Emission Rate Estimation of Fuel Oil in A Combustion System Using Empirical Method

DOI: http://dx.doi.org/10.24018/ejers.2019.4.12.1574 6  Abstract—This work highlighted the prediction of the emission rates of the products of combustion using a fuel oil of specific gravity of 0.9. The two reaction pathways of complete combustion and incomplete combustion were used differently to ascertain the emission rates. Ultimate analysis was conducted on the fuel oil to show the percentage composition of elements using ASTM 3178 method for carbon and hydrogen, Kjedahl method for nitrogen, ASTM D1552 for sulphur and the differences used to compute that of oxygen. The estimated percentages of the various elements were the stoichiometrically used to compute the emissions rates at standard conditions. The basis of the computation was a fuel oil flow rate of 10Tonnes/h and the following emission rates were predicted for the complete combustion reaction pathway: 31,246Kg/h for CO2, 65Kg/h for H2O, 158Kg/h for NO2 and 20Kg/h for SO2 while 9,940Kg/h for CO2, 15,623Kg/h for CO, 11,700Kg/h for H2O, 11Kg/h for H2S and 158Kg/h for NO2 were predicted for the incomplete combustion pathway. The study noted that this predictive path should be taken where effective devices or logistics are not in place to measure emissions from combustion systems.



Abstract-This work highlighted the prediction of the emission rates of the products of combustion using a fuel oil of specific gravity of 0.9.The two reaction pathways of complete combustion and incomplete combustion were used differently to ascertain the emission rates.Ultimate analysis was conducted on the fuel oil to show the percentage composition of elements using ASTM 3178 method for carbon and hydrogen, Kjedahl method for nitrogen, ASTM D1552 for sulphur and the differences used to compute that of oxygen.The estimated percentages of the various elements were the stoichiometrically used to compute the emissions rates at standard conditions.The basis of the computation was a fuel oil flow rate of 10Tonnes/h and the following emission rates were predicted for the complete combustion reaction pathway: 31,246Kg/h for CO2, 65Kg/h for H2O, 158Kg/h for NO2 and 20Kg/h for SO2 while 9,940Kg/h for CO2, 15,623Kg/h for CO, 11,700Kg/h for H2O, 11Kg/h for H2S and 158Kg/h for NO2 were predicted for the incomplete combustion pathway.The study noted that this predictive path should be taken where effective devices or logistics are not in place to measure emissions from combustion systems.

I. INTRODUCTION
Combustion is related to the burning of a fuel.The fuel could be solid, liquid or gas.There are two types of combustion, complete combustion and incomplete combustion.Reference [1] reckons that complete combustion requires a fuel burning in the presence of oxygen producing limited products.Reference [1] also further reiterated that when a fuel of hydrocarbon categorisation burns in the presence of oxygen, the products is predominantly CO2 and H2O.If there is carbon, nitrogen and sulphur entrainments in the fuel, it is oxidised to CO2, NO2 and SO2 respectively.Since nitrogen is abundant in air, it is oxidised to NO2 at very high temperatures while SO2 is produced only if sulphur is present in the fuel [1].One of the properties of complete combustion is the complete burning of the fuel.Reference [2] reiterated that while explaining complete combustion as an interaction between fuel and oxygen resulting in total consumption which requires specific duration of time and turbulence as well as high temperature needed to burn all the fuel elements.
Reference [1] also explained what makes up incomplete combustion as combustion requiring insufficient oxygen needed to oxidise the fuel to CO2 but instead leading to the formation of CO.Reference [3] also reiterated that CO is a product in the incomplete combustion fuel particularly carbon.
Various studies have established that combustion products such as oxides of C, N and S are emitted to the atmosphere which causes different forms of debilitating effects on the environment.In order to control such emissions, a careful evaluation, measurements and monitoring of these emissions is good practice.Handheld gas detectors are used to measure the emissions from these combustion chambers, however, most operations give limited space to measure, therefore it is expedient to predict the amount of emissions using laboratory findings of the fuel for the combustion.Ultimate analysis is a major tool in finding empirical evidences to the amount of combustion products released to the atmosphere.
Reference [4] described ultimate analysis as the categorisation of a combustion fuel into various elemental constituents by subjecting a small sample through a combustion analysis of the remnants.Reference [5] further highlighted the elemental categories that ultimate analysis generates as carbon, nitrogen, hydrogen, oxygen and sulphur.
In order to predict the emission rates, these elemental categorisations in percentages are used to estimate the empirical formation and then stoichiometric evaluations yield the emission rate.

A. Ultimate Analysis Methods:
Ultimate analysis was used to determine the compositions of each element with their respective amounts in percentages.The following methods were deplored for the analysis:

1) Determination of Carbon and Hydrogen Content
The Liebig method which is a standard method (ASTM D3178) was used for this analysis.

3) Determination of Sulphur Content
The (ASTM D1552) General Bomb Method was used for the analysis.
To calculate the sulphur content; the following relationship was used: Where P = grams of BaSO4 obtained from sample B = grams of BaSO4 obtained from blank W = grams of sample used.

4) Determination of Oxygen Content
Oxygen is determined by the subtracting the percentages of other elemental compositions obtained from 100%.
%  = 100 − ( +  +  +  + %ℎ)   Hydrocarbons being the most vital combustion fuel contains C, H and S .However, O and N are particularly necessary because they are part of the air composition required to aid combustion .This standard laboratory test predict the percentages of the various elements through an ultimate analysis test procedure .The elemental composition of C, H, S, N and O are feasible and subsequently utilized to predict the empirical formula of the fuel oil .This empirical formula necessitate the prediction of the reaction behavioral of the oil .The combustion of the oil heralds oxidized forms of this constituents and its proportion is determined by the combustion pathway, this pathway could be complete combustion or incomplete combustion .Depending on the combustion pathway followed and the basic characteristics of the element the emission rate could be predicted .This method is very vital for evaluation and measurement of emission rate for facilities where logistics could present a challenge in accessing the stack emission with gas detectors .However, it is worthy to note that this method uses basic standard conditions as assumptions for calculation, therefore testing and compassion with known emission rates of the fuel oil with some chemical characteristics is vital.

2 )
Determination of Nitrogen ContentThe Kjedahl method was used for this analysis.The nitrogen content is estimated with the following relationship: %  = (( * )−( * )−( * )) 1.4007 *  (3) Where: Emission Rate Estimation of Fuel Oil in A Combustion System Using Empirical Method N. Harry-Ngei, I. Ubong and E. Ojong E= VH2SO4 = mL standard H2SO4 pipetted into flask for sample I = VNaOH = mL standard NaOH used to titrate sample F = N H2SO4 = Normality of H2SO4 H = N NaOH = Normality of NaOH G = VBK = mL standard NaOH used to titrate 1mL standard H2SO4 minus B B = mL standard NaOH used to titrate reagent blank distilled into H2SO4 1.4007 = milliequivalent weight of nitrogen * 100 W = sample weight