M.A. Morales*, V.M. Herrero*, S.A. Martı´nez**, M.G. Rodrı´guez**, E. Valdivieso***, G. Garcia* and Ma. de los A´ngeles Elı´as**** *Pemex-Petroquı´mica, Jacarandas 100, Col. Rancho Alegre 1, Coatzacoalcos, Veracruz, Me´xico. (E-mail:
[email protected]) **Universidad Auto´noma Metropolitana, Av. San Pablo 180 C.P. 02200, Me´xico ***Comisio´n Nacional para el Ahorro de la Energı´a. Rı´o Lerma No. 302 Col. Cuauhte´moc, C.P. 06500, Me´xico ****Cognis Mexicana S. A. de C. V., Calzada de la Viga s/n, Frac. Los Laureles, 55090, Ecatepec de Morelos, Edo. de Me´xico, Me´xico Abstract In the frame of the Petro´leos Mexicanos Institutional Program for Sustainable Development, processes were evaluated in the manufacture operation of the petrochemical industry, with the purpose of reducing their ecological fingerprint. Thirteen cleaner production opportunities were registered in six process plants: ethylene oxide and glycols, acetaldehyde, ethylene, high density polyethylene, polypropylene switch and acrylonitrile, and 45 recommendations in the waste water treatment plant. Morelos is the second most important petrochemical complex in the Mexican and Latin American petrochemical industry. A tool was developed to obtain eco-efficiency indicators in operation processes, and as a result, potential savings were obtained based on best performance, as well as the integrated distribution of Sankey diagrams. Likewise, a mechanism of calculation to obtain economic savings based on the reduction of residues during the whole productive process is proposed. These improvement opportunities and recommendations will result in economic and environmental benefits minimising the use of water, efficient use of energy, raw materials and reducing residues from source, generating less environmental impacts during the process. Keywords Cleaner production; eco-efficiency; ecological fingerprint
Water Science & Technology Vol 53 No 11 pp 11–16 Q IWA Publishing 2006
Cleaner production and methodological proposal of eco-efficiency measurement in a Mexican petrochemical complex
Introduction
Petroquı´mica Morelos, an affiliate of Pemex-Petroquı´mica, is one of the largest and most important petrochemical complexes in Mexico and Latin America. Six different petrochemical plants produce ethylene (600,000 ton/yr), ethylene oxide (250,000 ton/yr), highdensity polyethylene (100,000 ton/yr), polypropylene switch (100,000 ton/yr), acrylonitrile (50,000 ton/yr) and acetaldehyde (100,000 ton/yr) and other products from ethylene and propylene. Petrochemical production is approximately 1.6 thousand million ton/yr. Energy consumption of the Petroquı´mica Morelos is 6.7 thousand million cal/yr and water consumption is 20.7 thousand million m3/yr, whereas 1,630 ton/yr of hazardous residues, and 350 ton/yr as the mass of pollutants measured as BOD in its effluent source, are generated. The wastewater flow rate produced is about 6,500 m3/day, and contains poisonous substances classified as toxics such as 1,2-dichloroethane, chloroform, benzene, among other volatile compounds. The wastewater produced from the different chemical processes must be treated before discharge to the river, to reach the effluent quality required by the Mexican environment legislation. This paper documents the results of seven evaluations in a cleaner production (CP) portfolio and one methodological proposal of eco-efficiency measurement with the aim of reducing the environmental doi: 10.2166/wst.2006.332
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impacts, the operation costs and to ensure the increase of economical value of the business, through the integration of “Institutional Program for Sustainable Development”, to reduce their ecological fingerprint (Wackernagel and Ress, 1996). Materials and methods M.A. Morales et al.
In this present paper the eco-balance tool was applied in the production processes of ethylene oxide and glycols, ethylene, acetaldehyde, high-density polyethylene, polypropylene switch, acrylonitrile and the wastewater treatment plant, following the stages from the guide Audit and Reduction of Emissions and Industrial Residues Handbook of CP (UNEP/UNIDO, 1999), to evaluate the profit of each process as goals in relation to raw material/product, energy consumption/product, water consumption/product, their environmental impacts and to identify the improvement areas and CP opportunities. In order to set and measure the eco-efficiency indicators, the criteria of Saling et al. (2002) and Verfaille and Bidwell (2000) were considered. Process inputs: water and energy consumption, raw material and the environmental impacts generated; emissions to the atmosphere, solid wastes, liquid effluent of process, by means of Raw material; product or waste value RM; P; W ¼ Production P
ð1Þ
To support the data analysis, the eco-efficiency indicators were obtained through correlation and a dispersion analysis of the best behaviour of outputs and inputs from each process in the production function, or the best line of tendency for each indicator, namely of energy, water, profit and residuals, giving as a result the potential economic savings for each indicator analysed, applied to a process during its operation from the ethylene plant of the Morelos petrochemical complex. Finally, three factors of weight and importance were established, to take into account for the CP opportunity areas registered on file of the evaluated plants: economic priority (EP), environmental priority (EnP) and technical priority (TP), with the following importance values: high (3), medium (2) and low (1). Results and discussion Cleaner production portfolio
There were 13 CP opportunities identified and 45 recommendations in seven installations evaluated. This paper describes the most important opportunities obtained (Tables 1, 2 and 3) which are more representative from the environmental and economic point of view. Measurement of eco-efficiency indicators: Case Ethylene Plant
Based on the correlation and dispersion analysis, as can be seen in Figures 1 and 2, the tendencies of eco-efficiency indicators per year and the calculation of potential Table 1 Ethylene oxide and glycols plant Environmental benefits
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Product recovering (monoethyleneglycol) 730 ton/yr, reduction of pollutants treated and reduction of CO2 emissions from biological oxidation To stop treating 600 ton of pollutants charge measured as COD in the wastewater treatment plant, this is equivalent to 96,600 kWh/day from electrical energy, and to stop generating 270 ton CO2 from biological oxidation Reduction from 245.6 ton CO2/day to stop burn gas saved Elimination of 340 ton CO2/day for commercialisation to the companies Praxair and Cryoinfra
Economic benefits (US$/yr)
243,478 60,869
313,043 2,608,695
Table 2 Ethylene plant Environmental benefits
Economic benefits (US$/yr)
52,173
M.A. Morales et al.
Reuse of 9,000 diesel L/d for shipment to boilers as an alternative fuel Environmental benefits in ethylene and wastewater treatment plant were: 95% Residues reduction 5% Electrical energy saving 1% Wastewater saving 90% Emissions reduction of BTX in the labour environment 100% Reduction of toxicity (benzene) from primary treatment mud 15% Reduction of CO2 emissions
Table 3 Polypropylene switch plant Environmental benefits
Economic benefits (US$/yr)
Reduction of 62.3 ton CO2/month to reduce the consumption of natural gas 40,000 to the second year
numerical savings (Table 4 with eight indicators) correlated to the areas on each year curve and the tendency of the indicator that was elected, which can be approached through good operative practices, were obtained. The benchmarks represent the “ideal” behaviour of the process indicator analysed in production line function. Above are the exceeded values of raw materials, products or residuals equivalents in savings. As seen in Table 4, the tool provides valuable help in identifying the potential savings of the process under analysis, starting from obtaining the eco-efficiency indicators, without carrying out the application of tools for the cleaner production evaluation. At the same time, the integrated distribution Sankey diagram (Figure 3) with the particular indicator for the process was obtained. Finally, with the aim of estimating the economic savings that can be obtained to improve the profit to reduce the emission of residuals between the productions, equation 2 was developed: Y eco ¼ f ðYg 2 YrÞ £ ðPriceÞ £ ðGwasÞ
ð2Þ
Years 1999
26
Yield (MBtu/t)
2000 2001
21
2002
16
2003 Bench
11 6 1 2000
12000
22000
32000
42000
52000
62000
Ethylene production (t) Figure 1 The behaviour and lines of tendency of the energy indicator per years (natural gas)
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1.46
M.A. Morales et al.
Yields (CO2/t)
1.26
Years 2001
1.06
2002 2003
0.86
Bench
0.66 0.46 0.26 0.06 2000
12000
22000
32000
42000
52000
62000
Ethylene production (t) Figure 2 The behaviour and lines of tendency of the greenhouse gas emission (CO2)
where Yeco is yield in economical saving (US$); Yg is yield goal (year X); Yr is yield real (month X); Price is price by commercialising the residuals or cost for management; and Gwas is generation of waste in tons (month X). Figure 4 shows the action of applying equation 2 to the petrochemical industry. Considering a price of 4.56 US$/tonCO2, for the sale of CO2 in the internal market of bonds of carbon, as a consequence of reduction residual for execution of diverse actions of CP, the economic benefits can be quantified. Summing January and March to July of 2004, the result was US$ 334,754. In February, the yield was 1.30 owing to a plant off operation, which means a payment of 180,647 US$, instead of a sale. If the seven months were evaluated, the total utility would be $154,107. The actions of CP can compensate the losses due to the out operation of the plants. In this way, the equation allows the environmental performance and the costs or benefits that are registered in the organisation to be monitored; when reduction strategies in pollution were implemented and the use of resources in the origin, to reduce their ecological fingerprint. On the contrary, not to do this will mean costs for treatment or disposition of waste.
Table 4 Potential savings in raw material, energy, water and residuals in accordance with the best tendency of the eco-efficiency indicator per years Description
Year 2000
Yield raw material: Ethene: Ethylene (ton) Natural gas (MBtu) High steam (ton) Cooling water (m3) Residual of NaOH used Residual of turn off water Emission of CO2 (ton) Emission of volatile organic compounds (ton) 14
2001
2002*
2003
123,555
123,189
313,985
137,805
494,009 1,341,213 80,369,224 1,903 82,111 14,476 0.66
345,638 1,267,421 90,639,399 1,903 82,111 14,476 0.66
216,475 922,525 71,435,485 1,555 146,167 10,037 0.46
674,626 1,052,786 88,302,169 1,946 75,800 33,314 1.53
*The plant operated to low charge and stopped because of enlargement
Energy of combustion gas MMBtu
VOCs (t) 0.35
CO 2 (t)
Ethylene plant
49,398 Ethane (t) 4.7
0 7,722
Ethylene (t)
38,051
Natural gas (MMpc)
1,026
Calorific power Btu/pc
EI
307.116
MMBtu/t
886,209
Electric energy (kWh)
WaI
338.466
m3/t
160,246
Haight steam (t)
ICO2
0.2029
tCO2/t
Iwas
0.8651
m3/t
CPI
0.8227
m3/t
Cold system (MMBtu) Steam (MMBtu)
12,872,090 6,888 0
Cooling water (m3 ) Treatment water (m3 ) 3
Yield
Demineralized water (m )
1.298
Radiation and convection (MMBtu) 0
0
Wastewater (m3 )
32,467 3
Date: December 2003
0
Waste caustic (m )
450
Flight (MMBtu) 0 Condensed 0 Steam
Figure 3 Integrated distribution Sankey diagram
M.A. Morales et al.
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Yield real
Yield goal (2004)
Yeco (USD $)
1.6
150,000 100,408
100,000
90,022
1.2
59,705
M.A. Morales et al.
1.0
Yield
59,568
7,424
50,000 –
17,627
0.8 –50,000
0.6
Yeco (USD $)
1.4
–100,000
0.4
–150,000
0.2
–180,647
0.0 Dec-04
Nov-04
Oct-04
Sep-04
Aug-04
Jul-04
Jun-04
May-04
Apr-04
Mar-04
Feb-04
Jan-04
2003
–200,000
Months Figure 4 Action of the environmental performance and economic benefits applying equation 2
Conclusions
Through the use of the correlation and dispersion analysis of the best behaviour from the eco-efficiency indicators, based on the quotients raw material, product and residuals between the production, can be obtained the potential savings in each case analysed, also presented later through the evaluation of CP. Both actions will allow focusing efforts on the improvement opportunities identified in the production process, which will bring economic and environmental benefits. The considered mechanism and equation 1 present a frame which can be used for measuring progress towards economic and environmental sustainability from the organisation. In this way, the technological development from processes of CP can result in high efficiency, operative optimisation and residues or environmental impacts diminishing. Acknowledgements
We are grateful to Petroquı´mica Morelos S.A. de C.V., Comisio´n Nacional para el Ahorro de la Energı´a (CONAE) and the Mexican Cleaner Production Centre from the IPN for supporting these projects.
References Saling, P., Kicherer, A., Dittrich-Kra¨mer, B., Wittlinger, R., Zombik, W., Schmidt, I., Schrott, W. and Schmidt, S. (2002). Eco-efficiency Analysis by BASF: The Method. Int. JLCA (Onlinefirst). UNEP-UNIDO (1999). Audit and reduction of emissions and industrial residues handbook. Technical Report No. 7. Verfaille, H.A. and Bidwell, R. (2000). Measuring Eco-Efficiency. A Guide to Reporting Company Performance. Ed. World Business Council for Sustainable Development. Wackernagel, M. and Ress, W. (1996). Our Ecological Footprint. Reduce Human Impact on the Earth. New Society Publishers, Gabriole Island, BC, Canada.
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