Dry-feed entrained-flow systems

The oxygen consumption is the highest for slurry-feed GE gasification and the lowest for the fluid-bed systems. Dry-feed entrained-flow systems and the E-Gas gasifier achieve values between these extremes. The oxygen consumption level for South African (SAf) coal is elevated compared to Pittsburgh No. 8 (Pitt 8) coal. 

The dry-feed entrained-flow gasifiers form a group in the very limited domain A. The new Siemens concept with radiant cooler overlaps with the standard Shell system and the two water-quench configurations from Siemens and Shell also overlap. The advanced concepts of GE and E-Gas (first stage) can also be found in domain A. The gasifier points only scatter due to different reactor heat losses and possible quench conversion. 

In the case of the E-Gas gasification, the first stages can also be displayed as distinct points, which are inside the slurry-feed entrained-flow domain for the standard system and inside the dry-feed domain for the enhanced system (entrained slagging transport reactor [E-STR]). The slurry point, which is located at the coal-H20 axis, represents the coal-water slurry that is introduced in the second stage. The overall mixing points, again, represent the outlet of the gasifier and can be found inside the fluid-bed domain. 

The dried pulverized coal system is quite complex the nitrogen from dense entrained flow may affect the subsequent chemical process. Thus, the CAPEX is much higher compared with a CWS feeding gasifier for methanol or other coal-to-chemicals plants. 

The feed system is an important choice for entrained-flow gasifiers. GE and E-Gas use a coal-water slurry compared with the dry-feed systems of Shell and Future Energy, which require lock hoppering. 

D4. We wish to wash an alumina solids to remove NaOH from the entrained liquid. The underflow from the settler tank is 20 vol % solid and 80 vol % liquid. The two solid feeds to the system are also 20 vol % solids. In one of these feeds, NaOH concentration in the liquid is 5 wt %. This feed s solid flow rate (on a dry basis) is 1000 k hr. The second feed has a NaOH concentration in the liquid of 2 wt %, and its solids flow rate (on a dry basis) is 2000 k h. We desire the final NaOH concentration in the underflow liquid to be 0.6 wt % (0.006 wt frac) NaOH. A countercurrent operation is used. The inlet washing water is pure and flows at 4000 k h. Find the optimum feed location for the intermediate feed and the number of equilibrium stages required. 

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