Medium to Large Scale Biochar Production
Horizontal Bed Biochar Reactor
The above unit can be used for a variety of feedstocks, it has a pre-dryer, incorporates the ability to closely control process parameters of temperature and residence time. It will a) produce biochar from nearly any feedstock b) condense wood vinegar from the raw syngas stream, c) crack and filter the raw syngas remaining after the condensation step to produce a clean mixture of hydrogen and carbon monoxide, known as syngas, and d) optionally burn the syngas to generate electricity. Syngas can also be used as a replacement for natural gas or propane for heating purposes.
The challenge we are attempting to address with this system is to maximize the potential for profitability, in particular by monetizing the gas stream in the most economical way possible. In this regard, we have developed a very inexpensive catalyst to crack the syngas for this device. We estimate that the revenue from the combined products of biochar, wood vinegar and electricity should recoup the investment cost for this unit within approximately 4 - 6 months of operation.
This biochar kiln is manufactured in a modular fashion, in 3 main sections, and its throughput capacity can be easily increased by adding units to the mid-section to make it longer. Its functional capacity can be enhanced by adding sections to fractionate the condensate yield, producing essential oils or chemicals like terpenes for instance. A section can also be added to the end to convert the char to activated char. The feedstock stream required for the lowest capacity unit would be about 16 tonnes of wood chip (@ 20% moisture content) per day. The unit is intended to run 24/7. Once started, this kiln is self-sufficient in terms of energy. Startup is accomplished with either natural or bottled gas.
The lowest capacity plant will produce, per day, about 4 tonnes of biochar, 2500 liters of wood vinegar, and (optionally) 8400 kWh of electricity. We conservatively estimate revenue per day to be $150 x 4 for the biochar, $1 x 2500 for the wood vinegar, and $ 0.05 x 8400 for the electricity, 600 + 2500 + 420 = $3520 per day. Note that the rate paid for electricity is often at least double the above estimate. The kiln will cost approximately $400,000, and the optional motor genset designed to run on cracked syngas will cost approximately $450,000 - $550,000.
Heat energy to dry and pyrolyse the feedstock is provided by flaring a portion of the syngas produced and/or recycling waste heat from the reactor and genset. The unit requires a relatively small amount of electricity to run the blowers, feed mechanisms and control electronics. Hence once it reaches operating conditions, it is entirely self-sufficient in terms of energy.
Tilting Batch Biochar Kiln
The tilting batch kiln is designed to produce biochar from sticks and split wood. The tilting mechanism allows for easy loading and unloading of the unit. It is also possible to configure 3 units in a round-robin fashion so that the excess heat from one is used to start the pyrolysis process in another. These units require no electricity, but there may be more manual labor involved in preparing the feedstock, loading and unloading.
Batch Kiln 100-MK 1
Simple and easy to use, this kiln has a cylindrical body 1.2 meters high and 1.5 meters in diameter. The kiln has an internal combustor (firebox) which hangs from the lid and provides heat to convert the feedstock to biochar. It takes about 8 hours for a batch to be processed, depending on the moisture content, type and size of the feedstock.
The kiln is loaded from the top, and unloaded through a door at the bottom. A hand-driven winch is used to remove the lid for loading. After a burn, the kiln is left overnight to cool before unloading. A single batch can produce up to 100 kg of biochar.
The kiln runs on a two stage cycle. First the feedstock is dried, then it is charred. The design relies on air convection to distribute heat throughout the feedstock bed. It is for this reason that feedstock is limited to split or small diameter wood. During the drying stage small logs are burned in the firebox to provide heat. As temperatures within the kiln rise to around 450 C, the feedstock releases syngas. Once syngas is available, it is burned in the combustor to maintain suitable charring temperatures.
The kiln is transportable on a small trailer. It is therefore likely that in most areas, planning permission would not be needed. It does however produce some steam and smoke, so it is advisable to locate it away from buildings and people. The kiln does not need electricity to run. It uses a leaf blower included with the kiln to supply air to the internal combustor.
Batch time: around 8 hours
Moisture content: up to 40%
Feedstock size: logs, up to 30 cm in length and 10 cm in diameter
Feedstock type: Wood
Feedstock volume: 1.5 cubic meters
Fuel source: logs, up to 15 cm in length and 5 cm in diameter
Char yield: up to 100 kg per batch
Infrastructure used: handheld leaf blower (provided with the kiln)
Price: ~ 8000 Swiss francs
Batch time: variable, up to 8 hours
Moisture content: up to 60%
Feedstock size: from rice husk, wood shavings and wood chip up 30 cm length logs
Feedstock type: most types of biomass
Feedstock volume: two kiln bodies or retorts of 6 cubic meters each
Fuel source: woodchip
Char yield: up to 750 kg per cycle (per 6 m3 retort)
Infrastructure used: 4 electric fans and a generator (provided with the kiln)
Price: ~75,000 Swiss francs excluding shipping
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