Yes – but that does not mean that that is the best way to do it, for reasons of efficiency, emissions and control.

Forget your load (8000 kg/h) as it is not really relevant.  Take a look at some 19th / early 20th century boilers which were operated on natural draught only (no fans):

old boiler factories

These stacks achieved air flows required to the fire boilers without the use of fans at all.  You do not actually need a fan to achieve any boiler load you can think of.

Moving on to the present day: Fans (ID or FD) are used to impart a degree of control, and they also enable the stack (or chimney) height to be decreased.

If you wish to use an ID fan only you will not get proper control of primary, secondary and tertiary (if used) air to the burners.  Thus, you cannot apply low NOx burners effectively.  For this you need a forced draught fan.

ID fans are a maintenance nightmare since they operate in hot conditions and are subject to hot corrosive ash etc from the combustion process.

Also, with ID only fans, the furnace tends to operate under a fairly low pressure (compared with other draught types) and this tends to promote air leakage into the boiler or furnace (‘tramp air’, which lowers efficiency).

Although combination (or ‘balanced’) ID +FD air systems have been preferred in the past few decades, with modern, properly sealed ‘pressure boiler’ technology, you should expect to see most modern boilers of the forced draught type only.