Gas Cleanup Systems

The typical steps for a gas cleanup system aim at particulate removal, sulfur removal, and NOx removal. This is achieved as follows  

Hot gas cleanup technology is currently under demonstration phase, but various demonstrations have not been successful so far. Wet scrubbing technology, though with a 

Fuel Coal Coal Pet coke/waste oil Vacuum residue Coal Lignite  

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The total emissions of hazardous air pollutants from a CGCC plant having wet cleanup are expected to be at least an order of magnitude lower than those achievable from a modem coal-fired steam plant (41). Metals removal in hot-gas cleanup systems is still under development. 

The particulates in the raw syngas is also significantly reduced due to multiple gas cleanup systems used to meet gas turbine manufacturers specifications. Particulate removal... 

Demkolec Buggenum Plant, Netherlands 253 MW Started operation in 1993 Shell gasifier - Initial problems encountered in gas cleanup system. Now operating with good availability. 

Hot Gas Cleanup System Breakage of ceramic candle filters and stress corrosion cracking in heat exchangers has also been reported. 

Gasifiers typically produce contaminants that need to be removed before entering the fuel cell anode. These contaminants include H2S, COS, NH3, HCN, particulate, and tars, oils, and phenols. The contaminant levels are dependent upon both the fuel composition and the gasifier employed. There are two families of cleanup that can be utilized to remove the sulfur impurities hot and cold gas cleanup systems. The cold gas cleanup technology is commercial, has been proven over many years, and provides the system designer with several choices. The hot gas cleanup technology is still developmental and would likely need to be joined with low-temperature cleanup systems to remove the non-sulfur impurities in a fuel cell system. For example, tars, oils, phenols, and ammonia could all be removed in a low-temperature water quench followed by gas reheat. 

The zero-emission energy recycling system (ZEROS) is a closed-loop thermal oxidation process that incinerates waste and recycles flue gas emissions for electrical co-generation. The technology uses a two-stage plasma torch combustion system, energy recovery system, and combustion gas cleanup systems. 

C.D. Livengood, H.S. Huang, M.H. Mendelsohn and J.M. Wu, Development of Mercury Control Enhancements for Flue-Gas Cleanup Systems, Proc. EPRI/DOE International Conference of Managing Hazardous and Particulate Air Pollutants, Toronto, Ontario, Canada, (1995). 

A low cost system for smaller communities is shown in Figure 1. It consists of a shredder to reduce the size of waste paper, a densification system to convert the shredded waste paper to a dense fuel "cube, the gasification reactor, a gas cleanup system, and an engine-generator to convert the gas to electrical power. 

In California (US), a 385 MW cogeneration facility comprising four gas turbine combined cycle trains is in operation [137]. Separate fuels such as natural gas, butane, and refinery fuel gas may be used. The refinery gas contains 800 ppm (by volume) sulfur. Sulfur was removed from the fuel before it was burnt in the gas turbine. The gas cleanup system includes a CO oxidation catalyst and downstream from this catalyst a SCR system. 

Flue gas from waste incinerators is composed of NO c, CO, HCl, HF, and SO2 Metals such as Cd, Hg, Zn, and Pb, and organic compounds such as dioxines and furanes are also observed. The flue gas cleanup system downstream a waste incinerator is comparable to that of a power plant. Again, a number of locations of SCR may be distinguished leading to flue gases with different compositions. These are sulfur, alkaline metals, HCl, HF, dioxines and furanes containing gases with no dust, flue gas without sulfur and dust, and clean flue gas. 

Develop a more detailed process flow schematic with a complete gas cleanup system. 

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