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Titiladunayo, Isaac Femi Department of Mechanical Engineering

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1 Titiladunayo, Isaac Femi Department of Mechanical Engineering
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). The United Nations Environment Programme (UNEP)

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 Softwood Hardwood Cellulose content 42% +/- 2% 45% +/- 2% Lignin content 28% +/- 3% 20% +/- 4% Extractives content 3% +/- 2% 5% +/- 3% Fibre length 2-6 mm mm Coarseness 15-35 mg/100 mm 5-10 mg/100m 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
Biochemical Conversion Thermochemical Conversion Screening, Pretreatments, Fermentation, Filtration, Distillation, Effluent treatment Slow Pyrolysis (Carbonisation), Fast pyrolysis, Flash Pyrolysis, Ablative Pyrolysis, Gasification.

13 Particle size Preparation
Process: Chipping, grinding and milling to reduce particle size. Materials size after chipping –30 mm Size after milling or grinding –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 hydrolysed lignocellulosic 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. Bioethanol & Biogas production –Root, tubers, grains, seeds, manures,etc Biodiesel production from oil seeds, fruits, sunflowers etc.

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; Carbonization is the energy conversion process undertaken with the intention to maximize the production of char at the expense of other pyrolysis products. The basic reaction in wood carbonization involves the expulsion of water from its cellulose structure, thus maximizing its carbon percentage.

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 Biomass Lignin Cellulose HEAT 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 MJ/kg compared to wood of 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 - fuels in 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. Crude pyrolysis liquid or 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

25 Properties of Pyrolysis oil
(i) Oxygen content – 50 wt% (ii) Identified compounds (iii) Water Content – 30wt% (iv) LHV MJ/kg (v) Density (ρ) – 1.25 kg/dm3 (vi) pH-value (vii)Molecular Weight g/mol (viii) Volatility Boiling Start 100°C Residues left (5-50 %) Stop °C (Czernik & Bridgwater, 2004; Oasmaa& Stefan, 1999) Density for Diesel oil/gas (ρ)= kg/dm3, Heating Value = 60% Diesel.

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 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 Pit Mound (Liberia) Beehive kilns (USA)
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)
(B) Beehive kilns in Canyon Creek, Wise River Ranger District, Montana (USA) (C) Multiple hearth kiln A continuous rotary retort Lambiotte Retort (France) Fig.5: Retorts

33 Fig. 6: Charcoaling Retorts

34 Unzipping of Biomass polymer chain
Residual fractions: Pyroligneous liquor Non–condensable portion (syngas) The char residues (charcoal

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 °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 Feedstock selection, sizing and preparation
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 OBJECTIVES Specific objectives:
Main objective: to develop 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.

Furnace development Selection of appropriate refractory clay materials for lining the furnace of the pyrolysis plant from four locations in Ekiti State: - Ikere Ekiti, Fagbohun Ekiti, Ishan Ekiti and Ara Ekiti. Fig .7: Kaolin (China Clay)

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 S/No Clay Samples % Al2O3 SiO2 K2O CaO Ti2O MnO Fe2O3 MgO Na2O Cr2O3 LOI 1 A 30.46± 0.89a 50.92± 2.12bc 0.33± 0.05d 0.19± 0.01d 1.88± 0.02d 0.01± 0.01cd 2.07± 0.1d 0.13± 0.02ad 0.04± 0.02c 0.02± 12.18± 0.02a 2 B 18.75± 0.5b 53.90± 3.55b 3.30± 1.58a 0.72± 0.03c 2.29± 0.14c 0.03± 11.80.± 0.16b 0.01ac 0.09± 0.01b .00b 7.85± 3 C 13.48± 0.5c 40.68± 1.72d 2.88± 0.19c 1.12± 0.07b 2.68± 0.15ab 0.15± 0.02b 25.55.± 0.10± 0.92ab 0.06± 0.01a 10.78.± 4 D 10.92± 0.58d 59.90± 3.94a 3.25± 0.09ab 1.90± 0.16a 2.76± 0.19 ±0.02a 11.40± 0.32c 0.12a 0.12± 0.03a 0.01bc 7.98± 0.01c 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 Physical Characteristics of Selected Clays
Table.4: Mean and Standard Deviation of the Physical characteristic of the selected Clay Sample No Name Bulk density Porosity % C.C.S. kg / cm2 Shrinkage Slag Resistance A IKERE 1.74±0.11d 31.44±0.91a 100±6.21c 5.0±1.23a Good B FAGBOHUN 2.0±0.15a 20.69±1.01bc 140±6.44b 2.0±.00b C ISHAN 2.0±0.02ab 19.10±0.19d 227±12.9a 1.50±0.16bd Poor D ARA 1.99±0.01ac 23.31±0.24b 83±3.24d 1.9±0.1bc 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 Pyrometric Cone Equivalent (PCE)
Table 5 : Result of Refractoriness test on selected Clays Sample No Sample Name Refractoriness Pyrometric Cone Equivalent (PCE) Seger PCE No. Range / Limit Temperature A Ikere Cone 29 > 1500°C High PCE B Fagbohun Cone 16 < Intermediate PCE C Ishan Cone 10 1300°C Low duty PCE D Ara

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 =

46 REACTOR COMPONENTS 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

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

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).

51 For steady state , for heat flow in radial direction and with no heat generation and equation (6) reduces to

52 Integrating equation (7) with boundary conditions of t = t1; at r = r1 and t = t2; at r = r2 the value for temperature distribution‘t’ within the furnace wall becomes: (8) Heat transfer rate is obtained by substituting equation (8) in Fourier’s equation (9) to give equation (10): (9)

53 (10) (11) By integrating equation (10) The Furnace appropriate wall thickness was obtained by substituting equation (5) in (11): (12)

54 Integrating equation (7) with boundary conditions of t = t1; at r = r1 and t = t2; at r = r2 the value for temperature distribution ‘t’ within the furnace wall becomes: Heat transfer rate is obtained by substituting equation (8) in Fourier’s equation (9) to give equation (10): By integrating equation (10)

The Furnace appropriate wall thickness was obtained by substituting equation (5) in (11): DETERMINATION OF THE APPROPRIATE FURNACE WALL THICKNESS: By integrating equation (12) Furnace appropriate wall thickness is determined to be:

56 Furnace is shown in Figure (10) Figure(7)
Fig.10: Reactor’s sections & Modeling


FIG. 12: Furnace with Cover

FIG. 13: Furnace Showing Resistance Elements

The brass crucible is made of m brass plate rolled into an enclosed cylinder and designed to hold averagely about kg of the selected biomass samples for carbonisation at a time in the designed furnace. Length (L) of the crucible is assumed but the densities of the various biomass feedstock ( ) were used to determined the volume of the crucible after experimentation. Average density ( ) = ( ) = ( Average mass ( ) = ) = ) = Volume of cylindrical crucible (

61 Combining equations 14, 15 and 16 the radius of the crucible is determined by equation (17)
(18) The furnace completely envelopes the crucible and supplies its pyrolysis heat through an electrical resistance heater. Heat diffusion to the crucible from the inner surface of the furnace is assumed to have taken place by conduction, since the environment is assumed quiescent and the space between them negligibly small. Heat flux (Q) across the crucible could be analysed by the following equation: (19)

62 FIG. 14: The Fixed- Bed Reactor’s Crucible
BRASS CRUCIBLE FIG. 14: The Fixed- Bed Reactor’s Crucible

FIG. 15: Furnace and Reactor

64 Design of Automatic Control Box
Automatic Control Box: Heat input regulation and temperature / residence time control were achieved through the operation of the designed Automatic Control Box shown on Figure 10 (a & b).

65 Design of Automatic Control Box
Fig .16 A: Control Box Wiring Diagram

66 FIG. 16 (B): Automatic Control Box

67 FIG. 16 (C): Automatic Control Box (Opened)

68 Feedstock selection, sizing and preparation
Materials Sizing: 10 kg each of Apa wood (A. africana), and Iroko wood (M. excelsa) were processed into fine rectangular pin chip particles size of 10 x 10 x 60 mm while Palm kernel shell (E. guineensis), was processed by sieving and utilised as received Moisture removal The materials were subjected to moisture removal in the oven using ASTM: E (ASTM 2006) at 103±2°C for 24 hours and until constant weight was attained per sample after three consecutive measurements.

69 Feedstock selection, sizing and preparation
The free moisture in the samples was therefore completely removed by this process, making them to attain identical moisture free platform. The average moisture totally expelled from the 20 batches per material sample (%) was determined using equation (20). Total expelled moisture content (% wt/wt) = (20)

70 Selected Feedstock Species
(B) A. africana (A) M. excelsa (C) E. guineensis Fig. 17: Sizing of Selected Feedstock for Pyrolysis Experiments

71 Experimentation and Documentation
Carbonisation experiments were carried out at various elevated temperatures for all samples in the developed electrically fired ‘Fixed-Bed Reactor’ at pre-determined temps., ranging from 400°C to 800°C and at 100°C intervals. Fifteen batches (0.5 kg net weight per batch) each of the selected materials of constant moisture content were used as feedstock in 3 replicated experiments

72 Experimentation & Documentation Cont…
By-products of pyrolysis: charcoal (solid fuel), oils (liquid fuel), and pyrogas (non-condensable gaseous products). Experiments were conducted under a quiescent environment (insufficient or complete absence of air). Feedstock residence time, furnace temp. and pyrolysis (reaction) temp. were recorded as displayed on the controllers and recorded every 5 min.

73 Experimental Set-up Fig. 18: Pyrolysis Experimental set-up

74 Assembling the Fixed-Bed Reactor
Fig.19 Assembling the reactor for an Experiment

75 Fig. 20: Fully Assembled Fixed-Bed Reactor with an Ongoing Experiment

76 Exp., Result, Discussion & Analysis
To be continued on Friday ( )


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