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Content archived on 2024-04-15

COMBINED DEWATERING AND SOLVENT EXTRACTION OF BITUMENS FROM PEAT

Objective

A COMPUTER ASSISTED DESIGN WILL BE MADE OF A CARVER-GREENFIELD TYPE PILOT PLANT TO PROCESS 100 TONNES MILLED PEAT PER WEEK. SUBSEQUENTLY PROCESS, CONSTRUCTION AND MAINTENANCE COSTS WILL BE ESTIMATED.
FOLLOWING COMPLETION OF THIS RESEARCH AN APPLICATION WILL BE MADE FOR A DEMONSTRATION GRANT UNDER DG XVII TO BUILD SUCH A PLANT.
The application of the Carver-Greenfield process to the dewatering of peat with concurrent solvent extraction of peat bitumens has been studied. Criteria for solvent selection included yield of bitumen and environmental acceptability, as well as physical considerations relevant to Carver-Greenfield process. A proprietary petroleum distillate, Shell white spirit, was found to have appropriate peat wetting and peat slurry rheological characteristics and extracted approximately 9% bitumen based on dry weight of peat. A plant was designed to dry 30000 tonnes of bog peat per annum from 50% to 1% moisture by weight.

Blends of peat bitumen with petroleum bitumen were found to show a propensity to harden on ageing. Mechanisms of age hardening are thought to involve polyesterifications with consequent increase in molecular weight.

The bitumen has been fractionated on the basis of solubility into wax, resin and asphaltere. These fractions were analysed chromatographically and spectroscopically and their rheological characteristics established. Species in the wax fraction were found to dominate the rheological behaviour of the bitumen.

The application of the Carver-Greenfield process to the dewatering of peat with concurrent solvent extraction of peat bitumens has been studied. Criteria for solvent selection included yield of bitumen and environmental acceptability, as well as physical considerations relevant to the Carver-Greenfield process. A proprietary petroleum distillate, Shell White Spirit, was found to have the appropriate peat wetting and peat slurry rheological characteristics and extracted approximately 9% bitumen based on dry weight of peat.

Using this data a plant was designed to dry 30000 tonnes of bog peat per annum from 50% to 1% by weight of moisture. The plant involves a total investment of 2.2 million and the manufacturing cost (including amortisation of the capital) of the crude bitumen is about 1180 per tonne. As the powdered peat is pyrophoric it would be appropriate to briquette it. If briquettes were made, with a selling price of 125 per tonne, then the total investment required is about 4.0 million and the manufacturing cost of the crude bitumen is effectively reduced to 880 per tonne.

The engineering properties of the blends of the peat bitumen with petroleum bitumen were evaluated but were found to show a propensity to harden on ageing, putting use as road binder constituents into doubt. Mechanisms of age hardening were investigated in terms of bitumen chemistry, and are thought to involve polyesterifications with consequent increase in molecular weight.

With a view to identification of alternative applications to road binders, the bitumen has been fractionated on the basis of solubility into wax, resin and asphaltene. These fractions were analysed chromatographically and spectroscopically and their rheological characteristics established. Species in the wax fraction were found to dominate the rheological behaviour of the bitumen.
THIS RESEARCH PROJECT IS DESIGNED TO DEVELOP AND OPTIMISE A PEAT DRYING PROCESS BASED ON THE CARVER-GREENFIELD SYSTEM TO :

A) INCREASE DEWATERING EFFICIENCIES;
B) EXTRACT PEAT BITUMENS;
C) DOUBLE THE CALORIFIC VALUE OF PEAT;
D) PRODUCE A SMOKELESS FUEL;
E) EASE PROCESS HANDLING OF PEAT;
F) REDUCE DUST EXPLOSIVE RISKS;
G) REDUCE TRANSPORT COSTS OF WET FUEL;
H) REDUCE COMMUNITY ENERGY COSTS;
I) CONSERVE FUEL DEPOSITS;
J) ACHIEVE CONSISTENT RESIDUAL MOISTURE CONTENT OF PEAT;
K) CREATE NEW EMPLOYMENT.

Topic(s)

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Call for proposal

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Coordinator

National Institute for Higher Education-Limerick
EU contribution
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Address
Plassey Technological Park
61 Limerick
Ireland

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