Major Steel Producer Improves ESP Performance with Neundorfer without any Shutdown Days

Summary

A large, integrated steel producer wanted to reduce the unplanned production stops on their BOF– a result of issues with their ESP. Neundorfer provided an integrated solution that was implemented while maintaining consistent production!

“We had discussions with leadership at the facility to optimize the project, ESP, and upstream processes in order to maximize long-term production and minimize emissions. By taking a holistic approach, we were able to understand how they got to where they were and what to do about it to provide the best solution.”

Jeremy Timmons VP, Engineering at Neundorfer

Full Story

A basic oxygen furnace (BOF) is the machinery used for the purification of pig iron by oxidizing impurities into slag and converting the rest into molten steel with an injection of oxygen. It is the primary method used for steel production worldwide. Emissions from the BOF are collected in an electrostatic precipitator (ESP). In this particular case, the ESP is treating 650,000 ACFM of dirty flue gas from a two-BOF vessel operation. The ESP has 6 chambers and 4 collecting fields in each chamber. Then, an induced draft fan pulls the flue gas through the ESP and exits a stack with an opacity meter as the primary real-time emissions monitoring device.

Production stops–where the injection of oxygen is stopped–were problematic. Each stop slowed the production process which impacted overall steel production. The production stops were the result of ESP equipment failure and emissions limitations. These stops were necessary to allow for lower emissions and/or personnel to isolate sections and make repairs online. Ultimately, the production of steel was impacted by these issues and something needed to be done to get output to optimal levels. The company engaged Neundorfer to help identify these problems and create an effective improvement plan. Neundorfer started with an effort to understand how the BOF process influenced performance, assessed the internal condition of the ESP and its impact on performance, and evaluated the distribution of flow through the ESP.

Major issues identified:

• Overall low power levels caused by internal clearance issues and shorted sections
• Poor discharge and collecting electrode conditions caused by corrosion
• Suboptimal flow distribution through the ESP, resulting in poor collection efficiency
• Excess air from the ductwork leading to the ESP

The ESP performance decayed at an exponential rate before the project. The high variability of the process (wide temperature and dust loading over very short periods of time) and excess air infiltrating from holes in the ductwork produced conditions to the ESP that would overwhelm it. As the ductwork began to decay, more air was entering the ESP.  Then the ID fans had to increase speed in order to provide the necessary draft at the fume hood.  More cooling water (for temperature control) was required to help the ESP perform. This cycle of events produced continually increasing gas flow, increased water usage and reduced operating temperatures, which accelerated until the ESP could not perform and the ID fans did not have enough capacity to pull an adequate draft. A plan had to be developed to help mitigate the effects of this process variability.

Solutions that were implemented:

• Replacement of the internals – necessary to maintain reliability
• Sealing of the ductwork leading to the ESP and the ESP itself – necessary to prevent future corrosion, but also to reduce the increase in gas volume the holes produced
• Upgrade to high-frequency power supplies
• Installation of optimized flow distribution devices – necessary to spread the flue gas and particulate evenly in each ESP chamber to improve collection efficiency

Another key component of the solution was to optimize the process upstream of the ESP to maximize production and minimize emissions. Neundorfer worked with the owner and the owner’s process consultant to develop a holistic solution that just wasn’t solely focused on the ESP. An incredible achievement of this project was that it was implemented without any shutdown days. All of this work was done while the BOF was online – maintaining consistent production of the plant. The project spanned multiple months and was completed without worker injuries. In the end, Neundorfer helped provide a holistic solution that not only solved short-term production issues but helped improve the production process as a whole while reducing plant emissions.

The results:

• Production stops were reduced by 99%
• Improved ESP performance at higher temperatures and lower moisture content
• Improved ESP process control operating range
• Reduced ESP emissions and prolonged life of internal components