A novel Ti-based sorbent for reducing ultrafine particulate matter formation during coal combustion

Ultrafine particulate matter (PM) is an important part of PM2.5, which is enriched with hazardous components and more harmful; meanwhile it cannot be effectively removed by the common-used dust collectors. In-furnace sorbent injection is an emerging technology to reduce the emission of PM in the coal combustion and the sorbent is a key factor determining its feasibility. In this study, to seek new PM sorbents, eight minerals were first separately added into a pulverized coal and burned in a drop-tube furnace (DTF) at 1773 K. The derived PM was collected via a Dekati Low pressure impactor (DLPI) sampling system and impacts of each mineral on the PM emission were evaluated. Then, the tested minerals were burned with pure sodium acetate (NaAc) under the same conditions to determine their Na fixation abilities. Finally, the PM reduction mechanism of the sorbent was discussed based on the particle size distribution, mass yield, composition and micromorphology of PM and the chemical and physical properties of the sorbent. A novel Ti-based PM reduction sorbent was screened out, which exhibited an ultrafine PM (PM0.2) reduction efficiency of ∼39% under the experimental conditions at an addition ratio of 5% (wt.%, coal basis). The Ti-based sorbent reacted with Na-contained vapour and formed sodium titanates. Fixation of the Na-contained vapour by the sorbent was considered to be the primary PM capture mechanism. What's more, the high sintering temperature of the Ti-based sorbent facilitates its PM reduction performance. Under the high temperature combustion conditions, the Ti-based sorbent exhibited a good performance in capturing ultrafine PM and Na-contained vapour, indicating its potential of being a high temperature sorbent.