The effect of steam and sulphur dioxide on CO₂ capture by limestone during calcium looping was studied in a novel lab-scale twin fluidised bed device (Twin Beds – TB). The apparatus consists of two interconnected batch fluidised bed reactors which are connected to each other by a duct permitting a rapid and complete pneumatic transport of the sorbent (limestone) between the reactors. Tests were carried out under typical calcium looping operating conditions with or without the presence of H₂O and/or SO₂ during the carbonation stage. Carbonation was carried out at 650°C in presence of 15% CO₂, 10% steam (when present) and by investigating two SO₂ levels, representative of either raw (1500 ppm) or pre-desulphurised (75 ppm) typical flue gas derived from coal combustion. The sorbent used was a reactive German limestone. Its performance was evaluated in terms of CO₂ capture capacity, sulphur uptake, attrition and fragmentation. Results demonstrated the beneficial effect of H₂O and the detrimental effect of SO₂ on the CO₂ capture capacity. When both species were simultaneously present in the gas, steam was still able to enhance the CO₂ capture capacity even outweighing the negative effect of SO₂ at low SO₂ concentrations. A clear relationship between degrees of Ca carbonation and sulphation was observed. As regards the mechanical properties of the sorbent, both H₂O and SO₂ hardened the particle surface inducing a decrease of the measured attrition rate, that was indeed always very low. Conversely, the fragmentation tendency increased in presence of H₂O and SO₂ most likely due to the augmented internal stresses within the particles. Clear bimodal particle size distributions for in-bed sorbent fragments were observed. Microstructural scanning electron microscope and porosimetric characterisations aided in explaining the observed trends.

在新型实验室规模的双流化床设备（Twin Beds – TB）中研究了蒸汽和二氧化硫对钙环化过程中石灰石捕集CO ₂的影响。该设备由两个相互连接的间歇流化床反应器组成，它们通过导管相互连接，从而允许在反应器之间快速，完全地气动吸附剂（石灰石）输送。在碳酸化阶段中在有或没有H ₂ O和/或SO ₂的情况下，在典型的钙循环操作条件下进行测试。碳酸化反应是在650°C，15％CO ₂和10％蒸汽（如果存在）存在下，通过研究两种SO _{2进行的。}浓度，代表来自煤炭燃烧的原始（1500 ppm）或预脱硫（75 ppm）典型烟气。所用的吸附剂是反应性德国石灰石。根据CO ₂捕集能力，硫吸收，磨损和碎裂来评估其性能。结果证明了H ₂ O的有益作用和SO ₂对CO ₂捕集能力的有害作用。当两种物质同时存在于气体中时，蒸汽仍然能够提高CO _2的捕集能力，甚至抵消了低SO ₂下SO ₂的负面影响。浓度。观察到Ca碳酸化程度与硫酸化程度之间存在明显的关系。关于吸附剂的机械性能，H ₂ O和SO _2均使颗粒表面变硬，从而导致测得的磨损率降低，这实际上总是非常低的。相反，在H ₂ O和SO _2的存在下，碎裂趋势增加的原因很可能是由于颗粒内部的内应力增加。观察到床内吸附剂碎片的清晰的双峰粒度分布。显微结构扫描电子显微镜和孔隙率表征有助于解释观察到的趋势。