National Library of Latvia, Riga 1989-in progress

[Early Conceptual Sketch], untitled. Digital image only of blue ink sketch on tracing paper, initialed

National Library of Latvia, Riga 1989-in progress

[Early Conceptual Sketch], untitled. Digital image only of blue ink sketch on tracing paper, initialed

National Library of Latvia, Riga 1989-in progress

[Conceptual Sketches], untitled. Digital image only of four black ink sketches on graph paper, initialed

National Library of Latvia, Riga 1989-in progress

[Conceptual Sketches], untitled. Digital image only of four black ink sketches on graph paper, initialed

National Library of Latvia, Riga 1989-in progress

[Conceptual Sketch], untitled. Digital image only of black and blue ink sketch on tracing paper, initialed

National Library of Latvia, Riga 1989-in progress

[Conceptual Sketches], untitled. Digital image only of black and blue ink sketches on tracing paper with marker coloring, initialed

National Library of Latvia, Riga 1989-in progress

[Conceptual Sketches], untitled. Digital image only of two black and blue ink sketches on tracing paper with marker coloring

National Library of Latvia, Riga 1989-in progress

[Conceptual Sketch], untitled. Digital image only of black and blue ink sketch on tracing paper with marker coloring

National Library of Latvia, Riga 1989-in progress

[Conceptual Sketches], untitled. Digital image only of two black ink sketches on tracing paper with marker coloring

Mathematics and logic for digital devices.

Mode of access: Internet.

A dynamic mathematical model for sequential leach bed anaerobic digestion of organic fraction of municipal solid waste

A mathematical model that describes the operation of a sequential leach bed process for anaerobic digestion of organic fraction of municipal solid waste (MSW) is developed and validated. This model assumes that ultimate mineralisation of the organic component of the waste occurs in three steps, namely solubilisation of particulate matter, fermentation to volatile organic acids (modelled as acetic acid) along with liberation of carbon dioxide and hydrogen, and methanogenesis from acetate and hydrogen. The model incorporates the ionic equilibrium equations arising due to dissolution of carbon dioxide, generation of alkalinity from breakdown of solids and dissociation of acetic acid. Rather than a charge balance, a mass balance on the hydronium and hydroxide ions is used to calculate pH. The flow of liquid through the bed is modelled as occurring through two zones-a permeable zone with high flushing rates and the other more stagnant. Some of the kinetic parameters for the biological processes were obtained from batch MSW digestion experiments. The parameters for flow model were obtained from residence time distribution studies conducted using tritium as a tracer. The model was validated using data from leach bed digestion experiments in which a leachate volume equal to 10% of the fresh waste bed volume was sequenced. The model was then tested, without altering any kinetic or flow parameters, by varying volume of leachate that is sequenced between the beds. Simulations for sequencing/recirculating 5 and 30% of the bed volume are presented and compared with experimental results. (C) 2002 Elsevier Science B.V. All rights reserved.

Mathematical modelling

The development of a new process model of cement grinding in two-stage mills is discussed. The new model has been used to simulate cement grinding and predicting mill performance in open and closed circuit configuration. The new model considered the two-compartment mill as perfectly mixed slices in series. The breakage rate function uses the back calculation technique to determine offline using drop weight and abrasion tests.