Expander retrofit

In die original system eonfiguration, die hot flue gas leaving die regenerator was expanded in die double slide valve and orifiee ehamber to atmospherie pressure, and dien passed via die waste heat boiler to die main staek. This mode of operation remains possible following die expander retrofit. 

The expander retrofit required additions to the control system due to the following modifications ... 

The first documented use of dry gas seals in turboexpanders was in 1989. At that time, an ethylene plant in Scotland worked with a dry gas seal manufacturer to retrofit a turboexpander-integral gear-generator package. The partial success of that project was sufficiently encouraging for both user plant and turboexpander manufacturer to undertake a redesign of all three expander stages. Dry face or gas seals were installed at that time. 

In order to build new facilities or expand existing ones without harming the environment, it is desirable to assess the air pollution impact of a facility prior to its construction, rather than construct and monitor to determine the impact and whether it is necessary to retrofit additional controls. Potential air pollution impact is usually estimated through the use of air quality simulation models. A wide variety of models is available. They are usually distinguished by type of source, pollutant, transformations and removal, distance of transport, and averaging time. No attempt will be made here to list aU the models in existence at the time of this writing. 

Low-temperature activity promotion is an issue in mobile (diesel) applications, but may not be a critical issue in several stationary applications, apart from those where the temperature of the emissions to be treated is below 200°C (for example, when a retrofitting SCR process must be located downstream from secondary exchangers, or in the tail gas of expanders in a nitric acid plant). In the latter cases, a plasmacatalytic process [91] could be interesting. In the other cases, the use of NTP together with the SCR catalyst is not economically viable. However, the synergetic combination of plasma and catalysts has been shown to significantly promote the conversion of hazardous chemicals such as dioxins [92], Although this field has not yet been explored, it may be considered as a new plasmacatalytic SCR process for the combined elimination of NO, CO and dioxins in the emissions from incinerators. 

The most obvious place for membrane systems in this application is in the retrofitting of existing sour gas processing plants. This would increase the capacity and reduce the energy load of the existing system or eliminate the need for expanding the existing plant when wellhead pressure loss or increased acid gas content occurs. 

Direct Decomposition Upstream of Expander Tail Gas Temperature = 450 °C Space Velocity = 45,000 h-1 N2O conversion = 70% Retrofit Factor = 50%... 

AH of the processes described above require more benzene recycle than the aluminum chloride-based processes. Retrofitting an existing aluminum chloride-based plant to a zeoHte-based plant requires not only replacement of the reaction section but also additional investment in the distiHation train. Several producers have chosen to replace their old plants during the 1980s and early 1990s with new ones based on the Mobil-Badger process, at expanded capacities. 

Section 19.15 on quick conceptual estimates has been expanded to cover a wider range of projects including retrofits. 

The ion-interaction model is a theoretically based approach that uses empirical data to account for complexing and ion pair formation by describing this change in free ion activity with a series of experimentally defined virial coefficients. Several philosophical difficulties have resulted from the introduction of this approach the lack of extensive experimental database for trace constituents or redox couples, incompatibility with the classical ion pairing model, the constant effort required to retrofit solubility data as the number of components in the model expand using the same historical fitting procedures, and the incompatibility of comparing thermodynamic solubility products obtained from model fits as opposed to solubility products obtained by other methods. 

Although the second alternative is more efficient and looks promising, it will not be taken into account in this study, as it will influence the combustion process and might be more difficult to retrofit to existing facilities. The calculated equipment costs only consist of the membrane costs and compressors/expanders, but are multiplied with an installation factor. The capital and operational costs adjusted with the parameters used in this study are shown in Tables 2.15 and 2.16. 

In June 1966, MIL-S-38130 was revised. Revision A to the specification once again expanded the scope of the SSP by adding a system modernization and retrofit phase to the defined life-cycle phases. This revision further refined the objectives of an SSP by introducing the concept of maximum safety consistent with operational requirements. On the engineering side, MIL-S-38130A also added another safety analysis the Gross Hazard Study (now known as the Preliminary Hazard Analysis). This comprehensive qualitative hazard analysis was an attempt to focus attention on hazards and safety requirements early in... 

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