Economia & Energia
No 20 - Maio - Junho 2000
|THE BRAZILIAN EXPERIENCE ON DEVELOPING A ALCOHOL-DIESEL
BINARY FUEL (*)
AUTHORS: ADAILSON DA SILVA SANTOS a,b
This work has the objective of evaluating the present situation of ethanol oxygenated compounds added to diesel. For this purpose we have made the historical attempts of its introduction as well policies for reducing fossil fuels consumption.
Ethanol in light automotive engines - PROALCOOL
As a consequence of the petroleum crises, the strategic need of reducing the country's dependency on imported petroleum resulted in turning ethanol the "official" fuel for light vehicles and in 1975 the National Alcohol Program - PROALCOOL - was established.
With PROALCOOL, the internal gasoline consumption was drastically reduced but the refining level was not altered since diesel oil consumption in the country was (and continues to be) extremely high ,, corresponding to 35% of the refined volume (NUNES)
At the end of the seventies it was considered the hypothesis of substituting diesel by alcohol in diesel cycle engines (DIAS). This substitution resulted in some problems concerning adaptation of the system to the new fuel (ECKLUND), such as efficient and economical additives in order to increase the self-ignition power of ethanol due to its low cetane content, engines adjustment - mainly the injection system - and the use of materials more resistant to contact with alcohol.
Research has demonstrated that it is not possible to establish this substitution program in diesel cycle engines.
The strong justification presented to the Federal Government of maintaining employed in the land a large manpower,, together with the reduction of pollution levels, used by part of the alcohol industry resulted in the proposition of adding alcohol to diesel. Studies carried out in 1984 concluded that using a mixture of 93% v/v of diesel oil and 7% v/v of anhydrous alcohol is viable from the technical point of view. It does not result in loss of efficiency or fuel consumption increase and it contributes to reducing the emission of particulate. In 1997 it was proposed a new Law project forcing the addition of 15% v/v ethyl alcohol to diesel oil (FENSTERSEIFER).
The governmental decision to add ethanol to the diesel energy matrix accelerated research and test works necessary for establishing the program. The CIMA ( Inter-ministerial Council for Alcohol and Sugar) established then a working group composed of various institutions, including research bodies and representatives of the different interested sectors, sugar cane and fuel producers, car assemblers and car parts suppliers.
Among the works sponsored by the Ministry of Science and Technology appeared the technical alternative of hydrated alcohol - diesel emulsions. This alternative was endorsed by METHANEX, a multinational group and one of the largest methanol producers in the world that commercializes an emulsifier agent named DALCO, fabricated by the Australian APACE (SOSALLA).
In São Paulo it is under test a mixture of hydrated alcohol (90.2% p/p of sulfur), DALCO additive (0.5% to 0.8% v/v) and anti-corrosion additives and cetane rating increasers . These tests, financed also by the Companhia de Transportes Coletivos de São Paulo - CTC-SP - were carried out in laboratory and in field. The assays were made with up to 20% v/v of hydrated alcohol, emulsifiers, with and without anticorrosion and cetana rating increasers. . .
The main critical points found by this group were:
Other problems were detected such as dependence on a sole emulsion supplier, difficulty in the integration with other countries, refusal from car parts manufactures to guarantee the quality of their products, taking into account the wear out due to using ethanol.
Due to serious problems concerning residue deposition in the injection pump, this alternative was abandoned (e&e).
Other possibilities that are being tested by a group sponsored by Alcohol and Sugar Producers Association of Paraná is the anhydrous alcohol - diesel solution that is possible due to the AEP national compound, derived from soy and that is biologically degraded. The proportion given in the table below has been used in some urban buses in Curitiba and also in São Paulo (FENSTERSEIFER).
Table 2 - Mixture used in urban buses in Curitiba:
SOURCE: MELCHIORS, 1994.
It has been observed a reduction in smoke emission and fuel consumption, cetane rating increase as well as the occurrence of problems concerning only rotating injection pumps which are minority in the Brazilian fleet (Mercedes Benz, the largest diesel engines manufacturer, uses rotating pumps only in light vehicles) (e&e).
As for price estimate, it has been calculated that the mixture will be 14 % more expensive to the final consumer than diesel. Tests are continuing and one of the critical problems observed is the mixture stability. (FENSTERSEIFER) .
Concerning the large quantity of stored alcohol that is not commercialized yet, the Federal Government has altered the legislation of the sector last November, allowing the addition of 26% of AEC in gasoline engines , besides the addition of 3% v/v alcohol to diesel (PETROBRÁS).
This authorization surprised the trucks, buses and pick-up engines manufacturers. Their main allegation was the corrosion on the different parts involved. This allegation is premature since the tests are still under way and the doubts are numerous, specially in what concerns the corrosion on the parts due to the hygroscopic characteristics of ethanol, cetane rating decrease, injection systems and consumption (MURTA VALLE).
Justifications concerning pollutants emission reduction in order to strengthen the mixture alcohol-diesel and compensate the fact that many technical problems have been solved coincide with PETROBRÁS' ongoing program for improving diesel quality. The company is investing US$ 1.5 billion to amplify the diesel park (COELHO).
In January 1999 the HDT (diesel hydrating) unit of RPBC (Presidente Bernardes Refinery, SP) started commercial operation. For this purpose US$ 270 million were invested and its processing capacity is 5 thousand m3/ day. In the second semester of 1999 two HDT units started operation in REPLAN (Planalto Paulista Refinery, SP) (MARTINEZ).
In the first semester of 2000, the modernization works of HDT and HDS (diesel hydro-desulfuring) units at REDUC (Duque de Caxias Refinery, RJ), REPAR (Presidente Getúlio Vargas Refinery, PR), REPAG (Gabriel Passos Refinery, MG) and REFAP (Alberto Pasqualini, RS) will be started.
Besides these ones, other projects will be ended until 2002 with investments estimated in US$ 600 million. They are (MARTINEZ):
In spite of tests made with metropolitan buses in Curitiba, Paraná, the announced changes will probably force diesel engines manufacturers to use materials that are more corrosion-resistant (PETROBRÁS).
Knowing its vantages and disadvantages, due to its multiple facets, even after two decades of PROALCOOL, the use of ethanol is far from having a defined policy, because it overloads in one way or another all sectors involved (GIANNINI).
Economia e Energia (E&E) - ONG: http://www.ecen.com
IPT: http:// www.ipt.br
(*)Part of this article was presented in a Congress in Cuba.