I would like to ask the experts about the issue of igniting a fluidized bed

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Hello, masters. Today, the boiler in our plant was ignited with a normal bed of fuel; the bed temperature rose very slowly, remaining around 400 degrees throughout (the rate of temperature increase was more than an hour slower than usual), while the temperature in the air chamber was around 1000°C. At that time, the ignition air damper was fully open, and the initial opening degree of the main air damper was 11% (as the management was concerned that there wouldn’t be enough airflow, that closing it too tightly might cause it to get stuck and prevent it from being opened later, and there was also a risk of damaging the main air damper, among other reasons). No other types of air such as mixed air were used for igniting this boiler. At that time, I thought I should reduce the opening of the main air valve, but another supervisor told me to increase its opening in order to supply heat from the air chamber to the bed material. I was puzzled at the time. So I would like to ask the experts here: in this situation, should it be turned down or turned up? There’s another issue I don’t quite understand: why is it necessary to design both an ignition air duct and a main air duct in a boiler? If the ignition air duct is sufficient for fluidizing the material layer, then what’s the need for an additional main air duct? Is it simply because the main air duct provides less assistance, or are there other factors at play? I earnestly ask all the experts for their guidance.