[Audio] Hello . Please accept greetings from STARKEN Academy. We are planning to provide basic knowledge related to the Natural Gas distribution business , with more focus on the practical aspects which will equip you with necessary information and knowledge of this business . This course is designed by experts having vast experience of various areas of City Gas Distribution business. The focus of the course material is to provide more realistic learning in a simple way.. 

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[Audio] To begin with , kindly go through the basic hydrocarbon series given in the slide. It covers the chemical formula and name of the hydrocarbons.. 

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Basic Hydrocarbon Series Methane 		:	CH4 Ethane 		:	C2H6		  Propane 		:	C3H8 Butane 		:	C4H10 Pentane	 	:	C5H12 Hexane 		:	C6H14 Heptane 		:	C7H16 Octane		:	C8H18		Petrol & Gasoline    		:	C9H20   		:	C10H22   		:	C12H26		Light & Heavy Diesel   		:	C13H28

[Audio] Now Let's first understand what is natural gas. Natural gas is mixture of gases naturally occurring beneath earth's surface . It is mixture of many gases but predominant are hydro carbon gases. The natural gas used commercially through pipelines is majority of Methane. Natural gas is taken out from earth's sub surface by drilling holes in earth till the source of natural gas. Source of gas can be on land or in deep seas. Modern drill rigs are used to drill holes.. 

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Sand and sitt
rock
Oil and gas deposits

Natural Gas is Naturally Occurring mixture of gaseous hydrocarbons and non-hydrocarbon gases found in porous formation beneath the earth surface. It may or may not be in association with crude petroleum . The main constituent of Natural Gas distributed commercially is Methane – CH4

Natural Gas is taken out from the earth sub-surface by drilling hole in the earth’s top surface on ground or in deep seas using well equipped hi-tech drilling rigs.

[Audio] There are many types of Natural gases known with different terminologies. When gas is present along with liquid hydrocarbons, it is known as associated gas. When the gas is free of liquids, it is known as dry gas. When natural gas is containing harmful gases like hydrogen sulphide , it is known as sour gas. Harmful gases are removed by various techniques like hot and cold flaring or scrubbing etc. Dry gas without harmful gases ready for use is known as sweet gas.. 

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Associated Gas :  Natural gas is accompanied with plant liquids such as propane, normal butane, iso butane, natural gasoline etc . Liquid and Gas are separated through separation process for further commercial utilisation. Dry Gas :  Natural gas is dry and ready for further processing. Sour Gas :  Natural gas is containing harmful gases like sulphides and carbides. This gas can not be processed directly without removing the harmful gases by various techniques like scrubbing , hot flaring ( harmful gases are burnt in flare stack ) , cold flaring ( harmless gases directly discharged through cold stack) etc.  Sweet Gas : Natural gas is free from any unwanted impurities and ready for commercial utilisation in the market.

[Audio] Apart from natural gas , there are many more gases used for various applications by different industries. It is useful to know about some of them. Let's know about them. First is LPG : The next one is Synthetic Gas :
Next is Substitute gas : LNG :
Next is Natural Gas liquids (NGL)
Last one is Dissolved Gases. 

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LPG :  Mixture of Propane and Butane which is liquefied under moderate pressure and temperature but exist as gas at normal pressure and Temperature. Synthetic Gas : Cooking gas produced by processing naphtha and contains CO2 and H2. It possesses properties similar to Natural gas.  Substitute gas : It is a gas which can substitute Natural Gas on demand (interchangeable with Natural Gas). Most of the time it is produced from distillates. LNG : Natural Gas liquefied below -160 0 C for transportation to far places in cryogenic ships. LNG is evaporated to produce Re-gasified LNG (RLNG) for commercial transportation through pipes. Natural Gas liquids (NGL) Heavier hydrocarbons above propane extracted from Natural Gas. It is different from Gasoline produced by crude oil cracking or distillation.  Dissolved Gases Gases are dissolved in liquids for storage in cylinders for various applications e.g. DA gas is used in gas cutting is Acetylene dissolved in acetone .

[Audio] Now let's see important properties of few hydrocarbon gases. You can refer the table given in the slide to study important properties and compare them with each other.
As can be seen in the table , Methane is the lightest of the gases . Since natural gas is predominantly methane , It is lighter than air also which allows it to mix with air very easily and effectively . Combustion efficiency of natural gas is very good compared to other fuels. Being lighter than air makes it safer to use as it disperses away in the atmosphere in case of leakages.. 

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Property Methane Ethane Propane Butane Pentane Formula CH4 C2H6 C3H8 C4H10 C5H12 Mol. Wt(gm/mol) 16 30 44 58 72 Boiling point at 1 atm -161.5 -88.68 -42 -0.5 9.5 Flammability Limit in Air(%) 5 to 15 3 to 12.4 2.2 to 9.5 1.8 to 8.4 1.4 to 7.5 Auto Ignition Temp o C 580 515 480 420 450 Flame Temp o C 1957 1960 1980 1970 1971 Calorific Value (Kcal/m3) 8570 15390 22380 29560 32731 Sp.Gravity ( Relative  to Air ) 0.55 1.04 1.52 2.0 2.48

Note :  Flammability limit is % of gas required in air for flame generation. LPG is mixture of Propane and Butane. It is heavier than Methane , Ethane & air. Hence it settles down on ground in case of leakage.  LPG gives more heat in comparison to Methane and Ethane for same volume burnt.

[Audio] Here , we would like to share some important technical information which will be helpful for some of the topics which we will cover later in this course. It is suggested that you should keep these information in your mind as ready reckoner.. 

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Atmospheric Pressure (1Atm):1.033 Kg/Cm2; 1.0132 Bar , 14.503 PSI 				            10,000 mm Water Column ( mmwc )  STP Condition : 0 deg C Temp. and 1 Atm Pressure NTP Condition : 20 deg C Temp. and 1 Atm Pressure Density of Air : 1.225 Kg/m3 at STP condition Pressure of Natural Gas for Domestic connection : 240 mmwc  CNG Pressure: 220 Bar ( generally ) 1 British Thermal unit ( BTU ) = 0.2522 Kcal/Hr. ( Gas is sold in Million BTU) 1 KW = 860 Kcal/hr Name of Odorant added to NG : Ethyl Mercaptan –C2H5-SH 1 Ton LNG = 1380 m3 NG , 2.47 m3 of LNG

[Audio] After learning about basics of Natural Gas , we move to very important laws based on which gas engineering is developed. These laws are Boyle''s Law , Chaarles Law and universal gas law. The Boyle's law explains the relationship between the Pressure and Volume at constant temperature. It states that if temperature remains constant , volume of gas reduces in proportion to the increase in pressure. Many formulas for designing gas pipeline and other calculations are based on this important theory. Similarly, the Charles law states that if pressure remains constant , the volume of gas increases in proportion to the temperature of gas.. 

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Boyles Law – P x V = Constant Volume occupied by given mass of gas varies inversely with absolute pressure* If temperature remains constant ( * absolute pressure means pressure shown on gauge plus the atmospheric pressure) . It implies that if we increase pressure without changing temperature , same mass of gas can be accommodated in less volume. In gas distribution perspective , by increasing pressure , gas can be accommodated in lower dia. pipes. Similarly , to handle same qty. of gas after reducing the pressure will need larger dia. Pipes.
 Charles Law – V/T = Constant Volume of given mass of gas varies directly as absolute temperature* if pressure remains constant. ( * absolute temperature means temperature shown in gas + 273). In gas distribution perspective , by lowering the temperature at constant pressure , more gas can be accommodated in less volume.
 By combining both laws , we get PV/T = Constant i.e. P1V1/T1 = P2V2/T2

[Audio] Now as we have learnt about Boyle's and Charles gas laws, we pay attention to the universal gas law derived from these two laws and it also includes some other important parameters. You are requested to study the equation given on the slide and understand the relationship between some important parameters. Proper understanding of this equation will be very useful in the subsequent course material we are going to learn .. 

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P x V = n X Z X R x T  Here n = no. of Kilo Moles of gas = Mass of Gas(m)/ molecular wt. of gas (M) Hence , P X V = m x Z x R x T / M Where , P = Pressure in Kg/cm2 V = Volume in m 3 m = Mass in Kg Z = Compressibility Factor R = Gas Constant , 831 J/Kmol- o K T = Temperature in o K  M = Molecular Weight Kg/K Mol

[Audio] Now let's move our attention to one of the very important property of Natural Gas . It is the gas density. Density of Natural gas at standard conditions is the weight of the gas in kg per volume of the gas in meter cube at standard condition. Depending upon the presence of various hydrocarbons in gas , density of the natural gas will vary. Density will be more if proportion of higher hydrocarbons is more. Specific gravity of natural gas is ratio of natural gas density to the air density and is unit less.. 

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Density of Gas is the weight of gas in Kg per cubic meter volume. ( Kg/m3) From the universal gas equation given in previous slide , the density can be calculated as follows :
 Density = m/V = P x M / ( Z X R x T )
 Hence , density of Gas with higher molecular weight is more. For Natural Gas, molecular weight increases when presence of higher hydrocarbon increases.  A typical composition of Natural gas is made up of Methane ( generally > 85 %) , Ethane , Propane , Butane , Pentane , CO2 and Nitrogen with remainder traces of some heavier hydrocarbons.  Molecular weight of mixture of gas is weighted average molecular weight of various constituents of Natural Gas.
 Specific Gravity of Gas = Density of Gas / Air density   Normal Range for Sp. Gravity of Natural Gas is 0.6 to 0.7
 Gas density and specific gravity plays important role in designing of pipelines and metering system of a City Gas Distribution ( CGD ) Company

[Audio] To understand calculation of gas density in a proper way , we will calculate density of a particular quality of natural gas. As you can see in the slide , first we need to calculate molecular weight contribution of each hydro carbon. From that , molecular weight of the gas is derived. Taking this value of molecular weight and values of temperature , pressure and compressibility factor at standard conditions , density is calculated . Density of Air at standard condition is 1.16 Kg per meter cube . By dividing the air density with the air density , specific gravity of the gas is calculated.. 

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Component Formula Mol. Wt. % Presence Total Methane CH4 (12+4)16 86.38 13.820 Ethane C2H6 30 06.545 01.963 Propane C3H8 44 02.500 01.100 Butane C4H10 58 00.550 00.320 Nitrogen N2 (14*2)28 00.107 00.030 Carbon Dioxide CO2 (12+32)44 03.816 01.680 Pentane C5H12 72 00.006 00.045 Hexane C6H14 84 00.003 00.025 Total Mol. Wt.


 18.990

Calculate gas density and Sp. Gravity at atm. Pressure and 30 o C temp for following gas:

Atm. Pr.=1.103*104 ,   Mol wt=18.99 , Temp=(273+30) , R=831,Z=1
 Density = (1.103*104*18.99*1)/(303*831) = 0.764 Kg/m3
 Sp. Gravity = 0.764/1.16 = 0.66

[Audio] Now we will know some important points related to the next very important aspect of gas engineering and that is combustion of Natural Gas. Please look at the diagram in the slide. For combustion to take place , fuel , oxygen and source of heat is required. When these three elements are shown in form of a triangle, it is known as combustion triangle. Oxygen is introduced in form of air as air contains 21 % of oxygen by weight. For combustion to take place , these three elements in right proportion are required.
The ratio of amount of air and fuel ,at which the fuel burns completely and no shortage of oxygen is there for combustion , is known as stoichiometric ratio. When fuel and air mixture burns , Carbon Dioxide and water vapours are generated. Insufficient air can produce harmful gases like carbon monoxide and nitrogen oxide.. 

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The ratio of amount of air and fuel ,at which the fuel burns completely and no shortage of oxygen is there for combustion , is known as stoichiometric ratio.   Fuel + Air  -> CO2 + H2O+N2  If Sufficient Air is not provide, harmful gases like CO and NO are generated.

To initiate spontaneous combustion , we require sufficient amount of Fuel , Oxygen and Heat. Heat is introduced in form of flame / spark .Oxygen is provided by introducing air and mixed with the fuel.  ( Oxygen is available in air @ 21 % by weight and 23 % by volume). For a perfect combustion to take place , right proportion of all 3 elements has to be ensured.

[Audio] To understand the concept of stoichiometric mixture for methane , we have one example and its calculation in the slide. Air is represented by 21% oxygen and 79% nitrogen on weight basis. Weight of air required for burning methane is calculated and from that the Air to Fuel ratio by volume is also calculated.
Please go through the example carefully and do your own calculation of Ethane for practice.. 

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Calculation of Stoichiometric Ratio for Methane

CH4         +	(0.21 O2+0.79 N2) = CO2 + H20 + N2 Methane			(Air)
 CH4  + ( O2 + 3.76 N2 ) = CO2 + H20 + N2 CH4  + 2( O2 + 3.76 N2 ) = CO2 + 2H20 + 7.52N2 Methane Mol. Wt is ( 12+4 ) 16 , for O2 it is 32 and N2  it is 28   Hence , For Complete combustion ,16 Fuel Mass require 274.56 Air Mass
 So , 1 Kg Methane require min. 17.16 Kg of Air for complete burning of fuel
 In volumetric terms Air / Fuel Ration (AFR) can be calculated using universal gas equation for Air and Methane.   AFR  = Stoichiometric Ratio ( weight ) X (R air / R fuel) , where R air = 831/28.84=28.81 R methane = 831/16 = 51.93 . AFR = 17.16 X  28.81/51.93 = 9.51 , hence , to burn 1 m3 of methane , 9.51 m3 of air is needed for perfect combustion . In practical condition , air is supplied above AFR to ensure that sufficient air molecules are available for proper mixing with gas molecules to form stoichiometric mixture.

[Audio] Now we will learn about the calorific value of natural gas. This is one of the most important properties of the natural gas and used to estimate natural gas requirements for various applications. Calorific value for any gas is basically the units of heat energy liberated by complete combustion of gas at standard conditions. It is generally expressed in Kilo Calorie per meter cube. There are two types of calorific values. One is net calorific value – NCV and the other is gross calorific value – GCV as explained in this slide. Gross Calorific Value for Natural Gas is generally 5 to 10 % higher as per its composition. Net calorific value is considered for energy calculations .. 

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Calorific value for any gas is basically the units of heat energy liberated by complete combustion of gas at standard conditions. It is generally expressed in Kcal/M3 .  As we have seen earlier, H2O is the product of combustion for Hydro Carbons. It is present in the product of combustion (Exhaust) in form of water vapours. This vapour consumes some energy for evaporation which reduces the actual heat available for utilisation.  The calorific value of the gas when water vapour is in gaseous stage is known as Net Calorific Value ( NCV ) . When this water vapour condenses to liquid state, it liberate heat of condensation , which increases the heat content . The calorific value , when the water vapours are in condensed state , is known as Gross Calorific Value ( GCV ).  For natural gas , depending upon the gas composition (gas source), GCV is higher than NCV by 5 to 10 %. When we consider heat available for utilisation for any application, NCV shall be considered.

[Audio] In this section, we will learn basic things about the gas burners. Gas burner is a device which facilitates combustion by making proper mixture of fuel and air and then releasing the mixture correctly to the source of ignition to ensure that heat of combustion is available for utilisation. When air is mixed with the natural gas before combustion is known as primary gas. The air which is available for burning in the combustion region is known as secondary air. Air is mixed with gas naturally or it is provided by fan or blower in case of higher capacity burners. Quantity of gas required to activate stoichiometric combustion is ensured by controlling the gas pressure.. 

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What is Gas Burner ?  Gas burner is a device which facilitate combustion by making proper mixture of fuel and air and then releasing the mixture correctly to the source of ignition to ensure that heat of combustion is available for utilisation.  Air required for proper combustion when introduced and mixed with gas is known as Primary Air and the Air which is made available in the combustion region near burner is known as secondary air. Secondary air is generally air available in the atmosphere.  The primary air can be sucked from the atmosphere or introduced by blower or fan.  Source of Ignition can be necked flame or Sparks. In industrial burners , ignition or necked flames are achieved through special mechanism.  Depending upon the situation , pressure of the Gas is controlled to ensure that required quantity of gas is injected to achieve stoichiometric combustion.

[Audio] Now we will describe key components of a gas burner. This will help you to understand gas burners more closely. As you can see in the drawing , the main components of a gas burner are Gas Jet , hole for primary aeration , mixing tube , burner ports and gas coke or gas valve. Gas jet ensures proper release of gas to mixing tube through hole of calculated diameter. The primary hole drilled in the mixing tube allows estimated quantity of primary air to enter in the mixing tube. Mixing tube is a long tube which is designed to ensure proper mixing of fuel and air. Burner ports are the ports drilled in the burner through which mixture of gas and air is released to combustion region. Gas Coke or gas valve is the device which controls the gas quantity.. 

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Gas Jet This is the part with calculated hole diameter through which gas is injected in the burner. Hole for Primary Air It is a hole of calculated dia drilled in the gas mixing tube to introduce required quantity of Primary Air. Mixing Tube It is a tubular part of the burner, designed to ensure proper mixing of Gas and the Primary air before the mixture is released for burning.  Burner ports These are the holes drilled in top most part of a burner through which mixture of gas and primary air is released for ignition. Gas cock / valve It is provided at the gas inlet to the burner for controlling the quantity of the gas for required heat output and combustion quality.

[Audio] In this slide , you can see three types of burners classified on the basis of method of aeration. As shown in the figure , the first burner is fully aerated burner where total quantity of air is provided with the gas and there is no secondary air. The next burner is partially aerated burner where total air is provided by both primary and the secondary air. The third type of burner is non-aerated burner , where total quantity of air is provided as secondary air. There is no primary air mixed with the gas. Depending upon the type of aeration , we get the flame characteristics as shown in the figures.. 

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Based on the method of achieving stoichiometric mixture of air and gas ,  burners are classified basically as Fully Aerated , Partially Aerated and Non Aerated burners .

Partially Aerated : Primary Air mixed with gas.  Partial  secondary Air. Long steady flame.

Fully Aerated : Total Air mixed with gas.  No secondary Air. Short steady flame.

Non Aerated : No Air mixed with gas.  Total secondary Air. Long irregular flame.

[Audio] We will now learn about the two basic parameters of gas burners which ultimately determines the burner performance. The first parameter is the primary aeration. Primary aeration determines the flame characteristics. The other parameter is port loading. It is the total heat energy provided divided by the total port area. To get good flame characteristics , port loading shall be maintained at around 20,000(BTU/Hr)/Sq.inch or 7.78 Kilo Calorie per hour pr square millimetre. More or less than required primary aeration or port loading results in flame lifting , flash back , yellow tipping or improper ignition.. 

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Basic Parameters for NG Burner Performance

Primary Aeration Primary aeration determines the amount of spark energy required for setting the combustion and flame characteristics. Providing more primary air above desired limit result in higher spark energy , flame lifting and yellow tipping of flame.  Port Loading Port loading is defined as the heat energy Input divided by port area. It is expressed in terms of  (BTU/Hr) / Sq.inch .  As a thumb rule for burner designing , port loading is considered as 20,000  to get steady blue flame without lifting. When converted , it is 7.78 (Kcal/Hr)/mm2 . Depending upon the combination of Port Loading and Primary Air % , the burner flame characteristics will change and vary between  Lifting , Yellow Tipping , Stable flame and Flashback.  Port loading below allowable zone result in flashback and above the zone results in flame lifting or yellow tipping.

[Audio] To understand the primary calculations for simple burner design, an illustration is given in this slide. This will make you all understand basics of burner design , though, complex burner designs involve many more calculations. Kindly go through the illustration and try to make calculations yourself. It shows practical aspects of deciding nos. of ports of a burner.. 

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Example of Port calculation for NG pipe burner

Find out number of rows for a NG Pipe burner for NG requirement of 5m3/hr. for these parameters :-  Port Hole dia (d) = 6mm , pitch = 2d , NG NCV = 8800 Kcal/m3 , available length of ports =  600 mm
 Solution
 Heat Input = NG Flow x NG NCV = 5 m3/hr X 8800 Kcal/m3 = 44,000 Kcal/Hr
 Port Area = Heat input/Port loading = 44,000/7.78 = 5655.52mm2    
 Nos. of holes = Total area/area of 1 hole = 5655.52/((∏/4) X (6) 2 ) = 200
 Holes in one row = Length / pitch = 600/( 2 x 6) = 50
 Nos. of Rows = nos. of holes / holes in each row = 200/50 = 4

[Audio] Now we will go through varieties of gas burners. 4 types of burners are described in this slide. The first type of burner is the ring type of burner , generally used in house holds and restaurants. The next one is the multi jet multi port burners used in commercial application. This type of burners can give high heat output with lower gas pressure. The next one is the simplest kind of gas burner known as Bunsen burne with single jet and single port having low heat output and used by jewellers and researchers. The last type is high capacity burners used in industrial applications with very high requirement of heat. They are generally equipped with control system and arrangement for injecting higher quantities of primary air using blowers.. 

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Single Jet , Multiple port , Single flame ring burners. Most of the domestic  and commercial appliances use this type f burners . In 2 burners domestic hotplate , bigger burner general heat output is 2000 Kcal/hr and that of smaller burner is 1500 Kcal/hr.

Multiple jet , multiple tube , multiple flame commercial burners . Depending upon the heat output required , jets are selected and accordingly the diameter of the  mounting is decided . These types of burners give good heat even at lower gas pressure.

Single jet , single port (tube) , Single flame burners. These are one of the simplest burners with low heat output. These types of burners are popular in jewellery making, laboratories and research work.

These are generally single jet (nozzle ), Single port, single flame burners equipped to handle larger qty. of gas with modern controls for  controlling flame characteristics and heat output. Variety of burners are available for equipments like boilers , furnaces , dryers , foundry , forging press etc.

[Audio] Till now we have learnt about the natural gas and its combustion. Before ending this module of the course , we would like to describe the basic gas value chain. As you can see , the gas value chain has three streams. The first one is associated with gas production known as upstream. Depending upon the gas field characteristics , such facilities can contin gas conditioning and compression for further commercial dealings. The next stream is called midstream which either involves gas processing and transportation by pipelines to the next commercial sale or liquefaction to make LNG and transportation by cryogenic ships. The gas transported by pipelines or in form of LNG are further filtered or evaporated for commercial sale and this stream is known as downstream.. 

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Discovery Exploration Processing Compression

Direct Sale – High Volume – Power, Fertiliser ,Metal , Glass etc.

Sale to CGD – Domestic , Commercial , Industrial , CNG

[Audio] Before we end this first module of the entire course , we would like to make you aware of the versatility of Natural Gas as fuel by describing its variety of usages in different sectors. You can go through the list of applications given in the slide and make your own list of natural gas usages which is not covered in this list.
We think that by now you must have learnt the basics of Natural gas and its combustion. We will cover various areas of the City Gas Distribution ( part of downstream ) business in more depth in the coming modules of this course. The coming modules will give you required knowledge of the city gas distribution business in a simple , practical and effective way. So let's meet in the next modulewhich will be on network planning and design.. 

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Natural Gas as Feedstock :       Fertilisers , Petrochemicals , Pharma etc. Power Generation :      Gas turbines , Co-Generation – Power + Heat ,       Tri- Generation – Power + Heat + Cooling Domestic : Cooking & Water Heating Commercial :      Restaurants ,  Very small scale industries, Malls ,     shopping     complexes Industries :       Textiles , pharma, chemicals , pints , metal processing , ceramics , glass,      paper , plastics etc.  Compressed Natural Gas ( CNG ) : Car , Buses , Auto Rickshaw

Module 1

Please accept greetings from STARKEN Academy

We are planning to provide basic knowledge related to the Natural Gas distribution business , with more focus on the practical aspects which will equip you with necessary information and knowledge of this business

This course is designed by experts having vast experience of various areas of City Gas Distribution business

The focus of the course material is to provide more realistic learning in  a simple way.

avatar

To begin with , kindly go through the basic hydrocarbon series given in the slide

It covers the chemical formula and name of the hydrocarbons.

Now Let's first understand what is natural gas

Natural gas is mixture of gases naturally occurring beneath earth's surface

It is mixture of many gases but predominant are hydro carbon gases

The natural gas used commercially through pipelines is majority of Methane

Natural gas is taken out from earth's sub surface by drilling holes in earth till the source of natural gas

Source of gas can be on land or in deep seas

Modern drill rigs are used to drill holes.

There are many types of Natural gases known with different terminologies

When gas is present along with liquid hydrocarbons, it is known as associated gas

When the gas is free of liquids, it is known as dry gas

When natural gas is containing harmful gases like hydrogen sulphide , it is known as sour gas

Harmful gases are removed by various techniques like hot and cold flaring or scrubbing et cetera

Dry gas without harmful gases ready for use is known as sweet gas.

Apart from natural gas , there are many more gases used for various applications by different industries

Now let's see important properties of few hydrocarbon gases

You can refer the table given in the slide to study important properties and compare them with each other.

As can be seen in the table , Methane is the lightest of the gases

Since natural gas is predominantly methane , It is lighter than air also which allows it to mix with air very easily and effectively

Combustion efficiency of natural gas is very good compared to other fuels

Being lighter than air makes it safer to use as it disperses away in the atmosphere in case of leakages.

Here , we would like to share some important technical information which will be helpful for some of the topics which we will cover later in this course

It is suggested that you should keep these information in your mind as ready reckoner.

After learning about basics of Natural Gas , we move to very important laws based on which gas engineering is developed

These laws are Boyle''s Law , Chaarles Law and universal gas law

The Boyle's law explains the relationship between the Pressure and Volume at constant temperature

It states that if temperature remains constant , volume of gas reduces in proportion to the increase in pressure

Many formulas for designing gas pipeline and other calculations are based on this important theory

Similarly, the Charles law states that if pressure remains constant , the volume of gas increases in proportion to the temperature of gas.

Now as we have learnt about Boyle's and Charles gas laws, we pay attention to the universal gas law derived from these two laws and it also includes some other important parameters

You are requested to study the equation given on the slide and understand the relationship between some important parameters

Proper understanding of this equation will be very useful in the subsequent course material we are going to learn .

Now let's move our attention to one of the very important property of Natural Gas

Density of Natural gas at standard conditions is the weight of the gas in kg per volume of the gas in meter cube at standard condition

Depending upon the presence of various hydrocarbons in gas , density of the natural gas will vary

Density will be more if proportion of higher hydrocarbons is more

Specific gravity of natural gas is ratio of natural gas density to the air density and is unit less.

To understand calculation of gas density in a proper way , we will calculate density of a particular quality of natural gas

As you can see in the slide , first we need to calculate molecular weight contribution of each hydro carbon

From that , molecular weight of the gas is derived

Taking this value of molecular weight and values of temperature , pressure and compressibility factor at standard conditions , density is calculated

Density of Air at standard condition is 1.16 Kg per meter cube

By dividing the air density with the air density , specific gravity of the gas is calculated.

Now we will know some important points related to the next  very important aspect of gas engineering and that is combustion of Natural Gas

For combustion to take place , fuel , oxygen and source of heat is required

When these three elements are shown in form of a triangle, it is known as combustion triangle

Oxygen is introduced in form of air as air contains 21 % of oxygen by weight

For combustion to take place , these three elements in right proportion are required.

The ratio of amount of air and fuel ,at which the fuel burns completely and no shortage of oxygen is there for combustion , is known as stoichiometric ratio

When fuel and air mixture burns , Carbon Dioxide and water vapours are generated

Insufficient air can produce harmful gases like carbon monoxide and nitrogen oxide.

To understand the concept of stoichiometric mixture for methane , we have one example and its calculation in the slide

Air is represented by 21% oxygen and 79% nitrogen on weight basis

Weight of air required for burning methane is calculated and from that the Air to Fuel ratio by volume is also calculated.

Please go through the example carefully and do your own calculation of Ethane for practice.

Now we will learn about the calorific value of natural gas

This is one of the most important properties of the natural gas and used to estimate natural gas requirements for various applications

Calorific value for any gas is basically the units of heat energy liberated by complete combustion of gas at standard conditions

It is generally expressed in Kilo Calorie per meter cube

One is net calorific value – NCV and the other is gross calorific value – GCV as explained in this slide

Gross Calorific Value for Natural Gas is generally 5 to 10 % higher as per its composition

Net calorific value is considered for energy calculations .

In this section, we will learn basic things about the gas burners

Gas burner is a device which facilitates combustion by making proper mixture of fuel and air and then releasing the mixture correctly to the source of ignition to ensure that heat of combustion is available for utilisation

When air is mixed with the natural gas before combustion is known as primary gas

The air which is available for burning in the combustion region is known as secondary air

Air is mixed with gas naturally or it is provided by fan or blower in case of higher capacity burners

Quantity of gas required to activate stoichiometric combustion is ensured by controlling the gas pressure.

Now we will describe key components of a gas burner

This will help you to understand gas burners more closely

As you can see in the drawing , the main components of a gas burner are Gas Jet , hole for primary aeration , mixing tube , burner ports and gas coke or gas valve

Gas jet ensures proper release of gas to mixing tube through hole of calculated diameter

The primary hole drilled in the mixing tube allows estimated quantity of primary air to enter in the mixing tube

Mixing tube is a long tube which is designed to ensure proper mixing of fuel and air

Burner ports are the ports drilled in the burner through which mixture of gas and air is released to combustion region

Gas Coke or gas valve is the device which controls the gas quantity.

In this slide , you can see three types of burners classified on the basis of method of aeration

As shown in the figure , the first burner is fully aerated burner where total quantity of air is provided with the gas and there is no secondary air

The next burner is partially aerated burner where total air is provided by both primary and the secondary air

The third type of burner is non-aerated burner , where total quantity of air is provided as secondary air

There is no primary air mixed with the gas

Depending upon the type of aeration , we get the flame characteristics as shown in the figures.

We will now learn about the two basic parameters of gas burners which ultimately determines the burner performance

The first parameter is the primary aeration

Primary aeration determines the flame characteristics

It is the total heat energy provided divided by the total port area

To get good flame characteristics , port loading shall be maintained at around 20,000(BTU/Hr)/Sq.inch  or 7.78 Kilo Calorie per hour pr square millimetre

More or less than required primary aeration or port loading results in flame lifting , flash back , yellow tipping or improper ignition.

To understand the primary calculations for simple burner design, an illustration is given in this slide

This will make you all understand basics of burner design , though, complex burner designs involve many more calculations

Kindly go through the illustration and try to make calculations yourself

It shows practical aspects of deciding nos

Now we will go through varieties of gas burners

4 types of burners are described in this slide

The first type of burner is the ring type of burner , generally used in house holds and restaurants

The next one is the multi jet multi port burners used in commercial application

This type of burners can give high heat output with lower gas pressure

The next one is the simplest kind of gas burner known as Bunsen burne with single jet and single  port having low heat output and used by jewellers and researchers

The last type is high capacity burners used in industrial applications with very high requirement of heat

They are generally equipped with control system and arrangement for injecting higher quantities of primary air using blowers.

Till now we have learnt about the natural gas and its combustion

Before ending this module of the course , we would like to describe the basic gas value chain

As you can see , the gas value chain has three streams

The first one is associated with gas production known as upstream

Depending upon the gas field characteristics , such facilities can contin gas conditioning and compression for further commercial dealings

The next stream is called midstream which either involves gas processing and transportation by pipelines to the next commercial sale or liquefaction to make LNG and transportation by cryogenic ships

The gas transported by pipelines or in form of LNG are further filtered or evaporated for commercial sale and this stream is known as downstream.

Before we end this first module of the entire course , we would like to make you aware of the versatility of Natural Gas as fuel by describing its variety of usages in different sectors

You can go through the list of applications given in the slide and make your own list of natural gas usages which is not covered in this list.

We think that by now you must have learnt the basics of Natural gas and its combustion

We will cover various areas of the City Gas Distribution ( part of downstream ) business in more depth in the coming modules of this course

The coming modules will give you required knowledge of the city gas distribution business in a simple , practical and effective way