Walter R. May, SFA International, Inc., Houston, Texas, U.S.A. and Edward A. Hirs, III, FuelSpec Chemicals LLC., Houston, Texas, U.S.A.
Presented to the 11th Diesel Engine Emissions Reduction Conference, August 21-25, 2005, Chicago, IL
In 1996 an oil-soluble organo-metallic iron combustion catalyst was developed for use in Siemens-Westinghouse 501 D-5 104 MW combustion turbine engines. The product also included oil-soluble magnesium to reduce vanadium deposits and corrosion. This product resulted in significant reduction of smoke in the exhaust of engines operating in steady state and non-equilibrium start-up conditions. The overall effects were greater than predicted from the literature.
We extended this work to steam boilers and compression-ignited reciprocating engines. We have found that the iron-magnesium catalyst when added to Diesel and heavy fuel oil supplies, promotes complete and more efficient combustion in the engine, resulting in increased power, improved fuel economy and radically reduced smoke emission. Certain metals, including Mn, Fe, Cu, Ba, Ce and Pt, are known to have catalytic activity in combustion processes. The iron-magnesium combination acts synergistically to give greater activity than expected.
This paper presents data from tests conducted by a combustion turbine engine manufacturer and customer, a government testing laboratory and independent fleet tests. A mechanism for the catalysis is proposed.
Earlier papers presented on this subject are available from the SFA International web site at www.SFAInternational.com.1,2
In 1996, Siemens Westinghouse began start-up of a new power plant at Hanwha Energy in Inchon, Korea. There were initially three model 501 D5 104 MW combustion turbines with nine more in process of installation. The economics of the plant were based on use of low sulfur waxy residual (LSWR) fuel oil from the Hanwha refinery adjacent to the power plant. Particulate matter in the exhaust was 120 – 150 mg./cu. M. exceeding the 60 mg./cu. M. requirement at the time. This requirement was reduced to 40 mg./cu. M. in 1998. Westinghouse began an investigation into the use of fuel additives containing combustion catalysts to solve the problem.
This work was reported by Rising in 1997. SFA International, Inc. was invited to participate in this work. Several metals are known to catalyze combustion of hydrocarbon fuels. These metals include manganese, iron, copper, barium, cerium, calcium and platinum. Reports in the literature indicate that 50% reduction in carbonaceous matter in the exhaust is the limit of effectiveness of these catalysts.
There are positives and negatives to using these various metals. Manganese, while an effective catalyst, interferes with inhibition of vanadium by magnesium. Iron is thought to catalyze formation of sulfur trioxide leading to sulfuric acid formation limiting use to low sulfur fuels. Copper, barium and calcium are less effective and water-soluble salts of barium are highly toxic. Cerium and platinum are very expensive. It was decided that iron was the best choice for the catalyst. An oil-soluble iron carboxylate was developed that was miscible in the fuel and could be combined with oil-soluble over-based magnesium used to inhibit vanadium in the fuel.
This was a 6.0% oil-soluble iron-napthenate product. Particulate matter was reduced from 120-150 mg./cu. M. to <60 which met the initial Korean Ministry of Environment requirement in 1996-98. Westinghouse and Hanwha measured the data summarized in Table 1. The second set of turbines came on line later in 1996 and testing continued with the catalyst in six units. Table 2 presents data taken between October 31 and Dec. 26, 1996 under varying loads and percents distillate oil in the LSWR fuel.
These data demonstrated that <60 mg./M.3 could be achieved with 0% distillate oil and less than full load – see unit 3 data. The data remained above 40 mg./M.3 in most cases. This work demonstrated that (1) lower particulates are found at high load, (2) distillate fuel yielded significantly lower particulates than LSWR residual fuel, and blending small amounts of distillate into the LSWR significantly reduced particulates and (3) the reduction of particulates was proportional to the concentration of catalyst.
The remaining turbines came on line in 1997 raising the total to 12 units. Heat recovery steam generators (HRSG) units were installed and the plant capacity increased to 1,800 MW. Dust loadings as low as 20 mg./M.3 at 40 ppm Fe were measured indicating more than 80% reduction in particulate loading. The Korean Ministry of Environment reduced the particulate level requirement to 40 mg./cu. M. in 1998. We were able to meet this requirement until mid-1998 when the Korean Ministry of Environment proscribed use of the fuel in the Province of Seoul. This plant now operates on liquefied natural gas.
Hyundai Heavy Industries Petroleum Subsidiary built a new refinery at Daeson. This refinery included an on-site power plant for the refinery and local area with four Westinghouse 501 D-5 104 MW combustion turbines similar to those at Hanwha’s Inchon Plant. The fuel was a similar LSWR material although derived from Chinese crude oil rather than Indonesian in the case of Hanwha.
Both SFA International, Inc. and a competitor competed for this business. The competitor introduced a dispersion type product with 15% iron and 2% Mg that was extensively tested. The results were unusual as indicated in Figure 1. The product shows a minimum at 45 ppm Fe with strong peaks on both sides. These data are not consistent with classical laws of catalysis. SFA developed a colloidal dispersion product with high iron concentration.
We found a dosage curve similar to that at Hanwha Energy shown in Figure 1 that follows classical laws of catalysis. SFA’s FuelSpec® 118-1502 has shown lower particulate matter over the dosage range than competitor’s product. SFA’s FuelSpec® 118-1502 has an unusually small average particle size of 0.007 µm compared with average particle size of 0.05 µm for the competitor’s product shown in Figure 2. We believe that the smaller particle size results in higher activity. We do not have an explanation for the fact that the competitor’s product activity is not proportional to concentration other than the particle size. A summary of data for 2004 is presented in Table 3. We have successfully reduced emissions by 90 % at 50 ppm iron dosage rate for a two period from mid 2003.
The Korean Ministry of Environment required that the additive was tested in a government operated laboratory at the Korean Institute for Energy Research (KIER) to verify that it would function as required and not create any additional environmental problems. This work was carried out in a low-pressure test boiler at 50% and 75% loads. LSWR fuel from the Hyundai Daeson Refinery was used in the test. The data are presented in Table 4. These data are averages of up to 10 tests under each condition.
The data demonstrate that SFA’s FuelSpec® 118-1502 combustion catalyst reduces emissions by 84.3 and 89.1% respectively at 50% and 75% loads. This compares with tests presented in Table 5 for the competitor’s product one year earlier. We have no explanation as to why FuelSpec® 118-1502 performed better than the competitor’s product at 50% load and compared similarly at 75% load. The tests were carried out eleven months apart on different fuel samples. The reductions were similar to those observed in combustion turbine exhausts at Hanwha and Hyundai. There are no data in the literature that give similar reductions of particulate matter in boiler emissions.
Reciprocating engines, whether spark-ignited or compression-ignited, represent a different set of problems from combustion turbines, steam boilers and industrial process heaters. Reciprocating engines have a more complex system of pistons and valves subject to abrasive wear and problems with deposit build-up and corrosion. SFA International has treated Wärtsilla V 32 18-cylinder 8 MW engines at the Coastal Power Plant at Nejapa, El Salvador.
That experience indicated that over-based oil-soluble magnesium fuel additives could be used to inhibit vanadium deposits and prevent corrosion on piston crowns and valve seats. It also reduced corrosion and failure of turbocharger power rotors. There were no examples to our knowledge of iron- magnesium fuel additives used in automotive high-speed (4,000 rpm) compression- ignited engines used in transportation applications. In 2002, a KIA 1.6 liter Diesel truck used at the Emission Control Products WLL blend plant and warehouse in Bahrain had a severe emission problem.
It would not pass inspection for annual renewal of registration. It was suggested that the oil-soluble iron combustion catalyst combined with oil-soluble over-based magnesium might alleviate the emission problem so that the vehicle would pass inspection. The product was introduced into fuel at the rate of 30 ppm iron. A reduction of emissions was noted visually. The dosage level was increased 50 ppm. Emissions were visually eliminated and the vehicle passed inspection. More surprisingly, the driver of the vehicle reported that it had the power of a new truck. Following this observation, an owner of a bus fleet in Bahrain agreed to test in six vehicles over a period of about 8 weeks.
We reformulated the fuel additive so that 500 ml. of additive achieved 50 ppm iron and 10 ppm magnesium in 100 liters fuel. This additive was a combination of iron salts of 200-240 molecular weight highly oil soluble carboxylic acid and over-based magnesium oxide suspended in a carboxylic acid and sulfonic acid surfactant system. The product concentration was adjusted with Solvent 150, a highly aromatic solvent with a flash point >60o C. The fuel additive closely duplicated density and viscosity of the fuel so that mixing and distribution of the metals in the fuel in a homogeneous manner could be easily attained by agitation caused during normal driving conditions. There was no attempt to control driving conditions or duplicate traffic conditions. The results of this test are given in Table 6.
The six vehicles gave a range of 2.9% to +19.7 % reduction in fuel consumption. The vehicle with the lowest result was badly in need of major engine maintenance and was using oil heavily. The other vehicles had 200,000 km or more on the odometer. All drivers with positive results reported a noted increase in power from the engine. Further tests were carried out on a single vehicle under the auspices of the Automotive Research Association of India (ARAI). The vehicle was a small Padmini Premier 137D sedan.
The fuel line was attached to a calibrated measuring device so that the fuel use could be accurately measured. In a relatively short test, a total of some 1,500 km., fuel consumption was decreased 16.1% and 18.7% under city and highway conditions respectively. These data are presented in Table 7. The driver also noted an increase in power from the engine. ARAI measured fuel consumption alternatively from carbon dioxide measurements in the exhaust. They discovered that with catalyst, the same amount of carbon dioxide was in the exhaust (at similar rpm and loads) with and without catalyst although 10% less fuel was passing through the engine. This test demonstrated that the catalyst promoted much more efficient combustion of the fuel.
Hydrocarbon fuels contain a mixture of molecules with varying hydrogen to carbon ratio. Three examples of combustion reactions are:
Methane CH4 + O2 = CO2 + H2O
Aliphatic -CH2- + 3/2 O2 = CO2 + H2O
Asphaltenic -CH- + 5/4 O2 = CO2 + ½ H2O
The exact chemical reaction in the combustion process depends on the molecular structure and distribution of the fuel.
In the combustion-ignited reciprocating engine, oxygen present in air is compressed to ignition temperature and fuel is injected. While the air is in slight excess, it can be safely assumed that a discreet 2nd order reaction is occurring with two distinct reactants, hydrocarbon fuel and oxygen.
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