3 replies to this topic

[rangaraj]

Dear Sirs,

I am presently working on a HP chemical dosing system (Tri sodium phosphate) for 80TPH boiler.

Please help me in calculating the metering pump flow rate and chemical dosing charge rate for the boiler.

Below are the relevant data:
Boiler steam rate: 320000kg/hr
Blow down: 3% - 9600 kg/hr
Chemical - Trisodium phosphate (Mol.wt - 380)
Residual phosphate to be maintained in steam drum - 7 ppm
Solution strength - 1%

Advance Thanks

[JoeWong]

Dear Sirs,

I am presently working on a HP chemical dosing system (Tri sodium phosphate) for 80TPH boiler.

Please help me in calculating the metering pump flow rate and chemical dosing charge rate for the boiler.

Below are the relevant data:
Boiler steam rate: 320000kg/hr
Blow down: 3% - 9600 kg/hr
Chemical - Trisodium phosphate (Mol.wt - 380)
Residual phosphate to be maintained in steam drum - 7 ppm
Solution strength - 1%

Advance Thanks

rangaraj,
Welcome...

Assuming there is NO phosphate leaving with steam by carry over,

Quantity of phosphate feeding to drum via injection = quantity of phosphate leaving drum via blowdown

1st, you can calculate the quantity of phosphate leaving drum via blowdown as you know the phosphate concentration in steam drum (e.g. 7 ppm) and blowdown rate (e.g. 9600 kg/h) ...

2nd, you have the concentration of phosphate feeding (e.g. 1%) to drum via injection...

You can calculate quantity of Trisodium phosphate feed...

Remaining is just arithmatic and unit conversion problem for you...

[djack77494]

Just elaborating slightly on what Joe has said, I think of your blowdown water flowrate as 9600kg/hr + 99% of the chemical dosing rate. The phosphate flowrate is 1% of the chemical dosing rate. Total blowdown rate = 9600 + chemical dosing rate. So your phosphate concentration = 7 ppm (by weight) =
1% * chemical dosing rate / {9600 + 99% * chemical dosing rate)
There's only one unknown in this equation, so it is quite easy to solve for.
In fact, the chemical dosing rate is probably <<< blowdown rate, and so can be neglected in the denominator.
Doug

[rangaraj]

Thanks all for your replies.