Patent ID: 7704456

Claim:
A NO x removal catalyst management unit comprising: a NO x measurement means for determining NO x concentrations on the inlet and outlet sides of respective NO x removal catalyst layers; a NH 3 measurement means for determining NH 3 concentrations on the inlet and outlet sides of the same NO x removal catalyst layers; and a percent NO x removal determination means for determining percent NO x removal (η) on the basis of an inlet mole ratio (i.e., inlet NH 3 /inlet NO x ), which percent NO x removal (η) is determined on the basis of the following equation (1): η = ( ( inlet ⁢ ⁢ NH 3 - outlet ⁢ ⁢ ⁢ NH 3 ) ( inlet ⁢ ⁢ ⁢ ⁢ NH 3 - outlet ⁢ ⁢ NH 3 + outlet ⁢ ⁢ NO x ) ) × 100 × evaluation ⁢ ⁢ ⁢ mole ⁢ ⁢ ratio inlet ⁢ ⁢ mole ⁢ ⁢ ratio ( 1 ) wherein: the inlet mole ratio is derived from a NO x concentration as measured on the inlet side by means of said NO x measurement means and an NH 3 concentration as measured on the inlet side by means of said NH 3 measurement means; the inlet NH 3 concentration is an NH 3 concentration as measured on the inlet side; the outlet NH 3 concentration is an NH 3 concentration as measured on the outlet side; the outlet NO x concentration is a NO x concentration as measured on the outlet side; and the evaluation mole ratio is predetermined for the purpose of evaluating respective NO x removal catalyst layers or plurality of NO x catalyst layers.