Study Of Deposition And Distribution Characteristics Of Particles Derived From Refining And Chemical Wastewater Incineration

High-salt organic wastewater with high toxicity and poor biodegradability is derived from petrochemical, metallurgy and pharmaceutical industry, and brings huge harm to human health and ecology environment. Thermo-chemical conversion method, such as incineration, is a common and well-established method of waste liquid treatment, which can achieve a certain purpose that the harmful material is completely destroyed and the heat is recycled efficiently. The adverse effects of deposition, such as fly ash bridge, thermal efficiency loss, high temperature corrosion and wear of heat exchange components, influence the security and economy of heat recovery steam generators (HRSGs) directly.In this paper, characteristics of migration, distribution, deposition of ash particles, heat transfer and pressure drop have been numerically investigated, the main conclusions are as follows:(1) Gas-solid two-phase flow and heat transfer mathematical models have been established, melting fraction curves of ash particles rich in alkali salts have been calculated by using thermodynamic equilibrium software FactSage. Critical velocity coupled with melting curve adhesion model has been used to predict the fates of ash particles impacting on the heat transfer surfaces along the flue gas flow, and the rationality and correctness of models have been verified by the filed measurement data. Mountain-like ash deposits formed by large size particles are focused on the range of-60 to 60 degrees of windward side of pipes only, while-50 to 50 degrees for micro-sized particles on the windward sides and a uniform distribution of deposits on the leeward sides; submicron particles deposit on both windward and leeward sides of tubes homogeneously.(2) The results show that all parameters such as particle size, pipe shape, flue gas velocity, spanwise tube pitch play important roles in deposition probability except longitudinal tube pitch; The results indicate that it has obvious effect on decreasing the deposition probability with increase of axial ratio, spanwise tube pitch and flue gas velocity; With the increase of longitudinal tube pitch, the deposition probability of submicron particles decrease dramatically, while a slight increase for large size and micro-sized particles. What’s more, deposition probability increase with the growth of ash particle size.(3) Characteristics of heat transfer and pressure drop were investigated, respectively, and the combined effect was predicted by comprehensive heat transfer performance PEC. The results show that PEC increase with the increase of ellipticity, flue gas velocity, or the decrease of spanwise tube pitch, and it reaches a maximum when S2/D equals to 2. Flue gas velocity has a remarkable effect on PEC; Nusselt number and perssure drop increase significantly with the increase of flue gas velocity, while show a downward trend with the increase of axial ratio, spanwise and longitudinal tube pitch.