2What is CNG ?CNG is natural gas compressed to a pressure of Kg/cm² (g).Why CNG is used in vehicles instead of natural gas?Due to its low density natural gas is compressed to enhance the vehicle onboard storage capacity. Thus, the compressed form of natural gas is used as a fuel for transportation purposes.What is composition of Natural gas?Natural gas is a mixture of hydrocarbon. Hydrocarbon is an organic compound containing only carbon and hydrogen atoms. Typically gas compositions are as follows:Methane %Ethane %Propane %Butane %Nitrogen %
3Natural Gas is reserved inside earth. To explorer natural gas reserved inside earthGeographical survey is carried out to find out the exact location of gas reservoir by basic seismology.Well is being drilled after interpretations of various observations.Well is casings provided for strengthening of well hole, evaluating temperature and pressure of formation to allow the flow of natural gas out of well.Well is completed to make it ready to flow gas in various techniques.After completion of well gas may be lifted in its own pressure or with aid of some other lifting equipment.
4These lifted gas is processed to make it pure These lifted gas is processed to make it pure. Usually it involves four main process to remove impurities.Oil and condensate removalWater removalSeparation of natural gas liquidsSulfur and Carbon Dioxide removal.
5What is liquefied natural gas? Liquefied natural gas is the liquid form of natural gas.Taken out of the ground as natural gas, it becomes a liquid by being chilled to -162 degrees Celsius.The cooling process reduces the volume of natural gas by more than 600 times, making it easier and safer to store and transport.At regassification terminals,the liquefied natural gas is warmed until it returns to its original gas state. This natural gas can then be used for cooking, home heating and generating electrical power, among other uses.
6Where does liquefied natural gas come from? Liquefied natural gas is predominantly imported from Trinidad and Tobago, Algeria. Indonesia, Malaysia, and Qatar.The 12 countries that currently export liquefied natural gas have approximately 28% of world natural gas reserves. Russia, Iran, and Qatar have natural gas reserves representing more than 50 percent of the world total.
7How is liquefied natural gas transported? Liquefied natural gas is transported in double-hulled ships that are specifically designed to handle the liquefied gas at -162 degrees Celsius. These ships are designed with many safety features to ensure safe marine transportation of the liquefied natural gas.Liquefied natural gas is transported in either a MOSS tanker or a membrane tanker.
8How does liquefied natural gas become the natural gas we use? On arrival at the LNG regassifictaion facility, liquefied natural gas will be pumped at atmospheric pressure to the full containment storage tanks. It will then pumped through a vaporizer where it will be warmed in a controlled environment.By passing through the vaporizer and slowly warming up, liquefied natural gas returns to its gaseous state. The vapourized gas is then regulated for pressure and enters the pipeline as natural gas.Where are LNG degasification facilities located in India?Currently there are two LNG terminals in India. One in Dahej and another in Hazira.
9Why CNG ?The calorific value of the natural gas is around 8500 Kcal/SCM.Real relative density of gas is kg/m3CNG is non-toxic and free from Lead and Benzene, and emits less pollutantsNatural gas is free from adulteration and theft.CNG-powered vehicles have less maintenance cost as compared with other fuel-powered vehicles.Increased life of oils. Another practical advantage observed is the increased life of lubricating oils, as CNG does not contaminate and dilute the crankcase oil.CNG mixes easily and evenly in air being a gaseous fuel.High auto-ignition temperature. CNG is less likely to auto-ignite on hot surfaces, since it has a high auto-ignition temperature (540 degrees centigrade) and a narrow range (5%-15%) of inflammability.
11Major Plant and Equipments : The mother station has been designed to cater to max. of 50,000 SCMD gas. Following major facilities / equipments has been considered at the mother station :Odourising Unit.1200 SCM/Hr capacity Electric Motor driven Compressor – 2 Nos. ( one as the main compressor and second as the stand by compressor ).Static Cascades of 4500 LitresTwo Nos of Car dispenserOne no of Bus dispenser..Standby DG set of 380 KVA capacity.Facility to fill mobile cascades for daughter booster stations
12Gas Odourizing UnitThe unit consists of following parts:Two nos of odourant tank.One pneumatic pump panelElectronic Control unit.
13Electrical Motor Driven CNG Compressor Typical parameters are as follows:Flow rate: 1200 SCM/HNo of cylinders : 2Inlet pressure : 45 barInlet temperature: 30 deg CIst stage discharge press: barIst stage discharge temp: 95 deg C2nd stage discharge press: 255 bar2nd stage discharge temp: deg C
14Description of Cascade (75 liters CNG cylinders): Each Cascade consists of 60 Cylinder of 75 liters Water Capacity in 3 Bank configuration (Low Pressure Bank 30 cylinders . Medium Pressure Bank 18 Cylinders and High Pressure Bank 12 Cylinders) , thus, Cascade capacity will be 4500 liters and each Bank flow will be 100 kg/min.The cascade is provided with NRV (non return valve) for one line as well as three line filling and three line sequential dispensing.
15Cascade is divided in to three banks like : Low pressure bank WORKING OF THREE BANK CASCADECascade is divided in to three banks like :Low pressure bankMedium pressure bank andHigh pressure bankThe storage pressure in all three banks is same i.e. 250 bar.When the vehicle with a pressure of 50 bar arrives for refilling, initially, the gas is drawn from low pressure bank, which has a maximum number of cylinders.At this stage medium and high pressure banks are closed.Once the pressure in LP bank is reduced to below 200 bar (the required pressure of CNG vehicle) MP bank is operated and the gas from the same is drawn to top up the vehicle cylinder up to 200 bar.Similarly, when the pressure in MP bank is reduced to below 200 bar the HP bank is operated in addition to MP bank.This system is suitable for Automatic dispensers.
164) Why gas is filled at 250 bar? In the vehicle the gas is to be filled at 200 bar. So to create the pressure difference the gas is filled at 250 bar in the cascade.5) Why 3 bank system is used instead of single bank system?In the single bank system only 20% of the total volume of the gas can be used in the ideal conditions whereas with 3 bank system we can get double the gas output at one filling.6) Why only 3 banks? Why not 4 or 5 banks?The dispensing system used to fill the gas in the automobile is based on the 3 bank system that’s why we are using 3 bank system.Why single cylinder is not used for storage of CNG ?In design calculation of high pressure vessel the thickness of vessel is proportional to diameter of vessel. So to keep the cylinder thickness less diameter of cylinder also kept less.
17Filling in Mobile Cascade: Following steps is followed to fill CNG in Mobile Cascade in Mother Station.Place the wheel choke to stop movement of LCV during filling.Pressure in High Bank, Medium bank, Low Bank of mobile cascade to note down.Temperature of mobile cascade to note down.Flexible hose to be connected to mobile cascade by quick coupling.LCV is grounded.Filling to be started.High, Medium, Low bank of mobile cascade is to be filled up upto 240kg/cm2
18The valve connected to the mobile cascade and connected to filling point to be closed. The quantity of gas entrapped between these two valves in flexible hose is to be vented out.Hose to be disconnected.Pressure and temperature is to be note down in LCV Log Book.Now the LCV is ready to go to Daughter Station.
19Points to remember during filing CNG in vehicles: The engine of vehicle should be stopped.Loud speaker if any is in the vehicle, should be turn off.There should be no passenger in the vehicle during filling CNG
20Daughter Station:Following facilities are available in Daughter Stations:1 No of Booster Compressor1 no of 2200 liter stationary cascade for storage of CNG1 no of Dispenser with two hoses.
21Daughter Station:Following facilities are available in Daughter Stations:1 No of Booster Compressor1 no of 2200 liter stationary cascade for storage of CNG1 no of Dispenser with two hoses.storage only, as one of the two set-points can be the vehicle filling pressure in direct-fill fashion. The second set point can be useful to storage pressure.
22Auxiliary attachments: Closed Loop water cooling system: To cool down the temperature of Hydraulic oil and gas inside cylinder.Sound Proof Canopy: To ensure sound level outside canopy max.65dBA.Electrical & Power Control Panel (Non Flame Proof)U V Detector : To shut off all the valves and stop the compressor if there is any flame inside compressor canopy.LEL Detector : To shut off all the valves and stop the compressor if LEL is 70%DCP fire extinguisher:CO2 Flooding System : To dump CO2 automatically on detection of flame inside the enclousure. CO2 flooding system is properly inter locked with the booster with manual selector switch for both the cylinders.
23How Safe are Natural Gas Vehicles? Natural gas is an environmentally clean, plentiful, low-cost, domestically-produced fuel for motor vehicles. But is it a safe fuel?As with all vehicle fuels, natural gas can be used safely if simple, common sense procedures are followed. In fact, natural gas has safety advantages compared to gasoline and diesel:Natural gas vehicles have an excellent safety record for two primary reasons: the properties of the fuel itself and the integrity of the natural gas vehicle and its fuel delivery system.Natural gas has a very limited range of flammability - it will not burn in concentrations below about 5 percent or above about 15 percent when mixed with air. Gasoline and diesel burn at much lower concentrations and ignite at lower temperatures. Although it takes very little energy to ignite a flammable mixture of air and natural gas, gasoline, or diesel, natural gas burns at a somewhat lower temperature
33Unloading of LCV (Mobile cascade): When the LCV reports at daughter station, check the vehicle log book.Check that the entry at Mother station and be sure that the LCV was actually dispatched for the same station. If the entry is for any other station, please confirm with mother station before proceeding with unloading.Enter the time of reporting, pressure and temperature of all three banks of cascade in the log book.Place the LCV in gear, put wheel chokes and take the key of LCV from the driver.Connect the earthing clip to body of cascade.Connect the hose to the Quick connect coupling of ‘High Bank” of the mobile cascade.Pull the hose slightly and check that the connection has been properly made.Ensure that the vent on the line is closed.
34Slowly open the isolation valve on the tubing manifold Slowly open the isolation valve on the tubing manifold . If any leakage is observed, close the valve immediately.Else, slowly open the valve on the high bank of the cascade fully.Gas will directly flow to the dispenser and dispensing to vehicles can be done.Ensure that the isolation valves of High Bank and Low bank of Stationery cascade are open and Valve on Medium Bank is closed.When the pressure goes below 200 bar, instruct booster compressor operator to start compressor.Unload the gas in mobile cascade till a pressure of 50 bar is reached, at which the compressor will trip automatically.Close the isolation valves on the high bank of the mobile cascade and on the tube manifold.Vent the hose contents by opening the venting valve. Once the gas is vented, close the vent valve and open it again to ensure that the gas is fully vented.Remove the hose from the quick connect coupling of the cascade.
35Enter closing pressure and temperature readings and time of releasing LCV in log book. Remove earthing clip, wheel chokes and return vehicle ignition key of LCV to driver and ask him to report to mother station.Observe pressure in high bank of stationery cascade. If the high bank pressure goes below 180 bar ,Close the valve on “Low bank “ of stationery cascade and open the valve on the “Medium bank”.Instruct compressor operator to operate compressor to boost high bank pressure by taking suction from medium(and low) bank .Stop the compressor if the pressure of high bank reaches 250 bar(the compressor stops automatically). Restart compressor if pressure in high bank falls below 180 bar and repeat procedure till the pressure in medium bank falls to 50 bar .If any LCV reports , stop the compressor immediately.Close the valve on “medium bank “ of stationery cascade and open the valve on the “Low bank”.Unload LCV as described above.
36Safety Instructions:All operators should use helmets and safety shoes.LCV operator should wear hand gloves.Safety procedures with respect to LCV like engine switched off, taking vehicle ignition key from driver, earthing clip and wheel chokes should be strictly followed before starting unloading.Steps 20 to 24 should not be carried out only if high bank pressure in stationary cascade drops below 180 bar and there is no other LCV connected or waiting to be unloaded. Else connect the next LCV and star unloading procedure as soon as it arrives.
37If any leakage is observed from any where , please stop compressor , close all valves and inform Mother station .If safety relief valve of stationery of mobile cascade operates discharging gas , stop al operations. Note the starting time and high bank pressure of the cascade and inform about the same to Mother station.Do not allow anybody to go near the area (atleast within 3 metres) till the vent stops.Note down the stop time and pressure of high bank of cascade after the venting has stopped.
38Dispensing:Vehicle should be stopped at a distance right for fixing of hose.There should be no passenger in the vehicle during refueling of the vehicle.The vehicle engine should be switched off and should be in gear.See the kit manufacturers’ compliance plate fixed on the vehicle for proper validity.Check the O rings of the refueling probe visually for any cuts/damages.Insert the probe into the valve of the vehicle and make sure that the connection is ok.Open 3 way valve of nozzle and check that there is no leakage. If leakage is observed, close valve immediately.If there is no leakage, press ‘Off” and then ‘ON’ on the dispenser. The gas dispensing starts.
39Once the vehicle’s tank is filled upto the required pressure , the filling cuts of automatically. If the driver wants a certain amount or qty of gas , press “Off” button atleast 200 gms/ Rs. 5 before the quantity of gas/amount.Press “Off” button on the dispenser.Vent the nozzle contents by operating the 3 way valve on the nozzle.Remove the nozzle and place the same on the cradle or proceed to fill the next vehicle.Collect the amount from the vehicle driver as displayed on the dispenser diplay.