Industrial Steam Boiler Heat Recovery for High Efficiency Water Heating
Demonstration of an emerging heat recovery technology for industrial steam boilers
Institute of Gas Technology dba Gas Technology Institute
Des Plaines, IL
Final invoices received and processed. This project's final report was submitted to publications 5/22/2019. Nothing new as of 10/26/2020.[br/][br/][p ]Final report with results is complete. Operation at the project site has demonstrated an increase of boiler operational efficiency from 82% to 88.6% at the current production rate at the Oxnard facility. The hot water usage at the facility varies based upon the type of equipment needed to meet the production scheduled for a given day. Based upon the stated goal of the project of an 8% increase of efficiency the current application came up 1.8% short of this goal.
Industrial boilers lose an estimated 16% of the fuel energy as waste heat in the exhaust. Recovering this waste heat and using it to heat water that is normally heated with natural gas will increase overall system efficiency with proportional reductions in natural gas use, and greenhouse gas and oxides of nitrogen (NOx) emissions. Currently available heat recovery technologies are custom engineered and fabricated for each application site and/or process. This costly site-specific engineering and installation makes the economic payback unattractive to the majority of industrial customers that could benefit from recovering waste heat.
The purpose of the project is to demonstrate the Heatsponge-Rainmaker
technology coupled to an industrial steam boiler for generation of hot
process water rather than its usual hydronic heating application that is
advantageous to the host-site and to verify the performance, energy
savings, and the emissions reduction benefits of the technology. In the
very limited deployment of this technology for steam boiler and other
non-standard applications thus far, energy savings and reduced emissions
are realized according to the some end-users and the manufacturer.
Independent verification of performance, energy savings and emissions
benefits are needed to help potential end users to better understand the
In conventional boiler exhaust heat recovery approaches for boiler feed water heating, the heat recovery unit configuration is standardized due to the proportional relationship between the water flow through the economizer to the boiler size. This setup leads to efficiency gains of 1-3% - but there is still significant energy lost through the high temperature exhaust stack which is due to the inability of standard economizers to achieve higher efficiency due in part to the low water flow rates for such applications. Under this project, the "SideKick" was installed to recover heat from a conventional steam boiler exhaust by heating a separate process water stream in the facility. This allowed for recovery of sensible and latent heat content from the exhaust stack with efficiency improvements of over 6% in most installations.
The energy recovery obtained represents 6.2% savings of the yearly projected natural gas energy used by the facility boiler. Based on these results, the estimated payback is 23.6 years based upon the current single shift operation, production rate, and $0.80/therm for natural gas. The system does provide some additional economic benefits not included in the calculation. This includes increase in available steam and hot water capabilities and avoided costs to increase the capacity of the boiler or hot water system. Based upon the operating data obtained, a three shift operation would yield a simple payback of 7.8 years. The target metric was 10% energy efficiency improvement.
The energy recovery obtained by the technology when demonstrated at Mission Linen Supply, Inc. represented 6.2% of the annual natural gas use by the facility’s boiler. This savings resulted from an increased boiler operational efficiency from 82 to 88.6%. This increased efficiency represents a projected yearly savings of 6,889 therms of natural gas and a corresponding emissions reduction of 55.2 metric tons of carbon dioxide from the facility (Mission Linen in Oxnard California).
Key Project Members
Davis Energy Group, Inc.
Tetra Tech, Inc.
Southern California Gas Company (SoCalGas)
Mission Linen Supply