ABRI-Tech provides modular biomass thermochemical transformation systems that include two main components: the biomass dryer and the pyrolysis unit, which includes the reactor, the condenser and the computer control system.
Biomass chain flail dryer
The original dryer was developed by Ken Harris of Rapid City (SD) as a mean of simultaneously drying and grinding bentonite clay for the drilling industry. Harris died before his dryer became a commercial reality and ABRI-Tech has taken over his idea for the purpose of drying biomass. The original dryer was capable of evaporating up to 10 tonnes of water per hour or about 240 tonnes per day of biomass.
The dryer in its current form has two rotating shafts with chains extending from the shaft to a couple of centimetres short of the outer cylindrical wall. The area between the two chambers is open so biomass can flow freely between the two cylinders. Heat is provided by either a gas furnace or by a custom designed biomass furnace.
As the biomass travels down the drying chamber it is continuously reduced in size and new faces are exposed. Simultaneous drying reduces the amount of energy required for drying and the grinding virtually eliminates the need for a downstream hammermill to further reduce the grain size. ABRI-Tech's dryers use approximately 25% less energy than a comparable size drum dryer. The dryer is linked directly to the pyrolysis unit. There is a small surge bin between the dryer and the pyroylsis reactor that provides control between the dryer and the reactor feed rates. The dryer feed rate is increased or decreased depending on the biomass level in the surge bin. Since the biomass is not exposed to the atmosphere after drying, the feed can be dried to below 2% RH.
Generally all pyrolysis systems have the same three basic components:
- Drying and feed
- Reactor, char and gas separation
Each of these components has to be optimized to maximize profits. Experience has shown that parasitic or the electricity required to operate the plant is a cost centre that can be reduced through diligent design. Over the years, ABRI-Tech has consistently reduced the parasitic energy to what we believe is close to a minimum. We have eliminated the costly recycle blowers common in fluid bed and circulating bed systems. Most fast pyrolysis reactors incorporate a heat carrier. We have made two fundamental changes, the first one being the use of steel shot as our heat carrier instead of sand. Steel's high thermal conductivity improves the transfer of heat from the steel shot to the biomass. The second area of improvement is keeping the profile low. It takes energy to fluidize sand or to move sand vertically in a circulating bed type reactor. Our analysis indicates we can reduce the electricity demand for a 100 tonne per day plant by approximately 1 MW. At $0.10 kW/hr, that amounts to savings of about $700,000 per year.
Fluid bed and circulating bed reactors require the heating and cooling of the fluidizing and transport gas. The size of the heat exchangers for both heating and cooling have to be increased as compared to the ABRI-Tech system where only the produced pyrolysis gas is cooled and condensed. Not only have we eliminated the electricity consumptive blowers, but our heat requirements shrink to the point where the non condensing gas will meet most of the reactor heating requirements.
Maintenance is normally estimated as a percentage of capital cost. By reducing the capital costs, by default we also reduce maintenance. Success in bioenergy means saving every dollar possible.
Considérations de conception de base
ABRI-Tech's patented and patent pending design is based on moving hot steel shot around a loop via two screw conveyors (augers). At one point, the loop (the reactor) biomass is added and is rapidly heated by the steel shot. The produced gas flows out of the reactor through a pipe. It then passes through a cyclone to remove the entrained char prior to condensation. The steel shot and char then drop into an inclined auger where the two materials are elevated enough to allow for separation of the char from the steel shot. The clean steel shot drops into the reactor for the next loop. The char is conveyed out of the system and cooled.
High heating rates
The video below shows how quickly the biomass is incorporated into the steel shot heat carrier.
Virtually all of the biomass is incorporated into the steel shot in a matter of two revolutions. We use temperature as a measurement on which to evaluate the yield of biooil and biochar, because it is easy to measure and is something we all relate to. In reality, pyrolysis is about rapid heating of biomass and the driving off of the volatile matter in the biomass. It has been shown over the years that the faster the heating rate, the higher the liquid yield.
Off the shelf and scalable
Moving materials with screw conveyors is a well established and proven technology. Augers come in standard sizes and are available from any number of suppliers. Shaft diameters, bearings, packings etc. are all off the shelf as we minimize the number of custom fabricated parts. The screw conveyors are housed in tubes and the entire system sealed to prevent intake of oxygen and hence combustion. If we assume the rotational speed of the augers is constant at all scales, then scaling up is a function of the square of the screw conveyor radius. Small increases in auger diameter make for large increases in volume of solids moved. Heat transfer through the auger shells can be calculated and the temperature differential between the oven housing the screw conveyors and the steel shot can be approximated during the design phase.
If one was to dig into the patent literature on pyrolysis systems, one would see that virtually all systems use a form of direct spray onto the hot pyrolysis vapours. The condensed and cooled biooil is collected in a reservoir, a portion is pumped back to the direct spray and the excess is pumped to storage.
Biooil contains some 300 chemicals, it is acidic, tends to form sludge and wants to repolymerize as it ages. Perhaps the most difficult part of a pyrolysis system is the condensers. Hot vapours exit the reactor and enter a cold condenser. At the interface between the cold and hot there is invariably a build up of coke. Given sufficient time, sometimes less than a couple of hours of operation, the pipes will become completely blocked. To date, the only solution to coke formation is to physically remove it via some mechanical means. There are at least two patents that show a variety of plungers that remove the offending coke. The plungers are on a timer and complete their cycle in a matter of seconds.
ABRI-Tech developed a unique coke removal device and is making the design available to the pyrolysis community without cost. We will sell you the plans if you don't want to do a little basic design work. The device is loosely based on our dryer technology. A rotating shaft with chains attached is turned by a motor. The chains are arranged in a helix down the shaft and if the shaft turns in the correct direction, the rotating shaft and chains will create a small draft that helps convey the hot vapours to the condenser. A generalized drawing for the decoker is shown in this image:
The design will have to be modified depending on the condenser design.
Conditions of sale
Given the importance of a properly prepared feedstock for attractive yields, ABRI-Tech does not allow itself to sell the pyrolysis unit without the biomass dryer.
The modules come with wired connections. Only one cable providing power to the main panel is required once the module is assembled.
The purchase price includes the necessary user manuals and two weeks of on-site training for the head operators.
The buyer is responsible for site preparation, oil storage and biochar storage.
For current price list, please contact us.
Delivery and commissioning
Normally, modular systems are ready for delivery six months after the fabricators start construction. The modules are assembled and tested prior to shipping.
The training and commissioning of the modules usually take approximately two months. Introductory training is offered at ABRI-Tech’s offices in Namur (QC), followed by on-site training after delivery.