Oil refinery fuel oil firing on furnaces and boilers
Oil refinery fuel oil firing on furnaces and boilers
(OP)
“Particulate matter emissions generally are classified into two categories, PM and PM10. PM10 is a particulate matter with diameter less than 10 microns. All particulate matter can pose a health problem. However, the greatest concern is with PM10, because of its ability to bypass the body's natural filtering system.
PM emissions are primarily dependent on the grade of fuel fired in the boiler. Generally, PM levels from natural gas are significantly lower than those of oils. Distillate oils result in much lower particulate emissions than residual oils.
When burning heavy oils, particulate levels mainly depend on four fuel constituents: sulphur, ash, carbon residue, and asphalenes. These constituents exist in fuel oils, particularly residual oils, and have a major effect on particulate emissions. By knowing the fuel constituent levels, the particulate emissions for the oil can be estimated.
Methods of particulate control vary for different types and sizes of boilers. For utility boilers, electrostatic precipitators, scrubbers, and bughouses are commonly utilized. For industrial and commercial boilers, the most effective method is to utilize clean fuels. The emission levels of particulate matter can be lowered by switching from a residual to distillate oil or by switching from distillate oil to a natural gas. Additionally, through proper burner set-up, adjustment and maintenance, particulate emissions can be minimized, but not to the extent accomplished by switching fuels”.
Without great investments, particle emissions can be reduced of the following forms:
Use fuel oils with low rates of nitrogen and sulphur.
Optimise atomisation pressure of fuel oil.
Good regulation of the relationship air/fuel oil.
Appropriate burners maintenance.
Knowing that there is a relationship of NOx emissions, with the contained nitrogen radicals in fuel, exists the possibility to mix fuel oil n. º 6 with fuel oil n. º 2 of low nitrogen in order to dilute the amount of nitrogen radicals, thus minimizing the emissions.
Another form of emissions reduction is to use fuel additives to control fuel firing.
Comments from the forum on the above subject would be appreciated.
Thanks
Luis Marques
Talk To Other Members
RE: Oil refinery fuel oil firing on furnaces and boilers
Please give us some specifics to comment on. All the generalities you list above are true.
rmw
RE: Oil refinery fuel oil firing on furnaces and boilers
We burn process residuum, fuel gas and off-gas in furnace heaters burners. In utility boilers burners we burn process residuum and fuel gas. Our process residuum has an average rate of 1.5% S, and an average viscosity of 113 Cst at 100ºC and 30 Cst at 135ºC. Average density of the process residuum is 1.01.
The vanadium in process residuum is about 60-ppm average. We have not nickel analyses values and we also have not analyses values of N radicals in the process residuum. Our Nox emission values varies from 500mg up to 765mg, No goes from 400 to 500mg, So2 Varies from 1000 to 1250mg, Co varies from 10 to 20mg, O2 is about 5%. The numbers above are not typical because every thing is dependent on the feed crude mix diet we process.
RE: Oil refinery fuel oil firing on furnaces and boilers
Efficiency depends on optimising the conditions for combustion.
Pollution control measures can be counter to efficiency. For example, it is claimed that NOX reduction measures for large diesle engines increase fuel consumption by around 4%. This is a feature of the combustion control.
Sulphur, on the other hand, is a feature of the fuel. The more there is in the fuel, the more is released as SOX, unless exhaust gas cleaning is employed.
Marine pollution control is becoming increasingly strict. There is now a global cap on sulphur in heavy fuel that isn't, at the moment, too onerous but in special sulphur control areas the limit is 1.5% in fuel and by 2008 this will probably be reduced to 0.5%. This last is part of the MARPOL ANNEX VI regulation 18 imposed by the EU. But it is expected that this legislation will become global.
In case anyone thinks that this is just for mariners to worry about, take a look at these links:
http://www.epa.gov/Region2/news/2001/01075.htm
http://www.epa.gov/Region2/news/2001/01078.htm
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Having fallen foul of the EPA the power stations operated by PREPA in Puerto Rico have had some stringent sulphur caps imposed for heavy fuel oils. They were burning Venesuelan Bunker C.
So we should all be prepared for some pretty tight controls for all land and marine based engine and burner operations and sometimes, despite the prevailing legislation, for even more strict controls when caught napping!
On the efficiency front, it has been usual in burner operations to rely on s strategy for burner fuel heating control (to optimise the viscosity at the nozzle or burner jet) based on three activities:
1) regular sampling and analysis to determine the optimum temperature to heat the oil to.
2) flame inspections
3) excess oxygen
This is a strategy based on using temperature as the control parameter for fuel oil heating. It carries a cost penalty, even at the cost of the uncontrolled qualities of residium refiners burn, which can run to $100,000s a year just on the use of excess oxygen.
In the case of PREPA they were using viscometers for heater control as this is more efficient and automatically compensates for fuel quality variations, but the technology they were using was prone to failure and they spent considerable time under "last good temperature" control.
Part of the excercise consequent on their Consent Decree was to trial and install more reliable viscometers. The EPA were mandating they should use two viscometers per burner, one duty and one standby.
However, their trials provided one of the newer viscometers which proved so reliable they were able to satisfy EPA that they only needed one per burner.
The message is that however well we have managed our operations till now, there is increasingly tough legislation coming that many would be advised to plan for. We are not talking of small fines (the cost to prepa is significant) but, in the marine sector at least, criminal procedings with jail terms attached.
JMW
www.ViscoAnalyser.com
RE: Oil refinery fuel oil firing on furnaces and boilers
http://www.coen.com/i_html/white_liquidfuel.html
JMW
www.ViscoAnalyser.com