Artikkelit kirjoittajalta Hannu Venäläinen
Termogravimetrian kaytto kiinteiden polttoaineiden tutkimuksissa. Osa VIII. Massan ja lampötilan nostonopeuden vaikutus kineettisten suureiden arvoihin.
English title: The usability of thermogravimetry in fuel research. Part VIII. The effect of mass and temperature rate on the values of kinetic quantities in the thermogravimetry.
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We have investigated the influence of the sample mass and the temperature rate on the values of thermogravimetric quantities.
The substances used were powdered willow dust and calcium oxalate, since willow dust represents a relatively homogenous natural material whereas calcium oxalate is a very common reference material in thermogravimetric studies.
The temperature rate was varied from 0.5 °C • min-1 up to 100 °C • min-1 and the masses were ranging from 10 mg to 420 mg.
It is a widely adapted impression that a relatively large masses (several hundred milligrams) and a slow temperature rate (optimum 3 °C • min-1 give the best experimental repetition and correct results.
We conclude, however, that the variation in sample masses and in temperature rate in this experiment had no significant influence on. the kinetic quantities computed.
The deviations originate from the differences in the instrumental technique and this assesses a requirement for the improved instrumentation before the mathematical relationships between various quantities can be established.
Furthermore, the neglible small effect of the reaction order on the kinetic quantities was observed. This was rather surprising, because it was only partly expected due to the formulation of the basic expressions.
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Tummavuori,
Sähköposti:
ei.tietoa@nn.oo
- Venäläinen, Sähköposti: ei.tietoa@nn.oo
- Nyrönen, Sähköposti: ei.tietoa@nn.oo
Termogravimetrian käyttömahdollisuudet polttoainetutkimuksessa. Osa VI: Kuuman ja kylmän auman turpeen pyrolyysin kinetiikasta.
English title: The usability of thermogravimetry in fuel research. Part VI: On the kinetics of the pyrolysis of the peat in the stockpiles with and without the self-heating tendency.
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Olemme tutkineet termogravimetristen suureiden merkitystä määritettäessä kuuman auman (A) ja kylmän auman (B) välisiä eroja.
Totesimme, että reaktiokineettiset suureet poikkeavat huomattavasti toisistaan, mikä voidaan varsin selvästi todeta kuvasta 1., josta ilmenee kuuman auman reaktioiden nopeuksien huomattava ero eri kaasuatmos-fääreissä tapahtuvissa reaktioissa.
lnfrapunaspektroskopia paljastaa myös sen tunnetun asian, että hydrolysoituvien aineiden määrä vaikuttaa huomattavasti aumojen itsepalamiseen.
Näitä alustavia tutkimuksia on tarkoitus jatkaa ensi tuotantokautena siten, että pystyisimme suoraan kenttänäytteestä ennus-tamaan auman itsepalamisominaisuuksia. Myöskin tältä alueelta tehdyt alustavat kokeet ovat olleet rohkaisevia.
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Tummavuori,
Sähköposti:
ei.tietoa@nn.oo
- Venäläinen, Sähköposti: ei.tietoa@nn.oo
- Nyrönen, Sähköposti: ei.tietoa@nn.oo
Termogravimetrian käyttömahdollisuudet polttoainetutkimuksissa. Osa V. Polttoaineiksi soveltuvien materiaalien pyrolyysin kinetiikasta.
English title: The usability of the thermogravimetry in fuel research. Part V. On the kinetics of the pyrolysis of materials suitable for fuel.
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This work completes our previous thermo-gravimetric investigations of domestic solid fuels. In this part, we have mainly concentrated on the pyrolysis of less common fuels e.g. straw, stumps and rejected, old railway sleepers. These cannot, of course, be regarded as significant fuel sources but locally and we wanted to show that the kinetics of their pyrolysis shows no exceptional behaviour as compared with previous materials.
Two peat samples were investigated because they differ from the other peat samples by their kinetic properties.
The straw ash, however, has a surprisingly low melting point, which can be detected from the TG-curves.
The utilization of used railway sleepers needs additional investigations, because the impregnating substances seem to evaporate in the course from the beginning to the end of the combustion. The safe use of the railway sleepers provides the determination of the toxicity of these substances.
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Tummavuori,
Sähköposti:
ei.tietoa@nn.oo
- Venäläinen, Sähköposti: ei.tietoa@nn.oo
- Nyrönen, Sähköposti: ei.tietoa@nn.oo
Termogravimetrian käyttömahdollisuudet polttoainetutkimuksissa. Osa IV. Paineen alentamisen vaikutus pyrolyysiin.
English title: The usability of the thermogravimetry in fuel research. Part IV. The effect of the reduced pressure on the pyrolysis.
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In this article we survey the pyrolysis of some solid domestic fuels in the lowered pressure, which completes the picture of the pyrolysis. Also, the possible comparison between the pyrolysis of the domestic fuels and the research methods have been rendered. The lowered pressure has a significant effect on the pyrolysis, because part of the polymerization and the coking are hindered. Up to the 650 K the pyrolysis seems to occur as in the nitrogen gas but thereafter no coking appears but the thermal decomposition proceeds. The remaining part of the reaction equals to the ash amount obtained after the reaction in the mixed gas. It is also obvious, that the particle size plays an important role in the pyrolysis in the lowered pressure. This can be seen from the inconsistent results presented in the literature.
The substances under investigation are mixtures of several organic compounds whose composition or even an average molecular mass is unknown. The calculation methods employed here are based on the approximations which are valid for the simple reactions of the compounds with known structures. Their application to the unknown reactions is strongly criticized.
If we perform the measurements in equal conditions and interprete the results as pseudo constants, they have, however, significance if the average properties of the pyrolysis of different substances are compared.
Finally, since the pyrolysis of the organic matter completely occurs in the lowered pressure, this may have meaning when the refining processes are developed.
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Tummavuori,
Sähköposti:
ei.tietoa@nn.oo
- Venäläinen, Sähköposti: ei.tietoa@nn.oo
- Nyrönen, Sähköposti: ei.tietoa@nn.oo
Termogravimetrian käyttömahdollisuudet polttoainetutkimuksissa. Osa III. Kiinteiden polttoaineiden pyrolyysin kinetiikan vertailua.
English title: The usability of the termogravimetry in fuel research. Part III. Comparison of the kinetics of the pyrolysis of solid fuels.
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In this work we have investigated the possibilities of the thermogravimetry (TG) to be applied to the peat research as well as to the rapid quality control of the peat products. It is shown, that the moisture content, the volatile matter and the ash content of the peat can be easily determined from the TG curves. Further, the pyrolysis
of the peat in various atmospheres can be investigated. The effect of the temperature rate and the carbonization time to the coke yield was also a subject of this study. Further investigations involve the calculations of the rate constants and the activation energies. Also, the products during the pyrolysis are of interest.
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Tummavuori,
Sähköposti:
ei.tietoa@nn.oo
- Venäläinen, Sähköposti: ei.tietoa@nn.oo
- Nyrönen, Sähköposti: ei.tietoa@nn.oo
Termogravimetrian käyttömahdollisuudet polttoainetutkimuksissa. Osa II. Eri turvelajien pyrolyysin kinetiikasta.
English title: The usability of the thermogravimetry in fuel research. Part II. On the kinetics of different peat types.
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The research work of the pyrolysis of the fossil fuels before the increase of the oil consumption was mainly directed to the tar, coke and gas obtained from the coal and to their use as energy and material sources of the industry. The interest to the further investigations has revived with the increase in the oil price. This is shown, for instance, with the thermogravimetric investigations lately performed by several scientists. The thermogravimetric investigations of wood and its components are performed in order to improve the fire re-tardant properties of wood, but forgetting the possibilities to use wood as an energy source or to refine its pyrolysis products. The comparison between various investigations is difficult due to the different instrumental and technical methods involved. The sample materials differ markedly by the virtue of their geographical locations. This is why we have performed the investigations of some domestic solid fuels in equal conditions in order to get comparable results. During the pyrolysis peat acts as an inhomogenous material making it difficult to monitore the pyrolysis products without a careful selection of the starting material. The pyrolysis of willow, alder and birch in different conditions are very identical and the whole pyrolysis is quite simple, since e.g. the tar content is very low. The preparation of liquid fuels (e.g. methanol) from hard wood species is easier than from peat. Also, the low ash content of the wood in an advantage.Fig 4 shows that the organic components in the mixture pyrolyze independently.
The wet carbonization of peat makes it burn faster but pyrolyze slower.
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Tummavuori,
Sähköposti:
ei.tietoa@nn.oo
- Venäläinen, Sähköposti: ei.tietoa@nn.oo
- Nyrönen, Sähköposti: ei.tietoa@nn.oo
Termogravimetrian käyttömahdollisuudet polttoainetutkimuksessa. Osa I. Sovellutusmahdollisuuksista turvetutkimuksissa.
English title: The usability of the thermogravimetry in fuel research. Part I. On the applications in peat research.
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This study involves the determination of some kinetic parameters of the various peat samples. Also, the effect of the peat type and the degree of the humification to the kinetics of the pyrolysis was of interest. These experiments were performed both in the inert gas and in the air nitrogen gas mixture. The energy of the activation as well as the rate constant clarify the changes of the matter during the pyrolysis. These facts are met, if we want to distinguish the nature and the behaviour of the products formed in the pyrolysis.
The kinetic parameters were calculated
using two different methods, both giving the similar results. The reference substance employed was cellulose since it is one of the main components of the peat and its pyrolysis is well studied. We conclude, that the pyrolysis of the peat can be investigated assuming the first order kinetics.
Further, the differences between the peat types were considerable which leads to the fact, that the selection of the peat type reflects the gaseous products formed during the pyrolysis and is important e.g. in the gasification studies.
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Tummavuori,
Sähköposti:
ei.tietoa@nn.oo
- Venäläinen, Sähköposti: ei.tietoa@nn.oo
- Nyrönen, Sähköposti: ei.tietoa@nn.oo
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