POWER STATION PERFORMANCE OPTIMISED BY THE USE OF FUEL TREATMENT ADDITIVES

Transcription

1 CONSEIL INTERNATIONAL INTERNATIONAL COUNCIL DES MACHINES A COMBUSTION ON COMBUSTION ENGINES POWER STATION PERFORMANCE OPTIMISED BY THE USE OF FUEL TREATMENT ADDITIVES Bert Wouters, Maintenance and Operations Manager Peruhmahan Bukit Indah Sukajadi Jl Cemara Angin nr 9, Batam, Tel.: b.wouters@batam.wasantara.net.id Jonas Östlund, Technical Manager, Bycosin AB Saegverksgatan 7, Karlstad, Sweden Tel.: jonas.ostlund@bycosin.se Arnim Marschewski, Technical Service Manager, Octel Deutschland GmbH, Thiesstr. 61, Herne, Germany Tel.: Marschewski@Octel.de ABSTRACT A report is presented, showing an economical way on how the operation of a Power Station burning heavy fuel oil was improved by the introduction of fuel treatment chemicals. The chemical background as well as the situation before and after the trial; including all data collected during the trial period, is presented in this report. The objective of the test was to establish and compare performance patterns between both units. The main reason for adding the fuel additive was to observe how the reduction of carbon deposits in the combustion chamber, on the valves, in the turbo charger and the exhaust gas system positively effects all the other operational parameters, e.g. exhaust gas temperature, turbo charger efficiency and, finally, the specific fuel consumption. INTRODUCTION Nowadays the milestones for an efficient and economical operation of a Power Plant are the engine design, the way of operation and the available fuel. Engine technologies are increasing very fast and also the education level of the people for a professional way to operate the engine. The only parameter that can not be influenced directly, is the availability of a good and economical fuel. Especially for modern four stroke engines with high output, the combustibility of the fuel is of CIMAC Central Secretariat c/o VDMA e.v. Lyoner Strasse Frankfurt/Germany Tel: Fax: CIMAC@vdma.org Internet:

2 paramount importance to achieve reliable operation of the engine. One way to improve the combustion of the fuel in the engine, without altering the specification of the fuel, is to introduce a chemical combustion catalyst. The operational and economical effects are shown in this paper. SCIENTIFIC CHEMICAL BACKGROUND The chemical combustion catalyst chosen for this test was PLUTOcen HF69. The active compound in the PLUTOcen products is an iron-containing organometallic chemical called ferrocene. It is a sandwich compound, consisting of a pair of pentadienyl rings with an iron atom squeezed inbetween. Ferrocene has the formula (C 5 H 5 ) 2 Fe, a molecular weight of , and is an orange crystalline substance that is insoluble in water but soluble in organic solvents and fuels. A number of studies have been performed to elucidate the mechanism by which ferrocene affects soot production in combustion process mainly in flames [1] Mitchell et al.[2] found that ferrocene enhances the oxidation rate of the soot. Perhaps the most revealing study into the effects on soot formation of ferrocene additivation is that of Ritrievi et al.[3], who used a ferrocene-seeded, premixed ethylene flame and performed Auger and Mossbauer analyses on the soot thus formed. They found that ferrocene addition led to soot particles that consisted of an outer layer of carbon with an iron oxide core. This observation serves to confirm the hypothesis that ferrocene acts, by initially being oxidised in the flame to form a solid iron oxide particle that serves as a nucleation centre for subsequent soot growth. At the elevated temperatures of the flame, the soot particle can be destroyed by reactions between the carbon of the soot and the iron oxide. The FEV [4] and the University of Rostock [5] carried out similar investigations of combustion in diesel engines. The description of the working mechanism is simplified, only relevant products are considered. It has to be seen as an example. The complete set of reaction steps and the kinetic parameters have to be known together with all partial pressures to predict the exact behaviour of each individual engine and combustion. Step 1: Combustion of Ferrocene and fuel oil The combustion of fuel oil leads to carbon dioxide, carbon monoxide and carbon (soot) C m H n + z O 2 fi CO, CO 2, C solid... The combustion products of Ferrocene are iron oxides and carbon dioxide Fe(C 5 H 5 ) 2 + O 2 fi Fe x O y + CO... 2 The main combustion product of Ferrocene is iron oxide Fe 2 O 3 (and slight amounts of FeO). Step 2: Soot reduction activity of Ferrocene Iron oxides and soot react to carbon monoxide or carbon dioxide and iron 2 Fe 2 O 3 + 3C fi 4 Fe + 3CO 2 FeO + C fi CO + Fe Step 3: Reactivation of the catalytic activity Iron and oxygen react to iron oxide 4 Fe + 3O 2 fi 2 Fe 2 O 3 and the catalytic cycle can start again. The mechanism described above indicates that the active compound is Fe 2 O 3 that is the base of the catalytic cycle. CIMAC Congress 2004, Kyoto Paper No

3 FIELD EXPERIENCE The Power Plant The Power Plant PLTD SEI BALOI is located in Batam, Indonesia. The plant has been in operation since 1995, operated by PNL under the supervision of Wartsila Indonesia. The system: Engines 2X Stork Wartsila 9 TM 620 Rated Output 12,4 MW at 428rpm per engine T/C VTR /SLE03 Generator ABB type HSG 1600S14 Elect. Output 15430KVA each Introduction: In order to determine the results of treating heavy fuel with Octel PLUTOcen HF 69 a trial is being conducted at PLTD Sei Baloi, Batam. Data collected mainly represents performance and production data. The fuel additive is a combustion catalyst used for optimising the combustion process, resulting in a reduction of soot and unburned hydrocarbons in the exhaust gasses. Targets by adding this fuel additive are: - Reduction of build up of carbon deposits on piston crown, combustion chamber, exhaust and inlet valves. - Reduction of build up of carbon deposits on the nozzle ring and turbine blades of the turbo charger. - Reduction of carbon deposits on the heat recovery system exhaust gas boiler. For comparison one engine is running on treated fuel while the other engine uses untreated fuel. Objective of the test is to establish and compare performance patterns between both units. At the end of the test the engine which has been operating with treated fuel will be opened to check individual parts for build up of carbon deposits. Observations: Note for comparison of the units. Engine no. 2 runs with treated fuel Engine no. 1 runs with untreated fuel The fuel additive is dosed directly into the fuel booster module at a dosing rate of 1 ltr. per 2500 ltrs. fuel. The treated fuel is preheated in the booster module and from there goes directly to the engine. Prior to start of the test all injectors were overhauled and new atomisers were fitted. Output: Engine no. 2 had a slightly higher output than engine no. 1 during the test. Average outputs of the engines for the duration of the test is: Engine no. 1: 9.1 MW (9.5 MW non de-rated load see note) Engine no. 2: 9.8 MW Note: the average output of engine 1 is significantly lower because for the last 1.5 months that we recorded the performance, the engine output was de-rated due to a broken cylinder head stud. Exhaust gas temperatures: The exhaust gas temperature is a direct indication of the combustion process. Exhaust gas temperature will be influenced by the condition of the fuel injection equipment eg. atomisers and high-pressure fuel pumps, and the type or quality of fuel used. Another parameter, which is of direct influence on the exhaust gas temperature, is the amount and temperature of scavenging and combustion air. The latter is directly related to the turbocharger performance and charge air cooler condition. High exhaust gas temperatures result in 3

4 high thermal stresses on the cylinder heads and inlet and exhaust valves. On some cases even derating the output of engines is required to stay within safe parameters. Although de-rating of an engine reduces the exhaust gas temperature and output, in practice the heat balance is not within the design parameters. Although Engine no. 2 is running on a higher average load a significant difference in exhaust gas temperature can be observed. On average the exhaust gas temperature on engine no. 2 is 392 deg C whereas the average exhaust temperature on engine no. 1 is 396 deg C. Considering the difference in output the difference will be higher on equal output of both units. In order to get the maximum yield out of the injected fuel it is very important to have a quick and complete combustion in the cylinder. Heavy hydrocarbons tend to burn at a slower rate than light hydrocarbons which can result that the injected fuel is not completely combusted at the moment the exhaust valves open. As a result, the exhaust gas temperatures will rise. Furthermore, the conditions under which the heavy hydrocarbons combust are far from ideal. This will result in incomplete combustion of these particles and a build up of carbon residue on piston crowns, exhaust valves, turbocharger nozzle rings and turbine blades and exhaust gas boiler. The build up of carbon residue on the piston has a negative effect on the overall performance of the engine. The carbon deposits rub against the cylinder wall polishing it, i.e. removing the honing grooves that are so important for lubrication. A vital condition for optimum compression is the proper sealing between piston rings and liner wall and good functioning of the cylinder liner lubrication. Deep grooves in the cylinder liner, sticking or worn piston rings and lack of a lubrication oil film on the cylinder liner prevent adequate sealing. This will cause blow by of the exhaust gases and subsequent loss of compression and combustion pressure, which results in high exhaust gas temperatures and loss of power generated by the engine. Another problem of gases leaking into the cylinder block because of blow by, is the negative effect they have on the lifetime of the lubricating oil when the gases condense and enter the lubricating oil charge. Improving the combustion efficiency through optimising the conditions to obtain maximum compression pressures is of major importance. This will assure optimal conditions for proper compression and the related combustion process, which as a result should be beneficial with regard to fuel consumption, lube oil consumption and general wear on pistons, piston rings and liners. This is not only a direct saving in operational cost but subsequently an advantage for environmental reasons due to the reduction of sludge and the improvement of combustion which leads to cleaner exhaust gasses. Turbocharger: Comparing the turbocharger speeds of engine no. 1 with engine no. 2 reveals that on equal load of about 10 MW the turbocharger speed of engine no 2 is about 200 rpm lower. The air inlet pressure in the receiver is about the same for both engines. However, an indication for the amount of energy that is absorbed by the turbo charger is the temperature drop over the turbocharger. This temperature drop is on average for engine no deg C, whereas the temperature drop over the turbocharger of engine no. 2 is 130 deg C. A higher efficiency of the turbocharger will result in more combustion air, which in turn will lead to more complete combustion and the reduction of carbon deposits. Fouling of the nozzle ring by carbon CIMAC Congress 2004, Kyoto Paper No

5 deposits will lead to high exhaust gas velocity through the turbine side. As a result, less energy is transferred to the turbine and the exhaust gas temperature is higher after the turbine. In exceptional cases of fouling the turbine starts operating in an unstable area resulting in surging. Fuel consumption: During the trial period a slight difference in fuel consumption between engine no. 1 and engine no. 2 is observed. As a remark I should like to add that we measured the uncorrected specific fuel consumption in ltr/kw. An engine, which operates with a higher output, will generally have a better specific fuel consumption. Due to normal wear of the fuel injection equipment and engine components after overhauls there will always be a rise in the specific fuel consumption. Apart from the general condition of the engine the quality of the fuel and circumstances under which the engine is operated are of influence on the specific fuel consumption. Because both engines operate under the same circumstances and run on the same fuel we can eliminate these influences for comparison only. When comparing the trend of specific fuel consumption it can be noticed that the trend line for engine no. 2 increases less steeply compared to engine no. 1. the engine and inspecting the individual engine parts before cleaning it was noticed that the build up of carbon on the cylinder heads and exhaust gas housing assemblies was less than we found during previous overhauls. The build up of deposits on top of the piston crown were also less than during previous overhauls. The build up of dirt on the side of the piston and in the piston ring area was about the same as during previous overhauls. Compared to previous overhauls we found that the composition of the deposits found on the cylinder heads and exhaust valve housings were soft and could easily be removed. The build up of deposits on the top of the piston crown was of a harder composition but it was also easy to remove it. There was no indication of sticking piston rings, which was also not experienced during previous overhauls. Due to the softer composition of the carbon deposits, the time and effort needed for cleaning the engine parts was considerably reduced. The build up of deposits on the turbo charger nozzle ring and turbine blades was quite heavy. The composition of the deposits was very hard and removal was difficult, but it has to be mentioned that the turbo charger had been in operation for more than 10,000 hrs without fuel additive counting from the last turbo charger overhaul. Findings after opening engine no. 2 for overhaul: Engine no. 2 has run for a total amount of 2341 hrs with fuel additive. Before beginning the test the engine had 3962 running hours from the previous overhaul. During the previous overhaul all cylinder heads and pistons were removed and cleaned. As previously described, before starting the test with fuel additive, only the injectors were overhauled and new atomisers were mounted. After opening CONCLUSIONS Use of PLUTOcen HF 69 for the duration of 14 weeks has resulted in a drop of exhaust gas temperatures, which resulted in an increase of available power for engine no. 2. After about 10 weeks we noticed that there was an increase in fuel temperature which can be the result of wear on the nozzles and/or change in composition of the fuel. 5

6 There is no detailed fuel analysis available but measurements for specific gravity showed an increase from kg/dm3 to kg/dm3 at 15 deg C. Trends regarding the uncorrected specific fuel consumption showed a lower increase of the specific fuel consumption for engine no. 2 compared to engine no. 1. The temperature converted energy in the turbocharger is higher for engine no. 2 than engine no. 1. Due to a mechanical failure (broken cylinder head stud) the output of engine no. 1 was de-rated and for 8 weeks a good comparison between both engines was difficult to make. Regarding the build up of carbon deposits we noticed a reduction on the cylinder heads and exhaust valve housings and the removal of the carbon deposits was easy that decreased the down time during maintenance. The fact that the carbon deposits are softer will also contribute positively to the prevention of cylinder liner polishing, sticking piston rings and general wear of valves and valves seats. The calculations are only related to the savings in fuel. In practice the savings will most probably be higher if the reduction in maintenance is taken into consideration. Based on measurements and findings during overhaul and test period, we feel that the use of additive during the test period had a positive impact on the operation of this engine. NOMENCLATURE REFERENCES [1] Bonczyk, P., United Technologies Report, No. R A, 1987 [2] Mitchell, J.B.A., Miller, D.J.M.; and Sharpe, M., Combust. Sci. Technol. 74 (1-6): 63, 1991 [3] Ritrievi, K.E., Longwell, J.P., and Sarofim, A.F., Combust. Flame 70:17, 1987 [4] Projektstudie FEV: Einfluß von Ferrocen auf die Verbrennung / Rußbildung im Dieselmotor, 1993 [5] Investigation of the influence of the additive ferrocene on the combustion of heavy fuels in diesel engines, 1995 BERT WOUTERS CONTACT INFORMATION Maintenance and Operations Manager Peruhmahan Bukit Indah Sukajadi Jl Cemara Angin nr Batam, Tel.: b.wouters@batam.wasantara.net.id JONAS ÖSTLUND Technical Manager Bycosin AB Saegverksgatan Karlstad, Sweden Tel.: jonas.ostlund@bycosin.se MW rpm kva ltr deg C hrs kw Mega Watt revolutions per minute Kilo Volt Ampere Litre degree Celsius hours Kilo Watt ARNIM MARSCHEWSKI Technical Service Manager Octel Deutschland GmbH Thiesstr. 61 D Herne Germany Tel.: marschewski@octel.de CIMAC Congress 2004, Kyoto Paper No

7 Attachment 1: Comparison of specific fuel consumption 7

8 Attachment 2: Comparison of fuel costs CIMAC Congress 2004, Kyoto Paper No

9 Attachment 3: Diagrams 9

10 Attachment 4: Diagrams CIMAC Congress 2004, Kyoto Paper No

11 Attachment 5: Batam Power Plant, Indonesia Engine Storck Wärtsilä 9TM

12 Attachment 6: Cylinder heads and Cylinder Liners Engine 1 Engine 2 CIMAC Congress 2004, Kyoto Paper No