Alternative Fuels for Glass Melting

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Melting glass Alternative fuels for glass melting

Tunc Goruney*, Richard Huang**, Jinghong Wang*** explain how the challenges associated with the use of alternative fuels in traditional air-fuel combustion can be overcome via oxy-fuel combustion technology.

hile global demand for technology portfolio for glass melting air-fuel fired furnace to full oxy-fuel natural gas continues to rise; that can use a wide range of alternative combustion using Air Products’ Wan increased share of supply fuels including but not limited to coke Cleanfire® combustion technology for a is forecast to come from unconventional oven gas (COG), pulverised coal, pet- pharmaceutical borosilicate glass sources such as those produced from coke and combinations thereof. In this manufacturer in China utilising coke shale formations (Fig 1). This abrupt article, examples on various uses of oven gas with a heating value of less change in the supply chain has triggered alternative fuels used in glass melting than half that of natural gas. variations in fuel prices across different applications are discussed with an In this case, the glass manufacturer regions, particularly where they lack a emphasis on how the aforementioned was looking for a solution to the domestic supply of natural gas or where challenges associated with the use of traditional air-fuel combustion in its natural gas resources are located in alternative fuels can be overcome via glass melting process to meet the local economically inaccessible geological oxy-fuel combustion technology. government’s emissions regulations. The formations. This, in turn, has impacted Here, the word ‘alternative’ refers to glass manufacturer recognised that air- many energy intensive industries either any fossil- or renewable fuel other fuel combustion of some relatively including glass manufacturing that than the traditional fossil fuels (natural dilute syngas blend might not be able to heavily relies on natural gas and fuel oil gas and oil) used in glass melting, or attain high enough flame temperature as for glass melting. As a result, a strong combined and simultaneous use of required for efficient melting of glass. demand has emerged to use less traditional fossil fuels used in glass expensive alternative fuels while melting. meeting stringent environmental The first example is a conversion of an continued » regulation targets without compromising glass quality and 30 productivity. History Projections

However, there are many challenges 25 for the use of alternative fuels in traditional air-fuel combustion. These 20 include decreased productivity induced Shale gas by low heating value fuels, flame stability Onshore unconventional issues associated with difficult-to-ignite 15 fuels, and the presence of particulate

matter leading to lower glass quality and 10 more particulate emissions. Onshore conventional Challenges have also arisen in the 5 attempt to blend multiple fuels to Offshore achieve an optimised balance of combustion stability and efficiency, glass 0 Alaska furnace productivity and reduced cost. 1990 2000 2006 2009 2020 2030 To address these issues, Air Products ៌ Fig 1. US Natural Gas Production Projection (Trillion cubic feet) www.glass-international.com has developed an oxy-fuel combustion Source: US Energy Information Administration. 0 Glass International October 2013 air products_00_GI_0909 9/27/13 4:38 PM Page 2

Melting glass

produce a large increase in flame a b luminosity. LPG mixed with air is widely used as a backup fuel in glass manufacturing industry and can alternatively be used as a co-firing fuel to increase combustion efficiency and reduce production cost. Similarly, natural gas co-firing with other fuels can lead to increased luminosity and flame radiation. As illustrated in Fig 3, a relatively small

៌ Fig 2. Oxy-natural gas flame produced by a Cleanfire HRi burner: a) natural gas only; b) natural gas co- amount of oil can significantly increase fired with LPG (12.5% LPG by thermal input). flame radiation. In both of the co-firing examples, the results indicate that the Also, due to the increased syngas fuel dynamics (CFD) simulations, showed flame radiation within 600-1100nm volume, the already short air-fuel flue- that Cleanfire HRi gas burners could (visible and near IR range, which is gas residence time in the furnace would deliver sufficient levels of heat flux for desirable for glass melting) approximately become even shorter, making the use of glass melting with the coke oven gas doubles with only 3% oil or 12.5% LPG syngas as alternative fuel a real blends with a heating value of less than co-firing (by thermal input). challenge. The proposed solution to half that of natural gas. The laboratory Air Products has extended the displace air with oxygen was the obvious findings were later validated, and burner capabilities of its successful Cleanfire path to follow. performance demonstrated, by a combustion technology applicable to However, with gaseous alternative successful commercial installation in the gaseous and liquid fuels to direct fuels of low heating value, it is also customer furnace. combustion of solid fuels for glass important to ensure the burners can The second example is a compilation melting applications, specifically produce a stable and luminous flame, of recent results from testing of burner pulverised petroleum coke (petcoke) and desirable for most glass melting configurations at Air Products pulverised coal. applications. It should not compromise laboratories that blend multiple fuel The most attractive features of petcoke the structural integrity of burners and types for optimisation of flame radiation are its high heating value, relatively low burner blocks, as the fuel discharge and melting efficiency. Fig 2a shows the price and little ash content. Petcoke has volumes and velocities are inversely bottom view of an oxy-natural gas flame been around since oil refining began, proportional to the heating value of the produced by a Cleanfire HRi natural gas but booming production of tar sands fuel, and therefore, can be multiple burner. Fig 2b shows the same view of a bitumen and other heavy oils has times higher than that of natural gas. 12.5% LPG (by thermal input) in natural dramatically raised production in recent To verify the compatibility of Air gas co-fired oxy-fuel flame produced by years[1]. In 2015, production is expected Products’ Cleanfire HRi gas burners with the same burner, where the LPG to grow to 161 million tonnes per year oxy-coke oven gas firing and optimise contains approximately 95% propane. with main sources in Brazil, China, burner parameters, extensive tests of Both images were captured using India, Spain, Taiwan, Canada, USA, simulated blends of the corresponding identical imaging parameters. It is Venezuela and South Africa[2]. As a coke oven gas were conducted at Air qualitatively evident from these images result, the increased supply has created Products laboratories. The lab results, that a small amount of LPG co-firing, new demand and opened markets for confirmed by computational fluid approximately 5% by volume, can this fuel, including glass manufacturing. One of the major challenges 2.4 associated with the use of petcoke in traditional air-fuel combustion is the

2.2 600-1100nm difficulty of ignition and maintaining flame stability due to its low volatile 600-1600nm matter content. For that reason, the 2.0 600-3000nm combustion space of air-petcoke fired

600-4800nm ៊ Fig 3. Integrated glass furnaces generally looks hazy due 1.8 flame radiation to unburned fuel and airborne normalised to oxy- particulate matter, which could have natural gas flame 1.6 adverse effects on glass quality and fuel as a function of oil efficiency. co-firing The large amount of this ‘fugitive’ fuel 1.4 percentage by thermal input. also has a negative impact on furnace

Integrated radiation normalised to NG flame radiation Integrated refractory life (walls and regenerators) as 1.2 it creates reducing conditions throughout the furnace. An alternative 1.0 to air-petcoke firing is the Cleanfire oxy-

0% 1% 2% 3% 4%

www.glass-international.com Oil co-firing continued » 0 Glass International October 2013 air products_00_GI_0909 9/27/13 4:38 PM Page 3

Melting glass

fuel burner technology which generates ់Fig 4. Oxy-petcoke flame produced by Cleanfire HRi solid fuel burner. stable and attached oxy-petcoke flame and produces efficient combustion of pulverised petcoke with a combustion space clear of dust and unburned fuel. Fig 4 shows the oxy-petcoke flame produced by Cleanfire HRi solid fuel burner technology. For increased flexibility, the Cleanfire HRi solid fuel burner fits into the same burner block as Cleanfire HRi natural gas and Cleanfire HRi oil burners, making the on-the-fly conversion between the fuels relatively easy, minimising production interruptions. The combination of a stable luminous flame and a clear combustion space allows fuel savings and increased glass quality compared to petcoke, including drying, grinding and refractory life. One way of overcoming traditional air-fuel combustion of transportation, having a sulphur these challenges is, converting these petcoke. content less than two weight percent. furnaces to oxy-fuel via the Cleanfire Air Products has also developed round The assumed price of oxygen is combustion technology to achieve a flame solid fuel burners that are fully approximately $60 per metric ton (on- stable luminous flame with minimal interchangeable with the existing site supply such as VSA). This analysis carryover of unburned particulate, as Cleanfire Gen1 natural gas and oil does not include multifaceted benefits of depicted in Fig 4. Accordingly, replacing burners. The solid fuel burners can be converting from air- to oxy-fuel, such as natural gas with petcoke in a natural gas used as i) primary oxy-fuel burners, ii) elimination of regenerators, reduction of fired 300 metric TPD regenerative oxy-boost burners, and as iii) oxygen- gaseous and particulate emissions, value furnace, and concurrent conversion to enriched fuel nozzles for under-port and of production increase and improved oxy-fuel can bring annual operating cost side-port firing in glass melting furnaces. glass quality. Rather, it solely represents savings in excess of $5 million. Several commercial oxy-petcoke a comparison of the cumulative fuel and Results suggest a potentially strong demonstrations are currently planned oxygen cost (where applicable), which economic case for replacing natural gas for glass melting furnaces in Asia. are the principal operating costs. with petcoke, with reliance on Cleanfire Fig 5 illustrates principal operating Fig 5 shows that, replacing natural gas oxy-fuel burner technology to assure cost components of a typical 300 metric with petcoke in a natural gas fired 300 high efficiency, reliable combustion and TPD regenerative glass furnace before metric TPD regenerative furnace can minimisation of upset to glass product and after converting to oxy-fuel for two provide annual savings in excess of $6 quality. different fuels, ie natural gas and million. However, as mentioned earlier, In today’s volatile global economy, it petcoke. The analysis reflects current traditional air-fuel combustion of is more important than ever for glass typical fuel prices in China, $18 and $9 petcoke in glass furnaces introduces manufacturers to be well prepared per million Btu for natural gas and challenges with an unfavourable impact against large fluctuations in fuel prices petcoke, respectively. The price of on glass quality, fuel efficiency, gaseous and diversify their process capabilities. petcoke includes preparation cost of and particulate emissions and furnace Air Products can help mitigate the glass manufacturer’s risk by offering fully integrated oxy-fuel combustion Fuel & oxygen cost for a 300 metric TPD A Air-Natural Gas Air-Petcoke regenerative furnace More monetary benefit at first glance, but need to consider solutions that can effectively utilise less 14 hidden costs due to: expensive alternative fuels. ឣ - Poor flame stability 12 - Incomplete combustion 10 B - Short furnace file List of References - High Nox 8 A - High particulate emissions [1] Stockman L, “Petroleum Coke: the coal Oxygen hiding in the Tar Sands” Oil Change 6 B Air-Natural Gas Oxy-Petcoke International, Washington, DC, January 2013 4 Best option due to: Fuel - Excellent flame stability [2] Goral D, Wylenzek A, “The efficient coal 2 - Complete combustion alternative. Petroleum coke fired CFB boilers 0 - Longer furnace life - Lower NO in Europe” Coal Gen Europe, Warsaw, Poland, Natural Gas Petcoke Petcoke x Fuel & oxygen costs, $ million/yr costs, & oxygen Fuel Converted - Lower particulate emissions February 14-16, 2012 Air-Fuel Air-Fuel to Oxy-Fuel - No regenerators Assumptions: Natural gas price $18 per million Btu, petcoke price $9 per million Btu, approximate oxygen price $60 per metric ton, *Tunc Goruney, Combustion Technology 20% fuel savings from air- to oxy-fuel conversion, identical natural gas and petcoke combusion efficiency Lead – Glass Industry Segment, Air Important notes: This analysis does not include the following benefits of converting from air- to oxy-fuel: - Regenerator capital savings Products, **Richard Huang, Glass - Flue gas emission control, capital and operating savings Industry Manager, Air Products Asia. - Value of production increase - Value of improved glass quality ***Jinghong Wang, Combustion Technology Manager, Air Products Asia. www.glass-international.com ៌Fig 5. Fuel and oxygen cost for a 300 metric TPD regenerative furnace. Website www.airproducts.com 0 Glass International October 2013 For more information, please contact us at: België France Portugal Air Products NV Air Products SAS GASIN – Grupo Air Products T +32 02 255 28 95 T +33 0800 480 030 T +351 229 998 300 [email protected] [email protected] [email protected] airproducts.be airproducts.fr gasin.com Belgique Italia Россия Air Products SA SAPIO Produzione Idrogeno Ossigeno ООО «Эйр Продактс» T +32 02 255 28 95 S.r.l. Эл. адрес: [email protected] [email protected] T +39 039 8398286 airproducts.ru airproducts.be/fr [email protected] Slovenská republika grupposapio.it Česká republika Air Products Slovakia s.r.o. AIR PRODUCTS spol. s r.o. 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