شبيه سازي رياضي پراكنش آلاينده SO2 ناشي از احتراق مشعل، مطالعه موردي: سكوي نفت و گاز ابوذر در جزيره خارك

SO2 dispersion mathematical simulation of flare combustion, case study: Aboozar oil and gas platform in Kharg Island

پراكنش آلاينده‌هاي هوا در واحدهاي صنعتي يكي از مواردي است كه همواره محيط زيست و اكوسيستم منطقه‌هاي مجاور را تحت تاثير قرار مي‌دهد و مي‌تواند در دراز مدت زندگي افراد ساكن در مجاورت اين گونه واحدها را با مشكلات جدي مواجه سازد. مدل‌هاي انتشار آلودگي ابزار مفيدي جهت شناخت رفتار آلاينده پس از خروج از منبع بوده و اندازه‌گيري‌هاي زياد و پر هزينه را غير ضروري مي‌نمايد. در اين تحقيق دي اكسيد گوگرد (SO2) كه يكي از آلاينده‌هاي خطرناك ناشي از سوزاندن تركيبات گازي مختلف در خروجي مشعل‌ها مي‌باشد به عنوان مدل آلاينده و مجتمع نفت و گاز ابوذر كه شامل 3 سكوي بهره برداري و 10 سكوي سرچاهي مي‌باشد و فرايند اشتعال مشعل‌ها به عنوان اصلي‌ترين چالش زيست محيطي اين مجتمع محسوب مي گردد به عنوان منطقه مورد مطالعه در نظر گرفته شده است. جهت مدلسازي فرايند انتشار آلاينده، ابتدا اطلاعات هواشناسي با نرم افزار View Rammet پردازش شد و ارتفاع شعله با توجه به سرعت باد و گرماي خالص آزاد شده در مشعل محاسبه گرديد. سپس غلظت SO2 خروجي از مشعل، از طريق شبيه‌سازي كامپيوتري به وسيله نرم افزار AERMOD View، در محدوده ي 150 كيلومترمربعي، محاسبه گرديد. خروجي نرم افزار كه همان گراف حاوي زون هاي اصلي تمركز آلاينده مي باشد، نشان داد كه در حالات در نظر گرفته شده غلظت SO2 در تمامي سكوهاي بهره برداري و سرچاهي اطراف مشعل از مقادير استاندارد جهت 8 ساعت كار مداوم و همچنين استاندارد هاي سازمان حفاظت محيط زيست آمريكا، تجاوز مي‌نمايد.

Aboozar oil field is located around 75 km south west of Kharg Island, in Bushehr state, southern part of Iran. Aboozar oil and gas complex contains 3 production platforms: AboozarA (AA), AboozarB (AB) and AboozarC (AC). Each of them includes some oil and gas wells which feed the process facilities and in addition each one comprises separate flare system in which separated gas is flared over there. Aboozar field offshore process is limited to oil and gas separation, and the produced gas from the separators is disposed in a common flare system in which more than 36 million standard cubic feet gas mixture are daily being flared. Flaring is the common practice of burning off unwanted, flammable gases via combustion in an openatmosphere, nonpremixed flame. This gas may be deemed uneconomic to process (i.e. if it is far from a gas pipeline or if it is ‘sour’ and contains trace amounts of toxic H2S) or it may occur due to leakages, purges, or an emergency release of gas in a facility. The flaring process can produce different pollutants such as SO2 as an index pollutant which has a substantial role in the environment and human health. SO2 is one the most major pollutants emitted from production platform flares due to gas mixture combustion.This pollutant concentration depends on the composition of gas sent to the flare combustion chamber and also flare combustion efficiency. To specify prevention and mitigation measures, it is needed to know about air pollutants concentration. In highly polluted places, to monitor amount of each pollutant all over the region, we should always measure concentration of pollutant by pollutant emission modeling from the source not to need costly routinely measurement by some special devices. Nowadays, air pollution models are routinely used in environmental impact assessments, risk analysis and emergency planning, and source apportionment studies. A dispersion model is essentially a computational procedure for predicting concentrations downwind of a pollutant source, based on knowledge of the emissions characteristics. These models is based on mathematical calculation and used to estimate pollutants concentration. As the project target, flare modeling as a point source to investigate its concentration around the platforms to understand whether the concentration of pollutant is more than the standard limit value or not was considered. In this project, we have simulated SO2 emission by means of an advanced model based upon the Gaussian model, and we tried to find out SO2 dispersion pathway after flame. In this study, Aboozar production platform flare SO2 dispersion has been simulated by means of AERMOD View software and its concentration was determined. Flare flame length and height was determined, using flare flame net heat release value, to achieve flare effective height. In addition, meteorological data was preprocessed in Rammet View Software to input in main software. Final results showed that SO2 estimated concentration is being exceeded from threshold limit value all over the complex in all living quarters and production and wellhead platforms based upon the American Conference of Governmental Industrial Hygienists standard.