Compressed Air Recovery System for PET Blow Molding Facilities
Polymer Bottle Blowing: Recover Compressed Air vs. No Air Recovery
A system that recovers spent air from the polymer bottle-blowing process and uses it for the initial blow on preforms or feeds it into the plant compressed air distribution system.
Item ID: 444
Process Loads & Appliances--Industrial Processes
The Technoplan Air Recovery System (ARS) was developed by Technoplan Engineering SA of Geneva, Switzerland, for use in PET (polyethylene terephthalate) container blow molding machines. The blow molding process requires ultra-high air pressure, in excess of 580 psig, for the bottle-blowing process. The ARS recovers compressed air after the bottle forming process at a residual pressure of 140 to 150 per square inch gauge (psig). The recovered air can be used for the preform blow or can be tied into the plant's low-pressure compressed air distribution system for use anywhere in the facility.
Blow molding plants produce many types of plastic containers, including two-liter bottles for soft drink manufacturers. A typical plant may have over a dozen blow molding machines, each capable of producing 8,000 to 20,000 bottles per hour. At a container plant in New Hampshire, two ARS systems installed on stretch-blow machines resulted in the recovery of 800 cubic feet per minute (cfm) of low-pressure air, which is comparable to the output of a 200 horsepower lubricant-free rotary screw compressor.
The cost of the equipment for a PET plant in 2010 was about $4,500 per station, with a $7,000 fixed charge for shipping and installation of all stations. For a twenty-station blow molding machine, the total installed equipment cost is about $97,000 (2010 cost estimate). About 600 ARS units have been installed worldwide at PET blow molding plants. The ARS technology is proven, cost-effective and commercially available. Connell Industries of Rahway, N.J. is the licensed U.S. distributor for this proprietary technology.
Baseline Description: Air Recycling System
Baseline Energy Use: 1280000 kWh per year per unit
A spreadsheet provided by Connell Industries yields the following: A stretch blow molding machine capable of providing 20,000 1.5L bottles/hour would provide a recovered air flow of about 871 cfm. This air would offset about 1.28 million kWh/year of energy that would otherwise be required by the compressors producing low pressure plant air. This energy offset is valued at $115,587/year given a utility energy charge of $0.09/kWh. Energy savings are thus about 1.28 million kWh per "unit." A blow molding plant may operate a dozen or more blow molding machines.
Manufacturer's Energy Savings Claims:
"Typical" Savings: 51%
Savings Range: From 50% to 60%
Note that savings are expressed here in terms of recoverable air. For this technology, the pressure of high pressure air is reduced during the stretch blow molding process. The spent air, which is typically exhausted to atmosphere, is recovered at a useful pressure and injected into the plant air system. The energy savings are not related to the energy needed to produce the high pressure air nor the low pressure plant air. A percentage of savings for these processes is not obtainable as the energy savings analysis approach does not take either energy use into consideration---i.e. process related numbers are simply not available. Savings are dependent upon the number of bottles produced per hour, the volume of the bottles, percentage of spent air that is recovered, and energy intensity of the compressors used to supply low pressure plant air.
Best Estimate of Energy Savings:
"Typical" Savings: 100%
Low and High Energy Savings: 56% to 100%
Energy Savings Reliability: 5 - Comprehensive Analysis
Energy savings are estimated at 1.28 million kWh for a stretch blow mold machine capable of producing 20,000 1.5L bottles per hour. Note that the air recovery system doesn't require energy to operate and recovers low pressure air that is typically exhausted from a stretch blow molding machine.
Energy Use of Emerging Technology:
kWh per unit per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
An annual energy savings of about 1,280,000 kWh/year is obtainable through retrofit of a spent air recovery system onto a stretch PET blow molding machine capable of producing 20,000 1.5L carbonated beverage bottles per hour. The spent air (about 871 cfm per blow mold machine retrofit) is recovered at a pressure that allows it to be introduced into the plant air system, allowing existing air compressors to be modulated or turned off.
Currently no data available.
Installed first cost per: unit
Emerging Technology Unit Cost (Equipment Only): $103000.00
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $7000.00
Baseline Technology Unit Cost (Equipment Only): $110000.00
The cost for equipment and installation of an air recovery system on a stretch PET blow molding machine with 16 cavities that allow it to produce 20,000 1.5L bottles used for carbonated beverages ranges from $79,000 to $110,000. Annual energy savings are about 1.28 million kWh/year, valued at $115,587 per year at a utility rate of $0.09/kWh. Given the high range of air recovery system equipment and installation costs ($110,000), the simple payback is expected to be slightly less than one year. Note that energy savings and equipment costs are dependent upon the number of mold cavities, production rate for bottles, and bottles size and dimensions.
Simple payback, new construction (years): -0.1
Simple payback, retrofit (years): 1.0
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
The New York State Energy Research and Development Authority (NYSERDA) published a case study for a compressed air recovery system of two of four blow molding machines at Southeastern Container. After the ARS was installed, operators noticed a definitive reduction in the plant's compressed air requirements. The baseline energy intensity dropped from 22.4 kWh/1000 bottles to 18.78 kWh/1000 bottles produced. This results in an energy savings of 1,432,000 kWh/year. Project cost was about $259,000 (NYSERDA, 2011).