Over the past years there has been a dramatic increase in the regulatory requirements for low emissions from both new and existing utility boilers and gas turbines. Traditional methods of reducing NOx emissions, such as: modification of the firing system; and/or post combustion treatment of the flue gas to remove NOx; are very expensive. One of the attractive alternative fuels for combustion in the utility boilers and stationary gas turbines may be methanol.
Using methanol has become an important solution for emissions compliance due to their unique constituents and combustion characteristics. Methanol may be referred to as enviro fuel. The clean burning characteristics of methanol are expected to lead to clean pressure parts, turbine blades and lower maintenance than with fuel oil.
Here, we present results of the Israel Electric Corporation (IEC) for specific 140 MWe unit consisting of tangential fired pressurized boiler designed by Combustion Engineering Inc by using the co-firing of methanol with heavy fuel oil and FT4C TWIN PAC 50 MWe GT designed by Pratt & Whitney by using the full methanol firing.
The experiments performed for gas turbine tested different GT loads during methanol and LFO firing. The results presented here clearly show that with minor low cost fuel system retrofit methanol firing leads to significant NOx, SO2 and particulates emission reduction. NOx emissions were reduced more than 75% and are equal 75 mg/dNm3 at 15% O2. SO2 emissions were reduced to zero with methanol firing. Particulate emissions vary from 1.3 to 1.6 mg/dNm3 at 15% O2 with methanol firing, while with LFO this parameter was 13–37 mg/dNm3 at 15% O2.
The experiments performed for the boiler tested different methanol fractions of the total boiler heat capacity (from 33% to 50% heat), at different boiler loads. The results presented here show that NOx, SO2 and particulate emissions were reduced more than 20%, 35% and 40% accordingly.
We believe that the conclusions of the present work are general and can be applied to other boilers and gas turbines as well.