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Boiler Efficiency: Unlocking Both Cost Savings and Sustainability

May 25, 2023
Most plants operating today have untapped potential for enhancing efficiency and realizing significant savings. Thermogenics' Joe McMullen discusses how to turn that around.

Boiler efficiency has always played a crucial role in many industries, directly impacting operating costs, product pricing, and overall profitability of the business. 

But the need for boiler efficiency extends beyond fiscal considerations.

It holds equal importance in terms of environmental impact, as well. The efficiency of a boiler must not only be looked at in terms of combustion but also from an overall steam system perspective. Poor combustion in boilers leads to increased fuel consumption, higher operating costs, and a larger impact on the environment both in the form of exhaust levels and thermally. An efficient system will reduce both costs and environmental impact.

Efficiency Through Innovation

In recent years, burner manufacturers and combustion management systems have made significant strides in enhancing boiler efficiency. Burner manufacturers continue to produce units that operate with lower excess air, higher turndown ratios, and lower NOx and CO emissions than ever before.

Combustion management systems enhance performance with tunable linkage-less control platforms that match the selected burner’s capacity. Both contribute to improved efficiency and substantial savings.

Optimizing the entire steam system offers additional fuel-saving opportunities. Strategies such as reducing blowdown rates, proper selection of water treatment, leveraging condensate return systems, and utilizing heat recovery products can yield impressive results.

Condensate Return, Waste Heat Recovery

Efficient condensate return systems effectively reduce operating costs by minimizing energy waste from failed steam traps and contaminated condensate often seen in manufacturing facilities. High rates of condensate return save on chemical treatment costs and reduce the amount of BTUs required for steam transformation upon reintroduction to the boiler.

Additionally, they lower effective blowdown rates, which directly minimize the loss of chemical treatment and fuel input associated with controlling conductivity and solids in the boiler water.

Certain systems inherently exhibit a low rate of condensate return, often due to steam injection into the process without the possibility of recovery. Consequently, these systems experience higher blowdown rates due to additional makeup water and solids introduced. However, implementing reverse osmosis pre-treatment in such systems can significantly decrease blowdown rates, resulting in reduced chemical treatment costs and substantial fuel savings.

Also, incorporating heat exchangers in the boiler stack enables the utilization of “free heat” in the boiler exhaust to preheat boiler feedwater or make-up water. A properly sized economizer can yield returns of 5-7% gains in efficiency and fuel savings.

Case Study: Food Manufacturing Plant

A major food manufacturing facility in Texas recently achieved remarkable efficiency gains by combining various technologies. With 85% of the generated steam utilized in the production process, Thermogenics implemented the following solutions:

  • High turndown burners;
  • Linkage-less burner management systems;
  • Reverse osmosis pre-treatment system;
  • Two-stage heat recovery system.

The implementation of the reverse osmosis treatment dramatically reduced the effective blowdown rate from 12% to less than 2% compared to the previous system. Here’s a breakdown of the process:

  • The first stage stack economizer captures free heat from the boiler stack and raises the feedwater temperature from 227°F (fed by the deaerator supply) to 290°F before entering the boiler;
  • The flue gas temperature leaving the first stage economizer is reduced from 520°F to 320°F while operating at 120 psig steam in the upper firing range;
  • The flue gas then flows into the second stage condensing economizer;
  • The high-flow reverse osmosis (RO) water is preheated using the remaining available heat, raising the make-up water temperature from an average inlet temperature of 60°F to 135-180°F before being introduced to the deaerator for scrubbing.

This significantly reduces the amount of pegging steam required to complete the deaeration process, while also lowering the exhaust temperature of the flue gas to 100-120°F. Under optimal conditions, this plant operates with a thermal efficiency well above 92%, resulting in lower emissions and a reduced environmental impact.

Investing in Efficiency

Despite upfront costs, a proper system survey often demonstrates that the ROI of these systems can be achieved in a few short years or even months. With rising fuel costs and tighter emission regulations, the utilization of these technologies not only offers attractive ROI but also ensures emissions compliance.

Grants and environmental incentives are often available to assist in funding these improvements. 

Of course, the examples provided here are only some of the ever-advancing technologies in boiler efficiency. Most plants operating today have untapped potential for enhancing efficiency and achieving substantial savings. 

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Based in Cincinnati OH, the author has been an integral part of operations at Thermogenics since 2010.