Biofuel Tests at Zoo - Round Two

Test locomotive No. 1924 blasts up the 3% grade hauling a heavy train. The locomotive is being fired with 100% torrefied biomass fuel and is instrumented with test equipment to gauge firebed and smokebox temperatures.

CSR and NRRI again collaborated with the Milwaukee County Zoo to undertake a comparative test of torrefied biomass fuel and coal this past October. The previous round of tests CSR undertook in June employed very small (3/8 inch diameter) cylindrical fuel pellets. While the finding of those tests were promising, CSR sought to undertake tests with fuel analogous in size to that employed on preserved steam locomotives.

The researchers at the Natural Resources Research Institute (NRRI) produced 500 lbs of torrefied biomass with its recently-commissioned torrefaction reactor and densified it using a B-100 cylindrical densifier to an approximate size of 1-1/4 x 2 inches [shown below, second from left]. These larger pieces of fuel were more analogous to the coal typically used by the Milwaukee County Zoo. As expected, the larger torrefied biomass pieces burned more cleanly in the firebox than the smaller pieces used in the previous round of testing.

As with the previous tests, CSR instrumented the locomotive with four thermocouples [shown at right], three in the firebox and one in the smokebox, to document temperatures on comparative tests between torrefied biomass combustion and coal combustion. To minimize the risk of sparks from coal/torrefied biomass fines, CSR also fabricated and installed a custom spark arrestor for use on the stack of the engine.

Tests revealed that the torrefied biomass burned with similar temperatures as the coal and with little smoke [see images at bottom]. It also revealed that the fuel has a very low ash content compared with coal.

That said, densification of the torrefied fuel still needs refinement to permit the fuel to burn more similar to coal, including for the same duration as coal per unit fired. The less dense torrefied fuel resulted in a quicker dropoff of firebox temperatures when the throttle of the locomotive was closed. These tests provided CSR with much needed data on the characteristics of torrefied biomass combustion in locomotive-style boilers, and it has provided focus for research this winter.

The cooperation of the Milwaukee County Zoo has been second-to-none in undertaking these tests, and it has provided CSR with a very good platform to undertake research. Whereas running tests in a full-size locomotive would take thousands of pounds of fuel, the Milwaukee County Zoo locomotive No. 1924 can operate a full day on 500 lbs of fuel or less. This keeps costs low in developing various fuel typologies (wood stock varieties, densification types, etc.), while still having a one third scale engine on which to test the effects of drafting and combustion.

With these tests completed, CSR is working with NRRI to undertake densification research over the winter. CSR will provide more information on those plans, including proposed future tests on standard gauge equipment, in the coming weeks.

In the meantime, please consider making a tax-deductible contribution to CSR to support the upcoming tests and research!

Firing up on coal, the locomotive had little difficulty making smoke.

Once switched to torrefied biomass fuel, the locomotive made almost no smoke.

Members of the CSR / Zoo research team pose in front of the two steam locomotives operated by the Zoo.

• People, from left to right: Davidson Ward [CSR]; Ken Ristow [Zoo]; Rob Mangels [CSR]; and Wolf Fengler [CSR].
• Locomotives, from left to right: 4-4-2 No. 1916, burning coal; and 4-6-2 No. 1924, burning torrefied biomass - both manufactured by Sandley Light Railway Equipment Works, Wisconsin Dells, Wisconsin.