No abstract

No abstract

No abstract

Coal and biomass co-combustion in existing utility boilers is a promising option of mitigating the fossil energy crisis and reducing the gaseous emissions of NO x , SO x , and CO2. However, ash-related problems, including fouling, slagging, and corrosion cause damage to the heat exchange tube and reduce boiler efficiency. In an attempt to give better insights into the slagging behavior during coal/biomass combustion, an experimental investigation was conducted to study the growth of slag when coal was co-fired with wood and corn stalk in a 300 kW pilot-scale furnace. For comparison, combustion of pure coal was also conducted. During the experiments, biomass proportions of 5 and 10% by weight were examined. Slags formed on an oil-cooled deposition probe were collected, sampled, and analyzed using scanning electron microscopy and X-ray diffraction (XRD). The change in slag thickness with time was obtained by a charge-coupled device monitoring system. With two thermocouples in the probe, the heat flux through the slag could be measured. The slag from pure coal combustion showed a layered structure with different levels of compactness and hardness. The heat flux decreased by 31.7% as the slag grew to 5.19 mm. The results showed that co-firing wood significantly inhibited the slagging behavior. Especially in the 10% wood case, hardly any slag was collected from the probe. Nevertheless, co-firing corn stalk resulted in severe slagging, with a slag thickness of 5.5 and 6.1 mm for two blend ratios. The formation of bubbles in the deposits together with greater deposit thickness caused heat transfer deterioration. XRD results revealed that the influence of co-firing biomass and corn stalk caused quite different changes to mineral species from wood. It was observed that fly ash under different biomass co-firing conditions differed little on mineral compositions.

No abstract

No abstract

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

No abstract