Effect of steam exploded treatment on the reactivity of pine wood

A commercial thermally treated biomass process known as ‘steam exploded biomass’ provided the treated biomass samples for this project together with the original yellow pine wood. The aim was to investigate the change in pulverised biomass reactivity. The steam exploded biomass is processed into pellets in the normal way and are known as black pellets (BP). The material was investigated using the Hartmann dust explosibility equipment. This enables the minimum explosion concentration (MEC) to be determined together with the initial rate of pressure rise and the flame speed and these latter parameters are measures of the mixture reactivity. BP was found to have a higher reactivity than the raw biomass with a much leaner MEC. A good correlation was found between the initial rate of pressure rise and the flame speed for the raw wood sample. Surface morphology was performed to investigate the effects of the steam exploded treatment. This showed the enhancement of the proportion of fines. The particle size distribution was determined and this confirmed the enhancement of the fineness of the treated sample. The enhanced reactivity of BP was found to be due to the greater proportion of fine particles which had a higher heating rate and a greater release of volatiles. The steam explosion treatment was found to be an effective pre-treatment in facilitating the combustion of renewable fuel and the main effect was that it was more easily milled, changes in the biomass chemistry was of secondary importance

Burning Properties and Flame Propagation of Varying Size Pulverised Rice Husks

Flame propagation in different size fractions of a rice husk (RH) crop residues were investigated using an ISO 1 m3 dust explosion vessel. This was modified to operate with coarse biomass and for the determination of flame speeds. The flame speed, burning velocity and Kst were found to be greater for the finer fractions compared to the coarser sizes. The MEC were measured at 0.27 equivalence ratio (Ø) for the finest fraction to 1.4Ø for the coarser fraction. The most reactive concentration was measured at lower Ø for fine particles and higher Ø for coarse particles. The maximum Kst for the fine particles was 83 bar m/s and 33 bar m/s for the coarse particles. The size distribution of coarse rice husk particles always has a fine fraction and the flame propagation occurs first in the fine particles, with the coarse particles burning in the hot products of combustion of the fine particles. The fine particle fraction in a coarse mixture has to be flammable and as there is a low proportion of the mixture in the fine fraction, the overall concentration of particles has to increase for the concentration of fines to be flammable. This resulted in the observed lean flammability limit that was richer than stoichiometric for coarse size mixtures

Steam Exploded Pine Wood: The Influence of Particle Size on Mixture Reactivity

Power generation using waste material from the processing of agricultural crops can be a viable biomass energy source. However, there is scant data on their burning properties and this work presents measurements of the minimum explosion concentration (MEC), flame speed, Kst , and peak pressure for pulverised pine wood and steam exploded (black pellets) pine wood. The ISO 1 m3 dust explosion vessel was used, modified to operate on relatively coarse paticles, using a hemispherical dust disperser on the floor of the vessel and an external blast of 20bar compressed air. The pulverized material was sieved into the size fractions <500µm, <63, 63-15-, 150-300, 300-500µm to study the coarse particles used in biomass power generation. The MEC was measured in the range of 0.6-0.85 burnt equivalence ratio, Øburnt,. The measured Kst (25-60 bar m/s) and turbulent flame speeds (~1.5 - 5 m/s) These results show that the steam exploded pine biomass was more reactive than the raw pine, due to the finer particle size for the steam explosed biomass

Flame speed and Kst reactivity data for pulverised corn cobs and peanut shells.

Power generation using waste material from the processing of agricultural crops can be a viable biomass energy source. However, there is scant data on their burning properties and this work presents flame speed and explosion Kst data for two agricultural waste materials: corn cobs and peanut shells. Both parameters were measured on the ISO 1 m3 dust explosion equipment. Two coarse size fractions of corn cobs (CC) and peanut shells (PS) of size less than 500 μm were tested using the Leeds 1 m3 vessel and were compared with two pulverized coal samples. This is typical of the size fraction used in pulverized coal power stations and of pulverized biomass currently used in power generation. The explosion parameters minimum explosive concentration (MEC), rate of pressure rise (dP/dt), deflagration constant (Kst), peak to initial pressure rise (Pm/Pi), turbulent and laminar flame speeds were determined using a calibrated hemispherical disperser in the 1 m3 vessel. MEC were measured in the range of 0.6-0.85 in terms of burnt equivalence ratio, Øburnt, which were comparable to the coal samples. The measured Kst (25-60 bar m/s) and turbulent flame speeds (~1.3 m/s) were lower than for coal, which was a reflection of the lower calorific value. These results showed that these crop residues are technically feasible power plant fuels to burn alongside coal or as a renewable biofuel on their own

Combustion of Pulverized Biomass Crop Residues and Their Explosion Characteristics

Two Pakistani crop residues bagasse (B) and wheat straw (WS), both with high ash content, were milled to <63µm and the ISO 1 m3 explosion equipment was used to investigate flame propagation in the dispersed cloud of pulverised biomass. Their turbulent flame speed was measured and the Kst (dP/dtmaxV1/3) and comparison was made with two pulverised coal samples. Minimum Explosion Concentration (MEC) values for B and WS were, in terms of the burnt dust mass equivalence ratio (Ø) 0.2Ø to 0.3Ø , which was leaner than for the coal samples. These MEC were lower than had previously been determined using the Hartmann explosion tube, and this was considered to be due to the 10 kJ ignition energy in the 1 m3 equipment and 4J spark energy in the Hartmann explosion tube, which extended the lean limit in the 1 m3 equipment. Peak turbulent flame speeds were 3.8 m/s for B and 3.0 m/s for WS compared with 3.5–5.2 m/s for the two coal samples. The peak Kst was 103 bar m/s for bagasse and 80 bar m/s for wheat straw and the two coal samples had peak Kst of 78 and 120 bar m/s. Overall the agricultural biomass and coal samples had a similar range of reactivity. Thus these agricultural crop residues are a viable renewable fuel for co-firing with coal or as 100% biofuel operation of steam power plants

Agricultural Waste Biomass Energy Potential In Pakistan

Pakistan has a major electricity supply problem with urban areas having a very intermittent supply of electricity. The supply gap at periods of high demand is 6 GW. Pakistan has a large agricultural economic sector and produces a substantial amount of waste material that has little current economic use. This work shows that these agricultural wastes are a significant energy resource that could be used to generate electricity using relatively small biomass generator sets that could take all the waste biomass from the surrounding agricultural area. Pakistan currently imports most of the oil used for electricity generation. The cost of this result in high cost electricity and it is shown that bio-electricity could be generated competitively in Pakistan. It was estimated, based on 30% thermal efficiency of electric power generation, that the annual production of crop residues have the potential to generate 76% of the annual electricity requirements of Pakistan. For this to come from agricultural wastes in farmland, transport costs would have to be minimised. It is proposed that a series of about 10MWe plants should be established (which are commercially available) with all farms in about a 10km radius delivering their agricultural solid waste to the plant at the farmers cost with direct payment by the power generator

Explosion and Flame Propagation Properties of Coarse Wood : Raw and Torrefied

A current production torrefaction process was used and the explosion and flame propagation properties were determined at the particle size of the raw (spruce, pine and fir – SPF) and torrefied biomass. The biomass material as received was sieved to <1mm. Size analysis showed that 10% by mass was <100µm and the torrefied sample had 25% <100µm. The CV for the torrefied biomass was 10% greater than that for the raw biomass. The ISO 1 m3 dust explosion vessel was used, with a modified and calibrated biomass dispersion system that could cope with very coarse particles. The explosions did not burn all the dust that was present at the start of the explosion and the residual unburnt dust was shown to be the original dust. The equivalence ratio, Ø, of the propagating flame was based on the burnt dust concentration, Øburnt. Raw and torrefied samples were found to have minimum explosion concentrations, MEC, of 2.3Øburnt and 1.4Øburnt respectively and this shows that the torrefied sample was more reactive as it had a leaner MEC. The deflagration index, Kst, was higher for the torrefied SPF with a peak at 35 bar m/s compared with 24 for the raw biomass. The peak turbulent flame speeds were similar for torrefied and raw biomass at about 1 m/s. The torrefied biomass was more reactive than the raw biomass mainly due to the smaller particles size and 10% higher CV. The mechanism for coarse particle combustion is considered to be due to the explosion induced wind blowing the finer fractions ahead of the flame which burn first with the coarser fractions gasifying in the rich burnt gases behind the initial flame. The rich MEC was caused by the requirement to have the fine fraction above the MEC when only about 10% of the mixture was fine

Flame Propagation of Pulverised Biomass Crop Residues and their Explosion Characteristics

Pulverised agricultural crop residues were investigated using the ISO 1 m3 turbulent explosion vessel. This was modified to enable the spherical flame propagation flame speed and the heat release rate in MW/m2 to be determined. From the turbulent flame speed, the laminar flame speed and laminar burning velocity and global heat release, MW/m2, were determined. In addition the equipment was used to determine the biomass explosibility, Kst (= dP/dtmaxV1/3), and the minimum explosion concentration (MEC). Two Pakistani crop residues bagasse (B) and wheat straw (WS) were investigated. Particle size distribution, elemental and proximate analysis and surface morphology for the raw powders and for their post explosion residues were carried out. It was found that these crop residues have explosibility characteristics comparable to wood biomass powders. MEC values as low as equivalence ratios of 0.18 to 0.3 were found which were lower than for gaseous hydrocarbons, but similar to other measurements for biomass using the Hartmann explosibility equipment. Peak turbulent flame speeds were measured at 3-4 m/s. There was a significant post explosion residue of unburned material which was shown to have an increase in char content relative to the raw biomass, while the volatile content was reduced. The BET surface area of the post explosion residue of bagasse was higher than that of the wheat straw residue, showing a higher release of volatiles for bagasse with a more porous char residue in the burnout indicating higher reactivity. These crop residues are a viable renewable fuel for existing coal power plants or as a basis for a new generation of small scale steam power generators in Pakistan

Turnip mosaic potyvirus probably first spread to Eurasian brassica crops from wild orchids about 1000 years ago

Turnip mosaic potyvirus (TuMV) is probably the most widespread and damaging virus that infects cultivated brassicas worldwide. Previous work has indicated that the virus originated in western Eurasia, with all of its closest relatives being viruses of monocotyledonous plants. Here we report that we have identified a sister lineage of TuMV-like potyviruses (TuMV-OM) from European orchids. The isolates of TuMV-OM form a monophyletic sister lineage to the brassica-infecting TuMVs (TuMV-BIs), and are nested within a clade of monocotyledon-infecting viruses. Extensive host-range tests showed that all of the TuMV-OMs are biologically similar to, but distinct from, TuMV-BIs and do not readily infect brassicas. We conclude that it is more likely that TuMV evolved from a TuMV-OM-like ancestor than the reverse. We did Bayesian coalescent analyses using a combination of novel and published sequence data from four TuMV genes [helper component-proteinase protein (HC-Pro), protein 3(P3), nuclear inclusion b protein (NIb), and coat protein (CP)]. Three genes (HC-Pro, P3, and NIb), but not the CP gene, gave results indicating that the TuMV-BI viruses diverged from TuMV-OMs around 1000 years ago. Only 150 years later, the four lineages of the present global population of TuMV-BIs diverged from one another. These dates are congruent with historical records of the spread of agriculture in Western Europe. From about 1200 years ago, there was a warming of the climate, and agriculture and the human population of the region greatly increased. Farming replaced woodlands, fostering viruses and aphid vectors that could invade the crops, which included several brassica cultivars and weeds. Later, starting 500 years ago, inter-continental maritime trade probably spread the TuMV-BIs to the remainder of the world