3rd PIN MEETING, UMIST, 27 APRIL 2000.MEETING MINUTES
The meeting, attended by 57 members and chaired by Colin Ramshaw, opened with a welcome by Robin Smith, Head of the Dept. of Process Integration at UMIST (www.cpi.umist.ac.uk) who recalled that he had been interviewed by Colin when applying for a post at ICI ‘some years ago’! A good proportion (30%) of the income for the Department comes from the 28 major companies in the research consortium, (something which we might see duplicated in a future Dept. of Process Intensification – DAR). Robin asked ‘What is process intensification?’ He said that everyone seemed to have their own idea, but a focussed one was needed and progress was perhaps being held back by the perception of lack of clarity. He saw parallels in process integration. But one is seeking in process intensification the radical step change to the process technology, and what needs addressing is how big should the step change be. Colin countered this by agreeing that one needed to rethink the process technologies, but said that the step was ‘pretty high’!
David Reay, PIN Co-ordinator, then updated members on PIN – the membership is now 230 – and recent/proposed activities, (see PIN web site for overheads). Future outputs will include the 3rd issue of PIN News, due in July (articles to David on DAReay@aol.com before the end of June, please), and the 4th PIN meeting at York University – see announcement at the end of these minutes. Of particular significance is the proposed PI Guide, with the sponsors likely to be the Health & Safety Executive (HSE), Department of Trade & Industry (DTI) and the Energy Technology Support Unit (ETSU), representing the energy efficiency aspects. It is planned that a draft will be put out to consultation in January 2001, and case studies provided by PIN members will feature strongly in the publication. Progress will be reported on the PIN web page.
Technical Session
Peter Redman of BP Amoco (Redmanpj@bp.com) gave a fascinating view of his Company’s attitude to ‘step-out’ technologies – it believes in them, and BP Amoco’s CO2 mitigation strategy – which it takes very seriously, in the context of his ‘What’s the Challenge?’ talk. The challenges are (a) the World is changing; (b) the industry is changing - - pressure is on to make cleaner products, and for oil companies this necessitates a move away from heavy crudes to H2 and gas, (or from oil refining to chemicals), and (c) the Company is changing – it is moving more into exploration and gas production. He then asked ‘Does the technology need to change?’ and the answer is yes.
In this context, market drivers have changed the old perception of production/processing of resources. Chernobyl, Brent Spa and the ozone hole are examples of these drivers. The price of resources has also reduced, but additional cost drivers such as the energy and landfill taxes have strong implications, which can be alleviated by sustainability – by not producing waste but by-products. These by-products are for heat generation and as feedstock for additional products, in the case of BP Amoco. In an ideal world we would all be moving in this direction.
The strategies an organisation can adopt may be reactive, responsive, proactive or competitive. BP Amoco has adopted the last of these, and is ‘setting the pace’. Particularly important is the commitment to reduce greenhouse gas emissions by 10% by 2010, compared to the baseline of 1990. From 1 Jan. 2000 a group-wide greenhouse gas trading system has been in operation. BP Amoco recognise that the reductions in greenhouse gases are difficult with existing technologies, and even with upstream, downstream and chemicals business energy saving opportunities, 50% of the required reduction will still be unaccounted for, about 18 million tonnes.
An approach outlined by Peter was to move from processing of crudes, which gives more C but less H, to gas, which can give more H and less C – build new products from gas rather than oil – and hopefully reduce energy intensity. (Refineries produce about 50% of the company’s emissions). This requires ‘technology’ from the likes of us, the developers!
The relevance to PI is:
Mike Brown of AMEC Process & Energy gave us an insight into the drivers and drawbacks of PI as seen by the largest UK-owned contractor, by covering topics such as PI off-shore, process flow scheme intensification and process equipment intensification, (Mike.Brown@amec.co.uk). With regard to off-shore equipment, Mike stressed the importance of weight – a saving of 1 tonne in process equipment weight saves 5 tonnes of structural weight, which has a value of about $25,000/tonne.
Examples of PI given included vapour/liquid separators, with vane/cyclone packs having a 2:1 reduction in volume, and for liquid-liquid hydrocyclones a 1:5 – 1:7 volume reduction was possible. Compact heat exchangers were also cited by Mike, the company obviously having extensive experience of their application off shore. The price of PI should not be neglected, Mike stating that sometimes one needs more equipment, valves etc. For example, with the PCHE compact heat exchanger, filters and filter cleaning equipment were needed, making the installation more complex (than larger volume alternatives). As well as ‘compacts’, tube inserts could be used on shell & tube units, as could high heat flux surfaces (UOP) or the ABB Lummus Helixchanger.
With regard to process flow scheme intensification, examples of PI such as divided wall columns for distillation and catalytic distillation – having the reactor in the column – were discussed. Specific data on hydrogen separation using methods such as cryogenic (normal) with a 20 unit plot area, 5 unit energy use and 1 day shut-down/start-up time was compared to membrane H2 separation, with, respectively, 1 unit, 1 unit and 20 minutes time. Pumps and separators were also used to illustrate how selection of appropriate types could reduce volume/plot area by over 60%
The challenge was to overcome the confidence difficulty. Three main points were stressed by Mike:
David Trent of the Dow Chemical Company in the USA (Davetrent@dow.com) reviewed the HiGee application in his company, and brought us up to date with the three units installed for stripping hypochlorous acid, used as the reactive chemical in a process (first discussed at the BHRG PI Conference in Antwerp in 1999). The rotating packed bed used for stripping was selected after other alternatives such as a spray distillation tower were rejected for capital cost reasons. The packing selected was a woven wire screen, with the gas flowing countercurrent to the liquid. Various packing surface areas were tested, with 200-3000 m2/m3 area densities, but these exhibited no performance differences so the lower value was used.
The pilot plant showed >90% yield, compared to 80% on a conventional spray distillation unit, with stripping gas use halved. The economics of scale-up looked favourable, but risk issues such as ‘will it work?’ and ‘is it reliable?’ needed addressing. The Chinese experiences of such plant provided some support for scale-up. The same packing was used as in the pilot plant, with a variable speed motor drive. With regard to reliability, speeds were <400 rpm, and the partner was a centrifuge manufacturer with a proven drive train.
The production machine yield was 93-96%, highly satisfactory, and after 6 months operation the unit has proved to be very reliable. It is easy to start up and shut down, and to operate. Pressure drop is <50% of that expected. Height of a transfer unit is 8 cm (4 cm was expected), but this is the same as the pilot plant. Three units were shown in a photo, two being adequate for production. The plant is operating at present at a planned 60% of capacity. There have been no control problems. It took 4 years from conception to having the process on line.
A further rotating machine, the Alfa Laval Centritherm compact evaporator, was described by Kjell Nessrup (Kjell.Nessrup@tetrapak.com). The intensification from rotation allowed one to reduce the surface to 20% of that of a falling film evaporator and a reduction in residence time to 12% of that needed in a falling film unit. The Centritherm can also deal with highly viscous fluids, to over 20,000 cP, and it has a small retained volume. In 40 years, 1000 units have been constructed, with new units having facilities for CIP (cleaning in place).
Kjell explained that the key to quality was a combination of low evaporation temperature and a short residence time. The rotation helped to ensure constant wetting rates and film thickness, avoiding burn-on. Low and well-defined vapour velocities were also important to avoid product loss. Concentration ratios of 25:1 can be achieved in a single pass, and there is a very low ‘thermal impact’ on the product, important in food and other sectors.
The ‘penalty’ is energy – because the unit is a single effect machine and thus needs a high temperature difference. Energy use can be reduced by using a conventional ‘pre-evaporator’ as an economiser – this reduces energy use by 66%.
Alfa Laval has now decided to collaborate with Newcastle University by sponsoring a project on spinning discs.
Colin Ramshaw, Newcastle University and Janet Etchells, HSE then discussed the topic of reaction kinetics, which was identified at the 2nd PIN meeting and during scoping of the PI Guide as a topic of importance. Colin (colin.ramshaw@ncl.ac.uk) started by comparing two types of reactions - those with either slow or fast mixing. In the former, diffusion of each component into the other was a recpe for disaster, as one is ‘deintensifying’ the operation and the stoichiometric ratio changes as one moves across the tube diameter. This also makes control difficult. The chemical kinetics are not matched by rapid diffusion.
With faster mixing, Colin stated that there was significant diffusion of each compoent into the other’s space. The stoichiometric ratio is nearly constant. Here there is a need to know the rapidity with which the kinetics operate so that one can understand intensified processes using rotation, micro-reactors, etc.
Colin gave a couple of examples of reactions which were not yet fully understood – p-xylene oxidation and the supersaturation zone in salt crystallisers.
Janet (Janet.etchells@hse.gsi.gov.uk) emphasised the need to operate intensified reactions safely, avoiding exothermic run-away, (where if temperature is not controlled and the heat production rises exponentially, doubling for every 100C rise. If one loses control, there is a rapid rise in pressure due to vapour and gas production, therefore in order to effect control, one needs to balance the heat output and the cooling capacity of the reaction vessel.
Other problems can arise with secondary unplanned reactions, and unstable substances, such as intermediates, can be present. There is a legal requirement to assess the risk and avoid it where possible, and to put in place measures to prevent or protect against eventualities. Janet outlined some of the measures which might be taken to help make PI experiments safer, which will be included in the PI Guide, and concluded by saying that the last thing we want is an explosion – as this could lead to a move away from the technology.
Colin then invited PIN members to help the Network identify research areas for support. Reaction kinetics is one area of interest. Contact Colin if you are interested in an academic/industrial collaboration in this area for submission to EPSRC for support, with information on the research area(s) of interest.
The discussion on the research agenda was kicked off by a revealing report by Jeff Howarth of NEL (Jhowarth@nel.uk) on the scoping study he is concluding for the DTI on the contents of a possible PI LINK programme. This is addressing the needs of the DTI/EPSRC, market barriers/failure to be overcome. PIN needs to identify ‘what stops PI happening’. Jeff said that a programme could be worked up in 2000/2001, a call issued in September 2001, with spending beginning in April 2002. It is likely that the programme would join the EPSRC IMI programme. Budget might be £5-6 million over 3 years.
Jeff gave preliminary conclusions as a result of his many visits to organisations active/interested in PI. He divided these into plus & minus points, market drivers, market barriers, and recurrent themes. Taking some of the important observations made by Jeff as a result of his study:
Comments from individuals visited included a reluctance to use rotating equipment, concern about blockage of narrow channels etc., design data may not be appropriate, and interfacing problems between conventional and PI kit. Market drivers included: ‘innovate or die’, distributed manufacturing opportunities, facilitates move from high volume to low volume/high value (chem. & process ind.), and Pi is relevant to many sectors.
Market barriers cited included: lack of awareness, conservatism, and the observed slow uptake of PI. The distance between engineers and chemists in the chemical ind. was a common thread with regard to ‘structural’ issues concerning PI.
Recurrent themes were: Demonstrations were the best place to spend money, as they give confidence in the technologies; methodologies were important, (how to include PI in your thinking from day 1); kinetics/design data; simulation software; chemistry/chemical engineering collaboration.
Impromptu Presentations
The 5 minute slots were opened by Jan Walpot of TNO, the Netherlands (j.i.walpot@mep.tno.nl ), who described new developments of the spiral tube heat exchanger first described at the last PIN meeting. The ‘Helix-Reactor’ is now used to exploit the mixing and intensified reactor properties possible with the design. Measurements of Nusselt numbers at low Re’s, showing much greater than in a straight tube, suggested that the helix form would make a good mini-reactor. CFD showed excellent radial mixing in the tube, and for axial mixing the helix was closer to plug flow than a straight tube. The relative residence time for 90% yield was 40% of the straight tube value. Jan concluded that the helix reactor could effectively intensify mixing, reaction and heat transfer. Further development includes experiment at Laporte Performance Chemicals.
Frigyes Lestak of M.W. Kellogg, (Frigyes.lestak@mwkl.co.uk) described the benefits brought by the use of a divided wall distillation column at BP Grangemouth. This resulted in a 25% capital cost saving, as well as using less energy. Further applications of this technology are being sought.
Terry Winnington of Process Kinetics (Terry.Winnington@processkinetics.com) is involved in, and interested in, setting up and running small scale scoping programmes related to PI. Under the Energy Efficiency Best Practice Programme he is demonstrating PI technology in chemicals/food/pharmaceuticals, and is looking for ‘softening’ of the costs of these activities with industrial support. Some of the results must go into the public domain from such work, however.
Henk van den Berg of Novem/WCE (h.vandenberg@ct.utwente.nl) updated us on the Dutch PI Task Force activity. Energy consumption reduction was an important reason for PI interest in Holland. Henk said that we needed to start development of technologies and management now. There had been two Task Force meetings to date. Publicity was planned, including in periodicals, and a national PI symposium is to be held in the Autumn. A start is being made on a PI manual/brochure. There are contract possibilities, including a theoretical study of the HEX-reactor and a study of transients & micro-systems.
Barry Johnson of BHRG (Bjohnson@bhrgroup.co.uk) reviewed current activities, including an EU-funded JOULE 3 project nearing conclusion. Work on characterising intensified lab. reactors to aid process development is progressing. Sponsors can influence design & construction, and the work allows BHR knowledge to be taken into partner companies in real processes.
Barry highlighted OSPRI, a project supported under the EEBPP, which is ‘on-site PI’. This is based on a mobile skid-mounted demonstration plant, with the EEO, BHRG and 4 companies. Different reactor types will be available. The first stage is a survey, followed by a 9 month design project, where suitable processes and their kinetics will be reviewed. The final stage will be the construction of the unit and site trials.
Workshops
Three parallel workshops were held.
Conclusion
Thanks went to all at UMIST, in particular Robin Smith, Frank Zhu and Lisa Ashcroft, for organising the event locally and helping to make the day a success.
Minutes prepared by David Reay, based on his notes, 18 May 2000. |