Ma Saeed

Improvements to the Hartmann Dust Explosion Equipment for MEC Measurements that Are Compatible with Gas Lean Limit Measurements

Literature results for the MEC of dusts show that the MECs in g/m3 convert to lean equivalence ratios of 0.2–0.3 for many HCO dusts, compared with 0.45 for hydrocarbons and alcohols. This indicates that HCO dusts are more reactive than hydrocarbons, but it could be that it is the measurements of MEC for dusts that are suspect. The measurement of the minimum explosible concentration of dusts is reviewed together with measurement methods for the lean flammability limit of gases. There is considerable uncertainty over the concentration of dusts at the lean limit in the 1 m3 MEC method, as most of the dust injected in the 1 m3 does not burn. It is shown for gases that a vertical tube equipment operated as a closed vessel will give the same lean limit of 0.46O for methane/air as the European standard method, but large spheres will not, and thus, the use of the 1 m3 dust explosion vessel is unlikely to give MEC data that is compatible with lean limits for gases. A study of the MEC of polyethylene dusts was carried out at various ignition delays in the Hartmann, and an ignition delay of 50 ms was recommended for polyethylene dust to give reliable MEC measurements.

Combustion of Pulverized Biomass Crop Residues and Their Explosion Characteristics

ABSTRACT Two Pakistani crop residues, bagasse (B) and wheat straw (WS), both with high ash content, were milled to <63 µm and the ISO 1 m3 explosion equipment was used to investigate flame propagation in the dispersed cloud of pulverized biomass. Their turbulent flame speed, pressure rise, and the Kst (dP/dtmaxV1/3) were measured and comparison was made with two pulverized coal samples. Minimum explosion concentration (MEC) values for B and WS were in terms of the burned dust mass equivalence ratio (Ø) 0.2Ø to 0.3Ø, which was leaner than for the coal samples. These MEC were in good comparison with those previously determined using the Hartmann explosion tube. Peak turbulent flame speeds were 3.8 m/s for B and 3.0 m/s for WS compared with 3.1–5.2 m/s for the two coal samples. The peak Kst was 103 bar m/s for bagasse and 82 bar m/s for wheat straw and the two coal samples had peak Kst of 78 and 120 bar m/s. The peak rise of pressure relative to ambient atmospheric pressure was measured to be 8.8 bar and 8.5 bar for bagasse and wheat straw, respectively. 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.