Endothermic Atmosphere Generators

Endothermic gas generators are used to produce atmospheres necessary for the scale free hardening, carburizing and carbon restoration of steel as well as the cover gas for the annealing of copper and for the silver brazing and sintering processes. A typical use would be in the case hardening of steel gears where the carbon content of the steel has to be tightly controlled. Endothermic generators built by Thermal Dynamix are compact, air cooled, efficient and reliable producers of these atmospheres.

An endothermic generator is comprised of a heavily insulated, heated chamber; a nickel catalyst filled retort; a feedstock gas metering system, a chamber heating system and an output gas cooling system.

A precisely metered mixture of feedstock gas (usually natural gas, propane or butane) and air is introduced into the catalyst filled retort where it is heated to approximately 1850 F. The mixture reacts with the catalyst which prompts the conversion of the feedstock gas and air to a process gas mixture of approximately 40% nitrogen, 38% hydrogen, 20% carbon monoxide and 2% carbon dioxide and methane. The input air/gas ratio can be adjusted, within limits from lean (more air) to rich (more feedstock), to vary the carbon potential or dew point making the output atmosphere useable for a wide range of heat treating requirements. Upon completion of the reaction process the endo-gas is cooled to about 120 F and sent to its intended use. Upon occasion the gas is dried to a lower dew point and once and a while it is compressed but most often it is used as it is produced without further finishing.

Automatic Temperature Control

The temperature of the Thermal Dynamix Endothermic Generator retort chamber is controlled automatically. In our gas heated units admission of combustion air to the chamber is also closely regulated. These features, combined with the chamber being insulated with 10 inches of high performance ceramic insulation and a small retort diameter, keep heat transfer into the gas stream very fast and efficient and thermal losses very low, making the Thermal Dynamix endothermic Generator extremely efficient to operate. Heat is put into the chamber and process, not into the room.

Adjustable Feed Rates

Thermal Dynamix endo-generators are designed with adjustable feed rates (turn-down capability) based on outlet pressure. This allows matching the supply of endo-gas to the demand thereby maximizing economy of operation. Our standard configuration assumes an output gas pressure of 1.5 - 3.0 psig. However, the system can be configured for output gas pressure of up to 20 psig if desired.

Available Sizes

If your requirement is for between 250 SCFH (standard cubic feet per hour) and 6,000 SCFH we have a standard endothermic generator to meet your needs. Our standard configurations are sized (in SCFH) as follows:

250, 500, 1000, 2000, 3000, 4000, 6000

If your need is for greater capacity Thermal Dynamix™ can design and build a generator tailored specifically to your unique situation.

Economical Operation

The Thermal Dynamix™ endothermic Generator is available in either gas-fired or electrically heated configuration. This allows selection of the most economical source of energy for operation. Each generator is a package unit, completely self contained and requiring only three connections; an electrical, one for fuel gas feedstock and the process gas output connection.

Our generator is designed for natural convection cooling. There are no cooling fans or blowers to maintain and, with no power required for cooling, operating costs are absolutely minimal. Our retorts, the smallest diameter in the industry, provide faster and more efficient heat transfer into the process gas stream. This enables a lower chamber temperature resulting in more economical operation and longer retort life.

Periodic Maintenance

As with all equipment, periodic maintenance will be required. Ours happens to require less than most of our competitors. We’ve designed the Thermal Dynamix™ endo-generator to be maintenance friendly. It is well enough instrumented so that, in many cases, you can tell where the problem is. When the time comes to replace a retort or heating element you can easily get to the part. You don’t have to dismantle the whole machine. Both heating elements and retort are top mounted and each may be removed from the generator without disturbing the other.

Available Models:

2000 SCFH Gas Fired Endothermic Gas Generator

Thermal Dynamix' gas fired endothermic generators have the same production and control capabilities as our electrically heated units. The only difference is that gas is used as both the feedstock and the heat source.

Thermal Dynamix's gas fired generators may be configured for either natural gas or propane.

500 SCFH Endothermic Gas Generator

Shown in this photograph is a 500 SCFH electrically heated endothermic generator. This generator comes equipped with carbon control, automatic turn-down, system differential pressure gage, critical point thermocouple ports and touch screen programming. It's also covered by Thermal Dynamix' standard system warranty of 400 days from the date of delivery to the FOB point. And, it requires only 3' X 6' of floor space.

This is an air cooled generator. There are no pumps to maintain, no filters to plug and no issues of cooling water temperature to maintain.

EN30G-SR Endothermic Gas Generator

Thermal Dynamix offers its endothermic generators with segregated retort chambers. This enables the shut down of any one (or more)retort(s) for maintenance or repair without taking the whole system out of operation.

Shown here is a recently installed, 3000 scfh, natural gas fired generator.

Generator Manuals:

Initial Start-up Procedure, EN30G-SR.pdf
Installation Procedure EN30G-SR.pdf
Operating Instructions EN30G-SR.pdf

1500 SCFH Electrically Heated Endothermic Gas Generator

This Thermal Dynamix endothermic generator comes equipped with touch screen automatic control for the regulation of chamber temperature, process gas outlet pressure and carbon potential. The output flow, is matched to the process needs minimizing the discharge of expensive process gas up the stack and maximizing operational efficiency. The system provides a turn-down capability of somewhat better than 3.5:1.

Chamber temperature trends and process bar charts continuously show temp, set points and % carbon. Setup is straight forward and easy to follow on screen.

Each thermal Dynamix generator is a package unit, completely self contained and requiring only three connections; an electrical, one for fuel gas feedstock and the process gas output connection (A vent hood or outside vent connection is also required). The TDI generator is designed for natural convection cooling. With no cooling fans or blowers to maintain cooling costs are minimal. 

Generator Top

As with all Thermal Dynamix electrically heated atmosphere generators, either the heating element(s) or the retort can each be removed, if necessary, without disturbing the other.

Gas Train

The gas train is complete and self contained. Necessary gauges are direct mounted and positioned for easy observation.


All generator operational controls are face mounted on the control panel enclosure. Operation controls are simple and straight forward. Temperature and carbon control is by
a simple touch-screen controller.

Retort Base

The generator is equipped with a rechargeable retort. The retort is designed with a flanged top and removable base enabling the catalyst to be removed with having to remove the retort from the chamber.

Admittedly, changing catalyst is a messy job but at least with the TDI endo generator the catalyst can be removed from the retort without having to pull the retort out of the machine. The process involves simply removing the inlet vestibule of the retort (8 bolts) and allowing the catalyst to fall onto a tray or drop cloth and then removing the top (exit) end of the retort
(4 bolts) and pouring new catalyst into the retort.