053 Cost-Estimation Methods for Drying.pdf

53 Cost-Estimation Methods for Drying

Zbigniew T. Sztabert and Tadeusz Kudra

CONTENTS

53.1 Introduction ....................................................................................................................................... 1247

53.2 Free-on-Board Cost and Installed Cost of the Equipment ................................................................ 1247

53.3 Fixed Cost .......................................................................................................................................... 1252

53.4 Variable Cost ..................................................................................................................................... 1252

53.5 Drying Cost Estimate: A Worked Example ....................................................................................... 1255

Summary ...................................................................................................................................................... 1258

Acronyms ..................................................................................................................................................... 1258

References .................................................................................................................................................... 1258

53.1 INTRODUCTION

Cost components of drying are usually divided

into the following two groups:

Reliable estimates of the ﬁxed capital investment (FCI)

of a drying system as well as the system’s ﬁxed and

operating costs are essential in the preliminary equip-

ment selection or when comparing different competing

systems. In general, estimation of the costs involved in a

drying process follows the well-known methods used

widely in the process industries [1–9]. This chapter pro-

vides the empirical information on shortcut methods

that may be used to quicken the predictions of FCI and

operating costs on the basis of the previously prepared

process balances and one-parameter equipment sizing.

The method described here is useful for preparing the

rough cost estimates applicable to many conventional

drying systems. However, extending this information to

unique or newest methods of drying must be regarded

with caution. When capital cost estimates of a deﬁnitive

investment are required to obtain budget authorization,

competitive quotes from vendors have to be requested,

as these quotes are the most reliable estimates.

A dryer itself is only one component of the overall

drying system. The systemmay comprise preprocessing

equipment (extruders, grinders, mixers, and blenders),

feeders, product-discharge devices, and postprocessing

equipment such as gas cleaners (cyclones, ﬁlters, and

scrubbers) and solvent-recovery systems (condensers

and separators). In some cases, heat-recovery systems

(exhaust-gas recycle, run-around coil, heat pump, or

heat wheel) may also be used. Thus, drying systems

for the same end product can be different. Therefore,

the total ﬁxed costs as well as the operating costs should

be calculated for the complete drying system.

1. Fixed costs (ﬁxed charges), which are incurred for

alongperiodoftime,tendtobeunaffectedby

ﬂuctuations in the level of production activity.

They include: depreciation of equipment and

buildings, interest charges for the investment cap-

ital, plant protection, insurance, ﬁxed part of

taxes and rents, ﬁxed part of maintenance costs,

and executive salaries (administration, overhead).

2. Variable costs (operating costs) tend to vary

with the production level. They include: cost

of raw materials, cost of product degradation,

costs of energy and utilities, direct labor (oper-

ating, works transport, supervision, and la-

boratory control), interest on working capital,

royalties, variable part of maintenance costs,

and miscellaneous direct costs.

The estimation process of drying costs is schemat-

ically shown in Fi gure 53.1 . The foll owing is a

detailed presentation of the method for preliminary

estimates preparation, together with a worked ex-

ample of cost estimates.

53.2 FREE-ON-BOARD COST AND

INSTALLED COST OF THE EQUIPMENT

Equipment-price data concern the free-on-board

(FOB) cost and the installed cost of the equipment.

The installed cost of a drying system covers the cost

2006 by Taylor & Francis Group, LLC.

Drying system

version

Calculations:

1. Mass and heat

balances

2. One-parameter

equipment sizing

Prediction of plant cost:

1. FOB cost of equipment

2. Installed cost of system

3. Total direct cost of system

4. Fixed capital investment

Preliminary

estimation of fixed

and variable costs

of drying

FIGURE 53.1 The steps of preliminary estimation of drying cost.

of the pur chased equipment , co st of equipment instal-

lation, and costs of piping, wiring, and instrumentation.

These costs can be estimat ed on the basis of ven dors’

data or, with less a ccuracy, on the basis of known

costs for the equipment or syst em bui lt previous ly,

assum ing a great de gree of simila rity.

Data for equ ipment costs obt ained from techni cal

literatu re are usuall y ba sed on the techni cal an d e co-

nomic cond itions of the pa st. Among the various

methods accounti ng for price chan ges due to inﬂation

and inevi table ﬂuctuat ions in econ omic condition s,

the method of the Chem ical Engineer ing Pl ant Cost

Index (based on the 1957/ 1959 cost level and ab bre-

viated as CE Index) and the method of the Marshal l

and Swi ft All-I ndustry Equip ment Cost Index (for -

merly known as the M arshall an d Stevens Ind ex) a re

the mo st commonl y used. This last inﬂation index

(formula ted in the US market in the year 1926 wi th

the set value of 1 00, and ab breviated as M&S Ind ex)

is recomm ended for updating the costs of high-l evel

process eq uipments [4,10]. The upda ted M &S Index

as well as the CE Index are listed regularly in Chem -

ical Eng ineering , a periodi cal publish ed by McGra w-

Hill, New York [11] , and are valid for cost upda ting

in US$ and for the US market. A part of such listing

for the equipment -cost indice s over the pe riod 1989–

2004 is given in Tabl e 53.1. The followi ng formu la

using M&S Index is wid ely acc epted for equipment -

cost upda ting:

different capacity can be predict ed approxim ately

from the followin g emp irical correl ation:

Predicted cost ¼ Original cost

[desired capacity = original capacity] n

(53 : 2)

where desir ed capacity is the capacit y of the eq uip-

ment for whi ch the cost is to be estimat ed and origi nal

capacity is the capa city of the same- type equ ipment

for whi ch the cost is known (original cost). Val ues of

the exp onent n for the typic al equipment used in

drying systems are lis ted in Table 53.2 [10]. If not

given he re or in the refer ence literat ure (e.g ., [4,13]) ,

n ¼ 0.6 can be taken for rou gh estimat ion. The expo -

nent n may vary with the design detai ls. For exampl e,

in the case of cloth dust collectors, n ranges from 0.70

to 0.86. The cost estimated according to Equation

53.2 must be corrected not only for the inﬂation

index according to Equation 53.1 but also for the

TABLE 53.1

Marshall and Swift All-Industry Equipment Cost

Index and Chemical Engineering Plant Cost Index

(1989–2004)

Year M&S

Index

CE Index Year M&S

Index

Updated cost ¼ Original cost

1989

895.1

355.4

1997

1056.8

386.5

1990

915.1

357.6

1998

1061.9

389.5

M&S Index at updated time

M&S Index at the time of original cost

(53 : 1)

1991

930.6

361.3

1999

1068.3

390.6

1992

943.1

358.2

2000

1089.0

394.1

1993

964.2

359.2

2001

1093.9

394.3

1994

993.4

361.1

2002

1104.2

395.6

The M&S Index an d the CE Index c an also be used

for world-pr ice c omparison , if the changes in costs

accordi ng to the local eco nomics , type of indust ry,

and kind of equipment (besi des time) a re accounted

for [12] .

For scale -up or scale -down of the drying syst em,

the cost of the equipment of the same type but of

1995

1027.5

381.1

2003

1123.6

402.0

1996

1039.2

381.7

2004

1178.5

444.2

Source: Marshall and Swift Equipment Cost Index. Chem. Eng.,

last pages of every issue (excerpted by special permission from

Intelligence, New York, NY 10038).

2006 by Taylor & Francis Group, LLC.

TABLE 53.2

Typical Expo nents Re lating Equ ipment Cost

to Capa city

Asi de from the general form ula, numerous da ta

on dryer cost depen dence on ev aporation capacity

exist in literat ure for the given dryers and deﬁ nite

operatin g parame ters [13, 21,22]. For exampl e, co st

of a spray dryer with a pr essure nozzle atomi zer,

residen ce time of 16 s, inlet- and outlet-ai r tempe ra-

ture of 538 an d 121 8 C, respectivel y, can be calcula ted

as [21] :

Equipment

Capacity Range Unit Exponent

Centrifugal fan

0.4–40 m 3 /s

0.44

Cyclone

0.01–4

m 3 /s

0.61

Multiple cyclone

4–94 m 3 /s

0.66

Dust collector (cloth)

1–470 m 3 /s

0.78

Price ¼ 13793 : 8

E 0 : 435 (first-qu arter-199 5 US $)

Electrostatic precipitator

23–470 m 3 /s

0.74

(53 : 4)

Gravity spray scrubber

0.7–189 m 3 /s

0.66

Venturi scrubber

3.3–38 m 3 /s

0.46

Impingement scrubber

1–23 m 3 /s

0.78

where E is the evaporat ive load (181 < E < 38,780

kg/h) and the price includes the 304-stai nless steel

dryer body , the access platform , support steel , bur ner,

air-heate r shell, feedi ng system, and instrument ation.

Insula tion, refractor y mate rial, fan, a nd soli ds-rec ov-

ery syst em a re not included.

The ab ove method of prices present ation is

restricte d to a na rrow range of technol ogy. Taking

into accoun t that dryer cost de pends mainl y on its

size and the material of constr uction, drying indice s

such a s dryer through put, evaporat ion rate, or unit

heat co nsumpt ion shou ld not be used as parame ters

for cost estimat ion, mainl y be cause the same indice s

may be obtaine d for dryers of different size by

manipul ating the ope rating condition s. This situ ation

changes when a contrac t relating to techn ology and

equipment is consider ed—then a depen dence of dry er

cost on evaporat ion capacit y can be a valuabl e criter-

ion for dryer selection.

The best charact eristic parame ters for preli minary

cost esti mation of most dryers a re:

Centrifugal scrubber

3.3–47 m 3 /s

0.73

Ribbon blender a

0.2–7

m 3

0.54

Cage-type disintegrator

0.3–6

kg/s

0.68

Roll crusher

3–66

kg/s

0.97

Screen (vibrating)

0.2–6

m 2

0.66

Bucket elevator a

3–50 m 0.52

Belt conveyor a

5–19 m 2

0.50

Screw conveyor b

0.4–0.8 m 2

0.53

Pan dryer

1–19 m 2

0.50

Vacuum-shelf dryer

1.4–92 m 2

0.54

Tunnel dryer

2–10 m 2

0.50

Roto-Louvre rotary dryer

4–93 m 2

0.62

a Carbon steel.

b Stainless steel, conveyor length diameter.

Source: Sztabert, Z.T., in A.S. Mujumdar, Ed., Drying of Solids,

Sarita Prakashan, New Delhi, 1990, pp. 136–153.

local eco nomic situati on when install ation will be

erected in a cou ntry other than the United State s

[14]. Plavsic [12] has given a num ber of useful refer -

ences [15–20 ] and pr ovided a simp liﬁed ‘‘direct fact or-

ing’’ method for convert ing the US data to numb ers

that are applic able elsewhere . Howe ver, furt her dis-

cussio n of this aspect is beyond the scope of this

chapter .

Ver y app roximate co st of carbon steel dryers can

be calculated as [4]

. The volume of the drying chamber (e.g., for

spray or rotar y dryers )

. The surface area of the suppo rting grid, shelve s,

belt con veyors etc.

. The heat- transfer area in case of co ntact dryers

Usually, the estimat ed fabricati on cost of a dryer can

be calculated from the follo wing correlati on:

C ¼ (M& S Index) 30 þ 36 : 74

(17 : 77 þ T )

(53 : 3)

P ¼ (M& S Index) A Q c

(US$ in the year of M &S Index)

(53 : 5)

where C is the installe d cost (US$ in the year of the

M&S Index) cov ering the dr yer and auxil iaries, includ-

ing foundati ons and erection, but no secondary dus t

collectors or buildin g; W is the evapo ration capacit y,

kg mois ture/h; and T is the inlet-ai r temperatur e ( 8 C).

This relation, howeve r, does not reﬂect the material

propert ies, so the calculated prices are unde restima ted.

The graphs accordi ng to Equation 53.3 are presen ted

in Fig ure 53.2 for the M&S Index equal to 1100.

where Q is the capacit y of a dryer deﬁ ned eithe r by its

effecti ve volume (V ) or by its characteris tic surface

area (S ), de pending on the dryer type. Valu es of the

coefﬁci ent A and expo nent c for some common

dryers , determ ined from the available cost data, a re

listed in Tabl e 53.3 .

The fabricatio n co st of a drying unit besides its

size dep ends also on the mate rial of co nstruc tion; it is

the lowest for carbo n steel. If the process requir es a

2006 by Taylor & Francis Group, LLC.

320,000

270,000

W =20 kg/h

W =100 kg/h

220,000

W =500 kg/h

170,000

120,000

70,000

20,000

100

130

160

200

250

300

T , ( C)

FIGURE 53.2 The dependence of dryer cost on evaporation capacity in kg moisture/h and inlet-air temperature in 8C,

according to Equation 53.3 (M&S Index ¼ 1100).

TABLE 53.3

Param eters A and c in Eq uation 53.5 for Selected Dry ers

Dryer Type

Capacity Range

Parameter

Construction

Equipment Included

A c

Cabinet (atmospheric)

16 < V < 160

7 0.50 Aluminum

Heater, instrumentation

Cabinet (low vacuum)

5 < V < 30

18 0.62 Aluminum

Heater, instrumentation, vacuum pump

Vacuum with unheated agitator 0.02 < V < 9

66 0.30 Carbon steel

Vacuum with unheated agitator 0.02 < V < 9

103 0.42 304-stainless steel

Vacuum double-cone tumbler

0.1 < V < 14

80 0.70 304-stainless steel

Indirect rotary (steam tube)

3 < V < 300

55 0.58 Carbon steel a

Instrumentation

Drum (single or double)

1 < S b < 40

21 0.50 Cast iron

Drive, fan

Belt conveyor (through-ﬂow)

18 < S c < 50

21 0.59 304-stainless steel Drive, fan, steam heater

Direct rotary, ﬂue-gas heated

20 < S < 300

17 0.68 Carbon steel d

Drive, burner, heat exchanger, fan, dust

collector, instrumentation

Direct rotary, hot-air heated

20 < S < 300

14 0.66 Carbon steel d

Drive, burner, heat exchanger, fan, dust

collector, instrumentation

Fluid bed (batch)

0.003 < V e < 0.66 141 0.47 304-stainless steel Heater, fan, ﬁlter, instrumentation

Spray

1 < V < 300

47 0.52 304-stainless steel Heater, atomizer, fan, ﬁlter,

instrumentation

Vibrated bed

1 < S f < 12

9 0.70 Carbon steel g

a For 304-stainless steel, cost is multiplied by 1.7.

b Drum peripheral surface area.

c Deck surface area.

d For 304-stainless steel, cost is multiplied by 1.5.

Bed volume.

Surface area of vibrated grid.

g For 304-stainless steel, cost is multiplied by 1.64.

Note: Dryer capacity is deﬁned by dryer volume V in m 3 or surface area S in m 2 .

2006 by Taylor & Francis Group, LLC.

more chemical- resistant material, a claddin g may be

applie d in so me cases. In certain drying operatio ns,

optimu m de sign of the equipment as well as pro duct-

quality requ irements calls for the use of not only more

durable but also more expensi ve material s. In general ,

drying equipment built of 304-stai nless steel typic ally

costs from 1.5 to 1.7 tim es more than that made of

carbon steel and 2 to 3 times more if built of titanium .

The co st depen ds also on the au xiliary e quipment ,

and this is a reason for some uncerta inty in co st

predict ion from literat ure sources withou t vend ors’

data. Figu re 53.3 present s, as an exampl e, the pur -

chase co st for severa l dryers in relat ion to their ca p-

acity that is updated to the yea r 2000 wi th the M&S

Index equal to 1089.

Once the FOB costs of all equipment compri sing

the drying syst em are establ ished, the install ed cost

and other costs of the plan t, as well as ﬁxed costs , can

be estimat ed us ing the factor method of cost estima-

tion. Usually, the follo wing co mponents of inst alled

cost are consider ed:

. Equip ment delivered without piping and in-

strumen tation—71 to 99% of FOB cost

3. Freight (funct ion of trans port method, weight,

and dist ance, or 7% of [componen t 1 þ com-

ponent 2])

The total direct co st of the plant ex pressed in

terms of the ‘‘batter y limit s’’ is much higher than the

install ed cost of the equ ipment becau se of addition al

costs such as

. Buildi ngs, laborat ories , wareh ouses

1. If a dryer syst em is inst alled insid e a build-

ing, the cost of the bui lding is fact ored in as

20 to 35% of the inst alled cost.

2. If a dryer system is outsi de of the buildin g,

the cost of the building is factored in as 1 5%

of the inst alled cost.

. Utility-supply facilities, site development,

other direct expenses (20 to 40% of the in-

stalled cost).

1. FOB cost (vendo rs’ prices or estimat ed prices)

2. Assembly, piping, wiring, instrumentation using

vendors’ data, or the following factors:

. Fully eq uipped compact syst em—25 to 3 0%

of FOB cost

. Fully equipped syst em, deliv ered in many

parts —40 to 45% of FOB cost

To roughly estimate the total direct cost of the dry-

ing installation, it is recommended to multiply the

equipment FOB cost by a factor of 2.25 if the equip-

ment is made of carbon steel or by 2.75 if stainless-steel

equipment is used [22]. These ﬁgures include the cost of

piping, instrumentation, electrical connections, insula-

tion, building space, and engineering when applied to

1,000,000

800,000

600,000

400,000

200,000

100

120

(m 3 )

FIGURE 53.3 FOB costs (US$, in the year 2000) vs. dryer volume in m 3 of selected dryers according to Equation 53.5 : 1,

atmospheric cabinet dryer (aluminum); 2, vacuum cabinet dryer (aluminum); 3, spray dryer fully equipped (304-stainless

steel); 4, steam tube rotary dryer (carbon steel) with instrumentation; 5, vacuum dryer with unheated agitator (304-stainless

steel); 6, double-cone tumbler dryer (304-stainless steel).

2006 by Taylor & Francis Group, LLC.

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