Fuel gas conditioning systems

In LNG plants where gas turbines are used, OEM provides Fuel Gas Conditioning Systems (FGCS) with temperature/pressure regulated and contaminant free fuel gas to Dry Low NOX turbines. 

However, emissions are highly variable and depend on gasifier type, feedstock, process conditions (temperature and pressure), and gas conditioning systems. For example, indirect gasification systems generate flue gas emissions from the combustion of additional fuel, char, a portion of the feedstock. 

These contaminants are produced in the gasification process as a result of the presence of small amounts of sulphur in the biomass feed. The most important of these is H2S, followed by COS. H2S is chemisorbed on catalyst surfaces, thereby blocking active sites in the catalytic gas conditioning systems and limiting fuel cell performance in power generation applications. The loss of catalytic activity resulting from sulphur contamination is usually reversible in the systems dealt with in this chapter removal of H2S from the fuel gas results in the restoration of catalytic activity to the original level. 

As membrane-based fuel gas conditioning technology gains credibility, opportunities to compete with low-temperamre condensation or to provide membrane-augmented hybrid systems should open up. 

Validation and Application. VaUdated CFD examples are emerging (30) as are examples of limitations and misappHcations (31). ReaUsm depends on the adequacy of the physical and chemical representations, the scale of resolution for the appHcation, numerical accuracy of the solution algorithms, and skills appHed in execution. Data are available on performance characteristics of industrial furnaces and gas turbines systems operating with turbulent diffusion flames have been studied for simple two-dimensional geometries and selected conditions (32). Turbulent diffusion flames are produced when fuel and air are injected separately into the reactor. Second-order and infinitely fast reactions coupled with mixing have been analyzed with the k—Z model to describe the macromixing process. 

Interstate pipelines also use computer simulation programs to calculate pipeline capacity, pressures, horsepower, fuel and other physical characteristics and properties of their systems. Using this information and incorporating variables such as ambient temperatures, facility outages, and changes in market patterns, transmission companies can run daily studies to determine how much natural gas their systems will deliver under expected operating conditions. 

A typical simulation result is shown in Fig. 3. Under the given conditions, the concentration of fuel gas in bulk phase at the exit (Fig. 3a) is zero and the concentration of evaporative fuel gas at solid phase (Fig. 3b) at the exit did not reach the equilibrium concentration of activated carbon during adsorption. These results indicate that the canister of ORVR system is properly designed to adsorb the evaporative fuel gas. The temperature changes in canister (Fig. 3 c) during the operation remains in the acceptable range. The test results for different weather conditions showed that the canister design in this study can fulfill the required performance. 

The validity of the model is tested against the experiment. A ISOOcc canister, which is produced by UNICK Ltd. in Korea, is used for model validation experiment. In the case of adsorption, 2.4//min butane and 2.4//min N2 as a carrier gas simultaneously enter the canister and 2.1//min air flows into canister with a reverse direction during desorption. These are the same conditions as the products feasibility test of UNICK Ltd. The comparison between the simulation and experiment showed the validity of our model as in Fig. 5. The amount of fuel gas in the canister can be predicted with reasonable accuracy. Thus, the developed model is shown to be effective to simulate the behavior of adsorption/desorption of actual ORVR system. 

The ORVR system is an important subsystem which reduces the contamination of evaporative fuel gas at gas station during the fueling. In this paper, a simulation model of adsoiption and desorption of evaporative fuel gas in canister of ORVR system is developed. From the comparison between the simulations and experiments, the validity of the developed model is verified and the dynamics can be predicted. This PDE model can be used to design the canister of ORVR system effectively for diverse climate and operating conditions. 

When compared with combustion systems, the fuel gas produced by gasifiers is lower in both volume and temperature than the fully combusted product from a combustor. These characteristics provide an opportunity to clean and condition... 

Since the airflow rate induced into the air-intake is dependent on the flight speed and altitude of the projectile, the mixture ratio of air and fuel gas must be adjusted accordingly. In some cases, the mixture may be too air-rich or too fuel-rich to bum in the ramburner, falling outside of the flammability limit (see Section 3.4.3), and no ignition occurs (see Section 3.4.1). In order to optimize the combustion in the ramburner under various flight conditions, a variable flow-rate system is attached to the gas flow control system. 

As shown in Fig. 14.24, a self-regulating oxidizer feeding mechanism is used to eliminate the liquid oxidizer pumping system. A flow of the pressurized fuel-rich gas generated in the primary combustor forces the oxidizer tank to supply the liquid oxidizer to the secondary combustor. Simultaneously, the fuel-rich gas is injected into the secondary combustor and reacts with the atomized oxidizer. The fuel-rich gas is injected from the primary combustor into the secondary combustor through the fuel gas injector under conditions of a choked gas flow. The pressure in the primary combustor is approximately double that in the secondary combustor. This system is termed a gas-pressurized system. 

Even comprehensive mechanisms, however, must be utilized with caution. The GRI-Mech fails, for instance, under pyrolysis or very fuel-rich conditions, because it does not include formation of higher hydrocarbons or aromatic species. Its predictive capabilities are also limited under conditions where the presence of nitrogen oxides enhances the fuel oxidation rate (NO f sensitized oxidation), a reaction that may affect unbumed hydrocarbon emissions from some gas-fired systems, for example, internal combustion engines. 

The gas-phase sulfur chemistry occurring in the front-end furnace of the Claus process is presumably similar to reactions occurring under fuel-rich conditions in combustion. However, in both systems the chemistry is quite complex and involves a number of unresolved issues. 

The SEPAREX system will recover over 90% of the hydrogen at a purity of 96+% for recycle, while increasing the heating value of the fuel gas from -550 BTU/SCF to -950 BTU/SCF. The projected flow rates and gas purities for the membrane separation are shown in Table II. Under the bone-dry feed conditions the cellulose acetate membrane is not affected by HCl. Special materials of construction and adhesives have been used in the fabrication of the spiral-wound elements to ensure their resistance to HCl in the gas streams. 

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