Energy savings and emission reduction of traditional pollutants, particulate matter, and polycyclic aromatic hydrocarbon using solvent-containing water emulsified heavy fuel oil in boilers

Heavy fuel oil is one of the most commonly used petroleum fuels in boilers, although it is associated with a high level of pollutants. Emulsification is a developing technique to enhance fuel efficiency and reduce regulated pollution emissions. In the current study, the water phase of emulsified heavy oil contained 1 vol % methanol, 4 vol % isopropyl alcohol (IPA), and 95 vol % water, representing actual industrial solvent-containing wastewater (SCW). The SCW fractions in emulsified fuel were optimized by thermal, centrifugal, and 14-day standing stability tests. The emulsion M1P4-10 with 10 vol % SCW showed no separation and contained the smallest and most homogeneous water-in-oil (W/O) droplets after stability tests. Four boilers, including three with 3.6 and one with 10 ton h^-1 steam capacities, were employed to be operated for 30 h with a regular heavy fuel oil and M1P4-10. The microexplosion and tinder effects of solvent contents improved boiler efficiency by 10-33% and reduced fuel consumption by 5-31% using M1P4-10. The emulsion also reduced SO _x by 3.3-7.1%, particulate matter (PM) by 41-85%, CO by 89-93%, HC by 91-60%, and NO_x by 3.3-23%. With regard to inhibiting toxic air pollutants, the emission levels of total polycyclic aromatic hydrocarbons (PAHs) and total benzo[a]pyrene (BaP_eq) were reduced by 37.7 and 61.8%, respectively using M1P4-10. The PM and NO_x trade-off problem could be solved by lower temperature combustion of M1P4-10. Consequently, the solvent-containing wastewater emulsified heavy fuel oil could effectively promote boiler efficiency and reduce the pollutant emissions in a specific emulsifying ratio.