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Fig. 1.  Photo of HybridCarb®

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Fig. 2a and 2b. These charts show that the furnace temperature and carbon potential of the HybridCarb® system (2a) is comparable to that of an endothermic generator (2b), but recycling the process gas provides better carburizing efficiency and reduced cost savings.


Although many companies across the globe have managed to become much greener and in the process have begun saving, it usually takes a significant investment of both time and money and is often a very difficult transition. Change can be painful and cumbersome to production, and in heat treating, slowing production can be extremely detrimental to the bottom line.

At Ipsen, we believe that innovation drives excellence, and that excellence includes being more environmentally friendly. Heat treatment is an energy-hungry business, and in the words of Mark Twain, “If you stand still, you fall behind.” The thermal-processing industry must remain innovative in order to keep moving forward.

In today’s atmospheric gassing systems using endothermic gas or nitrogen/methanol, only 2% of the gas is actually diffused into the workpieces – 98% remains unused and is burned off and released into the atmosphere. This is not only questionable from an environmental standpoint but also represents a squandering of resources, resulting in unnecessary costs.

For atmospheric furnaces, there are many factors to consider for increasing your “green-ness.” These factors include insulation, furnace cycle optimization, high-efficiency combustion systems and gas ratios paired with concern for uniformity, repeatability and overall product quality. If you know you have a tight furnace and optimized cycles, you’ve done all you can do, right? Not so fast.

Our research and development team – Team Innovation – is busy every day dreaming the future. When they looked at atmospheric technologies, they saw a huge opportunity hiding in a dinosaur-sized carbon footprint – endothermic generators, one of the largest culprits of energy consumption in thermal processing. Endothermic generators get the job done but often lack the adjustment capabilities to efficiently handle the fluctuations of demand at the generator, furnace and ever-changing natural gas suppliers, not to mention the waste of burning off the process gas during generation.

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Fig. 3a and 3b.  These charts show hardness uniformity from the same furnace with identical sample coupon material and placement. Uniformity is much tighter with HybridCarb® (3a).

New Process-Gas-Recycling Technology

Ipsen’s new process-gas-recycling technology saves energy and resources by decreasing energy consumption and carbon footprint, resulting in immediate cost savings without the hassle of major changes in operations. HybridCarb® is a gassing system that provides precise process gas control. Instead of burning it off, the process gas is recycled, reconditioned and reused, which increases efficiency up to 90%. The HybridCarb system allows for a reduction of more than 40 tons of CO2 per year – the equivalent of planting 220 new trees a year!  

How it Works
The Ipsen HybridCarb system replaces endothermic generators and other similar gassing systems with a more efficient system that not only generates the process gas but also recycles it, resulting in significant cost savings. Using this system, process gas is recovered and used for further heat treatment. Thanks to this process-gas recycling, the carburizing efficiency is enormously increased, which is a benefit not only for the environment but also for our operating efficiency. The unique design of the HybridCarb system has a more efficient gas injection method than that of an endothermic generator, which allows for a better distribution of carbon, resulting in tighter hardness uniformity.

During HybridCarb’s recirculation phase, the process gas is not directed to the burn-off system. Instead, after transferring carbon into the load, the process gas is guided back through the system in order to be reconditioned and reused. This gassing method offers the possibility of saving 90% of the process gas during the carburization cycle, thus reducing the exhausting of carbon dioxide (CO2) caused during the process-gas burn-off.

The combination of the precise control enabled by HybridCarb along with the process-gas injection method provided by the Trunk Module (patent pending) has delivered tighter hardness uniformity in several of our early beta testing sites.

The unique HybridCarb design allows for precise process-gas control, which results in reduced heat input requirements and can lead to better performance, while the gas burners on the furnace work less – all translating to less utility cost, faster recovery after transfers and reduced maintenance cost.

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Types of Furnaces Supported

HybridCarb can be installed on batch-type furnaces (e.g., Ipsen type TQ- and RTQ- furnaces as well as similar furnaces from other manufacturers).

Furnace integrity is a factor when considering the HybridCarb application. The furnace tightness must support a low, controlled leak rate and minimal pressure with a specified flow rate in order to carry out an efficient recirculation and reconditioning of the process gas. Some furnaces may require slight modifications for maximum efficiency and control.

Installation of HybridCarb
Unlike many green improvements, HybridCarb can be installed in hours. It is intuitive, operator-friendly and its compact roll-in design fits almost anywhere, taking up much less space than your typical endothermic generator. It does not require riggers, and it connects to the existing utilities while having almost no hardwire break-ins to the original controlling system. The original alarm and safety sequences are unaffected by the installation. This green technology offers a nearly hassle-free solution, using less floor space and less piping than endothermic generators, and it reduces costs immediately upon installation.

HybridCarb interfaces with the existing gas safety panel. In addition, the installation of Ipsen’s Trunk Module into one of the sidewalls of the heating chamber is required. The Trunk Module extracts the process gas out of the heating chamber, sending it to be reconditioned, and then delivers the reconditioned gas back into the heating chamber as needed. The Trunk Module is designed to work in conjunction with the combustion blower of the heating chamber during the atmosphere circulation phase, which provides a sufficient separation between extracted (used) gas and recycled (reconditioned) gas. 

The only change in the furnace controls is the installation of a manually operated switch in order to activate the HybridCarb system. This switch can also be installed directly into the control unit and includes an electrical bypass that monitors the amount of protective gas in the furnace’s gas safety panel when the system is activated. All other security queries of the existing furnace installation remain active and will not be affected by the start-up of the HybridCarb system.

The existing furnace hardware and software – including all probes, sensors, analyzers and the furnace-gas safety panel – are still responsible for creating and executing the heat-treatment programs, temperature control and C-potential control in the heating chamber. In the same respect, all safety devices and original adjustments remain active on the furnace.  

Overall Benefits and Support
The benefits of the HybridCarb system include:

  • Quick and easy connection using Ipsen’s patent-pending Trunk Module
  • Fast recovery of atmosphere after door movement and quenching operations
  • Less heat and atmosphere loss due to closed recirculation design
  • Improved hardness uniformity
  • Less chance of IGO formulations
  • Enhanced furnace pressure regulation
  • Significantly less expensive to operate compared to the cost of running and maintaining an endothermic generator or nitrogen/methanol gassing system
  • One system per furnace prevents a single generator from bringing several furnaces to a halt
  • Shorter burner recovery time
  • Less natural gas consumption
  • Environmentally friendly and cost efficient

Ipsen’s world-class Aftermarket Support team provides support, prequalification testing and installation of HybridCarb systems.

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Fig. 5.  HybridCarb® installed on a furnace


  Making changes and improvements to be more green can be a hassle, but Ipsen’s HybridCarb gassing system is one of the few green technologies that is easy to implement, and it allows you to begin saving right away. So next time you feel yourself getting a little green around the gills about being more environmentally friendly, remember research and development teams, like our Team Innovation, are working hard every day to make green technologies more, well, company-friendly. IH

For more information: Contact Ipsen, Inc., 984 Ipsen Road, Cherry Valley, IL 61016; tel: 815-332-4941; fax: 815-332-4995; e-mail: sales@IpsenUSA.com; web: www.IpsenUSA.com. Author Jim Grann is senior technical manager and Aymeric Goldsteinas is product development manager.