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

Notes on the very Notes on the very commencement of the commencement of the

research and development research and development in the area of noncatalytic in the area of noncatalytic gas-solid reaction systems gas-solid reaction systems

at the ICPF Pragueat 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.

Courtesy reminderCourtesy reminder

Each one of us tends to construct his own biased model of reality by highlighting some experience (significant) and neglecting other (irrelevant).

Batch ractor Plug flow reactor Mixed flow reactor

Examples of typical noncatalytic Examples of typical noncatalytic gas-solid reactions (NGSR)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.

Elements of the NGSR systemsElements 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.

Comparison with heterogeneous Comparison with heterogeneous catalytic reaction systemcatalytic reaction systemss

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.

General reactor behavior / General reactor behavior / performance / designperformance / 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.

Which quantities govern reactor behavior/performance.

What’s needed to relate output to input of a reactor.

Reliability of the reactor prediction and design.

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

Basic types of G-S reactorsBasic 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).

Bubbling bed Big bubble bed

Turbulent bedSlugging

Advantages of FBAdvantages 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 FBDisadvantages of FB

- Limited understanding of the complex physics of fluidization.- The erosion, entrainment of fines, bypassing.

Historical G-S systems employed / Historical G-S systems employed / explored at ICPFexplored at ICPF

What for? As needed steps in the developed new technology of terephthalic acid (TA).

When?

In the 1960s, early 1970s.

Commercial blast furnace

Disproportionation of potassium Disproportionation of potassium benzoate to terephthalatebenzoate to terephthalate

(F. Kaštánek, A. Zemek, J. Kratochvíl, et al.)

400oC, 1 MPa 2 C6H5COOK(s) C6H4(COOK)2(s) + C6H6(g) Cd, Zn, CO2

m.p. 425 oC m.p. > 550 oC

- 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.

Sublimation as a means of Sublimation as a means of refinement of solid with the aid of refinement of solid with the aid of

thethe fluidized bedfluidized bed (J. (P.) Vítovec, J. Smolík, J. Kugler, A. Haklová, Z. Říha, and others)

- originated as a wanted operation in the TA process. The sublimation and thermal decomposition:

C6H4(COONH4)2(s) C6H4(COOH)2(g) + 2 NH3(g) 350ºC

N2; H2O

- has to be accompanied by a condensation / solidification step (at 150oC),

- the inert bed material: corundum particles (exhibit a high thermal conductivity),

- a sublimation – condensation pilot plant was designed and erected,

- the excellent outcome of R & D, a number of foreign patents granted,

- later on, the activities expanded greatly in different directions.

- very efficient process also for other materials (e.g., for phthalanhydride and anthraquinone),

The combustion of low-grade coal The combustion of low-grade coal in the fluidized bed (FBC) with SO2 in the fluidized bed (FBC) with SO2

– removal– removal

(J.Beránek, V. Havlín, L. Foršt, B. Čech, V. Malaník, H. Kohoutová, J. Pata, V. Veselý, M. Čárský,

J. Kocurek, and many others)

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.

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).

Final aim

The conceptual design,construction and operationof a prototype of the commercial, fluidized boilerwith desulfurization.

T1

T2

T9

T10

T5

T11

T8 T7

T4

T2

T5

T6

SAMPLINGPOINT

600 K

T3

T6

T9

T10

T11

T12T12

940 K

1000 K

1135 K

1300 K

1370 K

1230 K

590 K

Fluidized combustor with SO2 removal

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.

NGSR systems important for the NGSR systems important for the flue and fuel gas cleaningflue 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).

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).

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.

Laboratory, fluidized, hightemperature reactor

Pneumatic slide feederof solids

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.

· The model equations (PDE) are inherently „stiff“ :

Solution of this and other computational problems developed by O. Trnka (then in the Computing Center).

C X >>

the gasphase

the solidphase

Amongst The 100 Most Cited Articles in AIChE Journal History

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.

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.

Higher pressure,elevated temperature, fluidized reactor

AcknowledgmentsAcknowledgments

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

shown by the audience.