Parties involved in the course of time: M. Hartman, K. Svoboda, O. Trnka, V. Veselý,

1. Notes on the very commencement of the research and development in the area of noncatalytic gas-solid reaction systems at the ICPF Prague Parties involved in the course of time: M. Hartman, K. Svoboda, O. Trnka, V. Veselý, M. Pohořelý, M. Čárský, J. Pata, J. Kocurek and others.

2. Batch ractor Plug flow reactor Mixed flow reactor Courtesy reminder Each one of us tends to construct his own biased model of reality by highlighting some experience (significant) and neglecting other (irrelevant).

3. Examples of typical noncatalytic gas-solid reactions (NGSR) Combustion: C(s) + O2(g)  CO2(g) Gasification: C(s) + H2O(g)  CO(g) + H2(g) SO2-removal: CaO(s) + SO2(g) + 0.5 O2  CaSO4(s), incineration of solid wastes, calcination, H2S-removal, etc., etc.

4. Elements of the NGSR systems · Mass transfer between single particles and gas stream. · Diffusion of gaseous components through a solid matrix (pores) and solid state diffusion. · Sorption and chemical reaction. · Heat transfer. · Textural changes brought about by the chemical reaction and sintering.

5. Comparison with heterogeneous catalytic reaction systems The most striking difference(s): - NGSRs are rather more intricate due to the direct participation of the solid in the reaction. - The texture of the solid changes as the reaction goes on. - NGSR systems are inherently transient (of unsteady nature). - Analysis involves an additional dimension-time.

6. General reactor behavior / performance / design is governed by several interrelated quantities: - the flow pattern and contacting gas with solid - kinetics: chemical reaction, transport phenomena, (heat & mass transfer). Thermodynamics and mechanical design must also be considered.

7. Which quantities govern reactor behavior/performance. What’s needed to relate output to input of a reactor.

8. Reliability of the reactor prediction and design.

9. The pragmatic approach in chemical reaction engineering: - abstract from the complexity of the real system and to substitute a more or less idealized situation / model - that is more amenable to analysis. The Exxon model fluid cracking unit

10. Basic types of G-S reactors Six broad types of contactors: 1. Packed (fixed, static) beds (PB). 2. Bubbling fluidized beds (BFB). 3. Turbulent fluidized beds (TFB). 4. Circulating fluidized beds (CFB). 5. Moving beds (MB). 6. Rotating kilns (RK).

11. Big bubble bed Bubbling bed Slugging Turbulent bed

12. Advantages of FB - The rapid mixing of solids leads to near isothermal conditions. - The liquidlike flow of particles. - Heat and mass transfer rates are high. Disadvantages of FB - Limited understanding of the complex physics of fluidization. - The erosion, entrainment of fines, bypassing.

13. Commercial blast furnace Historical G-S systems employed / explored at ICPF What for? As needed steps in the developed new technology of terephthalic acid (TA). When? In the 1960s, early 1970s.

14. 400oC, 1 MPa 2 C6H5COOK(s) C6H4(COOK)2(s) + C6H6(g) Cd, Zn, CO2 m.p. 425 oC m.p. > 550 oC Disproportionation of potassium benzoate to terephthalate (F. Kaštánek, A. Zemek, J. Kratochvíl, et al.) - performed in a tubular reactor (MB) with a mixer, - plagued with mechanical problems, - the formation of unwanted humines, - a peculiarity: always starts at the centre of pellets and spreads outwards, - discontinued.

15. - originated as a wanted operation in the TA process. The sublimation and thermal decomposition: 350ºC C6H4(COONH4)2(s) C6H4(COOH)2(g) + 2 NH3(g) N2; H2O Sublimation as a means of refinement of solid with the aid of thefluidized bed (J. (P.) Vítovec, J. Smolík, J. Kugler, A. Haklová, Z. Říha, and others) - has to be accompanied by a condensation / solidificationstep (at 150oC), - the inert bed material: corundum particles (exhibit a high thermal conductivity),

16. - a sublimation – condensation pilot plant was designed and erected, - the excellent outcome of R & D, a number offoreign patents granted, - very efficient process also for other materials (e.g., for phthalanhydride and anthraquinone), - later on, the activities expanded greatly in different directions.

17. Workplace In the Department of Chemical Reactors with F. Kaštánek and J. Čermák as the then Heads. Period of time From the early 1970s till the 1980s. The combustion of low-grade coal in the fluidized bed (FBC) with SO2 – removal (J.Beránek, V. Havlín, L. Foršt, B. Čech, V. Malaník, H. Kohoutová, J. Pata, V. Veselý, M. Čárský, J. Kocurek, and many others)

18. Final aim The conceptual design, construction and operation of a prototype of the commercial, fluidizedboiler withdesulfurization. Status and characteristics - The application – oriented project. - External, strong, influential partners: VŠB Ostrava, SONP Kladno, strojírny Tlmače. - Financing from the State plan of science & engineering development (SP RVT).

19. Fluidized combustor with SO2 removal

20. The attractive features of the FBC - The relatively low operating temperature (800 – 950oC). - Low-value fuels (coals) can be burned. - SO2 produced during combustion may be captured by adding limestone or dolomite into the bed. Final outcome of the project -A smaller commercial / production boiler with all accessories erected at Trmice (N. Bohemia) and tested. - The operational principles found feasible, but the machinery assessed as overly complicated. - Further development discontinued.

21. NGSR systems important for the flue and fuel gas cleaning - The work commenced as a tiny appendix to the big „Fluidized combustion with desulfurization“ project (J. Beránek). - On a small scale only: with a laboratory or bench-scale apparatus. Harmful gaseous pollutants of interest SO2(SO3), H2S, COS, NOx. Solid reactants (sorbents) CaO, MgO, CaO.MgO, Na2CO3 (active soda).

22. Precursors: - a host of limestones and dolomites of different origin from Bohemia & Moravia, - (waste) magnesite (Slovakia), - hydrated lime (Ca(OH)2), - calcareous muds, - NaHCO3. The conditions of reaction (sorption) Under ambient pressure, mostly at high temperature: 700 – 1000oC. In an oxidizing environment (SO2 from flue gas), in a reducing one (H2S from fuel gas).

23. Experimental facilities developed and employed - A high-temperature, differential, fixed-bed reactor for the kinetic studies. - A high-temperature, fluidized-bed, bench-scale unit for the reactor performance studies: the batch, continuous, or semi-cont. mode of operation. Crucial problems: low rate feeding of solids, heat resistant materials. - Cold, transparent (glass) fluidization columns for the hydrodynamic studies with different fluidized beds.

24. Pneumatic slide feeder of solids Laboratory, fluidized, high temperature reactor

25. Topics / subjects investigated ·The thermodynamic constraints on some reactions, e.g., sorption of SO2 by MgO, that of H2S / COS by CaO (the competition with CO2 in fuel gas). ·The changes (often dramatic) in sorbent texture caused by the „cleaning“ reaction; with the aid of P. Schneider, D. Tomanová, O. Šolcová et al.; the sintering of nascent (fresh sorbent). ·The kinetics studies and kin. modeling: - the reduction in porosity, - intraparticle transport, - chemical reaction.

26. the gas phase C X >>  the solid phase ·The model equations (PDE) are inherently „stiff“ : Solution of this and other computational problems developed by O. Trnka (then in the Computing Center).

28. Amongst The 100 Most Cited Articles in AIChE Journal History

29. Thermal decompositions in the fixed and fluidized bed · Hydronium jarosite, H3OFe33+(SO4)2(OH)6; in the elimination of iron from technol. polymetallic solutions. ·Dehydratation of sodium carbonate hydrates: Na2CO3 . 10 H2O, Na2CO3 . H2O; to produce effective sorbents, e.g., for NOx. A joint project with E. Erdös. ·Decomposition kinetics of Ca, Mg-hydroxides and the sintering of the oxides, to achieve high reactivity and special textural properties of the oxides; with the aid of O. Šolcová and H. Součková et al.

30. Combustion of liquid fuels in the fluidized bed · Formation of NOx in FBC: the conversion of the fuel-bound nitrogen to NO2 and NO. · Disposal of waste oils in a rolling mill in Chomutov. Analysis of the pressure fluctuations within the FB · An efficient means of monitoring the FB behavior, particularly at elevated temperature. · Started with the participation of J. Drahoš, K. Selucký, and M. Punčochář.

31. Higher pressure, elevated temperature, fluidized reactor

32. Acknowledgments The authors of this exposé ( M. Hartman and O. Trnka) wish to appreciate the unflagging attention and interest shown by the audience.