Question

Method 2: Determine the concentration of the fertiliser at the outlet A using component material balance around the fertiliser feed. 9. = 2 m3/h VVVVV fertiliser feed F(kg/h) > q.= 4 mº/h Reattempt the same question assuming the plant feed as 0.45 L/h with a density 900 kg/m3.

I have done the second part of the question with a plant feed of 0.45L/h. I assumed they meant the fertiliser feed, am I right?

I am just stuck on the first part, determine the concentration at the outlet using a component material balance around the fertiliser feed. I don't know if the original question data will be needed. I put a picture of the original question too.

thanks

Answer 1

I think you are confused about calculating the concentration in mole/volume or may be not.Hope you might be knowing that density is also a representation of concentration ,so we use specific term for both like Molar density for concentration while mass density for simple density kg/volume and thus both are interrelated.

Now coming to the question,for solving it one must know the fundamentals i.e. density or concentration is an intesive property.So if we add certain mass or moles of any solute to the water definitely it will change the concentration because the number of molesor mass has been increased now and hence the concentration is changed.But when we will take out some volume from a particular solution of solute,then also the concentration of solute will not change in the solution or the volume which is taken out because the mass or moles of solute has been distributed through out the solution uniformly and we represent concentration per unit volume so that remains unchanged in that case.

So in this problem once the mass of fertiliser has been added to the water, it will be distributed uniformly throught and hence the concentration of fertiliser remains the same after mixing and is equal to concentration in any row.Hence finding out the concentration at outlet A itself means finding out the concentration before the water is distributed to any row of tomato.

- Raamilho 902 m?lut . 5kglho Fertiliser feed ngit , qp 24m3 lno . Applying Mans Balance for the fertiliser, mans of fertiliser before mining = man of . fertiliser after mixing with water. Steady water outlet a 4 milhr. Inlet . 9 = 2m3/hr .. water being returned a 4-2= 2 mlho so the Total volume How rate with which - fertiliser is being mixed = R+% = 2+2=4 m3 . from man balance, inctial feed mass a mass of fertiliser in r solution. .5 kg lho - Clky, 2 x VG (m2) no) - is kg / hra (x4 ) c. = 152 Hence the concentration in Outlet A z B = G =D2E 30/25 Kg 1m3 125 kg Het m3 - - -