Page 335 - Advances in Eco-Fuels for a Sustainable Environment

290 Advances in Eco-Fuels for a Sustainable Environment

In Eqs. (10.11), (10.12), Cost HTL is the purchase cost of the HTL reactor in US$ at the
reference year of 2006, the constant numbers of 13,000, 34,000, and 0.5 are the Towler
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and Sinnot correlation cost constants, V R is the volume of the HTL reactor in m , _ m dig:
is the mass flow rate of the digestate specified as 5000tons per year or 694.4kg per h,
t T is the total residence time (heating time+holding time) required for a complete con-
version of digestate in h, and ρ dig. is the density of the digestate specified to be
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1020kg/m . The constant value of 1.5 is the factor used in converting the purchase
cost of a reactor made using carbon steel to the purchase cost of a reactor made using
high pressure-resistant (321) stainless steel.
In addition to the purchase cost of the HTL reactor vessel, additional purchase cost
components will include the cost of acquiring a high pressure pump. The high pressure
pump is used to provide the required high pressure in the HTL reactor. The purchase
cost of the high pressure pump (Cost p ) was subsequently estimated as follows [59],

0:7
Cost p ¼ 920 + 600S p (10.13)
where Cost p is the purchase cost of the pressure pump in US$ at the reference year of
2006, the constant numbers of 920, 600, and 0.7 are Towler and Sinnot correlation cost
constants, and S p is the estimated power consumed by the pump in kW.
As stated previously in the study of Jones et al. [11], large-scale HTL product
recovery is achieved easily by exploring the differences in the immiscibility and sur-
face properties of the insoluble solids, hydrophobic biocrude, and the polar post-HTL
water. Clearly, the gas phase product is easily separated from the product mixture.
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A simple tank of volume 100m has been assumed to be sufficient to facilitate gravity
separation of the products. The large volume of the tank has been specified to facilitate
the settling of large masses of the insoluble solids over time. The purchase cost of the
tank (Cost ST ) has been estimated as follows [59],

0:7
Cost ST ¼ 5700 + 700V ST (10.14)
where Cost ST is the purchase cost of the tank in US$ at the reference year of 2006, the
constant numbers of 5700, 700, and 0.7 are Towler and Sinnot correlation cost con-
3
stants, and V ST is the volume of the tank in m .
The purchase cost in the present year of 2018 for the ith equipment in
US$ (Cost i,2018 ) has been estimated by utilizing the literature-derived chemical
engineering plant cost index for reference year 2006 and for the present year 2018,
as follows [59],

CEPCI 2018
Cost i,2018 ¼ Cost i,2006 (10.15)
CEPCI 2006
where CEPCI is a dimensionless parameter specified as the chemical engineering
plant cost index that is used to account for the effect of annual inflation on costing
estimates. The values for CEPCI 2018 and CEPCI 2006 are specified for the year
2018 and the reference year 2006, respectively, and are obtained from literature