtha or natural gas. Gasification of coal and electrolysis of water are the other industrial methods for hydrogen-production. However, these processes are highly energy-intensive and not always environment-friendly. More over, the fossil fuel (mainly petroleum) reserves of the world are depleting at an alarming rate. So, production of hydrogen by exploiting alternative sources seems imperative in this perspective. Biomass is such an alternative. 5

6 2. BIOMASS AS A RENEWABLE RESOURCE Biomass is defined as a material that has participated in the growing cycle in Agriculture waste, forest residue, urban wood waste, and trees and grasses grown, as energy crops are materials commonly referred to as biomass. Because biomass consumes as much CO2 in the growing cycle as is produced when it is transformed into energy, the net CO 2 contribution from biomass-derived fuels is considerably less than from fossil-derived fuels. In addition, producing biomass on a sustainable basis by growing energy crops will support agricultural sector, an important part of our economy. Successful commercialization of this technology will also reduce oil and gas imports of the country. Biomass, as a product of photosynthesis, is the most versatile non-petroleum renewable resource that can be utilized for sustainable production of hydrogen (Table 2.1). Therefore, a costeffective energy-production process could be achieved in which agricultural wastes and various other biomasses are recycled to produce hydrogen economically. 6

7 SOURCE MAXIMUM OUTPUT COMMENT Regenerative Source Biomass W For total world land coverage. Wind Power GEOTHERMAL SOURCE High Density Source Nuclear Power Fossil Fuels W Perhaps 10 9 W 10 5 W or more 10 9 W maximum allowable For total world coverage. Required heavy-duty storage system. Restricted to specific areas (midocean ridges very long term) No more than 1K rise in environment temp. Problems of waste disposal & safety. Pollution abatement is essential for small & large-scale application. Table 2.1: Earth-based world power sources and possible practical expectations As an energy source, biomass has several important advantages. Renewability is obviously a key feature. It also has unique versatility. The list of plant species, by-products and waste materials that can potentially be used as feedstock is almost endless (Table 2.1). Major resources in biomass include agricultural crops and their waste by-products, lignocellulosic products such as wood and wood waste, waste from food processing and aquatic plants and algae, and effluents produced in the human habitat. Moderately dried wastes such as wood residue, wood scrap and urban garbage can be burned directly as fuel. Energy from water-containing biomass such as sewage sludge, agricultural and livestock effluents as well as animal excreta is recovered mainly by microbial fermentation. Moisture, ash content and gross calorific values of different solid biomass feedstock are given in below Table 2.2 7

8 BIOMASS MOISTURE (%) ASH (%) CV (MJ/Kg) Bagasse Bagasse pitch Spent bagasse Saw Dust Rice husk Rice straw Deoiled rice bran Coffee Peanut shell Coconut shell Soya straw TABLE 2.2 MOISTURE, ASH CONTENT & GROSS CALORIFIC VALUE OF DIFFERENT BIOMASS FEEDSTOCK 8

9 3. Process Concept Unfortunately, hydrogen content in biomass is only 6-6.5%, compared to almost 25% in natural gas. For this reason, on a cost basis, producing hydrogen by a direct conversion process such as the biomass gasification/water-gas shift cannot compete with the well-developed technology for steam reforming of natural gas. However, an integrated process, in which biomass is partly used to produce more valuable materials or chemicals with only residual fractions utilized for generation of hydrogen, can be an economically viable option. The proposed method, which was described earlier, combines two stages: fast pyrolysis of biomass to generate bio-oil and catalytic steam reforming of the bio-oil to hydrogen and carbon dioxide. The original concept was that the pyrolysis oil could be fractionated into two fractions based on water solubility. The water-soluble fraction is to be used for hydrogen production and the water insoluble fraction could be used in adhesive formulation. The biooil can be stored and shipped to a centralized facility where it is converted to hydrogen via catalytic steam reforming and shift conversion. Catalytic steam reforming of Bio-oil at ºC over a nickel-based catalyst is a two-step process that includes the shift reaction: Bio-oil + H 2 O CO + H 2 on wood. CO + H 2 O CO2 + H 2 The overall stoichiometry gives a maximum yield of 17.2-g H/100 g bio-oil 11.2 wt.% based 9

10 Fig.3.1Mass balance diagram of hydrogen production The actual process involve two stages: 1) Production of bio-oil by fast pyrolysis 2) Production of Hydrogen by catalytic steam reforming 10

11 4: Production of bio-oil by fast pyrolysis Fast pyrolysis is a high temperature process in which biomass is rapidly heated in the absence of oxygen. As a result it decomposes to generate mostly vapors and aerosols and some charcoal. After cooling and condensation, a dark brown mobile liquid is formed which has a heating value about half that of conventional fuel oil. While it is related to the traditional pyrolysis processes for making charcoal, fast pyrolysis is an advanced process, which is carefully controlled to give high yields of liquid. The essential features of a fast pyrolysis process are: Very high heating and heat transfer rates, which usually requires a finely ground biomass feed. Carefully controlled pyrolysis reaction temperature of around 500 o C in the vapor phase, with short vapor residence times of typically less than 2 seconds. Rapid cooling of the pyrolysis vapors to give the bio-oil product. The Process: Pelletized peanut shells were pyrolyzed using the fast ablative pyrolysis system (vortex reactor). The reactor wall temperature was maintained within the range of C, which has been proven to provide the highest bio-oil yield. Nitrogen at a flow rate of 15 kg/h was used as the carrier gas for the biomass particles in the pyrolysis reactor. The tests proceeded smoothly at the rate of 10 kg/h. eventually, kg of pyrolysis oil was generated from feedstock. Peanut shell oil was collected in the scrubber of the pyrolysis system as a two-phase liquid (water was used for scrubbing pyrolysis vapors), with the top fraction containing 32.3% organics (6% are lignin-derived oligomers) and 67.7% water. Water content of the liquids was determined by Karl-Fisher titration 11

12 method using a Metrohm 701 KF Titrino analyzer. Elemental composition, including the carbon, hydrogen, and oxygen content of these liquids was analyzed by a commercial laboratory. The aqueous solutions were then used in reforming tests to produce hydrogen. Fig 3.2. Production of bio-oil by fast pyrolysis 12

13 PHYSICAL PROPERTIES TYPICAL VALUE Moisture content 15 30% ph 2.5 Specific gravity 1.20 Elemental analysis, dry basis C 56.4% H 6.2% O (by difference) 37.3% N 0.1% Ash 0.1% HHV as produced (depends on moisture) MJ/kg Viscosity (at 40ºC and 25% water) cp. Solids (char) 0.5% Distillation max. 50% as liquid degrades Table 3.1: Typical properties and characteristics of pyrolysis oil Characteristics: Liquid fuel. Easy substitution for conventional fuels in many static appliance boilers, engines, turbines. Does not mix with hydrocarbon fuels. Not as stable as fossil fuels. Heating value is about 40% that of fuel oil or diesel on a weight basis and 60% on volume basis. 13

14 5. PRODUCTION OF HYDROGEN BY CATALYTIC STEAM REFORMING: The experiments were carried out using a bench-scale fluidized-bed steam reformer. The schematic of the fluidized bed system is shown in Figure 4. The two-inch-diameter Inconel reactor supplied with a porous metal distribution plate was placed inside a three-zone electric furnace. The reactor contained g of commercial nickel-based catalyst from UCI (C11-NK) ground to the particle size of µm. The catalyst was fluidized using superheated steam, which was also a reactant in the reforming process. Steam was generated in a boiler and superheated to 750 C before entering the reactor at a flow rate of 2-4 g/min. Liquids were fed at a rate of 2-5 g/min using a diaphragm pump. A specially designed oil injection nozzle supplied with a cooling jacket was used to spray liquids into the catalyst bed. The oil temperature in the injector was controlled by a coolant flow and maintained below boiling point to prevent premature evaporation of volatiles and consequent deposition of nonvolatiles. The condensate was collected in a vessel whose weight was continuously monitored. The outlet gas flow rate was measured by a mass flow meter and by a dry test meter. The gas composition was analyzed every 5 minutes by an MTI gas chromatograph. The analysis provided concentrations of hydrogen, carbon monoxide, carbon dioxide, methane, ethylene, and nitrogen in the outlet gas stream as a function of time. 14

15 The temperatures in the system as well as the flows were recorded and controlled by the OPTO data acquisition and control system. Figure 4.1 Hydrogen production from Biomass The measurements allowed determination of the total and elemental balances for the reforming tests as well as the calculation of the yield of hydrogen generated from the biomass-derived liquid feed. The maximum (stoichiometric) yield of hydrogen was 2+m/2n-k/n moles per mole of carbon in feed. Therefore, 63 g of hydrogen could be theoretically obtained from 1 L of peanut shell oil extract. 15

16 The steam reforming experiments in the fluidized bed reactor were carried out at the temperature of C and C. The steam to carbon ratio varied from 7 to 13, while the methane-equivalent gas hourly space velocity GC1HSV was in the range of h

17 6.ADVANTAGES OF THE PROCESS The anticipated potential benefits or impact include: Use of biomass will support and further expand the agriculture-related sector. Application of the proposed technology will provide an economical and environmentally acceptable means of disposing of the large quantity of peanut shells. The demand for peanut shells as feedstock of the proposed technology will improve the economic competitiveness of the peanut industry secures long-term future. Widespread use of renewable hydrogen, the cleanest fuel for power generation and for transportation applications, will reduce oil and gas imports and will have significant environmental and health benefits for the major cities. The proposed process will produce co-products in addition to hydrogen. Alternative co-products that may be obtained from different bio-oil fractions include phenol (for phenol-formaldehyde resins) and fuel oxygenates. Similar to petroleum crude oil, biomass pyrolysis oil can be used for the production of a multitude of fuel and chemical products, in addition to hydrogen. The development of new agro-industrial infrastructure options that could result in sustainable and equitable growth. The inclusion of small farms and the attention to the appropriate scale of production technology will ensure the ability to distribute the benefits of enhanced materials along the value chain to the communities involved in generating the wealth. 17

18 7. Conclusion Biomass can be a valuable resource for producing hydrogen if done as an integrated process that also generates higher value co-products. Fluidized bed reactor configuration proved to be efficient for reforming biomass-derived liquids. It can be used for producing hydrogen by co-processing bio-oils with natural gas or liquid hydrocarbons. The process needs to be optimized to determine conditions that allow for maximum yields of hydrogen and minimum coke formation. 18

19 8: BIBLIOGRAPHY Production of Hydrogen from Biomass by Catalytic Steam Reforming of Fast Pyrolysis Oil., Energy & Fuels, 12, Web Sites: