Unit-4 Notes PDF

## UNIT-IV Fuels ### Analysis of Coal **1. Proximate Analysis** - Moisture content - Volatile matter - Ash content - Fixed carbon in coal #### Proximate Analysis Definition It is the analysis involving the determination of physical constituents like percentage of moisture content, volatile matte...

## UNIT-IV Fuels ### Analysis of Coal **1. Proximate Analysis** - Moisture content - Volatile matter - Ash content - Fixed carbon in coal #### Proximate Analysis Definition It is the analysis involving the determination of physical constituents like percentage of moisture content, volatile matter, ash content and fixed carbon in coal. #### 1. Moisture Content ##### Method About 1 gm of powdered air-dried coal sample is taken in a crucible and is heated at 100-105°c in an electric hot-air oven for 1 hour. After 1 hour, the crucible is cooled in a desiccator and weighed. ##### Calculation % of moisture in coal = (Loss in weight of the coal) / (weight of air-dried coal) * 100 #### 2. Volatile Matter ##### Method After the analysis of moisture content, the crucible with residual coal sample is covered with a lid, and is heated at 950±20°C for 7 minutes in a muffle furnace. ##### Calculation % of volatile matter in coal = (Loss in weight of the coal) / (Weight of air-dried coal) * 100 #### 3. Ash Content ##### Method After the analysis of volatile matter, the crucible with residual coal sample is heated without lid at 700±50°C for 1 ½ an hour in a muffle furnace. ##### Calculation % of Ash content = (weight of Ash formed) / (Weight of air-dried coal) * 100 #### 4. Fixed Carbon It is determined by subtracting the sum total of moisture, volatile and ash contents from 100. % of Fixed Carbon in coal = 100 - % of [moisture + volatile + Ash Content] ### Significance (or) Importance of Proximate Analysis | S.NO | Analysis | Significance of Proximate Analysis | |---|---|---| | 1. | Moisture Content | High % of moisture is undesirable because <br> 1. It reduces the calorific value. <br> 2. It increases the transport cost. | | 2. | Volatile matter | High % of volatile matter is undesirable because <br> 1. It reduces the calorific value. <br> 2. It burns with a long flame with high smoke.| | 3. | Ash Content | High % of ash content is undesirable because <br> 1. It reduces the calorific value. <br> 2. It increases the transporting, handling and storage cost. | | 4. | Fixed Carbon | High % of fixed carbon is desirable because <br> 1. It increases the calorific value. <br> 2. It helps in designing the furnace and the shape of the fire-box | ### Distinguish between Proximate Analysis & Ultimate Analysis of coal | S.NO | Proximate Analysis | Ultimate Analysis | |---|---|---| | 1. | Determines the % of moisture, volatile matter, ash Content and Fixed carbon | Determines all elements Component of coal in C, H, O, S, A, N. | | 2. | used to find out heating value GCV | useful for furnace design. | | 3. | It gives idea about the utility/type and some of coal | Helps to calculate the quantity of air required for complete combustion of coal. | ### Metallurgical Coke (Otto-Hoffman's by-product oven method) #### Definition When bituminous coal is heated strongly in the absence of air, the volatile matter escapes out and the mass becomes hard, strong, porous and coherent mass which is called metallurgical coke. #### Requisites (or) Characteristics of good metallurgical coke - Purity - Porosity - Strength - Calorific value - Combustibility - Reactivity - Cost ### Manufacture of Metallurgical coke #### Significance - Increase the thermal efficiency of the Carbonisation process. - Recover the valuable by product. #### Description of the oven 1. The oven consists of a number of silica chambers. 2. Each chamber is about 10-12 m long, 3-4 m height and 0.4-0.45m wide. 3. Each chamber is provided with a charging hole at the top. 4. It is also provided with a gas off take valve and iron door at each end for discharging coke. #### Process of the otto-Hoffman's oven Coal is introduced into the silica Chamber and the Chambers are closed. The chambers are heated to 1200°C by burning the preheated air and the producer gas mixture in the Interspaces between the Chambers. #### For economical heating, the direction of inlet gases and flue gases are changed frequently. The above system of recycling the flue gases to produce heat energy is known as Regenerative System of Heat economy. When the process is complete, the coke is removed and quenched with water. Time taken for complete carbonisation is about 12-20 hours. The yield of coke is about 70%. The valuable by products like Tar, Ammonia, H₂S and benzol etc., can be recovered from coal gas. #### Recovery of by-products | | | | |---|---|---| | Coal gas sprayed | Tar water Sprayed| Ammonia sprunged | | Cooled H₂O | Naphthalene | Petroleum | | Coal gas (pure) | Benzene | Moist Fe₂O₃ | | | | H₂S | #### Advantages of Otto-Hoffman's process - Valuable by product like Ammonia, Coal gas, etc., are recovered. - The Carbonisation time is less. - Heating is done externally by producer gas. ## UNIT-IV Fuels and combustion ### Synthetic petrol (Bergius process) #### Definition The preparation of liquid fuels from solid coal is Called Synthetic petrol (or) Hydrogenation of coal. #### Bergins process (or) Direct method In this process, the finely powdered coal is made into a paste with heavy oil and a catalyst powder (tin en Nickel oleate) is mixed with it. #### The paste is pumped along with H₂ gas into the converter, where the paste is heated to 400-450°C under a pressure of 200-250 atm. #### Coal dust suspended in heavy oil + H₂) 200-250 atm 400-450°C - Mixture of hydrocarbons (Saturated Higher hydrocarbons) - Crude oil - Gasoline - Middle oil (lower hydrocarbons) #### The crude oil is then fractionated to yield - Gasoline - Middle oil - Heavy oil The middle oil is further hydrogenated in vapour phase to get gasoline. The heavy oil is recycled for making paste again coal powder. The yield of gasoline is about 60% of the coal used. ### Refining of petroleum (or) crude oil #### Definition The process of removing impurities and separating the crude oil into various fractions having different boiling points is called Refining of Petroleum. #### Process This process of refining involves the following steps - Separation of water (Cottrell process) - Removal of harmful Sulphur compounds. - Fractional distillation. #### Various Fractions, Compositions and their Uses | Name of the Fractions | Boiling Range °C | Range of Carbon atoms | Uses | |---|---|---|---| | Uncondensed gas | Below 30 | C₁-C₄ | Domestic and industrial fuel. | | Petroleum ether | 30-70 | C₅-C₇ | As a solvent. | | Gasoline or petrol | 70-120 | C₅-C₉ | As motor fuel, solvent and in dry cleaning. | | Naphtha or solvent spirit | 120-180 | C₉-C₁₀ | As solvent for paints and in dry cleaning. | | Kerosene oil | 180-250| C₁₀-C₁₆ | As a jet engine fuel and for preparing laboratory gas. As Domestic fuel.| | Diesel oil or fuel oil or gas oil | 250-320 | C₁₅-C₁₈ | Diesel engine fuel. | | Heavy oil | 320-400 | C₁₇-C₃₀ | Fuel for ships and in production of gasoline by cracking. | #### Heavy oil on vacuum distillation gives - Lubricating oils - Petroleum jelly - Grease - Paraffin wax - Pitch | | Boiling Range °C | Range of Carbon atoms | Uses | |---|---|---|---| | Lubricating oils | C₁₇-C₂₀ | Lubricants Used in cosmetics and medicines.| | Petroleum jelly | | | Lubricants.| | Grease | | | Lubricants. | | Paraffin wax | C₂₀-C₂₈ | In candles, boot polishes. | | Pitch | Above 400 | C₃₀ and above. | Used for making roads, water proof roofing. | ### Carbon Emission #### Definition It is defined as the release of carbon into the atmosphere. Since green house gas emissions are often calculated as carbon dioxide equivalents, they are often referred to as "Carbon emissions". #### Source Burning of fossil fuels like coal, oil and natural gas are the Primary sources due to the following activates. - Transportation - Electricity production. - Industry - Agriculture - Land use and forestry - Commercial and residential. #### Reduction of carbon emission Carbon emission can be reduced by the following ways - In industry, green house gases can be reduced by many ways - Including energy efficiency. - Fuel Switching. - combined heat and power. - Use of renewable energy. - Avoid of using HFC's in refrigeneration, air conditioning and foury blowing. - In oil and gas production, the leakage of green house gases can be controlled by reducing pressure from pipelines. ### Carbon Footprint #### Definition It is the total amount of green house gases that are generated by our direct and indirect activities. #### Individual Carbon Footprint It is the sum total of their direct and indirect Carbon emissions over the course of a year. #### Smaller your carbon footprint: better for the future. #### Bigger your carbon foot print : Have bigger negative impact the environment. #### Globally the average Carbon footprint is closer to 4 tones. #### To avoid 2°c rise in global temperatures, the average global carbon footprint per year needs to drop under 2 tons by 2050. #### Source of carbon footprint - Climate change - Natural process like voleanos - Green house gases emitted from human activities. - pollution released by human beings doing human things. - Transportation accounted for about 28% of total Country - Electricity generation accounted for about 28% - Industrial activities 22%. - Heating and Cooling in homes and businesses contribute 11% #### 15 ways to reduce your carbon foot print - Calculate your Carbon footprint. - Drive less - Switch to an electric (or) Hybrid Car, - Travel Smart. - Switch to renewable energy, - Consider solar panels. - Make your home more efficient - Turn your thermostat just 2 degrees Cooler in winter & 2 degrees warmer in Summer. - ret energy efficient appliances. - Unplug electrical devices when not in use - Buy locally-Sourced food. - Start home garden - Eat less meat. - Don't waste water. - Reduce, reuse & recycle. ### Power Alcohol #### Definition When ethyl alcohol is blended with petrol at concentration of 5-10%, it is called Power alcohol. When ethyl alcohol is blended with diesel, it is called E-diesel. #### Manufacture - **Manufacture of Ethyl alcohol** Ethyl alcohol can be synthesised by fermentation of Carbohydrates. Fermentation of molasses, which is the residue left after the crystallisation of sugar, with yeast generates alcohol. This fermentation yields only about 20% alcohol. C₆H₁₂O₆ (sugar) Yeast) 2 C₂H₅OH + 2 CO₂ (Ethyl alcohol) Concentration of alcohol can be increased up to 97.6 % by fractional distillation yields rectified Spirit. - **Conversion of Ethyl. alcohol into power alcohol** 100% alcohol (absolute alcohol) is prepared by removing last traces of water from rectified spirit. It can be done by the following two methods. 1. Alcohol is distilled with benzene. 2. Alcohol is distiled in the presence of dehydrating agent, which holds the water. Finally absolute alkohol is mixed with petrol at Concentration of 5-10% to get power alcohols. #### Properties - lower calorific values (7000 k.cal/kg)&#x20; - High octane number (90). - Anti-knocking properties are good.&#x20; - Its compression ratio is also higher - It generates 10% more power than the Jasoline of same quantity #### Uses of power alcohol - It is used, as a very good fuel, in motors, - Its properties are good. #### Advantages of power alcohol - It is cheaper than petrol - If any moisture is present, power alcohol absorbs it. - As ethyl alcohol contains oxygen atoms, complete combustion occurs, so emission of CO, Hydrogen, particulates are redunced. #### Disadvantages of power alcohol - Output power is reducent upto 35%. - As the calorific value of power alcohol is lower than Petrol (7000 cal/gm), specially designed engine is required. (11,500 cal/gm) - Due to its high surface tension, atomization of power alcohol is difficult, so it causes starting trouble. - It may under go oxidation to give acetic acid, which Corrodes engine past. ### Bio-diesel #### Definition Metyl esters of fatty acids, thus formed are called Bio-diesel. Bio-diesel is defined as mono-alkyl esters of long Chain fatty acids derived from vegetable oils (or) fats. Vegetable oil comprise of 90-95% triglycerides with Small amount of diglycerides, free fatty acids, phospholipids, etc. The viscosity of Vegetable oils are higher & their molecular weights are also higher. #### Problem in using vegetable oils directly Oxidation and thermal polymerisation of vegetable oil cause deposit formation. This high viscosity causes misfire and ignition delay, - The use of vegetable oils as direct fuel requires Modification of the conventional diesel engine design. - High volatility & Consequent high flash point lead to more deposit formation. - As the viscosity of wise vegetable oils are high, atomization is very poor. #### Manufacture of Bio-diesel: Trans esterification (or) alcoholysis Trans-esterification is nothing but displacement of alcohol from an ester by another alcohol. It involves treatment of vegetable oil with excess of methanol in presence of catalyst to give monoethyl esters of long chain fatty acid and glycerine is separated Akomolysis reaction is represented as CH₂ -O-C-R CH -O-C-R + 3 CH₃OH CH₂-O-C-R (Triglyceride) CH₂-OH + R -COOCH₃ + R-COOCH₃ (Glycerol) R"-COOCH₃ CH -OH CH₂-OH + (methyl esters of Jeatcy acids) Methyl esters of fatty acids, thus formed are Called Bio-diesel. #### Advantages of Bio-diesel - It is biordegradable - It is prepared from renewable resources. - It can be produced from different types of vegetable oils. - Best engine performances less Smoke emission are achieved. #### Disadvantages of Bio-diesel - Biordiesel gels in wld weather. - It decreases the horse power of the engine. - It can absorbs the water from atmosphere. - It degrades soften the rubber Splastics-used in some old ears. - It has about 10% higher NOx emission than conventional petroleum. ### Flue gas Analysis (ORSAT Method) #### Definition The mixture of gases (like CO₂, O₂, Co etc.,) coming out from the combustion chamber is called flue gases. - If the flue gas contains, CO→ It indicates incomplete combustion - O₂→ It indicates excess supply of airs used in combustion #### Description of orsat's apparatus - It consists of horizontal tube. - At one end has U-tube Containing fused CaCl₂ - In other end has graduated gas burette with water reservoir. #### Working and Function of ORSAT METHOD | Bulb | Reagents | working & Function of orsat method. | |---|---|---| | Bulb-I | KOH solution | Absorption of CO₂ <br> Bulb-I - opened in stop cock <br> Bulb-ⅡⅢ-closed in stop cock <br> The gas entere into the bulb-I, where CO₂ present in the flue gas is absorbed by KOH solution <br> The decrease in volume of the flue gas ish the burette indicates the volume of CO₂ in 100 cc of the flue gas.| | Bulb-Ⅱ| Alkaline pyrogallol Solution | Absorption of O₂ <br> Bulb - I - opened in stop cock <br> Bulb-ⅡⅢ-closed in stop cock <br> The gas enters into the bulb-Ⅱ, where O₂ present in the flue gas is absorbed by alkaline pyrogallol Solution <br> The decrease in volume of flue gas in the burette indicates the volume of O₂| | Bulb-Ⅲ | Ammonical Cuprous Chloride Solution | Absorption of CO <br> Bulb -Ⅲ - opened in Stop cock <br> Bulb-Ⅱ- Closed in stop cock. <br> The gas enters into the bulb-Ⅲ, where CO present in the flue gas is absorbed by ammonical cuprous chloride. <br> The decrease in volume of flue gas in the burette indicates the volume of CO | #### Significance (or) Uses of Flue gas analysis - Gives an idead about the complete con incomplete combustion process. - Flue gas with more CO, Shows incomplete combustion I demand of O₂. - Flue gas with more O₂, Shows complete combustion excess of O₂. #### Precautions of Flue gas Analysis - Care must be taken in such a way that, the reagents in the absorption bulb 1, 2, 3 order, etched marked one by one by raising lowering reservoir bottle. - All the air from the reservoir bottle is expelled to atmosphere by lifting the reservoir bottle. - It is essential that CO2, O2 and CO are absorbed in that order only, as the co content in flue gas is very small, it should be measured quite carefully.