Reducing Emissions in Plant Flaring Operations
a report by Brian Duck Line of Business Leader for Flare Systems, Callidus Technologies by Honeywell
Since 2006, one of the largest integrated energy and chemical companies in the world has actively pushed toward optimisation and upgrading of pipelines, refineries and petrochemical plants in China for the purpose of minimising energy consumption, lowering emissions and maximising production.
The Goals Saving energy and reducing emissions are the internal requirements for every division of this major corporation. To achieve the public goals the company set, they issued a five-year plan entitled ‘Methods on Energy and Water Saving Management’, which was applied to all operating equipment in the 13 company-owned oil and gas fields, the 22 refineries and three pipeline companies.
The plan for the refineries focused on key areas such as improving energy efficiency, utilising the latest technologies and reducing greenhouse gas emissions.1
The company also created a ‘Green Team’
with the objective of achieving zero injury, zero pollution and zero accidents for all production facilities. These Green Teams advocated the company’s new Health, Safety and Environment (HSE) culture by eliminating energy-consuming and highly polluting production equipment and facilities that fell behind in the use of technologically advanced equipment.2
Reduce Emissions Three new petrochemical and refining plants were installed, including the 10 million ton oil-refining project in Dushanzi. One goal of the
new plant was to reduce emissions of CO2, SO2 and NOx by 130 million tons per year. Among the ten projects implemented in this new plant for the reduction of pollutant emissions were the adoption of zero flaring, the reduction in loss of product from the flares through flare gas recovery systems (FGRSs) and the reduction in the use of steam and water in the plant through the installation of the latest generation of steam-assisted flares.3
Historically, losses from flares are the single largest loss in a refinery or chemical plant. Losses to the flare include process gases, fuel gas, steam, nitrogen and natural gas. Proper operation and maintenance of flares systems helps reduce the losses from flares. Eliminating leaking valves, efficiently using fuel gases required for the proper operation of the flare and controlling the steam to achieve smokeless burning all contribute to reducing flare losses. Modifying start-up and shutdown procedures also helps to reduce flare losses, but new technology in flare tip design offers the greatest reduction in flare loss.
Equipment Selection When it came time to select flare equipment for their new ethylene plant in Dushanzi, the company wanted the latest technology to maximise the operating efficiency of the flare system. They turned
© T O U C H B R I E F I N G S 2 0 1 1
to an international combustion company, recognised for their expertise in flares and FGRS – Callidus Technologies by Honeywell.
Smokeless Flaring The company designed, built and tested two flares and two FGRSs on a fast-track basis to enable installation during the plant start-up in 2009. The flares and FGRSs were installed on the northern and southern sections of the plant. The northern flare was designed to flow more than 3,500,000lb/hr at the maximum rate and is thought to be the largest smokeless elevated flare in the world. The south flare was designed to flow almost 2,000,000lb/hr. Each flare is 155 metres tall and both flare stacks are mounted on the same derrick structure. Figure 1 shows the flare systems and derrick support system. The stacks are demountable from grade so that the tip from one flare can be maintained or replaced while the other flare remains online. The mounting of the risers permits the flare burner to be lowered to grade without the use of a crane. Since the stack is lowered to grade, no personnel are required to climb the stack beyond the first riser section to perform the needed maintenance. This makes servicing the flare much safer and since one flare remains in service, the need to shut down the plant is eliminated, saving both time and money.
Drawing upon the observations of field engineers and maintenance technicians familiar with the failure modes of conventional flares removed from service for repairs, new approaches to flare tip metallurgy, structural design and weldment fabrication have been developed. The resulting flare burner design employs a high-density tube configuration, which introduces air into the flame envelope to improve combustion at reduced steam flow, thereby lowering operational noise while increasing efficiency. This allows minimum steam consumption while optimising smokeless capacity.
The tube inlet venturi design enhances the flare burner’s ability to inspirate air via steam in the internal steam/air tubes. Tip design extends the parameters for efficient operation at low noise levels. An increased flow-area acoustical muffler with ceramic refractory lining shrouds steam injection ports, further enhancing noise attenuation.
The flare employs a cast stainless steel segment at the end of the internal steam/air tubes to enhance the service life of the flare tip. By
Brian Duck is the Line of Business Leader for flare systems for Callidus Technologies by Honeywell in Tulsa, Oklahoma. He has been in the combustion industry for more than 30 years. He is a registered professional engineer in multiple states in the US and multiple provinces in Canada. He obtained his degree in Mechanical Engineering from Oklahoma State University.
E:
brian.duck@honeywell.com
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Refining Assets
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