How to cut fos­sil fuel use by 90 per cent

DEMM Engineering & Manufacturing - - ENERGY EFFICIENCY -

Mo­men­tive Spe­cialty Chem­i­cals man­u­fac­tures resin with lit­tle need for fos­sil fu­els, thanks to an en­gi­neer­ing project that has cut fuel use and CO2 emis­sions by nearly 90 per cent.

The com­pany, work­ing with En­ergy Plant So­lu­tions were hon­oured at the EECA Awards on 28 May, pick­ing up both the Large Busi­ness and In­no­va­tion tro­phies for a boiler in­stal­la­tion that runs on waste gas from its own man­u­fac­tur­ing process.

The project was de­scribed by judges as “com­pre­hen­sive and in­no­va­tive, with great team­work”.

“All the num­bers in this project are im­pres­sive – car­bon sav­ings, en­ergy, par­tic­u­lates and other ben­e­fits,” the judges said.

The plant in Hornby, Christchurch, man­u­fac­tures spe­cialised resins used in the en­gi­neered wood pan­els in­dus­try.

A by-prod­uct of the man­u­fac­tur­ing process is a waste gas stream con­tain­ing 19 per cent hy­dro­gen with the bal­ance gases of ni­tro­gen, car­bon diox­ide, wa­ter and a small per cen­t­age of or­ganic com­pounds.

Mo­men­tive wanted to har­ness the low calorific value waste gas be­ing f lared to at­mos­phere and use it as a fuel to gen­er­ate steam in a boiler plant. This would greatly re­duce the need for light fuel oil to fire the ex­ist­ing boiler plant. The in­tent was to re­duce en­ergy use, as well as CO2 and sul­phur emis­sions, to im­prove the plant’s en­vi­ron­men­tal foot­print.

Al­though sim­i­lar projects had been car­ried out at Mo­men­tive sites over­seas, plant dif­fer­ences meant a di­rect copy of those de­signs were not pos­si­ble. Mo­men­tive turned to En­ergy Plant So­lu­tions to de­sign a com­bus­tion sys­tem that would in­te­grate with its New Zealand pro­cesses.

The project in­volved sup­ply­ing and in­stalling a high ef­fi­ciency EPS 4 De­grees pack­age steam boiler. In ad­di­tion to the boiler, EPS de­signed and man­u­fac­tured a burner and au­to­mated con­trol sys­tem to com­bust the waste gas stream.

The waste gas is pro­duced at a rate of up to 3,900 cu­bic me­tres an hour and is di­rectly pro­por­tional to the pro­duc­tion rate of the process plants. Given the na­ture of resin man­u­fac­ture, process plant steam de­mand can be highly vari­able.

EPS and Mo­men­tive worked closely to­gether to in­te­grate the new boiler con­trol sys­tem with the ex­ist­ing fa­cil­ity. The re­sult is a boiler in­stal­la­tion that needs lit­tle fos­sil fuel for con­tin­u­ous oper­a­tion.

Com­pleted in May 2013, the tail gas boiler plant re­duced fuel use by 89.5 per cent in its first seven months, com­pared with 2012’s aver­age. This re­duces CO2 emis­sions by a pro­jected 1300 tonnes a year. Sul­phur emis­sions have re­duced by 99 per cent and PM10 emis­sions by 93 per cent, as­sist­ing with air qual­ity tar­gets in the Christchurch ur­ban air shed.

This project is an ex­tremely suc­cess­ful in­dus­trial scale in­stal­la­tion, cen­tred on en­ergy ef­fi­ciency, waste min­imi­sa­tion and pro­duc­tiv­ity gains. A chemical man­u­fac­tur­ing fa­cil­ity is now able to use its own waste stream as a fuel to pro­duce a process steam sup­ply to man­u­fac­ture.

The Mo­men­tive project dif­fers from nor­mal boiler in­stal­la­tions. Typ­i­cally burn­ers fit­ted to boiler plants run on con­ven­tional fos­sil fu­els and the fuel f low is reg­u­lated to main­tain the steam pres­sure or wa­ter tem­per­a­ture at the set point.

At Mo­men­tive, the waste gas stream is pro­por­tional to the pro­duc­tion rate of the man­u­fac­tur­ing process. It is not pos­si­ble to store the gas so it must be com­busted as it is pro­duced.

There was also the chal­lenge of try­ing to get clean, ef­fi­cient and re­li­able com­bus­tion when only 20 per cent of the fuel is com­bustible.

EPS en­gi­neered a sys­tem that mea­sures the waste gas stream f low rate. The f low me­ter au­to­mat­i­cally cor­rects for pres­sure and tem­per­a­ture. The gas f low data is used to cal­cu­late the re­quired air quan­tity to achieve the de­sired air/fuel ra­tio. An O2 sen­sor in the f lue gives the sys­tem feed­back on the ac­tual air/fuel ra­tio.

The sys­tem then trims the air f low by ei­ther in­creas­ing or de­creas­ing the air damper and fan speed. EPS also spent time per­fect­ing the burner head de­sign to en­sure ad­e­quate mix­ing of the waste gas stream and com­bus­tion air.

The re­sults speak for them­selves, and have set a new Mo­men­tive bench­mark for fuel use per tonne of resin in the Aus­trala­sia re­gion.

David Early, Mo­men­tive Process Con­trol En­gi­neer for Aus­tralia / New Zealand re­gion,says: “The en­vi­ron­men­tal ben­e­fits were cen­tral to the project, and these were com­mu­ni­cated clearly through­out the process.”

En­ergy Plant So­lu­tions has ap­plied the learn­ings from the Mo­men­tive plant to solve is­sues with other burner in­stal­la­tions, op­er­at­ing in un­usual ap­pli­ca­tions.

The next step for the com­pany is to de­velop burner tech­nolo­gies that im­prove the com­bus­tion of bio-gases and bio-oils de­rived from woody biomass – of­fer­ing even more scope for CO2 emis­sion re­duc­tion.

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