[Objective

]

The combustion of high-alkali coal is highly susceptible to severe fouling and slagging issues. Existing research has primarily focused on conventional loads. However

after the boiler drops to low load under deep peak shaving

the mechanisms underlying changes in fouling and NO

x

generation characteristics during highalkali coal combustion remain unclear

necessitating further in-depth investigation. [Methods

]

Targeted experiments were conducted using a muffle furnace and a two-stage drop tube furnace to study the fouling and NO

x

generation characteristics of high-alkali coal combustion under low-load conditions. In the two-stage drop tube furnace experiments

both conventional load and low load conditions were set to simulate actual deep peak-shaving scenarios. [Results

]

The experimental results indicate

that for Hami coal

as the burial depth increases

the occurrence forms of alkali metals in the ash gradually shift from aluminosilicates to sulfates. Moreover

the degree of influence of load variations on the microscopic morphology of ash also diminishes. Compared to conventional loads

under deep peak-shaving low loads

high-alkali coal with high iron

sulfur

and calcium content exhibits enhanced ash melting

increased viscosity

and a greater propensity for fouling(from 14.6 to 16.2 mg/g and from 9.0 to 12.8 mg/g) due to an increase in particles such as sodium and calcium sulfate on the ash surface. In contrast

high-alkali coal with high silicon and aluminum content shows little change in the number of sticky particles on the ash surface

resulting in a smaller or even reduced propensity for fouling(from 12.9 to 6.7 mg/g)

as most of the free sodium is captured by silicon or aluminum

and the release of calcium is suppressed. Furthermore

under deep peak-shaving low loads

the nitrogen conversion rate of high-alkali coal combustion generally increases by approximately 7%. However

for coal types with higher volatile matter content(30%)

the nitrogen conversion rate could decrease. This could be attributed to the organic volatiles released during combustion

which are difficult to fully burn at lower temperatures

leading to a significant decline in combustion efficiency. [Conclusion

]

When a boiler shifts from conventional load operation to deep peak-shaving under low-load conditions

priority should be given to selecting coal types with higher volatile matter content and higher levels of silicon and aluminum to ensure the safety and reliability of unit operation.