To analyze the dry exhaust gas (DEG) from a combustion system using the Orsat apparatus.
As shown in figure, the Orsat apparatus consists of a water-jacketed 100-m1 burette B connected at its top to a glass manifold M and at its bottom to a leveling bottle L. The glass manifold M is connected to three reagent bulbs called pipettes P1, P2 and P3 via three cocks C1, C2 and C3. Each tube is filed with its own absorbing chemical solution: P1: potassium hydroxide (30 % w/v) to absorb CO2
P2: alkaline pyrogallol to absorb 02
P3: cuprous chloride in hydrochloric acid to absorb CO.
Pipettes P1 and P2 are partly filled with glass tubes to increase the contact surface area between liquid and glass. P3 contains copper wire to protect acid against possible oxidation. The 3-way cock C4 is used to connect manifold M to the atmosphere (via suction pump SP), to connect it to the sampler tube or to isolate the trapped gas.
a) Preparatory Steps
-Fill the system with water & chemicals as applicable.
-By opening one of the cocks C1, C2, C3 at a time and keeping all other cocks close, and manipulating bottle L bring the solution in each pipette to the top mark on the stem of the pipette. Then close the isolating cock. -Now connect the sampler line to suction pump SP by turning the 3-way valve C4. Operate the pump to purge all air from the sampler line.
b) Trapping the Gas Sample
-By turning the cock C4 connect the glass manifold M to the sampler line. -Lower bottle L slowly until the water level in burette B is slightly below the zero mark on the scale. Then close C4 and disconnect the sampler line. -Slightly lift cock C4 off its seat to equalize the pressure inside burette B with the ambient pressure. Then raise bottle L gently until water level in the burette coincides with the zero mark. This ensures that the burette now contains 100 ml of exhaust gas at atmospheric pressure.