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Understanding the reduction mechanism of additives on ammonium bisulfate (ABS) fouling formation can alleviate ABS fouling problems. This paper presents an investigation of the influence of Na 2 SO 3 /NaHSO 3 on the formation process of ABS fouling with an in situ measurement technique. According to the thickness curves, both Na 2 SO 3 and NaHSO 3 can control the growth of ABS fouling, but Na 2 SO 3 shows a better inhibitory effect on the growth of ABS fouling. Meanwhile, the mitigation effect of the additive on ABS fouling increases with the increasing injection quantity of the additive. The results of the heat flux show that the heat transfer performance of the fouling probe becomes better with the injection of additives, whereas the heat transfer performance becomes worse with the increasing injection quantity of additives. The thermal resistance of ABS fouling provides a reasonable agreement with the results of the heat flux. The SEM-EDX results show that the additives have an effect on the formation of ABS fouling by controlling the ABS concentration, which can increase the viscosity of the particle, promote the agglomeration of the fouling particle, and enhance the heat transfer of the ABS fouling, providing a rational explanation for the experimental results. KEYWORDSadditive, effective thermal conductivity, in situ measurement, low-temperature ash deposition

The selective catalytic reduction technology has the potential hazards of NH 3 escape while catalytically reducing NOx. The HCl in the flue gas can react with the NH 3 under certain conditions to form NH 4 Cl and deposit in the appropriate temperature range. In this study, the deposition behavior of fly ash and NH 4 Cl was studied by a charge-coupled device (CCD) camera in a drop tube furnace under the condition of the NH 4 Cl atmosphere. To investigate the effect of surface temperature on the deposition characteristics, we set the surface temperature at 363 K for Case 1, 373 K for Case 2, and 383 K for Case 3, respectively. The CCD camera monitored the morphology of ash deposit growth, and two type-K thermocouples measured the temperature of the inner and outer surfaces of the deposition probe. Collected deposit samples were analyzed by scanning electron microscopy and X-ray diffraction. The results showed that the primary substance of the deposited sediments was salammoniac (NH 4 Cl). The crystal granules of NH 4 Cl in the deposited sediment were disconnected, and they were denser under the lower surface temperatures. The deposited layer caused a declination in the heat flux through the deposition probe, and the lower surface temperature was more conducive to the growth of the deposition. This work contributes to a deeper understanding of the characteristics of NH 4 Cl deposition, which has practical utility in preventing the formation of the NH 4 Cl deposition in the precipitator and induced draft fans. K E Y W O R D Sammonium chloride, ash deposition, flue gas, selective catalyst reduction