Oil refinery fuel oil firing on furnaces and boilers 1

It is a very broad open ended question. What are you firing, and with what type of firing equipment, and what alternative fuels do you have present to 'switch' to or 'blend' with?

Please give us some specifics to comment on. All the generalities you list above are true.

rmw

Rmv

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.

There are two aspects to fuel fired boilers: efficiency and pollution.
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:

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

Incidentally, there is a good article on burner operations here:


JMW