E3.9 Destruction and Removal Efficiency

Example 3.9: A mixture described below is being incinerated at 2000 °F with 50% excess air and a residence time of 2.1 seconds. The flow rate from the incinerator is measured at 12500 dscfm (dry standard cubic feet per minute). The O₂ concentration in the flue gas is 7.0%. Calculate DRE for all organic compounds; concentration of particulates leaving the system, gr/dscf; and the removal efficiency for HCl. The following data apply:

Hydrochloric acid gas is leaving at a rate of 10.7 lb/h. Particulate matter in exit gases is 23.4 gr/dscf. Molecular weight of HCl is 36.45.

Solution Basis 1 h of operation.

Destruction and removal efficiency (DRE):

DRE = (W_in - W_out)/W_in

And is tabulated for different components

Chlorobenzene reacted = 1150 - 0.11 = 1149.89 lb = 1149.89/112.5 = 10.22 moles

From the stoichiometry, one mole of chlorobenzene can produce one mole of HCl.

HCl produced = 10.22 moles = 10.22(36.45) = 372.56 lb

The incinerated stream goes to the absorber where HCl is absorbed.

Mass of HCl in the stream leaving the absorber is = 10.7 lb

HCl removal efficiency = (372.56 - 10.7)/372.56 = 97.128%

Concentration of particulate matter leaving the system

= 23.4(7000)/(12500(60)) = 0.2184 gr/dscf