Boiler Air / Gas Ratio

What kind of boiler do you have?

by adjusting air damper cam switch in air modulator or adjust fuel flow according by adjusting flow comutator .

thanks

tmp

This will be specific to the type of boiler you have, along with its control system. There are various ways to link the fuel rate with the air flow, and this should be described in the operating manual. If this is not available, try to get a copy from the manufacturer. Or engage a qualified boiler service person/company.

TORNADO's last comment is right on.

The relatively low cost of hiring a company that specializes in tuning boilers will yield pay back in less than 3 months due to enhanced boiler efficiency and fuel savings.

If your boiler sees a wide variety of loads throughout the day, or seasonally, you should have the boiler re-tuned at least once a year- probably right after your annual inspection- and perhaps twice a year if daily load fluctuations are occuring.

Hi arulmurugan,

The adjustment of A/F ratio can only be undertaken safely by person(s) trained on that particular burner product. In some countries eg UK,this is a mandatory requirement as the competent person must be a registered combustion/gas technician.

Notwithstanding this, the characteristic of the combustion process will vary across the whole firing range. The burner manufacturer will specify the maximum turn-down for a given application, this defines the least amount of fuel which can be reliably ignited and the resultant flue gases will have a relatively high excess oxygen level >6%. As the fuel rate increases towards hi-fire the ability to burn the fuel more effectively increases and with natural gas you should be able to get the excess oxygen level down to around 2.5% at mcr.The limiting condition is always avoiding the production of discernible levels of carbon monoxide. This should be virtually zero at all firing levels.You will appreciate therefore that flue gas analysis forms an essential part of setting up the burner.You will see that in measuring all the parameters including stack temperatures will will be able to determine the efficiency of combustion and hence boiler efficiency.

The example I have chosen is in fact a 5MW dual fuel fully modulating forced draught burner application;but simpler variants still need to abide by these basic principles.

Good luck,

Massey

You cannot do it yourself. Call an expert who does combustion analysis. He will come with his analyzer check present air/gas ratio, adjust the burner damper & controls, re-check again, adjust again till he gets the optimum value of 0-4% excess oxygen at the flue gas. Print out both the prior and after settings , give you his bill, collect his payment and walk off. You have to call him again after 4 months to do it again or come in contract on annual basis.

Secondly you can purchase an on-line O2 analyzer set and it will continuously modulate the burners on high/low .

Dear Sir,

It is possible to do it electronically. First find out required ratio required theorotically. Take one signal from stack temp. onesignal from fuel pump from flow of fuel and one signal from blower air supply. feedback is to be given to plc. plc processes the signal and sets the vfd for blower. With respect to blower pressure regulation a ratio controller can control the fuel pump motor. This type of arrangment gives altra high precision in burner control.

kiran nawathe

Look at the flue gas composition: too much air and the flue gas temperature will drop, fuel will be wasted, and the top of the exhaust stack will begin to corrode; too little air and fuel will be wasted, the flue gas temperature will drop, the top of the exhaust stack will begin to corrode and the top of the stack will produce smoke.

If the <...we...> cannot handle the balancing itself, then it would be worthwhile consulting a specialist; if in doubt, call the <...Boiler...> manufacturer and arrange a site visit.