Patent ID: 7835868

Claim:
A process for selecting replacement shaped particles which are suitable for replacing shaped particles packed in an existing packed bed in a tube, wherein the process comprises: defining a desired value of a relative change in the pressure difference over the packed bed per unit length of the packed bed when the packed bed is subjected to conditions of a gas flowing through the packed bed, wherein the relative change results from the said replacement of the shaped particles by the replacement shaped particles, calculating dimensions of replacement shaped particles using a computer system having a central processing unit and a computer program such that a packed bed in the tube of the replacement shaped particles having the calculated dimensions exhibits a relative change in the pressure difference per unit length of the packed bed under the said conditions of gas flow which meets the desired value of the relative change in the pressure difference, and selecting the replacement shaped particles in accordance with the calculated dimensions, wherein the shaped particles of the existing packed bed are standard 8 mm cylinders, the replacement shaped particles have a cylinder geometric configuration, which may or may not be hollow, which is defined by a cylinder length, a cylinder diameter and a cylinder bore diameter, on the understanding that in the absence of a bore the cylinder bore diameter is deemed to be zero, and wherein the dimensions are calculated by using a relationship which can be defined by the following expression: (Δ P′−ΔP 1 )/Δ P 1 =s+t ×( L/D o )+ u×D o +v×D i +w×L+y×D t , wherein ΔP′ represents the pressure difference per unit length of the packed bed, ΔP 1 represents the pressure difference per unit length of the existing packed bed, (ΔP′−ΔP 1 )/ΔP 1 represents the desired value of the relative change in the pressure difference per unit length of the packed bed, L represents the cylinder length, D o represents the cylinder diameter, D i represents the cylinder bore diameter, D r represents the diameter of the tube, and each of s, t, u, v, w, and y represents a constant having a dimension accommodating the dimension of the corresponding term of the expressions.