M$-$ MASS TRANSFER

Removing $C{O}_2$ is an important step in natural gas purification technology because the

presence of $C{O}_2$ reduces natural gas heating value. Absorption is the most established

technology for $C{O}_2$ removal due to its ability to effectively reduce $C{O}_2$ concentration to

the desired target.

A packed absorption column is required to remove $C{O}_2$ from a $250$kmo$\frac{l}{h}$ natural gas

steam using aqueous Monoethanolamine $($MEA$)$ solution at a flow rate of $300$kmo$\frac{l}{h}$

and cross sectional area of the empty column is $1\mathrm{.}2m^2\mathrm{.}98\%$ of the $C{O}_2$ is to be

recovered from $10$ mole $\%C{O}_2$ natural gas mixture by scrubbing with $C{O}_2$ free MEA

solution at $35C$ and $5$ bar. The over$-$all volumetric mass transfer coefficient for

operating conditions is given as $K_y{a}_v=0\mathrm{.}1$kmo$\frac{l}{m^3}s$ bar.

At the operating pressure & temperature and within the concentration range involved,

equilibrium distribution of $C{O}_2$ between natural gas$-$MEA can be taken as $y^{**}=0\mathrm{.}78x$

a$)$ Calculate mol fractions and molar flowrates of the exit gas and liquid steams

$)$

b$)$ Write operating line equation $(5p)$

c$)$ Determine height of the packing $(10p)$

Spherical sodium sulphate particles with an approximate size of $2mm$ and density of

$1500k\frac{g}{m^3}$ will be pneumatically conveyed by air $(20C)$ from the hopper to the storage

tank using a fan. The production capacity of the sodium sulphate is $550$ tons$/$day$.$ The

mass solid ratio is adjusted to $10$ in the system; and air velocity is set at $2$ times the

terminal velocity of the particles. The hopper and the tank are open to the atmosphere;

and cyclone separator and air filters exist in the system. Considering the dimensions

given in Figure F$1,$ calculate

a$.$ the diameter of the stainless steel pipes of the system. $[8$ pts$].$

b$.$ the pressure losses caused by air flow $(P_{\text{a}\text{i}\text{r}}).$ There are three $($fully open$)$ globe

valves, two $135(\frac{L_e}{D}=16)$ elbow and one $90$ elbow on the pipeline. The total length

of horizontal pipes are $200m[9$ pts$],$

c$.$ the pressure losses caused by solid particles $(P_s)$ in the system using empirical

equations $[3pts],$

d$.$ the total pressure losses in the system $[5$ pts$].$