6.0 Reactor Sizing
In our conducted research, semi-batch reactor is implemented to our slow pyrolysis process of plant based material.
Theory and Calculation
As all the reactor does share the similar mole balance equation, we will derive further based on the condition taken. The general mole balance as shown in below is :
For batch reactor ,
Take reaction of A ---> B + C + D
As the reactor is being filled , the volume V changes according to time. Reactor volume at any time can be determined from the overall mass balance of all chemical species exist in the semi-batch reactor.
The rate constant can be determined with the equation as shown below:
The reaction order for pyrolysis of plant is shown to be first order according to data of pyrolysis of cellulose , as plants contains high amount of cellulose.
Assume the whole mass of the plant biomass is consists of 90% cellulose and 10 % water. The actual concentration of the cellulose can be determined as the mass of cellulose of 272.3 kg.
The volume of the biomass(cellulose) determined based on the density of cellulose is:
Find the concentration of cellulose in its own volume:
For the reaction of A-----> B + 0.2791C + 0.1026D, with conversion, X = 0.9806
Construct the stoichiometry table for batch process:
Find the value of rate constant k ,
where T is temperature in Kelvin. Temperature parameter is at 350= 623.15 K , R is gas constant.
Thus , the value of k determined is 0.006638 per second (first order reaction).
The time for the reaction is determined as the equation above, then by re-arranging the equation. The volume needed for the reaction is determined as:
For a normal slow pyrolysis process, the time taken is about 2 hrs = 7200 seconds.
Rounding up to possible sizing,
Volume of reactor = 4.00 L
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