Krister Sjöström

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.

Use of amino phase adsorbent for biomass tar sampling and separation

Abstract To reduce sampling and sample separation time, a highly efficient method based on solid-phase adsorption (s.p.a.) on amino phase was designed. This method is suitable for intermittent trapping of tar compounds ranging from benzene to coronene prevailing in product gases from thermal decomposition of biomass at 700–1000°C. Using eluotropic elution, adsorbates are selectively desorbed into aromatic and phenolic fractions and then determined by gas chromatography with flame-ionization detection. The sampling step allows collection of one to three samples per minute, compared with one or two samples per hour using conventional cold trapping (c.t.) techniques, and correspondingly more information is obtained. As a result of this improvement, the progress of pyrolysis and gasification processes in terms of molecular distribution is easily followed. Furthermore, the method can be readily applied to establish cold-trap and filter performance and for industrial emission control. The usefulness of the method is compared with the cold-trapping techniques and the novel solid-phase micro extraction (s.p.m.e.) technique, not tested earlier for tar sampling.

Tar evolution profiles obtained from gasification of biomass and coal

The tar content of the product gases from gasification of biomass is one of the major factors affecting the subsequent process stages. In this work, evolution profiles of the main tar constituents, ...

Promoted reactivity of char in co-gasification of biomass and coal: synergies in the thermochemical process

An experimental study on co-gasification of woody biomass and coal in oxygen-containing atmosphere was carried out in a pressurized fluidized bed reactor. The wood used was birch from a Swedish paper mill, while the coals used were Daw Mill coal of UK origin and a bituminous coal from Poland. The operation temperatures were 900 and 700°C, and the pressure was 0.4 MPa. The ratio of coal to wood was varied in the investigation. The study was focused on possible synergetic effects in the thermochemical treatment of the fuels. The char formed was examined. The tar produced in the process was analyzed. The nitrogen compounds emitted were detected. A noticeable phenomenon was that the mixtures of the fuels and their char formed in situ demonstrated an unexpected high reaction rate of gasification under the studied conditions. The yield of char diminished and consequently the production of gas increased. Further, both the formations of tar and nitrogen compounds also seemed affected synergetically in the co-gasification experiments of the fuels. The yields of tar and of ammonia were lower than expected.

Characteristics of evolution of tar from wood pyrolysis in a fixed-bed reactor

The thermally induced interrelation between total tar, chemical distribution of principal tar constituents and the three C2 compounds (ethane, ethene, ethyne) obtained from wood pyrolysis at atmospheric pressure in a continuous bench-scale fixed bed reactor was investigated. Total tar and certain tar constituents exhibit a close correlation with the C2 compounds over the temperature range 700–900°C. Some characteristic compound ratios, namely indene to naphthalene (IN), phenols to aromatics (PA) and saturated to unsaturated C2 compounds, were identified. These reactor-specific correlations have obvious potential application for on-line continuous monitoring of non-gaseous products that so far are determined off-line. The analysis methods used were designed for quantification of aromatics, phenols, N-organics, asphaltenes and preasphaltenes.

Provisional protocol for the sampling and anlaysis of tar and particulates in the gas from large-scale biomass gasifiers. Version 1998

Abstract This paper presents tar sampling protocols for pressurised and atmospheric large scale gasification processes. Methods for constructing sampling lines either to on-line analysers or into sampling systems are described. The tar sampling system consists of a heated probe, a particulate filter and a series of impinger bottles. Dichloromethane is used as the tar abosrbing solvent. The solvent containing bottles are placed in a cold bath so that gradual cooling of the sampled gas from about 0°C to the final temperature −79°C takes place in them. Recommendations for suitable sampling gas flow rates and gas temperatures are given. Tar characterisation methods based on different garvimetric measurements and GC analysis are described.

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.

Reactivity of char from pyrolysis of birch wood

Abstract Pyrolysis of biomass from birch was carried out both in a free-fall tubular reactor and a thermobalance. The char obtained was further gasified with carbon dioxide and steam in the thermobalance. It was observed that the reaction rates of the char with the reagents were strongly affected by the time-temperature history of the char formation. A rapid heating rate of the raw material in free-fall reactor gives a char which possesses higher reactivity in reaction both with carbon dioxide and steam compared with the char formed under slow heating rate in the thermobalance. The treatment condition and environment of the char precursor during devolatilization are the most important factors affecting the reactivity of the char in gasification with the used reagents. The kinetic study focused on whether a surrounding pyrolysis gas atmosphere exerts negative effects on the reactivity of the formed char.

Decomposed Methanol as a Fuel—A review

Abstract The use of decomposed methanol, i.e., hydrogen and carbon monoxide, in spark-ignition engines is reviewed. The emphasis is on onboard decomposition and the paper docs not deal with engines fueled by stored hydrogen. The paper concentrates mostly on the experimental work performed using catalytically decomposed methanol, where the methanol is used as a hydrogen carrier. The greatest potential for this type of engine, besides the low energy consumption, lies in the low emissions of nitrogen oxides when running at lean air/fuel ratios. An active and selective catalyst for the decomposition reaction is essential for the utilization of this concept. A literature review on catalyst investigations is included. Neat methanol engines arc not readily started at low ambient temperatures. The possibility of using decomposed methanol as a cold start fuel for methanol engines is reviewed. Decomposed methanol has been proposed as a fuel for gas turbines. A brief review of this subject is also included.