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Inexpensive purification of diesel fuel

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Purification of diesel fuel is a rather important issue today, since poor quality diesel fuel may cause the whole fuel system to fail. Obviously, the desired effect should be produced with the minimum of financial resources. The following is a review of inexpensive diesel fuel purification methods.

Quality of diesel fuel should be observed regularly, and the fuel should be purified in time by removing small solid particles. This allows to prevent potential problems for the fuel system.

In general case, diesel fuel can be purified by physical methods and a combination of physical and chemical processes.

A mesh filter is a partial solution. It can capture particles larger than 80 micron. If the particles are smaller, they can pass through the filter unobstructed, and will still cause contamination of the fuel.

Filtration is an important physical method, because it allows to remove dust, which can enter the fuel tank at the filling station. Presence of dust in the fuel causes insufficient supply to the combustion chamber and reduces engine power. Simple filters are made in the form of a case containing a filtering element. More complex filters can capture water, which allows to improve diesel fuel performance.

However, such filters require increased attention, since they cannot let fuel through when they are saturated with water. Unpurified fuel passes around the barrier, which may cause failure of the fuel system and the engine.

Separation is different from filtration in terms of increased reliability. If the fuel is heavily contaminated, regular filters cannot entirely purify it. In this case separators are used. These systems can remove contaminants from the fuel, and the quality of purification does not depend on the amount of the undesired substances. Much like filters, separators can remove both solid particles and water from the fuel, but the design of such systems is much more complex.

The principle of operation divides separators into chemical and physical systems. They separate water and contaminants and remove them to the bottom of a purifier. To maintain operability of the separators, the bottom must be cleaned of the sediment from time to time.

While choosing the purification method, it should be noted that the purity of the processed diesel fuel may not always comply with the sensitivity of the fuel system.

In this case, proven and efficient equipment is in order. One such plant is GlobeCore’s UVR-450/6. This system removes hydrogen sulfide and unsaturated hydrocarbons, reduces the content of paraffin and sulfur. During processing, the fuel is lightened and stays light. The UVR-450/6 plant is reliable and simple to operate. Beside diesel fuel, it can process heavy fuel oil, gas condensate, and regenerate transformer, turbine and industrial oil.

Additive Blending

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Fuel additive is substance which is added to fuel (to gasoline, kerosene, diesel and so on) for improvement of their properties. Depending on the quality of initial fuel, function, property and efficiency of additives, their combinations in a commodity product are various. The additive content in fuel varies from 2 to 20% depends from the weight. Modern motor fuels made from basic fuel with additive blending process. For gasoline, first of all, additive should increase octane number, and for diesel fuels it will increase cetane number for improvement of flash temperature in the closed crucible and freezing temperatures.

Modern gasoline is very difficult by its hydrocarbonic structure and presence of additives which have various functional properties. Quality of common gasolines is defined by about twenty indicators which fix in the quality passport on each portion of gasoline. Such quality indicators as the induction period or water-soluble acids are most often known only between experts. But octane number of gasoline, well known practically every person. Octane number is so important value that is mentioned in each brand of gasoline. This value characterizes the most important operational property of gasoline – its detonation firmness. One of the most economic ways for increasing of detonation firmness of gasoline is application of the anti-detonation additive. At the concentration in gasoline of the 100-th shares of percent, it is increasing its octane number by 8 or more units. Production of gasoline without uses of anti-detonation additives is 5-7 times more expensive in comparison with production in which such additives are applied.

Additives which are intended in procedure of increasing diesel fuel cetane number, lead to decrease in time of a delay of ignition, increase uniformity and completeness of diesel fuel combustion, soften rigidity of diesel engine operation and facilitate its start process, improve ecological characteristics and decrease fuel consumption.

GlobeCore Blending Company started manufacturing additive blending systems for additive blending in hydrodynamic knot of mixing with additives injection by knots, depending on consumption of a basic component. Depending on requirements of the final product, exist from 2 to 7 additional knots for additives injection in the hydrodynamic mixer. The USB additive blending systems have been delivered worldwide for the period of past ten years. Today there are more than 53 countries, hundreds objects where our installations were supplied. GlobeCore Blending systems can work in any climatic zones, under climatic conditions from -65 C° to +55 C° as independently or in work chain.

additive blending

Removal of hydrogen sulfide from syngas

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The human population on Earth is growing rapidly. Current projections maintain that by 2050 there will be 9 billion humans, and 10 billion humans by 2100. The rapid growth leads to rapid reduction of areas for landfills. A good solution is to recycle waste into alternative fuels. The product of waste recycling is syngas. It can be used in generation of electricity, as well as raw material in many chemical and petrochemical processes. However, syngas contains hydrogen sulfide, which is a toxic and corrosive sulfur compound, and must be removed from syngas for environmental and safety reasons.

One method of HS removal is used in Japan, in waste recycling facilities. Japan is a good example, since it is there where waste recycling is especially efficient.

The Claus process is used for removal of sulfur from crude syngas in large refineries. This method is currently standard for such tasks. It is not, by far, the most efficient process, however. This is due to high costs and complications when operating relatively small plants.

Liquid redox process was first used in gasification in Japan in 2001. The method proved successful and was gradually adopted for other processes. The first European redox project was launched. The US and China are in the late stages of developing coal gasification project with the use of this reduction-oxidation process. The use of this technology is limited by the total amount of sulfur in crude syngas. If it is less than 40 ton/day, redox process is viable.

The first plants were not too efficient, extracting about 100 kg of sulfur per day. When technology was proven, this number rose to 4 ton/day.

Chemically, the liquid redox process is a case of Claus reaction, which can be divided into five stages. The first stages – hydrogen sulfide absorption, then its ionization, then oxidation of sulfide, then oxygen absorption and oxidation of iron. The presence of iron in this process is due to two reasons. First, it is a donor and acceptor for electrons. Second, iron accelerates the reaction. In practice, the functions can be performed by other metals, but iron is relatively cheap and non toxic to the environment.

Today a rather flexible process has been developed, which allows processing of gas stream containing small amounts of hydrogen sulfide. The main advantages of such systems are:

  • ability to process aerobic and anaerobic gas streams;
  • hydrogen sulfide yield of 99.9% or more;
  • harmless byproducts.

The process allows production of high quality sulfur:

  • more plastic particle structure;
  • quick absorption by soil and degradation;
  • ability to mix with water, general hydrophilic properties.

The redox technology is a good source of active sulfur for agriculture. Sulfur is used for soil acidity correction, plant nutrition and as fungicide.

Diesel fuel purification

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If a vehicle owner notices problems in the fuel system, the source of the problems needs to be found. Often such problems are caused by contaminated diesel fuel. One solution is to study special literature or search the Internet to find quick ways of diesel fuel purification.

Let us generally consider ways to purify fuels, as well as oils. The methods are different, one such difference being the required time. However, the availability of choice is a step forward all in itself!

To purify fuel and oil from hydrocarbons, tar and nitrogen compounds, 96% sulfuric acid solution is used. It is added in the amount of 0.5 – 1% of the product. After that the liquid separates: the top layer of purified product with some residual acid and the bottom layer: a thick black substance (acid sludge). Acid can be neutralized by alkali (mostly by sodium hydroxide).

Besides, alkali can remove acids, hydrogen sulfide, phenols and mercaptan. The substances resulting from treatment with sodium hydroxide, are usually water soluble and can be removed from the fuel with the water solution of alkali.

Adsorbents (bleaching clay or silica gel) are used to remove sulfur compounds, tar and organic acids.

Selective purification is an interesting looking method. This process is based on the ability of some materials to solve contaminants. Some of the solvents are mononitrobenzene, phenol, liquid propane, furfuraldehyde etc. These act differently: some solve the contaminant and are removed, while others solve hydrocarbons and cause precipitation of contaminants. The advantage of the mthod is that after treatment the solvent may be distilled and reused.

To remove high pour point hydrocarbons from oil products (paraffin removal), the product is cooled and then solid crystals of paraffin and ceresine are removed.

Every diesel fuel and oil can be treated with hydrogen at elevated temperature and pressure in the presence of a catalyst. This is called hydrotreatment. It allows thorough removal of sulfur compounds from oil or fuel, due to the fact that hydrogen binds sulfur to form hydrogen sulfide. Specific conditions of the process are such: the product and hydrogen is heated to 400 ºС and enter a special reactor with the pressure of 50 kg per cm2.

Still, probably the simplest method of fuel purification is the centrifuge. It helps to remove water, tar and solids from the fuel.

In practice, it is best to trust proven equipment, tested and tried in the field of oil and diesel fuel purification. Something like the UVR systems, which can lighten diesel fuel and HFO, gas condensate and gasoline. The main advantage of the UVR is its versatility: beside the above mentioned products, these systems handle regeneration of various oils, such as turbine, industrial, transformer etc, equally well.

By purchasing a UVR unit made by GlobeCore, you can process various products with the output in full compliance with the existing norms and regulations.

Diesel fuel: removal of paraffin by electric fields

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Partial removal of paraffin from diesel fuel by direct current fields is quite efficient. First, it allows to improve the low temperature performance of fuel. Second, diesel fuel retains some of the n-paraffin hydrocarbons, which define the cetane number. Third, removal of paraffin increases diesel fuel yield from crude oil in comparison to traditional purification methods. Fourth, the electric purification process is significantly simpler than such methods as hydrodewaxing. The drawback is the requirement of low temperature for the process, which, incidentally, also makes it suitable for cold areas.

Removal of paraffin requires special electric dewaxer machines. Each cycle of operation consists of several operations.

First, diesel fuel premixed with an additive enters the interelectrode space through lower side inlets of the system. The fuel can travel from one interelectrode space to another through gaps. Positively charged electrodes are meshes and do not impede movement of the liquid.

To eliminate overflow when fuel level is exceeded, the fuel is drained through the top connector to a special vessel. The interelectrode space is pre-calculated and must consider the thickness of sediment forming on the electrodes. In practice, the sediment rarely exceeds 10-15 millimeters.
When the electrodes are energized, paraffin sediment forms on both sides of the electrodes. Diesel fuel is then removed from the chamber, maintaining power on the electrodes.

The equipment is built with an incline to outlets to accelerate output of the processed fuel.
After fuel is removed, power is disengaged, then paraffin is removed from the electrodes. The latter operation is carried out by warm liquid. The molten paraffin drains to the bottom of the tank and is removed through lower outlets.

After this, the machine and the bottom of the unit should be cooled down to process temperature. To do so, cold liquid is circulated through the tank.

Kerosene, thickened with silicagel or calcium chloride, serves as both cooling and heating agent. Its dielectric properties are also a factor.

Hydrotreatment of diesel fuel

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Today, the desired properties of diesel fuel is mostly dictated by environmental considerations. The European community pays a lot of attention to environmental issues, making its requirements to chemical composition of diesel fuel ever stricter.

Thus, beginning with January 2005, the Euro-4 regulations, limiting sulfur content in diesel fuel to 50 ppm, came into force. Four years later, Euro-5 regulations were introduced, with 10 ppm max sulfur content in diesel fuel. Polycyclic aromatic hydrocarbon content requirement was reduced to 2%. With time, the regulations will be increased to 95% distillation point of 340-350ºС and the cetane number to 54-58. Fuels compliant with this standard, are made in Sweden, the UK, Finland and Germany.

Sulfur compounds are more difficult to remove from diesel fuel than from benzene, since the former are less reactive. Their rate of decay is significantly lower in transformation from triophen to trimethyldibenzothiophene.

Hydrodewaxing is applied for production of diesel fuel with the required operational parameters. The feedstock for this process is straight-run diesel fractions, which boil out of low sulfur, high sulfur and sulfur crude oil at 180-330ºС, 240-360 ºС and 180-360ºС accordingly.

To ensure low sulfur content in fuel (15 ppm or so), a deep hard hydropurification is required, at 9-10 MPa and 315-400ºС. Hydrogen consumption is high, and volume velocity of petrochemicals along cobalt-molybdenum or aluminum-nickel-molybdenum catalysts is low.

The following are the output parameters of the process:

  • weight yield – up to 97%;
  • hydrocarbon gas – до 0,7%;
  • benzene – до 1,5%;
  • hydrogen sulfide – до 2,5%.

The drawback of the hydrotreatment is its low versatility. GlobeCore manufactures and supplied versatile UVR-450/6 systems, which can lighten not only diesel fuel, but also HFO, benzene, kerosene and gas condensate, regenerate transformer, turbine and industrial oil. The unit does not require constant operator attention, operating in either manual or automatic mode. Human interference is only needed for start, stop and sorbent replacement.

The UVR-450/6 is very energy efficient. When switching from one processed product to another, it is only required to drain the remaining product from the system, replace sorbent and filters. There are no additional complicated operations involved.

The role of oil and gas in modern world

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Energy is a key resource in today’s economy. National production development is largely defined by the consumption of energy. The importance of energy resources is emphasized by the fact that over 70% of mineral resources are sources of energy.

The main energy sources today are coal, oil, natural gas, hydropower and nuclear power.

Oil and gas have become the leaders in world energy since the 1960s. In Germany and the UK, for instance, oil and gas account for 55-60% of total energy consumption, while the the US and Japan the number is even higher: 75 – 80%.

Some of the advantages of oil and gas as energy sources are relatively low production cost, waste-free processing with production of various types of fuel and chemicals. However, world deposits of oil and gas are not limitless. They are significantly lower than coal, shale and asphaltic sand. At the same time, the production of oil and gas by far exceeds that of other combustible minerals.

The high level of oil consumption causes the concern that the world supply of oil may be exhausted in the relatively near future. It is commonly accepted that oil is due to run out by the end of the 21st century.

As oil became the main energy source, its political and economic significance has increased. Availability of own oil, the ability to organize export of oil and oil products has allowed some countries many achievements in their economic and social development. At the same time, the fluctuations of the world’s oil prices and the market condition lead to significant changes in the policy of both oil producing countries and those countries with economy based on imported oil.

The world oil prices have been fluctuating in recent  years.  In the first years after World War II, the price of oil was dictated by the International oil cartel, dominated by the US. The cartel purchased oil from exporters, developing nations, at low price (22 USD per 1 cubic meter in 1970), while selling oil products to importers at relatively high prices.  To protect their economic interests, the developing nations created OPEC in 1960. OPEC includes Iraq, Kuwait, Saudi Arabia, Qatar, Venezuela, Indonesia, Libya, Nigeria, Algeria and Ecuador.

Considering a sharp increase of demand in the world market, OPEC increased their pressure on the oil monopolies in 1972-1973 and increased the price four times. The increase lead to unstable oil supply in several industrialized countries and oil shortages.

The West implemented measures to decrease their dependence on foreign oil by increasing their production of own oil and coal,  reducing consumption and the use of other energy sources (solar, nuclear and geothermal). These measures caused the world oil price to drop.

The chemistry of catalytic reforming

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The chemistry of catalytic reforming

Catalytic reforming is a complicated process which involves various transformations of hydrocarbons. Straight run gasoline fractions, which are the raw material of the catalytic reforming, contain parafins, naphthenes and aromatics.

The reactions in the catalytic reformers deeply transform the hydrocarbons. Aromatization of hydrocarbons is the main and most important direction of the process. Before looking at various reactions, it should be noted that reforming catalysts feature two types of catalytically active centers: dehydrating centers on platinum and isomerizing centers on the carrier.

One of the main reactions of the process is dehydration (dehydrogenation) of naphthenic hydrocarbons. Dehydration of pentatomic hydrocarbon rings of naphthenic hydrocarbons occurs through formation of cycloolefine hydrocarbons with rearrangement of the ring.

The second type of reaction is dehydrocyclization of paraffinic hydrocarbons; the mechanism of this reaction is not entirely clear yet. Aromatization of paraffinic hydrocarbons may occur either by formation of naphthenic or olefinic and cycloolefinic hydrocarbons.

Other main reactions of the process include isomerization of paraffinic hydrocarbons, which occurs via an intermediate stage of carbonium ion formation; in reforming conditions isomerization leads to formation of unbranched isomers.

Hydrocracking reactions run in parallel on reforming catalysts.

Hydrocracking affects paraffinic hydrocarbons, and, to a lesser extent, naphthenic hydrocarbons. Hydrocracking of paraffins occurs in several stages through formation and disintegration of carbonium ions. Propane and high-molecular compounds prevail in the products of this reaction. Hydrocracking occurs on acidic centers of the catalyst, but the first and final stages of the process, I.e. formation of olefins and hydration of other breakdown products, occur on the metal parts of the catalyst, which feature the hydration-dehydration function.

Hydrocracking of paraffinic hydrocarbons leads to formation of two or more hydrocarbons with lower molecular mass.

In some cases of reforming, hydrogenolysis becomes significantly developed on the metal parts of the catalyst. Unlike hydrocracking, hydrogenolysis leads to more prominent formation of gaseous hydrocarbons, especially methane. In the process of hydrogenolysis, the destruction of carbon-carbon bonds of methyl cyclopentane leads to formation of paraffinic hydrocarbons.

Besides, reforming favors reactions which significantly influence catalyst activity and stability; including formation of coke on the catalyst, as well as hydrodecay of sulfuric, nitric and chlorine substances.

Formation of coke is related to the reactions of compaction on the surface of the catalyst. This causes not only reduction of catalyst activity, but also degrades process selectiveness. Coke formation is promoted by decreased partial pressure of hydrogen and molar hydrogen/raw material ratio, poisoning of the catalyst by contact poisons, disruption of balance between hydrating and acidic functions of the catalyst, processing of raw material with increase content of light (C5 – C6) and heavy (C10 and above) hydrocarbons.

The fastest of the main reforming reactions is the reaction of dehydrogenating of alkyl cyclohexanes into the corresponding aromatic hydrocarbons, the slowest reactions are de dehydrocyclization of paraffinic hydrocarbons. The rate of naphthenic and paraffinic C6 – C10 hydrocarbons increase on homologous sequences with the increase of molecular mass.

Reforming reactions leading to formation of aromatic hydrocarbons from naphthenic and paraffinic substances absorb heat; hydrocracking and hydrogenolysis reactions emit heat, isomerization reactions of paraffinic and naphthenic hydrocarbons have little thermal effect. For C5 – C10 hydrocarbons, molar thermal effects are almost independent of molecular mass and change little in the temperature range of 470 – 500oC.

Antiknock agents

Articles, Fuel blending

Antiknock agents are compounds which include the antidetonants proper, scavengers and other substances which improve the product performance.

Lead compounds has been used as some of the most effective antiknock agents for over seventy years. The most known of these is tetraethyllead, a transparent, colorless highly toxic dense liquid (1.6524 g/cm3). Tetraethyllead dissolves well in gasoline, ethyl, acetone and some other solvents. It boils and decomposes at around 200°С. The vapor in small concentrations have a sweet scent, as concentration grows, the smell becomes rather unpleasant.

Another well known lead antiknock agent is tetramethyllead. It is also a liquid with unpleasant aroma, boiling at 110°С. It’s density is 1.995 g/cm3. Due to the relatively low boiling temperature, which constitutes about 50% of gasoline boiling temperature, this substance distributes more evenly in gasoline fractions and the cylinders of the engine. Tetramethyllead is more thermally stable than tetraethyllead: at 744°С tetraethyl lead decomposes to 65% in 5.6 ms, while tetramethyllead only decomposes to 8%. This difference ensures better efficiency of tetramethyllead as compared to tetraethyllead in high pressure ratio internal combustion engines and when used in highly aromatic gasolines.

A common drawback of both compounds is the extremely high toxicity of the agents and burn products, with severe impact on the environment and negative influence on exhaust gas aftertreatment devices. For these reasons the use of tetraethyllead and tetramethyllead is being decreased and intensive research into other efficient antiknock agents is underway.

The research of the antiknock agents progresses in two directions: organometallic and organic compounds. Among the organometallic compounds, apart from tetraethyllead and tetramethyllead, the most efficient are manganese and ferrous compounds.

Some of the compounds which have already been studied and tested and used at various times as antoknock agents, are Methylcyclopentadienyl manganese tricarbonyl (MMT), Cyclopentadienyl manganese tricarbonyl (CMT), Dicyclopentadienyl iron and its alkyl derivatives, iron pentacarbonyl etc. In terms of antiknock efficiency, manganese compounds are analogous and iron compounds are only somewhat inferior to lead.

CMT is a volatile crystalline substance of yellow color (melting point 77°С). It is stable in the air, well soluble in organic solvents and is insoluble in water.

MMT is a clear low viscosity liquid of light amber color with a grassy smell, boiling point of 233°С, density of 1.388 g/cm3 and freezing point of 1.5°С, well soluble in gasoline and practically insoluble in water.

Ferrocene is a solid orange crystalline substance, with melting temperature 173°С, subliming temperature 100°С and decomposition temperature 474°С.

Iron pentacarbonyl is a straw color liquid with boiling temperature of 102.5°С and freezing temperature -2°С, insoluble in water.

Ferrocenyldimethylcarbinol is a fine crystal powder with melting temperature 59.5°С.

Organometallic anti-knock agents cause sedimentation of metals on the walls of the cumbustion chamber and on spark plug electrodes. This sediment leads to increased cylinder and piston ring wear, as wells spark plug problems.

Therefore organometallic anti-knock additives are used in combination with scavengers: materials which convert churly metal oxides into volatile compounds.

Common scavengers are alkyl halides: bromo-ethane (boiling temperature 34.4°С), dibromoethane (131.7°С), dichloroethane (83.3°С), naphthalene monochloride (25°С). Some phosphorus and sulfur compounds are used with manganese and iron anti-knock agents. However, the scavengers for these agents are now efficient enough yet, which limits their widespread use.

Due to extraordinary toxicity of lead anti-knock agents, newly found significant disdvantages and high cost of manganese and iron anti-knock additives, the research for an organic antiknock material, which does not contain metal, is ongoing.

Such anti-knock agents are first of all the organic amines: methylaniline, xylidine, extralyne (a mix of 7% aniline, 88% methylaniline and 5% xylidine). The latter was added to blue aviation gasoline in late 40s in the amount of 2% by volume.

When adding aromatic amines to a blend of primary standards (70% isooctane and 30% n-heptane) in the amount of 2% vol, the octane number increase by 5 – 7 points (MM) and 8 – 9 point (IM).

When adding these antiknock agents to gasoline with octane number 86 (IM) in the amount of 2% by volume, the octane number increases by 4 – 5 (MM and by 5 – 6 (IM) points, and by 7 – 8 and 9 – 11 points respectively, when the amount is 5%.

A diesel fuel producing fungus found…

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There is nothing surprising about this find, since microscopic organisms, which synthesize certain hydrocarbons, had been found before. The special thing about this fungus is that it makes 55 types of hydrocarbons. It was located inside wood fibers of Eucryphia cordifolia (a tree from northern Patagonia) and was named Gliocladium roseum. According to Dr. Gary Strobel (one of the authors of the research), no one has seen anything like that before. The research was reported by Montana State University.

Biodiesel, diesel, diesel fuel, biofuel producing fungus

The results of the research were published in the Microbiology magazine. Mass-spectrography indicated that the fungus excretions contain octane, 1-octen, heptane and hexadecane, which are all components of diesel fuel. Of course, the amounts are far less than what is required for industrial production. It has been suggested that the fungus uses these substances for “clearing” the adjacent surfaces from competing neighbors. However, the find will not be in vain. Scientists hope to research the genome of the fungus and extract the genes used for hydrocarbon synthesis to create industrially feasible species.