Good morning everyone, welcome to part 1 of the lecture 1 under module 2. In this lecture we will discuss about the concept of solid and the liquid fuels, basic understanding of various properties of the fuels. In that we will discuss about the solid fuel first where we will discuss about the heating value of fuel ultimate analysis and the proximate analysis. Concept of solid and the liquid fuels. The fossil fuel resources that is coal, oil and gas is the primary energy source at present and biomass was the primary fuel before that and still being used in many countries. countries for space heating purpose.
So, if you remember in one of the lecture in the previous model I discuss about this concept of biomass where I mention about biomass is no more counted in the classification of conventional energy sources and now it is accounted under the non-conventional energy sources. The issue associated with the source material is that these particular materials have low energy content and thus their transportation and direct use is enviro economically. infeasible and because of that the conversion of this raw forms of energy into high energy containing product is. essential.
And this can be accomplished through various energy conversion technologies or processes to produce gas, liquid and solid as a product. But there are also certain check we need to take into consideration. The produce product also should have high energy content and it should be easily transportable. less pollutant and suitable for use as commercial fuels.
So, these various fuel sources and their products can be classified in three physical states as follows that is solid fuel, liquid fuel and gaseous fuel. So, solid fuel includes coal, coke, briquettes, charcoal, torrified biomass, biocoque and biochar. So, in that coal, coke, briquettes source from the fossil fuels.
or you can say the fossil source material. Turrified biomass, biocoque and biochar are source from the bio base material. So, biquette in the sense is like it is a block of compressed combustible material. So it may be charcoal, biomass or the waste material and the charcoal is produced in presence of insufficient quantity of air and the torrified biomass is produced in absence of air and the temperature would be between 200 to 300 degrees C.
So, likewise this torrified biomass further can be converted into the briquettes as well. The liquid fuels includes gasoline, diesel, kerosene, fuel oil, coal tar, tar, ethanol, butanol, biodiesel, vegetable oil and the bio oil. So, in that this gasoline to even ethanol these are source from the again fossil fuel materials.
And biodiesel, vegetable oil and the bio oil are basically derived from the biobased material. Even bioethanol are nowadays produced using the biobased material. The gaseous fields include natural gas, liquefied petroleum gas, furnace gas, coke oven gas and coal gas, which are sourced from fossil materials. The producer gas is also produced from the fossil material, that is coal, and the biogas is produced from the biobased material. And the producer gas as I mentioned earlier also, nowadays it is also being produced using the bio-based material by which by the process called a gasification where the biomass is gasified to convert it into a producer gas.
So now let us understand the properties of these various fuels. As discussed before these fuels are produced from the distinct source material and as a result there is a great variation among the properties of these different fuels. sources as well as the product derived from this particular source material because these fuels are derived from different varieties of the source material like solid, liquid and gas. And apart from that various energy conversion technologies or the processes or the systems are being used. to convert this source material into a usable product.
Because of that there is a great variation among the properties of these different fuels which are produced from the even different source material. Hence characterization of the fuels and their feedstock is essential for designing a reliable energy conversion process or system as well as it is essential to understand the compatibility assessment of the different types of feedstock. fuels with specific design equipment or system.
Because the design process or the equipment it should be compatible with the different or the varieties of the feedstock material as well as the source material and it should not be compatible with any single specific fuel or as well as any specific raw material so that it can be a sustainable in the longer run. Apart from that the characterization is essential to control the quality of the produce fuel so that it can meet the the specified fuel quality standards. And the environmental impact assessment is also essential to assess the environmental footprint of the fuels by determining the polluting and the toxic compound present in the source material. And for that reason, the characterization of the fuels and their feedstock is essential. Now after understanding the necessity of characterization of the fuels and the feedstock let us discuss about some important characteristics of fuels and their feedstock which include physical properties, thermodynamic properties and composition.
The physical properties includes density, permeability, diffusivity and the viscosity and this is a comprehensive list and not specific to any single given fuel. Similarly, the thermodynamic properties includes thermal conductivity, heating value, specific heat, heat of combustion, heat of formation and the ignition, temperature and again as I mentioned these are not specific to a single fuel but this is a comprehensive list of the thermodynamic properties. And the composition include the ultimate analysis, the proximate analysis, the structural and chemical composition which includes the cellulose, hemicellulose, lignin and the extractive content in the material. Apart from that the carbohydrate, protein and the lipid content and these are specific to a bio-based material.
And apart from this Properties, there are other tools which are also used to characterize, classify and rank the fuel which includes the atomic ratio that is H by C, O by C and the N by C ratio which is also helpful in classifying or characterizing the fuel. Ratio of lignocellulose constituent that is cellulose, hemicellulose and lignin, this also helpful to rank the lignocellulosic biomass and the ternary diagram. showing the percentage of carbon, hydrogen and oxygen.
It is also useful as one of the tools to characterize or classify the fuel. Now let us discuss about solid fuel in detail. The greatest discovery in history was produced from biomass fuel for heating caves and cooking food in ancient times.
And with advancement of civilization, the utilization of the solid fuels has broadened to domestic use, smelting material as well as to produce the power in the thermal power station. And these solid fuels are grouped in three classes that is biomass, fuel, fossil fuel and waste. So, now let us discuss about these source of solid fuels, their derived product and their ultimate use in the industries.
The source of fossil solid fuels include peat, coal, oil shale, oil sands and tar sands and the product derived from this solid fuels include the peat, coal, oil sands and tar sands and the product derived from this solid coal, coke and the briquette. So, here the peat and the coal are nothing but the upgraded form of this source material which can be upgraded using the suitable upgradation technology with the removal of the foreign material as well as the pollutant and it can produce a high quality coal. Apart from that the briquette here indicates the briquette produced from the coal dust and this particular derived product can be burned to supply energy in the industrial. processes. Similarly, the biomass source material include wood, wood waste, spain pulp, rice compounds, cotton trash, bagasse, coffee grounds, manure and other forms of biomass.
And this particular biomass can be converted into pellets and briquettes or it can be converted into a torrified biomass, biocoque and also biochar. The pellets and the briquettes as I mentioned earlier, it is a block of a combustible material. So here it is a biomass based material.
Similarly, the pellet which is smaller in size can also be obtained from the combustible based material that is a biochar. biomass. The torrified biomass as we already discussed about the torrified biomass in the previous slide.
These particular materials again can be burned in the boiler and in the kilns. And the waste material the sources include the municipal solid waste including the waste from the wood, paper, food, yard and the plastic. Again this particular source material can be converted into pellets and the brick weights as well as the refuse derived fuel and this derived fuel.
fuels can be burned for the steam generation, electricity and for the safe disposal of the society's residues. This can be converted into a suitable form of the energy. As discussed earlier, these solid fuels are sourced from the distinct source material. As a result, they have the distinct physical, chemical and the composition characteristics. And it is essential to characterize this particular solid fuels which eventually helps to create define the behavior of any given solid fuel as well as it will help to select a proper energy conversion technology or a system.
And also it will help in understanding the environmental impact by the utilization of these particular source material for the energy generation. And it includes the physical properties, thermodynamic properties and the composition as we already discussed in the previous slide. The physical properties includes these many properties. The thermodynamic properties include majorly thermal conductivity, heating value, specific heat and heat of combustion and the composition includes ultimate analysis, proximate analysis and the structural composition.
So, here the characteristics of various solid fuels. important in the fuel analysis are summarized in the tabular form which will be very easy to understand even. So, for the biomass based source material the physical properties include the specific gravity and the porosity, thermodynamic properties includes thermal conductivity, specific heat and the heating value and the chemical characteristics include proximate analysis, ultimate analysis and the structural and the composition analysis of the.
biomass. And in case of coal, physical properties include specific gravity, porosity and grindability. And majorly thermodynamic properties include the specific heat and heating value.
Along with that the chemical characteristics include the approximate analysis, ultimate analysis, chemical structure, even the reactivity, chemical component present in the coal. in the form of organic matter and inorganic matter. The waste includes bulk density and porosity.
thermal conductivity, heat capacity and the heating value and ultimate analysis along with the trace metal content. So, we will discuss about these properties one by one. So, first the density, density is an important design parameter for any fuel conversion process or system.
there can be three characteristic densities that is true density, apparent density and the bulk density. So, the true density here It is the ratio of total mass of fuel by solid volume excluding the pore volume of the material. So while calculating the true density, it is basically considered as the total mass of fuel that is weight per unit volume occupied by solid constituents of the biomass is the true density. So in this calculation, the pore volume of the specific source material is excluded.
Whereas, if you see the apparent density, so this consider the internal pores of particle, but not the interstitial volume between the particles which are packed together while estimating the apparent density. And it is the easiest to measure and most commonly used density for the design calculation and it gives the actual volume which is occupied by particle in a system. and it can be calculated using the following equation that is total mass of a fuel by apparent volume including the solids and the internal pores but it does not account the interstitial volume between the particle. And the bulk density it is simply a ratio of total mass of fuel divided by the bulk volume which is occupied by amount or a group of particles. this bulk density can be estimated as per this ASTM standard method as well.
Even these three densities are related as per this following equation that is apparent density equal to true density into 1 minus porosity and even the bulk density can be related with the apparent density into 1 minus bulk porosity. So, for the estimation of this apparent and the bulk density, we need to know the porosity and the bulk porosity of the given sample. And in this particular table the bulk density of the various solid fuels is compared.
Now if you see here the anthracite coal, the bituminous coal and the lignite coal, these samples have relatively a higher bulk density compared to the wood and the serials. In fact the Municipal solid waste is having relatively a higher density than that of the wood and the cereal straw. So, the porosity as we have discussed this concept of the porosity just now. So, this porosity it is an important characteristics of solid fuel including biomass, fossil fuels and MSW and this porosity can be estimated by this simple equation where we need to know the pore volume of a material as well as the total volume of a sample.
So, once we know these two values, so the porosity can be estimated accordingly and it is defined as the ratio of pore volume to the total volume of a solid fuel. Similarly, the bulk porosity is defined as the ratio of interstitial volume to the total packed volume of a solid fuel. So, in the bulk porosity basically the interstitial volume between the particle is considered with that of the total packed volume of a solid fuel. And once we know this bulk porosity and the porosity then easily we can estimate the apparent density and the bulk density of a solid fuel.
And the next in the list includes the thermal conductivity. Thermal conductivity is a measure of materials ability to conduct the heat and thermal conductivity of the material can be defined as the rate of heat transfer through unit thickness of the material per unit area per unit temperature difference and once we know this quantities we can calculate the thermal conductivity of a given material. High k value It indicates that the material is a good conductor of heat. Similarly, low k value, it indicates that the material is appropriate for thermal energy storage. And the thermal conductivity of the fuel, it depends on its composition, the moisture content, density, porosity and temperature.
And next in the list of the properties is the heating value. The higher heating value also known as a gross calorific value. It is defined as the amount of heat released by unit mass or the volume of fuel which was initially at 25 degree C and once it is combusted and products have returned to a temperature of 25 degree Celsius. In case if the fuel contains a moisture then the higher heating value includes the latent heat of vaporization of water.
And if the latent heat of vaporization of water is not recovered then the effective heat which is available for use is less than the chemical energy which is stored in the fuel and therefore lower heating value is introduced here. The lower heating value also known as the net calorific value, it is defined as the amount of heat released by fully combusting a specified quantity of fuel but less the amount of heat of vaporization of water in the combustion product. And this LHV can be estimated using the following expression. LHV is equal to higher heating value minus Hg that is called as a latent heat of steam into 9H by 100 minus m by 100 in the bracket where H is the hydrogen percent and m is the moisture percentage.
And if these values are known then we can calculate the lower heating value of a sample. And as I mentioned earlier the higher heating value of a given fuel. can be estimated using the calorimeter that is also widely known as a bomb calorimeter.
Even the heating value this also need to be defined on the basis of different moisture and the ash content of a fuel. If m kg of fuel contains q kilojoule of heat, m kilogram of moisture and m kilogram of ash then higher heating value can be presented in a three different basis as follows that is on as received basis the amount of heat which is released on combusting mf kilogram of fuel. So, by that way we can calculate the higher heating value. Similarly, on dry basis the higher heating value can be estimated as Q divided by M F minus moisture contained in the fuel that means mass of the fuel minus the moisture contained in the fuel it will gives the net mass of the fuel which is taking part in the combustion process.
So, that is on the dry basis where we have not accounted the moisture and on dry and ash free basis. So, here basically mass of the fuel minus moisture ash. So, by that way we can calculate the high rating value on dry and ash free basis.
Even this high rating values can be correlated as follows that is once we know the high rating value on dry basis that is Q by M F minus M W. So, we just simply take out this mass of the fuel common that is 1 minus mass of moisture divided by the mass of fuel. which can be represented as m here onward. So, once we know the higher heading value because this q by m f is nothing but the higher heading value on the as received basis. So, you can just replace this q by m f as higher heading value on as received basis and the remaining expression will remain as it is.
So, it is the ratio of these two terms where higher heading value on as received basis can be also calculated as high rating value on dry basis into 1 minus m and high rating value on dry and ash free basis it is simply the ratio of again this. terms. And similarly, the high reading value on the as received basis can be also calculated where we can simply multiply these two terms to get the high reading value on the as received basis. And the ash content on weight basis, it can be also determined if the value of this ash content on the dry basis is known.
So, the ash is equal to 1 minus m into ash on. dry basis. So, once we know these two terms we can calculate the ash content.
Similarly, the heating value can be determined using two methods as I mentioned the calorimeter that is called as a bomb calorimeter and also using the ultimate analysis. So, while calculating the heating value using the ultimate analysis this Dulong's formula can be used to calculate the high reading value of the any given fuel once the ultimate analysis of the given fuel is known but there is a condition that the oxygen contained in the fuel or in the feed stock should be less than the 10 percent then using this expression we can calculate the higher heating value as i mentioned earlier as well the higher heating value is one of the important characteristics of fuel as well as the feed material Compared to most fossil fuels, the heating value of biomass based material is low, especially on volume basis because its density is very low and it is a high oxygen containing fuel. So, if you see this table here, it represents the heating value and the bulk density of the source. material. So, in that the bulk density of the wood and the cereal straw if you can see the range of the bulk density it is relatively low compared to that of the coal sample.
Even the heating value is low compared to that of the coal sample because the biomass contains relatively high amount of oxygen in its composition whereas, the oxygen content in the coal sample is relatively low. So, the next in the list is the specific heat and the specific heat is the amount of energy required to raise the fuel from ambient condition to reaction temperature and it is indication of the heat capacity of a substance. And the specific heat is important property of a fuel which is used for the thermodynamic calculation. Now if you see the specific heat versus temperature plot here it shows that the specific heat of the fuel it increases with the temperature and for the wood species for example wood and the wood bark and its mass density if you see it do not have much effect on the specific heat.
However, when this wood is converted into a wood char, then it has much lower specific heat compared to that of its original wood and the wood bark material. And most important property of the solid fuel is the heat of combustion. or we can say the heat of reaction because the heat of reaction is the amount of heat released or absorbed because it depends on the endothermic and the exothermic nature of the reaction with no change in temperature.
Similarly, the heat of combustion is the heat released by substance when it undergoes the complete combustion in the presence of oxygen at standard temperature and the pressure condition. And theoretically we can calculate the heat of combustion of a given reaction by using the difference between the heat of formation of the product and reactant under the specific condition. For example, the combustion of the hydrocarbon in presence of oxygen produces water and CO2 as a product. So, once we know the heat of formation of these compounds, then we can easily calculate the heat of combustion.
So, for example, the heat of combustion as I discussed earlier, it is the difference between the summation of the heat of formation of products that is water and the CO2 minus the heat of formation of the reactant that is hydrocarbon and the oxygen. And once we know these values we can easily calculate the heat of combustion. So, now let us discuss one small example here to calculate the heat of combustion of this specific reaction where the methane is combusted in presence of oxygen to produce water and CO2 as a product.
As the heat of formation of this compound is given here in this table, so the heat of combustion as we discussed earlier, it is the summation of the heat of formation of product compounds that is water and CO2 minus the heat of formation of the reactant. So, here as 2 moles of waters are produced, so 2 into heat of formation of the water plus this is 1 mole of CO2. heat of formation of CO2 once we take the summation of this and minus the summation of heat of formation of methane and heat of formation of the oxygen. So, these values are given here. Once we replace these values in this equation, we will get the final answer in the form of minus 801.7 kilojoule per mole and the negative sign here indicates the exothermic process right as Already we know the combustion is an exothermic process as it releases significant amount of heat.
So, and that is also depicted here in this form of the heat of combustion of the reaction. In case if the sign is positive then it is called as an endothermic process. So, the next point in the Properties is the ultimate analysis. Ultimate analysis it involves the quantitative estimation of carbon, hydrogen, nitrogen, sulfur and oxygen within the fuel or the feed material. So, typically the ultimate analysis is presented in the following way that is on dry basis and dry and ash free basis.
When it is on the dry basis, then it includes carbon, hydrogen, nitrogen, sulfur, oxygen and the ash which accounts to be 100 percent. And when it is dry and ash-free basis, then the ash is neglected and it only presented in the form of carbon, hydrogen, nitrogen, sulfur and oxygen which accounts to be around close to 100 percent. And typically these Ultimate analysis of the fuel is determined at dry and ash free basis. So, normally when we try to estimate the ultimate analysis of any source material, we try to estimate the ultimate analysis on dry and ash free basis. Dry basis means the hydrogen and oxygen in the ultimate analysis does not include the hydrogen and oxygen from the moisture and this ultimate analysis or also known as the elemental analysis can be performed using the elemental analyzer and that is as per the ASTM standard protocol.
This ultimate analysis as I mentioned earlier also it includes the carbon, oxygen, hydrogen, nitrogen and sulfur. In case if we are considering on the dry basis then we have to include the ash as well, but as I mentioned earlier also the ultimate analysis are normally determined on dry and ash free basis so it includes only these elements. Similarly, the proximate analysis it includes the fixed carbon, volatile matter, ash and the moisture contained in the specific raw material as well as the produced product.
If need to be estimated on dry and ash free basis then it includes only the fixed carbon and the volatile matter. If need to be estimated on the dry basis then it includes the ash and as on the received basis. then it includes again the moisture. So, likewise the proximate analysis can be presented based on the following three conditions. So, the ultimate analysis of different fields is tabulated here in the tabular form along with its h by c ratio and the o by c ratio.
And if you see here the h by c and the o by c ratio of biobased material is relatively high compared to that of coal material. However, the sulfur content in the biomaterial is less than that of the coal material and hence the sulfur in the fuel need to be removed before being used in the combustion process because the sulfur in the fuel it contributes to the sulfur dioxide emission. Therefore, to reduce the emission of the sulfur dioxide we can scrub this sulfur dioxide gas using a flue gas desulphurization unit where the limestone is used as a slurry in the scrubber where this sulfur dioxide gas is scrubbed with this limestone slurry and produces calcium sulfate dihydrate that is also known as a gypsum along with the CO2.
So if you see this particular reaction, so for reducing 1 mole of sulfur dioxide, it produces around 1 mole of carbon dioxide and therefore the sulphur must be removed from the fuel before using the feedstock in the combustion process. Apart from the ultimate analysis, the atomic ratio that is h by c ratio and the O by c ratio can also be calculated to rank the fuels. The atomic h by c and the O by c ratios are calculated in the form of molar fractions of the respective element.
That is if you see here this H by C ratio it is the ratio of molar fraction of hydrogen to the molar fraction of the carbon. That is percentage weight of hydrogen divided by its molecular weight and here it is percentage weight of carbon divided by its molecular weight and similarly the O by C ratio can be calculated. So, as we discussed earlier the higher the content of carbon that means the H by C ratio will be lower also the O by C ratio will be lower higher will be the heating value and that is what we have seen in the previous slide where we have seen in the table that the H by C ratio and the O by C ratio of coal is relatively lower than that of the biomass and that is the reason the feedstock or the source material which has higher carbon content ultimately its heating value is relatively higher. So, the high O in the source material consumes the part of the hydrogen in the fuel as well as in the source material to produce H2O and thus high H by C ratio content does not claim that the high gas yield or high heating. For example, if you see here the biomass like leaves has very low heating value because it has very high h by c and the o by c ratio which can be seen here from this graphical representation as well.
If you can see here this biomass which is shown in the green color it has relatively higher h by c ratio and higher o by c ratio. it has a lower heating value. Now if you compare this biomass with the coal that is the anthracite so it has relatively very lower h by c as well as the o by c ratio but the higher heating. So, this way even this h by c ratio as well as the O by c ratio that is also called as the atomic ratios are useful to classify the fuel as well as to rank the fuel. Even the ternary diagram is also useful in ranking the fuel because ternary diagram here it is a graphical representation of elemental like carbon, hydrogen and oxygen concentration of the fuel.
So, the three vertices if you see here these three vertices of the triangle element it represents the carbon, oxygen and the hydrogen and it is nothing but the 100 percent concentration of carbon, hydrogen and the oxygen and the axis opposite to the vertex represents the carbon. 0 concentration of the component at that vertex. So, for example, if you see here this particular axis which is opposite to the vertex that is O.
So, here the concentration of O is 0 percent and points within this particular triangle it represents the. ternary mixture of these three substances. So, for example, here the horizontal axis which is opposite to the edge corner shows the binary mixture of carbon and oxygen and 0 percentage of hydrogen.
So, likewise this ternary diagram it is a useful tool for the classification of the fuel. So, for example, if you see here the coal which is located towards the C vertex and it is closer to the H-C axis suggesting that it is a much richer in carbon and also it is very well known that the high grade coal is much richer in the carbon content. Similarly, this ternary diagram is also useful to illustrate the fuel conversion processes. For example, if you try to see the fast pyrolysis process first, so in case of fast pyrolysis process that is F here, the product moves towards the hydrogen and away from oxygen which implies that the process will produce higher liquid product.
And in case of slow paralysis process, suppose for example, P here which indicates the slow paralysis process, it moves the product towards the carbon through solid char, right? Through formation of the solid char which indicates the formation of a specific product. Likewise, this ternary diagram is also useful tool for the classification of a fuel.
Apart from that the ultimate analysis as we discussed earlier it is also useful for calculating the heating value of a source material as well as the produce fuel. The ultimate analysis of the solid fuel on the dry basis as we discussed earlier which includes carbon, hydrogen, nitrogen, sulfur and the oxygen along with the ash and it accounts to 100 percent. And among these Constituents only carbon, hydrogen and sulfur are only the combustible constituents and thus the heating value of a given fuel it can be approximated from the mass fraction of this constituent that is carbon, hydrogen and sulfur but that is on the dry basis as we have.
assume it is on the dry basis. So, once we know the mass fraction of these constituents, then we can easily calculate the higher heating value of the given fuel. Once we know the mass fraction of carbon, mass fraction of hydrogen and mass fraction of sulphur and their higher heating values, then we can easily calculate the higher heating value of the given fuel. On the similar basis, we can calculate the lower heating value of a given fuel, but for that we need to know the higher heating value of the fuel.
the higher heating value of carbon, hydrogen and sulfur which are given here in the tabular form. And once these values are known along with their mass fraction, we can easily calculate these values. And if you recollect, we discussed the same concept in one of the lecture in the module 1. There we have estimated the higher heating value of a given composition of a fuel.
So, once the composition of the fuel is known then we can easily calculate the high reading value as well as the low reading value of a given fuel. So, this in total completes the ultimate analysis of a source material as well as the fuel. So, with this we will end our lecture here and in the next lecture we will discuss about the remaining properties that is the approximate analysis and the structural composition of a source material as well as the fuel.
Thank you.