ChemE.info – Chemical Engineering Consulting

Australia is a large country (with a small population) which has lots of coal reserves, quite a lot of natural gas, and virtually no oil.

Back in the 1980′s after the first Middle East oil embargo and against the continuing backdrop of Middle East political unrest, the Australian Department of Primary Industries decided to study whether and how Australia’s abundant coal reserves might be used to produce synthetic liquid fuels (e.g. diesel, jet fuel, gasoline, etc.) in case imported oil became scarce or unavailable.

DPIE (never, we were told, to be pronounced “dopie” ;) ) commissioned Broken Hill Proprietary’s R&D arm to develop a pilot-scale coal liquefaction process and run experiments on the various coals available in Australia. My recollection is that they looked at coals from the Victoria, New South Wales, and Queensland.

For those unfamiliar with Australia, Broken Hill Proprietary (or BHP) is the 800 lb gorilla of the Australian economy. Not only is it a huge company but is also the primary player in terms of industrial R & D. In a US context, it is as if you combined IBM, GM, GE, and Microsoft into a single entity.

So BHP set up pilot plant facilities at their R&D campus in a suburb of Melbourne and began running tests on the various domestic coals. The actual liquefaction process was largely based on what had already been shown to work in the US and Europe.

I don’t remember the BHP process in any detail but, like all coal liquefaction processes, it involved processing pulverized coal with coal-derived liquids and hydrogen under high pressure and high temperature. This then produced two streams, an ash residue stream and a liquid roughly comparable to crude oil. It was this synthetic crude oil that was intended for additional processing to produce synthetic diesel, kerosene, and gasoline. A fraction would also be recycled back to liquefy additional coal.

Of course, the pilot plant process was intended to collect data on the process and the immediate synthetic crude product. It did not provide any directly useful information on the overall process economics.

So DPIE commissioned us (AspenTech) to develop a simulation of the complete process including coal pre-processing, coal hydroliquefaction (based on the BHP pilot-plant data), the synfuel refining section, and all the other support sections (e.g. hydrogen production).

The simulation was intended to represent an actual commercial-scale plant, its operating costs, and capital costs with a view to determining what the net cost of the final transport fuels would be in equivalent dollars per barrel. This would then give one idea of how high world oil prices would have to be for a coal-based synfuel plant to be competitive.

The other purpose of the modeling effort was to ensure that BHP was collecting enough consistent data to support such a study.

The process side simulation was challenging (this was a large model with a lot of distillation columns, reactors, and recycle streams) and the economic side required a lot of assumptions. For example, databases used to estimate capital equipment costs were US-based, no Australian capital equipment cost data was available.

It was a very interesting, challenging project and I enjoyed my stay in Australia (I was out there for a total of 6 months) and it was fun working with my colleagues at BHP.

The conclusion of the project was rather bemusing and, I suppose, shows how naive engineers are. One of the things we’d been asked for in the RFP was a comparison of the process economics for the different Aussie coals (Victoria, New South Wales, and Queensland). So our final report had a table comparing the results and we had text discussing this… Basically, the model showed that Queensland coal had the best economics and our conclusions said as much. But DPIE kept delaying approval of the report and, since our final payment was dependent on the report being accepted, we were getting a bit anxious. But no one was giving us any specifics on why the report was not being accepted.

Eventually, one of the BHP managers had to give us a little explanation of Australian politics… That Victoria was a much more populous state than Queensland and therefore had more MPs and more clout in the Federal bureaucracy than Queensland did… And that DPIE did not want to approve our report while it explicitly stated that the Queensland coal was a better choice than the Victoria coal. (Neither were they willing to tell us that directly.. ;) )

So we changed the text of the conclusions… The comparison tables still showed that the Queensland coal produced less expensive synthetic fuels but we didn’t explicitly mention that in the final conclusion. And… The revised report was accepted.

Now that world oil prices are up around $60 a barrel, I wonder if anyone in Australia is revisiting this area to see what the current synfuel economics look like.

I spent about a year at Kennecott Development working on a project for Kennecott’s Carborundum subsidiary (I think Carborundum is now owned by Saint Gobain). We were developing two processes for making boron nitride ceramic fibers. One process was intended to make tensile BN fibers for use in woven composite materials. The second process made a loose BN fiber mat that looked very much like the pink fiberglass mat used in home construction (the BN wasn’t pink of course ;).

What I want to focus on here is the second fiber mat process. One cannot spin Boron Nitride fibers directly so the process involved spinning boron oxide glass fibers first and then nitriding the BO with ammonia to convert it to BN.

As I mentioned, the fiber mat we wanted to end up with looked a lot like fiberglass wall insulation so the BO glass spinning apparatus was modeled on a commercial fiberglass spinning system. This was comprised of an electrically heated metal tank that stored the molten boron oxide glass, a metering valve, a perforated spinning cup, and a torch system.

The molten boron oxide glass was metered into the spinning cup where it was thrown against the side by the centripetal force. It then extruded through the holes in the cup a formed a cloud of glass fibers surrounding the cup. The torch was positioned so that it melted through the fibers once they reached a certain radius from the center of the cup so that one would get a consistent fiber length in the mat.

In the commercial fiberglass system, the torch would have been supplied with either natural gas or propane. But boron oxide glass is very hygroscopic; in other words it soaks up moisture from the air. When exposed to humidity it ends up looking like sticky cotton candy. And, of course, a major combustion product of both natural gas and propane is H2O.

So what to do? We needed a torch fuel that didn’t produce water vapor as a product of combustion. I don’t think it was me that thought of it but somebody on the team came up with a very elegant solution. We used carbon monoxide as the fuel and that worked quite well. It burned hot enough to cut the fibers as needed and the only combustion product was CO2 so we didn’t end up with cotton candy. Neat, eh?