As the old saying goes, one man’s trash is another man’s treasure. And in the case of Montenay Energy Resources of Montgomery County Inc. (www.montenayenergy.com), a waste-to-energy facility located in Conshohocken, Pa., many a man’s trash is being burned to produce an unending treasure of electricity.
Go with the flow
Each day, Montenay Energy processes tons of household garbage and municipal solid waste at its 20-acre site. Here the waste is converted to thermal energy, which is used to produce electricity for 30,000 homes. No, it’s not magic, but it is pretty amazing that this facility can burn trash 24 hr/day and reduce the solid waste by 90% in volume and by 75% in weight. For every 100 tons of trash, Montenay Energy generates more than 50 MW of electricity and sends just one tenth of the volume to the landfill in the form of ash. Many, including the Environmental Protection Agency, approve of this process as an alternative to discarding tons of garbage in landfills, especially because the garbage never stops coming.
Montenay Energy recently upgraded the system that helps control the rate at which trash is fed into the incinerator. Many difficulties plagued the older hydraulics responsible for this portion of the process, but with the help of the Bosch Rexroth Hydraulics service group in Bethlehem, Pa., Montenay successfully incorporated the new equipment into its facility.
For years, Bosch Rexroth has designed hydraulic systems used in waste-to-energy facilities from New York to Newark. Typically, hydraulics is used within the incineration process to ram or feed the trash into a large boiler and then extract the ash. When Montenay needed to enhance its current hydraulics system, plant operations and maintenance manager John Polidore consulted with Bosch Rexroth service engineer Keith Metz. The two had worked together on a previous project at Montenay to solve a corrosive hydraulic fluid problem. According to Polidore, he was so pleased with the results of their initial work and the ensuing relationship with Metz that he felt comfortable calling on Bosch Rexroth again for help on this major overhaul.
Montenay’s hydraulic system was designed in Germany and used a main power unit with 24 submersed gear pumps. The gear pumps set the flow rate for multiple sets of identical cylinders that feed the trash into the boiler by controlling the movement of grates within the boiler. The grates are moving plates inside the boiler that shuffle the trash along as it burns. The problem with the design, as Polidore knew and Metz quickly discovered, was that the fixed-displacement pumps caused the grates to move and then stop for a variable period of time, depending on the process conditions. During the stopped periods, weldments would frequently occur, causing the grates to seize and resist movement. This, in turn, would eventually force the unit to be removed from service for repairs. In addition, the gear pumps were stacked together and submersed in a tank, making them difficult to access and repair.
Metz offered Polidore an approach that called for the replacing Montenay’s 24 gear pumps with four pressure-compensated A10VS0-DR size 18 pumps. A pressure controller maintains a constant pressure within the range of the pumps; therefore the pump unit supplies only the amount of pressurized hydraulic fluid required. The pumps then pass the flow through model 2 FRE 6 proportional flow control valves. The two-way proportional flow control valves allow an electric signal to control the fluid flow independent of pressure and temperature variations. Each valve assembly comprises a proportional solenoid with inductive position transducer, a metering orifice, and a pressure compensator. The valves are controlled by VT 5010 electrical amplifier cards with electrical position feedback, and the cards are commanded by Montenay’s existing PLC.
Polidore accepted Metz’s proposal, and Bosch Rexroth assembled a temporary unit at its facility and delivered it to Montenay as a complete power unit for testing. Airline Hydraulics Corp., a Bosch Rexroth distributor located in Bensalem, Pa., helped test the power unit by operating the entire feed system for one boiler to prove the unit could control the cylinders using the model 2 FRE 6 valves and VT 5010 driver.
“Working together, all the components in the Bosch Rexroth hydraulics package have successfully allowed Montenay to ensure cylinder synchronization,” said Bill Hludzinski, of Airline Hydraulics.
Once the testing was complete, Montenay asked Bosch Rexroth and Airline Hydraulics to revise the entire power unit for each boiler using four top plate pump motor groups each with Bosch Rexroth A10VSO pumps and new electric motors. Previously, six gear pumps were powered by one electric motor. That number has now been reduced to one gear pump per motor. Along with manifolds, Airline Hydraulics and Bosch Rexroth also tied into Montenay’s existing system and field piping to complete the installation. In addition, each boiler required eight model 2 FRE 6 valves and eight VT 5010 driver cards and associated electronic hardware.
Polidore was responsible for writing the front-end software program that applies the internal boiler conditions and allows the hydraulics to react to operating conditions.
“Using conditions such as temperature and pressure, the hydraulic system controls the motion of the boiler in-feed. Electricity is then ultimately generated from the steam produced by the boiler,” described Polidore. “The system is capable of varying the in-feed speed based on boiler operating parameters.”
Metz added that the pressure-compensated pump and pressure-compensated proportional valve control the hydraulic flow throughout the cylinder cycle to achieve optimum feed rates and burning quality.
Montenay successfully operated the temporary test unit during the entire changeover process because, as Polidore stated, “The plant cannot afford downtime, and the trash never stops coming.” He says Montenay manages a facility in California, where they are planning to upgrade their in-feed systems with the new hydraulics design.
Push-to-connect assembly a new option for recycling industries
Parker Hannifin’s Tube Fittings, Hose Products, and Parflex divisions have together developed a universal push-to-connect (UPTC) assembly that provides fast, efficient, and leak-free connections for compact fluid power systems in stationary and mobile equipment. The system is suited for the waste management and recycling industries (specifically in compactors and grapple arms), because it is much easier to connect in tight spaces than conventional connectors are. Furthermore, a self-aligning nipple eliminates hose twisting during assembly to maximize connection life.
Using the company’s own Seal-Lok O-ring face seal (ORFS) adapter or EO metric bite-type fittings, the UPTC system can be used with rigid inch and metric tubing, hydraulic hose, and thermoplastic hose assemblies involving tube-to-hose, tube-to-port, and hose-to-port connections. Unlike other push-to-connect couplings that require changeovers to new male and female end-fitting designs, the UPTC’s male geometry allows easy substitution on any existing Seal-Lok or EO fitting system. UPTC is especially advantageous during assembly because simply pushing the hose or tube into the adapter creates a leak-free connection. The fast connection creates immediate cost savings in assembly time — not to mention potential reductions in warranty and rework claims due to improper assembly.
UPTC consists of a base Seal-Lok or EO metric bite-type fitting, a factory assembled nut (with internal sealing and retaining elements), a dust O-ring, and a hose assembly or rigid tube. The nut is assembled to the base ORFS or metric bite-type fitting at the factory to ensure proper torque is applied. Once fully engaged, the retaining element is positively trapped between the male fitting and the nut. It cannot escape — even under vibration or extremely high pressure.
Visual and tactile install indicators on the nut and fitting signify full engagement and a complete connection. The assembly can be disconnected by using a wrench to loosen the nut, exposing a standard connector end. If the hose is damaged, the UPTC assembly can be replaced with a standard ORFS hose assembly. No special connector is required for field repair, but the option of replacing the damaged assembly with a new UPTC connection is still available. Features of the system include: