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Innospec Fuel Specialties technical bulletin: Considerations when heating VLSFO and Case Studies

Heating VLSFOs to prevent cold flow issues causes issues related to distillate ageing, and there is a gentle balance to be maintained when handling the product.




Considerations when heating VLSFO and Case Studies

Colorado-based global specialty chemicals company Innospec Fuel Specialties in December published a technical bulletin entitled Cold Flow – A Point on Pour Point. The document has been shared with Singapore bunkering publication Manifold Times:

Considerations when heating VLSFO

Heating VLSFO to prevent cold flow issues will cause unintentional issues related to distillate ageing i.e. the rapid change in fuel quality due to chemical reactions in the lighter fractions of the fuel.

A study into the storage stability of VLSFO from global ports shows how the sediment present in VLSFO increases over time when a fuel is stored at slightly elevated temperatures (50°C).  The Total Sediment Existent (TSE) increases with time across most fuels, and rapidly increases in most cases to exceed the ISO 8217 limits within weeks.

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The increased sedimentation would manifest as excessive sludge, filter blocking and centrifugal purifier maintenance. However, these are only symptoms of ageing and other issues besides might be expected, such as reduced fuel efficiency, poor combustion and contamination of future bunkers.

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There is clearly a gentle balance to be maintained when handling VLSFO that did not previously exist when using HSFO. If temperatures are too low there is the risk of cold flow issues, poor separation efficiently etc. Too high and fuel will age, leading to excess sludge and deposits. Diligent monitoring and housekeeping practices are one of the best ways to combat this, ensuring that storage temperatures are maintained high enough to prevent wax but not so high that the ageing process is unduly accelerated.

At this time there is little information on how low is too low, or how high is too high. Chemical treatments are available that retard the chemical ageing process and mitigate against the consequences of aged fuel.

Case Story 1: Wax sludge experienced in cold climate

4 Layers in storage
Example of solid wax deposits on tank bottoms

Bunker Grade, Quantity: VLSFO IFO380, 2000MT
ISO 8217: Met
Viscosity, Pour Point: 28cSt, 6°C
WAT, WDT: Not tested

Issue: Sludge clogging backwash filters and overloading purifier. Heavy sludge left behind at bottom of bunker tank unable to be dissolved.

It was during the winter season and the container ship was transiting through a cold climate region. There was no issue faced when the first 200MT of fuel was consumed but soon after, the vessel started to experience sludge issues. Some fluctuation was also observed at the viscometer.

Why did this happen? Where heating is insufficient, especially when the vessel transits through cold climates, the fuel can separate into layers. Initially, lighter components will enter the fuel system and leaves behind the heavier components. Even with the highest possible temperature that can be achieved in bunker tanks, the sludge that remains at the bottom of the tank will not dissolve.

Case Story 2: Wax sludge experienced with on spec pour point fuel, WAT/WDT unknown


Port: South Korea
Bunker Grade, Quantity: VLSFO IFO380, 400MT
ISO 8217: Met
Viscosity, Pour Point: 33cSt, 15°C
WAT, WDT: Not tested
Issue: High generation of sludge overloading the purifier.

In this case, the sludge appeared to have both the consistency of waxes and asphaltene sludge. Hence, to eliminate the possibilities, the vessel carried out a trial and error at the purifier by increasing the separation temperature in steps of 5 °C from the recommended separation temperature which was 60 °C. When the separation temperature was maintained at 75 °C, the sludge generated was observed to be minimal and therefore, the sludge is likely waxes.

Sometimes, purifying at the recommended temperature is insufficient when the fuel has a higher risk of experiencing cold flow issues. At any point of time, if the temperature falls below WAT, wax crystals will form and they can only be dissolved by increasing the heating temperature to above WDT.

However, excessive heating either by high temperature or long-term heating can accelerate the distillate ageing process. Hence, correct heating must be applied.

Case Story 3: Wax sludge experienced with low pour point fuel, high WAT/WDT

Waxy fuel blocking centrifugal purifier drains

Port: Singapore
Bunker Grade, Quantity: VLSFO IFO380, 800MT
ISO 8217: Met
Viscosity, Pour Point: 57cSt, 3°C
WAT, WDT: 74 °C, >75 °C
Issue: High generation of sludge overloading the purifier

The vessel suspected waxes due to the softer appearance of sludge that was clogging the purifier and hence, requested for the fuel lab to carry out WAT, WDT testing with the fuel. From the results, it is likely that waxes have formed in the bunker tank as the fuel’s temperature at storage fell below its’ WAT result. In an attempt to dissolve the waxes before consuming the fuel, the vessel increased the storage temperature to as close to WDT as possible, managing to achieve only 50 °C inside the bunker tanks. The sludge issue did improve for the next 48hrs before it took a turn and worsened.

Why did this happen? This is an example where issues and solutions overlap. In this case, the temperatures required to dissolve the waxes (WDT) were extremely high which brought a new problem into the equation- an irreversible distillate ageing process through thermal instability. In addition, distillate sludge can similarly clog filters and purifiers.

The fuel’s resistance to oxidation and thermal instability can be improved significantly with the help of fuel additives. However, if the distillate ageing process has already started then it cannot be reversed. Its’ effectiveness will only be to stabilise the fuel and the chances is dependent on the extent the fuel has aged. Hence, pre-combustion additives are always recommended to be dosed at an early stage- into the storage tanks before bunkering.

Please contact your local sales representative for more information. Email:

For Technical support or questions please email:

Find out more about Innospec Fuel Specialties’ series of OctamarTM products here.

Photo credit: Innospec Fuel Specialties
Published: 12 January, 2022

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Sea Cargo Charter report demonstrates shipping’s shortfall against IMO climate goals

2024 report highlights the gap between current emissions and the IMO’s revised strategy for net-zero emissions by 2050.





Sea Cargo Charter 2024 report

The shipping industry must take urgent action to meet ambitious new climate targets set by the International Maritime Organization (IMO), according to a new report released on Thursday (13 June) from the Sea Cargo Charter (SCC), a global transparency initiative developed by the Global Maritime Forum.

New data from the SCC, a global framework representing 20% of global bulk cargo transport, reveals the sector fell short of minimum international climate goals set by the IMO by an average of 17% in 2023, equivalent to 165 million metric tonnes of CO2e.

When considering ‘striving’ goals set by the IMO, signatories are on average 22% misaligned, which represents a shortfall of 204 million metric tonnes of CO2e in 2023.

Currently, dry bulk, general cargo, and tankers account for around 400 million tonnes of CO2 emissions. With global trade predicted to quadruple by 2050, emissions will skyrocket without urgent action.

Reporting has also been expanded to include “well-to-wake” emissions, which measure emissions from the extraction of oil to its end use, providing a more comprehensive picture of environmental impact and pushing the industry towards faster decarbonisation.

The 2024 report highlights the gap between current emissions and the IMO’s revised strategy for net-zero emissions by 2050. The report shows the importance of commercial and operational decisions on the vessels’ use (such as, instructed speed, cargo and routing optimisation, laden/ballast ratio), innovation and cooperation within the industry to be able to take action in this transition.

Other identified barriers to cutting emissions are geopolitical disruptions, limited alternative marine fuel options for long voyages, and a lack of infrastructure to support new technologies.

The 2024 Annual Disclosure Report was produced by the Global Maritime Forum, which performs secretariat services for the Sea Cargo Charter with expert support provided by UMAS and the Smart Freight Centre.


Photo credit: Sea Cargo Charter
Published: 14 June 2024

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Expert discusses technical considerations of using ammonia as marine fuel

Ammonia as bunker fuel poses significant safety challenges due to its toxicity and flammability, says ABS Regional Business Development Manager Muammer Akturk.





Technical considerations of ammonia as marine fuel

Muammer Akturk, ABS Regional Business Development Manager, on Monday (10 June) published an article on technical considerations of using ammonia as a marine fuel in his Alternative Marine Fuels Newsletter.

The article dives into the use of ammonia as a marine fuel, focusing on the safety and technical considerations necessary for its implementation.

Ammonia is recognised for its potential as a zero-carbon fuel, making it an attractive option for reducing greenhouse gas emissions in the shipping industry. However, it poses significant safety challenges due to its toxicity and flammability.

Key points discussed include:

  1. Safety Measures: The importance of stringent design and operational safety measures to prevent ammonia releases and mitigate risks during both normal and emergency conditions is emphasized. This includes the need for gas dispersion analyses and the use of safety systems like gas detectors and alarms
  2. Regulatory Framework: The article reviews the latest regulations and guidelines developed to ensure the safe use of ammonia as a marine fuel. This includes the IACS Unified Requirement H1, which provides a framework for controlling ammonia releases on vessels
  3. Engineering Considerations: Technical aspects such as fuel storage, handling systems, and the role of risk assessments in identifying potential hazards and implementing preventive measures are detailed
  4. Human Factors: The article also considers the human factors approach to safety, emphasizing training and the importance of designing systems that account for human errorOverall, the article aims to provide a comprehensive overview of the challenges and solutions associated with using ammonia as a marine fuel, highlighting the importance of safety and regulatory compliance in its adoption.

Editor’s note: The full article can be found at the link here.


Published: 13 June 2024

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JLC China Bunker Market Monthly Report (March 2024)

China’s bonded bunker fuel sales grew in March, as the shipping industry recovered gradually and sellers actively boosted sales on the back of ample supply and high inventories.





JLC Bonded bunker fuel sales in Zhoushan (Mar 2024)

Beijing-based commodity market information provider JLC Network Technology Co. recently shared its JLC China Bunker monthly report for March 2024 with Manifold Times through an exclusive arrangement:

Bunker Fuel Demand

China’s bonded bunker fuel sales surge in March

China’s bonded bunker fuel sales grew in March, as the shipping industry recovered gradually and sellers actively boosted sales on the back of ample supply and high inventories. Domestic LSFO prices were lower than those in Singapore and other neighboring ports, incentivizing shipowners or operators to refuel their vessels in China, with bunkering volume in Shanghai and Zhoushan rising considerably.

The country sold about 1.82 million mt of bonded bunker fuel in the month, with the daily sales up 13.59% month on month to 58,658 mt, JLC’s data shows.

Sales by Chimbusco, Sinopec (Zhoushan) and China ChangJiang Bunker (Sinopec) came in at 540,000 mt, 630,000 mt and 30,000 mt in March, while those by suppliers with regional bunkering licenses settled at 558,400 mt. At the same time, SinoBunker sold about 60,000 mt of bonded bunker fuel, the data indicates.

China’s bonded bunker fuel exports rise in first two months

China’s bonded bunker fuel exports rose in the first two months of this year, underpinned by fresh quotas and larger production.

The country exported a combination of 3.02 million mt of bonded bunker fuel in January-February, growing by 3.13% from the same months in 2023, JLC estimated, with reference to data from the General Administration of Customs of the PRC (GACC).

Heavy bunker fuel exports totaled about 2.85 million mt in the two months, accounting for 94.13% of the total, while light bunker fuel exports were 177,500 mt, accounting for 5.87%.

The increase in the exports mainly came as China released this year’s first batch of quotas on LSFO exports at the end of 2023. Though refiners’ LSFO production margins were relatively poor, they ramped up their production amid new quotas, which buoyed the exports. China’s LSFO output totaled 2.57 million mt in January-February, with the daily output gaining 2.69% year on year to 42,850 mt, JLC’s data shows.

In January alone, China’s bonded bunker fuel exports settled at 1.78 million mt, jumping by 11.93% month on month and 34.71% year on year.

However, the exports plunged to 1.25 million mt in February, down by 29.99% month on month and 22.75% year on year. Bunkering business at Chinese ports was halted during the Chinese New Year holiday, and customs’ clearing procedure for export was also affected by the holiday. In addition, the operation of many ports was hit hard by heavy snow and freezing rains, adding to the downward pressure on the exports.


JLC China bunker exports by region 2023 2024


JLC China major blending producers' bunker supply (Mar 2024)

Domestic-trade bunker fuel demand rises in March

Domestic-trade heavy bunker fuel demand recovered mildly in March, as the shipping industry rebounded after the Chinese New Year holiday. However, the demand growth was still limited as some shipowners still suspended services and the market was dominated by wait-and-see sentiment amid high prices.

Domestic-trade heavy bunker fuel demand was estimated at 430,000 mt in the month, a gain of 70,000 mt or 19.44% from a month earlier, JLC’s data shows.

Meanwhile, domestic-trade light bunker fuel demand was estimated at about 140,000 mt, a gain of 20,000 mt or 16.67% from a month earlier, the data indicates.

Bunker Fuel Supply

China’s bonded bunker fuel imports soar in Jan-Feb

China’s bonded bunker fuel imports soared in January-February 2024, due to a low base a year earlier.

The country recorded 581,900 mt of bonded bunker fuel imports in the two months, a surge of 27.36% year on year, with 359,200 mt in January and 222,700 mt in February, JLC estimated, with reference to data from the GACC.

China’s bonded bunker fuel imports dived to a record low in January-February 2023, as bunkering demand had not fully recovered from the epidemic, also because of high freight rates and ample domestic supply. The imports totaled only 456,900 mt in the first two months of 2023, tumbling by 48.01% year on year.

On the other hand, Chinese refiners boosted LSFO production in January-February 2024, limiting the import growth. These refiners produced about 2.57 million mt of LSFO in the two months, with the daily output climbing by 2.69% year on year to 42,850 mt, JLC’s data shows.

Russia became the largest bonded bunker fuel supplier in the first two months of this year, exporting 276,800 mt to China, accounting for 47.57% of the latter’s total imports. Malaysia ranked second with 186,800 mt, accounting for 32.10%, followed by South Korea with 95,800 mt, accounting for 16.46%. Japan climbed to the fourth place with 21,500 mt, occupying 3.69%, while Singapore slipped to the fifth place with only 1,000 mt, making up 0.17%.

In China’s bonded bunker fuel market, only HSFO and MGO are still mainly imported, while LSFO is rarely imported as its import efficiency is relatively low amid steep freight rates.

JLC Bonded bunker fuel imports by source Jan Feb 2024

Domestic-trade bunker fuel supply increases in March

Domestic-trade heavy bunker fuel supply improved in March, as availability of some blendstocks (such as low-sulfur residual oil and shale oil) increased.

Chinese blenders supplied about 460,000 mt of domestic-trade heavy bunker fuel in the month, a rise of 60,000 mt or 15% from February, JLC’s data shows.

Similarly, domestic-trade MGO supply rose to 160,000 mt in March, up 30,000 mt or 23.08% month on month, the data shows. Refineries’ enthusiasm for MGO production improved in March, as domestic MGO prices moved up along with domestic oil products.

JLC Arrival of imported fuel oil cargoes


JLC China main oil blending feedstock prices

JLC China domestic trading 180 cSt bunker fuel price 2023 2024

JLC China bunker blending profit by region 2023 2024

Yvette Luo
[email protected]

Sales (Beijing)
Tony Tang
[email protected]

Sales (Singapore)
Ginny Teo
[email protected]
[email protected]

JLC Network Technology Co., Ltd is recognized as the leading information provider in China. We specialized in providing the transparent, high-value, authoritative market intelligence and professional analysis in commodity market. Our expertise covers oil, gas, coal, chemical, plastic, rubber, fertilizer and metal industry, etc.

JLC China Bunker Fuel Market Monthly Report is published by JLC Network Technology Co., Ltd every month on China bunker market, demand, supply, margin, freight index, forecast and so on. The report provides full-scale & concise insight into China bunker oil market.

All rights reserved. No portion of this publication may be photocopied, reproduced, retransmitted, put into a computer system or otherwise redistributed without prior authorization from JLC.

Related: JLC China Bunker Fuel Market Monthly Report (February 2024)
RelatedJLC China Bunker Market Monthly Report (January 2024)

Note: China-based commodity market information provider JLC Technology has been providing Singapore bunkering publication Manifold Times China bunker volume data since 2020. Data from earlier periods are available here.


Photo credit: JLC Network Technology
Published: 11 April 2024

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