Abstract. A semi-mobile torrefaction and densification pilot plant was constructed in order to determine ideal operating conditions and evaluate briquette quality and throughput rate using forest residuals as the input feedstock. Experiments were conducted at various conditions with feedstock moisture content ranging from 4% to 25% (wet basis), reactor residence times of 10 and 20 min, and final product temperatures between 214°C and 324°C. Optimal operating conditions, evaluated based on throughput rate, specific electricity demand, torrefied briquette grindability, briquette volumetric energy density, and briquette durability, were identified to occur with a short residence time (10 min), low feedstock moisture content (<11% wet basis), and high final product temperature between 267°C and 275°C. These conditions were able to process 510 to 680 kg h-1 (wet basis) feedstock with a dry mass yield of 79% to 84% to produce torrefied biomass with a higher heating value of 21.2 to 23.0 MJ kg-1 (dry basis) compared to 19.6 MJ kg-1 for the original biomass. Torrefied briquettes produced at these conditions had a neatly stacked packing density of 990 kg m-3 and a volumetric energy density of 21,800 MJ m-3. Their specific grinding energy was an average 37% of the energy required to grind a raw biomass briquette. These torrefied briquettes were more durable (94% DU) than raw briquettes (85% DU) directly following production, but were less durable after undergoing temperature and humidity fluctuations associated with long distance transportation (74% DU for torrefied and 84% DU for raw biomass briquettes). Results from this pilot plant are promising for commercial scale production of high quality torrefied briquettes and should lead to additional research and development of a torrefaction system optimized for a higher throughput rate at these conditions. Keywords: Biomass, Biomass conversion technology, Bioenergy, Briquetting, Densification, Forest residuals, Pyrolysis, Torrefaction.
ABSTRACT. Two commercial biochar production machines -a single-auger unit and a larger dual-auger version
ABSTRACT. An All Power Labs PP20 gasifier generation set (Berkeley, Calif.) any promising technologies are emerging for the conversion of residual forest waste to useful products. These processes are collectively known as biomass conversion technologies (BCTs) and include processes such as torrefaction, densification, and biochar production. However, the feasibility of BCT projects is highly dependent on the transportation economics of the unprocessed waste biomass (Pan et al., 2008). From a transportation economics standpoint, it is often optimal to place a BCT operation as close to the fuel source as possible. Examples include forest landing sites, at the roadside, or in locations close to forestry operations, such as former sawmills. Although optimal for transportation costs, technological and logistical challenges arise when operating a BCT in remote locations. A key logistical factor for BCT operation is obtaining a reliable source of electricity. Many potential sites do not have access to grid electricity, and a remote power source is therefore required to provide electricity to the BCT. BACKROUNDIn a previous study by Severy et al. (2016), various remote power generation technologies were compared for their potential feasibility for providing power at a remote forest landing site. The technologies evaluated in this study were an organic Rankine cycle (ORC) waste heat recovery device, a thermoelectric generator, a biomass gasifier with an engine generator (All Power Labs Power Pallet, Berkeley, Calif.), a solar PV array with battery storage, and a shaft work power generator. The generation sources were evaluated based on their mobility, footprint, reliability, operational intensity, electrical load following ability, environmental impact, capital cost, operational cost safety, and ease of permitting. The results of the technoeconomic feasibility study concluded that a biomass gasifier was the preferred alternative technology to replace a diesel generator at a BCT site due to its mobility, small footprint, competitive lifecycle cost, and quoted load following abilities (Severy et al., 2016). To validate the results of the feasibility study and extend research on the topic, the goal of this study is to evaluate the suitability of the APL PP20 for powering biomass conversion technologies in the greater Pacific Northwest area. The objectives are to measure the power output and load following capabilities, quantify the emission rates, and provide electricity to a remote BCT that has a fluctuating load. By conducting these tests, the authors can verify whether this gasifier generator is a technically-viable alternative to a diesel generator at offgrid locations. GASIFIER AS AN ELECTRICAL POWER SOURCEGasification technology has been used for decades (Ghosh et al., 2006). However, due to relatively recent technology improvements, there has been an increase in development and interest in the technology. Ahrenfeldt et al. (2013) review the state of the art of biomass gasification combined heat and power (CHP) syst...
Floating offshore wind is being considered in northern California as indicated by the Bureau of Ocean Energy Management’s issuance of a lease consideration in the Humboldt Call Area. Humboldt County offers access to this enormous resource, but local electric load and transmission are limited. The potential impacts of offshore wind generators at three different scales were studied using a regional grid model of Humboldt County. Offshore wind generation was calculated using modeled wind speed data and 12-MW turbine specifications and integrated with projected load and historical generation. Offshore wind farms deployed in the Humboldt Call Area achieve annual capacity factors between 45% and 54% after losses and maintenance. Power output is variable between and within seasons, with full power output 30% of the time and no output approximately 20% of the time. Electricity from a 48-MW wind farm provides 22% of regional load with limited exports. A 144-MW wind farm serves 38% of local load, exporting 40% of its electricity with the extant 70-MW transmission capacity. A full build-out of 1836 MW would result in 88% curtailment with existing transmission. Across scenarios, offshore wind variability necessitates reliance on existing power plants to meet local demand in periods of low wind.
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