The FurnaceMANAGER system, from INCREASE Performance, will be monitoring the furnace combustion area 24/7/365, monitoring tubes and burners for flame detection, temperature variations, and burner control. The images will be diagnosed through analytical software, and the results will be displayed to the control room, giving operators the necessary information to adjust the furnace conditions for best furnace optimization.

Production began in 2010 with an Ethylene capacity of 900,000 tonnes per annum (tpa), and Propylene 800,000 tpa. The cracking furnace section of the steam cracker production plant was designed, built, and installed by Technip.  Technip’s furnace is based on its proprietary GK6 cracking furnace technology which allows a furnace to run on a range of feed stocks from naphtha to heavy oil. Production includes 400,000 tpa of high density polyethylene and 400,000 tpa of polypropylene. The facility was built on Dow’s long-standing business relationship with Siam Cement Company (SCC), which began in 1987, and is a series of joint venture projects between the two companies.

We recently were asked our thoughts regarding whether it was worthwhile to consider replacing an old air preheater with one of today’s new designs. The focus of the question revolves around how much improvement in preheater efficiency can be expected. The following summarizes items to consider.

• If you have a fired heater or boiler without an air preheater, the unit efficiency can usually be increased to 90-92% by installing an air preheater.
• If you already have a furnace or boiler with an older air preheater, and are looking for improvement, you may have some air preheater options.
• Rotary regenerative. This is the Ljungstrom type, which has a slow-turning rotor that is packed with closely spaced heat transfer surfaces, similar to an automobile radiator. The rotor turns in the gas streams, picking up heat from the flue gas and transferring it to the combustion air. The element temperatures generally operate about halfway between the flue gas and air temperatures.
  • The advantages of the rotary regenerative air preheater are:
    • Smaller footprint and lighter structure, which usually results in lower installed cost.
    • Replaceable heat transfer surfaces. Elements are designed in pie-shaped “baskets” which are relatively easy and economic to replace and maintain performance.
  • Disadvantages of the rotary regenerative air preheater are:
    • Has seals that leak, and leakage generally increases with time. Normal, as-built leakage to be expected is about 15%. This can limit the lowest cold-end temperature achievable, especially if cold-end corrosion is a concern due to firing sulfur-bearing fuels. Enamel coating of the cold-end metallic surfaces can prolong element life.
    • Due to air-leakage, the potential for fires may be greater. If poor combustion occurs in the fired heater, unburned combustibles may accumulate in the air preheater. The possibility of fire in an air preheater increases if one air preheater is shared with multiple furnaces.
• Fixed recuperative. These are generally called static air preheaters. Their designs vary from a plate-frame type to a cast-iron “tubular” type.
  • The cast-iron type generally is larger and heavier, such that the foundations and structures become costly. The newer plate-frame type (sometimes called the Open Channel Air Preheater, “OCAP”) are lighter, and often can fit in a similar footprint as the rotary-regenerative type. This makes them a good choice for replacing a rotary type.
  • The cast-iron type has finned elements at the cold-end, which can be biased to the flue gas side, thus keeping the metal temperature above the average of the flue gas and air temperatures. This reduces the tendency for cold-end corrosion, especially when firing sulfur-bearing fuels. In addition, glass-tube bundles have been used downstream of cast-iron air preheaters to maximize efficiency.
  • Like the rotary type, the plate-frame APH metal temperature will be the average temperature of the two streams.
  • The cast-iron type air preheaters are generally bolted and sealed such that leakage can be considered nil. The plate-frame type sealing method differs depending upon manufacturer. Some use spring seals, which have not been 100% successful. Others use a welded seal construction, which provides a better, but more costly seal.
  • The OCAP heat transfer surfaces are not designed for easy replacement. Instead, entire replacement of the air preheater would be necessary.

The bottom line is that both types of air preheater have offsetting advantages and disadvantages. There have been little design changes in recent years, which have increased air preheater efficiency. However, most efforts seemed aimed at reducing manufacturing costs. It seems that most recent installations have been fixed-recuperative type, rather than rotary-regenerative type. I believe that this is due to lower first-cost and a willingness to operate the air preheater to failure, rather than spend more initially, and perform the continued maintenance necessary to maximize unit life.

Written by Bob Dubil, Copyright 2010, Carmagen Engineering, Inc.
Reproduced from the website www.Carmagen.com

David Schmitt, President and CEO of INCREASE Performance Incorporation, based in Tulsa, Oklahoma, presented a paper on the FurnaceMANAGER System, the continuous online diagnostic measurement and intelligent monitoring, various combustion burners and furnace operations. The paper also outlined how the FurnaceMANAGER provided superior flame control and flame management, tube problem assessment, and sending early warning signals to the control room.

Jeff Banister, who is highly specialized in Robotics Automated Systems Technology and is the Design & Technical Director at Increase Performance Incorporation, based in Tulsa, Oklahoma, presented a paper discussing the FurnaceMANAGER System. This paper provides details of the early warning and safety capabilities of this intelligent camera system for monitoring furnaces.

As outlined in this article, not many changes are being done in this area in today’s operations:

“Furnace or boiler operations are supported by standardized procedures and operator experience, rather than by effective online information and optimized flame control. It is surprising that a chemical process such as combustion, with an impressive economic and environmental impact worldwide, still relies on nearly archaic controls.”

There are many economic and business related reasons for monitoring and controlling the furnace, to optimize it for best results.  Economic reasons include environmental regulation of reducing NOx emissions, and environmental safety issues and personnel safety are always at the top of the priority list. In addition, there are business-related issues which motivate organizations to monitor and control the combustion area: increase fuel efficiency, reduce unnecessary shut downs because of tube or furnace damage, safety of personnel and equipment, and increased capacity.

“Combustion improvement offers the greatest potential for economic savings regarding the operation of industry boilers and furnaces. Nevertheless, the combustion process is difficult from the operator’s point of view because of limited information and feedback. For this operating unit, fuel costs are the greatest operating expense, and inappropriate fuel monitoring and oxygen monitoring make furnace optimization very unclear.”

The article outlines current operating conditions throughout the industries that utilize furnaces and boilers, and why furnace optimization is important in these economic and business related issues. The case history of measuring of the combustion area, and making the improvements are necessary, but reliable and immediate feedback of information to the operators is very important to make this happen. The example illustrated is a point in time, of a very small sample in the combustion area. As stated,

“Efficiency and emissions in industrial furnaces depend on the correct distribution of fuel and air supplies to the combustion process.”

We believe the article is correct in its analysis of current conditions, and that if correct adjustments are made, will improve these economic and business issues. The savings from optimizing the furnace will justify the technology and modified enhancements to the furnace and boilers.

One of the new technologies addressing this problem is actually the solution.  The FurnaceMANAGER system, from Increase Performance, which monitors the furnace (combustion area) 24/7/365, monitoring all tubes and burners, relays feedback through analytical software back to the control room, giving operators the necessary information to adjust the furnace conditions for best furnace optimization.