RB-4 ANALYSIS OF THE DECREASE OF SLUDGE DEPOSITED IN THE FUEL OIL FILTRATION SYSTEM
IN A POWER PLANT
1 - INTRODUCTION
In order to quantify the effect that the additive for fuel oil “rb bertomeu” has on the formation of sludge in the fuel filter of a cogeneration plant, we reviewed the data contained in our archives, and eventually chose data from the cogeneration plant at the company Minera de Santa Marta located in Belorado, Burgos province, Spain. Only this plant provides sufficient data to form comparisons between the use and non-use of additive treatment.
The effects of our additives in this respect are produced by the dispersal of carbon solids contained in the fuel oil, in such a way that they are homogenised within the fuel, while preventing further sedimentation (a common occurrence due to ageing of the fuel). In practice, both effects have the following results:
a) Reduced sedimentation of sludge occurs in the fuel oil storage tanks.
b) Reduced quantities of sludge are deposited in the fuel oil filtration system. This sludge is composed mainly of insoluble carbon and asphalt residues, but can be utilised in combustion and improve the energy yield of the fuel.
c) Because comparatively lesser quantities of sludge are produced, the costs of treating and removing them are reduced.
This analysis aims to quantify the result in (c) on the basis of data recorded in the plant detailed above, which is equipped with three Deutz engines and has run on fuel oil No. 1 BIA since it was brought into service in March/April 1995.
2 - AVERAGE COMPOSITION OF THE FUEL OIL USED
Although this is not absolutely essential for this study, as the data are comparative, it may be of interest to provide the average composition of the fuel oil No.1 BIA used, including the components that are mainly responsible for the formation of sludge.
Conradson Carbon 9.40 %
Asphaltenes 4.20 %
Heavy Metals 120 ppm
Water and sediment 0.30 %
Ash 0.046 %
3 – SLDUGE DEPOSITED IN THE DEPURATION SYSTEM
The quantities of sludge produced are quoted in dry Kg (excluding the water contained in the sludge) per Ton (T) of fuel oil consumed.
Period monitored Additive utilised Kg. sludge / T fuel Order
May – July 1995 None 8.87 1
August – October ’95 “rb bertomeu” beco FB 4.97 2
Nov. ’95 – Jan. ’96 None 8.04 3
Feb. - Dec. ’96 “rb bertomeu” beco F1/ASF 3.31 4
* Reduction attained in the first test period (2 - 1):
8.87 – 4.97 = 4.97 Kg of sludge per T of fuel
Reduction = 44 %
* Reduction attained in the second test period (4 - 3):
8.04 – 3.31 = 4.73 Kg of sludge per T of fuel
Reduction = 59 %
* Average overall reduction:
(8.87+8.04) - (4.97+3.31) = 4.32 Kg of sludge per T of fuel
Reduction = 51 %
4 - EVALUATION OF THE RESULT
4-1 The improved utilisation of the combustible solids contained in the fuel oil, assuming that these solids have the same N.C.V. as the fuel as a whole, would produce a an energy saving equivalent to:
Average reduction in combustible sludge = 4.32 Kg per T of fuel
Energy saving = 0.432 %
Average fuel consumption = 216.5g fuel per KWhe produced
Fuel saving = 216.5 x 0.432 % = 0.94 Kg fuel per Kwhe produced
Savings per MWhe produced = 0.94 Kg fuel oil /MWhe x 0.195 €/Kgr fuel oil = 0.1833 €/MWhe
4-2 The reduction in sludge deposits means that the total costs of removing them for off-site treatment in an authorised plant are reduced proportionately. Currently, the cost of the sludge removal is calculated at an average 110 €/T. Thus, by taking into account the reduction attained along with this cost, the saving is:
Average reduction in combustible sludge = 4.32 Kg / T of fuel
Saving per T of fuel oil = 4.32 Kg sludge/Tm fuel x '.11' €/kg sludge removal = 0.4752 €/T
Savings per MWhe produced = (216.5 x 0.4752) / 1,000 = 0.1029 €/MWhe
5 - SAVINGS
After adding the results from the sections 4.1 and 4.2, we will obtain the total savings due to sludge reduction.
Savings due to sludge leverage = 0.1833 €/MWhe
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