Few equipment suppliers for gas turbine power generators can claim experience with hot catalyst systems for emissions controls. While there are companies in similar applications, critical differences exist between a simple cycle gas turbine catalyst system and other systems for combined cycle or reciprocating engines. INNOVA Global has operational experience with catalyst systems for all three power generator types and can help guide the end client in the areas of importance to ensure emissions and noise control is achieved.
Simple cycle (SC) catalyst systems on gas turbines pose a significantly different design challenge from combined cycle (CC) gas turbine catalyst systems. The SC catalyst system must operate in the high exhaust temperature of the gas turbine, typically running in the 875°F to 1050°F range which is above the maximum operating temperature of most conventional NOx reduction catalysts, and therefore, requires cooling tempering air. SC catalyst systems for high 90+% NOx removal levels require very uniform flows of NOx in the flue gas and highly uniform ammonia reactant distribution, along with precise temperature and velocity profiles. In contrast, the CC catalyst system is usually embedded in the rows of boiler tubes of an HRSG allowing the system designer to place the catalyst system in a lower temperature zone not requiring a tempering air system.
In designing gas-fired power plants, the power generation industry often ignores noise propagation, believing any potential problems will go away, provided the plant meets the Occupational Safety and Health Administration–specified maximum noise level of 85 dBA within operating areas. Operators believe that, should noise complaints arise from nearby residents, they can be dealt with by retrofitting some simple mitigation such as a noise barrier. This approach is aimed at lowering upfront cost. However, due to the difficulty of retrofitting mitigation on major noise-generating equipment, this is a high-risk approach, potentially leading to millions of dollars of post-construction expenses, lost revenue, costly litigation, and liability damages.
The Alberta Energy and Utilities Board (EUB) has issued one of the most comprehensive noise limit criteria in Directive 038, largely concerning the extensive oil and gas industry in Alberta. Along with the sound level criteria, addressed are the environmental surveying conditions, complaint investigation process and sound level prediction methodology. Several other jurisdictions have set criteria to limit the noise from oil- and gas-related operations, including the Colorado Oil and Gas Conservation Commission (COGCC), which recently voted to repeal their provision of a more stringent noise level criterion. Most of the criteria do not include limits on low-frequency noise unless such specific complaints have been made. Many regulations also give simplified criteria outlining A-weighted level limits at set distances from the source. Having a comprehensive set of criteria (such as in the EUB guidelines) gives the energy industry a more useful tool to proactively include noise mitigation in their environmental impact assessments. This paper will compare the noise limit criteria of several different jurisdictions including permissible sound levels, meteorological conditions, prediction modeling parameters and assumptions, measurement protocols and reporting requirements.
On August 4, 2011, Article X of the Public Service Law for the State of New York was reenacted. The revised Article X consolidates the certification process for electric generating facilities producing 25 MW or more under the New York State Public Service Commission (PSC). One of the major provisions of Article X is the inclusion of an environmental impact analysis, though its requirements with regards to facility operational noise are not well defined. The paper discusses quantifiable metrics and noise criteria that the Siting Board may consider in the Article X process going forward.
Low frequency noise (LFN) generated by industrial and oilfield applications is generally recognized as having the potential to cause annoyance, particularly in rural residential locations. The recent revision of EUB directive 38 quantifies sound levels which may be symptomatic of an LFN annoyance condition and recommends that the dBC-dBA level be determined through modeling of new plants and expansions. This paper examines the reliability and limitations of current noise propagation modeling methods with respect to low frequency noise predictions. Topics of discussion include the importance and prospective availability of noise emission levels in the 16 Hz Octave Band, limitations imposed by the prediction accuracy of LFN in software modeling tools and standards, and potential supplementary analysis of noise sources which may help to anticipate a LFN problem. A case study involving dBC-dBA level predictions is presented as practical example.