Air Pollution · Environmental Engineering · GATE CE

A hydrocarbon $\left(\mathrm{C}_n \mathrm{H}_m\right)$ is burnt in air $\left(\mathrm{O}_2+3.78 \mathrm{~N}_2\right)$. The stoichiometric fuel to air mass ratio for this process is

Note: Atomic Weight: $\mathrm{C}(12), \mathrm{H}(1)$

Effective Molecular Weight: Air(28.8)

Ignore any conversion of N 2 in air to the oxides of nitrogen $\left(\mathrm{NO}_{\mathrm{x}}\right)$

A settling chamber is used for the removal of discrete particulate matter from air with following conditions. Horizontal velocity of air $=0.2 \mathrm{~m} / \mathrm{s}$; Temperature of air stream $=77^{\circ} \mathrm{C}$; Specific gravity of particle to be removed $=2.65$; Chamber length $=12 \mathrm{~m}$; Chamber height = 2 m ;

Viscosity of air at $77^{\circ} \mathrm{C}=2.1 \times 10^{-5} \mathrm{~kg} / \mathrm{m} . \mathrm{s}$;

Acceleration due to gravity $(\mathrm{g})=9.81 \mathrm{~m} / \mathrm{s}^2$; Density of air at $77^{\circ} \mathrm{C}=1.0 \mathrm{~kg} / \mathrm{m}^3$;

Assume the density of water as $1000 \mathrm{~kg} / \mathrm{m}^3$ and Laminar condition exists in the chamber.

The minimum size of particle that will be removed with 100\% efficiency in the settling chamber (in $\mu \mathrm{m}$ ) is ___________ (round off to one decimal place).

Match the following air pollutants with the most appropriate adverse health effects :

A sample of air analyzed at 25$$^\circ$$C and 1 atm pressure is reported to contain 0.04 ppm of SO₂. Atomic mass of S = 32. O = 16. The equivalent SO₂ concentration (in $$\mu$$g/m²) will be __________. (round off to the nearest integer)

The concentration s(x, t) of pollutants, in a one-dimensional reservoir at position x and time t satisfies the diffusion equation

$${{\partial s(x,t)} \over {\partial t}} = D{{{\partial ^2}s(x,t)} \over {\partial {x^2}}}$$

on the domain 0 $$\le$$ x $$\le$$ L, where D is the diffusion coefficient of the pollutants. The initial condition s(x, 0) is defined by the step-function shown in the figure.

The boundary conditions of the problem are given by $${{\partial s(x,t)} \over {\partial x}}$$ = 0 at the boundary points x = 0 and x = L at all times. Consider D = 0.1 m²/s, s₀ = 5 $$\mu$$mol/m and L = 10 m. The steady-state concentration $$\overline s \left( {{L \over 2}} \right) = s\left( {{L \over 2},\infty } \right)$$ at the center x = $${{L \over 2}}$$ of the reservoir (in $$\mu$$mol/m) is __________. (in integer)