Experience from the Gasification of Greek Lignite in a Pilot Indirect Heat Rotary Kiln Gasifier

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1 NATIONAL TECHNICAL UNIVERSITY OF ATHENS SCHOOL OF CHEMICAL ENGINEERING CHEMICAL PROCESS ENGINEERING LABORATORY Professor G.P. Androutsopoulos Dr. Eng. K.S. Hatzilyberis Experience from the Gasification of Greek Lignite in a Pilot Indirect Heat Rotary Kiln Gasifier 1

2 New Reactor (Gasifier) Concept Allothermal (Indirect Heat) Gasifier for MHV gas production or Lime Enhanced Gasification for HyMet production under controlled atmosphere The selected reactor type is that of Rotary Kiln 2

3 Rotary Kiln offers: No particle size limitations either in the feed or during processing. Feed containing the full inherent moisture content. Reactor operation under a controlled atmosphere. Effectiveness of phase mixing. Control of solids hold-up and residence time. 3

4 First implementation of this concept: Pilot Plant in PPC under NATO-SFS Programme Director: G.P. Androutsopoulos 4

5 Second implementation and improvement of the concept: Pilot Plant in NTUA / Sch. Chem. Eng. Developed by: Professor G.P. Androutsopoulos and Dr. K.S. Hatzilyberis 5

6 The NTUA Rotary Kiln Gasifier Section View Head & Thermowell Solids Motion 6

7 Temperature Measurement System Longitudinal Configuration of Thermocouples Data Acquisition & Temperature Control System 7

8 The NTUA / CE full Gasification Unit 8

9 Flowsheet of the Gasification Plant The Basic Flowsheet of the Pilot Scale Gasifier and the Gas Cleaning and Handling Unit including the recently added equipment (in red color). 9

10 Gasification of Greek Lignite in the NTUA Pilot Rotary Kiln Gasifier Experiments with the use of partially pre-dried lignite. A minor feed-stream of inert gas (N 2 ) was also fed into the rotary kiln. Proximate Analysis of the Samples Maximum Internal Temperature of the Kiln Moisture Volatiles Ash Fix Carbon ( C) (% w/w) (% w/w) (% w/w) (% w/w) Megalopolis Greek Lignite has raw moisture content ~60% w/w 10

11 Maximum Conversion (%) Gas Composition (% v/v) Internal LHV Temperature of the Kiln DAF * Lignite Volatile Matter Fix Carbon H 2 CO CH 4 CO 2 N 2 Tars ** *** (MJ/Nm 3 ) ( C) *DAF = Dry Ash Free ** As total dissolved elemental carbon (Total Carbon-TC), in mg/l, in the wet scrubber drainage aqueous stream. *** LHV = Lower Heating Value. Maximum Internal Temperature of the Kiln Steam / C * (mol/mol) CaO / C ** (mol/mol) MgO / C ** (CaO + MgO) / C ** ( C) *Steam is derived from the inherent moisture content of the raw lignite ** CaO and MgO are derived from the natural mineral matter of the raw lignite 11

12 Tars determination in the aqueous drain solution of the wet scrubber. Samples were received during the start-up state of the 700 C run. No Maximum Internal Temperature of the Kiln ( C) Total Dissolved Elemental Carbon (mg /L ) From the 700 C measurement (steady state conditions) and taking into account scrubber water flow (~600 L/h) and dry product gas flow (~800 NL/h) it is calculated ~86 mg of C / NL of dry product gas. 12

13 Theoretical Modeling of an Allothermal Rotary Kiln Gasifier A theoretical model of allothermal rotary kiln gasifier has been developed. This model involves a scheme of parallel execution of the three basic processes (drying, pyrolysis and gasification). The mass and energy balances include literature kinetics for lignites pyrolysis (devolatilization) (Merrick, D. 1983, Fuel, 62, pp ) and gasification (Johnson, J.L. 1979, Kinetics of Coal Gasification, John Wiley & Sons). For the drying process is used a pilot-scale verified kinetic relationship that had initially developed in laboratory-scale TGA equipment, by Professor G.P.Androutsopoulos. 13

14 This theoretical model leads to a mathematical system of 14 differential equations with 14 independent functions (axial distributions of magnitudes along rotary kiln). The rest axial distributions and final values of magnitudes are derived from the above 14 independent functions. The predictions of the theoretical model are, in general, in sufficient agreement with the relevant experimental data. The results of the theoretical data show that, at the gasifier exit, the gas phase species are close to chemical equilibrium, but the same state cannot be verified for the reactions between the gas and the solid phase (active sites of char). The same results set the need for further laboratory-scale investigation of Greek lignites gasification kinetics. 14

15 Tmax=700 C T ( C) ,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 Tmax=877 C l = z / L Cconv., DAFconv. 1,0 0,9 0,8 0,7 0,6 0,5 DAF conv. 0,4 0,3 C conv. 0,2 0,1 0,0 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 l = z / L T ( C) ,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 l = z / L DAFconv. 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 l = z / L Ea=13 Ea=15 Ea=20 Ea=25,7 (L=3m) 15

16 Tmax=700 C y (mol/mol) (wet gas) 1,0 0,9 H 2 O (g) 0,8 0,7 0,6 0,5 0,4 N 2 0,3 0,2 H 2 0,1 CO 0,0 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 l = z / L y (mol/mol) (wet gas) 1,0E-01 CO 2 1,0E-02 CH 4 NH 1,0E-03 3 H 2 S C 1,0E-04 2 H 6 1,0E-05 1,0E-06 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 l = z / L Composition of dry gas (% mol/mol) T max = 700 C Measurement Prediction H 2 38,1 37,4 N 2 19,8 20,3 CO 24,2 23,7 CH 4 2,9 3,2 CO 2 15,0 14,7 Gas nitrogenous substances expressed as equivalent NH 3 Gas sulfurous substances expressed as equivalent H 2 S Gas hydrocarbons with C 2 expressed as equivalent C 2 H 6-0,4-0,2-0,1 16

17 Upgrading of High Moisture Low Rank Coal to Hydrogen and Methane C2H Upgrade RFC-CR Program executed by 11 European partners under the coordination of IVD / USTUTT and funded by the European Commission Research Fund for Coal and Steel (RFCS) (ex. European Community for Steel and Coal (ECSC)). 17

18 Scheme of the coal upgrading process C2H including lime enhanced steam gasification This method functions as a chemical energy transformation process, whereas lignite heating value is converted to clean chemical energy of H2. 18