ABSTRACT
One of the biggest sources of air pollution in industrial areas is the exhaust from boilers, furnaces and incinerator stacks, which in order to reduce this pollution, companies are required to measure and monitor and consequently reduce the amount of pollution. Considering the multiplicity of measurement parameters, this study defined an equivalent index including all parameters. According to the measured data from the emission of the stationary resources of the petrochemical industry located in the two special economic zones of MAHSHAR and ASSALUYEH and also the nature of the production processes, the obvious pollution parameters were identified. By using the weighting of the parameters regarding to their importance, a multiple linear equation was obtained. The data calculated from this formula can be used as a quantifies index for overall assessment of regulatory organizations. This index, which is called EEI (Exhaust Emission Index), is a linear equation of the sum of several prominent and important sub-indices identified based on the measured data. In fact, this concept involves a quick assessment of the stacks based on the emission parameters that determines the health of the process performance.

Introduction
Due to the large number of parameters required to be measured in short time intervals, every industry after a period of measurement, identifies the nature of the pollutants of its emitted gases and makes them the basis of its routine measurement. In each of the production processes of the petrochemical industry, according to the type of product, the characteristic compounds of the gases released into the atmosphere can be identified after a certain period of time, subject to all the different operational conditions including start-up, normal operation and shutdowns.
Air Quality Index (AQI) is a measure of ambient air pollution that is used to quantify air pollution. In fact, the air quality index is a key tool for knowing the air quality and determining its pollution level. Studies have been done to create an index of this type in various industries, including the calculation and use of EEI to check the performance of gasoline-burning vehicles [1]. The index is a new scientific approach proposed to evaluate a car's emission performance along the lines of an air quality index (AQI).
the definition of the same type of index as a function of the operational performance of jet engine turbines, the amount of fuel flow ratio to air and atmospheric conditions, to calculate the amount of output pollution [2].
In another similar work of the same type, which can be improved, regarding the estimation of the pollution index caused by combustion in jet engine turbines [3]. In this case, a multi-layer feedforward neural network has been designed, which uses fuel flow, air-to-fuel ratio and Turbine speed as input data to network and CO, NOx, CO2 and unburnt hydrocarbon pollution indicators are estimated as the output data of this network.
Inspired by the study conducted using neural networks [3], the basis of further work after this research will be the design of a neural network to estimate the amount of pollution emitted from stacks using operating conditions in order to avoid repeated measurements and reduce the problems of using local analyzers.
The inspection and maintenance programs exist in all of industries, aiming at efficiencies improvements and emission reduction through exhaust emission monitoring and compliance policy to the extant norms. However, considering the absence of an intra-system approach, the higher success rate of all equipment towards compliance policy remains a grey area. The paper attempts to investigate this issue through the application of an exhaust emission index (EEI) for combustion and operational stationary sources in the petrochemical industries.

Methodology
This study started by focusing on the analysis of measured multi-year analysis of emitted gases from combustion and process of petrochemical plants located in MAHSHAR And ASSALUYEH regions. Among these data, the parameters of SOX, NOx and CO, PM, HCL, NH3, H2S and BTEX, which has the most importance in air pollution, was considered as the basis and variable. By using these values, a comprehensive index was defined under the title of EEI, including all the above influential parameters in a single number, which resulted in a linear equation. Actually, the EEI index as a quick and brief tool derived from the AQI to combine all possible pollutants in a numerical value is used in identifying and predicting how polluting a process produces.

Regarding to the different studies, the EEI as well as AQI is based on various mathematical formulae that is used to evaluate a stack’s state showing how much pollution it emits. By considering this subject and lots of trial and error, an equation was created from the sum of several sub-indexes with proportional weighting coefficients. These sub-indices are obtained by dividing the number by the value of the standard limit released to the atmosphere and then to the power of 2. The weights assigned to each of these sub-indices are proportional to the region and the importance of each parameter in the formula is defined as 1.5 for SOX, NOx and CO parameters and 1 for PM, HCL, NH3, H2S and BTEX parameters.


Conclusion

According to the study conducted and the actual data measured from the exhaust emission of petrochemical companies in MAHSHAR and ASSALUYEH Special Economic Zones, it was concluded that with the current conditions and no change in the process, the EEI equivalent index calculated in this research as a brief and quick tool for evaluating and sometimes ranking companies is very useful. And also, it is an indicator stating how much pollution a process emits and, as a result, recommend a variety of solutions or directions to improve the plant’s performance. In continuation to the research, by converting a numerical value into a qualitative expression classified as "excellent", "good", "healthy", "unhealthy", "very unhealthy" and "dangerous", It is also tangible for the general public.
Considering that this index is defined for a specific petrochemical process, with a fundamental change or the addition of a new production process, it is necessary to measure all the parameters required by the environmental organization again in a continuous period of time to determine whether another pollutant parameter is added to this formula, or perhaps a parameter should be removed, in which case the formula for calculating the equivalent index should be changed and redefined.