Emilia Björnbom

Rapid pyrolysis of agricultural residues at high temperature

This paper deals with rapid pyrolysis of agricultural residues such as olive waste and straw at high temperature (800 -1000degreesC) in a free-fall reactor at pilot scale. The conditions are of int ...

Rapid high-temperature pyrolysis of biomass in a free-fall reactor

Rapid pyrolysis of biomass, wood and agricultural residues was studied using a free-fall reactor with which the effects of heating rate, temperature, particle size and residence time on the product distribution, gas composition and char reactivity could be determined. Interest was focused on the effect of the rapid pyrolysis conditions on the reactivity of the char. Formation of low yields of char with high reactivity is desirable in both gasification and combustion. The reactivity of char obtained in pyrolysis of biomass is very strongly influenced by the treatment conditions and may be significantly increased by using high heating rates, small particle size of the fuel and short residence time at higher temperature.

Mixed manganese oxide/platinum catalysts for total oxidation of model gas from wood boilers

Abstract Mixed manganese oxide/platinum catalysts in the form of monoliths have been prepared by the deposition-precipitation method. The influence of the platinum content and the calcination temperature has been investigated by activity measurements for total oxidation of methane, naphthalene and carbon monoxide in the presence of steam and carbon dioxide, and by the temperature programmed reduction (TPR) technique. Manganese oxide behavior is influenced by the presence of even very small amounts of platinum especially when the catalyst is calcined at a higher temperature due to favorable synergetic effects.

Total oxidation catalysts based on manganese or copper oxides and platinum or palladium I: Characterisation

Abstract Temperature-programmed reduction (TPR), oxidation (TPO), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to characterise catalysts based on manganese oxides, copper oxides or one of them mixed with platinum or palladium-supported on γ-alumina. The catalysts were characterised before and after they had been exposed either to high temperature in the presence of steam or to sulphur dioxide. Raman spectroscopy, XRD, XPS and TPR performed on the fresh samples of MnO x , mixed MnO x –Pt and MnO x –Pd revealed the presence of a mixture of manganese oxides, particularly Mn 2 O 3 . In the fresh mixed MnO x –Pd and CuO x –Pd samples, Pd catalysed the reduction of both MnO x and CuO x , whereas Pt only catalysed the reduction of MnO x . After hydrothermal treatment at 900°C of the MnO x , mixed MnO x –Pt and MnO x –Pd samples, there was a formation of new manganese oxide phase, Mn 3 O 4 detected by Raman spectroscopy. TPR revealed increasing interaction between the metal oxides and the noble metals in the hydrothermally treated mixed MnO x –Pd and CuO x –Pd samples, and also the appearance of interaction in the treated mixed CuO x –Pt sample. The sulphur adsorbed in all the MnO x samples formed sulphate, which was more difficult to reduce than the oxides. Also, the reduction temperature of sulphates was lowered when noble metals are present.

Effect of water vapour and biomass nature on the yield and quality of the pyrolysis products from biomass

Slow pyrolysis/activation of biomass in a flow of steam is studied in laboratory equipment supplied with a fixed bed reactor. Forestry and agricultural residues of different origin are selected as ...

Thermochemical treatment of biomass in a flow of steam or in a mixture of steam and carbon dioxide

Simultaneous pyrolysis and gasification of biomass samples of different origin is performed in a flow of steam or in a mixture of steam and carbon dioxide. Wastes from birch wood, olive stones, bag ...

Catalytic tar decomposition of biomass pyrolysis gas with a combination of dolomite and silica

Abstract In this study the catalytic effects of dolomite and silica on biomass tar decomposition were investigated. The concentration of naphthalene is of particular interest since it is the most difficult compound to decompose when dolomite is used as catalyst. The two catalysts were tested in different combinations to see whether synergetic effects on the cracking of naphthalene could be found. Thermal and catalytic cracking were carried out at 700–900°C under ambient pressure in a fixed bed reactor using a tar-rich gas obtained from pyrolysis of different biomass materials. Characterisation of light components of tars using the solid phase adsorption method was also performed. Experimental results indicate that when a pure silica is placed in a layer above the dolomite, considerably less naphthalene and total light tar remains after cracking.

Thermal stability of metal-supported catalysts for reduction of cold-start emissions in a wood-fired domestic boiler

The aim of the present work is to develop a catalyst based on a mixture of manganese oxides and platinum supported on a metallic monolith for abatement of emissions from wood combustion, particularly during the cold-start phase. The activity and the thermal stability of the catalysts have been studied in the laboratory, before performing tests in a wood-stove. The effect of the hydrothermal treatment at 900°C on the adherence of the washcoat onto a metallic substrate was studied using scanning electronic microscope. It revealed well-adhering washcoat onto the metallic support due to the growth of the alumina whiskers during the treatment. The influence of the amount of washcoat, as well as the influence of the concentration of manganese oxides in it (Mn: 5 to 20 mol%/Al2O3) on the activity of fresh and hydrothermally-treated catalysts were studied. The activity tests were carried out using a mixture of carbon monoxide, naphthalene and methane in the presence of air, steam and carbon dioxide to resemble the flue gases from wood combustion. On the fresh catalysts, containing the same total amount of manganese, a high concentration of manganese oxides in the washcoat favoured the oxidation of carbon monoxide and naphthalene, whereas a lower concentration of manganese oxides in the washcoat gave higher activity for the oxidation of methane. An increased total amount of manganese oxides in the catalysts, which had the same amount of washcoat, resulted in an increase in activity for the oxidation of the three combustibles. After thermal treatment at 900°C for 270 h in steam, most of the manganese oxide catalysts were activated for the oxidation of carbon monoxide and naphthalene while only being slightly deactivated for the oxidation of methane. The addition of manganese oxides in the washcoat, however, lowers the temperature of the γ- to α-alumina phase transformation. Platinum (0.5 mol%) was added to the manganese oxide (10 mol%) catalyst to improve its activity. A platinum catalyst was also tested for comparison. The platinum and the mixed catalysts showed similar activity for the oxidation of carbon monoxide and naphthalene, while the mixed catalysts were more active for the oxidation of methane. A similarly mixed MnOx–Pt (10–0.5 mol%) catalyst supported on Al2O3 stabilised with 3% lanthanum, but at larger scale, was tested in a wood-stove. The possibility of pre-heating the catalyst during the start-up phase was studied. The tests revealed a strong decrease of the carbon monoxide and unburned hydrocarbons emissions during the start-up phase when the catalyst was pre-heated with hot air compared with no pre-heating or no catalyst.

Material losses in liquefaction of raw peat with carbon monoxide

The loss of organic material into the aqueous and gas phases in the liquefaction of raw peat with ≈ 90 wt% moisture content has been studied. The raw material was treated with CO at an initial pressure of 5.5–8.3 MPa and a temperature of 300–350 °C in the presence of K2CO3. The yield of water, water-soluble and gas products depended on the operating conditions and the chosen input material. In the liquefaction of peat with 31 wt% oxygen content the loss of material into the aqueous and gas phases decreased with increases in the initial CO pressure and the reaction temperature. The loss of organic material from peat with a high oxygen content (≈ 40 wt%) was significant. This loss of organic material is a result of thermal decomposition and hydrolysis of the organic matter of the peat and elimination of low molecular weight gases and water-soluble compounds with high oxygen and low energy contents. The selective transfer of highly oxygenated components from the peat resulted in the formation of liquid and solid residual materials with low oxygen and high energy contents. Most of the energy content of the peat becomes concentrated in the liquid and solid products (toluene- or acetone-solubles and -insolubles). The loss of organic material from the peat into the aqueous and gas phases is not accompanied by significant energy losses from the raw material.

Some criteria for the selection of peat as a raw material for liquefaction

Abstract This work compares some of the characteristic properties of peat, such as the degree of humification, calorific value and oxygen content of the organic matter, as criteria for selection of peat for liquefaction. It shows the priority of the calorific value over the currently used degree of humification as a criterion.