The inevitable emission of aerosols during pyrolysis can negatively affect the downstream process and even pollute the environment. In this work, the characteristics of aerosols were investigated during corn stalk pyrolysis at 400–900 °C. The effects of other operation conditions on the aerosol emissions were also probed with online and offline instruments. Results show the yield of aerosol presents a regular change with temperature in a wide range ratio of 3.4–8.7 wt.%. The aerosol size distribution reveals a unimodal form mainly in the 1.1–2.1 μm accumulation range and the maximum emission achieved is about 35 mg/g for SR and SP at 500 °C. Nevertheless, SL gives about 34 mg/g at 600 °C. High temperature promotes the decomposition of polymers into partciles with small diameter (less than PM_1.0). The microtopography of aerosol presents spherical droplets, elongated-like liquid and solid particles that form heterogenous or homogeneous aggregations, that also happen on account of collisions. Aerosols contain mostly organic matter, a small amount of salt and over 50% of volatile organic carbon molecules (VOCs) in the total organic carbon (OC). Proper gas flow, high vapor concentration and longer path way boost the yield of bio-oil and reduce the emission of aerosols. The direct contact is beneficial for adequate extraction, but also causes additional solvent emissions.

The understanding of thermal behaviors of inherent alkali and alkaline earth metals (AAEMs) is significant for the reduction of corrosion and deposition and further utilization of by-products. In this paper, effects of temperature (400–900 °C), retention time and secondary reaction on the release and distribution of AAEMs in products and evolution in the char were systematically investigated during fractional tissues of corn stalk pyrolysis. Results reveal temperature is the crucial factor for AAEMs release and transformation. < 700°C, AAEMs, except Na, was metastable in char. However, ion-exchangeable AAEMs slightly convert by interaction with oxygen-containing active sites. At 900°C, release of AAEMs increased abruptly by the form of salts steam. And spherical or broken bubbles on the molten surface, especially for > 700°C, impenetrate polymer channel and promote the entrainment of AAEMs by aerosol. The enrichment of Si and Al retain them again in the char by the form of acid-soluble and insoluble matter. Compared to char pyrolysis stage, release of AAEMs during devolatilization was lower. Hence, collision probability of AAEMs with oligomers was less likely that leads to inclinable distribution in the aerosol. Simultaneously, longer traveling time-restricted escape from the path of particle clearance.