Innovative Cleaning and Inspection Plays a Critical Role in Refinery Debottlenecking

Debottlenecking is all about analyzing each piece of equipment's capacity and time utilization and then recognizing opportunities for increasing throughput with the least capital expenditure.

Every business owner wants to increase production while reducing expenditure. Within the oil, gas, petrochemical, and energy industries, an additional desire - or should we say necessity - is the reduction of CO2 emissions.

Within oil refineries, debottlenecking is about avoiding emergency critical path situations. It is about identifying problems before they become a cause for concern and finishing the large, demanding tasks to shorten shutdowns. Often, these problems are cleaning and inspection-related.

Debottlenecking presents challenges in various areas, one of which targets the quick, efficient cleaning of heat exchangers and other plant assets. Often regarded as a 'traditional' procedure, it is crucial that clients source and encourage a more inventive approach to achieve successful de-scaling, whether for performance or integrity inspection, especially on the more challenging of exchangers, in order to avoid bottlenecking.

For the past thirty years, Tube Tech International has been working with several of the world's largest oil refineries to develop radically innovative cleaning and inspection techniques to assist with debottlenecking activities caused by heavily fouled, complex exchangers or exchangers perceived as "un-cleanable". The companies' innovations have included in-situ and even online cleaning of heat transfer equipment. Previously, local contractors had struggled and needed cranes and scaffolding to produce mediocre cleaning results. With this knowledge, Tube Tech can advise engineers tasked with refinery debottlenecking where cleaning is involved.

Debottlenecking to Save Time, Save Money, and Reduce Emissions

About 50% of financial losses directly related to fouling within any oil refinery are due to the crude distillation unit (CDU). These crude exchangers regularly suffer from scaling of tubes or tube blockages, which thwarts the transfer of heat and substantially reduces overall efficiency and subsequent production throughput.

Such heat exchangers become 'baked' with carbon scale with a high percentage blocked, causing back pressure and poor delta Ts. As a result, these exchangers become critical paths simply because cleaning contractors cannot clean to the required IRIS or Eddy Current standards. That shortcoming eventually leads to a frustrating bottleneck situation, and if the company cannot clean these crude exchangers properly, this limits furnace capacity, which means a costly cut to the operations flow rate. The loss of throughput multiplied by the profit equates to the loss of plant profits. These costs can be huge and often dominate energy losses and have a tremendous impact on the increase in one's CO2 footprint.

100% clean of BP Fin Fans

Several ACC fin-fans serving the coker unit at a BP refinery in Germany had become blocked with a material that consisted of an elastic, cured polymer, similar to rubber, like bathroom sealant. The deposit was pliable but tough and resistant to up to 750 Bar/10kpsi jetting pressures. Once cooled, the deposit tended to harden to a brittle, glass-like consistency. Each unit contained 225 x 10-meter carbon steel tubes terminated by 328mm-deep header boxes. The reduced efficiency of the ACC fin-fans was estimated to cost the refinery around $20,000 daily for each unit.

These exchangers had become critical path items in the refinery's shutdown list because they could only be taken out for maintenance during a scheduled shutdown and because previous high-pressure jetting contractors who had been given six days to clean had struggled to reach the desired inspection standard. An added complication was that replacement bundles had been delayed, so the plan to clean these fin fan exchangers was given to Tube Tech very late in the planning stage. It was essential to reduce time and achieve the correct cleanliness standard significantly—an additional hazard for the cleaning team involved aromatic solvents left behind by a previous chemical cleaning attempt.

The nature and extent of the fouling in the ACCs, which normally handle E3 reformate, was revealed by careful inspection. The fouling to be removed from the tubes varied from a sticky, putty-like substance to crisp, brittle restrictions, including the catalytic (PCA) material remains.

Once on site, cleaning proceeded as planned, with two methods being employed to clean the ACC units' headers and tubes. The first method was based on the well-established SafeTrack- system, while the second utilized a newly-developed self-feeding rigid coiled lance - a hydraulically-driven rotary lance that employs a hydraulically-powered reaming principle with simultaneous pump pressure up to 3500 bar water pressure. The new system applied a high-torque rotary action within the tube, with water, to clean the various consistencies of deposits encountered. It is common for traditional technology to clean the tubes, but the waste ends up in the header boxes, which basically goes back into the clean tubes when the unit is put back online! Tube Tech ensured that 100% of deposits were extracted from the header at source.

"Cleaning these important fin-fan units has always been a problem for us, both in getting them cleaned in the time available and to the required eddy current and IRIS inspection standard, using our usual local contractors. This time, we had a situation where the decision to clean the units was not made until very late in the planning for the shutdown as our replacements had been delayed, reported the Shutdown Manager at BP. As it had been taking six days to clean just one unit, and we wanted to clean at least two, we knew we had to look for an alternative service provider, and we found Tube Tech International. The cleaning went exceptionally well - and so quickly that we got them to clean not just two ACCs but four. We had been planning to order some new ones, so badly were they blocked, but Tube Tech could clean all four to a much higher standard than we have ever seen before, so we have made some great savings."

Understand the Debottlenecking Process - Look at Refinery Needs and Wants

Refineries rarely possess accurate historical data on previous cleaning/inspection activities, and what exists needs to be revised. In its twenty-year history, Tube Tech has never once found a refinery or petrochemical plant that could provide archives on how something has been cleaned, i.e., Pressures, volumes used, technology applied, or any other significant information that could hold the key to improving performance the next time around. Invariably, the comments from refinery personnel refer to "pressure jetting" or "chemical flushing" and very little else. A clear and precise information-gathering strategy is crucial to understanding the details of the problem, information such as limitations of access, deposit characteristics, etc., all of which help contractors apply the best technology most efficiently. This information reduces bottlenecking by preparing and understanding a cleaning problem before it occurs, planning for the best cleaning technology that benefits plant performance, reducing the cleaning time, increasing energy savings, and reducing the CO2 footprint.

Refinery engineers must accurately record cleaning activities, ROT HIT values, and heat transfer co-efficient data, i.e., New operational performance date and performance data before and after cleaning. This information is rarely if ever, shared with the contractor or the plant engineers, yet it is crucial to motivate contractors and plant personnel alike to deliver best practices. Within their lengthy contract questionnaire, Tube Tech International requests information about the units to be cleaned but also asks for detailed performance information. The comprehensive questionnaire aims to ensure that refinery operators can record the increase in performance that a TRUE conscientious specialist cleaning service will provide.

Arabian Texas Tower Clean Reduces Delta

The refinery of one of the world's largest Arabian oil companies includes a processing stage found in the most productive and successful refineries - the Continuous Catalytic Reforming unit or CCR Platformer. Texas towers or VCFEs (Vertical Combined Feed Exchangers) play a vital part in the platforming stage of the refinery process. Platforming product in its last stage of processing is passed into the Texas Tower to cool it down against cold feed. A VCFE is designed to minimize heat loss, thereby improving the fuel consumption of the unit's furnaces. The VCFE must operate as efficiently as possible, so the tube and shell sides need to be cleaned to the highest possible standard. For traditional high-pressure jetting contractors, this is a challenging task!

The two Texas Towers at this Arabian refinery contain a combined total of 6,200 steel tubes. The tubes are unusually long at 21 meters long, with an internal diameter of 14mm. Tube Tech was contracted to completely unblock and clean between 200 and 300 tubes in each VCFE. The client also stated that a 'good' production standard would be entirely satisfactory.

As the V.C.F.Es were opened, it became clear that the client had severely underestimated the level of fouling. Instead of 200-300 blocked tubes, there were almost 3,000, almost half the total. Thus, the contract risked becoming a classic bottleneck scenario. In the face of high local ambient temperatures, Tube Tech faced a significant challenge to meet the new objective in the time available, mainly as there were numerous operational delays beyond their control. An early, major obstacle was the lack of suitable scaffolding that was to have been provided by the client's sub-contractor.

As with any significant international cleaning project, 20 years of experience has taught Tube Tech to mobilize several cleaning solutions to a client's site to cover as many unforeseen operational eventualities as possible. This meant that the lack of scaffolding did not prevent the clean from going ahead, thanks to the companies' inherent forward thinking and ability to deploy a second and third fall-back system.

The heavy gum and coke blockages found in approximately 30% of the heat exchanger tubes required an unusual system modification as Tube Tech's bespoke and very unique 25m long vertical drilling rig intended for this type of blockage could not be deployed due to the absence of suitable scaffolding. With normal high-pressure jetting processes, any gum jetted out tends to solidify behind jetting nozzles and can trap the lance, making it irretrievable. In one of the VCFEs, Tube Tech found three tubes containing metallic blockages from previous contractors, including broken flexible and rigid lances, drills, and cleaning tips.

"Rarely do we encounter such a wide variety of tube deposits. We found literally everything - from coke-like substances to rubbery chewing gum-like full-length blockages," recalls Martin Byford, Tube Tech General Manager.

Incredibly, apart from the three blocked tubes, all the others were successfully unblocked and cleaned, and even more surprising, all within five days and nights. With intensive dedication and working in 40 degrees C heat, the Tube Tech teams could clean both VCFEs to inspection standards well over the production standard requested.

*Following the Tube Tech clean of the VCFEs, the heat transfer between the exchangers' tubes and shell increased dramatically, reducing the delta T between ROT and HIT. This is shown by the drop in temperature on the 'after' plot. The cleaning, therefore, led to hotter feed going to the downstream heater inlet, reported the client's Site Engineer.

Challenging Convention Reduces Time, Cost, and Emissions

Questioning conventional practices and long-standing beliefs is another way individual refineries can successfully debottleneck. The slavish use of standard cleaning methods means that many refineries find themselves replacing expensive equipment as the conventional cleaning techniques cannot provide the increase in performance required. Even when effective, many traditional cleaning methods often require that the equipment is removed to a cleaning bay for cleaning and, if not moved, then has to be offline while cleaned.

Fast Flare Line Clean Online

The specialist consultancy arm of one of the world's largest refinery companies approached Tube Tech to perform a "fast clean" operation from 10 days to 5 on a fouled refinery flare line in Germany, as a plant shutdown was imminent. Tube Tech visited the site, reviewed the task, and confirmed not only their ability to reduce the shutdown time by half but also felt strongly that the cleaning could even be completed while online, believing that 'just because no one had done it before did not mean it could not be done'.

The Germany-based facility of this global oil company refines crude oil and produces various hydrocarbon products, including ethylene, propylene, benzene, toluene, xylenes, and methanol. Combustible waste gases from all processes/plants are offloaded into a single flare line for burn-off.

Back pressure had been building up in the 250-meter refinery flare line as resistance to flow increased due to the line being restricted by approximately 40% overall by pyrophoric and sulfurous sludge deposition. The client's inspections suggested this soft, mud-like sludge badly restricted substantial sections of the pipeline. Taking the flare line off-line for cleaning meant that the entire refinery complex would have to shut down, the operational and cost implications of which would be substantial, as any refinery operator will know. The client hoped, therefore, to limit any such impact by cleaning during a plant shutdown. The risk of cleaning the flare during a shutdown with thousands of on-site workers would have had its own logistical problems.

Having surveyed the flare line, recorded the visit with digital images, isometrics, and inspection records. Tube Tech was the only contractor to suggest hi-tech, high-pressure jetting of the flare line while online. It would be a world first for Tube Tech and the oil industry if this could be achieved while addressing all safety issues. The flare line clean could then be removed from the shutdown and safely completed at the client's convenience.

Tube Tech offered to demonstrate their ideas on a full-scale mock-up of crucial sections of the flare line at its UK operations center. The client's consultants came to the UK and witnessed a successful online trial demonstrating multiple fail-safes. Tube Tech's bespoke method coped with potentially high temperatures and pressures inside the flare line and prevented oxygen spark ingress and the escape of toxic gases. The significant technical difficulty was to design access via 25mm valve ports located at intervals along the length of the flare line.

All systems devised for the project were trialed on the life-sized mock-up. Mechanical orbital cleaning heads and pulsed high-pressure hydro jetting lances, designed to be heat and scratch-resistant when fed into the small 25mm entry points, were utilized. Locating the deposits and establishing their level and density before cleaning was carried out by TracerCo, using gamma ray-based inspection during and after cleaning. Intrinsically safe inspection equipment was used by Tube Tech using a novel high-pressure/temperature sealing technology through the 25mm ports to take digital images before and after cleaning.

The objective was to reduce the deposition level within the flare line by removing as much sludge as possible, to level the remaining deposit, and to achieve an 80% cleanliness level to reduce back pressure. Even though some entry points turned out to be corroded shut or obstructed by weld intrusion, Tube Tech's "design-on-the-run" reputation came to bear, and equipment was modified to accommodate this unforeseen additional challenge.

With cleaning underway, some excellent reports came back from the inspectors, and in just five days, the cleaning standard had been achieved.

Based on the client's sample analysis, we came prepared for soft, mud-like deposition. Actual samples found during removal were concrete-like lumps, commonly known as "sulphurcrete" and not just sludge! We were, however, still able to wash loose concretion downstream to an interceptor tank. While our objective had been achieved, we offered to return with appropriate equipment and further guarantee removal of all the remaining sulfur concretion at some future date, reports Mike Watson, Technical and Managing Director, Tube Tech International Ltd. This was the first time an online flare line cleaning was accomplished. We have already developed an even more robust system to tackle future unexpected deposits and even longer and larger flare lines in case another similar opportunity presents itself anywhere in the world. A considerable digital video archive of information and knowledge was built up during the exercise, which means we can repeat the exercise at any time in the future.

By challenging convention, Tube Tech was able to avert a total refinery shutdown, thereby providing substantial financial savings for the refinery.

It Is About Working With the Right People

Successfully debottlenecking a refinery involves working with specialists. Refinery operators and engineers need to ask contractors the right questions, which will include:

• Have you experience in refinery debottlenecking?
• What inventive methods do you employ?
• Can you provide evidence of your experience?
• How will you approach our debottlenecking problem?
• Do you understand how this particular activity will affect the rest of our plant?
• Who will be on the team that comes to my plant?

Heat exchangers need to be cleaned out regularly. In practice, maintenance schemes for heat exchangers are based on legislation, meaning inspection and clean-out are required every two to four years. However, some heat exchangers should likely be cleaned more regularly because the savings achieved by thermal efficiencies and increased production capability will rapidly outweigh the extra costs of a cleaning exercise. Quite often, large amounts of time and money are spent on unnecessary inspections of heat exchangers brought about by doubt caused by heavily scaled tubes that could harbor under-scale corrosion. Tube scale is often so hard that no inspection tool can provide a suitable reading or even be pushed down a tube.: Solution? Clean it with the right technology at the right time. A cost-effective clean-out strategy is needed for heat exchangers in a train.

Forming a debottlenecking plan for cleaning activities can pay dividends, for example, Separating and prioritizing exchangers that are:

1. Critical path.
2. Difficult to clean.
3. Those that never seem to be cleaned effectively in the time allowed.
4. Those that are removed to a cleaning bay.

Finding the best practice solution for each selection should make debottlenecking cleaning activities run more smoothly instead of simply using the same tool for all.

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