What is the reason of Acid rain ?

The primary reason for acid rain is the release of certain pollutants into the atmosphere, namely sulfur dioxide (SO2) and nitrogen oxides (NOx). These pollutants are primarily emitted from human activities such as:

1. Burning Fossil Fuels: The combustion of fossil fuels, such as coal, oil, and natural gas, in power plants, industrial facilities, and vehicles releases sulfur dioxide and nitrogen oxides into the air. These pollutants are byproducts of combustion processes.

2. Industrial Processes: Various industrial activities, including manufacturing, refining, and chemical production, emit sulfur dioxide and nitrogen oxides as part of their operations. These emissions contribute to the accumulation of pollutants in the atmosphere.

3. Vehicle Emissions: Cars, trucks, buses, airplanes, and other forms of transportation burn fossil fuels, which produce sulfur dioxide and nitrogen oxides as exhaust gases. Urban areas with high traffic density often experience elevated levels of these pollutants.

4. Agricultural Practices: Certain agricultural activities, such as the use of nitrogen-based fertilizers and the burning of crop residues, can release nitrogen oxides into the atmosphere, contributing to acid rain formation.

Once in the atmosphere, sulfur dioxide and nitrogen oxides undergo chemical reactions with water vapor, oxygen, and other compounds to form sulfuric acid (H2SO4) and nitric acid (HNO3). These acids can then be transported over long distances by wind currents before falling to the Earth's surface as acid rain, snow, fog, or dust.

While natural sources such as volcanic eruptions can also release sulfur dioxide and nitrogen oxides, human activities are the primary drivers of increased levels of these pollutants in the atmosphere, leading to the phenomenon of acid rain. Efforts to mitigate acid rain typically involve reducing emissions of sulfur dioxide and nitrogen oxides through regulatory measures, technological improvements, and the adoption of cleaner energy sources.

The effects of acid rain for the environment

 Acid rain is a type of environmental pollution that occurs when sulfur dioxide (SO2) and nitrogen oxides (NOx) are released into the atmosphere through industrial processes, vehicle emissions, and natural phenomena like volcanic eruptions. These pollutants react with water, oxygen, and other chemicals in the atmosphere to form sulfuric acid and nitric acid, which then fall to the ground as acid rain.

The effects of acid rain can be detrimental to the environment, including:

1. Damage to Vegetation: Acid rain can damage forests, crops, and other vegetation by disrupting nutrient uptake and damaging foliage. It can also leach important nutrients from the soil, affecting plant growth.

2. Harm to Aquatic Life: Acid rain can acidify bodies of water such as lakes, rivers, and streams, posing a threat to aquatic life. It can harm fish, amphibians, and other aquatic organisms by disrupting their reproductive cycles, damaging their gills, and altering the pH balance of the water.

3. Corrosion of Buildings and Infrastructure: The acids in acid rain can corrode buildings, monuments, bridges, and other structures made of limestone, marble, metal, and other materials. This corrosion can weaken structures and lead to deterioration over time.

4. Impact on Human Health: While direct exposure to acid rain is not a major health concern for humans, the pollutants that cause acid rain, such as sulfur dioxide and nitrogen oxides, can contribute to respiratory problems and exacerbate conditions like asthma and bronchitis.

Efforts to reduce acid rain have included implementing emissions controls on industrial facilities and vehicles, using cleaner energy sources, and international agreements to limit pollution. Despite these efforts, acid rain remains a significant environmental issue in many parts of the world.

The difference between TBN and TAN

TBN (Total Base Number) and TAN (Total Acid Number) are both measures used in the analysis of lubricants and oils, particularly in engines, to assess their condition and performance. However, they represent different aspects of the oil chemistry:

1. Total Base Number (TBN):

   • TBN measures the reserve alkalinity of an oil, indicating its ability to neutralize acids formed during the combustion process in an engine.
   • It represents the amount of alkaline additives, such as detergents and dispersants, present in the oil to counteract the acidic by-products of combustion and chemical degradation.
   • Higher TBN values indicate greater acid-neutralizing capability and, therefore, better protection against corrosion and wear caused by acidic compounds.

2. Total Acid Number (TAN):

   • TAN measures the acidity of an oil, specifically the amount of acidic components present in the oil due to oxidation, thermal degradation, and contamination.
   • It reflects the concentration of acidic contaminants, such as oxidation products, organic acids, and inorganic acids, which can corrode engine components and degrade the lubricating properties of the oil.
   • Increasing TAN values indicate higher levels of acidic compounds and potential degradation of the oil, which may necessitate oil changes or other maintenance actions to prevent engine damage.

In summary, while TBN indicates the alkaline reserve of an oil to neutralize acids, TAN measures the actual acidity level of the oil due to various factors. Monitoring both TBN and TAN is essential for assessing the condition and performance of lubricants and oils in engine applications, helping to ensure proper lubrication and prolonging the life of engine components.

TBN In Diesel Engine Oils

In diesel engine oils, Total Base Number (TBN) plays a critical role in maintaining engine health and performance. Here's why TBN is significant in diesel engine oils:

1. Neutralization of Acids: During the combustion process in a diesel engine, various acidic by-products are formed, including sulfuric acid and other acidic compounds. These acids can lead to corrosion of engine components and degradation of the oil's lubricating properties. The TBN of the oil indicates its ability to neutralize these acidic compounds, thereby preventing corrosion and maintaining oil stability.

2. Protection Against Wear: Acidic compounds can accelerate wear on engine parts, such as piston rings, cylinder liners, and bearings. By neutralizing these acids, diesel engine oils with a sufficient TBN help protect critical engine components from premature wear and extend their service life.

3. Extended Drain Intervals: The TBN of diesel engine oils influences the recommended oil change intervals. Oils with higher TBN values typically have greater acid-neutralizing capacity and can maintain their effectiveness for a longer period, allowing for extended drain intervals. This can result in cost savings and reduced maintenance downtime for diesel engine operators.

4. Performance in High-Sulfur Environments: Diesel fuels with higher sulfur content can lead to increased formation of acidic by-products during combustion. Engine oils with higher TBN values are better equipped to handle these conditions, providing enhanced protection against corrosion and maintaining oil stability in high-sulfur environments.

5. Oil Condition Monitoring: Regular monitoring of TBN levels is essential for assessing the health and effectiveness of diesel engine oils. TBN analysis helps determine when the oil's acid-neutralizing capacity is depleted, indicating the need for an oil change to prevent potential engine damage.

In summary, TBN is a crucial parameter in diesel engine oils, providing protection against acidic corrosion, minimizing wear on engine components, extending oil change intervals, and ensuring optimal engine performance, particularly in challenging operating environments with high sulfur content.

Fuel Characteristic Definition as per ISO 8217:2010

ISO specification 8217 stipulates acceptable characteristics of marine fuel oil products. In order to understand the relative importance of each characteristic it is important to understand the definition. The following definitions are deemed useful to users of marine fuels products.

Viscosity A measure of fluid resistance to flow. Viscosity of fuel oil decreases with increasing temperature. The viscosity of the fuel oil at the point of injection into the engine is key to performance. Viscosity is used to classify residual fuel types but is not a key indicator of fuel quality. For example, all other characteristics being equal, a fuel of 360 cSt is of no better or worse quality than a fuel of 400 cSt, it is just less viscous.

Density Mass per unit volume of a product. It is used to convert the volume delivered into the quantity purchased. Density varies with temperature and is an important parameter in the onboard purification of the marine fuel product.

Calculated Carbon Aromaticity Index (CCAI) The most widely accepted empirical formula to estimate the ignition quality of fuel oil. CCAI uses the physical properties of density (d) and viscosity (V) in the following equation: CCAI = d - 81 –141*log [log (V+0.85)]

Sulfur Sulfur is the main inorganic component of fuel. It occurs naturally in crude oils and tends to concentrate in the heavier fractions. Sulfur concentration in fuel oil strongly influences the choice of lubricant. Energy content of fuel oil diminishes with increasing sulfur.

Flash Point Flash point is the minimum temperature at which vapours released from the fuel oil will ignite when exposed to an open flame. The flash point of a blended fuel oil is the same as that of the lightest component in the fuel oil product.

Acid Generally, marine fuel products should not contain inorganic acids, however ISO 8217 allows for minimal acceptable levels.

Sediment Sediment in distillates is composed mainly of rust, general dirt & scale. Marine fuel oil sediment can be both inorganic and organic in nature.

Carbon Residue Carbon residue is a measure of the carbonaceous material left after the volatile components of a fuel have been vaporized in the absence of air. It is used to estimate the potential of a fuel to create deposits in an engine upon combustion.

Pour Point The pour point of a fluid is the lowest temperature at which it ceases to flow. In fuels, the pour point is largely determined by the petroleum wax content in the oil. Pour point determines the minimum temperature required for storage and handling onboard of fuel oil products.

Ash Ash is the carbon free (inorganic) residue remaining after completely burning the fuel in air. It occurs naturally in crude oils and tends to concentrate in the heavier fractions. Ash can contain hard and erosive particles, some of which may also be corrosive.

Vanadium Vanadium is a metal occurring naturally in some crude oils and is concentrated in residual components during refining. In high concentration, it can form high melting point, corrosive deposits. In combination with sodium, it can form lower melting point, oxygen deficient deposits.

Sodium Sodium occurs naturally in crude oils and is concentrated in residual streams during refining. It can be introduced into fuel streams as a scavenger used to control the hydrogen sulfide content of fuel oil, via salt water contamination, or through sodium ingress into a marine diesel engine due to salt water saturated air.

Cat Fines Cat fines contamination in fuel oil is caused by carryover of catalytic material used in the refining process and evidenced by the presence of Alumina and Silica. Cat fines are hard and abrasive.

Used Lubricant (or Lube) Oil Some used lube oil may contain components harmful to an engine, but all used lube oils may not necessarily be unfit for purpose. Some additives used to identify used lube oil such as calcium are naturally occurring in crude oil and hence residual fuel. Test methods are designed to eliminate false positives.

Calcium A soft grey alkaline earth metal, the fifth most abundant element in the earth’s crust. Essential for living organisms, particularly in cell physiology, and is the most common metal in many animals. Calcium occurs naturally in crude oils. It is introduced into the combustion space via cylinder lubrication oil. The alkaline Total Base Number (TBN) additives of cylinder lube oil contain calcium. Calcium is concentrated in the residual part of the refinery process as lighter products are removed.

Compatibility Compatibility of a fuel is a function of the stability of the two individually stable oils used to blend marine fuel oil when they are co-mingled. Heavy marine fuels are complex mixtures of hydrocarbons. Some very large molecules called asphaltenes are held in suspension by maltenes. Mixing fuels can adversely affect this equilibrium.

Fundamentals of Refinery Processing

The basic products from fractional distillation are:

Liquid petroleum gas (LPG) has carbon numbers of 1-5 and a boiling point up to 20 °C. Most of the LPGs are propane and butane, with carbon number 3 and 4 and boiling points -42 °C and -1 °C, respectively. Typical usage is domestic and camping gas, LPG vehicles and petrochemical feedstock.

Naphtha, or full range naphtha, is the fraction with boiling points between 30 °C and 200 °C and molecules generally having carbon numbers 5 to 12. The fraction is typically 15–30% of crude oil by weight. It is used mainly as a feedstock for other processes:

• In the refinery for producing additives for high octane gasoline

• A diluent for transporting very heavy crude

• Feedstock to the petrochemical olefins chain

• Feedstock for many other chemicals

• As a solvent in cleaning

Gasoline has carbon numbers mainly between 4 and 12 and boiling points up to 120 °C. Its main use is as fuel for internal combustion engines. Early on, this fraction could be sold directly as gasoline for cars, but today’s engines require more precisely formulated fuel, so less than 20% of gasoline at the pump is the raw gasoline fraction. Additional sources are needed to meet the demand, and additives are required to control such parameters as octane rating and volatility. Also, other sources such as bioethanol may be added, up to about 5%.

Kerosene has main carbon numbers 10 to 16 (range 6 to 16) boiling between 150 °C and 275 °C. Its main use is as aviation fuel, where the best known blend is Jet A-1. Kerosene is also used for lighting (paraffin lamps) and heating.

Diesel oil, or petrodiesel, is used for diesel engines in cars, trucks, ships, trains and utility machinery. It has a carbon number range of 8 to 21 (mainly 16-20) and is the fraction that boils between 200 °C and 350 °C.

White and black oils: The above products are often called white oils, and the fractions are generally available from the atmospheric distillation column. The remaining fraction below are the black oils, which must be further separated by vacuum distillation due to the temperature restriction of heating raw crude to no more than 370-380 °C. This allows the lighter fractions to boil off at a lower temperatures than with atmospheric distillation, avoiding overheating.

Lubricating oils, or mineral base lubricating oil (as opposed to synthetic lubricants), form the basis for lubricating waxes and polishes. These typically contain 90% raw material with carbon numbers from 20 to 50 and a fraction boiling at 300-600 °C. 10% additives are used to control lubricant properties, such as viscosity.

Fuel oils is a common term encompassing a wide range of fuels that also includes forms of kerosene and diesel, as well as the heavy fuel oil and bunker that is produced at the low end of the column before bitumen and coke residues. Fuel oil is graded on a scale of 1 to 6 where grade 1 and 2 is similar to kerosene and diesel, 3 is rarely used anymore. 4-6 are the heavy

fuels, also called Bunker A, B and C, where B and C are very high viscosity at normal ambient temperatures and requires preheating to about 100 °C and 120 °C respectively, before it flows enough to be used in an engine or burner. Fuel oil grade 4 does not require preheating and is sometimes mixed with off spec products, such as tank residue and interface liquid from multiphase pipelines or with grade 2 fuel oil to achieve low-enough viscosity at ambient temperatures. Fuel oil 6 is the lowest grade, its specification also allows 2% water and 0.5% mineral soil and is consumed almost exclusively by large ships in international waters, where pollutants such as sulfur is less regulated.

Bitumen and other residues like coke and tar has carbon numbers above 70 and boiling points above 525 °C. Low sulfur coke can be used for anodes in the metals industry (aluminum and steel) after processing (calcining). The remainder is a problem fuel, because of high sulfur content and even higher CO2 emissions than coal (typically 15% higher). Bitumen in the form of asphalt boiling above 525 °C is used for roofing and road paving. Asphalt concrete pavement material is commonly composed of 5% asphalt/bitumen and 95% stone, sand, and gravel (aggregates).

Calculation of Fuel Quantity & Density-Volume Correction Factor

To calculate the weight of the fuel, we need to find out the volume and temperature. Having Density and temperature, enter Table 54B to obtain Volume Correction Factor.

Mass = Density x Volume

         = VCF x WCF x Actual Sounded Volume 

Where: 

         Density = Temperature Corrected Density = VCF x WCF 
         Volume = Actual Sounded Volume 
         VCF = 1- {(T-15) * 0.00064} 
        WCF = Density @ 15 deg.C - 0.0011

CCAI related bunker issues

In these days of burning residual fuels in our ships, various types of fuel related problems occur. These can, while being evident, be a considerable 'pain in the neck' for the engine crew and for the operator of the vessel. Hence, the measures to be taken from the owner's side to avoid these hick-ups are to specify as appropriate as possible the grade of fuel required for 'his' engine. And in case of a dispute, to be a subscriber to a recognized fuel analyzing scheme. Sampling procedures for receiving fuel should be accepted by all involved parties.

Let us dwell for a moment on the issue of ordering bunkers and the specification that normally is submitted to ensure the correct grade is received on board. A number of parameters are normally mentioned, such as; density max, viscosity max, sulphur max, poue point etc. There is however a parameter rarely being mentioned in these specifications and that is the CCAI, Calculated Carbon Aromaticity Index, which gives a value on the Ignition Quality for residual fuels, since these grades cannot be verified by methods used for distillates, i.e. Diesel Index, Cetane Index and Cetane Number.

Accepted method for determination of the ignition quality of residual fuels is currently not available. It has, however, been empirically established that there is a relationship between the density, the viscosity and the ignition performance and the Shell-developed CCAI is the one presently most accepted for indicating ignition delay, although there is also a BP- developed Calculated Ignition Index (CII). CCAI gives an idea of how much the ignition is delayed, the higher the index, the longer the delay. The CCAI can be determined, with limited accuracy, by the enclosed nomogram AAAA

The combustion starts with a short delay already when a small amount of the fuel has been injected and therefore the remaining quantity injected burns in a controlled manner. If,however, the delay is long, a large amount is injected before the combustion starts,producing a quick and violent raise of pressure. This produces the characteristic"diesel knock". The problem is generally related to medium speed diesel engines when burning blended fuels less than 220 cSt. and problems seems to appear in the CCAI-span 850-890. See enclosed diagram BBBB If it is required (necessary) to operate the engine within this span the stresses on the engine components might increase considerably and special attention should be paid to:

0  Connecting rod big-end and bearing shells.

0   Main bearing shells

0  Pistons(particularly composite pistons)

0  Piston rings and liners

0  Cylinder head with studs and gaskets

0  Tie bolts

0  Intake and exhaust valves

To alleviate the effect of the ignition delay, the ambition should be to keep the engine load within 50 - 85 % and to maintain the inlet air temperature  as high  as practically possible and through pre-heating prior start-up(the CCAI problems  are accentuated on a cooler engine, hence a known  scenario is the vessel makes it to port but the engine can not be restarted upon departure due to fouled/clogged piston rings, poppet valves and turbocharger).With the violent increase of combustion pressure, when operating on fuels delaying the ignition, the rate of blow-by will increase and it goes without saying that the lub.oil quality must be optimal to cope with the additional load imposed on the bearings.

So, by way of conclusion, if the shipowner is operating engines which  are sensitive to ignition quality he would  be wise to order fuels with a CCAI limit or to set density and viscosity limits which will control the CCAI.

Special care to CCAI is needed when a ship is forced to use low viscosity fuels (below

180 cSt), due to heating limitations. If the density of these fuels is high the CCAI will be too high and ignition problems may be encountered.