ENERGY SOURCE ESI. A Newsletter published by. The Steam and Power SPECIAL FORCES

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1 ENERGY SOURCE A Newsletter published by ESI The Steam and Power SPECIAL FORCES Summer 2010

2 Consider This... Designing a Successful Biomass Material Handling System Part 2 : Material Receiving System Design Written By: Jeffrey H. White, ESI Chief Operations Officer Editor s Note: This is Part 2 in a series of articles on Designing a Successful Biomass Material Handling System. Part 1 appeared in the Spring 2010 issue of Energy Source. Previously, we explored the importance of understanding how material properties affect the proper design of a successful biomass handling system. Properties discussed included: Density, Material Sizing, Angle of Repose, Tendency to Bridge, Material Moisture, Flammability, and Friability. In this article, we will delve into some areas to be considered when designing a material receiving system. ESI classifies the material receiving system as the part of the system which unloads the material from whatever transportation medium is used to deliver the fuel and conveys the material to short or long term storage. Fuel Delivery Options The method for delivering biomass to a power plant is largely a function of the type of material being combusted and the material s location relative to the power plant. By far the most common delivery method of biomass is via truck, either self unloading or not. Most of the biomass being used for power production today is woody in nature and comes from waste materials such as tree trimmings and thinnings. Due to its relatively low density and high moisture content, it has been impractical to transport the material more than a mile radius from the plant. This makes the use of trucks the most likely mode of transportation. Also, unlike coal which usually has a rail spur available at the mine mouth, the woody biomass wastes described above are harvested over thousands of acres making the installation of a rail terminal impractical. In the future as more energy crops are developed, it may become more practical to consider a combination of rail and truck delivery. Having said this, a small percentage of un-pelletized biomass is available by rail. As the markets grow, more and more pelletized biomass is becoming available via rail. The third and less ENERGY SOURCE The ENERGY SOURCE is published quarterly for customers, employees, and friends of ESI Inc. of Tennessee. ESI is the Steam and Power SPECIAL FORCES providing clients with innovative, cost-effective, and environmentally-friendly solutions. If you have any suggestions or comments about the newsletter, feel free to call us at or us at energysource@esitenn.com. Vickie Hoffman Managing Editor ENERGY SOURCE 1 common option for biomass delivery in the US is via barge. While it is relatively common for pelletized wood to be sent via barge to Europe to facilitate compliance to the European renewable energy mandates, the infrastructure for domestic delivery of the biomass via barge is in its infancy. Truck Delivery - Each of these delivery options has its own unique challenges which must be overcome to create a successful operating scenario. When dealing with truck delivery of biomass, a Continued on Page 2

3 ...Continued from Page 1 lot of the issues are caused by the sheer volume of the material to be delivered and the number of trucks necessary to deliver that volume. A typical truck will hold approximately 22 to 25 tons of woody biomass, so a 50 MW plant can require as many as 95 trucks during a 24 hour period just to maintain supply. More often than not, biomass is only delivered during the daylight hours and is very rarely delivered on the weekends. Therefore, the receiving system must handle all the fuel deliveries during daylight hours five days per week. This can become a logistical nightmare. Truck Tipper *photo courtesy of BRUKS Biomass is commonly delivered in both self unloading (live bottom or dump type) trucks and standard open top tractor trailers. Self unloading trucks are typically either discharged onto the ground and then handled via a front-end loader or preferably discharged into a live bottom receiving hopper and conveyed to the sizing and storage systems. Open top tractor trailers must be unloaded via a truck tipper onto either the ground or preferably into a live bottom receiving hopper. Truck tippers are hydraulically driven units which lift either the trailer alone or the trailer and truck together. Two varieties of truck tippers exist: the back on type and the drive through type. The back on type is less expensive but forces the truck driver to stage and position the truck onto the tipper. The drive through type is more expensive but reduces the positioning time of the truck; however, drive through designs usually are more difficult to clear in the event of a jam in the receiving hopper due to their design. Barges containing coal. Barge Delivery - As mentioned previously, domestic biomass delivery by barge is not common currently. Typically the costs for this delivery method are higher than truck delivery. This is largely because trucking costs must be incurred anyway to get the biomass to a port for loading onto a barge, so the barge costs are in addition to the trucking costs. Most biomass that is delivered via barge is in a dried and pelletized form. There are several reasons why. First, unprocessed biomass often contains between 30-55% water. Essentially, it is expensive to ship Continued on Page 3... ENERGY SOURCE 2

4 ...Continued from Page 2 water which has value. Secondly, the pelletizing process greatly increases the density of the material being shipped (for woody biomass there is as much as a 66% increase in density). This enables more mass to be contained in the same volume, decreasing shipping costs. Finally, un-dried biomass which is piled on top of itself will generate heat. Due to this fact, there is a concern that green biomass stored in a barge for a long period of time could begin to smolder and catch fire. Regardless of whether the biomass is processed or green, there are two common methods of removing the material from a barge: pneumatically via a vacuum system, or via a mechanical clamshell. A pneumatic system is basically a stationary filter receiver Mechanical Clamshell to unload barge material. mounted at or near the shore line with high pressure vacuum blowers and a hose. The hose is placed in the barge and the material flows up the hose and into filter receiver. From there it is discharged to a conveyor system. A mechanical clamshell consists of a hydraulic or cable driven clamshell which is lowered into the barge and takes a bite out of the material and lifts and dumps it into a hopper on or near the shore. Either method has unique issues to be overcome including dust control, degradation of the materials, weather protection and spark or fire suppression. Rail Delivery - Although not common, biomass can and is delivered by rail. Biomass delivered by rail can include processed materials such as pellets, unprocessed materials such as wood chips or waste fibers, whole trees and in the future, baled energy crops. Most processed biomass is delivered in bottom dump cars with large open hoppers. In cold climates, bottom dump cars can be difficult to unload due to the inherent moisture in certain biomass products. In addition, due to the stringiness of waste materials, it is very difficult to completely empty the rail cars. Therefore, rail car shakers and thawing sheds are required to Continued on Page 4... Rental Boilers Deaerator Systems Water Softener Systems Economizers ENERGY SOURCE 3

5 ...Continued from Page 3 insure a dependable supply is available. Rail car receiving hoppers should be carefully designed to eliminate positive angles so that the potential for bridging is minimized. If stringy material is anticipated, a live bottom hopper consisting of either screws, drags or hydraulic live bottom floors is necessary to properly receive the material and transfer it to the conveying system. Other Considerations - No matter which delivery method is considered, there are several common areas which need to be understood and considered to insure the system is designed appropriately. Among these, the most critical is to have a good understanding of the realistic delivery schedule. Each one of the methods discussed has unique limitations. For example, as stated previously, biomass is normally delivered only during the daylight hours and rarely on the weekends. Extended rain or cold weather will mean that the supply could be interrupted for days at a time. Freezing weather can cause barge delivery to stop until the waterways are clear. For those reasons, it is critical to design ample capacity in the receiving system so that when fuel interruptions occur, it will be possible to catch up when the fuel supply is reinstated. Another big factor to be considered is dust control. Biomass is inherently dusty and under the right conditions the dust can be explosive. With each of the delivery methods described, a large volume of material is discharged at a rapid rate. Extremely dry and fine material can cause a dust cloud. In many cases it will be necessary to control this dusting by enclosing a portion of the process and pulling a vacuum on the enclosure to capture the free dust. To do this, large volumes of air are drawn through cyclones and bin vents. The captured dust can then either be handled separately or discharged onto the take-away conveyor. Consideration for explosion relief and fire suppression is critical in these dust handling applications. In some installations, consideration should be given to spraying a surfactant on the material either before or as it is unloaded. We hope that you now have a basic understanding of the methods by which biomass is currently delivered. Whether the material is delivered by truck, rail or barge, careful consideration of design details is required to insure successful operation. In the next issue of Energy Source, Part 3 of this series will discuss the topic of material stack-out, sizing and storage. In the meantime, ESI offers its expertise to assist customers considering biomass by offering a variety of services ranging from engineering design to complete guaranteed EPC system installation. ESI has the experience and professional capability to prevent the catastrophic design issues which so often affect biomass facilities. For more information contact Jay Garrett at or jgarrett@esitenn.com. Visit us at Scott Adams / Dist. by United Feature Syndicate, Inc. ENERGY SOURCE 4

6 Project Updates DTEES Stoneman Project Nearing Completion: ESI is nearing completion of the 54MW biomass conversion project for DTEES at their Cassville, Wisconsin facility. ESI began work on the engineering and procurement of the facility components in April The project consisted of the conversion of two pulverized coal-fired boilers to burn biomass and included the installation of a new material sizing, storage and handling system, a new biomass stoker, a SNCR system and new fans. ESI is excited to continue work as the engineering and procurement supplier for this biomass conversion project. This green energy project will reduce carbon emissions and help improve the environment. ESI s expertise is showcased very well with this project, stated ESI s Chief Operating Officer, Jeff White. Ameresco Federal Solutions Savannah River Facility: ESI is completing engineering for the 20 MW Ameresco Biomass Cogeneration Project at the Savannah River Facility in Aiken, South Carolina. Engineering design for this project began in May 2009, using Bentley 3D software. The 3D model developed will be used by the contractor for piping fabrication and erection, providing the most efficient method for conveying design information from ESI s engineering team to the contractor. The project includes a complete scope of supply for a greenfield operating cogeneration facility consisting of two 120,000 pph biomass-fired bubbling fluid bed boilers providing steam to a 20 MW turbine generator with an extraction to provide steam to the process; site work; concrete; foundations; buildings; structural steel; waterside auxiliaries; water treatment; material handling and storage bins for biomass, ash, and limestone; stack; distribution and plant piping; electrical, instrumentation and control system; electrical systems, including power distribution and utility interconnects; and other miscellaneous systems. Currently, construction is underway with site grading complete, foundations nearing completion, and erection of the boiler equipment beginning. Start-up for the Savannah River Facility is scheduled for mid Join ESI s SPECIAL FORCES Visit our website for open positions and to apply. ENERGY SOURCE 5