Biodiel production from waste cooking oil:2.Economic
asssment and nsitivity analysis
黑崎一护图片Y.Zhang a ,M.A.Dub e a ,D.D.McLean
a,*
,M.Kates
b
a
Department of Chemical Engineering,University of Ottawa,Ottawa,Ont.,Canada K1N 6N5
b
Department of Biochemistry,University of Ottawa,Ottawa,Ont.,Canada K1N 6N5Received 18March 2002;received in revid form 12May 2003;accepted 13May 2003
怎样克服紧张Abstract
The economic feasibilities of four continuous process to produce biodiel,including both alkali-and acid-catalyzed process,using waste cooking oil and the Ôstandard Õprocess using virgin vegetable oil as the raw material,were assd.Although the alkali-catalyzed process using virgin vegetable oil had the lowest fixed capital cost,the acid-catalyzed process using waste cooking oil was more economically feasible overall,providing a lower total manufacturing cost,a more attractive after-tax rate of return and a lower biodiel break-even price.On the basis of the economic calculations,nsitivity analys for the process were carried out.Plant capacity and prices of feedstock oils and biodiel were found to be the most significant factors affecting the economic viability of biodiel manufacture.
Ó2003Elvier Ltd.All rights rerved.
Keywords:Biodiel;Economic asssment;After-tax rate of return;Break-even price;Sensitivity analysis
1.Introduction
Exploring new energy resources,such as biodiel fuel,is of growing importance in recent years.Biodiel,derived from vegetable oil or animal fats,is recom-mended for u as a substitute for
petroleum-bad diel mainly becau biodiel is a renewable,domestic resource with an environmentally friendly emission profile and is readily biodegradable.The u of biodiel as a fuel has been widely investigated.Its commercial u as a diel substitute began in Europe in the late 1980s.
At prent,the most common way to produce bio-diel is to transterify triacylglycerols in vegetable oil or animal fats with an alcohol in the prence of an al-kali or acid catalyst.Methanol is the commonly ud alcohol in this process,due in part to its low cost.The products,fatty acid methyl esters (FAME),are called biodiel and include glycerine as a by-product.Alkali-catalyzed transterification has been most frequently ud industrially,mainly due to its fast reaction rate.Sodium hydroxide or potassium hydroxide is the usual
alkali catalyst.In contrast,acid-catalyzed transterifi-cation has received less attention becau it has a rela-tively slow reaction rate.Nevertheless,it is innsitive to free fatty acids in feedstock oil compared to the alkali-catalyzed system.The typical acid catalyst ud in the reaction is sulfuric acid.
防控措施
Compared to petroleum-bad diel,the high cost of biodiel is a major barrier to its commercialization.It costs approximately one and a half times that of pe-troleum-bad diel depen
摩羯和白羊
ding on feedstock oils (Pro-kop,2002;Lott,2002).It is reported that approximately 70–95%of the total biodiel production cost aris from the cost of raw material;that is,vegetable oil or animal fats (Krawczyk,1996;Connemann and Fischer,1998).Therefore,the u of waste cooking oil should greatly reduce the cost of biodiel becau waste oil is available at a relatively low price.
In a previous study,four different process flowsheets for producing biodiel from virgin vegetable oil or waste cooking oil by alkali-or acid-catalyzed tran-sterification were developed (Zhang et al.,2003).A comparison of the process was prented from the point of view of their process technology.The results showed that the acid-catalyzed process from waste cooking oil was potentially a competitive alternative to the commonly ud alkali-catalyzed process.Besides the
*
Corresponding author.Tel.:+1-613-562-5800x6110;fax:+1-613-562-5172.
E-mail address:mclean@genie.uottawa.ca (D.D.McLean).0960-8524/$-e front matter Ó2003Elvier Ltd.All rights rerved.
doi:10.1016/S0960-8524(03)00150-0
Bioresource Technology 90(2003)
229–240
technological evaluation,economic feasibility is also of great importance in asssing process viability.Thus,the main objective of the prent article is to asss the process on an economic basis.In this way,a better evaluation of the biodiel production process will be achieved from both the technological and economic points of view.In addition,a nsitivity analysis of each process is prented to identify the major factors af-fecting the economic viability of biodiel production.
Throughout this article,monetary values are ex-presd in US dollars.
2.Background
2.1.Economic studies
In previous economic studies of biodiel production, the main economic criteria were capital cost,manufac-turing cost and biodiel break-even price.Results of three recent studies are given in
Table1.Nelson et al. (1994)evaluated the economic feasibility of a plant producing approximately100,000tonne/year of bio-diel.Beef tallow was transterified with methanol in the prence of an alkali catalyst.Noordam and Withers (1996)carried out an economic study on a biodiel plant with a capacity of approximately7800tonne/year biodiel.Canola ed was ud as the raw material. Canola meal produced from ed crushing was a valu-able by-product,providing a credit of$2.3million.The estimated equipment cost for the transterification fa-cility was$695,656.With respect to the transterifica-tion unit,no detailed description of the process flowsheet or equipment sizing was provided.Other ex-pens,such as the costs of supervision,patents and royalties,and rearch and development,were not taken into consideration in their study.Bender(1999)com-pared ven biodiel plants using different , soybean ed,canola ed,sunflower ed and rapeed) or animal fats as the raw material.The capital cost and break-even price of biodiel for each process were de-termined.The results for one plant are provided in Table1.A glycerine credit was estimated bad on the specification of glycerine.The overall operating costs for each process were provided,but scale-dependent ex-pens,such as maintenance costs,utility cost and waste disposal fees,were not described.
In the economic studies mentioned in the preceding paragraph,detailed descriptions of the proces
s evalu-ated were not provided nor were details of their eco-nomic evaluations.Also,most publications have been related to the u of various oileds or animal fats as the raw material.To our knowledge,no economic studies on acid-catalyzed process using waste cooking oil as the feedstock have been reported to date.In ad-dition,different rearchers ud different economic criteria to asss the biodiel plant.Total capital cost was ud by Nelson et al.(1994),whereas total biodiel ,total manufacturing cost)was ud by Noor-dam and Withers(1996)to reprent the economic performance of the plant.Capital equipment cost was ud as an economic evaluation criterion by Bender (1999).In the prent article,the economic criteria were bad onfixed capital cost,total manufacturing cost, after-tax rate of return and break-even price for bio-diel.
2.2.Sensitivity analysis
The economic performance of a biodiel ,fixed capital cost,total manufacturing cost,and the break-even price of biodiel)can be determined once certain factors are identified,such as plant capacity, process technology,raw material cost and chemical costs.However,the effects of the factors on the eco-nomic viability of the plant are also of concern.A n-sitivity analysis involves measuring the relative magnitudes of the effects.This will also provide fur-ther information for the optimization of biodiel pro-duction.
Korus et al.(1993)studied an alkali-catalyzed batch transterification of rape oil with methanol or ethanol
Table1
Economic evaluations for biodiel production plants
Nelson et al.(1994)Noordam and Withers(1996)Bender(1999)a
Plant capacity100,000tonne/year7800tonne/year10,560tonne/year
Process type Alkali-catalyzed continuous
process
Alkali-catalyzed batch process Alkali-catalyzed continuous process Raw material Beef tallow Canola oiled Animal fats
Total capital cost$12million Not reported$3.12million
Total manufacturing cost$34million$5.95million Not reported
Biodiel break-even price$340/tonne$763/tonne$420/tonne
Glycerine credit$6million($600/tonne)$0.9million($1450/tonne glycerine)$1.2million for technical grade
glycerine($1470/tonne);$0.72mil-
lion for crude glycerine($660/tonne)
a Only results for one of the biodiel plants evaluated is reported here.
230Y.Zhang et al./Bioresource Technology90(2003)229–240
on the laboratory scale.They concluded that the cost of feedstock oil played a significant role in determining the economic viability of the biodiel process.Similarly, Nelson et al.(1994)commented that the significant factors affecting the cost of biodiel were feedstock cost,plant size and glycerine by-product value.A price nsitivity analysis was performed by Noordam and Withers(1996).The variables were restricted to the costs of raw material and ,prices of canola ed,canola meal and glycerine).By varying the value of one variable while keeping the others unchanged,its effect on the break-even price of biodiel was studied. Noordam and Withers(1996)r
eported that,on average, a$0.01/kg increa in the canola ed cost would in-crea biodiel price by$0.03/kg.A$0.11/kg increa in glycerine price would reduce the biodiel price by$0.01/ kg.Becau other factors,such as the ones related to process operation,were not considered,the results from such an analysis cannot be generally applied to other biodiel plants.
On the whole,nsitivity analys of biodiel pro-cess have not been ud widely and only a limited number of factors have been examined.In other words, there is a lack of quantitative nsitivity analys on the impact of a wide range of factors,such as all the possible chemical prices and variables related to operating con-ditions.Conquently,in the prent work,nsitivity analys of the alkali-and acid-catalyzed process using waste cooking oil as the raw material were performed. The goal was to t up an empirical model describing the relationship between the input ,prices of raw materials and products,plant capacity,product purities,etc.)and the output ,economic criteria).By evaluating the sizes of parameters in the empirical model,plotting residuals and testing the model adequacy,the physical significance of each effect and the nsitivity of process economics to changes in the input factors were identified.
3.Process descriptions
Four different continuous process to produce bio-diel from virgin oil or waste cooking oil were designed and simulated using HYSYS TM.Flowsheets and tech-nological asssments of the process were provided by Zhang et al.(2003).The process were the focus of the economic evaluation in the prent investigation.A brief description of each process follows.
Process I was an alkali-catalyzed process to produce biodiel from virgin vegetable oil.Virgin oil and a mixture of methanol and sodium hydroxide were fed into a transterification reactor.After the reaction(at 60°C and400kPa),an effluent stream containing FAME,glycerol,methanol,unconverted oil and sodium hydroxide entered a methanol distillation column where most of the methanol was recovered in a distillate stream.The distilled methanol,mixed with a fresh methanol stream,was recycled to the reactor.The methanol column bottom stream pasd to a column for water washing to parate the FAME from glycerol, sodium hydroxide and methanol.FAME,along with unconverted oil,some water and methanol,was then forwarded to a distillation column to further remove methanol and water.From the top of that column, >99.6wt.%(purity)FAME was obtained as a distillate. The bottom stream from the water-washing column, containing sodium hydroxide,glycerol,methanol and water,entered a neutralization reactor to remove so-dium hydroxide by adding phosphoric acid.After the sodium hydroxide was removed,the stream went into a glycerine purification column where the b
ottom stream yielded approximately85or92wt.%glycerine as a high quality by-product depending on the extent of the dis-tillation of methanol and water.
In process II,waste cooking oil was ud as the feedstock oil to produce biodiel in the prence of an alkali catalyst.Due to the nsitivity of the alkali-cata-lyzed reaction to free fatty acids found in waste oil,an esterifi,pretreatment)unit was required prior to the transterification unit to reduce the content of free fatty acid.Unrefined waste cooking oil,methanol and sulfuric acid were fed into the esterification reactor to reduce the free fatty acid content to the required level (<0.5wt.%).The effluent stream from this reactor was nt to a liquid extraction column.Using pure glycerine as a solvent,the refined cooking oil was parated from the resulting glycerol solution of methanol,water and sulfuric acid.Then,the refined cooking oil,together with the fatty acid esters produced,entered the tran-sterification reactor.The bottom stream from the liquid extraction column contained methanol,glycerol,water and sulfuric acid,and proceeded to a distillation column for methanol recovery.The other parts of this process were the same as tho in process I.
Process III was an acid-catalyzed process using waste cooking oil.Two transterification reactors operating in ries were required to deal with the high molar ratio (100.1)of methanol to oil.Neutralization of the acid catalyst in process III followed methanol distillation to reduce the costs o
f material of construction in the down-stream process units.The material of construction for the transterification and neutralization reactors and the methanol distillation column was stainless steel becau of the prence of sulfuric acid.As for the other units,there was little difference between process I and III.
Process IV was similar to process III,except that hexane was ud as an extraction solvent rather than water washing to avoid the formation of emulsions. After methanol distillation,an amount of hexane,equal in volume to the amount of methanol in the feed stream, and10vol.%of water(bad on the methanol amount)
Y.Zhang et al./Bioresource Technology90(2003)229–240231
were added to an extraction unit,where all the FAME and unconverted oil were extracted by hexane and p-arated from most of the glycerol,sulfuric acid and methanol.After further methanol/water washing of the hexane pha,no glycerol or sulfuric acid remained in the FAME and hexane stream.Hexane was recovered by distillation,and FAME was distilled as the biodiel product.Other parts of the process were the same as in process III.
Zhang et al.(2003)concluded that the acid-catalyzed continuous process to produce biodiel from w
aste cooking oil was a competitive alternative to the alkali-catalyzed process from a technological viewpoint.The logical next step involves economic studies and nsi-tivity analys of the process.
4.Economic asssment
4.1.Basis and scope of calculations
Economic evaluations were bad on the following assumptions:(1)Each process was bad on a plant capacity of8000tonne/year biodiel.This was the same size as an existing plant in Europe(Connemann and Fischer,1998)and was consistent with plant sizes dis-cusd previously(Zhang et al.,2003).In the following nsitivity analys,two other levels of plant capacity, one at4000and the other at12,000tonne/year were considered.(2)Operating hours for the biodiel plant were assumed to be8000h/year.(3)Both waste cooking oil and virgin oil,ud as the feedstock for biodiel production,are free of water and any solid impurities. The prices of the raw material oil include costs associ-ated with impurity removal and transportation.(4)In the simulation,pump efficiency was assumed to be70%. This was ud to determine the pump shaft power.A 90%motor efficiency was ud to calculate the electricity usage.Although a spare pump is usually required in a
chemical plant design,no spare pumps were taken into account in this work.(5)Superheated,low and high-pressure steams were ud as the heating media.Water was the cooling medium.Their specifications and prices are listed in Table2.(6)All costs shown are in US$. Equipment prices were updated from available mid-1996 to2000values using the Chemical Engineering Plant Index,where I2000¼394and I1996;MID¼382(Turton et al.,1998;Chemical Engineering,2001).(7)All chemical costs including raw materials,catalysts,solvent and products are given in Table2.
Table2
Basic conditions for the economic asssment of each process
Item Specification Price($/tonne)a
Chemicals a
Biodiel600
Calcium oxide40
Glycerine92wt.%1200
85wt.%750红梅的诗句
Hexane USD410
Methanol99.85%180
Phosphoric acid Tech.340
Sodium hydroxide NF/FC4000
Sulfuric acid98%60
Virgin canola oil500
Waste cooking oil200
Utilities b
羽五行
Cooling water400kPa,6°C$0.007/m3
Electricity$0.062/kW h
Low pressure steam(superheated)450kPa,210°C 6.8
High pressure steam(superheated)2700kPa,500°C10
Waste treatment
Liquid Hazardous150
Solid37
Plant capacity8000tonne/year biodiel
Thermodynamic model in process simulation NRTL or UNIQUAC
Methanol recovery in T-20194%
FAME purity99.65wt.%
Methanol recovery in the pretreatment unit94%
a Unless specified,all prices are in US$/tonne.Chemical prices are from National Biodiel Board,20
00,,Chemical Market Reporter(2000–2001),vol.258(22),vol.259(9)and ,November2000.
b Bad on the price in mid-1996provided by Turton et al.(1998)and updated to the year2000.
232Y.Zhang et al./Bioresource Technology90(2003)229–240
Due to the polar nature of many streams,both the non-random two liquid(NRTL)and universal quasi-chemical theory(UNIQUAC)thermodynamic/activity models were ud in the process simulations.This al-lowed the impact of the choice of thermodynamic/ac-tivity model to be evaluated.HYSYS TM simulations of each process design provided mass and energy balances and operating conditions for each piece of equipment (Zhang et al.,2003).This information was the basis for determining the size of the process equipment in the flowsheets.Straightforward non-iterative calculations (Lin et al.,1973;Sinnott,1999)were ud for deter-mining the equipment sizing,as discusd in detail by Zhang(2002).Results for sizing the main equipment of each process in ca1are shown in Table3.
According to the definition of capital cost estimation provided by Turton et al.(1998),the economic estima-tion in this article is classified as a‘‘study estimate’’.It is bad on the development of a proce
ssflow diagram and rough sizing of major process equipment.No further information,such as a layout plot,process instrumen-tation diagram or piping and instrumentation require-ments,were considered.Turton et al.(1998)stated that this study estimate had a range of expected accuracy from+30%to)20%.Thus,results from such a pre-liminary evaluation may not accurately reflect thefinal
Table3
Equipment sizes,equipment costs andfixed capital costs for ca1(85%glycerine byproduct using NRTL)
Type Description Process I Process II Process III Process IV Reactors Esterification
Size,(DÂL,m)00.8·2.400
Cost,($·10À3)80
Transterification
Size,(DÂL,m) 1.8·5.4 1.8·5.4 2.1·6.3a 2.1·6.3a
Cost,($·10À3)290290673a673a
Neutralization
Size,(DÂL,m)0.3·10.3·10.5·1.50.4·1.2
Cost,($·10À3)21213829
Columns Methanol distillation
Size,(DÂH,m)0.6·101·121·101·10
0.6·10
Cost,b($·10À3)140357324324
140
Washing column
Size,(DÂH,m)0.8·101·101·101·10
0.8·100.8·10
Cost,($·10À3)100240109240
100220
FAME distillation
Size,(DÂH,m) 1.2·12 1.2·121·12 1.5·16c
Cost,b($·10À3)157157168256c
Glycerine purification
Size,(DÂH,m)N/A0.5·100.6·100.8·10
Cost,b($·10À3)106135145
Heat exchangers,cost($·10À3)4161212
Pumps,cost($·10À3)45724049
Others(parator,vacuum system),cost($·10À3)46577342
宽带号码在哪看Total basic module cost($·10À6),C BM00.61 1.10 1.01 1.19
Total bare module cost($·10À6),C BM0.81 1.64 1.57 1.99 Contingency fee($·10À6),C CF¼0:18C BM0.140.290.280.36
Total module cost($·10À6),C TM¼C BMþC CF0.95 1.94 1.85 2.35行进管乐
Auxiliary facility cost($·10À6),C AC¼0:3C BM00.220.390.360.42
Fixed capital cost,C FC($·10À6),C FC¼C TMþC AC 1.17 2.33 2.21 2.77
Working capital($·10À6),C WC¼0:15C FC0.170.350.330.42
Total capital investment($·10À6),C TC¼C FCþC WC 1.34 2.68 2.55 3.19
a Includes two reactors operated in ries.
b Includes the overhead condenr,recycle pump and bottom reboiler.
c Includes hexane distillation.
Y.Zhang et al./Bioresource Technology90(2003)229–240233
