Whitepaper Renewable Diesel in Combustion Engines Diesel Performance Additive Team - Americas
AOverviewnewfuelsourceisbeingusedmore and more in the diesel fuel market. Afton has been approached with questions surrounding renewable diesel fuel. If you would like more information about renewable diesel, please read below. Afton Chemical is committed to providing our customers with leading technologies to improve fuel economy, reduce emissions, and extend the life of engines and equipment in all market fuels.
Ultra-Low Sulfur Diesel vs. Renewable Diesel vs. Biodiesel. What is the difference?
Figure 1: Overview of biofuel and petroleum diesel production
ULSD is traditional pertroleum based diesel fuel composed of a complex mixture of hydrocarbons and other organic material derived from crude oil. Biodiesel and renewable diesel (or Hydrotreated Vegetable Oil) are not derived from crude oil. They are made from non-petroleum biomass or biomass-derived renewable feedstocks. Traditional biodiesel is produced by a process called transesterification, yielding fatty acid methyl esters (FAME) and glycerol. Renewable diesel is produced by a hydrotreatment process that yields pure middle distillate hydrocarbons in the diesel range, and other bio-derived fuel sources like renewable propane. As shown in Figure 1, renewable diesel has a similar composition to petroleum diesel, making it suitable for use in diesel engines. Depending on the source, renewable diesel blend properties can vary and may require lubricity additives, cold flow improvers, pour point depressants, corrosion inhibitors and other additives to improve overall fuel characteristics.
Both1.
Illustration of above ground diesel storage tank
ULSD and Renewable Diesel can experience issues with fuel contamination and degradation.
Fuel, regardless of the source, can be subject to impurities such as contaminants or fuel-degradation products. As specified in ASTM D975, fuel contaminants are materials not intended to be present in fuel and can make the fuel less suitable for use. Fuel-degradation products are materials that are formed in fuel from exposure to oxygen and relatively high temperatures. Both types of impurities can be introduced during the manufacturing, handling, distribution, or storage process. For example, water is one of the top contamination concerns for diesel fuel, and it can enter fuel through transportation, tank leaks, and condensation. The presence of water in diesel fuel can lead to increased microbial activity, metal wear, and filter plugging. It is expected that similar issues found with conventional diesel fuel could impact renewable diesel as Figurewell.2:
In an engine, combustion is not 100% complete, and the process can result in carbon depos its and soot. It is important to continue to prevent external injector deposits (coking or fouling around the flow holes in the injector tips) and internal injector deposits. The build-up of these deposits can have detrimental effects on fuel economy, emissions, and uptime. While 100% renewable diesel is described to be free of contaminants when it exits the refinery, like ULSD, it is not immune to contamination by impurities that can be introduced during the transporta tion process, storage, or in the engine itself. Industry requirements are estabilshed to ensure overall fuel quality, and to protect engine parts and equipment. One of the industry standards, the CEC F-98-08 (DW10B) test, is used to assess diesel deposit control additives for their cleanliness performance in modern high pressure common rail injectors. The DW10B is a keep clean test that utlizes zinc neodecanoate, an organometallic fuel contaminant, to accelerate engine power loss in a reference fuel. The power loss is a result of external injector deposit formation. When tested with the zinc accelerant and without a deposit control additive, renewable diesel will form deposits in this test similar to ULSD. Afton’s deposit control additives have proven effective in preventing deposit accumulation even in the event of metal contamination.
diesel Renewable diesel is recognized as an ASTM D975 compliant fuel, meaning that it is suitable for use in compression ignition engines. Fuels compliant with ASTM D975 are still susceptible to injector deposits and fuel degradation products/contamination.
Control Additives and their role in renewable
Deposit2.
A second industry standard test, CEC F-23-A-01(XUD-9 indirect injection), is also used to evaluate the formation of external coking deposits on diesel injectors. Graph 1 presents results for 100% ULSD, 100% RD, and a blend of the two. Results show that renewable diesel does in fact generate injector-fouling deposits during this 8-hour test. Using a deposit control additive in these fuels will reduce this fouling.
Graph 1: XUD-9 injector fouling demonstration in EN590, 30% HVO, and 100% HVO
Afton has conducted testing with varying renewable diesel blends that show they behave like conventional diesel in their deposit-forming tendency and responsiveness to additives.
Graph 2 shows the results from real-world coking vehicle tests where a 30% renewable diesel blend without dopants showed a 3% power loss after 6000 miles compared to the start of test. The additized run, following that dirty up phase, recovered 100% of the 3% power loss. The strong performance of Afton additives in these industry and real-world tests leads us to rec ommend the use of deposit control additives to control internal and external injector deposits and maintain optimum vehicle performance when using renewable diesel fuel.
Modern high pressure common rail injectors can also suffer from internal injector deposits. These deposits can be sticky and cause sluggish injector response, which affects performance and emissions. The potential for internal deposit formation is still a concern for 100% renewable diesel, as illustrated in recent papers such as SAE 2019-01- 0061, where injector blockage was observed with 100% renewable diesel. Blends that contain renewable diesel will also need deposit control additives.
Graph 2: Real-world power performance demonstration in 30% HVO
Table 1: Corrosion and lubricity performance demonstrated in renewable diesel Afton4. additives are safe for use in renewable diesel and renew diesel blends
Additional3. additive solutions may be required to meet specs
Renewable diesel may require other additives in addition to deposit control additives such as lubricity improvers and corrosion inhibitors to meet specification or enhance the level of desired performance. Additionally, the highly paraffinic nature of renewable diesel may cause low temperature filterability issues requiring the use of cold flow improvers or pour point depressant additives. Afton supplies several additive solutions to fulfill any customer’s performance and handling needs.
Extensive compatibility and performance testing has been conducted with Afton’s diesel additive technologies in renewable diesel blends. In testing to date, deposit control additive technologies have been shown to improve the overall performance of the fuel, providing protection in critical areas such as filter blocking and the prevention of injector deposit build-up.
Summary Renewable diesel can create engine and injector deposits leading to the need for deposit control Renewableadditives.diesel can be susceptible to contamination and degradation similar to ULSD. Renewable diesel may need lubricity improvers, corrosion inhibitors, cold flow and pour point depression additives to achieve desired fuel performance. Afton Chemical is committed to providing our customers leading technologies to improve fuel economy, reduce emissions, and extend the life of engines and equipment in all market fuels. Afton’s patented Greenclean™ detergent technology has proven to be effective in cleaning up deposits and reducing the harsh effects of impurities. For more information, please contact your local Afton representative or visit www.aftonchemical.com
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