Paulownia

4. Paulownia

Paulownia (PGX1002)

Paulownia is an economically important genus in the family Scrophulariaceae, comprising of nine species of very adaptable and fast growing timber trees¹. The value of Paulownia for afforestation¹ and mine reclamation²  has previously been demonstrated. Whether in intercropping systems³  or managed plantations, Paulownia trees produce leaves useful as fodder or fertilizer, flowers for medicine or honey production and wood for solid wood products¹. Paulownia is also an excellent choice of feed stock for bio-mass  to energy production  due to its fast rotation cycles and  excellent  gasification profile.

In 2006 the Queensland Department of Primary Industries tested a cross section of 4 year old polygenomic Paulownia for wood fibre density and growth. Click  DPI density test to view full results. In summary the results showed that the average density of a 10 year old non-polyploid Paulownia at 263 kg/m3 was not significantly different from the 4 year old polyploid (polygenomic) sample at 261 kg/m3.

Average growth ring size over 4 rings for non-polyploid was 20.24mm, and was shown to be significantly less than average growth ring size of 27.20mm for the polygenomic sample.

Hence the Polygenomic sample showed an average 34% increase in growth, and was the same size and density as a 10 year standard Paulownia tree!

Click Paulownia density report  to read the comparison of the 2006 results and the 2011 results.

This new PGX1002 clone is set to revolutionize the production of feed stock for the bio-energy Industry based on fast-rotation cycles and enhanced burn characteristics, hence adding hundreds of years to any existing breeding program.

PGX1002 as feedstock

Normally, the dryer the fuel the higher the energy density and the better the quality of low Btu gas produced so, the biomass from the plantation will be dried using waste heat from the gasifier to 10%.

PGX1002 chars quickly but has a relatively high ignition temperature of approx 400°C in reduced oxygen. Thus it smoulders within the reaction vessel.

With the heat released by the char a fixed quantity and while using a constant air flow, the more moisture in the fuel, the more heat consumed by evaporation. Less energy remains for volatilization and sensible heat, so the fuel rate must be decreased. Consequently, less volatiles are produced and both the combustible gas quality and quantity are reduced. As such, only dried feed stock will be used.

The gasification process occurs as a result of three linked events:

1. Pyrolyses: The conversion of solid fuel to CO, CO2, H2, CH4, H2O, char, tars and hydrocarbons.

2. Gasification: The conversion of the pyrolysis products to syngas (H2 and CO).

3. Partial combustion: Combusion of some of the pyrolysis products liberates the heat necessary to drive the gasification process.

The gasification process occurs in a reduced oxygen atmosphere. Typically 20-45% is required for combustion of syngas.

Normally, when chips of timber are introduced to the gasifier, a series of consecutive degradation steps occur under high temperature.

• First, the moisture is driven off.

• Second, the outer layer is converted to volatile gases leaving char and ash.

• Next, fluidized sand ablates the char revealing a clean reaction surface and the char is oxidized within the bed to provide heat for the process.

This cycle occurs over a period of seconds causing small spikes and dips in the temperature of the fluid bed. These in turn, reduce the energy [BTU] quality of the gases produced.

However, with PGX1002 these processes occur almost simultaneously, producing a constant evolution of gases and even burn rate for the char. As a result, the gasifier can be run at optimum efficiency.

Low Phenolics

During pyrolysis plant phenolics are released into the reaction chamber. These chemicals degrade the reaction vessels walls such that approx every two years the chamber walls need to be replaced.

PGX1002 produces negligible phenolics thus alleviating the need for this costly maintenance procedure.   (The test results below are for PGX1002, though bearing it’s laboratory designation ALC1002)

An ideal biomass feed stock will be fast charring, with a high ignition point; will have a low density but a high energy value per tonne; will produce low or no phenolics or toxic by-products; its surface should ablate and gasify readily; and, from a production point of view, it should be hardy and fast growing.

PGX1002’s gasification characteristics and growth performance make it the ideal biogas feedstock.

PGX1002 wood easily carbonizes a rate 1.6 times faster than cedar.

PGX1002 Syngas Feedstock – Comparative Energy Yield
feedstock PGX1002 Electricity Grade Coal Black Coal Cedar
kw hour/ton 2909 4444 8888 2897
30% converstion 873 1333.2 2666.4 693

PGX1002 Syngas Feedstock – Comparative Energy Yield

1. Zhu et al, 1986
2. Carpenter, 1977
3. Wang & Shrogen, 1992