Reasons for Back Fire in afbc Boiler

Can you describe in greater detail the intended control sequence of this boiler? There are too many possibilities for good guessing, unless we know more.

Roughly speaking, it looks as though there is too much fuel (or too soon), and/or too little air (or too late), when ignition occurs. Several things can cause this.

The old problem, air fuel imbalance, have a close look at the PLL settings. CO at the exhaust is too high.

Sorry I meant PID control

Dear Shivak....chate, Is ignition going out and restarting during normal operation, or is it during light off? During light off you may be trying to increase the rate of firing to fast. What is the draft in the furnace? Is the ID fan and FD fan balanced, to achieve a slightly negative pressure? As Tony S was suggesting, are the controllers settings (is the operator able to.. bias settings ) adjusted correctly? What is the condition of the fuel... I have seen coal so dry that it is burning up, or so wet that water pouring out of coal lorry.

Klearzen

I'd forgotten about coal moisture, I've seen it arrive on fire due to spontaneous combustion, due to it being too dry. Other deliveries were like slop, too wet to do anything with!

In one night I had to replace 25 explosion panels due to crap coal! We tried PetCoke as an alternate to coal. That was a total disaster the coal mill was well on fire!