Heat pump assisted distillation for the energy efficient separation of the liquid phase products from anaerobic digestion - LEVERHULME

This project is part of a wider research programme into biological routes for the synthesis of chemical products. A key element of this approach is the separation of the chemical products from the aqueous broths produced by the bioreactors/anaerobic digestors, which is commonly achieved via distillation.

Distillation is one of the most mature and widely used unit operations in the chemical process industries. It is an energy intensive separation process which accounts for about 40% of the total energy consumption of a typical chemical plant. Fossil fuels, such as petroleum and natural gas, are still the primary source of energy worldwide and they are largely responsible for the production of greenhouse gases contributing to global warming. This has led to intensified efforts to improve the efficiency of well-established processes and the development of new energy efficient and cost-effective process configurations.

In this project, the optimal design of distillation columns will be investigated that will be used to separate the liquid phase products from an anaerobic digester. In an anaerobic digester, organic waste such as food residue and animal manure is converted to useful chemicals in the absence of oxygen by the action of microorganisms. The liquid product generated by the digester will be made up of water and of the short chain organic acid and molecules. These substances, once separated, can be used as useful chemicals or upgraded into more useful forms. For instance, acetic acid can be used as a solvent or can be used as starting materials for many chemical reactions that can produce paints, plastics, and many other essential chemicals.

This project will investigate the use of heat pump assisted distillation technology, particularly vapour recompression in batch and continuous distillation of the liquid-phase anaerobic digestion products, with the aim of identifying the conditions that minimise energy consumption and maximise the use of electricity which can be sourced renewably. Among the heat integrated distillation techniques, vapour recompression distillation has emerged as one of the widely accepted schemes for continuous flow distillation. In this technique, the vapour coming from top of the column is compressed and then used to heat the bottom liquid. Although such an integrated configuration leads to significant energy savings, the coupling of heating and cooling requirements results in the reduction of available degrees of freedom as the condenser and reboiler duties cannot be manipulated independently. Such coupling also leads to feedback interactions and complexities in the dynamics of the system. In this project, a mathematical model of the heat pump assisted distillation column will be developed which can subsequently be used to simulate the distillation process and identify the key process parameters. A model based optimization of the process will also be carried out that will ensure high productivity while ensuring required purity and low energy cost. This study will provide theoretical support for design, optimization and scale-up of the distillation column used to separate the liquid phase from anaerobic digesters for sustainable production of chemicals and materials.

Selection will be made on the basis of academic merit. The successful candidate should have, or expect to have, an Honours Degree at 2.1 or above (or equivalent) in Chemical Engineering, Mechanical Engineering and Applied Mathematics or related areas.

Knowledge of process modelling, numerical methods and computer programming would be advantageous.

APPLICATION PROCEDURE:

Formal applications can be completed online: https://www.abdn.ac.uk/pgap/login.php

• Apply for the Degree of Doctor of Philosophy in Chemical Engineering
• State the name of the lead supervisor as the Name of Proposed Supervisor
• State ‘Leverhulme CDT in Sustainable Production of Chemicals and Materials’ as the Intended Source of Funding
• State the exact project title on the application form

Further information on the Leverhulme Centre for Doctoral Training (CDT) in Sustainable Production of Chemical and Material can be found at: https://www.abdn.ac.uk/engineering/research/leverhulme-centre-for-doctoral-training-in-sustainable-production-of-chemicals-and-materials-625.php