The effects of an additive on the release of potassium in biomass combustion

This study focuses on the effects of an aluminosilicate additive on the fate of potassium during biomass combustion. Such additives have shown some success in mitigating slagging and fouling problems in boilers and furnaces, and the mobility of potassium in combustion systems is one of the key factors dictating ash behaviour. To investigate this, a flame emission spectroscopy technique was used to evaluate the differences in the gas-phase potassium release profiles during the combustion of 5 mm diameter pellets of different biomass suspended in a methane-air flame. The biomass pellets were evaluated with various mixes of an aluminosilicate based additive (5, 15 and 25 wt%). Potassium emission detection, coupled with high speed video of the combustion process, indicated that potassium evolves over the three stages of volatile combustion (a sharp peak in the emission profile), char combustion (a broader peak) and “ash cooking” (a very broad peak over an extended period, long after the end of combustion). In the absence of additive, the three biomass studied (softwood, wheat straw, olive residue) behaved quite differently in terms of potassium release profiles. When the results are normalized for the amount of potassium in the fuel, it is clear that a large fraction of potassium enters the gas phase during the volatile and char combustion of the softwood. Olive residue, releases a lower fraction of potassium during the volatile and char combustion stages, indicating that more potassium is fixed in the ash. In contrast, wheat straw shows a release of potassium during combustion, and then, after a period of “ash cooking”, a substantial gradual release with continued exposure to hot combustion gases. The difference in the emission profiles can be interpreted in terms of the K:Cl ratios and the K:(Si+Al) ratios: high chlorine and/or low (Si+Al) facilitates the release of KCl or KOH to the gas phase, while high (Si+Al) helps to fix K in the solid phase. The addition of the aluminosilicate additive shows a clear reduction in the potassium released from all the biomass pellets, particularly during the char-oxidation and “ash cooking” stages, and the level of additive required is related to the amount of K in the biomass. The potassium emission experiments were complemented by laboratory-scale preparation of ash at different temperatures, and detection of residual potassium in the ash using Atomic Absorption Spectroscopy (AAS). These results validated the findings and quantified the higher fractions of potassium retained within the ash when additives are used. For the wood ash 70-100% of K is retained in the ash in the presence of additive; for the wheat straw, this figure is 60-80% and for the olive pellets it is 70-100%

Deploying the NASA Valkyrie Humanoid for IED Response: An Initial Approach and Evaluation Summary

As part of a feasibility study, this paper shows the NASA Valkyrie humanoid robot performing an end-to-end improvised explosive device (IED) response task. To demonstrate and evaluate robot capabilities, sub-tasks highlight different locomotion, manipulation, and perception requirements: traversing uneven terrain, passing through a narrow passageway, opening a car door, retrieving a suspected IED, and securing the IED in a total containment vessel (TCV). For each sub-task, a description of the technical approach and the hidden challenges that were overcome during development are presented. The discussion of results, which explicitly includes existing limitations, is aimed at motivating continued research and development to enable practical deployment of humanoid robots for IED response. For instance, the data shows that operator pauses contribute to 50\% of the total completion time, which implies that further work is needed on user interfaces for increasing task completion efficiency.Comment: 2019 IEEE-RAS International Conference on Humanoid Robot

Climatic variability over the last 30,000 years recorded in La Piscina de Yuriria, a Central Mexican Crater lake

The Trans-Mexican Volcanic Belt provides an excellent setting for reconstruction of late Quaternary climate from different natural archives. Moreover human impact on the landscape since the mid Holocene provides a good opportunity to investigate the complex interplay of natural and anthropogenic forcing of landscape change. However despite the wealth of records, understanding of the environmental history of the region and its wider significance for climate change across the northern neotropics remains incomplete. We present a radiocarbon-dated, multiple-proxy (sedimentology, sedimentary geochemistry, ostracods, diatoms, stable isotopes) record of climatic and environmental change based on the lacustrine sediments from La Piscina de Yuriria, a hydrologically-closed volcanic crater in the northern TMVB. Much of the last glacial interval was characterised by low effective moisture associated with a weakened North American Monsoon (NAM) although the interval from 30,000 to 27,500 aBP experienced abrupt changes in rainfall. The period corresponding to the late glacial stadial was also dry and the lake may have dried out at this time. There was a change to wetter but variable conditions during the early Holocene as the NAM strengthened. Progressive drying during the later Holocene was accompanied by phases of catchment disturbance, which were partly the result of human impact