Process gas preparation apparatus for an industrial furnace system and an industrial furnace system for gas carburizing and hardening of metal workpieces utilizing same

Abstract

A process gas preparation device for an industrial furnace system is disclosed. The gas preparation device includes a preparation reactor having a catalyst. A gas feed line and a gas return line are connected between the industrial furnace and the preparation reactor to form a closed loop. A compressor is situated upstream from the preparation reactor in the feed line. The preparation reactor is also connected with supply lines for hydrocarbon gas and air to be supplied to the preparation reactor. The process gas preparation device also includes a control device with which process gas preparation and return can be regulated and controlled. The gas feed line also has a shut-off valve. The control device can check the functional state of the catalyst by measuring the pressure differential across the catalyst and can initiate a burn-out process therein to clear clogging of the catalyst.

Claims

1. A process gas preparation device for an industrial heat treating furnace system, said gas preparation device comprising: a preparation reactor that contains a catalyst; a gas feed line connected for conducting spent process gas from a treatment chamber of the industrial furnace system to the preparation reactor; a gas return line for conducting process gas from the preparation reactor back to the treatment chamber; a compressor connected in the gas feed line upstream from the preparation reactor; a hydrocarbon gas supply line and an air supply line connected to the preparation reactor; a shut-off valve connected in the gas feed line; a first mass flow controller connected to the hydrocarbon gas supply line; a second mass flow controller connected to the air supply line; a pressure difference measurement device; and a control device connected to the preparation reactor, to the compressor, to the shut-off valve, to the first mass flow controller, to the the second mass flow controller, and to the pressure difference measurement device for controlling the operation of the gas preparation reactor; wherein the control device is programmed to monitor the pressure differential across the catalyst via the pressure difference measurement device and to initiate a burn-out process in the catalyst to remove clogging matter from the catalyst when the pressure differential reaches a preselected set point that indicates a clogged operational condition of the catalyst.

2. The process gas preparation device according to claim 1 comprising a cooler connected in the gas feed line upstream from the compressor.

3. The process gas preparation device according to claim 1 wherein the control device is programmed to control the supply of hydrocarbon gas and the supply of air to the preparation reactor.

4. The process gas preparation device according to claim 3 wherein the control device is connected to the compressor and to the shut-off valve whereby the operation of the compressor and the operation of the shut-off valve can be controlled by the control device.

5. The process gas preparation device according to claim 3 wherein the preparation reactor, the compressor, the first and second mass flow controllers, the shut-off valve, and the control device are contained in a shared housing that is separate from the industrial heat treating furnace.

6. An industrial furnace system for gas carburizing and hardening of metal workpieces comprising: an industrial heat treating furnace having a treatment chamber; and a process gas preparation device according to claim 1, wherein the preparation reactor is connected with the treatment chamber of the industrial heat treating furnace by a closed loop comprising the gas feed line and gas return line.

7. The industrial furnace system according to claim 6 comprising a burn-off location that is connected to the treatment chamber by an exhaust gas line and the exhaust gas line comprises a shut-off valve by which the exhaust gas line can be shut off.

8. The industrial furnace system according to claim 6 comprising a process gas lance connected to the gas feed line and to the gas return line for guiding the process gas into and out of the treatment chamber.

9. The industrial furnace system according to claim 6 wherein the process gas preparation reactor is at least partially integrated into a housing of the industrial furnace.

10. The industrial furnace system according to claim 6 wherein the process gas preparation reactor is contained in a separate housing provided outside of the industrial heat treating furnace.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Advantageous embodiments of the invention described below are depicted in the drawings wherein:

(2) FIG. 1 is a schematic view of an industrial furnace system with a process gas preparation device corresponding to a first embodiment of the invention; and

(3) FIG. 2 is a schematic illustration of an industrial furnace system with a process gas preparation device according to the invention corresponding to a second embodiment of the invention.

DETAILED DESCRIPTION

(4) Visible on FIG. 1 is a schematic view of an industrial furnace system 1 corresponding to a first embodiment of the invention, wherein this industrial furnace system 1 includes an industrial heat treating furnace 2, in which is located a treatment chamber 3 for the heat treatment of metal workpieces. The heat treatment is set up in such a way as to expose the workpieces introduced into the treatment chamber 3 to gas carburization and hardening heat treatments which are known in principle to the skilled person. In carrying out the carburizing heat treatment the treatment chamber 3 is continuously supplied with a process gas under a positive (i.e., superatmospheric) pressure. The process gas is composed of a carrier gas typically comprising carbon monoxide and hydrogen and an enrichment gas, typically a hydrocarbon gas.

(5) In the apparatus according to the present invention, the treatment chamber 3 is not rinsed with the process gas, i.e., the process gas supplied to the treatment chamber 3 is not subsequently flared off at a burn-off location 4. Rather the process gas spent during gas carburization is recycled and regenerated for further use. To this end, the industrial furnace system 1 is equipped with a process gas preparation device 5, which has a preparation reactor 6. The preparation reactor 6 includes an insulated housing 6a, heating elements 6b, and a heating chamber 6c.

(6) Located inside of the preparation reactor 6 is a catalyst 7 in which the process gas is prepared via corresponding enrichment with carbon. The catalyst 7 includes a gas-tight container 7a which is constructed and arranged to hold the catalytic material 7b. Suitable catalytic materials are described in U.S. Pat. No. 8,333,852. The spent process gas is conducted out of the treatment chamber 3 by means of a gas feed line 8 to the preparation reactor 6, and thus, to the catalyst 7. The gas feed line 8 includes a compressor 9 with a cooler 10 both of which are located upstream from the preparation reactor 6. The cooler 10 is preferably designed as a heat exchanger with a blower by which ambient air of the industrial furnace 2 can be forced over the heat exchanger to increase the heat transfer.

(7) The process gas prepared in the catalyst 7 is conducted back to the treatment chamber 3 via a gas return line 11. The gas feed line 8 and the gas return line 11 are connected to the treatment chamber 3 by a process gas lance 12 that traverses an opening or port through the walls of the heat treating furnace and the treatment chamber. In addition, gas supply lines 13 and 14 are also connected to the preparation reactor 6, whereby the preparation reactor 6 can be supplied with hydrocarbon gas via the supply line 13 and/or with air via the supply line 14. The supply lines 13 and 14 include respective mass flow controllers 15 and 16, with which the quantity of gas flowing through the respective supply line 13 or 14 can be precisely regulated or adjusted.

(8) The regeneration or preparation of process gas and its return to the treatment chamber 3 is regulated and controlled by a control device 17 of the process gas preparation device 5. The control device 17 is preferably configured as an electronic, computer-assisted and/or programmable controller. The control device 17 is connected with the catalyst 7, with the compressor 9 and cooler 10 (if present), as well as with the mass flow controllers 15 and 16. The control device 17 is further connected to two shut-off valves 18 and 19, of which the shut-off valve 18 is connected in the gas feed line 8 and the shut-off valve 19 is connected in an exhaust line that extends from the treatment chamber 3 to a burn-off location 4. Further, the control device 17 is connected with a pressure sensor 20 which is mounted in the treatment chamber 3 to continuously monitor the pressure in the treatment chamber. The control device 17 is configured to receive other parameters of the treatment chamber 3, including in particular the current temperature in the treatment chamber 3, as well as a carbon content of the process gas present therein.

(9) The return of the process gas via the gas return line 11 is regulated by the control device 17 as a function of the pressure in the treatment chamber 3. If the control device detects that the pressure is too low, the control device 17 acts to increase the gas pressure by signaling the mass flow controller 15 and/or the mass flow controller 16 to add hydrocarbon gas and air via the supply lines 13 and 14, respectively. By contrast, if the control device 17 detects that pressure is too high, then the shut-off valve 19 is opened, and the pressure is reduced by exhausting process gas through the exhaust line causing it to be burned off at the burn-off location 4.

(10) In addition, the control device 17 can be programmed to close the shut-off valve 18 and thereby block the gas feed line 8 in a targeted manner so that no spent process gas can flow into the preparation reactor 6 at selected times. Under such condition, for example, the treatment chamber 3 can be pressurized solely by process gas newly generated in the preparation reactor 6 by the reaction of hydrocarbon gas and air as correspondingly supplied via the respective supply lines 13 and 14.

(11) The control device 17 further continuously monitors the functional state of the catalyst 7 by detecting a differential pressure across the catalyst 7. If the pressure differential across the catalyst 7 is too high relative to a set point, then the control device 17 initiates a burn-out cycle, so that soot and other debris in the catalyst that are clogging the catalyst can be burned out and removed to clean the catalyst.

(12) In the embodiment shown in FIG. 1, the process gas preparation device 5 is completely integrated into (i.e., housed in) the industrial furnace. This is preferably realized by structurally locating the preparation reactor 6 underneath the treatment chamber 3. The mass flow controllers 15 and 16 are installed in a gas mixer tap of the industrial furnace 2 and the control device 17 is located in a control cabinet of the industrial furnace.

(13) FIG. 2 depicts a second embodiment of an industrial furnace system 21, which corresponds to the embodiment of FIG. 1 with respect to the essential features of the gas preparation device. The difference of the embodiment of FIG. 2 is that the process gas preparation device 22 is not integrated into (i.e., not housed in) the industrial furnace 23. Rather it is connected externally to the industrial furnace as a separate, preferably self-contained, unit. To this end, the components of the process gas preparation device 22, already described for the embodiment of FIG. 1, as gas preparation device 5, are installed in a housing 24 which is separate from the housing of the industrial furnace 23. Otherwise, the embodiment according to FIG. 2 corresponds to the embodiment according to FIG. 1.

(14) Process gas preparation can be optimally configured with the embodiments according to the invention of a process gas preparation device along with an industrial furnace system that includes such a gas preparation device.

REFERENCE LIST

(15) 1 Industrial furnace system 2 Industrial furnace 3 Treatment chamber 4 Burn-off location 5 Process gas preparation device 6 Preparation reactor 6a Thermally insulated housing 6b Heating elements 6c Reactor chamber 7 Catalyst 7a Catalyst container 7b Catalytic material 8 Feed line 9 Compressor 10 Cooler 11 Return line 12 Process gas lance 13 Hydrocarbon gas supply line 14 Air supply line 15 Mass flow controller (hydrocarbon gas) 16 Mass flow controller (air) 17 Control device 18 Gas feed line shut-off valve 19 Exhaust line shut-off valve 20 Pressure sensor 21 Industrial furnace system 22 Process gas preparation device 23 Industrial furnace 24 Housing 25 Difference pressure measurement device