The Supaflo
High Rate Thickener

The Supaflo high rate thickener was invented in March 1983 by John Thixton. This website has been created to tell the true story about how the concept came into being. The first commercial unit was commissioned in August 1984 at Rum Jungle in the Northern Territory, Australia. The Supaflo is now marketed by Outokumpu OY of Finland. Over 1000 units have been installed in 50 countries world-wide. Total value of units sold may exceed $100 million.

To quote from the brochure "The revolutionary SUPAFLO high rate thickener has pioneered and redefined thickening and clarifyiing methods around the world". As with many inventions others have benefited from the SUPAFLO financially far more than its inventor.

---

Concept Development
as Related By John Thixton

In a conventional settling thickener pulp is introduced into a large tank. Solids settle to the bottom and clear liquid overflows from the top. The concept of introducing pre-flocculated pulp below the liquid surface into the settling pulp bed was probably first pioneered by the Australian Sugar Research Institute in the 1960's. It was demonstrated that significantly higher throughputs could be achieved using the principle. Enviro-Clear Inc. was the first company to market a commercial unit incorporating the principle. Between 1978 and 1983 I had been involved in marketing and commissioning Enviro-Clear thickeners. Whilst throughputs of up to 10 times that achieved in conventional settlers could be achieved, high flocculant consumption was a drawback. The units were also expensive, requiring a separate external deaerator tank and suffered from a lack of process control. Sudden increases in underflow density often resulted in the rake mechanism tripping out which usually meant the unit had to be emptied, hosed out and restarted from scratch.

Whilst on a flight from Tasmania to Sydney in March 1983 I did a sketch in my diary of an Enviro-Clear thickener then superimposed my high rate thickener concept on it with an inbuilt open deaerator/feedwell flared at the bottom and an inverted cone deflector fixed to the thickener rakes to deflect the pulp downwards at an angle of 30 to 45 degrees from the horizontal. The idea was to produce a larger "reaction zone". See reproduction of the diary page below.

The sketch that launched 1,000 Supaflos

 

The diagram below from the current Outokumpu brochure shows the open internal deaerator/feedwell and cone deflector as drawn in the diary sketch. It is these features that have enabled the Supaflo to outperform other high rate thickener designs.

 

In order to test the principle I borrowed a 3.5 inch Enviro-Clear laboratory test unit from the flocculant company, Catoleum and modified it by removing the horizontal deflector plate and replacing it with an inverted cone.

This test showed that the concept did work. I then had a 100mm unit fabricated from clear shinkolite tubing, purchased variable speed Masterflex pumps and did further testwork to establish parameters. This design has obviously stood the test of time because the laboratory test unit illustrated in Outokumpu's current brochure is identical to the one I built in 1983!
top

---

 

Sale of First Commercial Unit.

The Rum Jungle uranium mine was shut down in 1971 leaving behind a major environmental problem. It was decided that rehabilitation of the site was necessary to stop dumped tailings washing into the nearby river. The full story can be read at:
http://www.sea-us.org.au/oldmines/rumjungle.html

Samples of the tailings were laboratory tested in the 100mm unit and a quotation submitted for the supply of a 5.5 metre diameter Supaflo thickener. In September 1983 a firm order was obtained from the project engineers Mining & Process Engineering Services and a draughtsman was engaged to prepare detailed fabrication drawings of the unit. These were completed and checked in December 1983.

The unit was fabricated in Sydney and shipped to the Rum Jungle site, 65 km south of Darwin in early 1984 in a road/rail container. The unit was erected and ready for commissioning by July 1984.
top

---

 

Commissioning of the First Commercial Unit
at Rum Jungle

I flew to Darwin on Sunday 29th July 1984 to commission the unit. The following description is taken from a report I wrote subsequently: "It became apparent that no plant start up was likely before Tuesday or Wednesday so I decided to make a modification to the unit which I had considered as a result of experiments with the 100mm unit.

The deflection cone had been fabricated with a diameter of 700mm whereas the downpipe was 1000mm and the flared section 1400mm. I removed the two halves of the cone and took them to an engineering company in Darwin. I had intended to have them enlarged to 1400mm but the boot of my hire car would only accept them at 1200mm so I compromised on this.

In order to obtain an injection velocity of around 3m per minute the gap between the cone and the flared section was set at 180mm. Feed to the unit commenced on Thursday 2nd August 1984. When the unit filled it was apparent that the sealing between the adjustable weir plates and the shell was unsatisfactory. I drove into Darwin and bought 4 tubes of silicone sealant (the shops entire stock!) then climbed around the overflow launder filling the gaps. After further delays the plant was restarted at 5.00pm on 3rd and was then run continuously until 4am on Saturday 4th August during which time a bed was established in the unit and clear overflow obtained. Initially the feed to the unit contained 9% solids (design figure 3%) but with continuous operation it was down to 5 to 6% and at this level operation improved considerably. It could be seen that the there was a sharp interface between the bed and clear overflow and the bed was being subjected to a very gentle rolling-fluidised movement which is what is required to achieve good flocculation of the incoming feed.

It was also apparent that there was no air entrainment in the feed which is a very common fault in Enviro-Clear units. Thus the combined deaeration tank/feedwell worked very effectively.

Due to problems in other parts of the plant a shutdown was necessary at 4am. It would be hard to put into words the joy (and relief!) I felt as I drove back to Darwin in the early hours of Saturday morning. My concept worked!! I sang all the way. Since a lengthy shutdown seemed likely I flew back to Sydney. In a subsequent phone conversation with site personnel they advised that the unit was operating very well with very clear overflow. They commented "at least we seem to be on a winner there"

The plant operated until 1986 when the project to remove heavy metals from and neutralise the tailings was complete. The pictures below show the effect of the rehabilitation

top

---

 

My thoughts at that stage

At the end of my report on the successful commissioning of the first commercial Supaflo unit I made the following comments: "The thought occurs that we might possibly get a patent for a design whereby the pulp is injected downwards at an angle of 30-45 degrees into the pulp bed. The argument would be that in a pulp bed a gradual increase in pulp density occurs from top to bottom which causes an upflow of liquid. When incoming pulp is injected horizontally into this pulp bed the rising liquid stream tends to force very fine particles straight out of the surface of the bed. They then rise and pass out of the unit causing dirty overflows. However when the pulp stream is injected downwards at an angle, fine particles get pushed deeper into the bed and have a better chance of flocculating and not escaping from the bed."

I never did apply for that patent. What a pity in the light of subsequent events!

I must confess the Rum Jungle unit was a huge gamble and the relief felt when it was successfully commissioned was enormous. Little did I imagine back then that 23 years later over 1000 Supaflo units would be in operation world wide.

It makes me very proud that I pioneered the concept.
top

---

 

A Setback - Sunila, Finland.

At that time we were associated in business with Larox OY of Finland and they were given a licence to sell the Supaflo in areas where they had representation. They chose to market it as the FB (for filter bed) thickener. In late 1984 they sold a unit to Sunila in Finland. In April 1985 they attempted to commission it without success. When the SOS came for help I was away from the office so Neil Jagger got on the first available flight to Finland. After spending 2 weeks at the site he failed to get it working. The unit was shut down pending further on site inspections and tests.

In September 1985, I visited the site and it was immediately obvious to me why the unit had failed to operate. I wrote a lengthy report at the time the salient points of which were:
1. Larox had attempted to convert a conventional thickener to a high rate unit. The thickener had only radial launders in the form of a central square. This area inside this square represented only 16% of the total surface area of the tank. Thus the liquid rise rate inside this square was much too high. The effect was to drastically reduce the effective diameter of the unit. They were advised to remove the radial launders and fit a peripheral one.

2. No pulp bed level detector had been fitted making pulp bed level control impossible.

3. They were also advised to lengthen the downpipe.

I do not know if these modifications were ever carried out.
top

---

 

The Lessons of New Zealand Steel
Correct Feedwell Design & Flocculation

I first tested samples of ironsands from New Zealand Steel in November 1984. On the basis of the tests I tendered for the supply of a 9.5m dia. Supaflo and after flying to Auckland in March 1985 returned with the order.

Commissioning was delayed due to problems in other parts of the plant but eventually start up began on 11/2/86. My 2 weeks at the site proved a nightmare. This was, without doubt, the most difficult commissioning job I have ever done. I probably averaged 16 hours a day at the site, only driving back to my hotel in Auckland for a sleep when my body just couldn't keep going.

Problem were numerous but probably the biggest stemmed from the fact that the original sample as tested was not truly representative of the actual feed, it had been made up synthetically. Also our new engineer had the not so clever idea of introducing feed tangentially into the feedwell which proved disastrous - the entire thickener contents swirled! Various sizes of temporary wooden baffles were tried before a suitable steel one was welded into place to stop the swirling. A further problem was the presence of coarse heavy material which accumulated on the deflector cone closing off the plate gap. These could only be removed by emptying the unit and hosing them out of the feedwell. Plant modifications were necessary to remove the coarse material from the feed pulp.

The 2 weeks proved invaluable for subsequent Supaflo design. The need for multiple flocculant injection points and the use of adjustable length sparge pipes helped solve flocculant dosing problems. The problem was finally diagnosed by cylinder flocculation tests which demonstrated the fragility of the flocs. Hence flocculant needed to be added as late as possible before the feed entered the pulp bed.

It was at NZ Steel that one of the major advantages of the open, internal de-aerator/feedwell design was first noted. Due to their different S.G.'s the level of clear overflow outside the feedwell was always higher than inside it. This facilitated gravity dilution of the incoming pulp using adjustable weirs for flocculation purposes. I note that Outokumpu claim "the world's first systems to auto dilute feed". This was done at NZ Steel 20 years ago!

I have copious notes on the commissioning but sufficient to say when I left the site on Saturday 21/2/86 the thickener was working satisfactorily. The present 'floc-miser' feedwell owes its origins to the New Zealand Steel experience.
top

---

 

Counter Current Decantation

1. Lebong Tandai - Indonesia

My greatest wish in the early years was to secure an order for a CCD circuit. Successful pilot testwork was done in December 1984 at Roxby Downs (see below) where the 1 metre unit was incorporated into a CCD circuit so I was confident it could be done. In May 1986 I attended the Institute of Mining & Metallurgy Conference in Singapore. There I made contact with metallurgists from the Indonesian company PT Lusang who were re-developing a gold mine at Lebong Tandai in Sumatra. It had been worked by the Dutch years before but they had left behind gold bearing tailings which presented an ideal CCD leaching situation. However, as I was to find out on my site visits, the mine location was unique being in a river gorge with steeply sloping sides. There was insufficient level ground to accommodate large diameter conventional thickeners. Their preferred treatment method when I made contact was a horizontal belt filter with counter current washing. I managed to convince them Supaflo thickeners could do the job and would require much less level ground than conventionals.

I returned to Sydney on 17/5/86 and took the first available flight to Jakarta on 25/5/86 taking with me the 100mm test unit. The journey to Lebong Tandai is an all day adventure. First a flight, then a drive over very rough road followed by a 2 hour ride up river in a canoe with an outboard motor before a final hour on a narrow gauge railway. The tests were successful and I returned via the same lengthy route and back home on 31/5/86.

100mm test unit being loaded aboard river canoe

After a lengthy meeting with PT Lusang personnel I finally convinced them and got an order for 4 x 5.5m Supaflos. However supply had to be on the basis of local tank fabrication to our drawings with rakes, feedwells and drives supplied from Australia. Whilst I didn't like this scenario it was necessary to get around Indonesian local content rules for steel imports.

They were in a big hurry to get the plant operating and supply had to be quick. The units were erected and ready to go by November 1986. I spent 3 weeks at Lebong Tandai from 18/11/86 to 6/12/86 supervising final erection details and commissioning the units. We had also supplied, for the first time, closed loop control systems whereby underflow withdrawal rates were controlled by the rake torque and floc dosing rates by the bed level detector.

An interesting sideline occurred prior to the commencement of commissioning. The local people insisted that the plant would not work unless the Gods were placated. To do this they slaughtered a steer and buried its head in the middle of the site. It must have worked because the commissioning went very well thereafter.

I should also mention they roasted its body on a spit and had a grand barbecue. During the following months the operators were able to considerably increase throughput. Mine personnel were delighted with the success of the installation.

Supaflo CCD Circuit at Lebong Tandai
top

---

 

2. Olympic Dam - Australia

When Rio and Fluor were building the first pilot plant at Olympic Dam in South Australia I got permission in June 1984 to take the 100mm test unit to the Olympic Dam site which was pretty rough at that stage. Accommodation was in pre-fabricated "Dongas".

Rio personnel were able to witness the successful operation of the test unit in their site laboratory. At that stage a 1 meter diameter pilot unit was under construction and the Rio people said they would like it at Olympic Dam as soon as it was available.

In December 1984 I returned to site and commissioned the 1m unit. It was then operated by Rio personnel so successfully that they phoned me on 13/12/84 to say that after I left they had achieved up to 10 times the throughput of their conventional thickeners.

The 1m unit was returned to site again in January 1985 and again for a 4 month period commencing in July 1985. During this period they were able to put the unit in series with 3m conventional thickeners in a CCD circuit, taking the full flow from these units - great news.

In June 1986 a tender was submitted for the supply of 5 x 14.5 metre Supaflos for Olympic Dam and in August 1986 the order for these units was obtained. A 6th unit was ordered a couple of months later.

It would seem from the Google Earth picture below that when the plant capacity was increased conventional thickeners were selected rather than Supaflos. I find this surprising and can only assume this was a result of poor customer liaison.

Olympic Dam - Google Earth
top

---

 

Athens Mine - Zimbabwe

I made 2 visits to Zimbabwe in connection with a Larox OY bid to supply 3 units to the mine. On the second visit in August 1986 the units were successfully commissioned.
top

---

 

The Choice of the Name 'Supaflo'

When the concept was licensed to Larox Oy they called it the FB (for Filter Bed) thickener. I didn't like the name but unfortunately they went ahead and printed brochures using it. In October 1987 I decided it was time for a change. Several options were considered including Maxout, Ultraflo, Maxithick, KrisKlear and Supaflo. I conducted a ballot amongst all the staff and they agreed Supaflo was the best. Unfortunately a man in Perth held the rights to it but I managed to locate him and he agreed to release it. By mid 1988 over 50 Supaflo thickeners had been sold world-wide.
top

---

 

The Worst Day of My Life.
The South African Conspiracy

Monday 29th August 1988 was, by far, the worst day of my life.

On that day fellow director Neil Jagger, supported by 3 employees, David Taylor, Ian Arbuthnot and Jonathon Trope confronted me with an ultimatum. Either I sold my half share of Supaflo Pty Ltd to him or all senior staff would resign and take most of the junior staff with them to form a new company making high rate thickeners. I was shocked and disbelieving that these 4 young men who had every reason to be extremely grateful to me for the friendship and career opportunities I had given them should turn on me in this fashion.

Briefly: Jagger - see separate box.
Taylor I had known for over 10 years, both workwise and socially. He was out of work when I offered him a job in about 1981. It is interesting that a few weeks earlier Jagger had wanted to sack Taylor for incompetence! Arbuthnot and Trope, I interviewed in South Africa in September 1985 and subsequently offered them jobs in Australia, going to great trouble with the Department of Immigration to expedite their applications for residence permits.

I was given no time to consider my options but rushed off to the office of the company's accountant and plied with alcohol. Unfortunately in my confused state I drank too much. In an inebriated state and without the benefit of legal advice I was pressed into signing a document which gave away everything I had worked for including all my rights to royalties from future Supaflo sales. I was paid only for my shares in Supaflo P/L but received nothing for the ongoing rights to manufacture Supaflo thickeners.

It was a foolish mistake but I was confused and deeply hurt. In the months and years that followed I came to bitterly regret signing. I did learn that Jagger got the support of the others by promising them shares in the 'new' Supaflo P/L. I also learned that the threat to take all of the junior staff was a bluff - they were never consulted.

In all my working years I still consider the action by Jagger as the worst act of treachery I have ever encountered.

The real tragedy is that these men allowed the manufacturing rights of this Australian invention to fall into the hands of a foreign company. I would never have let that happen.

Jagger is now a President of Outokumpu Technologies and is presumably a very wealthy man.
top

---

 

The Ensuing Years

After the unfolding of these events I went through a few very bad years. Initially I found myself walking around in a daze wondering how this could have happened to me after all the personal sacrifice I had made particularly at Rum Jungle and New Zealand Steel. I had spent many weeks away from home getting orders and commissioning units. It all seemed like a bad dream from which I would eventually wake up. I hated and despised Jagger for what he had done and thought of ways to get back at him. Such ways existed but I couldn't bring myself to use them.

I suffered a chronic depression, my marriage broke up and I was really in the pits.

Fortunately I met my present wife who is a Psychotherapist. She got me over my anger and into a new life.

I discovered I had other talents besides inventing thickeners. We now live in a beautiful house overlooking Balmoral Beach and spend 3 months every summer travelling or at our house in the South of France.

I suppose I could dwell on all the lost royalties I should have got from the 1000 Supaflos Outokumpu have sold but at least I have a clear conscience about the way I have dealt with my fellow men throughout my entire life. Others may have trouble with their consciences and problems sleeping at night! I hope so.

Now in my 75th year I am a keen cyclist, doing about 100km each week, work out in our gym, play tennis and kayak. I have 8 beautiful grandchildren who are a delight to be with.

Life is good!

If anyone would like to join John & friends on safe organised bike rides either during the week or at week-ends visit
http://groups.google.com.au/group/manmosbug
To see John's online photo albums click on:
http://www.flickr.com/photos/jthixton/

The reader might ask why I have chosen to do this website after all these years. It came to my notice recently that Jagger got an award in 2002 from the Australian Institute of Mining & Metallurgy for "revolutionising of the development and implementation of new thickener technology". I haven't seen the citation but if it was for inventing the Supaflo he should give the award back. His contribution to its development was minimal!

All of the events described on this web site are documented in my diaries from the 80's.
top