BioCycle January 2007, Vol. 48, No. 1, p. 24
Particle size reduction is an important processing step in organic materials recycling, whether for composting, biomass energy recovery, or manufacturing recycled products. For the most part, this is due to a need to manage the biological or chemical process by optimizing the particle surface area-to-volume ratio. Grinders have long been used to achieve this optimization, particularly for vegetative debris.
This article is the first of a new series here at BioCycle. Each month, in this What’s New? series, we will profile developments in various types of equipment important to those engaged in organic materials recycling. This article on grinders is an update to last year’s report on grinding equipment (see “Wood Recycling Equipment Trends and Innovations,” January, 2006).
Grinders, shredders, and chippers are types of equipment used for size reduction of various materials such as wood wastes, yard trimmings, landclearing debris, MSW, paper, plastic, etc. The primary objective is to reduce large particles to small ones by physically breaking them apart. Grinding equipment can be classified as chippers, shredders, hammermills, toothed rotor grinders, and screw-type cutting blades. As most composters are familiar with the use of hammermill-type grinders for particle size reduction of vegetative debris, this article is focused on that application.
The following grinder manufacturers were contacted for this article: Bandit, CBI, Diamond Z, Doppstadt US, DuraTech, Morbark, Peterson, Powerscreen, Rotochopper, SEKO, Sundance, Vecoplan, and Vermeer (see accompanying Grinder Directory for contact information and additional grinder suppliers). Questions included new offerings for 2007, improvements in safety and durability, engine compatibility with alternative fuels and more stringent air quality regulations, and types and levels of technical support. Each manufacturer also was presented with three hypothetical grinding scenarios common to composters and wood waste recyclers. For each scenario, the manufacturer was asked to recommend a particular machine, and to provide estimates on operating hours, fuel consumption, annual cost of routine maintenance, and likely equipment capital cost. The information reported here was supplied by the manufacturers and not independently verified by BioCycle editors.
NEW FEATURES, UNITS
Grinder manufacturers plan to offer several types of improvements in 2007, although only two are introducing new machines:
Bandit Industries: Equipment improvements to the grinder line include newer, longer lasting teeth, easier screen changing, a hammermill option, an Iqan (variable speed) Feed System, more features on the radio remote controls, an ungrindable material release system, and an improved material discharge system able to handle the greater flow of material from the increased production of their newer recyclers.
CBI: Would not reveal its plans for 2007, but noted its grinders are equipped with different rotors that can operate at varying speeds and rotational directions depending on the feedstock being processed, e.g., a solid steel rotor in a downward rotation at a slower speed for mixed C&D debris, and a higher speed forged rotor with replicable hammers in an upward rotation for clean wood or green waste.
Diamond Z: Unveiling the DZH7000 tub grinder with the 1200 HP Cat C-32 engine on tracks.
Doppstadt: Introduced the AK530 grinder, which incorporates automatic load sensing on the infeed, a one piece hydraulic screen cage that can be changed in less than 10 minutes, and self-propelled hydraulic drive on the wheels to allow for building windrows and variable angles on the discharge conveyor. The control system is simplified and the unit comes standard with a 16 channel full remote control.
Dura Tech: New 950-hp horizontal grinder, the Model 9564, will include its microprocessor-controlled wet clutch system for transferring power to the hammermill.
Morbark: Primary improvements are to introduce a new, redesigned Model 3600XL horizontal grinder, with dual belt discharge, increased tip swing and tip speed in the hammermill, and an internal drive on the feed wheel. Morbark also plans to add a 1200-hp engine to its Model 1600 tub grinder and to make the Model 2600 horizontal grinder available with tracks.
Peterson Pacific: Improvements to the grinder line include refinements to the rotor, impact release system, and grate fastening system; more aggressive infeed; simplified control systems for easier set up and trouble shooting; improved track power on all track mount machines; a revised remote control system to allow all basic operational functions to be done via the remote control; and improved discharge to minimize belt tracking issues associated with operating the machines on unlevel surfaces.
Rotochopper: Introducing a liquid grind and color system on its B-66 horizontal grind for making colored mulch.
Vecoplan: Introduced HiTorc energy-saving devices on its line of stationary preshredders and reshredders.
Vermeer: Introducing a new mid-size tub grinder in the 50,000 to 60,000 lb class.
SAFETY AND FIRE SUPPRESSION
Anyone who has operated either a horizontal or tub grinder knows how potentially dangerous these machines can be. All of the manufacturers offer significant safety features. Vermeer offers the patented Thrown Object Restraint System on its tub grinders – a two piece restraint design that uses a conical shield on the tub that can be hydraulically positioned either over the tub or over the engine enclosure via control station, cab or remote. In addition, a rotor deflector plate is bolted to the table on the upswing of the mill to help direct material toward the conical shield. This slows the momentum, thus reducing the distance and amount of thrown objects. The horizontal line also uses a deflector that is hydraulically controlled.
Bandit will introduce an ignition delay warning siren on its grinders in 2007 to alert those in the vicinity of the machine that the grinder is about to be started. Vecoplan offers interlocked hydraulic shutters or doors on the sides of its low-speed, high-torque machines for controlled access to the cutting chamber. This provides easy access for both maintenance and removal of foreign bodies. Maintenance can be done from the outside of the machine without having to climb inside the unit. Diamond Z is introducing two new features – safety mill locks to keep the mill from moving while changing hammers, and a tub safety switch to prevent the tub from being opened while it is rotating. Rotochopper minimizes flying debris with a down-cut rotor, an enclosed grinding chamber, and a wide (36-inch diameter) power feed wheel.
Morbark’s safety features include internal drives on the feed wheels on all horizontal models, which eliminate moving parts such as chains and sprockets; electric controlled clutches that are engaged and disengaged at the touch of a button; optional fire suppression systems; hydraulic rod pullers, which eliminate some of the difficult physical labor of changing hammers and rods; and power packs that enable hydraulic functions to work without starting main power units.
Peterson’s planned safety improvements for 2007 include: improved air flow around engine to reduce build up of wood debris; revised shielding around engine, exhaust system, and hydraulic components; supplying a water tank and pump on all diesel grinders to clean units for fire prevention; and improved access to engine and maintenance areas. Dura Tech will offer optional fire suppression systems on all of its grinders in 2007. The fire suppression systems are made by AFEX Systems (www.afexsystems.com) and consist of fire detection sensors, automatic chemical fire extinguisher activation and shut-down of the grinder engine.
Grinders are subject to very high levels of wear and tear so manufacturers offer various features to improve durability. Many of these features are designed to minimize damage to the grinder from contaminants. Peterson offers two damage-avoidance mechanisms in its grinders – standard equipment is the Impact Release System (IRS) where the anvil and sizing chamber are held in a fixed position until the force exceeds the set limit. At that point, the system opens to release the noncrushable material. An option available from Peterson is the Floating Anvil System that allows the anvil and first grate to float in order to bypass noncrushable material. The float pressure is adjustable. In an extremely contaminated application, this system is run in conjunction with a half grate section removed and a baffle plate to reduce impact on the discharge conveyor. Other durability improvements offered by Peterson include: an optional reduced rotor speed specifically for heavy duty applications; refinements in the grate retaining system; and an optional heavy duty discharge conveyor belt. Diamond Z has strengthened the mill wall by adding thicker steel.
Recent durability improvements from Morbark include: stronger hammers and inserts with increased life and precisely balanced, laser-cut mills, which eliminate most vibration. The company has always offered a torque limiter that stops the hammermill when encountering ungrindable materials. It can also include the PT Tech clutch with internal torque protection, along with the torque limiter, for dual protection against contaminants. Vecoplan now offers indexable and replaceable cutting inserts in their line of electric-powered shredders in lieu of the resurfaceable tables they offered previously. Bandit Industries offers thicker screens (on most models), a re-engineered anvil assembly, a more durable infeed conveyor chain, new and improved drives for the infeed conveyors, an improved hard surface, carbide impregnated weld on standard cutter bodies (designed to increase their longevity), more durable tooth options and a new heavy duty hammermill option. CBI’s durability features include the use of flanged rotor bearings built into the frame of the grinder rather than weaker pillow block bearings for the main rotor bearings, and a practice of sandblasting all painted components before assembly and priming (which can reduce corrosion).
Doppstadt grinders, which use a swing hammer configuration, are equipped with a nitrogen accumulator back-up for its hydraulically adjustable screen. This allows contaminants to be released and the screen to reset automatically. The Doppstadt AK series grinders incorporate as standard a fluid coupling drive system, alleviating any potential for clutch failure in heavily contaminated materials. The company also notes that its DW series Slow-Speed shredders, with throughput capacities from 20 tons/hour to 125 tons/ hour, are designed for material that is too contaminated to be processed efficiently and cost-effectively by its high-speed grinders.
Vermeer’s horizontal grinder line offers a removable anvil that can be taken out from either side of the machine at ground level to facilitate maintenance. Bolt-on wear liners are available in the mill lid that can be easily replaced and monitored by the operator.
ENGINE FUELS AND EMISSIONS
The two main suppliers of diesel engines to nonelectric-powered grinder manufacturers are Caterpillar and Cummins. Manufacturers were asked about the ability of their equipment to run on biodiesel. Using biodiesel in off-road equipment applications can reduce air pollution emissions relative to traditional distillate diesel fuels, with the exception of nitrogen oxide emissions. Most of Caterpillar’s newer and higher horsepower diesel engines can use up to a 30 percent biodiesel blend (B30), provided the biodiesel meets Caterpillar’s specifications (some of the smaller horsepower engines are limited to a maximum of 5 percent biodiesel). Cummins 2007 engine platforms will continue to offer B5 biodiesel capability while the manufacturer continues to evaluate the suitability of B20 biodiesel. All of the grinder manufacturers (with the exception of CBI) using diesel engines indicated some compatibility with biodiesel.
In terms of emissions requirements for nonelectric-powered grinders – which fall into the off-road sources – the federal Clean Air Act has tiers of regulations with a defined set of standards for allowable emissions per tier, per horsepower range. Each progressive tier has an objective of reducing levels from the previous one. In 1996, Tier 1 for off-road applications became effective. Current Tier 2 regulations are in force for a large portion of off-road products. The next wave of regulations affecting off-road machines, Tier 3, goes into effect over the 2006-2008 time period, depending on engine horsepower rating. Both Caterpillar and Cummins now provide engines that meet the new Tier III standards. “We have updated our complete product line in order to meet the emissions standards,” says Cody Peterson of Peterson Pacific. “Although the new engine packages are a substantial cost increase, there is some return to the user in reduced fuel consumption and engine maintenance cost. The engines built from the ground up to meet the emission standards are much more efficient than the engines that were modified to meet the standards. We are very pleased with the performance of the Cat C-18 and C-27.” Hugh Fagan, Sales Manager of Doppstadt US, notes that all Doppstadt units meet Tier III emissions standards for 2007.
While retrofitting older diesel engines to meet new air emissions standards is not currently required, the California Air Resources Board is considering regulatory action (called “The 5 R’s”) that would require: Retrofit older engines with new technology that controls emissions; Repower the equipment with new, cleaner engines; Replace the equipment with new machines with cleaner engines; Rent new equipment with cleaner engines; and Reduce idling.
Most grinder manufacturers operate through a network of dealers supported by field and factory-trained technicians. Morbark’s factory service personnel supply troubleshooting assistance over the phone. In addition, Morbark’s IQAN system offers satellite linkage to the factory for diagnosing machine functions in real time. Vermeer keeps factory-trained grinder specialists assigned to dealer “networks” who devote whatever time is needed to support purchasers of its grinders. Peterson customizes maintenance contracts based on the level of service desired and also offers an extended warranty. In addition to a standard paid service and warranty, Vecoplan offers a Preventive Maintenance Program tailored to a customer’s needs; therefore the price varies.
In CBI’s case, the company deals directly with the customer and “takes out the middle man (dealer) so we can keep our finger on the pulse and know exactly what is going on with each customer,” says Tim Griffing of CBI. “We have Field Service Engineers living in different parts of the country with fully equipped service trucks including satellite and computers to allow for a much more efficient program.” Bandit offers similarly tailored service plans. “Bandit has 12 service technicians based out of the factory,” says Travis Lint of Bandit Industries. “This group of extremely dedicated personnel continually travels the country making courtesy calls at customer locations and servicing our line of horizontal grinders. In some areas of the country, we have dealerships that are very well equipped and factory trained to handle customer needs.”
Because of the variations in equipment as well as types of feedstocks processed, we provided manufacturers with three hypothetical grinding scenarios. Nine manufacturers responded to the following three scenarios with their equipment recommendations:
Scenario #1: A yard waste composting facility, processing 200 tons/day (tpd) of incoming yard trimmings (nothing larger than 6-inch diameter), with peak monthly tonnage of 450 tpd during three months in the spring. All processing is done on an asphalt pad. The yard trimmings have minimal contamination. The desired ground particle size is 2-inch minus.
Scenario #2: A vegetative storm debris processing site, unimproved (bare earth), with 150,000 tons of accumulated storm debris on-site (nothing larger than 24-inch diameter). The storm debris has some contamination. The desired ground particle size is 4-inch minus.
Scenario #3: A composting facility, taking in 75 tpd of waste pallets from various sources and 60 tpd of offcuts and 75 tpd of debarking waste from a lumber sawmill. All processing is done on an asphalt pad. The wood waste has minimal, if any, contamination. The desired ground particle size is 2-inch minus.
For each scenario, the manufacturers were asked: What model of grinder would you recommend? How many operating hours per year is anticipated? How much annual fuel consumption is anticipated? What is the expected annual cost of routine maintenance? What is the likely capital cost of the equipment?
The comparisons in Tables 1-3 are presented for general information only and are based entirely on information supplied by each manufacturer. Claims and information presented have not been independently verified. To the extent possible, the editors of BioCycle have attempted to ensure that all information presented reflects the same basis and data across all manufacturers, however, considerable variation was found in manufacturers’ estimates of routine maintenance costs. All manufacturers based their estimates on nonfuel “consumables” – the definition of which varied by manufacturer and is noted in the footnotes. The grinder manufacturers will almost always provide demonstrations to qualified purchasers. Thus, actual results can be verified for each manufacturer before the customer makes a purchasing commitment. Interested readers should contact manufacturers directly for information tailored to their specific needs.
Craig Coker is a Principal in the firm of Coker Composting & Consulting in Roanoke, Virginia, who specializes in providing technical support to the composting industry in the areas of planning, permitting, design, construction, operations and compost sales and marketing.