Economizer outlet gas temperature control

Controlling gas temperatures

GE Steam Power offers advanced boiler solutions and systems to control the gas temperature in selective catalytic reduction (SCR) so your plant can operate at low load and still comply with environmental restrictions.

Our systems are fully integrated with your boiler’s controls (DCS) and are tailored to meet your plant’s needs. Based on your unit, we can customize the right boiler solution to meet operating requirements.

  • Subcritical boiler: Our patented Hot Water Recirculation System (HWRS) controls exit gas temperature by extracting a portion of hot water from the boiler downcomers and mixing it with the feedwater upstream of the economizer inlet.
  • Supercritical boiler: Our patented Economizer Recirculation System (ERS) recirculates waterwall outlet fluid.

Avoiding shutdowns and parasitic power

GE’s boiler control systems increase the fluid inlet temperature to the economizer, which increases the economizer outlet gas temperature at reduced loads. There are other effective solutions available depending on your unit and your operating requirements.


  • Easy to control gas temperatures to SCR at low loads
  • Operates only during required loads, avoiding parasitic power used at high loads
  • Increases boiler demand flexibility
  • Operating SCR at low loads avoids increased startup/shutdown cycles, reducing wear and tear on your boiler

NOx reduction solutions for boilers


You can benefit from a state-of-the-art combination of boiler service technologies and engineering for cost-effective in-boiler NOx compliance, for both power generation plants and industry-specific plants. Primary low NOx measures include our portfolio of cutting-edge low NOx burners. We can help you reduce NOx levels by up to 50% with a combination of LNCFS* for our OEM boilers, RSFC* and RoBTAS* for other manufacturers’ boilers, and our overfire air systems.

We can help you achieve a secondary reduction of up to 30% of NOx with a selective non-catalytic converter (SNCR) system. This works by injecting urea or ammonia in the upper part of the furnace. At temperatures of 1,500 to 2,010 °F the NOx is reduced without the need for a catalyst.

The GE Umbrella-SNCR (U-SNCR) is unique because the urea is sprayed within the furnace with a nozzle that is adjustable in height. The process uses cooled lances, which carry flexible hoses arranged in the furnace. There are no boiler size constraints, and the technology is easy to control. By selecting GE, you can reduce your NOx boiler emissions by up to 60% while remaining competitive and productive.

Emissions reductions—mercury

Mer-cure* Mercury Reduction System

GE has developed an advanced mercury control technology capable of high removal efficiencies. This patented technology, called Mer-Cure, is an enhanced activated carbon injection system which has unique attributes that complement mercury oxidation and subsequent mercury capture.

Advanced mercury capture

The sorbent is injected into the duct upstream of the air heater, which allows for enhanced utilization of the effective temperature range for oxidation and provides longer residence time for enhanced mercury capture.

For additional mercury capture and reduced sorbent consumption, our patented activated carbon milling technology can add even more value to your plant's emissions reduction system, in addition to our other power and industrial boiler services.


  • Enhanced mercury (Hg) capture rates >90%
  • Reduced sorbent consumption by up to 50% compared to traditional removal systems
  • Lower OpEx
  • Wide range of potential sorbent suppliers

*Trademark of General Electric Company.

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