Additional Information on Proposed Methodology“Waste heat recovery and utilization by installing Heat exchanger toexisting waste heat recovery boiler of gas co-generation system”

The way of thinking about BaU (in case that existing activity would be continue in the absenceof the project) emissions, reference emissions and net emission reductions in this methodology
are as follows;
By implementing the project, the amount of fossil gas fuel consumed by duct burner of heatrecovery steam generator (HRSG) is reduced because that the temperature of feed water into
HRSG is increased by heat recovered by project heat exchanger.
While the amount of waste heat from exhaust gas of gas turbine into HRSG is expected to besame as the one without in the absence of the project (BaU status).
𝑄𝐻𝑔𝑡,𝑖𝑛,𝐵𝑎𝑈 = 𝑄𝐻𝑔𝑡,𝑖𝑛,𝑃𝐽 (= 𝑄𝐻𝑔𝑡,𝑖𝑛 )𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 > 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽
𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 / 𝑄𝐻𝑔𝑡,𝑖𝑛,𝐵𝑎𝑈 > 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 / 𝑄𝐻𝑔𝑡,𝑖𝑛,𝑃𝐽
As for reference status in this methodology, it is assumed as the following 2 equations tosecure net emission reductions;𝑄𝐻𝑑𝑏,𝑖𝑛,𝑅𝐸 + 𝑄𝐻𝑔𝑡,𝑖𝑛,𝑅𝐸 = 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 + 𝑄𝐻𝑔𝑡,𝑖𝑛,𝑃𝐽 < ( 𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 + 𝑄𝐻𝑔𝑡,𝑖𝑛,𝐵𝑎𝑈 )the ratio of 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑅𝐸 to 𝑄𝐻𝑔𝑡,𝑖𝑛,𝑅𝐸 is set to be same as the one in BaU to secureconservativeness in reference.
𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 / 𝑄𝐻𝑔𝑡,𝑖𝑛,𝐵𝑎𝑈 = 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑅𝐸 / 𝑄𝐻𝑔𝑡,𝑖𝑛,𝑅𝐸 > 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 / 𝑄𝐻𝑔𝑡,𝑖𝑛,𝑃𝐽
So, the following 2 magnitude relationships are shown.
𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 > 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑅𝐸 > 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽
𝑄𝐻𝑔𝑡,𝑖𝑛,𝐵𝑎𝑈 = 𝑄𝐻𝑔𝑡,𝑖𝑛,𝑃𝐽 (= 𝑄𝐻𝑔𝑡,𝑖𝑛 ) > 𝑄𝐻𝑔𝑡,𝑖𝑛,𝑅𝐸Where;1

𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈:Amount of heating energy inputted into feed water through combustion offossil gas fuel by duct burner in the absence of the project (BaU status) [GJ]

𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽:

Amount of heating energy inputted into feed water through combustion offossil gas fuel by duct burner in the project [GJ]

𝑄𝐻𝑑𝑏,𝑖𝑛,𝑅𝐸:

Amount of heating energy inputted into feed water through combustion offossil gas fuel by duct burner in reference [GJ]

𝑄𝐻𝑔𝑡,𝑖𝑛,𝐵𝑎𝑈:

Amount of heating energy inputted into feed water through waste heat fromexhaust gas of gas turbine in the absence of the project (BaU status) [GJ]

𝑄𝐻𝑔𝑡,𝑖𝑛,𝑃𝐽:

Amount of heating energy inputted into feed water through waste heat fromexhaust gas of gas turbine in the project [GJ]

𝑄𝐻𝑔𝑡,𝑖𝑛,𝑅𝐸:

Amount of heating energy inputted into feed water through f waste heatfrom exhaust gas of gas turbine in reference [GJ]

Heating energy of feed water
gained at Steam Heat recovery
steam generator (HRSG)

Heating energy inputted into feedwater at Steam Heat recovery
steam generator (HRSG)
QHdb,in,BaU

BaU status

QHgt,inHeat inputted through waste heat fromexhaust gas of gas turbine

Project
statusQHgt,in

QHdb,out,Bau

Heat
QHgt,out,BaU
inputtedthroughHeat gained through waste
combustion heat from exhaust gas of gasof fossil
turbinegas fuel by
duct burner
QHgt,out,PJ
QH

Heat gained throughcombustion of fossil gas
fuel by duct burner

db,in,PJ

QHdb,out,PJ(QHdb,in,BaU − QHdb,in,PJ)

Heat recovered by
Project heat exchanger(QHdb,in,BaU − QHdb,in,RE)

Reference
statusQHRhe,PJ

QHgt,in,RE

QHgt,out,RE
QHdb,in,RE

QHdb,out,REQHTfw,PJ

QHgt,in,RE + QHdb,in,RE = QHgt,in + QHdb,in,PJ

Amount of heating energy
transferred into the feed water
through the heat recovery steam
generator

QHgt,in,RE : QHdb,in,RE ≒ QHgt,in : QHdb,in,BaUNote) Only 2 parameters in green highlight can be known by measured data and calculation after
the project starts
Only 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 , 𝑄𝐻𝑅ℎ𝑒,𝑃𝐽 and 𝑄𝐻𝑇𝑓𝑤,𝑃𝐽 can be estimated in the project.
Therefore, use these three to conservatively calculate reference emissions.
BaU (in the absence of the project) emissions is shown as follows;2𝐵𝐸 = (𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 − 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 ) × 𝐸𝐹𝑔𝑎𝑠,𝑓𝑢𝑒𝑙Utilization situation of waste heat by exhaust gas of gas turbine within Steam Heat recovery steam
generator (HRSG) nearly unchanged in the presence or absence of project. In both supply the sidefor heating energy inputted into feed water (the left side in above figure) and the side for heatingenergy of feed water gained (the right side in above figure), the sharing rate of the amount ofheating energy through waste heat from exhaust gas of gas turbine in total amount of heatingenergies in project is rarely different from the one in BaU.
So, It can be inferred that the ratio of the amount of heating energy of gas fuel saved by project( 𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 − 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 ) to the amount of heating energy of gas fuel consumed in
BaU (𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 ) is rarely different from the ratio of the amount of heat energy recovered by
Project heat exchanger (𝑄𝐻𝑅ℎ𝑒,𝑃𝐽 ) to the amount of heating energy gained through combustionof fossil gas fuel by duct burner in BaU (𝑄𝐻𝑑𝑏,𝑜𝑢𝑡,𝐵𝑎𝑈 ).
(𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 − 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 )/ 𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈≒ 𝑄𝐻𝑅ℎ𝑒,𝑃𝐽 / 𝑄𝐻𝑑𝑏,𝑜𝑢𝑡,𝐵𝑎𝑈

Furthermore, It can be inferred that the ratio of the amount of heating energy of gas fuel saved byproject (𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 − 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 ) to the amount of heating energy of gas fuel consumed in
Project (𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 ) is rarely different from the ratio of the amount of heat energy recovered by
Project heat exchanger (𝑄𝐻𝑅ℎ𝑒,𝑃𝐽 ) to the amount of heating energy gained through combustionof fossil gas fuel by duct burner in Project (𝑄𝐻𝑑𝑏,𝑜𝑢𝑡,𝑃𝐽 ).
(𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 − 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 )/ 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽≒ 𝑄𝐻𝑅ℎ𝑒,𝑃𝐽 / 𝑄𝐻𝑑𝑏,𝑜𝑢𝑡,𝑃𝐽

So, (𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 − 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 ) is shown as follows;(𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈 − 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 ) ≒ 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 × 𝑄𝐻𝑅ℎ𝑒,𝑃𝐽 / 𝑄𝐻𝑑𝑏,𝑜𝑢𝑡,𝑃𝐽
So, BE is shown as follows:
Therefore, BaU emissions can be shown as the hollowing equation.
𝐵𝐸 ≒ 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 × (𝑄𝐻𝑅ℎ𝑒,𝑃𝐽 /𝑄𝐻𝑑𝑏,𝑜𝑢𝑡,𝑃𝐽 ) × 𝐸𝐹𝑔𝑎𝑠,𝑓𝑢𝑒𝑙Above equation means that heating energy saved by the project is almost only the one from fossil
gas fuel consumed by duct burner.
Next, the following equation means that the total amount of heating energy saved by the project3

is distributed into the one from fossil gas fuel consumed by duct burner and the one of waste heatfrom exhaust gas of gas turbine by a certain ratio. So, the amount of saving fossil gas fuelconsumed by duct burner is conservatively identified.
(If the value of 𝑄𝐻𝑔𝑡,𝑜𝑢𝑡,𝑃𝐽 (parameters in blue highlight) is added to the section of denominator,
the value of the following section will be lower than the value of the above-described section)> 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 × {𝑄𝐻𝑅ℎ𝑒,𝑃𝐽 /(𝑄𝐻𝑔𝑡,𝑜𝑢𝑡,𝑃𝐽 + 𝑄𝐻𝑑𝑏,𝑜𝑢𝑡,𝑃𝐽 )} × 𝐸𝐹𝑔𝑎𝑠,𝑓𝑢𝑒𝑙= 𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽 × (𝑄𝐻𝑅ℎ𝑒,𝑃𝐽 /𝑄𝐻𝑇𝑓𝑤,𝑃𝐽 ) × 𝐸𝐹𝑔𝑎𝑠,𝑓𝑢𝑒𝑙= 𝑅𝐸
Where;BE:

Emissions in the absence of the project [tCO2]

RE:

Reference emissions [tCO2]

𝑄𝐻𝑑𝑏,𝑖𝑛,𝐵𝑎𝑈:

Amount of heating energy inputted into feed water through combustion offossil gas fuel by duct burner in the absence of the project (BaU status)[GJ]

𝑄𝐻𝑑𝑏,𝑖𝑛,𝑃𝐽:

Amount of heating energy inputted into feed water through combustion offossil gas fuel by duct burner in the project [GJ]𝑄𝐻𝑅ℎ𝑒,𝑃𝐽,𝑖,𝑝 :Amount of heating energy recovered by project heat exchanger [GJ]

𝑄𝐻𝑑𝑏,𝑜𝑢𝑡,𝑃𝐽

Amount of heating energy of feed water gained through combustion offossil gas fuel by duct burner in the project [GJ]

𝑄𝐻𝑔𝑡,𝑜𝑢𝑡,𝑃𝐽:

Amount of heating energy of feed water gained through recovery of waste
heat by exhaust gas of gas turbine in the project [GJ]

𝐸𝐹𝑔𝑎𝑠,𝑓𝑢𝑒𝑙:CO2 emission factor for the fossil gas fuel consumed by duct burner

𝑄𝐻𝑇𝑓𝑤,𝑃𝐽:

Amount of heating energy transferred into the feed water through the heatrecovery steam generator with project heat exchanger [GJ]

Therefore, as above mentioned, the amount of fossil gas fuel saved by the project is calculated
lower than the one in actual status and reference emissions are ensured net emission reductions.

4