World Bunkering >Articles > Fuel management > Getting the most out of bunker fuel

The use of advanced control in-line blending technology in the bunkering industry holds the key to achieving an optimally profitable fuel oil supply operation, especially with the current MFO and MDO/MGO price differential, and MARPOL maintaining pressure for the market to ensure and validate fuel quality and quantity. By streamlining operations to ensure flexible delivery of high quality and certified products, forward-thinking suppliers can gain a commercial advantage and capture a dominant role in future bunkering markets. They will be able to more quickly deliver a comprehensive range of products using a wider variety of feedstock than their competitors. Their bunkers will be of a guaranteed quality, fully complying with the regulations and produced at the highest margin. Furthermore, their infrastructure will be optimally structured to meet future market demands.
Three primary parameters controlling blend accuracy to optimise bunker quality are: measurement representivity and repeatability, normally of viscosity, density and now sulphur; programmed corrective responses to changing process conditions; and correct field integration of all system components. While in-line blending has been around for some time, traditional systems failed to deliver their promise because they did not accurately measure or control either the volume or the quality of the bunkers at reference conditions and therefore could not produce an accurate blend.
Newer systems have produced a quantum leap in the application of in-line technology for bunker blending. They have proven to flexibly deliver products on specification at the lowest cost, significantly reducing operating costs while giving an auditable guarantee of quality. Enhanced blending plus developments in mixing, analysis and instrumentation integration have delivered the promise. A helpful example of these developments is found in comparing the quality and cost factors of traditional viscosity systems with the newer advanced systems. Traditional viscosity measurement and control only delivers an accuracy of ±1% of the viscometer’s calibrated range. In bunkering, a viscometer measuring 60-500 cSt at 50°C is likely to have a calibrated range of approximately 1000cSt, and 1% of this is 10cSt. The ISO bunker specification calls for viscosity of +0-10%. Based on this “offset specification”, a ±10cSt viscometer accuracy error causes an error of up to 20cSt in a compliant blend (as shown below).

When blending 180cSt this results in a viscosity of 160cSt with significant “give-away” of MDO/cutter. An advanced viscosity measurement and control system uses a controlled and stabilised mixing and temperature environment to guarantee a viscosity measurement and control accuracy of ±1% of the actual (target) viscosity. This reduces the potential error from 20cSt to 3.6cSt (±1.8cSt). When blending 180cSt this delivers a saving of in excess of $5 a tonne, by blending a 176.4cSt (instead of 160cSt), reducing the MGO/MDO usage in the blend by nearly 2%. Fuel certification can be provided by the blender control system. Viscosity is the only parameter of interest for a Bunker Delivery Note (BDN) that cannot be accurately calculated (provided feedstock is compatible) based on the ratio of the feedstock, and this is a key measurement and control parameter for an advanced control blender. Each feedstock BDN/certificate is used in real-time by the blender to both calculate and/or limit key parameters, such as sulphur, to ensure the quality of the blended product. This data is used by the blender control system to produce a BDN for the batch once complete. The batch quality is certified using a flow-proportional representative sample. While a manual spot sample will provide verification of a point in the transfer, an automatic flow proportional sample is the only way to guarantee a truly representative sample to validate the batch quality and blending process.

An in-line blender – upping quality and profitability

With the increasing availability of higher sulphur base stocks, there is an increase in the number of operators investing in multistream blending for bunker applications. This enables them to use compatible high and low-sulphur heavy base stocks along with viscosity and density cutters to optimise both the quality and production costs for the fuel. To summarise, it is clear that the poor performance of old traditional in-line blenders is a thing of the past, and that new levels of bunkering efficiency, competiveness and profitability can be achieved by working with today’s blending system manufacturers to understand the real value and return on investment that an advanced control in-line blender can deliver.