Hydrogen From Biomass

HYDROGEN FROM BIOMASS

SR.NO

PARTICULARS

PAGE NO.

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ABSTRACT

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INTRODUCTION

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BIOMASS AS A RENEWABLE SOURCE

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PROCESS CONCEPT

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PRODUCTION OF BIO-OIL

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PRODUCTION OF HYDROGEN

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RESULTS & DISCUSSION

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ADVANTAGES OF PROCESS

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CONCLUSION

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BIBLIOGRAPHY

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HYDROGEN FROM BIOMASS

A SEMINAR REPORT ON

HYDROGEN FROM BIOMASS SUBMITTED BY

GUIDED BY

PRASAD M. RANADE

PROF. J.P.KAWRE

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.

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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.

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2 .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).

FIGURE 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 molecular weight compounds. It can also be used to saturate compounds, crack hydrocarbons or remove sulfur and C.O.E. & T. Akola

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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.

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3. 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 CO2 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 nonpetroleum renewable resource that can be utilized for sustainable production of hydrogen (Table 1). Therefore, a cost-effective energy-production process could be achieved in which agricultural wastes and various other biomasses are recycled to produce hydrogen economically.

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SOURCE

MAXIMUM OUTPUT

COMMENT

Biomass

9 × 1012 W

For total world land coverage.

Wind Power

6 × 10122 W

Regenerative Source

G EOTHERMAL S OURCE

Perhaps 109 W

For total world coverage. Required heavy-duty storage system. Restricted to specific areas (mid-ocean ridges very long term)

High Density Source 5

Nuclear Power

10 W or more

9

Fossil Fuels

10 W maximum allowable

No more than 1K rise in environment temp. Problems of waste disposal & safety. Pollution abatement is essential for small & largescale application.

Table 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). 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

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fermentation. Moisture, ash content and gross calorific values of different solid biomass feedstock are given in Table 2.

BIOMASS Bagasse Bagasse pitch Spent bagasse Saw Dust Rice husk Rice straw Deoiled rice bran Coffee Peanut shell Coconut shell Soya straw

MOISTURE (%) 50.0 40.0 40.0 35.0 10.0-15.0 6.0 16.0 11.0-14.0 10.0 10.0 7.0-8.0

ASH (%) 1.0-2.0 2.0 10.0 2.0 15.0-20.0 16.0 16.0 2.0-5.0 2.0-3.0 1.0 5.0-6.0

CV (MJ/Kg) 9.2 7.5-8.4 12.5 11.3 12.6-13.8 14.4 11.3 15-17.5 16.8 18.8 15.5-15.9

TABLE 2. MOISTURE, ASH CONTENT & GROSS CALORIFIC VALUE OF DIFFERENT BIOMASS

4. Process Concept

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FEEDSTOCK

HYDROGEN FROM BIOMASS

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 bio-oil 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 750-850ºC over a nickel-based catalyst is a two-step process that includes the shift reaction:

Bio-oil + H2O CO + H2O

CO + H2 CO2 + H2

The overall stoichiometry gives a maximum yield of 17.2-g H/100 g bio-oil 11.2 wt.% based on wood).

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Fig.2 Mass 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

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5.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 500oC 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 600-625°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

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10 kg/h. eventually, 200-300 kg of pyrolysis oil was generated from feedstock. Peanut shell oil was collected in the scrubber of the pyrolysis system as a twophase 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

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.

Figure 3. Production of bio-oil by fast pyrolysis

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PHYSICAL PROPERTIES

TYPICAL VALUE

Moisture content pH Specific gravity Elemental analysis, dry basis C H O (by difference) N Ash HHV as produced (depends on moisture) Viscosity (at 40ºC and 25% water) Solids (char) Distillation

15–30% 2.5 1.20 56.4% 6.2% 37.3% 0.1% 0.1% 16–19 MJ/kg 40–100 cp. 0.5% max. 50% as liquid degrades

Table 3 : 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.

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6. 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 150-200g of commercial nickel-based catalyst from UCI (C11-NK) ground to the particle size of 300-500µm. 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.

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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. The temperatures in the system as well as the flows were recorded and controlled by the OPTO data acquisition and control system.

Figure 4. Hydrogen production from Biomass

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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. The steam reforming experiments in the fluidized bed reactor were carried out at the temperature of 8000C and 8500C. The steam to carbon ratio varied from 7 to 13, while the methane-equivalent gas hourly space velocity GC1HSV was in the range of 1200-1500 h-1.

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7.RESULTS & DISCUSSION Gas composition (on nitrogen free basis) obtained from the peanut shell pyrolysis oil is shown in Figure 6.

Figure 6. Composition of the gas produced during steam reforming of peanut shell bio-oil carbohydrate-derived fraction at 850°C and S/C=9

 During eight hours of the experiment, the gas composition was very stable and only a small decrease in the concentration of hydrogen and an increase in methane were observed.  Methane concentration, though it grew to 3000-4000 ppm, still remained an order of magnitude smaller than that of the three major gas components and, therefore, is not shown in Figure 6.

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 More fluctuation was observed in the amount of gas produced and, consequently, in the yield of hydrogen from the peanut bio-oil fraction, which is presented in Figure 7.

Figure 7. Yield of hydrogen obtained during reforming of peanut shell bio-oil carbohydratederived fraction at 850°C and S/C=9 [3].



The hydrogen yield was still at the level of 80% of the stoichiometric potential after eight hours on stream.



Peanut shell liquid had a higher concentration of the organic compounds, especially of lignin oligomers than the wood oil fractions. Large molecules of lignin compounds are less reactive and probably required a longer contact time with the catalyst than the smaller carbohydrate-derived fragments. They are also more likely to form carbon deposits on the catalyst surface.

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 However, at 850°C, these deposits were removed and converted to hydrogen and carbon oxides by steam processing (carbon to gas conversion of 92%).  This resulted in hydrogen yields greater than 80% of the stoichiometric potential during eight-hour catalyst time on stream.  The yields of hydrogen would be 5-7% higher if the reforming was followed by water-gas shift processing of carbon monoxide in the product gas. 

The global mass balance closure for the whole experiment was 94%, and 8891% of bio-oil carbon was converted to gases. Both the decrease in the hydrogen production and the missing carbon in the mass balance suggest that a small part of the carbon from bio-oil formed deposits on the catalyst surface. Steam treatment of the used catalyst performed at 850°C resulted in the release of hydrogen and CO2 in the amount corresponding to 4-5% of the carbon fed (about half of the missing carbon). The other part of carbon unaccounted for was probably entrained by product gases together with the catalyst fines and collected in the cyclone and condensers.

 The steam treatment - by removing deposits from the surface also regenerated the catalyst, which performed during the following test at the same level of activity as the fresh catalyst.

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8.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 longterm 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.

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 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.

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9.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 biomassderived 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.

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BIBLIOGRAPHY



I & EC Research, 36, 1507-1518.



Production of Hydrogen from Biomass by Catalytic Steam Reforming of Fast Pyrolysis Oil., Energy & Fuels, 12, 19-24.



Web Sites:



www.eere.energy.com



www.eprida.com



www.pyne.com

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