Guthrie Method

The Guthrie method has the option to calculate the cost for a complete plant or
only for a particular team, since the total cost is conceptually divided into
modules. The modules cover smaller parts of the project, facilitating the final calculation of
cost. Within the process equipment module, Guthrie presents a series of cost data that
they allow estimating the installed costs of a large number of equipment for chemical processing. A
the following presents the most general way to estimate the installed cost of equipment within
this section.
1. The base cost is obtained (Cbbased on one or more design variables of the equipment to
estimate. Such design variables can be a dimension or consequence of the
dimensions specific to the equipment, e.g., for heat exchangers the area is used of
exchange, for pressure vessels their dimensions (diameter and height) and for the
Distillation columns use dimensions and the number of trays. The base costs
they are presented graphically and represent the costs in mid-1968, for equipment to
the conditions of the standard module; moderate pressure, specific geometry and material
carbon steel type.
2. The f.o.b. cost of the equipment is calculated (Cfob) adjustment factors are used to match the
standard module to the team that wishes to estimate, along with an equation that provides
Guthrie to make the adjustments. The equation depends on the equipment and involves the base cost.
3. The estimation is finalized through a series of equations that provide the final cost.
of the module. First, the cost of the bare module for the base year is calculated (Cmd) using the
next expression
C md=C b∗F

Where F represents the bare module factor of Guthrie. Subsequently, it is calculated the
cost of the bare module (Cmodfor the year that is wanted to be scaled, through the following
expression:
C mod=C md +( Cfob−C b )

Finally, a 15% contingency is added to the cost value of the module.

nude of the current year, to obtain the total cost of the module (Cm).
C m=1.15−Cmod

4. The bare module factor includes all direct and indirect cost modules and is
used as a multiplier of the equipment cost. It is a measure of the dollars required
to integrate the piece or the multiple pieces of the equipment within a process circuit in
particular. That is, the modulus factor includes the cost of equipment and material of
construction along with the costs of labor and the indirect materials needed
to install the equipment. Since Guthrie's equations include a calculation for the
cost of equipment, the values for the bare module factor are based by definition
in the cost of the equipment. Therefore, a lower factor of the unit would indicate an unrealistic situation
that the total cost of the equipment once installed is less than the manufacturing cost of the
equipment plus that of the construction material.
Cost of the distillation plant:
Distillation column
For the calculation of this cost, the equations proposed by Guthrie for the containers will be applied.
under pressure. First, the arrangement of the container must be selected, in this case the arrangement is
vertical.
The expression that will be used for the calculation of the base cost is the following

L D
CB=C 0
( )( )∗
L0 α D 0 β

The reference values C0 L0, D0, and for this expression, they appear in a table, as well as the
exponents to which the quotients must be raised.

Cost for reboiler and condenser

Design equation to find the area

Where:

=Á

∆ = Logarithmic media

The temperature values for the cooling water y they must have at least one

difference of 77 °F and the temperature values for the heating steam y ) inside
of the range regarding the type of exchange that will be used.

The value for the overall heat transfer coefficient is obtained from tables regarding the type

of fluids used in the exchanger

 Cost of the operation.
When using the Guthrie method to calculate the cost of equipment, it must be specified for the
year in which the estimate is made, reported in tables in the literature.

Guthrie method for heat exchangers.

ln = 1 + 2 ln( )+ [ln(
3 )]2

The values of the constants vary depending on the type of heat exchanger being used.
employed and are reported in tables in the literature.

The value for the index of 1968 is 113.7.

Index year that will carry out the estimation

Cfob=Cb(Fd+ Fp)Fm
( Index or 1968 )
Cmd=3.39Cb

Cmda=Cmd+(CFob−Cb)
Module cost equation

Cmodule=1.15∗Cmda
 Cost of the column and plates
Guthrie method for columns.

log = +
1 log(
2 )+ 3[log( )]2

The values of the constants vary depending on the design of the column to be used and
they are reported in tables in the literature.

Index year that the estimate will be made

Cfob=Cb(Fd+ Fp)Fm
( Index 1968 )
Cmd=3.39 Cb

Cmda=Cmd+(CFob−Cb)
Module cost equation

Cmodule=1.15∗Cmda

Cost of services
For the calculation of the Cp of the vapor using the following equation:
Cp=a+bT+ c T 2+ d T 3

The following formulas were used for these costs:

Cagua=Q∗( for sale)∗(Operation time) /(CP∗D e l t a T )

Cvapor=Q∗( for sale)∗(Operation time)/(CP∗D e l t a T )

= +

The costs of steam and cooling water must be searched for in the same region so that only
Thus, the estimation of the method is valid.

With the data from the following table, calculations were made in the document for the cost of
distillation process:

Column Extractive Recovery

Food flow (kmol/h) 100 53.137
 Solvent flow (kmol/h) 40 0
Distillate flow (kmol/h) 86.864 13.156
Molar fraction of ethanol in the distillate 0.9957 0
Temperature of food (°C) 78.2 130.2
Solvent temperature (°C) 80 ________
Molar reflux ratio 0.35 0.05
Number of theoretical stages 18 6
Food stage 10 4
Pressure (mmHg) 760 15
Solvent food stage 3 ________
Solvent/food relationship 0.4 0
Energy consumption (kj/kg ethanol) 1249 224

Results:

RR Condemned heat Heat Reboiler

Extractive Column 0.4 -1205 1249
Recovery column 1.33 -201 224

Stages Diameter (f) Spec. Platters Plate Height ( ſt)

Extractive Column 18 2.81 2 16 32
Recovery column 6 16.89 2 4 8

Condemned area Area Cb Cb Fp Fp

(ſt) reboiler (f) condenser reboiler condenser reboiler
Extractive Column 0.104831 0.108659 0.023493 0.024047 1 1
Recovery column 0.017486 0.019487 0.007334 0.007869 1 1

F
m Cmd Cfob Cdma Conden Command Cfob Cdma Creboiler
1 0.07729 0.1214871 0.1752876 0.2015807 0.0791171 0.124352 0.179421 0.206335
1 0.02413 0.0379285 0.0547251 0.0629339 0.0258920 0.040695 0.058717 0.067525

Vapor Water
Cp steam cost Cp water cost Cost of
 $/year $/year services
Extractive Column 3.38E+01 1.08E+01 3.37E+01 0.0358 10.8
Recovery column 3.38E+01 1.94 0.00597 1.94

Column
Area Cost VAPOR
Column Cb C teams $/lb Water $/lb
Extractive Column 282.4926 174532.12 349064.24 34906.4656 0.003 0.00001438
Column of
recovery 424.4929 261620.93 523241.86 52324.1991 0.003 0.00001438

Total cost
Extraction Column 34920
Recovery column 52330
87240
Total

Salazar, J. (2001). Design of Heat Transfer Equipment. Autonomous University of Nuevo

Lion

Seider, W. Equipment Sizing and Capital Cost Estimation. University of Pennsylvania.

Philadelphia