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

SO2 and NOx emissions from Kuwait power stations in years 2001 and 2004 and evaluation of the impact of these emissions on air quality using Industrial Sources Complex Short Term (ISCST) model

Comprehensive emission inventories for 2001 and 2004 for Kuwait’s main power stations located at Al-Doha and Al-Subyia have been prepared. These inventories are inserted, in conjunction with meteorological data, into the Source Complex model for Short Term Dispersion (ISCST4.5) to predict ambient ground level concentrations of sulphur dioxide (SO2) and nitrogen oxides (NOx) at selected receptors for years 2001 and 2004. The comparison of the results obtained for these two years show the influence of increase in emission rates due to urban and industrial growth. For model validation, computed results are compared with the measured daily average values of SO2 and NOx collected at a fixed Kuwait Environment Protection Agency air quality monitoring station located at the roof of polyclinic in Rabia. Individual contributions of each power station to the highest predicted values are assessed. The five highest hourly, daily and annual ground level concentration values under prevailing meteorological conditions are compared for 2001 and 2004. It is found that the hourly mean concentrations are strongly influenced by the prevailing meteorological conditions. The effect of meteorological conditions has not been that dominant for the daily and annual mean values and the predicted values for 2004 are higher than 2001, simply corresponding to a high emission rates, especially in summer months. Top fifty daily average values show a slope of 0.806 for 2001 which means that the model predictions are 20% less than the observed levels. However, the predicted slope for 2004 is 0.96 and the model predictions are in very close agreement with the observed data

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

Comparison of the diagraph and FAULTFINDER methods of fault tree synthesis for nested control systems

Comparison of the diagraph and FAULTFINDER methods of fault tree synthesis for nested control system