Emissions and deposit properties from combustion of wood pellet with magnesium additives

This work studies the amount of gaseous and particle emissions and deposits on heat exchanger surfaces in a boiler firedwith commercially available pellets and with pellets primed with magnesium oxide and magnesium hydroxide.The combustionexperiments were performed on a residential boiler of 20 kW.Substrates placed in the heat exchanger was analysed with SEM-EDX-mapping to evaluate the chemical composition of the deposits.The results show that particle emissions(PM 2.5)using the additivesincreased by about 50%and the mass of the deposits in the flue gas heat exchanger(excluding loose fly ash)increased by about25%compared to the combustion of pellets without additives.The amount of additives was found to be eight times higher than theamount of the main alkali metals potassium(K)and sodium(Na)which leads to the assumption that the additives were overdosedand therefore caused the problems reported.The SEM analysis of the substrates placed in the flue gas heat exchanger indicate that thedeposits of sodium(Na),potassium(K),chlorine(Cl)and sulphur(S)decrease using the additives.If this was due to theexpected chemical reactions or due to the loose fly ash covering the substrates after the test,could not be determined in this study.

西伯利亚苔原对大陆架海域和北冰洋环境的影响

"94’苔原生态"考察队研究了河流输入到大陆架海域的无机和有机碳及其在海水和沉积物中的生物化学转化。另外,还研究了水和沉积物中的人为放射性核物质、^(137)Cs、^(90)Sr和^(239.240)Pu 。溶解的无机碳的分布表明鄂毕河和叶尼塞河大部分的径流进入北冰洋中心之前都经过了拉普捷夫海。沉积物研究表明不同位置海底氧的吸收、溶解无机碳和养分的迁移都具有明显的差异。切尔诺贝利事故泄漏的^(137)Cs的活动有30%分布在巴伦支海、喀拉海和拉普捷夫海。巴伦支海的^(137)Cs增加了5～8Bq/m^3,喀拉海增加了5～13Bq/m^3,拉普捷夫海增加了8～15Bq/m^3,但在河口出现局部的低浓度。^(90)Sr值也相应地达到2.5,3和4Bq/m^3。