Carlos Alberto Luengo

Wood briquette torrefaction

Several torrefaction experiments using wood briquettes are reported in this paper. The torrefied briquettes weight yield lies between 43 and 94 %, and energy yields ranged from 50 to 97 % depending on the operating parameters. After torrefaction the briquettes showed an increase of approximately 15 % in heating value, and a decrease of approximately 73 % in equilibrium moisture. It was shown that torrefied briquettes achieved hydrophobic character and remained unaffected when immersed in water. This research also provides information on proximate and elemental analysis, showing that temperature has more influence than residence time. The aforementioned data indicate that torrefaction is a feasible alternative to improve energy properties of ordinary briquettes and prevent moisture absorption during storage.

The scope for generating bio-oils with relatively low oxygen contents via hydropyrolysis

Abstract The primary oils obtained in high yields from fast (fluidised-bed) pyrolysis of biomass generally have high oxygen contents (ca. 40% w/w). The scope for using pyrolysis under hydrogen pressure (hydropyrolysis), to give oils with much lower oxygen contents compared to normal pyrolysis has been investigated. Fixed-bed hydropyrolysis tests have been conducted on cellulose, sugar cane bagasse and eucalyptus wood using hydrogen pressures up to 10 MPa, with heating rates of 5 and 300°C min −1 . A colloidal FeS catalyst was used in some tests (Fe loading of 5%, w/w) to increase overall conversions. Further, the attractive option of using a two-stage reactor in which the primary oil vapors are passed though a bed of hydrotreating catalyst is also described. Raising the hydrogen pressure from atmospheric to 10 MPa reduced the oxygen content of the primary oil by over 10% to below 20% w/w. The addition of a dispersed iron sulphide catalyst gave conversions close to 100% for all three biomass samples investigated at 10 MPa under conditions in the fixed-bed reactor where significant diffusional resistances existed and reduced the oxygen content of the bio-oil by a further 10%. Although NMR indicated that the oils became increasingly aromatic as more oxygen was removed, the increase in hydrogen pressure decreased the extent of overall aromatisation that occurs primarily due to the lower char yields obtained. In two-stage tests for cellulose, using a commercial sulphided Ni/Mo γ-Al 2 O 3 catalyst at 400°C, increasing the hydrogen pressure from 2.5 to 10 MPa decreased the oxygen content of the oil by over 20% to 10% w/w. The H/C ratios were higher and O/C ratios smaller for the two-stage bio-oils compared to their single stage counterparts. However, the differences in the O/C ratios between the single and two-stage bio-oils increase with pressure.

Applications of a granular model and percolation theory to the electrical resistivity of heat treated endocarp of babassu nut

Abstract The volume fraction, X, of the conducting phase in a granular structure defined in the carbon matrix and applicable to heat treated biomass carbons is calculated as a function of structural parameters obtained from X-ray diffraction and small angle X-ray scattering measurements. The room temperature electrical resistivity of heat treated endocarp of babassu nut with heat treatment temperatures up to 2200°C is thus presented as a function of X. The drop of twelve orders of magnitude in the resistivity is explained as a percolation transition in the granular structure, X being the fundamental parameter. The electronic conduction process occurs in this structure with the involvement of microcrystallites and micropores.

Babassu charcoal: A sulfurless renewable thermo-reducing feedstock for steelmaking

Abstract The physical and chemical properties of babassu coconut following heat treatment at temperatures of up to 1000°C are reported. Results for compressive strength, density, granulometry, heat of combustion and ash content suggest that babassu charcoal from unbroken coconuts could be used as a substitute for metallurgical coke as a reducing agent in blast furnaces. This material is one of the few which could substitute directly metallurgical coke in high capacity blast furnaces without the need for briquetting.

A novel catalyst system for ethanol gasification

Nickel/copper/chromium catalysts supported on porous alumina were synthesized. Samples of 4.0% Ni/0.75% Cu/0.25% Cr on α-Al2O3 were run in a fixed-bed reactor system dedicated to the steam reforming of ethanol. The operating temperatures ranged from 573 to 823 K, the water/ethanol mole ratios from 0.4 to 2.0 and the space velocities from 2.5 to 15 h−1. The data reveal high activity of this catalyst for ethanol gasification, as well as good selectivity in H2 and CO. Comparison of these results with thermodynamic equilibrium values indicate that the catalytic effect is more pronounced at lower temperatures.

Preparing and characterizing biocarbon electrodes

Abstract In this research, eucalyptus wood is used as a source of coke (charcoal) and pitch (biopitch) feedstocks for the production of graphite-like materials. The wood process starts with batch pyrolysis of Eucalyptus saligna wood samples heated up to 1000°C under a heating rate of 3°C min −1 . Volatiles are condensed to originate an organic tar (bio-oil), and later distilled to recover heavier fractions that are used as a binder in the electrodes manufacture. The solid charcoal is ground and compressed together with biopitch. The pre-molded green electrode has a 25-mm diameter and 120-mm length. It is read to be cured in an increasing temperature treatment. The next step is the calcination at 1000°C, followed by graphitization at 2700°C. The material presented a turbostratic structure, which is monitored by X-ray diffraction (XRD), and the line widths of (002) and (100) lines indicate values of L c =12.4 nm and L a =56.5 nm. The electrical resistivity of the biocarbon samples, treated at heat temperatures (HTTs) higher than 900°C, presented values of 10 −4 Ω m. Compression tests indicate that Youngs modulus has a maximum of 3.0 GPa at HTT of 1000°C. The rupture strength also goes through a maximum of 50 MPa at similar HTT. Thermal expansion measurements indicate a linear coefficient of 6.10 −6 °C −1 for the samples heat-treated at 2700°C. In this work, a comparison between the biocarbon electrode (BCE) and a traditional electrode from coal and petroleum derivatives is made. We found out that an ordinary electrode used to scratch furnace has comparable properties to BCE. The main purpose of this research is to prove that electrodes can be made from renewable sources and, in this way, decrease pollutant in the industrial process.

Thermochemical Properties of Cuban Biomass

This study provides information on proximate analysis, heating values, and ultimate analysis for seven kinds of biomass from agriculture and forest sources, such as rice husk, coffee husk, sugar cane bagasse and straw, and firewood. The results have shown excessive volatile content ranging from 61.2% to 82.6%, fixed carbon content ranging from 14.6% to 20.7%, and high ash contents over 22.5% for rice husk and 9.3% for sugar cane straw. Other biomass studied did not reach 3%. The lower heating values ranged from 15.2 to 21.2 MJ/kg (dry weight basis), with firewood presenting higher values. The ultimate analysis indicated that the weight fraction of carbon ranged from 38.2% to 48.8%, the hydrogen fraction ranged from 5.6% to 7.0%, and the oxygen fraction ranged from 33.8% to 43.7%. Estimates have indicated that the energy potential of agricultural residues is around 366,700 tonnes of oil annually, which is almost 25% of the cuban annual crude oil production.This study provides information on proximate analysis, heating values, and ultimate analysis for seven kinds of biomass from agriculture and forest sources, such as rice husk, coffee husk, sugar cane bagasse and straw, and firewood. The results have shown excessive volatile content ranging from 61.2% to 82.6%, fixed carbon content ranging from 14.6% to 20.7%, and high ash contents over 22.5% for rice husk and 9.3% for sugar cane straw. Other biomass studied did not reach 3%. The lower heating values ranged from 15.2 to 21.2 MJ/kg (dry weight basis), with firewood presenting higher values. The ultimate analysis indicated that the weight fraction of carbon ranged from 38.2% to 48.8%, the hydrogen fraction ranged from 5.6% to 7.0%, and the oxygen fraction ranged from 33.8% to 43.7%. Estimates have indicated that the energy potential of agricultural residues is around 366,700 tonnes of oil annually, which is almost 25% of the cuban annual crude oil production.

Microscopic structure and electrical properties of heat treated coals and eucalyptus charcoal

Abstract The essential parameter governing the conduction process of coal under heat treatment in the range 500–800°C is the volume fraction of the graphitic particles distributed among microvoids. Combining the activated conduction description with percolation, we have obtained the effective barrier height for tunneling between grains which is independent of the volume fraction. Thus all dependence on the heat treatment temperature have been reduced to a single parameter, the volume fraction.

A case study of compact cogeneration using various fuels

A method for studying the technical and economic feasibility of absorption refrigeration systems in compact cogenerators is presented. The system studied consists of an internal combustion engine, an electric generator and a heat exchanger to recover residual heat from the refrigeration water and exhaust gases. As an application, a computer program simulates the cogeneration system in a building which already has 75 kW of installed electric power. The maximum electric and refrigeration demands are 45 kW and 76 kW respectively. This study simulates the system performance, utilizing diesel oil, sugar cane alcohol and natural gas as possible fuels.

Hydrodeoxygenation of oils from cellulose in single and two-stage hydropyrolysis

To investigate the removal of oxygen (hydrodeoxygenation) during the hydropyrolysis of cellulose, single and two-stage experiments on pure cellulose have been carried out using hydrogen pressures up to 10 MPa and temperatures over the range 300–520°C. Carbon, oxygen and aromaticity balances have been determined from the product yields and compositions. For the two-stage tests, the primary oils were passed through a bed of commercial Ni/Mo γ-alumina-supported catalyst (Criterion 424, presulphided) at 400°C. Raising the hydrogen pressure from atmospheric to 10 MPa increased the carbon conversion by 10 mole % which was roughly equally divided between the oil and hydrocarbon gases. The oxygen content of the primary oil was reduced by over 10% to below 20% w/w. The addition of a dispersed iron sulphide catalyst further increased the oil yield at 10 MPa and reduces the oxygen content of the oil by a further 10%. The effect of hydrogen pressure on oil yields was most pronounced at low flow rates where it is beneficial in helping to overcome diffusional resistances. Unlike the dispersed iron sulphide in the first stage, the use of the Ni-Mo catalyst in the second stage reduced both the oxygen content and aromaticity of the oils.