Liquified Natural Gas (LNG) AND Boil-Off Gas (BOG)
The Need for alternate fuels to replace oil coal, and natural gas (fossil fuels) to meet ever increasing demand for energy has been experiencing significant growth potential in various sectors. With the urgency to tackle global temperature increase because of greenhouse gases emissions resulting from the use of fossil fuels, and certain natural systems, fast transition has become the responsibility of all nations.
Hydrogen, a zero-emission energy carrier, and natural gas, a relatively cleaner fuel provide a pathway to reach the set goal to limit the global temperature to 1.50 C, as set by attending nations at the Paris Agreement 196 nations committing at the UN Climate Change Conference (COP21) in Paris, France, on 12 December 2015.
At the last meeting for COP29, India has restated its commitment to reaching a zero-emission target by 2075. It has also developed a plan and is implementing to make five million tons of hydrogen by 2030, using renewable energy and a water electrolysis process.
Moreover, viewing the current limitations for producing green hydrogen by electrolysis process to 2050 required scale, industry is heavily investing to extract hydrogen from natural gas by established steam methane reforming (SMR).
Assuming that the inevitable biproduct carbon dioxide, and other greenhouse gases can be managed, Hydrogen production by SMR will be a viable bridge to cross and reach the zero-emission energy goal.
Liquefied Natural Gas and Methane Emissions:
Though natural gas production in the domestic market in 2023 is about 25 million tons, 22.7 million tons LNG is imported. The import quotient will rise as, besides industrial and city gas distribution requirements, the fast adoption of CNG and hydrogen fuel cell vehicle population multiplies.
Methane, 95 to 97 percent of natural gas, when let to enter atmosphere the climate change effect on global temperature is 80 times more potent than carbon dioxide over the 20-25 years and the effect is to be reduced to 20 to 26 percent over 100 years. During transportation of natural gas in liquefied state containers must be designed for minus 160 degrees centigrade and internal pressure not to exceed 3 Bar. The containers must be double walled and vacuum insulated equipped with electronically controlled venting and flaring systems to handle inevitable heat leak into the tank causing LNG continuously vaporizing to gaseous state which is known as Boil off GAS (BOG).
The LNG sector encompasses many segments from the source to the end users, and each one of these is a source of methane emissions. For instance, when an LNG tanker arrives at a delivery port, about 5 percent of the contents of the tanker will be boil-off gas (BOG) from the tanker, with more methane emissions also during the unloading process and transferring to an onshore LNG cryogenic tank. For instance, on February 21,2021 an oil tanker with 147000 cubic meters (330 tons) LNG is berthed and unloading took place over 7 days (assumed) This will emit 10 tons natural gas (BOG) at 5% per day of an average 200 tons of tanker content and leakage in transfer system. Given the terminal capacity of 5 million tons LNG annually, the accumulated methane emission must worry the people and policymakers. Transportation of natural gas can be either by LNG transport trailer or in compressed gas cylinders bundled for bulk transportation. The whole supply chain is dotted with not only loss in products but substantially high methane emissions affecting the climate.
Vinjamuri innovations Pvt. Ltd, Velachery Chennai (VIPL) has suggested a patented process to control the BOG from the LNG tankers and transfer temperature BOG to specially designed filament wound composite cylinder modules (tube trailers). The proposed system prevents BOG entering the atmosphere impactfully eliminating certain expensive equipment including for regassification units and high-pressure compressors. VIPL claims significantly improved gravimetric density compared to prior-art compressed gas transportation tube trailers equipment.