Makoto Kobayashi, Hiroyuki Akiho

Transcription

1 Performance Evaluation of Honeycomb Shaped Dry Desulfurization Sorbent in the Syngas Expected for Advanced Oxy-fuel IGCC Power Generation Plant. 8 th IFC on IGCC & XtL Technologies Makoto Kobayashi, Hiroyuki Akiho Central Research Institute of Electric Power Industry June 13,

2 Concept and basic design of oxy-fuel IGCC. O 2 -CO 2 blown gasification + Semi-closed cycle GT CO 2 is obtained by mist elimination of exhaust. Thermal efficiency is 44% LHV at transmission end. Dry Desulfurization Process 2

3 Three fixed-bed reactor sulfur removal system. 3

4 Pellet and honeycomb sorbent for sulfur removal. Pellet sorbent for lab. experiment. Good gas-solid contact. Large pressure drop across the bed Honeycomb sorbent Low pressure drop Easy installation for fixed bed reactor using unit cages. 4

5 Scope and objective of this study. The honeycomb sulfur sorbent is applied to syngas in a severe condition during plant start-up, while the gas turbine exhaust is not available. The sorbent was improved to retard carbon deposition in the sever condition. This study performs comparative evaluation of the former type sorbent and the improved sorbent in terms of sulfur removal, carbon deposition, and oxidative elimination of deposited carbon. 5

6 Fixed bed test apparatus for honeycomb desulfurization sorbent. T = 450 P = 0.98 MPa 6

7 Gas composition in the actual plant and experimental condition. (stream gasifier(outlet Dry(sulfur Cond.((A((, A Cond.((B((, B Dry(sulfur removal(with Severe Gentle removal* EGR condition** condition** temp.,8 C press.,8mpa H 2 O CO H gas8comp. R B,8bar 1 CO CH N O *Assuming8equillibrium8of8water8gas8shift8reaction **The8composition8was8compensated8according8to8the8pressure8difference. 7

8 Honeycomb sulfur sorbent installed in a quartz tube. gas flow gas flow These sorbents were evaluated under the condition across the carbon deposition boundary. 8

9 Chemistry related to sulfur removal. Boudouard reaction, carbon deposition 2CO!! CO!!+ C (1) 2 R B P CO2 P CO (2) water gas shift reaction CO + H 2 O!! CO 2!+ H 2 (3) R W P CO2 P H! P CO P H! O (4) Sulfidation of zinc ferrite ZnFe 2 O 4 + 3H 2 S + H 2 ZnS + 2FeS + 4H 2 O (5) Regeneration of spent zinc ferrite ZnS + 2FeS + 5O 2 ZnFe 2 O 4 + 3SO 2 (6) 9

10 Carbon deposition boundary determined for the pellet shaped, former sorbents. Carbon deposition map RW, gas composition parameter for water gas shift reaction RB, gas composition parameter for Boudouard reaction A B The carbon deposition boundary for the former type sorbent was determined experimentally as indicated by the red chain line. 10

11 Sulfur removal performance of the former type honeycomb sorbent. Carbon deposit caused performance degradation. Condition is much severe on honeycomb sorbent than the pellet sorbent. 11

12 Regeneration of the sorbent reacted under the condition A. Once deposited carbon accumulated on the sorbent, the carbon cannot be released during subsequent regeneration step. 12

13 Sulfur removal performance of the improved honeycomb sorbent. Carbon deposition was inhibited for the improved sorbent, even in the deposit region of the former sorbent. 13

14 Regeneration of the sorbent reacted under the condition A. The improved sorbent was not suffered from carbon deposition even in the severe condition. Thus, very slight amount of CO2 was released during subsequent regeneration step. 14

15 Spent honeycomb sorbents in condition A. gas flow gas flow The improved sorbent maintained the shape and structure of the honeycomb soundly. 15

16 Conclusion The former type sorbent was suffered from deteriorative structure collapse due to rapid carbon deposition in the severe condition. The improved sorbent could avoid the rapid carbon deposition in the severe condition. Slight amount of deposited carbon in the sorbent could be eliminated by the oxidation in the subsequent regeneration step. It was concluded that the improved sorbent can be used in a fixed bed reactor of the dry gas sulfur removal process. 16