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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. Batch ractor.

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slide1
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.

courtesy reminder

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).

examples of typical noncatalytic gas solid reactions ngsr
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.

elements of the ngsr systems
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.

comparison with heterogeneous catalytic reaction system s
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.

general reactor behavior performance design
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.

slide7

Which quantities govern reactor behavior/performance.

What’s needed to relate output

to input of a reactor.

slide9

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 reactors
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).

slide11

Big bubble bed

Bubbling bed

Slugging

Turbulent bed

slide12

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.

historical g s systems employed explored at icpf

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.

disproportionation of potassium benzoate to terephthalate

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.

sublimation as a means of refinement of solid with the aid of the fluidized bed

- 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),

slide16

- 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.

the combustion of low grade coal in the fluidized bed fbc with so2 removal

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)

slide18

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).

slide19

Fluidized combustor

with SO2 removal

slide20

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 flue and fuel gas cleaning
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).

slide22

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).

slide23

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.

slide24

Pneumatic slide feeder

of solids

Laboratory, fluidized, high

temperature reactor

slide25

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.

slide26

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).

slide29

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.

slide30

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.

slide31

Higher pressure,

elevated temperature,

fluidized reactor

slide32

Acknowledgments

The authors of this exposé ( M. Hartman and O. Trnka)

wish to appreciate the unflagging attention and interest

shown by the audience.

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