Surface Modification of Metallic Reaction Vessels to Resist Scaling by Calcium Salts

Lead Research Organisation: University of Manchester
Department Name: Materials


Sugar cane ethanol plants use the addition of lime to the raw extracted juice in order to neutralise and clarify the juice. This leads to the juice becoming saturated with a range of calcium salts, notably sulphate, phosphate, silicate, and oxalate. This leads to the deposition of these salts as a hard scale on the insides of the tubes in the evaporators, where the sugar juice is concentrated by boiling off the water. The hard scale reduces the heat transfer rate in the evaporators, and would eventually lead to blockage of the tubes.

Normal practice in Brazil is for the evaporators to be cleaned manually, as often as weekly. This involves personnel being lowered into the upper chamber of the evaporators and removing the scaling by "rodding", i.e. physical abrasion of the inner tube surfaces. Not only does this involve undesirable working in confined space, but it inevitably also leads to significant wear on the tubes leading to their frequent replacement. In countries where labour is most expensive, chemical cleaning has been attempted with rather mixed results. One difficulty is that such a diverse range of calcium salts is involved, a range of different (and mutually incompatible) chemical cleaners, including strong alkali, are needed to remove the deposits, so several cycles of cleaning are required each time, and some of the chemical cleaning agents also introduce additional hazards. Furthermore, each of the evaporator stages has a different combination of scalants, and requires different treatment.

This project forms part of BP Group Research's response to this issue, and seeks to find means of treating the insides of evaporator tubes (and potentially other vulnerable surfaces) such that the calcium salts do not nucleate on those surfaces. It is understood that the evaporation of water must inevitably take the juice beyond the solubility limit of the salts concerned, so the aim must be to ensure that the salts either crystallise in the bulk rather than on the surface, or form solids which readily detach from the surface rather than form hard scales. In a practical implementation, this would require installation of filtration or settling equipment downstream of the evaporators to collect these calcareous precipitates.

Planned Impact

The EPSRC Centre for Doctoral Training in Advanced Metallic Systems was established to address the metallurgical skills
gap, highlighted in several reports [1-3] as a threat to the competitiveness of UK industry, by training non-materials
graduates from chemistry, physics and engineering in a multidisciplinary environment. Although we will have supplied ~140
highly capable metallurgical scientists and engineers into industry and academia by the end of our existing programme,
there remains a demonstrable need for doctoral-level training to continue and evolve to meet future industry needs. We
therefore propose to train a further 14 UK based PhD and EngD students per cohort as well as 5 Irish students per
cohort through I-Form.

Manufacturing contributes over 10% of UK GVA with the metals sector contributing 12% of this (£10.7BN [4,5]) and
employing ~230,000 people directly and 750,000 indirectly. It is estimated that ~2300 graduates are required annually to
meet present and future growth [5]. A sizeable portion of these graduates will require metallurgical expertise and current
numbers fall far short. From UK-wide HESA data, we estimate there are ~330 home UG/PGT qualifiers in materials and
~35 home doctoral graduates in metallurgy annually, including existing AMSCDT graduates, so it is unsurprising that
industry continues to report difficulties in recruiting staff with the required specialist metallurgical knowledge and
professional competencies.

As well as addressing this shortfall, the CDT will also impact directly on the companies with which it collaborates, on the
wider high value manufacturing sector and on the UK economy as a whole, as follows:

1. Collaborating companies, across a wide range of businesses in the supply chain including SMEs and research
organisations will benefit directly from the CDT through:

- Targeted projects in direct support of their business and its future development and competitiveness.
- Access to the expertise and facilities of the host institutions.
- Involvement in the training of the next generation of potential employees with advanced technical and leadership skills
who can add value to their organisations.

2. The UK High-Value Manufacturing Community will benefit as the CDT will:

- Develop the underpinning science and advanced-level knowledge base required by future high technology areas, where
there is high expectation of gross added value.
- Provide an enhanced route to exploitation, by covering the full spectrum of technology readiness levels.
- Ensure dissemination of knowledge to the sector, through student-led SME consultancy projects, the National Student
Conference in Metallic Materials and industry events.

3. The wider UK economy will benefit as the CDT will:

- Promote materials science and engineering and encourage future generations to enter the field, through outreach
activities developed by the students that will increase public awareness of the discipline and its contribution to modern
life, and highlight its importance to future innovation and technologies.
- Develop and exploit new technologies and products which will help to maintain a competitive UK advanced
manufacturing sector, ensure an internationally competitive and balanced UK economy for future generations and
contribute to technical challenges in key societal issues such as energy and sustainability.

1. Materials UK Structural Materials Report 2009
2. EPSRC Materials International Review 2008
3. EPSRC Materially Better Call 2013
4. The state of engineering, Engineering UK 2017
5. Vision 2030: The UK Metals Industry's New Strategic Approach, Metals Forum


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S022635/1 01/10/2019 31/03/2028
2386022 Studentship EP/S022635/1 01/10/2019 31/03/2024 Huda Al-Jurani