DEVELOPMENT OF A BIOMASS PYROLYSIS REACTOR AND CHARACTERISATION OF ITS PRODUCTS FOR INDUSTRIAL APPLICATIONS

1. DEVELOPMENT OF A BIOMASS PYROLYSIS REACTOR AND CHARACTERISATION OF ITS PRODUCTS FOR INDUSTRIAL APPLICATIONS Titiladunayo, Isaac Femi Department of Mechanical Engineering The Federal University of Technology Akure.Ondo State. Nigeria JANUARY, 2012

2. Introduction • It comprises:- aggregate of all biologically produced matter inform of: • wood and wood wastes; • agricultural crops and their waste by-products; • municipal solid wastes; • animal wastes; • wastes from food processing; • and aquatic plants including sea weeds and algae (Agarwal and Agarwal, 1999; U.S Dept of Energy, 2003). • Biomass is cheap, available, affordable and reliable • It’s a regular source of rural energy in Nigeria, fuel wood is cheap, easily accessed by both rural & urban dwellers.

3. Introduction • Biomass – renewable, available, and abundant on earth. • It is a versatile energy and chemical resource • It could be converted into renewable products that could significantly supplement the energy needs of society

4. Introduction Cont.--- • Globally, 140 billion metric tons of biomass is generated every year from agriculture. • This volume of biomass can be converted to an enormous amount of energy and raw materials, equivalent to approximately 50 billion tons of oil. • Agricultural biomass waste converted to energy can substantially displace fossil fuel, reduce emissions of greenhouse gases and provide renewable energy to some 1.6 billion people in developing countries, which still lack access to electricity. • As raw materials, biomass wastes have attractive potentials for large-scale industries and community-level enterprises (UNEP 2009).

5. Biomass Resource & Availability Wood Cuttings (2) Wood Cuttings (1) 2 1 Wood Wastes 3 4 Wood Dust Fig.1:Forest Biomass

6. Biomass Resource & Availability Cont... • Municipal Solid Wastes (MSW): generation is enormous in our society. • The expanding urban centres in Nigeria have tremendous production of solid wastes that could be utilized for energy through different conversion routes. Garbage wastes due to human & animal activities are massive • Lagos with 18 million inhabitants generates about 9,000 metric tons of municipal solid waste daily (0.5 kg/person/day), 80 percent of this waste can be reconverted (LAWMA, 2010). Ibadan: 0.37–0.5 kg/person/day (Maclaren International Ltd, 1970)

7. Fig.2: Ojota dumpsite, Lagos, Nigeria. (Courtesy: LAWMA, 2010)

8. MSW - Material Distribution • Composition of MSW – Variable • 50% Lignocellulosic Mat.(Wood, paper etc) • 15% synthetic polymer based materials- Polyethylene (PE), Polypropylene (PP) and Polyvinylchloride (PVC) • 20% inorganic materials (metals, glass etc) • 15% others (Blasi, 1997) • Natural Decomposition- May affect environment & climate change • Recycling waste for energy and chemicals products will consume waste and safe the environment

9. Straws and Grasses for Energy Rice Straw Miscanthus Fig.3: Straw and Grasses

10. Wood composition Cellulose and hemi-cellulose contain only around 17.5 MJ/kg high heating values (HHV) while lignin has about 26.5 MJ/kg HHV and extractives can approach 35 MJ/kg HHV (Ramachandra and Kamakshi, 2005; NC State, 1993

11. Polymeric Constituent of woody Biomass 1. Cellulose (C6H10O5)n •Structure, fibre walls •Carbohydrate (sugar) •Polymer of glucose C6H10O6 2 Hemicellulose(C5H8O4)n •Encasing of cellulose fibre •Carbohydrate •Other than glucose •Dissolvable 3 Lignin (C40H44O6) •Binding agent / strength •Non-sugar polymer •Aromatic structure

12. Biomass Conversion Routes

13. Particle size Preparation • Process: Chipping, grinding and milling to reduce particle size. • Materials size after chipping 10–30 mm • Size after milling or grinding 0.2–2 mm. • Type of milling M/C: (i) Vibratory ball milling (ii) Ball milling (Millet et al.,1976)

14. Biochemical biomass Conversion • Fermentation is the biochemical route of converting sugar, starch or hydrolysedlignocellulosic biomass to ethanol (alcohol) in a process similar to anaerobic respiration • Milling to an optimum size to facilitate effective pretreatment. • Pretreatment to facilitate effective Hydrolysis and fermentation. • Hydrolysis - conversion of cellulose to sugars • Fermentation of sugars to bioethanol. • Filtration and/or distillation to remove the byproducts from the bioethanol. • Management of Waste by-product.

15. Biomass Thermochemical conversion Routes

16. Biomass Energy Conversion Routes: • Direct Combustion: Exothermic reaction of biomass combustible elements with Oxygen. • Biomass locked-up energy is released by burning. • The combustible elemental composition of biomass is completely oxidized to H2O & CO2 with the release of heat and light (FAO, 1987). • requires adequate air supply;

17. THE PYROLYSIS PROCESS: • Carbonisation: Upgrades biomass energy to high dense energy fractions in a quiescence environment • The three major biomass polymer building blocks degrades to charcoal, pyroligneous liquor and syngas • Process is influenced: heating rate, residence time, particle size, chemical composition, moisture content and final pyrolysis temp. of the wood feedstock.

18. Reaction Temperatures • Effect of temperature on biomass • At a temperature less than 260ºC Charring of biomass feedstock occurs • Between 275ºC and 400ºC depolymerisation of chemical components generally predominates • Between 200ºC and 280ºC hemicellulose is converted to methanol and acetic acid • Above 280 ºC lignin decomposes to produce tar and charcoal (Hillis, 1975; Bailey and Blankehorn, 1982; Fuwape, 1996).

19. HEAT HEAT Lignin Hemicellulose Pyro-oil (methanol + Acetone+ Acetic Acid + Tar + etc), + Pyrogas(CO + CO2+ CH4+ H2 + unburnt hydrocarbons), + Char

20. Economic Advantage of Biomass Energy • Utilizing forest residues, mill residues, logging residues and various wood cuttings for charcoal production will go a long way to boost domestic and industrial energy resources, thereby reduce pressure on the forest. • Inexhaustible production of renewable fuel & chemicals is guaranteed • It improves the environment, as waste is consumed & the effect of Methane is mitigated • Wood conversion to charcoal is a process involving the thermal separation of its volatile constituent from the char residue.

21. Economic Advantage of Biomass Energy • Charcoal is a high-grade fuel having a heating value of 28.7-34 MJ/kg compared to wood of 20-26.5 MJ/kg (Fuwape, 1996). • Charcoal is easier to handle than the parent stock, • Fuel for household and industrial settings (metal extraction in iron smelting, generating producer gas, serves as activated carbon particles for water treatment systems) (FAO, 1985). • Pyroligneous oil is used as fuel oil substitute, chemical sources, solvent and insecticide

22. Industrial Utilization of Charcoal • Chemical Industries - manufacture of carbon disulphide, sodium cyanide and carbides, ethanol, methanol, Acetic acid, etc • Iron Smelting - smelting and sintering iron ores, production of ferro-silicon and pure silicon, case hardening of steel, etc • Fuels -fuelsin foundry, cupolas, electrodes in metallurgical industries, etc • Water and Gas Purification -dechlorination, gas purification, solvent recovery; waste water treatment, etc • Gas Generator - In the production of producer gas for vehicles and carbonation of soft drinks.

23. Charcoal as fuel for industry • The advantages of charcoal depend on six significant properties which account for its continued use as fuel in industry. • relatively few and unreactive inorganic impurities • stable pore structure with high surface area • low sulphur content • high ratio of carbon to ash • good reduction ability • almost smokeless

24. Pyroligneous Liquor • Crude condensate consists mainly of water and non-water component: • Crude bio-oil is dark brown and approximates to biomass in elemental composition. • It is composed of a very complex mixture of oxygenated hydrocarbons with an appreciable proportion of water from both the original moisture and reaction product. Solid char may also be present.  • The liquid has a distinctive odour - an acrid smoky smell, which can irritate the eyes if exposed for a prolonged period to the liquids. The cause of this smell is due to the low molecular weight aldehydes and acids.

25. Properties of Pyrolysis oil • (i) Oxygen content 35 – 50 wt% • (ii) Identified 300compounds • (iii) Water Content 15 – 30wt% • (iv) LHV 14 -18 MJ/kg • (v) Density (ρ) 1.15 – 1.25 kg/dm3 • (vi) pH-value 2-3 • (vii)Molecular Weight 370 - 1000g/mol • (viii) Volatility Boiling Start 100°C Residues left (5-50 %) Stop 250-280°C (Czernik & Bridgwater, 2004; Oasmaa& Stefan, 1999)

26. Non- Condensable gas (Syngas) • Wood gas is useable as fuel • It consists typically of: • 17% methane; • 2% hydrogen; • 23% carbon monoxide; • 38% carbon dioxide; • 2% oxygen • and 18% nitrogen. • It has a gross calorific value of about 10.8 MJ/m³ (290 BTU/cu.ft.) i.e. about one third the value of natural gas. Source: FAO (1985)

27. Inorganic Constituents of Ash • Ash is a good source of calcium, potassium, phosphorus, magnesium, Sodium, Iron, Zinc, silicon, Copper and aluminium. • Ash from woody biomass, in general, stimulates microbial activities and mineralization in the soil by improving both the soil's physical and chemical properties (Soil amendment). • Wood ash neutralizes soil acidification caused by whole-tree harvesting as well as acid depositions (raise the pH of acidic soils)

28. The Pyrolysis Plant • A pyrolysis plant is developed to produce higher dense energy products from renewable biomass through thermochemical conversion processes. • The plant does not produce useful energy directly. • More convenient high grade energy & chemical products, are produced under regulated heat load and restricted air supply.

29. Slow and Fast Pyrolysis • Temperature = Low/Moderate • Heating Rate = Low/High • Carrier gas = Not required/ Required • Material Residence time = Long/short • Vapor Residence time = Long/short • Particle size = ≥ 10cm / ≤ 1mm • Oil yield = Could be low/ High (70-80%)

30. Biomass Charcoal Production Techniques • Pit carbonisation method • Kiln carbonisation method • This method is termed; charcoal burning, as part of the wood charge is burnt to supply the needed heat for the effective transformation of the remaining wood charge to charcoal. Pit Mound (Liberia) Beehive kilns (USA) FAO, 2008 FAO, 2008 Fig.4: Kilns

31. Retort Processes: • The retort process (destructive distillation of wood) came into industrial use in the 18th and 19th century (Fapetu, 2000). • Heat for carbonisation in this process is externally supplied to a closed vessel, which contains the woodchips to be carbonised (FAO, 1987). • Volatiles are captured and collected through various cooling or condensation devices. • Pyrolysis in the kiln and retort devices occur in three notable phases: drying, pyrolysis, & cooling for the products of biomass.

32. The retort principle for carbonization (FAO, 2008) (A) (B) (C) A continuous rotary retort Fig.5: Retorts Lambiotte Retort (France)

33. Fig. 6: Charcoaling Retorts

34. Unzipping of Biomass polymer chain

35. Biomass Thermal Degradation Cont.. • Percentage charcoal yield decreases with increasing carbonisation temperature. • The percentage yield of combustible gases (Syngas) & pyroligneous liquor is a function of: • carbonisation temperature • & degree of biomass polymerisation.

36. Justification (What has been done) • Several studies considered wood carbonisation from 150-550°C (Bailey & Blankehorn, 1982; Fuwape 1996; Gommaa and Mohed, 2000; Shinya & Yukiwko, 2008). • Conversion of wood to charcoal is affected by the heating rate, residence time, particle sizes, chemical composition and moisture of the wood and the final pyrolysis temp. (Fuwape 1996). • Traditional kilning techniques (yield charcoal usually in the range of 5%-20% of the parent stock) & • Industrial / Modern retorting techniques(20%-30%) (FAO, 2008). • Charcoal yield takes between 7-30 days in the traditional kiln (Sanabria & Paz, 2001; SINTEF Energy Research, 2010).

37. Justification (Need for Current Work) • Need to investigate the effect of higher temperature on lignocellulosic biomass than previously reported. • Development of a pyrolysis plant with a comparative edge at reducing carbonisation time, and improving carbon yield at elevated temperatures. • Most research work by authors; focused on temperate wood species, a need therefore arises for the physiochemical characterisation of tropical wood species and their thermochemical by-products. • The effectiveness of the pyrolysis plant at handling variety of biomass species is investigated. The relationship between biomass yield as a function of the degree of biomass polymerisation and temperature is established.

38. Scope of the Project • Development of an electrically fired, fixed-bed reactor with electronics accessories and equipped with a pyrolysis furnace with selected refractory lining. • Feedstock selection, sizing and preparation • Experimentation, Documentation and Data Analysis

39. Main objective: todevelop biomass pyrolysis reactor and characterise its products for industrial applications • Specific objectives: • develop a thermochemical reactor, for the conversion of selected lignocellulosic biomass materials into high grade energy and industrial products; • evaluate the effects of temperature on the degree of carbonisation of the solid products; • determine the physio-chemical, thermo-chemical and the gross energy characteristics of the selected biomass and their derived fractions; and • assess their suitability for industrial applications. OBJECTIVES

40. DEVELOPMENT OF THE FIXED-BED REACTOR • Furnace development • Selection of appropriate refractory clay materials for lining the furnace of the pyrolysis plant from four locations in Ekiti State: - IkereEkiti, FagbohunEkiti, IshanEkiti and AraEkiti. Fig .7: Kaolin (China Clay)

41. DEVELOPMENT OF THE REACTOR Cont…. • Appropriate refractory clay selection as furnace lining was based on: • Meeting known physical, chemical, and refractory standards; • Ability to withstand thermal shock & very high operating temperature (1800°C) without thermal deformation. • Non-reactive characteristics with pyrolysis products at elevated temperatures. • Efficient thermal conservation

42. Table.3:Chemical Characteristics of Selected Clays Mean and Standard Deviation of chemical Properties A = Ikere-Ekiti, B = Fagbohun - Ekiti, C = Ishan -Ekiti, D = Ara -Ekiti Values in the same column with different alphabet are significantly different from each other. (Result of Chemical test of Clays from selected sites in Ekiti State, Nigeria)

43. Table.4: Mean and Standard Deviation of the Physical characteristic of the selected Clay Physical Characteristics of Selected Clays A = Ikere-Ekiti, B = Fagbohun - Ekiti, C = Ishan -Ekiti, D = Ara –Ekiti Values in the same column with different alphabet are significantly different from each other.

44. Table 5 : Result of Refractoriness test on selected Clays

45. The densities (ρClay) of the clay materials are functions of the major constituents of the (alumino-silicate ) refractory clay samples • Porosity is also a function of density • Bulk density is highly significant in predicting the apparent porosity of the clay samples: R2 = 0.97889

46. The reactor : -Electrically–fired Furnace chamber -An airtight crucible (Fixed-Bed) -Control Box (With digital readout) - Step-down transformer - Counter-flow Liebig condenser - Pyro-oil traps - Gas displacement vessel - Cooling water circulation pump REACTOR COMPONENTS

47. THE FURNACE • Developed from locally available materials • Wall thickness was determined using: • Appropriate heat transfer design tools in furnaces • Thermo-chemical and refractory properties of kaolin and the maximum designed furnace temperature • Heating rate was achieved by regulating the input voltage from the circuit’s transformer. • Resistance (R1 and R2) of two heater elements connected in parallel, which is the equivalent resistance of the electrical connection in Fig (1) and (2).

48. R1 V V R2 RR2 Req V V FIG. 8: Resistance Elements Connected in Parallel HEAT INPUT

49. HEAT INPUT Contd The total energy (Q) supplied to the furnace is obtained by substituting equation (4) into (3)

50. Ceramic wall Fig.9 : Furnace Wall Heat conduction through the furnace wall is obtained by applying the general heat conduction equation in cylindrical coordinate (Rajput, 2007; Yunus, 2002).