Getting the job done: increasing the capacity of a methanol plant in Trinidad

Simon Early, senior principal process engineer, Davy Process Technology, BSc (Eng) chemical engineering, Imperial, College London (1981)

The project in brief

• PROJECT A 5,000 metric tonnes per day (MTPD) methanol plant based on conventional steam-methane reforming with a second 400 MTPD synthesis section taking additional feed from the purge gases of the adjacent Davy-designed plants in Trinidad.
• CLIENT Methanol Holdings Trinidad (Limited) (MHTL) – the second largest methanol company in the world.
• REASON FOR PROJECT MHTL wanted to increase its capacity while methanol prices were expected to remain high. The client wanted the biggest single-stream plant possible.
• SCHEDULE Initial discussions, Dec 1998; technical kick-off meeting, Feb 2001; construction completed, Jul 2005; first feed to plant, Sept 2005; guarantee test run, Nov 2005.
• COST Many hundreds of millions of US dollars.

In 1998 the focus was on reducing the cost of methanol so that it could enter the fuel market and compete directly with gasoline. The lowest production cost comes from low capital cost (per annual tonne of production), low feedstock cost (natural gas for most methanol plants) and high on-stream time. M5000 was aimed at this target.

The design work for the plant took place in London and Mumbai, India, with 100 engineers working on the project at peak load. I was involved as the technology expert at the research and development (R&D) stage and worked through to the development of a full-scale design for the world’s biggest methanol plant. I then took over as lead process engineer for commissioning in Trinidad.

Beating the limits of what was thought possible

The biggest challenge was designing 5,000 MTPD in a single stream. Not long ago papers at the World Methanol Conference said that 2,500, perhaps 3,000 MTPD, was the limit of conventional technology. To add to this challenge M5000 is also in the middle of an existing complex, which limited plot space.

I worked closely with the reformer designers to keep the reformer as small as possible. We used the newest pilot plant at Davy’s technology centre to run tests and simulate the proposed reformer inlet conditions. Vessel designers gave advice on what was practical to build – at one point some internal parts of the main converters were so thick they could only be made from the steel used in the hulls of nuclear submarines.

We used a lower synthesis pressure to reduce the main compressor power and a radial-flow steam raising converter gave good catalyst performance at the lower loop pressure. This was the biggest technology challenge, but it had been done before at a smaller scale so we knew that it would work. State-of-the-art software was used for computational fluid dynamic (CFD) modelling of several parts of the design.

Taking the project from concept to commissioning

Taking the design from a concept sketch through all the stages to commissioning the world’s largest methanol plant was terrific. I’d wanted to do something like this since my second-year design project at university. Some features went straight from the drawing board to world-scale in one step. The power and accuracy of modern computers was a significant factor in this and access to Davy’s R&D facilities gave us the confidence that the plant would work.

Everything I learned at university and in the 20 years since was put to use in this project. I employed all my skills from basic thermodynamics to compiling enormous Excel spreadsheets and designing test rigs. I also gave presentation after presentation to showcase new features and explain how we had tackled design issues. Persuasion and clear communication were essential skills for putting forward the new approach to plant design that was required.

Now M5000 is fully contributing to Trinidad’s position as the world’s largest producer of methanol, and given current methanol prices, it’s making our client lots of money.