Air and water pollution control., HTML programming, GNU Linux.

Thursday, 24 July 2008

Air pollution calculations part II

In previous article we saw what is the limits from chimney stacks for SO2 and NOx(measured as NO2). In this part we will see how to calculate the emissions of SO2 when we have measured sulfur contain in the liquid fuel. This computing method is based on stoichiometric understanding of process of fuel burn.
At first we should look at sulfur as independent compound in the fuel. When the burning process become with normal oxygen content – 3% we has this chemical equation:

S2 + 2O2 = 2SO2

Sulfur oxidizes to the sulfur dioxide. We have two sulfur atoms equivalent with molar mass 64 which react with two molecules of oxygen with summed molar mass 32+32=64. Then we are able to say:

64+2x32=128

So from one molecule of sulfur we received two molecule of sulfur dioxide with double increased molar mass and the correlation is 1:2. With this conclusion we could determinate how concentration of SO2 we should expect in chimney gases. Let start with 2 % sulfur contain in the fuel which we burn in combustion chamber. If we burn at least 700 kg per hour liquid fuel then we shall burn around 14 kilos of sulfur. From these 14 kilos we will receive 28 kilos of sulfur dioxide at this scheme:

700 kg x 2 % = 14 kg

1 mol S --> 2 mol SO2
14 mol S --> 28 mol SO2
14 kg --> 28 kg SO2

From 700 kilos of our 2 % contained sulfur powered fuel we had received a 28 kilos of sulfur dioxide. Now the questions are how chimney gases we should receive from this fuel. As far as I know 1000 kg of fuel give us 12 500 normal cubic meters of chimney gases. I have spoken with many peoples – all of them are engineers and many of them said that this digit is not so correct and it depends from type of fuel. It can decrease the size and gain the 20 000 m3. So I have been teach from my ex-boss on this value and we will work with it.
Before we start to work we will take care for dimensions. Because the limits are in mg/m3 we must change the dimensions in this 700 kg/h of fuel is a 0.7 tons/h of fuel. Our 28 kg/h of sulfur dioxide is a 28 000 g/h or 28 000 000 mg/h of sulfur dioxide – to describe this we could use the term: output of the emission.

And then:

From 0.7t/h we have 0.7 x 12 500 = 8 750 m3/h chimney gases,

The concentration of SO2 in chimney gases must be:

28 000 000 / 8 750 = 3 200 mg/m3
I have just prepared one table in google docs where everyone can calculate these emissions. If you know what is the load of your furnace for hour and what is the content of sulfur in the fuel you are able to calculate the emissions of SO2.

Little calculator.

In the end just want to say if you look careful over the formula you will see that there the limited factor is only sulfur contain in fuel. The quantity of burned fuel is given only for volume of chimney gases. In our example we break the sulfur dioxide level which is placed from EC in the

2 comments:

JR said...

If you want any reader to be able to access that spreadsheet calculator, you need to either:

1 - add a parameter to the end of the link (&newcopy) which will give each person who clicks it their own copy of the spreadsheet in their google Docs account.... OR

2 - check the option "Allow anyone to edit (without logging in)" - which will grant anyone edit access to the same copy of the spreadsheet - which means you should back it up first (using "copy spreadsheet") in case ome rogue editor changes your formulas....

Or - you can just invite those specific people who you trust to edit it.

mjekov said...

Thanks @jr I just skip this moment in the link.
Thanks again!