Environmental impact of fluid catalytic cracking unit in a petroleum refining complex

The fluid catalytic cracking (FCC) unit is of great importance in petroleum refining industries as it treats heavy fractions from various process units to produce light ends (valuable products). The FCC unit feedstock consists of heavy hydrocarbon with high sulphur contents and the catalyst in use is zeolite impregnated with rare earth metals i.e. lanthanum and cerium oxides. The catalytic cracking reaction is endothermic and takes place at elevated temperature in a fluidised bed reactor generating sulphur-contaminated coke on the catalyst. In the regenerator, coke is completely burnt producing SO2, particulate matter emissions. The impact of the FCC unit is assessed in the immediate neighborhood of the refinery. Emission inventories for years 2008 and 2009 for both SO2 and PM have been calculated based on real operational data. Comprehensive meteorological data for years 2005 – 2009 are obtained and preprocessed to generate planetary boundary layer parameters using Aermet (Aermod preprocessor). Aermod (US EPA approved dispersion model) is applied to predict ground level concentrations of both pollutants in the selected study area. Model output is validated with the corresponding measured values at discrete receptors. The highest hourly SO2 predicted concentrations for both years 2008 and 2009 exceeded the corresponding Kuwait EPA ambient air standard, mainly due to elevated emission rates and the prevailing calm and other meteorological conditions. The highest daily SO2 predicted concentrations also exceeded the Kuwait EPA allowable limit due to high emission rates, while meteorological parameters influence is dampened. Hourly average predicted PM concentrations showed similar variation into SO2 in different location. The daily average predicted PM concentrations are lower than US EPA specified limit. An extensive parametric study has been conducted using three scenarios, stack diameter, stack height and emission rates. It is noticed that stack diameter has no effect on ground level concentration, as stack exit velocity is a function of the square of stack diameter. With the increase in stack height, the predicted concentrations decrease showing an inverse relation. The influence of the emission rate is linearly related to the computed ground level concentrations SO2 additives are tested for SO2 emissions reduction. In the year 2008, reduction of SO2 annual total emission by 43% results in full compliance with Kuwait EPA hourly specified limit, using an appropriate amount of additives. Similarly, 57% reduction of SO2 annual total emission leads to no exceedance in predicted concentrations for the year 2009. The application of the state of the art technology, ESP has reduced about 90% of PM emissions for the year 2009

Inventories of SO2 and particulate matter emissions from fluid catalytic cracking units in petroleum refineries

Fluid catalytic cracking (FCC) of heavy ends to high value liquid fuels is a common unit operation in oil refineries. In this process the heavy feedstock which contains sulphur is cracked to light products. Sulphur content is hence redistributed in the liquid and gaseous products and coke of the catalyst used in this process. The coke is later burnt in the regenerator releasing sulphur into the discharged flue gas as SO2. In the present work, comprehensive emission inventories for a FCC unit in a typical oil refinery are prepared. These inventories are based on calculations which assume complete combustion of catalyst coke in the regenerator. Yearly material balances for both SO2 and particulate matters (PM) emissions are carried out taking into account seasonal variations in the operation of the process unit. The results presented in this paper reflect the variation of sulphur in feedstock originating from various units in the refinery. The refinery operations are not dependant on seasons but controlled by market driven conditions to maximize the profit. The seasonal impact on refinery emissions is minimal due to its operation at optimum capacity fulfilling the international market demand. The data presented and analyzed here can be used to assess the hazardous impact of SO2 and particulate matter (PM) emissions on surrounding areas of the refinery

Fluid catalytic cracking unit emissions and their impact

Fluid catalytic cracking unit is of great importance in petroleum refining industries as it treats heavy fractions from various process units to produce light ends (valuable products). FCC unit feedstock consists of heavy hydrocarbon with high sulfur contents, and the catalyst in use is zeolite impregnated with rare earth metals, i.e., lanthanum and cerium. Catalytic cracking reaction takes place at elevated temperature in fluidized bed reactor generating sulfur-contaminated coke on the catalyst with large quantity of attrited catalyst fines. In the regenerator, coke is completely burnt producing SO2, PM emissions. The impact of the FCC unit is assessed in the immediate neighborhood of the refinery. Year-long emission inventories for both SO2 and PM have been prepared for one of the major petroleum refining industry in Kuwait. The corresponding comprehensive meteorological data are obtained and preprocessed using Aermet (Aermod preprocessor). US EPA approved dispersion model, Aermod, is used to predict ground level concentrations of both pollutants in the selected study area. Model output is validated with measured values at discrete receptors, and an extensive parametric study has been conducted using three scenarios, stack diameter, stack height, and emission rate. It is noticed that stack diameter has no effect on ground level concentration, as stack exit velocity is a function of stack diameter. With the increase in stack height, the predicted concentrations decrease showing an inverse relation. The influence of the emission rate is linearly related to the computed ground level concentrations

Impact of gaseous and particulate matter emission for fluid catalytic cracking units

Fluid catalytic cracking unit is a major part of petroleum refineries as it treats heavy fractions from various process units to produce light ends (valuable products). FCC unit feedstock consists of heavy hydrocarbon with high sulphur contents and the catalyst used is zeolite impregnated with rare earth metals i.e. Lanthanum and Cerium. Catalytic cracking reaction takes place at an elevated temperature in fluidized bed reactors generating sulphur-contaminated coke on the catalyst with large quantity of attrited catalyst fines. In the regenerator, coke is completely burnt producing SO2, PM emissions are mainly due to high attrition of cold makeup catalyst charge and operating conditions, vapour velocity particle velocity, particle collision and particle degradation. This study is dedicated to the quantitative analysis of the impact of harmful emissions resulting from FCC units on the environment