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The Technology Efficiency Index: A method for measuring process technologies
TECHNOLOGICAL
FORECASTING
AND SOCIAL CHANGE
35.5 142
(1989)
The Technology Efficiency Index: A Method for Measuring Process Technologies BEN0 ZAIDMAN
and GUIDO CEVIDALLI
ABSTRACT
A method for measuring technologies to be applied in the chemical processing industries is proposed. A Technology Efficiency Index (TEI) is established. This index is based on factors objectively measurable, in terms of characteristics of processes like stochiometric ratio, maximum temperature, number of stages, etc. The data necessary for the TEI are available at each stage of the innovation. Examples of application of TEI to existing industrial technologies in the area of basic organic chemicals are presented. In the examples quoted, a good agreement between the TEI value of a technology and its industrial fate has been found.
Introduction The problem of measuring technologies in order to compare them, or to forecast
their evolution over a period of time, is often debated in specialized literature (see the recent issue of this journal almost entirely devoted to this subject) [ 11. The methodologies proposed for the technology measurement include scoring models [2], constrained scoring models [3, 41, trade-off between technical parameters’ surfaces [5, 61, and objective sectorial functions [7]. All of the above methodologies have in common the fact that they characterize a technology by the performance of the yielded output (produce or service) as expressed by a technical parameter or by a cluster of parameters. Those methodologies have not been successfully applied to chemical processes as explicitly stated by Ayres [7], and is implicitly indicated by the failure to apply Gordon’s method to coal gasification 141. The failure of the output-performance oriented methodologies in the chemical-process industries (CPI) is, in our opinion, because of a structural incompatibility between them and the CPI rather than a flaw of the methodologies. A significant proportion of the technological change generated by the CPI, especially in the basic industries, is aimed at improving the pathway to the desired chemical species rather than the modification of the output products. For example, the basic organic chemical industry has recorded tremendous technical changes in the last 50 years; however, it continues to produce basically the same chemical products that remain the building blocks of the entire organic chemical industry. BEN0 ZAIDMAN is senior research engineer at the Casali Institute of Applied Chemistry, School of Applied Science and Technology, The Hebrew University of Jerusalem, Jerusalem, Israel. GUIDO CEVIDALLI is Professor Emeritus at the Hebrew University of Jerusalem, Jerusalem, Israel. Address reprint requests to Dr. Beno Zaidman, Casali Institute of Applied Chemistry, School of Applied Science and Technology, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
0 1989 by Elsevier Science Publishing
Co., Inc.
0040-1625/89/.$03.50
52
B. ZAIDMAN AND G. CEVIDALLI
GENERAL APPROACH
We propose in this article a different approach to the methodology of technology measurement to be applied in the CPI. This method defines a technology efficiency index (TEI) as a function of the input resources consumed in a production process. This index is a dimensionless number ,of merit. It is not a quantitative independent measurement of the economic efficiency of a technology, but instead it furnishes a tool for a preliminary comparison between two or more technologies yielding the same product. The area of relevance of TEI is limited to chemical-process technologies. Our methodology requires the definition of some preliminary terms. In this context, a technology is considered efficient when it utilizes the minimum resources for performing a chemical transformation of an initial material (the feedstock) in a new material (the desired commercial product). The term productive resources refers to the primary form of production factors before their translation into monetary units. By substituting the monetary costs with physical measures of productive resources as a means of evaluating economic efficiency, a general validity is conferred to the proposed methodology. A comparison of two technologies that yield the same product can be schematically shown as below, in eq. (1). efficiency
of technology,
> efficiency
of technologyz
(la)
or technology
efficiency
index, > technology
efficiency
index,
(lb)
when x
resources used in technology,
< 2
resources used in technology,
(lc)
The term resources refers to the primary form of production factors before their translation into monetary units. By avoiding the use of costs, a general validity is confered to the proposed methodology. The transformation of a material in an industrial-chemical process uses the following resources: feedstocks, capital (land and physical investment), energy and labor (direct, indirect, and knowledge). The choice of those resources has been suggested by the analysis of the economic structure of the chemical-process industries in which the above-quoted production factors play the dominant part. A technological concept is defined by the way it combines the above resources for obtaining the desired product. PRESENTATION OF METHODOLOGY
In order to build an operative expression for TEI, we sought coefficients that are proportional to one or more of the resources. The value of the TEI is then a function of those coefficients, as shown in eq. (2): TEI = f (raw materials coef.; capital coef.; labor coef.; energy coef.)
(2)
This function, which is somehow similar to the “production function” used by the economists, may be of various forms, from a simple addition of terms to a complex mathematical expression. We will adopt a function in which TEI is equivalent to the product of the proportionality coefficients and some constant, as shown in eq. (3):
53
THETECHNOLOGYEFFICIENCYINDEX
TEI = K X (raw mat. coef.
X capital coef. x labor coef.
x energy coef.)
(3)
The adoption of such an expression is motivated by observation of the structure of the process industries, which shows that the utilization of the resources is interconnected, and a limited trade-off between them is possible. Therefore, the amount consumed from one resource affects in some proportion the quantity of one or more of the other resources in the process. This linkage between the resources is best expressed, in our opinion, by a function in which the different terms are multiplied. This opinion is strengthened by a number of empirical expressions, with a good statistical relevance, used for assessing the value of one cost component of the chemical production process as a function of other cost components and of the size of the production system. Such formulae are quoted in literature for fixed investment [8, 91 and energy and labor costs [lo]. These formulae have the form of a multiplication of terms, their general expression being the following: [cost of resource
l] = K. [cost of resource 21”. [cost of resource 31b...
(4)
where the exponential values a and b appear in order to satisfy a quantitative correlation. These formulae express relationships between use of resources and present similarities with the formula sought by us for TEI. In order to evaluate the appropriate proportionality coefficients, for the different resources, one can use a scoring model in which the different characteristics of a technology receive numerical scores. In this type of model, the different alternatives are ordered on the basis of the sum (or product) of the specific scores. As this type of model can introduce a degree of subjectivity, we use, for the building of the TEI, technological factors objectively measurable such as temperature, pressure, and matter ratio, among others. The first resource dealt with is the chemical matter or the feedstock. As we intend to measure the efficiency of a technological concept rather than a defined industrial process, we will not use here the yield or conversion ratio. We express the efficiency of a technology in the use of chemical matter by the ratio between the sum of molecular weight of the raw materials and the sum of molecular weight of products. This approach confers to the method general applicability in the chemical processing industry and is preferable, in our opinion, to the use of the fate of one chemical element as a measure of the efficiency of the feed stock utilization, as proposed, e.g., by Rudd [ll]. c matter ratio (MR) =
molecular x
weight raw materials
molecular
weight products
(5)
In this context, raw materials are those commercial products+hemical comodities-that directly participate in the chemical reaction. One must emphasize that those raw materials that are practically “free of charge” as atmospheric air and water are not reckoned with when the value of MR is sought. In the modem social framework, the efficiency of a technology in using the chemical matter cannot be separated from the separation of environment-disturbing wastes, which must be treated (inside or outside the plant) before their emission into the external environment. This treatment implies use of resources by the industry or by the public, which reduce the benefit brought up by the products manufactured in the process. This
54
B. ZAIDMAN
AND G. CEVIDALLI
aspect is reckoned with by the introduction of a penalty factor composed of a subunitary multiplier (w) and the molecular weight of the wastes generated by the technology. The ecologic weighted matter ratio (EWMR) has the form: 2
molecular
weight of raw material
EWMR = IX mo 1ecu 1ar weight products
-
w. x
molecular
weight of wastes (6)
The multiplier w must reflect the loss in efficiency due to the need for processing wastes; therefore, w is expressed as shown in eq. (7):
w=
environmental production
outlays of an industrial costs of an industrial
the
sector
sector
(7)
The numerical values of this ratio for the chemical processing industries converge in the range of 0.03-0.05 [12-141. As an average value for w, we adopt 0.04. Other values can be used in specific cases, depending on specific local conditions or industrial branches. The determination of the proportionality coefficient for capital, energy, and labor is a more difficult task because of the high degree of interconnection between these resources. The coefficient chosen by us to express the use of capital is the number of technological steps on which the technological concept is based. This coefficient is similar to the concept of the functional unit used in some shortcut methodologies for capital izvestment evaluation [lo]. We distinguish between the steps in which a chemical transformation is made (the equivalent of a unit process in the language of the industrial chemist) and those in which only a physical change occurs (the equivalent of a unit operation). We believe that the character of a technological concept to be applied in the chemical processing industries is structured ultimately by the chemical transformation that it provides. For this reason, we differentiate between these two types of technological steps and use the following expression for the coefficient for capital utilization: CUC=N+a*n
(8)
where CUC N n a
= = = =
coefficient number of number of subunitary
of capital utilization unit processes unit operations multiplier
For the chemical processing industries, we have found, after some trials and errors, that 0.5 is a convenient value for a. The CUC coefficient reflects also the degree of utilization of labor (direct and indirect), and we will not introduce a supplimentary term for this resource. One can resume the role of energy in the chemical process industries to the following tasks: 0 To drive the flow of materials
along the process path
THE TECHNOLOGY
EFFICIENCY
55
INDEX
To bring the different materials to the most adequate physical form for each technological step. 0 to bring the materials to optimum conditions for performing the chemical transformation (including the energy required for endothermic reactions). l
The use of energy in the first two tasks is proportional to the number of technological steps and is represented by the previously discussed terms (eq. 8). The coefficient for the last use of the energy is a parameter F,, some way similar to an expression proposed for the evaluation of the complexity of chemical processes [ 151. The structure of the term F, is defined by eq. (9): F
c
=
l(,‘F,+F~+Fe)
(9)
The weighted factors F,, Fp, and F, express the operating conditions imposed by the technological concept (maximum temperature t,,, “C; maximum pressure P, atm and the enthalpy of reactions (AZf, KcaVmol). The following equations are employed: F, = 1.8(t,,,-27)10-4 F,=O.l
[15]
(lOa)
log P, [15]
(lob)
(1Oc)
F, = 0.05 log CAH
After definition of all the proportionality coefficients for the resources to be used, the next step in our methodology draws the general form of the TEI function. The term efficiency has a positive connotation, and the increase in the efficiency of a technology must be reflected by an increase in the numerical value of TEI. Since an increase in the value of the terms EWMR, CUC, and F, brings about a decrease in the efficiency of a technological concept, TEI has the following form: TEI = K. EWMR-‘.
CUC-‘.
F c-1
(11)
where K is the proportionality constant. The constant K is given the value 100, so that for an “ideal” technology, the TEI will be 100. In an “ideal” technology, one unit of raw material is transformed to one unit of product (EWMR = l), in one unit process (N = 1) without any unit operation (n = 0) at room temperature (F, = 0), atmospheric pressure (F, = 0) without application of external energy (F, = 0). One must emphasize the fact that the only aim of this form of presenting the TEI is the convenience of the user, and no absolute meaning is claimed for the numerical values, which only serve as a tool for comparing different technological concepts. In order to facilitate the understanding of the TEI index and to demonstrate its relevance, the equations developed were used in a trial TEI analysis of technologies already applied in the CPI. The results were then compared to the actual industrial fate of the various technologies. The information needed for the calculation of the TEI values for the processes quoted by us in this article have been obtained from open industrialchemistry literature, especially from Kirk-Othmer’s Encyclopedia of Chemical Technol-
56
B.ZAIDMAN AND G.CEVIDALLI
ogy, which, in its three editions, (1947-1985).
covers nearly half a century of development
in this area
PHENOL-ACASESTUDY As a first excercise, the TEI values of various technological concepts in the manufacture of phenol were determined. Phenol was chosen because there are at least five well documented, industrial processes for its production. The five technologies chosen are as follows: 0 Sulfonation of benzene, followed by melt caustification of the sulfonic acid and acidification of sodium salt. 0 Hydrolysis of chlorobenzene followed by acidification. 0 Oxychlorination of benzene followed by steam hydrolysis-the Rashig process, l Peroxidation of cumene and cleavage to phenol and acetone. 0 Oxidation of toluene followed by decarbonylation. The data used and the steps of calculation following:
1. 2. 3. 4. 5.
appear in Table 1, and the results are the
Process
Year of Introduction
TEI
Benzene sulphonate Chlorobenzene Oxychlorination Cumene oxidation Toluene oxidation
1910-1915 1925 1935 1955 1960
4.01 6.69 24.15 22.85 33.45
which has practically disappeared, for the The first generation of technologies, production of phenol have a very low TEI value relative to the later generations. The superiority of the oxychlorination concept, which assures a maximum utilization of the raw materials, is expressed by a big increase in TEI. The cumene oxidation technology in which phenol and acetone are produced simultaneously was industrially introduced about 15 years after the oxichlorination and is the dominant present technology for the production of phenol together with the oxidation of the toluene. The TEI of cumene oxidation technology (22.85) is similar to the index of the oxychlorination technology (24.15), and the success of the former cannot be explained by a first TEI analysis. However, when considering the operations of a petrochemical complex producing both phenol from benzene via oxychlorination and acetone from a C3 hydrocarbon in two separate processes, and applying the TEI concept to both these technologies (see Table lb, cases 6a and 6b), one realizes that the alternative cumene technology is more efficient in TEI terms than the two separate technologies that it has replaced. (TE&,e,, = 22.86; TEI_,u,ated = 16.72). The toluene oxidation represents an improvement relative to the cumene process, but again, as in the preceeding argument (see Table lb, cases 7a and 7b), when the separate production of the phenol from toluene and of acetone from C3 hidrocarbon is considered, the TEI of the cumene technology is superior to the cumulate index of the separate technologies. The toluene oxidation process has replaced the cumene process in those industrial environments where the market ratio between the phenol and the acetone does not coincide with the technological ratio.
4.12 2.42 1 1 0.98
Matter Ratio EWMR
1 0.72 0.88
2 1 3
PThe synthesis of cumene is comprised.
oxidation) 250 120 250
425 120 425
oxidation)
300 360 425 120 250
(tm; “C)
Temperature Maximum
and propylene
and propylene 1 1 2
2 1 3
1
1
3 2 2
(n)
Unit Operation
Numberof
(benzene oxychlorination
3 2 2 3 2
(N)
Number of Unit Process
1 .c: Manufacture of phenol and acetone by distinct process (toluene oxidation 7a Phenol by toluene oxidation 0.98 2 7c Acetone by propylene oxidation 0.72 1 la + lb 0.88 3
6a Phenol by benzene, oxychlorination 6b Acetone by propylene oxidation 6a + 6b
of phenol and acetone by distinct processes
Benzene sulfonation Chlorobenzene hydrolysis Benzene oxychlorination Cumene oxidation” Toluene oxidation
1 .b: Manufacture
1. 2. 3. 4. 5.
Concept
of phenol [16-181
Technological
1 .a: Manufacture
No. of Case
TABLE 1 Manufacture of Phenol-Technology Efficiency Index Values PreSSUR?.
(P,,
3 12 12
5 12 12
1 350 5 5 3
atm.)
Maximum
1.40
1.51
1.119 2.06 1.38 1.25 1.22
WC)
Complexity Factor
20.2
16.72
4.82 6.69 24.15 22.86 33.45
Technology Efficiency Index
_
Ammonia + Benzene Du Pont process
1.02
1.19
-1965
1970
1.23
3.12
- 1958
Like la with utilization of iron oxide as pigment Nitrobenzene reduction (hydrogen; catalytic; gas phase) Bayer-Allied process Ammonolysis of phenol gas phase Halcon-Scientific Design process
Ib
0.84
-1860
Nitrobenzene reduction (iron and acid) Bechamp process
la
EMWR
2
I .5
I.5
2.5
2.5
CUC
Fc
2.02
2.00
1.16
1.04
1.04
Resource Coefficients
-1860
Year
Technological
Concept
NO. of Case
Manufacture
24.24
28.01
46.5
45.8
12.33
TEI Value
100
-
90
IO
-
90
10
-
Early 1980s
o/o of Total
Mid- 1960s
Installed Capacity
Values [19-211
Before 1950
TABLE 2 of Aniline-TEI
No commercial
1985--commercial use
Observations
in Japan?
Technological
Concept
Ethylene cyanohidrin” Cyanamid process Hydrocyanic ac. addition to acetaldehyde” Hydrocyanic ac. addition to acetylene Amoxidation of propylene (as SOHIO orocess)
“The synthesis of hydrocyanic
4.
3.
2.
1.
No. of Case
acid (by Andrussow
1960-1962
1940-1942 1940 Germany 1952 (?1940 Germany)
Year
2.5
3.5
3.5
3.5
CUC
Fc
1.19
.496
.49
,496
Coefficients
30.25
17.2
13.2
13.2
TEI Value
TABLE 3 of Acrylonitrile-TEI
process) is comprised.
1.11
1.11
1.45
1.45
EMWR
Resource
Manufacture
-
-
100
Before 1950
11
72
17
-95
-5
-
Early 1980s
% of Total
Mid- 1960s
Installed Capacity
Values [22-24
Not commercial
Observations
60
B. ZAIDMAN
AND G. CEVIDALLI
OTHER EXAMPLES
The relevance of the TEI concept was confirmed by more applications to industrial technologies. The TEI analysis of the manufacture of aniline is presented in Table 2. The first industrial process, nitro-benzene reduction (case la), is obsolete, with the exception of those situations in which the by-product, iron oxide, finds a utilization (case lb). This situation is clearly expressed by the respective TEI values. The dominant process today (95% of the installed capacity) is the catalytic reduction of nitrobenzene, and it has the highest TEI value. Two relatively new technological concepts (cases 3, 4) have not found a fully commercial application. From Table 2, it appears that the high value of the complexity factor F, for these later processes lowers their TEI values. In Table 3 the different processes for the manufacture of acrylonitrile are presented. The first three processes (cases l-3), based on the addition of the hydrocyanic acid to C2 speciae, have low TEI value due to the extreme reaction conditions and have practically no present commercial application. The technological superiority of the SOHIO process (amoxidation of propylene, case 4) finds a good expression in its TEI value. About 95% of the acrylonitrile is produced today by the SOHIO process. Table 4(aac) presents the TEI values of the principal processes for the manufacture of phtalic anhydride, ethylene oxide, and maleic anhydride. The corelation between the TEI values and the diffusion of the technologies is evident in all the three cases. It appears that, at least in the above analyzed cases, there exists a clear concordance between the TEI classification of a technological concept and its industrial fate. Conclusions and Comments A quantitative method for measuring the technological efficiency of concurrent processes in the chemical processing industries has been developed. The methodology uses factors objectively measurable in terms of technical characteristics of the processes. The data necessary for the use of the methodology are available at each stage of the innovation process. The relevance of the method is demonstrated by its successful application in the evaluation of processes for the production of phenol, aniline, acrylonitrile, and others. When the possibility of using the proposed method as a tool for a preliminary evaluation of research projects is examined, the fact that this approach does not take into consideration the prices of the process constituents raises some questions as to its validity. The good agreement between the TEI values calculated and the development and difusion of the CPI innovations indicates that the TEI can be used as an evaluation tool at the preliminary conceptual stage. Does this really mean that a sound and efficient “technological concept” may be independent from the vagaries of the economic and political environment, as reflected by the changing prices of the various resurces? Is such a measure of the efficiency of a technological concept more meaningful than economic indicators established in a defined time frame? In a long-term perspective, the answer is probably yes, but in the short-time approach, the harsh day-to-day reality cannot be ignored. References 1. Technological Forecasting and Social Change, 27, (1985). 2. Delaney, Charles L., Technology Forecasting: Aircraft Hazard Determination, Technological Forecasting and Social Change, 5. 249-252 (1973). 3. Gordon, J. T., and Manson, R. T., A Proposed Convention for Measuring the State of the Art of Products or Processes, Technological Forecasting and Social Change. 20, 1-26 (1981). 4. Edwards, K. L., and Gordon, J. T., Further Research into a Convention for Measuring the State of the Art of Products or Processes, Technological Forecasting and Social Change, 24, 153-175 (1983). 5. Dodson, E. N., A General Approach to Measurement of the State- of the Art and Technological Advance, Technological Forecasting and Social Change, 1, 391408 (1970).
Concept
[31-331
1. Benzene oxidation 2. Butane dehydro-oxidation 3. Butene oxidation
4c. Maleic anhydride
1 Chlorohydrine 2. Oxidation of ethylene
4b. Ethylene oxide [28-301
1. Naphtalene oxidation 2. 0-xylene oxidation (liquid phase; catalyzated)
[25-271
Technological
4a. Phtalic anhydride
No. of Case
-1957 1975 1975
1925 -1960
1917-1920 1946
Year
Manufacture
0.79 0.59 0.57
4.08 1
0.86 0.71
EMWR
2 2 2
2.5 1.5
2.5 2.5
CUC
1.276 1.216 1.280
1.052 1.11
1.17 1.05
Fc
Resource Coefficients
49.6 69.69 68.53
9.3 60.0
39.75 53.53
TEI Value
TABLE 4 of Chemical Products-TEI
-
-
100 -
95 -
100
9.5 90.5
70 30
90 [34]
10
-2 -98
35 65
Early 1980s
% of Total
Mid- 1960s
Installed Capacity Before 1950
Values
Observations
62
B. ZAIDMAN
AND G. CEVIDALLI
6. Dodson, E. N., Measurement of Technology Usmg Trade-off Surfaces, Technological Forecasting und Social Change, 27, 1985). 7. Ayres, R. U., Empirical Measures of Technological Change at the Sectoral Level, Technological Forrcasting and Social Change, 27, 229-247 (1985). 8. Stalworthy, E. A., The Viewpoint of a Large Chemical Manufacturing Company, The Chemical Engineer, June, CE 182~CE 189 (1970). 9. Allen, D. H., Revised Techniques for Predesign Cost Estimating, Chemical Engineering, March 3. 142150 (1975). 10. Bridgewater A. V., The Functional Unit Approach to Rapid Cost Estimation, AACE Bulletin. October, 153-164 (1976). 11. Rudd, D. F., et al., Petrochemical Technology Assessment, John Wiley, New York, 1981, Chap. 2, pp. 35-72, Chap. 3, pp. 73-83. 12. James, D. E., et. al., Economic Approaches to Environmental problems, Elsevier, New York, 1978, p, 163. 13. Atkins, M., and Lowe, Y., Pollution Control Costs in Industry, Pergamon Press, U.K. 1977, p. 148. 14. Cevidalli, G., and Benedetti, L., Processi Chimici non Inquinanti, La Chimica e l’fndusrria, 53, U-53 (1971). 15. Cevidalli, G., and Zaidman, B., Evaluate Research Projects Rapidly, Chemical Engineering, July 14, 145-152 (1980). 16. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 1st Ed., Vol. 10, 1953. 17. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 15, 1968, pp. 147-159. 18. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 17, 1982, pp. 373-384. 19. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 1st Ed., Vol. 1, 1947, pp. 916-917. 20. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 2, 1969, pp. 41 l-426. 21. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 2, 1978, pp. 309-321. 22. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 1st Ed., Vol. 1, 1947, pp. 185-188. 23. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 1, 1963, pp. 338-351. 24. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 1, 1978, pp. 414-416. 25. Kirk, R., and Othmer, D., Encyclopedia ofChemical Technology, 1st Ed., Vol. 10, 1953, pp. 588-590. 26. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 15, 1953, pp. 444457. 27. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 17, 1982, pp. 732-746. 28. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 1st Ed., Vol. 5, 1950, pp. 320-325. 29. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 8, 1965, pp. 523-558. 30. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 9, 1980, pp. 43247 1. 31. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 1st Ed., Vol. 8, 1952, pp. 680-699. 32. Kirk, R., and Otbmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 12, 1967, pp. 819-834. 33. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 14, 1981, pp. 770-790. 34. Chowdhury, J., Maleic anhydride Manufacture, Chemical Engineering August 17, 29-33 (1987). Received 8 January 1988; revised 3 June 1988.
FORECASTING
AND SOCIAL CHANGE
35.5 142
(1989)
The Technology Efficiency Index: A Method for Measuring Process Technologies BEN0 ZAIDMAN
and GUIDO CEVIDALLI
ABSTRACT
A method for measuring technologies to be applied in the chemical processing industries is proposed. A Technology Efficiency Index (TEI) is established. This index is based on factors objectively measurable, in terms of characteristics of processes like stochiometric ratio, maximum temperature, number of stages, etc. The data necessary for the TEI are available at each stage of the innovation. Examples of application of TEI to existing industrial technologies in the area of basic organic chemicals are presented. In the examples quoted, a good agreement between the TEI value of a technology and its industrial fate has been found.
Introduction The problem of measuring technologies in order to compare them, or to forecast
their evolution over a period of time, is often debated in specialized literature (see the recent issue of this journal almost entirely devoted to this subject) [ 11. The methodologies proposed for the technology measurement include scoring models [2], constrained scoring models [3, 41, trade-off between technical parameters’ surfaces [5, 61, and objective sectorial functions [7]. All of the above methodologies have in common the fact that they characterize a technology by the performance of the yielded output (produce or service) as expressed by a technical parameter or by a cluster of parameters. Those methodologies have not been successfully applied to chemical processes as explicitly stated by Ayres [7], and is implicitly indicated by the failure to apply Gordon’s method to coal gasification 141. The failure of the output-performance oriented methodologies in the chemical-process industries (CPI) is, in our opinion, because of a structural incompatibility between them and the CPI rather than a flaw of the methodologies. A significant proportion of the technological change generated by the CPI, especially in the basic industries, is aimed at improving the pathway to the desired chemical species rather than the modification of the output products. For example, the basic organic chemical industry has recorded tremendous technical changes in the last 50 years; however, it continues to produce basically the same chemical products that remain the building blocks of the entire organic chemical industry. BEN0 ZAIDMAN is senior research engineer at the Casali Institute of Applied Chemistry, School of Applied Science and Technology, The Hebrew University of Jerusalem, Jerusalem, Israel. GUIDO CEVIDALLI is Professor Emeritus at the Hebrew University of Jerusalem, Jerusalem, Israel. Address reprint requests to Dr. Beno Zaidman, Casali Institute of Applied Chemistry, School of Applied Science and Technology, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
0 1989 by Elsevier Science Publishing
Co., Inc.
0040-1625/89/.$03.50
52
B. ZAIDMAN AND G. CEVIDALLI
GENERAL APPROACH
We propose in this article a different approach to the methodology of technology measurement to be applied in the CPI. This method defines a technology efficiency index (TEI) as a function of the input resources consumed in a production process. This index is a dimensionless number ,of merit. It is not a quantitative independent measurement of the economic efficiency of a technology, but instead it furnishes a tool for a preliminary comparison between two or more technologies yielding the same product. The area of relevance of TEI is limited to chemical-process technologies. Our methodology requires the definition of some preliminary terms. In this context, a technology is considered efficient when it utilizes the minimum resources for performing a chemical transformation of an initial material (the feedstock) in a new material (the desired commercial product). The term productive resources refers to the primary form of production factors before their translation into monetary units. By substituting the monetary costs with physical measures of productive resources as a means of evaluating economic efficiency, a general validity is conferred to the proposed methodology. A comparison of two technologies that yield the same product can be schematically shown as below, in eq. (1). efficiency
of technology,
> efficiency
of technologyz
(la)
or technology
efficiency
index, > technology
efficiency
index,
(lb)
when x
resources used in technology,
< 2
resources used in technology,
(lc)
The term resources refers to the primary form of production factors before their translation into monetary units. By avoiding the use of costs, a general validity is confered to the proposed methodology. The transformation of a material in an industrial-chemical process uses the following resources: feedstocks, capital (land and physical investment), energy and labor (direct, indirect, and knowledge). The choice of those resources has been suggested by the analysis of the economic structure of the chemical-process industries in which the above-quoted production factors play the dominant part. A technological concept is defined by the way it combines the above resources for obtaining the desired product. PRESENTATION OF METHODOLOGY
In order to build an operative expression for TEI, we sought coefficients that are proportional to one or more of the resources. The value of the TEI is then a function of those coefficients, as shown in eq. (2): TEI = f (raw materials coef.; capital coef.; labor coef.; energy coef.)
(2)
This function, which is somehow similar to the “production function” used by the economists, may be of various forms, from a simple addition of terms to a complex mathematical expression. We will adopt a function in which TEI is equivalent to the product of the proportionality coefficients and some constant, as shown in eq. (3):
53
THETECHNOLOGYEFFICIENCYINDEX
TEI = K X (raw mat. coef.
X capital coef. x labor coef.
x energy coef.)
(3)
The adoption of such an expression is motivated by observation of the structure of the process industries, which shows that the utilization of the resources is interconnected, and a limited trade-off between them is possible. Therefore, the amount consumed from one resource affects in some proportion the quantity of one or more of the other resources in the process. This linkage between the resources is best expressed, in our opinion, by a function in which the different terms are multiplied. This opinion is strengthened by a number of empirical expressions, with a good statistical relevance, used for assessing the value of one cost component of the chemical production process as a function of other cost components and of the size of the production system. Such formulae are quoted in literature for fixed investment [8, 91 and energy and labor costs [lo]. These formulae have the form of a multiplication of terms, their general expression being the following: [cost of resource
l] = K. [cost of resource 21”. [cost of resource 31b...
(4)
where the exponential values a and b appear in order to satisfy a quantitative correlation. These formulae express relationships between use of resources and present similarities with the formula sought by us for TEI. In order to evaluate the appropriate proportionality coefficients, for the different resources, one can use a scoring model in which the different characteristics of a technology receive numerical scores. In this type of model, the different alternatives are ordered on the basis of the sum (or product) of the specific scores. As this type of model can introduce a degree of subjectivity, we use, for the building of the TEI, technological factors objectively measurable such as temperature, pressure, and matter ratio, among others. The first resource dealt with is the chemical matter or the feedstock. As we intend to measure the efficiency of a technological concept rather than a defined industrial process, we will not use here the yield or conversion ratio. We express the efficiency of a technology in the use of chemical matter by the ratio between the sum of molecular weight of the raw materials and the sum of molecular weight of products. This approach confers to the method general applicability in the chemical processing industry and is preferable, in our opinion, to the use of the fate of one chemical element as a measure of the efficiency of the feed stock utilization, as proposed, e.g., by Rudd [ll]. c matter ratio (MR) =
molecular x
weight raw materials
molecular
weight products
(5)
In this context, raw materials are those commercial products+hemical comodities-that directly participate in the chemical reaction. One must emphasize that those raw materials that are practically “free of charge” as atmospheric air and water are not reckoned with when the value of MR is sought. In the modem social framework, the efficiency of a technology in using the chemical matter cannot be separated from the separation of environment-disturbing wastes, which must be treated (inside or outside the plant) before their emission into the external environment. This treatment implies use of resources by the industry or by the public, which reduce the benefit brought up by the products manufactured in the process. This
54
B. ZAIDMAN
AND G. CEVIDALLI
aspect is reckoned with by the introduction of a penalty factor composed of a subunitary multiplier (w) and the molecular weight of the wastes generated by the technology. The ecologic weighted matter ratio (EWMR) has the form: 2
molecular
weight of raw material
EWMR = IX mo 1ecu 1ar weight products
-
w. x
molecular
weight of wastes (6)
The multiplier w must reflect the loss in efficiency due to the need for processing wastes; therefore, w is expressed as shown in eq. (7):
w=
environmental production
outlays of an industrial costs of an industrial
the
sector
sector
(7)
The numerical values of this ratio for the chemical processing industries converge in the range of 0.03-0.05 [12-141. As an average value for w, we adopt 0.04. Other values can be used in specific cases, depending on specific local conditions or industrial branches. The determination of the proportionality coefficient for capital, energy, and labor is a more difficult task because of the high degree of interconnection between these resources. The coefficient chosen by us to express the use of capital is the number of technological steps on which the technological concept is based. This coefficient is similar to the concept of the functional unit used in some shortcut methodologies for capital izvestment evaluation [lo]. We distinguish between the steps in which a chemical transformation is made (the equivalent of a unit process in the language of the industrial chemist) and those in which only a physical change occurs (the equivalent of a unit operation). We believe that the character of a technological concept to be applied in the chemical processing industries is structured ultimately by the chemical transformation that it provides. For this reason, we differentiate between these two types of technological steps and use the following expression for the coefficient for capital utilization: CUC=N+a*n
(8)
where CUC N n a
= = = =
coefficient number of number of subunitary
of capital utilization unit processes unit operations multiplier
For the chemical processing industries, we have found, after some trials and errors, that 0.5 is a convenient value for a. The CUC coefficient reflects also the degree of utilization of labor (direct and indirect), and we will not introduce a supplimentary term for this resource. One can resume the role of energy in the chemical process industries to the following tasks: 0 To drive the flow of materials
along the process path
THE TECHNOLOGY
EFFICIENCY
55
INDEX
To bring the different materials to the most adequate physical form for each technological step. 0 to bring the materials to optimum conditions for performing the chemical transformation (including the energy required for endothermic reactions). l
The use of energy in the first two tasks is proportional to the number of technological steps and is represented by the previously discussed terms (eq. 8). The coefficient for the last use of the energy is a parameter F,, some way similar to an expression proposed for the evaluation of the complexity of chemical processes [ 151. The structure of the term F, is defined by eq. (9): F
c
=
l(,‘F,+F~+Fe)
(9)
The weighted factors F,, Fp, and F, express the operating conditions imposed by the technological concept (maximum temperature t,,, “C; maximum pressure P, atm and the enthalpy of reactions (AZf, KcaVmol). The following equations are employed: F, = 1.8(t,,,-27)10-4 F,=O.l
[15]
(lOa)
log P, [15]
(lob)
(1Oc)
F, = 0.05 log CAH
After definition of all the proportionality coefficients for the resources to be used, the next step in our methodology draws the general form of the TEI function. The term efficiency has a positive connotation, and the increase in the efficiency of a technology must be reflected by an increase in the numerical value of TEI. Since an increase in the value of the terms EWMR, CUC, and F, brings about a decrease in the efficiency of a technological concept, TEI has the following form: TEI = K. EWMR-‘.
CUC-‘.
F c-1
(11)
where K is the proportionality constant. The constant K is given the value 100, so that for an “ideal” technology, the TEI will be 100. In an “ideal” technology, one unit of raw material is transformed to one unit of product (EWMR = l), in one unit process (N = 1) without any unit operation (n = 0) at room temperature (F, = 0), atmospheric pressure (F, = 0) without application of external energy (F, = 0). One must emphasize the fact that the only aim of this form of presenting the TEI is the convenience of the user, and no absolute meaning is claimed for the numerical values, which only serve as a tool for comparing different technological concepts. In order to facilitate the understanding of the TEI index and to demonstrate its relevance, the equations developed were used in a trial TEI analysis of technologies already applied in the CPI. The results were then compared to the actual industrial fate of the various technologies. The information needed for the calculation of the TEI values for the processes quoted by us in this article have been obtained from open industrialchemistry literature, especially from Kirk-Othmer’s Encyclopedia of Chemical Technol-
56
B.ZAIDMAN AND G.CEVIDALLI
ogy, which, in its three editions, (1947-1985).
covers nearly half a century of development
in this area
PHENOL-ACASESTUDY As a first excercise, the TEI values of various technological concepts in the manufacture of phenol were determined. Phenol was chosen because there are at least five well documented, industrial processes for its production. The five technologies chosen are as follows: 0 Sulfonation of benzene, followed by melt caustification of the sulfonic acid and acidification of sodium salt. 0 Hydrolysis of chlorobenzene followed by acidification. 0 Oxychlorination of benzene followed by steam hydrolysis-the Rashig process, l Peroxidation of cumene and cleavage to phenol and acetone. 0 Oxidation of toluene followed by decarbonylation. The data used and the steps of calculation following:
1. 2. 3. 4. 5.
appear in Table 1, and the results are the
Process
Year of Introduction
TEI
Benzene sulphonate Chlorobenzene Oxychlorination Cumene oxidation Toluene oxidation
1910-1915 1925 1935 1955 1960
4.01 6.69 24.15 22.85 33.45
which has practically disappeared, for the The first generation of technologies, production of phenol have a very low TEI value relative to the later generations. The superiority of the oxychlorination concept, which assures a maximum utilization of the raw materials, is expressed by a big increase in TEI. The cumene oxidation technology in which phenol and acetone are produced simultaneously was industrially introduced about 15 years after the oxichlorination and is the dominant present technology for the production of phenol together with the oxidation of the toluene. The TEI of cumene oxidation technology (22.85) is similar to the index of the oxychlorination technology (24.15), and the success of the former cannot be explained by a first TEI analysis. However, when considering the operations of a petrochemical complex producing both phenol from benzene via oxychlorination and acetone from a C3 hydrocarbon in two separate processes, and applying the TEI concept to both these technologies (see Table lb, cases 6a and 6b), one realizes that the alternative cumene technology is more efficient in TEI terms than the two separate technologies that it has replaced. (TE&,e,, = 22.86; TEI_,u,ated = 16.72). The toluene oxidation represents an improvement relative to the cumene process, but again, as in the preceeding argument (see Table lb, cases 7a and 7b), when the separate production of the phenol from toluene and of acetone from C3 hidrocarbon is considered, the TEI of the cumene technology is superior to the cumulate index of the separate technologies. The toluene oxidation process has replaced the cumene process in those industrial environments where the market ratio between the phenol and the acetone does not coincide with the technological ratio.
4.12 2.42 1 1 0.98
Matter Ratio EWMR
1 0.72 0.88
2 1 3
PThe synthesis of cumene is comprised.
oxidation) 250 120 250
425 120 425
oxidation)
300 360 425 120 250
(tm; “C)
Temperature Maximum
and propylene
and propylene 1 1 2
2 1 3
1
1
3 2 2
(n)
Unit Operation
Numberof
(benzene oxychlorination
3 2 2 3 2
(N)
Number of Unit Process
1 .c: Manufacture of phenol and acetone by distinct process (toluene oxidation 7a Phenol by toluene oxidation 0.98 2 7c Acetone by propylene oxidation 0.72 1 la + lb 0.88 3
6a Phenol by benzene, oxychlorination 6b Acetone by propylene oxidation 6a + 6b
of phenol and acetone by distinct processes
Benzene sulfonation Chlorobenzene hydrolysis Benzene oxychlorination Cumene oxidation” Toluene oxidation
1 .b: Manufacture
1. 2. 3. 4. 5.
Concept
of phenol [16-181
Technological
1 .a: Manufacture
No. of Case
TABLE 1 Manufacture of Phenol-Technology Efficiency Index Values PreSSUR?.
(P,,
3 12 12
5 12 12
1 350 5 5 3
atm.)
Maximum
1.40
1.51
1.119 2.06 1.38 1.25 1.22
WC)
Complexity Factor
20.2
16.72
4.82 6.69 24.15 22.86 33.45
Technology Efficiency Index
_
Ammonia + Benzene Du Pont process
1.02
1.19
-1965
1970
1.23
3.12
- 1958
Like la with utilization of iron oxide as pigment Nitrobenzene reduction (hydrogen; catalytic; gas phase) Bayer-Allied process Ammonolysis of phenol gas phase Halcon-Scientific Design process
Ib
0.84
-1860
Nitrobenzene reduction (iron and acid) Bechamp process
la
EMWR
2
I .5
I.5
2.5
2.5
CUC
Fc
2.02
2.00
1.16
1.04
1.04
Resource Coefficients
-1860
Year
Technological
Concept
NO. of Case
Manufacture
24.24
28.01
46.5
45.8
12.33
TEI Value
100
-
90
IO
-
90
10
-
Early 1980s
o/o of Total
Mid- 1960s
Installed Capacity
Values [19-211
Before 1950
TABLE 2 of Aniline-TEI
No commercial
1985--commercial use
Observations
in Japan?
Technological
Concept
Ethylene cyanohidrin” Cyanamid process Hydrocyanic ac. addition to acetaldehyde” Hydrocyanic ac. addition to acetylene Amoxidation of propylene (as SOHIO orocess)
“The synthesis of hydrocyanic
4.
3.
2.
1.
No. of Case
acid (by Andrussow
1960-1962
1940-1942 1940 Germany 1952 (?1940 Germany)
Year
2.5
3.5
3.5
3.5
CUC
Fc
1.19
.496
.49
,496
Coefficients
30.25
17.2
13.2
13.2
TEI Value
TABLE 3 of Acrylonitrile-TEI
process) is comprised.
1.11
1.11
1.45
1.45
EMWR
Resource
Manufacture
-
-
100
Before 1950
11
72
17
-95
-5
-
Early 1980s
% of Total
Mid- 1960s
Installed Capacity
Values [22-24
Not commercial
Observations
60
B. ZAIDMAN
AND G. CEVIDALLI
OTHER EXAMPLES
The relevance of the TEI concept was confirmed by more applications to industrial technologies. The TEI analysis of the manufacture of aniline is presented in Table 2. The first industrial process, nitro-benzene reduction (case la), is obsolete, with the exception of those situations in which the by-product, iron oxide, finds a utilization (case lb). This situation is clearly expressed by the respective TEI values. The dominant process today (95% of the installed capacity) is the catalytic reduction of nitrobenzene, and it has the highest TEI value. Two relatively new technological concepts (cases 3, 4) have not found a fully commercial application. From Table 2, it appears that the high value of the complexity factor F, for these later processes lowers their TEI values. In Table 3 the different processes for the manufacture of acrylonitrile are presented. The first three processes (cases l-3), based on the addition of the hydrocyanic acid to C2 speciae, have low TEI value due to the extreme reaction conditions and have practically no present commercial application. The technological superiority of the SOHIO process (amoxidation of propylene, case 4) finds a good expression in its TEI value. About 95% of the acrylonitrile is produced today by the SOHIO process. Table 4(aac) presents the TEI values of the principal processes for the manufacture of phtalic anhydride, ethylene oxide, and maleic anhydride. The corelation between the TEI values and the diffusion of the technologies is evident in all the three cases. It appears that, at least in the above analyzed cases, there exists a clear concordance between the TEI classification of a technological concept and its industrial fate. Conclusions and Comments A quantitative method for measuring the technological efficiency of concurrent processes in the chemical processing industries has been developed. The methodology uses factors objectively measurable in terms of technical characteristics of the processes. The data necessary for the use of the methodology are available at each stage of the innovation process. The relevance of the method is demonstrated by its successful application in the evaluation of processes for the production of phenol, aniline, acrylonitrile, and others. When the possibility of using the proposed method as a tool for a preliminary evaluation of research projects is examined, the fact that this approach does not take into consideration the prices of the process constituents raises some questions as to its validity. The good agreement between the TEI values calculated and the development and difusion of the CPI innovations indicates that the TEI can be used as an evaluation tool at the preliminary conceptual stage. Does this really mean that a sound and efficient “technological concept” may be independent from the vagaries of the economic and political environment, as reflected by the changing prices of the various resurces? Is such a measure of the efficiency of a technological concept more meaningful than economic indicators established in a defined time frame? In a long-term perspective, the answer is probably yes, but in the short-time approach, the harsh day-to-day reality cannot be ignored. References 1. Technological Forecasting and Social Change, 27, (1985). 2. Delaney, Charles L., Technology Forecasting: Aircraft Hazard Determination, Technological Forecasting and Social Change, 5. 249-252 (1973). 3. Gordon, J. T., and Manson, R. T., A Proposed Convention for Measuring the State of the Art of Products or Processes, Technological Forecasting and Social Change. 20, 1-26 (1981). 4. Edwards, K. L., and Gordon, J. T., Further Research into a Convention for Measuring the State of the Art of Products or Processes, Technological Forecasting and Social Change, 24, 153-175 (1983). 5. Dodson, E. N., A General Approach to Measurement of the State- of the Art and Technological Advance, Technological Forecasting and Social Change, 1, 391408 (1970).
Concept
[31-331
1. Benzene oxidation 2. Butane dehydro-oxidation 3. Butene oxidation
4c. Maleic anhydride
1 Chlorohydrine 2. Oxidation of ethylene
4b. Ethylene oxide [28-301
1. Naphtalene oxidation 2. 0-xylene oxidation (liquid phase; catalyzated)
[25-271
Technological
4a. Phtalic anhydride
No. of Case
-1957 1975 1975
1925 -1960
1917-1920 1946
Year
Manufacture
0.79 0.59 0.57
4.08 1
0.86 0.71
EMWR
2 2 2
2.5 1.5
2.5 2.5
CUC
1.276 1.216 1.280
1.052 1.11
1.17 1.05
Fc
Resource Coefficients
49.6 69.69 68.53
9.3 60.0
39.75 53.53
TEI Value
TABLE 4 of Chemical Products-TEI
-
-
100 -
95 -
100
9.5 90.5
70 30
90 [34]
10
-2 -98
35 65
Early 1980s
% of Total
Mid- 1960s
Installed Capacity Before 1950
Values
Observations
62
B. ZAIDMAN
AND G. CEVIDALLI
6. Dodson, E. N., Measurement of Technology Usmg Trade-off Surfaces, Technological Forecasting und Social Change, 27, 1985). 7. Ayres, R. U., Empirical Measures of Technological Change at the Sectoral Level, Technological Forrcasting and Social Change, 27, 229-247 (1985). 8. Stalworthy, E. A., The Viewpoint of a Large Chemical Manufacturing Company, The Chemical Engineer, June, CE 182~CE 189 (1970). 9. Allen, D. H., Revised Techniques for Predesign Cost Estimating, Chemical Engineering, March 3. 142150 (1975). 10. Bridgewater A. V., The Functional Unit Approach to Rapid Cost Estimation, AACE Bulletin. October, 153-164 (1976). 11. Rudd, D. F., et al., Petrochemical Technology Assessment, John Wiley, New York, 1981, Chap. 2, pp. 35-72, Chap. 3, pp. 73-83. 12. James, D. E., et. al., Economic Approaches to Environmental problems, Elsevier, New York, 1978, p, 163. 13. Atkins, M., and Lowe, Y., Pollution Control Costs in Industry, Pergamon Press, U.K. 1977, p. 148. 14. Cevidalli, G., and Benedetti, L., Processi Chimici non Inquinanti, La Chimica e l’fndusrria, 53, U-53 (1971). 15. Cevidalli, G., and Zaidman, B., Evaluate Research Projects Rapidly, Chemical Engineering, July 14, 145-152 (1980). 16. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 1st Ed., Vol. 10, 1953. 17. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 15, 1968, pp. 147-159. 18. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 17, 1982, pp. 373-384. 19. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 1st Ed., Vol. 1, 1947, pp. 916-917. 20. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 2, 1969, pp. 41 l-426. 21. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 2, 1978, pp. 309-321. 22. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 1st Ed., Vol. 1, 1947, pp. 185-188. 23. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 1, 1963, pp. 338-351. 24. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 1, 1978, pp. 414-416. 25. Kirk, R., and Othmer, D., Encyclopedia ofChemical Technology, 1st Ed., Vol. 10, 1953, pp. 588-590. 26. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 15, 1953, pp. 444457. 27. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 17, 1982, pp. 732-746. 28. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 1st Ed., Vol. 5, 1950, pp. 320-325. 29. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 8, 1965, pp. 523-558. 30. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 9, 1980, pp. 43247 1. 31. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 1st Ed., Vol. 8, 1952, pp. 680-699. 32. Kirk, R., and Otbmer, D., Encyclopedia of Chemical Technology, 2nd Ed., Vol. 12, 1967, pp. 819-834. 33. Kirk, R., and Othmer, D., Encyclopedia of Chemical Technology, 3rd Ed., Vol. 14, 1981, pp. 770-790. 34. Chowdhury, J., Maleic anhydride Manufacture, Chemical Engineering August 17, 29-33 (1987). Received 8 January 1988; revised 3 June 1988.