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Title: Reduce Air Infiltration in Furnaces

Abstract

This DOE Industrial Technologies Program tip sheet describes how to save energy and costs by reducing air infiltration in industrial furnaces; tips include repairing leaks and increasing insulation.

Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
875896
Report Number(s):
DOE/GO-102006-2222
TRN: US200603%%332
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Technical Report
Resource Relation:
Related Information: Industrial Technologies Program (ITP) Energy Tips - Process Heating Tip Sheet #5 (Fact Sheet)
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 42 ENGINEERING; AIR INFILTRATION; FURNACES; ENERGY EFFICIENCY; INDUSTRY; INDUSTRIAL ENERGY EFFICIENCY; DOE INDUSTRIAL TECHNOLOGIES PROGRAM; ITP; U.S. DEPARTMENT OF ENERGY; PROCESS HEATING; INDUSTRIAL FURNACES; Industry

Citation Formats

Not Available. Reduce Air Infiltration in Furnaces. United States: N. p., 2006. Web. doi:10.2172/875896.
Not Available. Reduce Air Infiltration in Furnaces. United States. doi:10.2172/875896.
Not Available. Sun . "Reduce Air Infiltration in Furnaces". United States. doi:10.2172/875896. https://www.osti.gov/servlets/purl/875896.
@article{osti_875896,
title = {Reduce Air Infiltration in Furnaces},
author = {Not Available},
abstractNote = {This DOE Industrial Technologies Program tip sheet describes how to save energy and costs by reducing air infiltration in industrial furnaces; tips include repairing leaks and increasing insulation.},
doi = {10.2172/875896},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Technical Report:

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  • The goal of this experiment was to determine if energy could be saved by providing furnaces and water-heaters with ''make-up air'' (air for combustion) from outdoors, instead of drawing this air from inside the house. By not drawing air which has already been heated and humidified from the house, cold air infiltration through cracks in windows, doors and walls should be reduced, and the furnace should not need to run as much. To conduct this experiment, six residences were modified, in addition to the previous modification of the grantee's residence. These modifications all involved natural gas heating systems, some mountedmore » in closets in the living space, other mounted in basements and crawlspaces. In the case of furnaces located in crawlspaces, the crawlspaces were sealed from the outdoors and make-up air was ducted into the furnaces from outdoors, in an effort to reduce heat loss across uninsulated floors. To summarize briefly the project results: at the Payne, Durham, and Eizenstat residences, modification apparently improved efficiency by 7.4%, 19.5%, and 3.9% respectively. At the Scheer, Mercer, and Smith residences, modification apparently degraded efficiency by 1.2%, 10.7%, and 12.3% respectively. At the grantee's residence, the effects of heating-system modifications was obscured by other efficiency-altering activity.« less
  • Chinese translation of the Reduce Air Infiltration in Furnaces fact sheet. Provides suggestions on how to improve furnace energy efficiency. Fuel-fired furnaces discharge combustion products through a stack or a chimney. Hot furnace gases are less dense and more buoyant than ambient air, so they rise, creating a differential pressure between the top and the bottom of the furnace. This differential, known as thermal head, is the source of a natural draft or negative pressure in furnaces and boilers. A well-designed furnace (or boiler) is built to avoid air leakage into the furnace or leakage of flue gases from themore » furnace to the ambient. However, with time, most furnaces develop cracks or openings around doors, joints, and hearth seals. These openings (leaks) usually appear small compared with the overall dimensions of the furnace, so they are often ignored. The negative pressure created by the natural draft (or use of an induced-draft fan) in a furnace draws cold air through the openings (leaks) and into the furnace. The cold air becomes heated to the furnace exhaust gas temperature and then exits through the flue system, wasting valuable fuel. It might also cause excessive oxidation of metals or other materials in the furnaces. The heat loss due to cold air leakage resulting from the natural draft can be estimated if you know four major parameters: (1) The furnace or flue gas temperature; (2) The vertical distance H between the opening (leak) and the point where the exhaust gases leave the furnace and its flue system (if the leak is along a vertical surface, H will be an average value); (3) The area of the leak, in square inches; and (4) The amount of operating time the furnace spends at negative pressure. Secondary parameters that affect the amount of air leakage include these: (1) The furnace firing rate; (2) The flue gas velocity through the stack or the stack cross-section area; (3) The burner operating conditions (e.g., excess air, combustion air temperature, and so on). For furnaces or boilers using an induced-draft (ID) fan, the furnace negative pressure depends on the fan performance and frictional losses between the fan inlet and the point of air leakage. In most cases, it would be necessary to measure or estimate negative pressure at the opening. The amount of air leakage, the heat lost in flue gases, and their effects on increased furnace or boiler fuel consumption can be calculated by using the equations and graphs given in Industrial Furnaces (see W. Trinks et al., below). Note that the actual heat input required to compensate for the heat loss in flue gases due to air leakage would be greater than the heat contained in the air leakage because of the effect of available heat in the furnace. For a high-temperature furnace that is not maintained properly, the fuel consumption increase due to air leakage can be as high as 10% of the fuel input.« less
  • This DOE Industrial Technologies Program tip sheet describes how to save energy and costs by reducing air infiltration in industrial furnaces; tips include repairing leaks and increasing insulation.
  • The report gives results of a study to clarify the processes that control sulfur capture by dry sorbents injected directly into a pulverized-coal-fired system, and to develop methods for generalizing data from one test furnace to another and from test facilities to fired application. Most experiments were conducted in a 1 million Btu/hr down-fired furnace to determine the effects of: fuel type, sorbent type, injection location, peak flame temperature, SO/sub 2/ concentration, and burner zone stoichiometry. Conclusions of the study include: (1) the concentration of SO/sub 2/ in the natural-gas-fired tests had a slight effect on sulfur capture, increasing capturemore » at Ca/S = 2 from 26% at 500 ppm to 40% at 3500 ppm SO/sub 2/; (2) the concentration of mineral matter in the system had a very strong impact on capture at all SO/sub 2/ concentrations and Ca/S ratios tested; (3) injecting the sorbent downstream from the main flame resulted in improved utilization in coal flames; and (4) the effect of sorbent type on capture with a given fuel was dependent on the firing conditions - including sorbent injection location and thermal conditions (the hydrated limes seemed to be most sensitive to thermal conditions and the Vicron limestone least sensitive). Dolomite gave the highest capture with all of the fuels tested.« less
  • The report gives results of a study to clarify the processes that control sulfur capture by dry sorbents injected directly into a pulverized-coal-fired system, and to develop methods for generalizing data from one test furnace to another and from test facilities to fired application. Most experiments were conducted in a 1 million Btu/hr down-fired furnace to determine the effects of: fuel type, sorbent type, injection location, peak flame temperature, SO/sub 2/ concentration, and burner zone stoichiometry. Conclusions of the study include: (1) the concentration of SO/sub 2/ in the natural-gas-fired tests had a slight effect on sulfur capture, increasing capturemore » at Ca/S = 2 from 26% at 500 ppm to 40% at 3500 ppm SO/sub 2/; (2) the concentration of mineral matter in the system had a very strong impact on capture at all SO/sub 2/ concentrations and Ca/S ratios tested; (3) injecting the sorbent downstream from the main flame resulted in improved utilization in coal flames; and (4) the effect of sorbent type on capture with a given fuel was dependent on the firing conditions - including sorbent injection location and thermal conditions (the hydrated limes seemed to be most sensitive to thermal conditions and the Vicron limestone least sensitive). Dolomite gave the highest capture with all of the fuels tested.« less