Calculation of Drying Costs

Calculation of Drying Costs

Fall Meeting of the NEKDA, 3-4 November 2010

Shelburne, New Hampshire

Yves Fortin

Facult? de foresterie, de g?ographie et de g?omatique

Universit? Laval

Contents

? Introduction ? Energy consumption ? Drying cost components ? Excel spreadsheets ? Case studies ? How to reduce drying costs ? Conclusions

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Introduction

Why to calculate drying costs?

? to help choosing a new drying installation ? to determine the real cost of drying for an

existing intallation ? to determine custom drying rates ? to determine actions to take to reduce

drying costs

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Introduction (cont?)

How to determine drying costs?

? Feaseability study (capital investment decisions): net present value of investment (NPVI: capital

outlays ? cash inflows), internal or discounted rate of return (IRR or DRR) (ref. Engalichev and Eddy 1970)

? Calculation of the various cost components:

calculation of drying costs at a given time, not taking into account cash inflows and time value of money (Goulet and Ouimet 1970, McMillen and Wengert 1978, Hukka 2001, Chanrion et al. 1989)

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INTRODUCTION (cont')

The calculation of drying costs involves first the calculation of energy consumption

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INTRODUCTION (cont')

Kiln drying is a very demanding energy process

Balsam fir drying from 100% to 15%: 100 MBF, 2''x4''x8' 56 000 kg H2O 1.09 kWh/kg H2O 61 040 kWh (208 millions BTU) 1-year bungalow consumption: 100 millions BTU

N.B. 1 kWh= 3 421 BTU

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Energy consumption Excel spreadsheet

Input data

9 Wood species and lumber dimensions

9 Geometry of kiln and lumber stack 9 Characteristics of equipment 9 Initial and final moisture contents 9 Conditions of exterior climate 9 Drying schedule 9 Drying curve

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Energy consumption Excel spreadsheet

Sources of energy consumption (at the kiln only)

Heating and humidification of

incoming air Q6

Heating and evaporation of water from wood

Q5

Heating of residual water

after drying Q4

Differential heat of sorption Q3

Heat loss through kiln walls, roofs and floor

Q7

Fan motors Q8

Heating of kiln and equipment

Q1

Heating of lumber Q2

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Drying cost Excel spreadsheet

Input data

9 Geometry of kiln and lumber stack 9 Characteristics and costs of kiln and storage equipment 9 Initial and final moisture contents 9 Kiln operation capacity and number of kilns 9 Process efficiency 9 Labor salaries 9 Kiln startup factor (1.2 -1.5) 9 Other various costs and rates (stickers, fuel, taxe and interest rates,

etc.)

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Drying costs Excel spreadsheet

Cost components

? Fixed costs

9

Equipment, buildings and stickers (depreciation)

9

Interest on investment

9Insurances (kilns, equipement, buildings, lumber)

9Administration (office costs attributed to drying)

9Taxes (land, buildings, lumber, yard facilities)

9Interest on lumber inventory and land

9Maintenance of yard and snow removal

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