LNG: Pros and cons

Natural gas is an essential energy source and people have various confusions regarding its derivatives and related products

It is indeed a great relieving news that Bangladesh has entered to a new era of imported LNG since for the last decade or so, Bangladesh was in the grip of acute energy crisis to meet the domestic industrial need and national prosperity in the industrial sector proved a great threat due to drastic short-fall in domestic natural gas supply owing to rapid depletion of natural gas wells in the country.

According to the published information released so far that Moheshkhali floating LNG terminal will include a floating storage and regasification unit (FSRU), a subsea buoy system and a subsea pipeline, which will connect the terminal to an on shore pipeline system. The FSRU is expected to have a storage capacity of 138,000 Nm3 of LNG and a regasification capacity of 500 Mcf/day. The terminal’s offshore subsea buoy system may be used mooring and will also serve as a conduit to transfer natural gas onshore.

It should be borne in mind that the Moheskhali site is unfortunately situated under the natural calamity area as such adequate safety precaution should be taken to face any natural cyclonic calamity and possible tidal bore, effect of Tsunami etc. The Equipment, Piping loop as well as supply line should be adequately protected as discussed in this article below, especially from the possibility of hydrate formation and impurities contaminants and its consequences. All safety protections must be ensured as per the environmental studies and necessary precautions should be incorporated and strictly monitored.

Natural Gas is an essential energy source and people have various confusions regarding its derivatives and related products commonly named as commercial products of different and various use.

Natural Gas is a natural product, consisting mainly of methane (CH4), and its state depends on temperature, pressure, specific volume, and its chemical composition. It may contain high methane (about 97%). Compressed Natural Gas (CNG) is produced from natural gas by compression to approximately 200 bar. Liquid Natural Gas (LNG) is natural gas that is cooled down to approximately –162 0C where methane liquefies.  Propane and Butane are also referred to liquefied petroleum gas (LPG). Together with ethane, LPGs, pentanes, and higher hydrocarbons are usually referred to as Natural Gas Liquids (NGL). The most important parameters describing the combustion properties of natural gas are (Gross) calorific value and Wobbe index. Production and use of natural gas has an adverse effect on the environment. These environmental effects might be categorized according to the part of the ecosystem influenced. Climate effects, air pollution, water pollution, and land use do occur. In general natural gas combustions products are cleaner than other fossil fuels.

About 98% carbon emissions result from fossil fuel combustion. Reducing the use of fossil fuels would considerably reduce the amount of carbon dioxide and other pollutants produced. This can be achieved either by using less energy altogether or by replacing fossil fuels by renewable fuels which seems to be difficult to meet the present world’s energy requirements. Methane hydrates are the world’s largest source of fossil fuel. Gradual use and technology improvement to extract Methane from it is foreseen. China claims to have been successful in commercial extraction of Methane from Hydrates. So far this unconventional hydrocarbon energy source remained untapped, however, because traditional source are still plentiful and less expensive to develop. Nevertheless, scientists have recently been taking a closer look at hydrates. A widely quoted US Geological Survey estimate predicts there is twice as much organic carbon in gas hydrate than in all recoverable and unrecoverable fossil fuels resources, including natural gas, coal and oil—a very promising prediction in deed!

The supplied LNG should contain typically 50 ppmv of CO2 to avoid freezing in the main exchanger and 4 ppmv H2S to meet LNG sales specification. It typically takes about 600 m3 of natural gas to yield 1m3 of LNG with 1 ton of LNG holding the energy equivalent of some 50,000 cubic ft of natural gas. Exact conversions depend upon the composition of the natural gas in question. It is the large contraction in volume from the gaseous state to the liquid state that makes LNG much easier and more economical to transport over large distances and store in large quantities. LNG is not at all explosive of flammable in its liquid state. As LNG vapor worms above –106.70C (--160 0F), it becomes lighter than air and will rise and disperse rather than collect near the ground. However, it is not explosive unless flammable concentrations of gas occur in enclosed or other confined spaces.

The LNG industry has a long and excellent safety record, due to strict industrial safety standards applied worldwide. Up to 2012 there have been some 50,000 LNG carrier voyages, without a significant accident or safety problem (i.e., loss of containment) either port or in the high seas. A gas hydrate is an ice-like crystalline solid called a clathrate, which occurs when molecules form a cage-like structure around small guest molecules at certain temperatures and pressures. Care should be taken so that such conditions of formation is avoided for possible coconut-shell like blockade inside the pipe and worst condition the pipe may be fully choked and this may be a costly and time consuming exercise to restore the usual flow.

Finally the LNG is expected to transport from the initial Tank Storage of Moheshkhalito Chittagong main NG supply terminal. Flow assurance encompasses the

thermal-hydraulic design and assessment of multiphase production/transportation systems as well as the prediction, prevention and recommendation of flow problems such as gas hydrate formation, wax and asphaltene deposition on walls, corrosion, erosion, scaling, emulsions, foaming, severe slugging, etc, and in all cases, flow assurance designs must considered and incorporated for the capabilities and requirements for all parts of the system throughout the entire production life of the system to reach a successful solution for securing the supply operations, minimizing the downtimes, and reducing overall cost including transportation costs (Ref: Natural Gas Hydrates in Flow Assurance by  D. Sloan, C.Koh,A.K.Sum,  Gulf Professional Publishing, USA, 2011).

Liquid Natural Gas management is a huge job and though seems to be dictated by commercial norms but it is extremely technical and liquefaction to gasification involves lots of technical involvements and quality of the LNG is of prime importance since the usual impurities and contaminants at the later stage may have serious consequences to ensure flow and any flow restriction can jeopardize the whole operation and difficult to get remedy and such job may be extremely expensive and time consuming.

Our economy is expected to boost up especially the power and fertilizer sector with the imported LNG and its smooth supply in cost effective way and the country is looking forward to this.

The writer is a contributor to

The Independent

Email: [email protected]

 

 

LNG: Pros and cons

Natural gas is an essential energy source and people have various confusions regarding its derivatives and related products

It is indeed a great relieving news that Bangladesh has entered to a new era of imported LNG since for the last decade or so, Bangladesh was in the grip of acute energy crisis to meet the domestic industrial need and national prosperity in the industrial sector proved a great threat due to drastic short-fall in domestic natural gas supply owing to rapid depletion of natural gas wells in the country. According to the published information released so far that Moheshkhali floating LNG terminal will include a floating storage and regasification unit (FSRU), a subsea buoy system and a subsea pipeline, which will connect the terminal to an on shore pipeline system. The FSRU is expected to have a storage capacity of 138,000 Nm3 of LNG and a regasification capacity of 500 Mcf/day. The terminals offshore subsea buoy system may be used mooring and will also serve as a conduit to transfer natural gas onshore. It should be borne in mind that the Moheskhali site is unfortunately situated under the natural calamity area as such adequate safety precaution should be taken to face any natural cyclonic calamity and possible tidal bore, effect of Tsunami etc. The Equipment, Piping loop as well as supply line should be adequately protected as discussed in this article below, especially from the possibility of hydrate formation and impurities contaminants and its consequences. All safety protections must be ensured as per the environmental studies and necessary precautions should be incorporated and strictly monitored. Natural Gas is an essential energy source and people have various confusions regarding its derivatives and related products commonly named as commercial products of different and various use. Natural Gas is a natural product, consisting mainly of methane (CH4), and its state depends on temperature, pressure, specific volume, and its chemical composition. It may contain high methane (about 97%). Compressed Natural Gas (CNG) is produced from natural gas by compression to approximately 200 bar. Liquid Natural Gas (LNG) is natural gas that is cooled down to approximately 162 0C where methane liquefies. Propane and Butane are also referred to liquefied petroleum gas (LPG). Together with ethane, LPGs, pentanes, and higher hydrocarbons are usually referred to as Natural Gas Liquids (NGL). The most important parameters describing the combustion properties of natural gas are (Gross) calorific value and Wobbe index. Production and use of natural gas has an adverse effect on the environment. These environmental effects might be categorized according to the part of the ecosystem influenced. Climate effects, air pollution, water pollution, and land use do occur. In general natural gas combustions products are cleaner than other fossil fuels. About 98% carbon emissions result from fossil fuel combustion. Reducing the use of fossil fuels would considerably reduce the amount of carbon dioxide and other pollutants produced. This can be achieved either by using less energy altogether or by replacing fossil fuels by renewable fuels which seems to be difficult to meet the present worlds energy requirements. Methane hydrates are the worlds largest source of fossil fuel. Gradual use and technology improvement to extract Methane from it is foreseen. China claims to have been successful in commercial extraction of Methane from Hydrates. So far this unconventional hydrocarbon energy source remained untapped, however, because traditional source are still plentiful and less expensive to develop. Nevertheless, scientists have recently been taking a closer look at hydrates. A widely quoted US Geological Survey estimate predicts there is twice as much organic carbon in gas hydrate than in all recoverable and unrecoverable fossil fuels resources, including natural gas, coal and oila very promising prediction in deed! The supplied LNG should contain typically 50 ppmv of CO2 to avoid freezing in the main exchanger and 4 ppmv H2S to meet LNG sales specification. It typically takes about 600 m3 of natural gas to yield 1m3 of LNG with 1 ton of LNG holding the energy equivalent of some 50,000 cubic ft of natural gas. Exact conversions depend upon the composition of the natural gas in question. It is the large contraction in volume from the gaseous state to the liquid state that makes LNG much easier and more economical to transport over large distances and store in large quantities. LNG is not at all explosive of flammable in its liquid state. As LNG vapor worms above 106.70C (--160 0F), it becomes lighter than air and will rise and disperse rather than collect near the ground. However, it is not explosive unless flammable concentrations of gas occur in enclosed or other confined spaces. The LNG industry has a long and excellent safety record, due to strict industrial safety standards applied worldwide. Up to 2012 there have been some 50,000 LNG carrier voyages, without a significant accident or safety problem (i.e., loss of containment) either port or in the high seas. A gas hydrate is an ice-like crystalline solid called a clathrate, which occurs when molecules form a cage-like structure around small guest molecules at certain temperatures and pressures. Care should be taken so that such conditions of formation is avoided for possible coconut-shell like blockade inside the pipe and worst condition the pipe may be fully choked and this may be a costly and time consuming exercise to restore the usual flow. Finally the LNG is expected to transport from the initial Tank Storage of Moheshkhalito Chittagong main NG supply terminal. Flow assurance encompasses the thermal-hydraulic design and assessment of multiphase production/transportation systems as well as the prediction, prevention and recommendation of flow problems such as gas hydrate formation, wax and asphaltene deposition on walls, corrosion, erosion, scaling, emulsions, foaming, severe slugging, etc, and in all cases, flow assurance designs must considered and incorporated for the capabilities and requirements for all parts of the system throughout the entire production life of the system to reach a successful solution for securing the supply operations, minimizing the downtimes, and reducing overall cost including transportation costs (Ref: Natural Gas Hydrates in Flow Assurance by D. Sloan, C.Koh,A.K.Sum, Gulf Professional Publishing, USA, 2011). Liquid Natural Gas management is a huge job and though seems to be dictated by commercial norms but it is extremely technical and liquefaction to gasification involves lots of technical involvements and quality of the LNG is of prime importance since the usual impurities and contaminants at the later stage may have serious consequences to ensure flow and any flow restriction can jeopardize the whole operation and difficult to get remedy and such job may be extremely expensive and time consuming. Our economy is expected to boost up especially the power and fertilizer sector with the imported LNG and its smooth supply in cost effective way and the country is looking forward to this. The writer is a contributor to The Independent Email: [email protected]