Filterability diesel fuel

Table 5.1 Diesel fuel filter operating factors...

In the selection of diesel fuel filters, it is important to verify that they have been tested in accordance with the appropriate ISO test standard, which measures the effectiveness of fuel filters. 

Figure 5.4 Diesel fuel filter-water separator...

The characteristics of diesel fuel taken into account in this area are the cloud point, the pour point, and the cold filter plugging point (CFPP). 

The cold filter plugging point (CFPP) is the minimum temperature at which a given volume of diesel fuel passes through a well defined filter in a limited time interval (NF M 07-042 and EN 116 standards). For conventional diesel fuels in winter, the CFPP is usually between —15 and —25°C. 

The experimental conditions used to determine the CFPP do not exactly reflect those observed in vehicles the differences are due to the spaces in the filter mesh which are much larger in the laboratory filter, the back-pressure and the cooling rate. Also, research is continuing on procedures that are more representative of the actual behavior of diesel fuel in a vehicle and which correlate better with the temperature said to be operability , the threshold value for the Incident. In 1993, the CEN looked at two new methods, one called SFPP proposed by Exxon Chemicals (David et al., 1993), the other called AGELFI and recommended by Agip, Elf and Fina (Hamon et al., 1993). 

The main justification for diesel fuel desulfurization is related to particulate emissions which are subject to very strict rules. Part of the sulfur is transformed first into SO3, then into hydrated sulfuric acid on the filter designed to collect the particulates. Figure 5.21 gives an estimate of the variation of the particulate weights as a function of sulfur content of diesel fuel for heavy vehicles. The effect is greater when the test cycle contains more high temperature operating phases which favor the transformation of SO2 to SO3. This is particularly noticeable in the standard cycle used in Europe (ECE R49). 

The nature of these paraffins and their concentration in diesel fuel affect the three temperatures that characterize the cold behavior. The cloud point is the temperature at which crystals of paraffins appear when the temperature is lowered. The cold filter pluming point is defined as the temperature under which a suspension no ionger flows through a standard filter. Finally, the pour point is the temperature below which the diesel fuel no longer flows by simple gravity in a standard tube. These three temperatures are defined by regulations and the refiner has three types of additives to improve the quality of the diesel fuel of winter. 

This condition is of concern only when equipment operates in subzero ambient temperatures. Since diesel fuel extracted from crude oil contains a quantity of paraffin wax, at some low ambient temperatures this paraffin will precipitate and create wax crystals in the fuel. This can result in plugging of the fuel filters, resulting in a hard or no-start condition. Any moisture in the fuel can also form ice ciystals. Cloud point temperatures for various grades of diesel and other fuels should be at least 12°C (21.6°F) below the ambient temperature. In cases where cloud point becomes a problem, a fuel water separator and a heater are employed. 

All diesel fuels tend to contain trace water, expressed in parts per million (ppm). With the veiy high fuel injection pressures now used in electronically controlled diesel engine, fuel-filter/water separators are widely used, since water allowed to circulate freely through the injection system can result in seizure of components and erosion of injector orifice holes, and in extreme cases the high compressibility factor of water can blow the tip off of the fuel injector. 

Analysis of nitroaromatics found by treating diesel fuel with NO2 (column A) compared to nitroaromatics found in extracts of filters of exhaust from a diesel engine (column B) or in extracts of diesel soot deposited in a dilution tunnel of an animal exposure system (13). 

DCL DDGS DEFC DICI DISI DME DMFC DOE DP DPF Direct coal liquefaction Distillers dried grains with solubles Direct ethanol fuel cell Direct-injection compression ignition Direct-injection spark ignition Dimethylether Direct methanol fuel cell Department of Energy (USA) Dynamic programming Diesel particulate filter... 

Fuels such as diesel fuel and heating oil are sometimes stored in large tanks for extended periods of time. At temperatures below the cloud point of the fuel, wax can form and fall from solution. Accumulated wax within fuel systems can deposit onto component parts and settle into areas of low turbulence. Problems such as filter plugging and flow limitations can be due to accumulated wax. 

Diesel fuel pumped from storage tanks, through pipelines, and within internal combustion engines passes through various types of fuel filters. When cold fuel containing wax passes through these filters, the wax can be trapped on the filter media. Accumulated wax can slow the flow of fuel enough to shut down further fuel flow. 

Diesel fuel and kerosene alone are not effective solvents for use in solubilizing most WCMs for low-temperature application. The low KB value of diesel fuel and kerosene makes these fuels ineffective at holding the WCM in solution for extended periods of time at low temperatures. Stratification and separation of the WCM from solution can lead to application problems such as filter plugging and inaccurate WCM treatment. 

Additional low-temperature fuel filterability information is often required to confirm whether fuel will pass through fuel filters in cold environments. Two tests are commonly used to determine this performance value, ASTM D-4539 and IP 309. The method ASTM D-4539 is termed the Low-Temperature How Test (LIFT) and is used to determine the low-temperature filterability of diesel fuel. 

The CFPP was developed in 1965-66 to predict the low-temperature filterability performance of diesel fuels. This method is commonly used throughout the world to quickly determine low-temperature fuel filterability characteristics. In more recent... 

PROBLEM DIFFICULTY IN PUMPING DIESEL FUEL AT LOW TEMPERATURES / FUEL FILTER PLUGGING... 

Water contamination in diesel fuel is common. When diesel fuel cools, ice crystals may form in the fuel well before the fuel reaches its pour point. These ice crystals will settle to the bottom of fuel tanks and may result in fuel filter plugging and pumpability problems. 

The high content of water and emulsifier in this fuel creates some differences in handling and application compared to conventional diesel fuel. The surfactant quality of the emulsification additive in the fuel can remove existing deposits from the internal surfaces of fuel handling and storage systems. Problems with fuel discoloration and fuel filter plugging may follow. Compared with conventional diesel, fuel economy ratings per tank of fuel will drop because the overall carbon content per unit volume of fuel is lower. This is due to carbon displacement by water. 

At present, there is no indication that the filters used in diesel fuel dispensers now are not compatible with biodiesel. 

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