A fast pyrolysis process yields 15%wt (d.b.) raw char which contains only 80% of

Question

A fast pyrolysis process yields 15%wt (d.b.) raw char which contains only 80% of pure carbon. Could it possibly provide the heat needed for the feedstock to                    reach the operating temperature of 550?C if it is completely combusted in a furnace and supplied to the pyrolyzer? Do you need to provide externally additional                    heat to maintain 55C if the drying process has an efficiency of 50% (i.e., 50% heat is lost to environment through walls of facility and in the spent gas.

                    The woody biomass (10% MC, w.b.; 100?C) is fed at a rate of 1,000kg/h to the system. The heats of endothermic reactions are assumed the same as the heats of                    exothermic reactions, thus neglected for this estimation. The heat capacity of this woody biomass, 2.72 kJ/kg

Explanation / Answer

Rate of raw char produced = 0.15*1000 Kg/h = 150Kg/h

Mass of pure carbon in char produced = 0.8*150 = 120Kg/h

Energy required for elevating the feedstock to the operational temperature = 1000*2.72*(550-100)

= 1.224*10^(9) J / h

Assuming, enough air supply for complete combustion of pure carbon to CO2,

Energy released upon combustion = 32.8MJ / kg - carbon

Total energy released on an hourly basis = 120 * 32.8 MJ/h = 3.936*10^(9) J

If 100% energy circulation efficiency is attainable, then the combustion energy can suffice for maintaining the operational temperature in the fast-pyrolysis furnace.

If 50% energy is lost, energy utilised from combustion = 1.968*10^(9)J/h

This value is actually greater than the energy required for operation.

Hence, no further means are necessary for maintaining operational temperature even when 50% energy is lost in the process.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.