Ensuring air quality within the refinery’s boundaries and in the surrounding area is an obligation for the company that arises not only from legal requirements but also from its commitment to the principles of Corporate Social Responsibility.
To protect and improve air quality, air pollutant emissions are monitored using a wide range of techniques; state-of-the-art measurement equipment – continuously renewed and upgraded – is employed. The measurement programme, including continuous as well as intermittent readings, covers both, point and diffuses emissions sources.
In the peripheral zone of the refinery, air quality is monitored by four appropriately equipped stations:
- Three fixed monitoring stations capable of continuously measuring the concentration of hydrogen sulphide (H2S) and sulphur dioxide (SO2).
- A mobile station equipped with automated state-of-art measuring and recording devices, which can perform and record a wide range of measurements, including meteorological parameters and the concentrations of nitrogen oxides (ΝΟ, ΝΟ2, ΝΟx), sulphur dioxide (SO2) , hydrogen sulphide (H2S), carbon monoxide (CO), total hydrocarbons, hydrocarbons excluding methane (CH4), benzene, and particulate matter PM10 and PM2,5.
Within the refinery, flue gases emitted by the large combustion plants (point emissions) of the Fuels, Hydrocracking and Lubricants complexes are continuously monitored by online analysers. The parameters measured are: temperature, pressure, flow and concentration of oxygen, nitrogen oxides, sulphur dioxide and particulate matter PM10.
At the Catalytic Cracking unit, continuous monitoring of temperature, humidity, emissions’ flow, carbon monoxide and of all the above pollutants is carried out. It should be noted that the analysers are connected to the refinery’s Distributed Control System (DCS), a configuration that allows the complete control of the combustion taking place in the furnaces.
An automated performance control system operates at the Sulphur Recovery units, which continuously monitors and records Η2S concentrations at the entry points, and Η2S and SO2 concentrations at the exit points of those units. Also, the Η2S/SO2 ratio is continuously measured, recorded and adjusted, so as to ensure maximization of recovery performance (which is 99.5% for the new plants U6700-U7700 and also for the new, SCOT-type unit at the New Crude Distillation complex commissioned in 2010, and 99.0% for the two older units). Operation of all the sulphur recovery units, and the incinerators, is automatically controlled via the refinery’s Distributed Control System (DCS).
As in the case of the stacks of the large combustion plants, the supply lines of the flares of both the Fuels production unit and the Hydrocracker unit are subject to continuous measurement of total sulphur concentration. The analysers installed are also connected to the DCS.
Emissions from the refinery’s other stacks are monitored periodically by an accredited external organisation.
Fugitive emissions- LDAR
A modern refinery comprises lots of different types of installed equipment, through which large quantities of crude oil and feedstock circulate, as well as intermediates and final products. In such a system, it is to be expected that there will be particular points with a higher risk of hydrocarbons being accidentally released into the atmosphere. In order to contain such fugitive emissions from equipment, a programme of periodic checks of selected equipment points is implemented for detecting fugitive emissions and immediately repairing the leaks causing these emissions. In the industry, this is known as Leak Detection and Repair (LDAR) Programme, and is based on the EPA 21 method of the United States Environmental Protection Agency.