Properly managed, wood is the ultimate renewable resource. Nothing more harmful is emitted in the conversion of wood to electricity than would be emitted as wood decays naturally in the ground. In fact, the unique process of gasification is actually more beneficial than letting wood rot in a landfill because it prevents the emission of methane, a greenhouse gas that is 25x more powerful than carbon dioxide alone, according to the US Department of Energy. Finally, landfill space is precious. By diverting more waste out of this final resting place we not only help save money we also help save further environmental damage.

With parallel operation, your business seamlessly integrates with the grid. Producing more power than you need? Spin your meter backwards and have the power company pay you! Need more power than you are generating, supplement by taking part of the power from your Phoenix Energy power plant, and part from the local utility.

Phoenix Energy's model P250 converts wood into a synthetic natural gas ("syngas" or "producer gas") through the process of gasification. This syngas is then used to fuel a specially modified natural gas genset to produce electricity and heat.

In a process very similar to manufacturing charcoal, the gasification process partially combusts wood in an oxygen starved environment. By depriving the fire of sufficient oxygen the wood does not burn, but rather gives off a flammable gas. As the wood gives off the syngas, it is transformed into charcoal and ash of approximately 1-5% of the volume of wood fuel. The syngas is then captured, cleaned and cooled before being sent as fuel to the genset. The gensets are provided by a variety of nationally known vendors such as Cummins, Caterpillar, GE and others. This ensures that there are readily available spare parts and maintenance technicians available locally in addition to support from Phoenix Energy.

Fuel preparation

Normally, but not always, our systems begin with a grinder. This processes cut ends, culled lumber, scrap and other wood waste into a consistent size. This is also the most fault tolerant system in case some metal finds its way into the waste stream (binding straps, soda cans, etc.) The fuel is then fed into a storage hopper.

Gasification

Wood is then fed by means of a belt conveyor or elevator to the top of the gasification chamber. There wood is fed through an airlock into the chamber. The inside of the gasifier is essentially an open column; however several different processes take place inside as the wood travels towards the bottom.

Wood gets dried, heated, pyrolysed, partially oxidized and reduced in this reactor as it flows through it.

Although there is a considerable overlap, each process can be considered to be occupying a separate zone, in which fundamentally different chemical and thermal reactions take place. The fuel must pass through all of these zones to be completely converted. The downdraft gasifier is under vacuum drawn by a high-pressure blower. The essential characteristic of the downdraft gasifier design is that the tars given off in the pyrolysis zone are drawn through the combustion zone, where they will be broken down or burned. When this happens, the energy they contain is usefully recovered and the mixture of gases in the exit stream is relatively free from tars.

Gas Cleaning

After the syngas has been extracted from the gasifier it is cooled and cleaned by a series of scrubbers and filters. First the gas passes through a venturi scrubber, which removes particulate matter. The gas is then passed through a series of four filters. The first is a coarse filter to coalesce residual liquids. The second is a rejuvenating active sawdust filter, the third is a similar passive filter, and the fourth is a fabric bag filter. The filter media are sawdust and wood chips so instead of using expensive synthetic filters that need to be thrown away, the used filter media are simply placed into the fuel hopper and consumed.

Power Generation

Our normal proposal for electricity generation is based on natural gas gensets. Our systems are modular and can be set up for a variety of power needs, 50 or 60 Hz, 3 phase, 240 to 250 kW. If more power is needed, our units can be stacked in a modular format allowing for addition power in increments of 100 kW.