Johannesburg 2007
PREFACE
The theme of the 24th Annual International Pittsburgh Coal Conference (PCC) focusing on “Coal – Energy, Environment and Sustainable Development,” covers wide spectrum of important topics on coal technology and environmental issues. The program of this year’s conference held in Johannesburg, South Africa, includes over 300 papers presented in 3 plenary, 54 oral and 4 poster sessions over three days. The presentations provide in-depth discussions in various areas encompassing combustion, gasification and environmental control technologies; hydrogen from coal; coal utilization by-products; materials, instrumentation, and controls; global climate change: science, sequestration, and utilization; synthesis of liquid fuels, chemicals, materials and other non-fuel uses of coal; Fischer-Tropsch Technology; coal chemistry, geosciences and resources; and coal production and preparation; as well as Coal and Sustainability.
The Plenary Sessions feature several keynote addresses by an international panel of coal industry and environmental issues experts. Speakers include: Pat Davies: CE of SASOL, South Africa; Roger Wicks: Head of Energy – Anglo American, South Africa; Dr. Steve Lennon: MD Resources and Strategy, ESKOM, South Africa; Christopher Higman: MD Syngas Consultants, United Kingdom; Professor Rafael Kandiyoti: Chemical Engineering, Imperial College London, United Kingdom; and Dr. David Harris: Theme Leader: Low Emissions Electricity, CSIRO, Australia.
This interactive CD-ROM serves as a permanent record of the Conference Proceedings and offers the reader a convenient means to retrieve technical papers and other information related to the conference. It is hoped that the technical and environmental issues presented at this Conference will serve to stimulate future dialogues for clean and environmentally friendly use of coal by the international communities to achieve the ultimate goal of improving the quality of life for all mankind.
On behalf of the Conference Advisory Board, Conference Committees, North West University (Potchefstroom Campus-South Africa), and the University of Pittsburgh, I wish to express my sincere appreciations to Sasol, Eskom, Exxaro Coal, and Angelo Coal for their generous sponsorship of the PCC in South Africa. My gratitude goes to Professor Shiao-Hung Chiang for his invaluable mentorship and continuous nurturing of the International Pittsburgh Coal Conference. My personal thanks go to Drs. Chris Reinecke and Johan van Dyk for inviting the PCC to South Africa and for their dedication and exceptional service to our Conference over the years. My personal gratitude goes to Professor Frans Waanders from North West University (Potchefstroom campus) for his tremendous help and hosting the PCC in South Africa. Ms. Brenda Pierce, Chair and Dr. Robert Beck, vice-Chair of the Advisory Board have provided the leadership in setting the organizational policies for the Conference. The Program Committee chaired by Gary Stiegel, Tarunjit Butalia, and Johan van Dyk; and assisted by Evan Granite is responsible for the Conference’s outstanding technical program.
My personal appreciations go to all session chairs, Conference participants, plenary speakers, authors/presenters, and members of the Advisory Board and the South African Steering Committee. The administrative support by the School of Engineering, University of Pittsburgh and the financial support of Pitt Award by CONSOL Energy, Inc. are gratefully acknowledged. Special thanks go to Mrs. Adrian Starke and Mr. Rob Toplak for their invaluable help throughout the conference. I wish to express my sincere appreciation to Mr. Yannick Heintz and Mr. Laurent Sehabiague for their consistent help and effort in preparing the CD-ROM Conference Proceedings and to Ms. Heidi M. Aufdenkamp for her kindness, effectiveness, proficient assistance and enthusiasm in managing the overall operation of the Conference.
Badie I. Morsi
Editor and Executive Director
University of Pittsburgh,
September 2007
GENERAL
Metallurgical fuel production from low-metamorphism coals after their chemical treatment
Artem Madatov, “Coral invest technology, Ltd.” (Ukraine)
It is known, that strong lamp metallurgical coke is produced at laminar coking process of coal charges which are blended from baking coals of medium stages of methamorphism (Сdaf = 80-87%). These coals account a few percents only from total coal production, are critical and expensive. High price of baking coals determines prime cost of coke and limits its production increase.
More than 90% of coal world’s supply fall at low-metamorphism coals (LMC) – lignite and candle coals. However, it is impossible to obtain strong lump metallurgical coke from such coals by means of traditional laminar coking process The reasons of this are high yield of the volatile matter with small molecular weight and absence of liquid nonvolatile substances (LNS) with medium molecular weight (200-300 c. u.). As a result, volatile matter leaves coal charge at the temperature much less (350С) than temperature of coal char single structure (450-500С). Plastic layer is not formed because of absence of liquid contact zone between coal grains and pyrolysis solid residue is disintegrated into powder.
In chemical-physical respect LMC are polymorphous tertiary structure (conglomerate), which is formed from molecular fragments with small molecular weight (primary structure). Properties of tertiary structure are determined by non- valency linkages between polar functional groups -electron donors (aromatic, aliphatic,
naphthenetic) groups and electron-seeking (carboxyl, carbonyl, hydroxyl and sulfide too) ones. At pyrolisis process of coal tertiary and secondary coal structure destruction starts with these linkages rupture at the temperature about 350С. This temperature, however, is higher than boiling-point of small molecular weight of by-products of LMC pyrolysis, which leaves coal charge quickly.
It was showed in works, that during metamorphism of coals at the temperature 250-320С chemical reactions of dehydration and decarboxylation and aromatic condensation reactions of coal organic structure natural conditions when volatile byproducts do not leave coal. They generate multinuclear naphthenetic and aromatic structures with medium molecular weight which correspond to gas, fat and coke coals. In that way, target of strong lamp metallurgical coke production from LMC consists in change of chemical mechanism of coal pyrolysis in order to generate LNS in adequate amount for forming of plastic layer (30%).
Put problem has been solved by means of conditions for chemical reactions of LMC dehydration and decarboxylation and aromatic condensation reactions at comparatively low temperature and pressure in order to such conditions could be introduced into industry. So, inexpensive catalysts, solvents and reagent for such reactions in liquid phase were found. We used aliphatic hydrocarbons as solvents, polyenes and aromatic hydrocarbons as reagents.
Experimental technique:
High-boiling solvent (boiling-point 350 0С), was prepared from large-tonnage industrial and domestic waste according special technology. Reagents, made of largetonnage industrial waste too with special catalysts were added in amount 10, 20, 30, 40 and 50% to lignite after predrying (moisture 15%). Then we added 20% solvent to lignite-reagent mixture and kept it 24 hours at 250-350 0С. Pyrolysis of lignite-reagent mixture was realized in stainless steel retort, heating rate was 1,5 0С/min. up to 900С. At this temperature charge was kept for 1 hour, cooled and elicited from retort. We caught and studied volatile matter according to standard method, made up a balance. Solvent was condensed together with coal-tar pitch and divided by means redistillation at 350С. Fixed residue was studied according to standard method, which used for coke study in laboratory environment. Analogous experiments was conducted with candle coal.
Plastic properties of chemical treated coals determined by Institute of Fossil Fuel (Russian Science Academy).
RESULTS
Fixed residue yield is showed in fig.1. It is obviously that yield maximum corresponds to 30% reagents addition. At that fixed residue of the process without reagents and catalysts addition shaped fine-dyspersated. But fixed residue with 10% addition shaped small-sized, with 20-50 % addition – lumpy.
Quality indexes of coke is showed in fig. 2 and 3.. Durability of coke increase naturally at reagents part increase up to 30%, then became stabilize.
Fig. 2. Quality indexes of coke from lignite-reagent mixtures.
Fig. 3. Quality indexes of coke from candle coal-reagent mixtures.
Yield of liquid pyrolysis by-products (except for mass of overhead solvent) is sowed in fig. 4. It was found that yield of liquid by-products rises sharply at addition more than 30% reagents. Qualitative analysis revealed presence of aromatic, aliphatic, naphthenetic hydrocarbons.
Fig. 4. Yield of liquid by-products from coal-reagent mixtures.
Change of plastic properties of treated lignite and candle coal are showed in fig. 5. and fig. 6. According to increase of reagents share up to 30% shrinkage x decreases but then increases. Plastic layer thickness уincreases up to 14 mm in lignite and 19 in candle coal at 30% reagents and more.
Fig. 5. Srinkage of coal-reagent mixtures.
Fig. 6 Plastic layer thickness of coal-reagent mixtures.
DISCUSSION
Formula, determined by approximation method, describes fixed residue yield from lignite- reagents mixture, has view:
Mc = 0,45Ml + 0,80Mr ,
where
Мc – fixed residue yield from mixture;
Мl – lignite share;
Мr – reagents share;
0,45 – fixed residue yield from lignite;
0,80 – reagents rate of use.
Formula, determined by approximation method, describes fixed residue yield from
candle coal – reagents mixture, has view:
Mc = 0,50Mcl + 0,80Mr
where
Мc – fixed residue yield from mixture;
Mcl – candle coal share;
Мr – reagents share;
0,50 – fixed residue yield from candle coal;
0,80 – reagents rate of use.
Reagents rate of use depends on chemical reactions type – in this case additive reactions – and is approximately equal carbon content in it. It means that 80% mass of reagents turns into coke and 20% – in volatile matter. As it follows from formulas, that at constant reagents rate of use 0,80 maximal reagents consumption is 30% from mixture
mass. Reagents surplus is not consumed for coke formation but it is decomposed and goes out together with volatile matter. This is a reason of liquid by-products yield increase. Therefore, reagents rate of use for coke formation is conditioned by chemical reaction ability of coal and depends on content of definite functional groups on coal organic mass.
Increase of lump coke strength at reagents addition is evidence of coal pyrolysis chemical mechanism change, generation of LNS and increase of plastic properties. Increase of plastic layer thickness у increases up to 14 mm in lignite and 19 in candle coal e.i.up to fat and coke level is a such evidence too. Probably, these changes are
result of decreas of decomposition reactions temperature, and consequently widening of temperature interval of coal plastic state. Strength of lump coke made of such coal allows use it as blast-furnace fuel.
Low coke yield from LMC comparatively to coal charge of traditional composition is obstacle of effective use in multicell coke heaters. So, new type of coke-oven (shaft furnace) for coal charge with low coke yield was developed and tested in experimentalindustrial variant. It is combined with processor for uninterrupted coal treatment with reagents. Its test result allowed to alculate, that prime cost production of 1 ton blastfurnace coke according new technology will be as 15-20% as less than on traditional one.
It is possible to use developed technology at existing coke plants without any changes in production process. Increased plastic properties of treated coals allows to add lean coal and rise coke yield up to usual level. In this case the plant will get additional profit thanks to exchange of expensive coals by cheap ones. Resources of wastes for solvents-reagents are more than 200 million tons per year, it allows to introduce into coke industry about 400 million tons of lignite and candle coal and 100 million tons of lean coal. Therefore, introduction of new technology will allow to
obtain 350-400 million tons of coke, 200-150 million tons liquid hydrocarbons and 150-175 billions m3 of gas annually.
RESUME
- Chemical treatment of LMC in liquid phase with reagents and catalysts allows to obtain metallurgical coke .
- Chemical treatment of noncaking coal increases coal plastic properties by means of chemical mechanism of their pyrolysis to generate LNS due to aromatic condensation promotion.
- Sintering coal properties increase up to fat and coke coals allows to save expensive coals, use lean coal in coking charge and compensate low coke yield from LMC.
- LMC chemical treatment process proceeds at atmospheric pressure andmoderate temperature, therefore, could be involved into coke industry easily.
- High yield of liquid small molecular weight by-products improves financial result of coking due to row materials for motor fuel production.
- Developed equipment for chemical treatment allows to process non-liquid wastes and get addition profit due to involve cheap coal into coke production.
