Destruction of the 'Black Lagoon'

Article by Jimmy Hunter BSc CEng CSci

1982, Secunda, Transvaal, South Africa

READING a technical article, we don’t think (or know) about the writer’s family life. The journeyman chemical engineer has to deal with the often unseen dramas, including uprooting of family, racist attacks, and so on associated with moving hundreds (even thousands) of miles from home. To give readers some idea of what problems can arise in the lives of a chemical engineer’s family, I have included some family background on the events surrounding this article.

I left the role of Works Manager of Chrome Chemicals in Durban, South Africa, after five years because I had run out of technical challenges and was tired of trying to solve the personal problems of some of the workers. I foolishly tried starting a consulting business, but I didn’t have enough grey hairs, and there was insufficient chemical industry in the Durban area. Starvation was staring us in the face (there were no state benefits to speak of in South Africa).

I took a job as Senior Process Engineer with SASOL 2 in Secunda, some 530 km away in the Eastern Transvaal. It offered a good salary, company car, cheap rented houses and plenty of technical challenges.

SASOL 2 was a massive petrochemical project, based on the Fischer-Tropsch conversion of coal (via gasification) to petrol. The capital cost was more than US$1bn, and a second plant, SASOL 3, was being built next to it. To give an idea of the size of these plants, the cooling water make-up line was big enough to drive a van through! The South African Government was encouraging this venture because it was afraid of sanctions, which could cause oil supplies to be cut off.

Uprooting the family

Our sons had to leave their friendly little school in Westville and go to a big school in Secunda, run by very conservative people. The teachers were well-meaning, but liberalism was not part of their make-up. Most of the pupils were children of contractors from all over the world. Some of them were very wild, and one stabbed a teacher to death the year after we left.

My wife, "M", heavily pregnant at the time, was reasonably happy with the house we rented. It had an established garden, and was in a part of Secunda, the company town, with some friendly people who made us feel welcome.

Only a few weeks after we moved in, the excellent HR department informed us that the owner was no longer renting out our house as he wanted to sell it. The only available house was a brand-new one on a ploughed field, with no trees or garden. M was very unhappy at the prospect of a second move in three months, and she was in no state for gardening. I started contacting employment consultants back in Durban with a view to moving back.

New houses were being built at a rate of a few weeks per house. A team of Sotho workers was digging the foundations of another house on the other side of our fence, supervised by an Induna (chargehand). A white foreman arrived in his van and decided that the foundations were not correct. He grabbed a heavy spirit level and began to beat the defenceless Induna, with much loud racist swearing. My brave wife, eight months pregnant, rushed out of the kitchen and confronted the attacker. He was amazed at her intervention. She made him stop, and told the Induna that if he wanted to lay a charge against the foreman, she would be his witness. The foreman began screaming obscenities and called her all sorts of racist names. He finally left when she mentioned the police. I reported the incident to the HR department, and the foreman did not return.

These events formed the backdrop to our stay at SASOL 2. We were a very unhappy family, and focussing on solving the technical problems of SASOL2 was very difficult. I knew that I had to think clearly and not allow the events to affect my work.

Problems at work

SASOL had set up its Process Department and Projects Department as two separate companies. I worked in the Special Assignments Department for Sasol 2. Our department’s task was to oversee the activities of these two companies, to ensure that they were doing the right projects at the right time and place.

The Fischer-Tropsch process reacts carbon monoxide with hydrogen over a metal oxide catalyst to form hydrocarbons and water:

nCO   +   (2n+1)H2     -->    CnH2n+2  +    nH2O

N can vary from 1 upwards. Iron catalysts produce hydrocarbon mixtures which can produce “heavy” molecules like waxes, etc. More modern catalysts, such as cobalt-based catalysts, produce mainly lighter hydrocarbons.

At Sasol2, the mixture of hydrogen and carbon monoxide was produced by gasification of coal with oxygen, and reacted over a solid catalyst. The mixture of hydrocarbons from the reactor then flowed into a large distillation column, heated by steam. Methane and other “light” hydrocarbons were the overhead products, while a “heavy” fraction, consisting mainly of heptanes, octanes, nonanes, was discharged at the base. This fraction was then further treated to produce petrol and recover “heavier” components for other purposes such as diesel, etc.

 Unfortunately, the column’s performance was erratic. It would work steadily for a few weeks, then suddenly go out of control and the plant had to be shut down and the column drained. The black liquid drained out into a large “pond” which I called the “Black Lagoon”.

One of the projects on our books was to replace this column. Sasol Process had decided that the column was too small, so had designed one with twice as much capacity. Sasol Projects was planning to spend millions on building the column. Our task was to facilitate this.

I was horrified at the thought of the cost of this project. My reasoning was that the existing column had enough capacity initially, but something was building up in the column until it no longer had enough capacity. The task was to find the material building up and to deal with it.

Clearing the black lagoon

My boss did not see things in the same way. His attitude was that the “experts” had decided on this course and it was not in our remit to argue. Our task was to ensure that the new column was correctly installed. I pointed out that the plant would work the same with the new column, except that it would take twice as long to fail, but the volume of liquid into the “Black Lagoon” would be twice as much. This would thus not solve the problem. I decided that I would try to solve it before any more money was wasted.

There was very little information available, but I set up differential equations for the kinetics of the process. We did not have computers available, but I had my personal HP65 Hewlett-Packard desktop computer, with 36k memory. I used the methods described in Reference 1 to estimate the values of the rate constants and hence model the behaviour of the column. What made the calculation difficult is that the article in reference 1 gave a computer program written in FORTRAN for integrating the equations, but the HP65 only had BASIC, so I had to translate the program into BASIC.

The model suggested that, in addition to the “heavy” components like heptane and octane, butane would also be formed. Butane would be too “heavy” to be removed overhead, but too “light” to be discharged with the product at the base. Butane fitted perfectly as the mystery material which was building up in the column, until it flooded.

I then had the problem of convincing my boss, who finally agreed to publish this information for the Sasol Process team. Their response was that the research people had made some measurements on the pilot plant in the past, and found no butane. Luckily someone finally took me seriously, and they changed the design of the column to remove butane continuously with a separate offtake line. However, even if no more liquid was discharged to waste, the “lagoon” still needed to be removed. Luckily, there was a contractor from Durban who had developed a centrifuge which recovered the oil from the solid catalyst. The “Black Lagoon” was on it’s way out! Unfortunately, I did not stay with SASOL2 long enough to see the modification implemented, since by then we had definitely decided to move back to Durban. I had to rely on feedback from friends on the outcome, which was a delightful vindication.

Back to the family

In the meantime, M had produced another bonny son. This involved a 200-mile round trip for me with a blood plasma sample because she is Rhesus negative and our baby was yellow. When they were out of hospital, the Durban contractor offered to fly her and the baby to Durban in his 2-seater plane to show the new arrival off to M's mother and sister. It was with very mixed feelings that I waved them goodbye, but they made it back.

The Sasol management offered me a promotion to Principal Process Engineer (nicer car!) and a move to the R&D team at Sasolburg in the Orange Free State. This would have been like going from the frying pan into the fire, since Sasolburg was also a very conservative town. However, by that time the employment consultants had found me a job back in Durban and my sons got back to their school and we settled back in Durban. Apart from the enormous stress involved in the move, we had lost a great deal of money because we lost on the sale of our house as well as all the costs of the move itself.

However, I learned a great deal about the petrochemical industry and met some very good people in the process. I also learned that I had married a gem!

Reference

 1. King, RP, "Estimation of parameters in systems defined by differential equations", South African Journal of Science ,63, 1967

Article by Jimmy Hunter BSc CEng CSci

Process engineering consultant, JHunter Process

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