Could nat­u­ral gas be an­swer to a clean diesel al­ter­na­tive?

Aus­tralia is slow pick­ing up on LNG en­gine tech

Big Rigs - - TECH TALK - Bruce Honey­will Tech­ni­cal Ed­i­tor

LIKE the greedy farmer Brown from back in me­dieval times – the bloke who sold his crops for profit but had noth­ing left to feed his fam­ily through the win­ter – it ap­pears that Aus­tralia has com­mit­ted the bulk of its huge nat­u­ral gas ex­trac­tion to over­seas mar­kets, leav­ing in­ad­e­quate sup­plies for do­mes­tic use. A case of cor­po­rate farmer Brown greed.

This seems some­thing of a tragedy when one of the more vi­able al­ter­na­tive fu­els for heavy truck use in the fu­ture is nat­u­ral gas. Many mil­lions of eu­ros and green­backs have been in­vested in the nat­u­ral gas en­gine tech­nol­ogy by truck man­u­fac­tur­ers.

In spite of the Turn­bull Govern­ment’s at­tempt to stem the rivers of nat­u­ral gas flow­ing over­seas, the ex­trac­tion and pro­cess­ing in­dus­try is ad­dicted to profit, with 37 mil­lion tonnes of LNG ex­ported, worth $16.55 bil­lion, in the 2015-16 fi­nan­cial year

Most of Aus­tralian gas goes to Ja­pan, China and South Korea, and gas ex­porters are busily build­ing in­creas­ing mar­kets in Tai­wan and In­dia.

And, hard to be­lieve, in 2016 AGL an­nounced the like­li­hood of spend­ing $300 mil­lion to build a gas im­port fa­cil­ity – talk about coal to New­cas­tle.

The pos­si­bil­ity of im­port­ing gas to one of the most gas-rich coun­tries in the world.

Much has been writ­ten of elec­tric-pow­ered trucks in re­cent times, with fast-evolv­ing bat­tery tech­nol­ogy. How­ever, all ma­jor truck man­u­fac­tur­ers have al­ready dipped their toes in the sea of po­ten­tial they claim for nat­u­ral-gaspow­ered en­gines.

Just about all ma­jor truck man­u­fac­tur­ers have de­vel­oped trucks to meet Euro VI emis­sion stan­dards us­ing diesel. How­ever, even cleaner in­ter­nal com­bus­tion en­gines can be en­gi­neered to run on gas.

To date, most of the truck ap­pli­ca­tions for nat­u­ral gas en­gines are in the con­struc­tion, refuse and ag­i­ta­tor mar­kets, mostly be­cause fuel stor­age re­quire­ments limit the range of heavy trucks to 1000km or less.

Even to get this range, liq­uid pe­tro­leum gas (LPG) must be used and this must be kept at tem­per­a­tures be­low -100 de­grees Cel­sius, re­quir­ing com­plex and heavy ther­mos-styled fuel tanks.

An op­tion is to use com­pressed nat­u­ral gas (CNG), and this re­quires a tank en­gi­neered to hold gas at ex­tremely high pres­sure, 3000–3600psi (re­mem­ber a truck tyre runs at about 90psi). The CNG tank is big­ger and more costly than a con­ven­tional fuel tank and the range for heavy trucks is lim­ited to a few hun­dred kilo­me­tres.

Nat­u­ral gas

Nat­u­ral gas is ex­tracted from deep un­der­ground, in Aus­tralia mostly from desert gas fields and off-shore fa­cil­i­ties.

While CNG and LNG are both the same ex­trac­tive en­ergy source, stor­age meth­ods dif­fer.

Liq­uid pe­tro­leum gas (LPG) is a dif­fer­ent chem­i­cal, also called propane, and is used in many ve­hi­cles to­day and has a dif­fer­ent com­po­si­tion, com­ing from pe­tro­leum pro­cess­ing.

A nat­u­ral-gas-pow­ered ve­hi­cle ob­tains its en­ergy through the com­bus­tion of what is es­sen­tially meth­ane gas and, like diesel, it pro­duces car­bon diox­ide and wa­ter vapour through the in­ter­nal com­bus­tion process.

Nat­u­ral gas, how­ever, has fewer par­tic­u­lates than diesel and claims to be the clean­est burn­ing hy­dro­car­bon.

LNG and CNG are both con­sid­ered as vi­able fu­els for ve­hi­cles.

CNG, as well as giv­ing more chal­lenges with on-truck fuel stor­age, re­quires large in­vest­ment with re­fu­elling equip­ment, pumps, tanks, and in­creased haz­ards.

LNG is re­frig­er­ated to its liq­uid state and is more than two times as dense as CNG. It can be dis­pensed from bulk stor­age tanks and is stored in spe­cially de­signed in­su­lated tanks that op­er­ate at com­par­a­tively low pres­sures on the ve­hi­cle.

Use in heavy trucks

China has been a leader in the use of LNG ve­hi­cles, with hun­dreds of thou­sands of trucks op­er­at­ing to­day.

In North Amer­ica the par­cel de­liv­ery com­pany UPS has a large num­ber of LNG-pow­ered trucks on the road, mak­ing an in­creas­ing per­cent­age of the com­pany’s 16,000 prime mover fleet.

Europe was slower to pick up LNG as a fuel, pos­si­bly be­cause of the dif­fi­culty in ac­quir­ing the gas, but in the past cou­ple of years has em­braced the gas tech­nol­ogy.

Cum­mins launched the West­port ISX12G for heavy trucks back in 2013, based on the ISX12 diesel en­gine, and it is be­com­ing avail­able in the trucks of the In­di­ana com­pany’s OEM part­ners in the US.

The ISX12G can use ei­ther LNG or CNG and uses a com­bus­tion tech­nol­ogy that dif­fers to a tra­di­tional diesel burn, us­ing a sto­i­chio­met­ric cooled ex­haust gas re­cir­cu­la­tion (SEGR) com­bus­tion tech­nol­ogy and a three-way cat­a­lyst (TWC).

SEGR com­bus­tion uses spark ig­ni­tion, tak­ing a mea­sured quan­tity of ex­haust gas and pass­ing it through a cooler to re­duce tem­per­a­tures be­fore mix­ing

Even cleaner in­ter­nal com­bus­tion en­gines can be en­gi­neered to run on gas.

it with fuel and the in­com­ing air charge to the cylin­der.

The ISX12 G re­quires no ac­tive af­ter-treat­ment such as a diesel par­tic­u­late fil­ter (DPF) or se­lec­tive cat­alytic re­duc­tion (SCR).

The 12-litre gas en­gine is avail­able in horse­power rat­ings from 320–400hp with 1966Nm of torque.

Cum­mins says the ISX12 G is a ded­i­cated fac­tory-built nat­u­ral gas en­gine, but it shares many of the same com­po­nents as its diesel sib­ling and op­er­ates on 100% clean-burn­ing, low-cost nat­u­ral gas. Cum­mins is rec­om­mend­ing the gas en­gine for trucks used in the mixer, dump truck and refuse ap­pli­ca­tions.

Sca­nia launched a nat­u­ral-gas-pow­ered Euro VI truck in 2014 and is claiming many en­vi­ron­men­tal ad­van­tages and lower fuel costs, say­ing re­duced run­ning costs will more than out­weigh the higher pur­chase price in many ap­pli­ca­tions.

In the Sca­nia LNG trucks, the gas is stored on board at -132 de­grees Cel­sius, held in a highly in­su­lated tank sur­rounded by a vac­uum, the whole thing in­side an­other in­su­lat­ing layer – a big ther­mos tank.

Just last month, Volvo has launched two LNG-pow­ered mod­els, claiming the new trucks have the same per­for­mance, driv­abil­ity and fuel con­sump­tion as the equiv­a­lent diesel-pow­ered mod­els, with re­duced emis­sions in the range of 20–100 per cent.

The new mod­els are the Volvo FH LNG and the FM LNG, avail­able in 420 or 460hp ver­sions for heavy re­gional and long-haul op­er­a­tions.

The Volvo LNG tanks can store fuel in a tem­per­a­ture range of -40 to -125 de­grees Cel­sius, with the largest fuel tank giv­ing a range of up to 1000km, sim­i­lar to Sca­nia.

Volvo says re­fu­elling will take about the same time as fill­ing with diesel.

In the Volvo sys­tem, fuel is warmed as it is pumped out of the tank and con­verted to a gas be­fore it is in­jected into the en­gine with a tiny squirt of diesel to aid ig­ni­tion.

The Volvo G13C en­gine is a Euro VI in-line six cylin­der, 13-litre com­mon rail en­gine with in­jec­tor noz­zles for gas and diesel.

It is avail­able with an out­put of 420hp/2100Nm of torque or 460hp/2300Nm of torque.

A range of 1000km re­quires the 495-litre fuel tank.

Dif­fer­ing from the Sca­nia ver­sion, a SCR emis­sions man­age­ment sys­tem and par­tic­u­late fil­ter are re­quired to main­tain Euro VI com­pli­ance.

So nat­u­ral-gas-pow­ered en­gines are avail­able to­day, with the ad­van­tages of re­duced run­ning costs, less in­ter­nal cor­ro­sion and sig­nif­i­cantly re­duced emis­sions.

Are we, in gas-rich Aus­tralia, likely to see them in any num­bers here?

Don’t hold your breath.

PHOTO:

COOL DOWN: LNG is car­ried at be­low -100 de­grees Cel­sius and re­quires heav­ily in­su­lated on-truck fuel tanks.

PHOTO: CON­TRIB­UTED

The Volvo LNG en­gine uses a mi­nus­cule in­jec­tion of diesel to aid com­bus­tion and re­quires a small diesel tank as well as the LNG stor­age.

Sca­nia launched nat­u­ral gas pow­ered trucks in Europe in 2014.

PHOTO: CON­TRIB­UTED

POS­SI­BIL­ITY IS THERE: The Cum­mins West­port ISX12 G on show in the US.

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