Costs and Savings
Undoubtedly there are vested interests on all sides that can spin an argument either way. In the case of steam air decoke, many of the costs are hidden, with further likely to be consequential at a later date. Pigging Companies will inevitably make commercial sales pitches based on real or promised financial gains.
So, salesmanship to one side... what is the real picture on costs?
When looking commercially at the respective procedures of pig and steam air decoking, costs may be separated into two composite elements of short term pure & visible costs, as well as hidden & consequential costs. With Steam Air Decoking it may be recognised there are opportunity costs within those refineries in the developed World where traditional skills and practices have been originally trained and well maintained over many years.
Many Steam Air Decoking costs can be invisibly absorbed. Steam can be seen as a free by-product, and fuel gas costs can be obscured through easy allocation to Process. The absence of an external physical payment can deceive budgetary management into seeing Steam Air Decoking as a cost free exercise. If there’s no invoice, and no cheque to be written, then it must be free!
Although mindful of all these reasonable points, cost identification of Steam Air Decoking remains difficult, and there will inevitably be much variation from Country to Country. In short term pure and visible cost terms, it seems that a pigging decoke may be approximately twice the cost of an internal steam air decoke.
However, for the purposes of a helpful commercial example, we might take a four pass fired heater, typically a delayed coker or visbreaker, containing a lineal total of 8,000 tube feet.
Steam Air Decoking hidden & consequential costs often relate closely to factors of timing, and the losses caused by downtime and tube damage. Downtime is the easier to quantify with the value in operation of a DCU represented by the often quoted figure of $20,000 per hour. In consideration of downtime duration, the pig decoke wins handsomely every time.
It is therefore a critical exercise to compare the duration of decoking, as follows:
| Steam Air Decoke | Mechanical Decoke | ||
|---|---|---|---|
| Elements of Procedure | Duration | Elements of Procedure | Duration |
| Flush out & cool down | 10 hours | Flush out & cool down | 10 hours |
| Swing elbows - steam connection | 4 hours | Swing elbows - steam connection | 4 hours |
| Decoking | 48 hours | Decoking (including one changeover) | 30 hours |
| Cool down | 8 hours | Spring elbows - process connection | 4 hours |
| Spring elbows - process connection | 4 hours | Return to service | |
| Return to service | |||
| Total time taken Oil to Oil | 74 hours | Total time taken Oil to Oil | 48 hours |
Costs for Pig Decoke
Contractor charge estimate: €30,000 - €60,000
Other costs – mechanical attendance only
Costs for Steam Air Decoke
internal identified cost estimate: €17,500 - €25,000
Add downtime – 26 hours: €250,000 - €500,000
Additional safety costs ?
Add impact on tube longevity: ?
Please note: Cost through tube damage is a long term consideration. Material and labour costs for re-tubing are high, but the biggest cost in such circumstances is down time. Contractor charges for pig decoking can significantly reduce when carried out during multiple heater operations. As the Contractor’s biggest cost is mobilisation, a second and third heater decoked in the same maintenance visit can produce reductions making the unit charge attractively less. Outside North America & Europe, Contractor costs are likely to be higher in order to incorporate additional mobilisation and other costs.
In a long shutdown planned to take weeks, it can be argued that such a circumstance will not gain in any way from saved time through faster & more efficient decoking. Yet a pig decoke will still clean efficiently, quickly and with proper measurement. The tube damage associated with a steam air decoke is avoided, and the Client is left with a clean heater after a predictable, safe and trouble free decoking experience.
If the cost case is made for a pig decoke – then why cokebuster pigging?
Hidden & consequential costs are clearly reduced, as follows:
1. Quality of the decoking.
Although pig decoking grew in popularity through the 1990s as a beneficial replacement of Steam Air Decoking (& other methods), its scientific development then stagnated. Through new investment and scientific advance, the cokebuster pig now changes that. Not only the new cokebuster pig, but the whole concept of service with complete package of pigs + measurement technology + advanced machinery + quality personnel through training and experience... this produces a proven new departure from ordinary pig decoking.
2. Are the tubes clean?
With tubes properly and thoroughly cleaned, the heater can simply be put back into service with a confident expectation of the fullest run length. The degree to which tubes are clean can be scientifically measured and such measurement promptly displayed for refinery engineers to consider. Recorded measurements can be used time after time for ongoing management of the heater.
3. Are the tubes damaged?
With cokebusters – no. One of our representatives will be pleased to arrange a visit and closely discuss all aspects of our technology. With undamaged tubes, the heater remains in service longer, it refines more efficiently, and has increased longevity in its lifetime’s service.
4. Management & Safety.
Your regional cokebusters provider is commercially part of the whole enterprise. He is not a Franchise looking only for his commission, but he is a committed individual who has every commercial and genuine reason to offer his Clients the total care package. Representatives visiting Client sites have direct access to the most senior management levels, matched only by their similar direct access to the hands-on personnel who will later conduct the site operation. It is not just a slogan to say this is “World Class Technology – locally delivered.”
5. Environment – a different kind of cost.
Financial penalties have been levied against refineries for exceeding acceptable emission levels through use of the steam air decoking procedure. The United States Department of Energy & Office of Industrial Technologies commissioned a treatise focusing on the Petroleum Refining Industry in order to clarify the varieties of refining processes, at the same time identifying environmental impacts of the Industry. In a thorough and wide ranging analysis containing 124 pages, the treatise examines in detail all refining processes and draws on technical studies to produce a definitive appraisal of production practices along with associated control and measurement of emissions.
Some enormous figures clearly identify the size of this global pollution issue:-
"Per year, carbon & carbon equivalent emissions in excess of 60 million metric tonnes, as well as in excess of 34,000 metric tonnes of toxic chemicals, are produced by the Petroleum Refining Industry."
"A large source of air emissions is process heaters and boilers (CO, SOx, NOx). In addition, some processes create considerable amounts of particulate and other emissions from catalyst regeneration or decoking processes."
With cokebusters pigging, removed coke automatically passes through on-board primary & secondary filtration. From the last 4 pass visbreaker we decoked, the Client was left with over 10 tonnes of coke solids. It’s his coke – we left it there!