Coal gasifier

Hot Corrosion. Hot corrosion is an accelerated form of oxidation that arises from the presence not only of an oxidizing gas, but also of a molten salt on the component surface. The molten salt interacts with the protective oxide so as to render the oxide nonprotective. Most commonly, hot corrosion is associated with the condensation of a thin molten film of sodium sulfate [7757-82-6], Na2S04, on superaHoys commonly used in components for gas turbines, particularly first-stage turbine blades and vanes. Other examples of hot corrosion have been identified in energy conversion systems, particularly coal gasifiers and direct coal combustors. In these cases the salt originates from alkali impurities in the coal which condense on the internal... 

There are essentially three types of coal gasifiers moving-bed or countercurrent reactors fluidized-bed or back-mixed reactors and entrained-flow or plug-flow reactors. The three types are shown schematically in Eigure 2. 

Background Indirect coal liquefaction differs fundamentally from direct coal hquefaction in that the coal is first converted to a synthesis gas (a mixture of H9 and CO) which is then converted over a catalyst to the final product. Figure 27-9 presents a simplified process flow diagram for a typical indirect coal hquefaction process. The synthesis gas is produced in a gasifier (see a description of coal gasifiers earlier in this section), where the coal is partially combusted at high temperature and moderate pressure with a mixture of oxygen and steam. In addition to H9 and CO, the raw synthesis gas contains other constituents (such as CO9, H9S, NH3, N9, and CHJ, as well as particulates. 

Status of Indirect Liquefaction Technology The only commercial indirect coal liquefaction plants for the production of transportation fuels are operated by SASOL in South Africa. Construction of the original plant was begun in 1950, and operations began in 1955. This plant employs both fixed-bed (Arge) and entrained-bed (Synthol) reactors. Two additional plants were later constructed with start-ups in 1980 and 1983. These latter plants employ dry-ash Lurgi Mark IV coal gasifiers and entrained-bed (Synthol) reactors for synthesis gas conversion. These plants currently produce 45 percent of South Africa s transportation fuel requirements, and, in addition, they produce more than 120 other products from coal. 

Fig. 7.41 A typical coal gasifier atmosphere at 871 °C plotted in the M-O-S thermodynamic stability diagram for elements commonly present in stainless steels and high temperature alloys...

In operating a fluidized bed reactor such as a fluidized bed coal gasifier, fine particles tend to be elutriated from the fluidized bed. The elutriated fines, if not recovered, represent a significant carbon loss and thus a significant loss of reactor efficiency. In actual industrial practice, the fines are recycled back to the fluidized bed for further consumption. The location of the fines reinjection point into the fluidized bed reactor is important in order to maximize the consumption of fines in each pass. Otherwise, the fines will build up in the recycle loop and increase the heat load of the reactor operation. The fines reinjection location is selected to maximize the fines residence time in the bed and to provide an conducive environment for consumption, such as high temperature and an oxidizing atmosphere. 

The Texaco gasification process, currently owned by GE, is also of the EF type. A main difference with the aforementioned technologies is that the fuel is fed as a water slurry, whereas Koppers-Totzek- and Shell-based coal gasifiers use some steam. 

Conceptual flowsheet depicting integration of various units in the calcium looping processes for H2 generation in typical coal-gasifier facility. 

Among the natively fluorescent compounds determined by the POCL reaction are PAHs in different matrices such as coal tar [100] and biomass emissions [101], and amino-PAHs in shale oil, coal oil, and coal gasifier tar [102], Nitro-PAHs have no fluorescent properties, but have been reduced online (either pre-or postcolumn) to the corresponding amino-PAHs [103], The two fluorescent drugs dipyridamole and benzydamine have been determined in rat plasma by... 

CPG [Clean Power Generation] A version of the IGCC process which incorporates the Texaco coal gasifier. Developed and offered by Humphreys and Glasgow. 

Typical operating characteristics of coal gasifiers are as follows ... 

Like natural gas, the producer gas from coal is a clean fuel. Additionally, it is a rich source of chemicals. Coal-derived gas can also be recombined into liquid fuels, including high-grade transportation fuels, and a range of petrochemicals that serve as feedstock workhorses in the chemicals and refining industries. In contrast to conventional combustion, carbon dioxide exits a coal gasifier in a concentrated stream rather than diluted in a high volume of flue gas. This allows the carbon dioxide to be captured more effectively and then used... 

Avian leukosis virus, 3 136 Aviation gasoline, 23 666 Aviation turbine fuel, from coal gasifier syngas, 6 778 Avidin, 25 800 Avidity constant, 14 137 Avionics, with fiber-optic smart structures, 22 156-157... 

Diesel exhaust, 10 60-61 health effects of, 12 421 Diesel fuel, 12 420-13 13 668 from coal gasifier syngas, 6 7780 cold temperature properties of, 12 423 manufacture of, 12 426-429 requirements for, 12 421—426 specifications for, 12 426t... 

Biomass gasification processes are in the demonstration phase. Biomass can also be gasified together with coal. Royal Dutch/Shell has commercially demonstrated a 25/75 biomass/coal gasifier. 

FuelCell Energy is a partner with Versa Power Systems, Nexant, and Gas Technology Institute to develop more affordable fuel-cell-based technology that uses synthesis gas from a coal gasifier. The key objectives include the development of fuel cell technologies, fabrication processes, and manufacturing capabilities for solid oxide fuel cell stacks for multi-mega-watt power plants. 

Compared to conventional combustion, carbon dioxide exits a coal gasifier in a concentrated stream instead of a diluted flue gas. This allows the carbon dioxide to be captured more easily and used for commercial purposes or sequestered. 

Figure 2. Schematic of moving-bed coal gasifier with typical reaction temperature...

Figure 4. Schematic of entrained flow coal gasifier with typical reactor temperature...

---