LNG and LPG as fuel

By: Engr. Edgar Mana-ay

LNG means Liquefied Natural Gas while LPG is Liquefied Petroleum Gas. The two are miles away from each other as to origin, processing and use.

“Gasul” (actually a trade name) content of your 12-kg cylinders are LPG, the gas used for cooking and fuel for taxis and small trucks.

About half of taxis in Cebu are fueled by LPG which drivers claim is cheaper than gasoline or diesel. LPG is mostly propane (C₃H₈) or butane (C₄ H₁₀), entirely derived from fossil fuel sources and produced by “cooking” petroleum during the refining of crude oil in the refinery.

LPG is in liquid form inside your cylinder with “boiling” temperature BELOW room temperature. So when you open your pressurized steel LPG tank, the liquid gas inside your cylinder instantly turns to vapor at normal room pressure and temperature and enters your stove burner as its fuel. Sales of LPG cylinders are reckoned by weight because a “full” LPG cylinder contains 85% liquid and the remaining cylinder space is filled with vapor form (termed as ulliage in the oil industry).

LPG is heavier than air, unlike LNG which is lighter, hence an LPG spill is more dangerous. The vapor tends to flow along floors and tend to settle in low spots as in basements. If someone lights a match or switches a light (the contact switch produces a spark), an explosion will occur. If there is no explosion, it still can cause suffocation because LPG displaces surrounding air. If an LPG line is broken, just run out of the building if you don’t have time to close the main valve.

Recently, LNG (liquefied natural gas) hugged the headlines because of the Lopez-owned First Gen Corp’s announcement to build the first LNG import terminal facility costing $1.2 billion in Batangas. This is in preparation for Shell Philippines’ announcement that the supply of natural gas (LNG) from our Malampaya fields, the only viable gas deposit in the Philippines so far, will only last up to year 2024.

As a backgrounder, the Malampaya offshore gas deposit was discovered 60 years ago and drilling was made in the middle of Palawan seas to exploit the gas which also contains 5% condensate, a gasoline-like liquid component (technically called straight run gasoline) for further processing at the refinery. Production of LNG started in 1980 and delivered to Batangas via submarine pipeline to feed Santa Rita, San Lorenzo and Ilijan GAS-FIRED power plants generating a total of 2,700 mega watts of cheap and clean electricity for the Luzon grid.

IF THE PREDICTION OF Shell IS TRUE that the gas deposit of Malampaya will be totally depleted by 2024, then it has not reached a 50-year use.

Use of LNG fired turbine electric power plants has the most important role in the energy mix of the country. Our country now has a very ideal diversified power sources such as coal (about 55%), LNG (17%), geothermal (16%), hydro, solar, wind (12%). Because of the anticipated increase in the integration of more renewables (wind and solar) into the grid, LNG is the most viable complement to the “intermittency” of renewables generation. Starting 5 pm until 12 midnight, demand of electricity is at its peak, but solar cannot help because the sun is not shining and if there are no strong winds at that time, then wind power is also useless. In that situation a reserve gas turbine electric power plant will come in handy to fill in the shortage of power supply.

A gas turbine plant start up is immediate and the power produced is already in the grid within one hour. Not so with coal fired power plants. It takes at least 24 hours because water will still be heated into steam to turn the turbines that produce electricity. So, the most important part of the energy mixed system is the gas turbine plant that can put in additional power when there is power shortage in an hour’s notice.

By the way, LNG is predominantly methane (CH₄) with some mixture of ethane (C₂H₆) and has the same origin as crude oil deposits underground. Oil and gas originated from organic matter (remains of ancient plants and animals) in marine sediment. Burial deep underground subjected it to high temperature and pressure, at a time frame of more than a hundred million years which converted the organic matter into oil and gas. Natural gas represents the end point in petroleum maturation. Drilled out from deep underground, maybe at 14,000 ft. below a 400 ft. sea level in the Malampaya off shore field, LNG seeps out of a reefal structure underground in gas form, hence the undersea pipeline from Palawan to Batangas.

Since four years from now Malampaya gas deposit will be exhausted, we will be importing LNG, most probably from Australia or the U.S. From their wells, it has to be liquefied by cooling it to minus 162°C and at a pressure of only 4 psi, SO THAT THE LIQUID VOLUME IS REDUCED BY 1/600 OF ITS ORIGINAL GAS VOLUME. It is then shipped by super LNG tankers to any part of the globe and the proposed First Gen LNG terminal in Batangas will serve as a storage hub. The imported LNG is then re-gasified and piped to power plants served by Malampaya.

The challenge now to President Duterte, whose bravados disappears when facing China, is to hold on to the Spratleys and the Recto Bank in our very owned territory and patrimony which a greedy and bully China wants to annex as its own.

It is believed that these areas hold natural gas deposit TRIPLE THAT OF MALAMPAYA.

Note:  The author is a retired Drilling Manager of Philippine National Oil Company (PNOC).