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Nothing tops working with Heavy Oil in a developing country in sheer frustration factor - and in the end nothing tops it in the expense of actually making a Heavy Oil Combustion System work in a fashion that is acceptably straightforward for the End User. We are highly experienced with commissioning and remediating Heavy Oil projects. A Brief HistoryHeavy Oil was at one time a refined product of the Petroleum Industry. The Crude was pumped into a Cracking Tower and the lighter, useful constituents boiled off. The residue at the bottom of the Tower was tested and when it reached a certain specification - such as viscosity - it was pumped out and marketed as a specified Residual Fuel Oil (ASTM #6 and/or Bunker C for example). This is and was commonly used to fire large boilers, such as in Ships and Utility Power Generating Stations. Working with this type of Fuel certainly has its' problems - the largest of which is the difficulty and expense of preparing the Oil for combustion and the Products of Combustion that result. The Heavy Oil that we encounter today no longer conforms to what is expected here in the United States. Refining technology has been improved greatly, and the market for more and more heavier constituents of the Crude Oil have opened. This makes it economically attractive to the Refiners to boil down the Crude much further to extract more from it. This leaves an extremely thick Tar-like substance - so thick that this writer has actually had the opportunity to walk on a cooled "Lagoon" of this stuff that was at least several acres across! The installation where this experience was had "harvested" this Fuel by chopping it out of the Lagoon with hot shovels and loading it onto Trucks in solid form, and these blocks of fuel were carried to the top of the Storage Tank and dropped in. The Steam Grates at the bottom of the Tank melted the blocks and the convective movement generated by the heat kept things stirred up. It is safe to say that this was a viscosity problem that was well outside the range encountered with #6 or Bunker C! It is offered quite cheaply though, and is a terrific Fuel. TroubleShooters rule; if the Fuel is cheap, the equipment required to burn it will be expensive. And if it isn't, getting it to work acceptably will be. To make matters worse, the Refiners are often handed a specification for the product by a prospective User - for example a Customer of one of our Clients receives the specification for the fuel required to operate the intended equipment. They approach the Refiner and ask if fuel meeting the specification (primarily viscosity) is available. The Refiner, seeing an opportunity to get paid for what they often pay to dispose of, says "Sure, no problem!" The Refiner then "blends" some of the lighter, less useful (or profitable) constituents that were boiled off earlier - back into the Residual Oil - until the Viscosity specification is met. This is then trucked to the End User and the huge Storage Tanks are filled to the top with a Fuel that can not be burned by the equipment that was installed. Then, months of frustration ensue. Often many people try to make the Combustion System work with the Fuel - universally the concept is that the Burner should ignite with a "push of a button" and it just won't ignite at all. Hundreds of pounds of Propane (for the Pilot Burner) are consumed - the End User was told specifically that the Pilot would only operate for a few seconds before lighting the Main Burner and it has been cycled hundreds of times, resulting in hours of Pilot operation. They have acquired Propane through illegal channels, as in many countries its' use for other than cooking is considered a "Crime against the People". So the tension mounts. We have been to several sites where the Fuel was clearly not even close to the specification. Samples that were drawn for analysis by the End User invariably checked out as straight #6 with absolutely no water, while the Oil at the site was solid at 60oF and yielded 15% water when distilled. We have also worked at one site where samples drawn by the technician have been scurried away by the End User because "the containers were not suitable for travel to the U.S.". When returned, the contents obviously were not what was in the original unsuitable containers - even the color and smell were markedly different. This sort of problem removes another critical tool required for correctly diagnosing a problem, which compounds time and expenses even further. Industrial Fuels have become more difficult to control correctly for several reasons - none addressed by the typical Specification for ASTM #6 or Bunker C. The first reason is that it is no longer homogeneous - it has been chemically separated and mechanically re-blended. So now there are light constituents within the Blend that boil at a temperature considerably lower than water and separate very easily - leading to stratification in the Storage Tanks and even more handling problems. The second reason is that it has significant water in it - often the Refiner in a developing country has no means of transporting the Residual to the Blending Tank other than Steam Pressure. So this Fuel has another Low Boiler added - the problem here being that it becomes difficult to distinguish which problem is worse - the Low Low Boiler or the Low Boiler! And there is a third problem - the Refiner is usually looking at a Specification that indicates a range - and he is going to create a blend that meets the easiest (or cheapest) target to hit. This generally means that the lighter oil will likely be from the higher end of the viscosity range - it requires less of the lighter (and therefore more marketable) constituents to be wasted in making this Heavy Fuel Blend. The Base Residual often has a viscosity that is extremely high (it must if it can support a brute like this writer!) and no matter how much blending is attempted, there is significant content that is still not to spec. This means that a higher temperature is required to bring the Fuel to the viscosity that can be atomized well enough to burn acceptably (let alone ignite!) The bottom line is that if the Fuel must be heated beyond the boiling point of the lightest constituents to reach the target viscosity there will be significant problems with any sort of pressure or volume based controls that might be applied. Some high pressure fuel delivery systems might be able to cope - but the penalty is next to no turndown, something that becomes unacceptable if any range of control is desired. Fuel Control EquipmentAdditional problems with the Fuel Control Equipment have been encountered at almost every site visited. Often the equipment is shipped without the required heating and insulation equipment to keep the piping at the required temperature - drawings typically are noted "by others". The concept of Steam or Electrical Heat Tracing is often completely foreign to engineers in developing countries - they simply don't know how to do it, the materials are not available locally, and the labor that installs it doesn't have a clue. The result, invariably, is Piping that can not keep the Fuel at the temperature required to meet the demands of the Process. The Heaters (or more correctly the "inexpensive" Controls supplied to operate them) used to get the Fuel hot enough to atomize are almost universally incapable of maintaining an accurate temperature. This Delivery Temperature (from the Fuel Train to the Burner) is utterly critical, and becomes more so as the Base Viscosity of the Fuel increases. Steam Heaters (usually "by others") are often controlled by a hand valve that is either opened or closed - the End User has no idea what temperature is required, no indication of the temperature within the Heater, or that the Steam Temperature is determined by the utility supplying it. Electrical Heaters are invariably supplied with ON/OFF Controllers that operate big Contactors that turn the heating coils ON or OFF - causing huge swings in the actual temperature of the Oil. Because of the very high viscosity of the Base Fuel, relatively tiny swings in temperature create exponential swings in the delivered viscosity - often making the Burner appear to be cycled ON and OFF by the Contactor! Many installations that we have encountered had these problems - the Combustion System could be made to function, for a while. Then some process variable would change ever so slightly and the whole Process would collapse - requiring another examination of the issues and a cobbled together temporary solution (and invariably very expensive remediation for facilitating the permanent solution). Flow Control becomes a key issue - particularly when any turndown at all is required. Pressure or Volume based Flow Control becomes a huge problem because any problems related to flashing of Low Boilers in the Fuel increase exponentially as the temperature required to maintain the required viscosity increases. All of the equipment in our experience base that had major operational problems delivered pressure or volume just fine - except what it delivered was in the form of "black shaving cream". This is a problem because now, instead of delivering a controlled flow of Oil the system is delivering a steady flow of foam, whose density varies wildly with the volume of Low Boilers and temperature combined! Even high pressure fuel delivery often requires that Orifices be experimented with to find the most reasonable compromise that keeps the Burner firing while under a fixed load. The reason is that the foam density is also determined by pressure - so choosing an Orifice that works under certain conditions becomes critical. Once any turndown is required, the pressure behind the Orifice changes and everything works differently again. We have developed a system that addresses all of these problems, delivering extremely consistent Fuel Mass to the Burner through a very wide range of turndown. The key to success is maintaining the Fuel at all of the conditions required to atomize correctly at the tip of the Atomizer, not at the Fuel Train - which is often located dozens of feet away from the Burner(s). Most importantly, it is simple, straightforward and completely self-contained. One connects electrical power, the low pressure fuel supply to the input and the output to the Burner. No Heat Tracing, no Insulation, and one pipe connection to a low temperature Plant Circulation Loop. Should you require assistance with a Heavy Oil Project, please do not hesitate to call us - we probably can help no matter what stage of development you are currently in. For obvious reasons, we recommend contacting us before the remediation stage is entered, but we are happy to help regardless.
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