CA2062708C - Method and apparatus for regenerating gas used in carbon dioxide laser generator - Google Patents

Abstract

An improved method and apparatus for regeneration and reuse of He-N2-CO2 mixed gas for carbon dioxide gas laser generator. The mixed gas after use is contacted with a precious metal catalyst (for example, Pt-Al2O3) at a temperature of 200 - 300 °C to react CO and O2 so as to form CO2. Poisoning of the catalyst by NO x is suppressed at this relatively high temperature of reaction.
Deterioration of the catalyst can be prevented to some extent by pretreating the catalyst prior to use, and the activity of the catalyst, even if decreased, may be recovered by reactivation.

Description

2062~

MET~OD AND APPARArUS FOR ~ P~ING GAS USED IN CARBON
DIOXIDE LABER GEw~RATOR

BA~K~Ku~Nv OF THE lNv~ ON
The present invention concerns a method of regenerating mixed gas used in a cArbo~ dioxide laser generator with the aid of a catalyst as well as an apparatus 10 for working the method. The invention further concerns a method of reactivating the catalyst by Lecov~L-ing it from poisoning by NOX and a method of pretreatment the catalst for r~ ci n~ the poiconi n~ .
A~ the laser gas for c~rb~n dioxide laser generator of 15 high output and high pulse there has been u~ed a mixed gas consisting of He, N2 and CO2 at a mixing ratio of 8:1:1 ~volume). Due to diacharging a portion of C02 is decrn~cee~, and if the decompsition products remain in the gas, output of the laser generator decreaRes and arcing 20 ~ h~rge will occur.
Under constant ~upply of fresh gas the high output can be maintained. ~'.J~l, He-gas which shares a major part of the mixed gas for laser is ~yrencive~ and supply of the fre~h mixed gas as dem~nded make~ the runnin~ cost~ very high.
25 Thus, efforts have been made to ~ 'ine CO and C02 formed in the carbon ~i~Y;~ laser ~eneL~Lo~ to form C02 and reuse 20~2708 the thus regenerated gas. It i8 known that precious metal cataly~t are useful for practicing the reaction.
The in~entors intended to provide an industrially practicable method of regenerating the mixed gas used in the carbon dioxide la~er generator, and estab1;~he~ the method which enables reuse of the mixed gas cont~in;ng CO and C02 by recombining them, and disclose~ it (J~p~n~se Patent Di~closure Hei 3-84980).
The method compri~e~ preheating the mixed gas used in 10 the carbon dioxide ~aser generator and contacting it with a catalyst to react CO and ~2 in the mixed gas, while u~ ng the reactio~ heat for preheating the mixed gas to be treated, and then, cooling the reacted gas to the temperature 3uitab1e for reu~e in the laser oscillation and, after removing dust 15 therefrom, recycling it to the laser genera-or. The reaction conditions preferable for this regeneration are:
reaction temperature 80 - 200 ~C, ~pace velocity of the mixed ga8 in the catalytic reactor 4,000 - 14,000 /Hr. r- i n~
under pressure makes it pos~ible to use a lower reaction 20 te~pe~ture and reduce the size of the apparatus, and th~ ~fole, i8 ~ '. Practically, if practiced under a pre~ure of 5 kg/cm2 G or higher, efficient reac~ion can be made even at a preheating temeprature as low as near the normal temperature ( about 40~C~, and the loads of the 25 preheater and the cooler may be much re~l~ced.
The method proved to be succe~s~ul to 30me extent.
~c.~e~ in aase where the operation continued for a long period, particularly, operated under the conditions where the laser output is high, the activity of the catalyst decreases and the regeneration of the gas becomes insufficient.

SUMMARY OF THE INVENTION
The object of the present invention is to provide an industrial method and apparatus for regenerating the mixed gas used in a carbon dioxide laser generator so that the gas may be used repeatedly, and so that the catalyst remains active for an extended period of time.

In one aspect of the invention there is provided a method of regenerating He-N2-CO2 mixed gas for reuse in a carbon dioxide gas laser generator comprising contacting the mixed gas used in the laser generator with a precious metal catalyst at a temperature exceeding 200~C and up to 15 350~C to react CO and ~2 with NOX in the used gas; utilizing the reaction heat for preheating the unreacted mixed gas; cooling the reacted mixed gas to a temperature usable in the laser oscillation; removing dust from the mixed gas; and recycling the mixed gas to the laser generator.

An apparatus according to the invention comprises a gas preheater for preheating the mixed gas used in the laser generator; a reactor which has a heating means and is packed with a precious metal catalyst for reacting CO
and ~2 with NOX in the preheated mixed gas; a gas cooler for cooling the gas ' CA 02062708 1998-04-29 after the reaction; a filter for removing dust from the gas after cooling; a means for recycling the regenerated gas to the laser apparatus; and a means for supplying a He-CO-02 mixed gas to the reactor packed with the catalyst for reactivating the catalyst.

BRIEF EXPLANATION OF THE DRAWINGS
Fig.l is a flow chart illustrating the structure of the apparatus for regenerating the gas for laser generator;
Fig.2 is a flow chart illustrating the experimental 10 apparatus with which the present invention was established;
Fig.3 concerns experimental data for the present method, or the graph showing that the Pt-A1203 catalyst used in the laser gas regenerating apparatus recovers its activity at a high temperature after being poisoned by NO;
Fig.4 also concerns experimental data showing that the gas regeneration carried out subsequent to the experiments of Fig.5 also concerns experimental date showing the results of regeneration of a gas having a composition simulating to the composition after u~e of the la~er gas according to the present invention;
Fig.6 is practical data of the working example according to the preqent method of mixed ga~ regeneration showing the chAn~es of C0-reactivity and N0-reactivity ~pq~jng on the temperature in case of Le~ene.a~ing the laser gas cont~; n; ng NO;
Fig~7 is pracitcal data of the wc ' ing example according to the present method showing the chAn~es with the passage of time of C0-reactivity and N0-reactivity in case where the laser gas cont~;nlng N0 was regenerated by use of a reactivated c~talyst;
Fig.8 is comparative data of the working example using the cataly~t which is pretre~ted according to the present invention and thQ catalyst which is not pretreated by showing the ~h~n~6 with the pA~~~gq of time of C0-rea~tivity;
Fig.9 is data o~ a working example in which the la~er 20 gas regeneration according to the present invention i~
combined with laser o~cillation showing the ~h~nges in ~2-c~c~Lration in the laser gas by comparing the ca~es where the Ley~ La~Or i8 used or not used;
Fig.lO is data of the working example, to which the 25 data of Fig.9 i~ related, Yhowing the Gh~ngss with the passage of time in the laser output by comparing the cases where the L~ne-a~or is used or not used.

20627~8 DET~TT~n D~C~ ON OF THE lhv~luN
The method of r~geneiating the gas for carbon dioxide laser ge~.eL~to~ is a method of r~gen~ldling He-N2-C02 mixed gas used in carbon dioxide gas laser gene~aLo~ for reuse, which method coIprises contacting CO, ~2 and NOX in the ~ixed ga6 used in the laser g~e~dLor with a precious metal catalyst at a tempe~d~ure P~n~;nq 200~C and up to 350~C;
while ut;l;7;n~ the heat of reaction y~elaLed by the catalytic reaction for prQh~tjn~ the un~eac~ed mixed gas;
10 cool m g the m1xed gas after the reaction to a teD~ld~f~ at which the gas may be used for gen~ration of the laser,o removing du~t in the gas and recycl m g the gas to the laser g~n~ r. Suitable space velo~ity for pasBing the mixed gas in the catalyst bed is Ln the range of 4,000 - 15,000 15 /~r.
The ~ethod of rea~tivating the catalyst according to the present invention is to rQactivate the catalyst with lowered activity due to ri~ning by NOX C~ntAin~e~ in the mixed ga8 after laser di3charge m practice of the above 2~ described method of ~g~n~ ing the mi~ed gas, and co~p~is~s passins a ~ge,rF,~tin~ gas consisting of 0.2 - 0.8 % of CO, 0.1 - 0.4 ~ Of ~2 and the balance of He through the catalyst layer at a temp~alu~ of 400 - ~00 oc.
The ~ethod of ~eLl~rt;ng the cataly~t according to 25 the preoent i~ n ccmpri~es, prios to pr~cticing the above d~QC- ;h~ mothod o~ ting mixed gas, pas~ing a 2~62708 .
He-N2-CO2 mixed gMs cont~;n;ng CO of 1,000 - 3,000 ppm or He gas cont~n~nq CO of 1,000 - 3,000 ppm in the catal~yt layer at a temp~rature of 60 - 150 ~C . Suitable space veloclty i~ 100 - 500 /Hr.
~he apparatu~ ~or regenerAting the gae for carbon dioxide gas laser according to the pre~ent invention, with which the above described method of L~gen~Ling the mixed ~as, the method o~ reactivating the catalyst and the method of ~ Laa~ing the catalyst are carried out, comprises, as lO illustrated in Fig.1, a gas~gas heat PY~hAng~r 2 for preheatlng the mixed gas used in the cArhe~ ~iQyi~e gas la~er yeneL~G~ 7; a ga~ heater 3; a reac~o 4 having a heatiny mean~, in which a catalyst for reacting CO and ~2 with NOX in the mixed gas i8 p~ck~; a ga~ cooler 5 for cooling the mixed 15 ga~ after the reaction; a filter 6 for removing dust from the mixed ga~ after cool;n~; all the devices being connected in the above mentioned order; a means for recycling the ~ ¢nCL~ gas to the laser ~~ne~d~or such as a blower; and a means for ~upplying a He-CO-D2 mixed gas 9 for reactivating 20 the catalyst. In ~ig.l, n~eral reference 10 indicates a gas analy~er.
The rePc~G~ to be employed in the present invention i8, pl~La~bly, a type of self heat ~Y~h~n~;ng or a reactor in which the ga~ before the reaction is heated by the gas 2~ after the reaction. The app~ratus must be durable to the temp~a~ of 400 - 500 ~C h~ e the reactivation of the c~taly~t i5 carried out at this level of temperature.

- .
- . - .

"; ~ ~
~ .. .. .. .

Pre~erable cataly~ts to be used in this in~ention are tho e of precious metals such as Pt, Rh and Pd supported on a carrier such as alumina or silica, which are known a~ the CO-oxidation catalyst. Particularly, Pt-A1203 catalyst is the most u~eful. The content of the precious metal in the catalyst i8 usually in the range of 0.3 - 5 %.
The gas cooler and the filter may be chosen from the known apparatus on the basis of the reaction conditions and the quantity of the gas to be treated. The filter preferbly 10 has the perf~- ~n~e of removing 99.9 % or more of the dust of particle ~izes of 0.1 micrometer or more.
In the practical use of the gas regeneration apparatus of the pre~ent invention, it is of course possible to recyle all of the mixed gas. In case where it is preferable to 15 reduce the load of the regeneration apparatus 80 as to avoid accumulation of CO and ~2 gas in the ~cy~ne~a~ed gas, i~ is also possible to ch~o~e as an alternative, as shown in Fig.1, to r~leA~e a portiong of the used gas and to rerl~n;~h fresh mlxed ga~ of the equivalent quantity from a suitable source 2~ such as a bomb 8. It is convenient to supply the gases for reactivation and pretreatment of the catalyst through the la~er generator.
In the He-N2-C02 mixad gas for the cArho~ dioxide gas laser yeneLator CO and ~2 occur due to the discharge therein 25 a~ the result of the following reactions:
C~2 + e ~ CO + O + e (1) O + O = ~2 (2) It h_s been practiced to ~es~..aLate CO2 by c~a~ g the reaction bc~ n the CO and the ~2 with tho aid of a cataly~t~
CO I 0-5 ~2 ' CO2 ~3) The inventors investigated the reason of relatively rapid sl~-'~ of the activity of the catalyst for this reaction and found that NO and NO2 ~hereinafter represented by HNOx") occur due to the ~1~chArge in accordance with the folcwing reaction~: -N2 + e = N I N I e (4) N + O = NO (5) NO + O = NO2 (6) and that the NOX i~ strongly A~ at the active points to pnj~o~ the catalyst. Quantity of NOX y~e~ed in the gas 15 i8 very slight under the conditions where the la~er output is low, _nd the NOX doe~ not cause a serious problem. The quantity, }~ -~1, increases i~ the la~er output is ;-hiY1~nO~. PO;~Qn1~ by NOX iB significant at a lower reaction tem~6 ~tu~ (80 - 200 oc) chssen in the previous 2 0 in:vent i Qn .
In the p~e-e~t invention, the catalyst activity is maintained for much longer period by ch~o~in~ a higher tem~e~LuLa (200 - 300 ~C~.
When the activity d~cLaaD~d si~nifi~antly, the NOX
25 ad~orbed by th~ cataly~t i~ decompo~ed in accordance with the following reaction-:
NO ~ CO = 0.5 N2 + C~2 (7) .
: ;, . ~ ~ . .:
,. ,. , ~ - ,. ... , ~
- . . . I

.. . . . . .

N02 = 0.5 N2 + ~2 (8) so that the cataly~t may be recovered from poisoning and reactivated. Thus, it i8 possibLe to repeat the p.ocedu~e~
of ~agene aLing the mixed gas for cAr~on ~i~Y;~e gas laer go~LaLo~.
The techno1ogy of L~ene aLing the mixed gas according to the present invention ensures enjoying the merit~ of the previously pL~p~sad invention that enables repeated use of the used gas for la~er in the carbon ~;oYi~ gas laser 10 ~er.e~ator and reduction of the running costs for the laser operation.for a long period The m~thod of pretreating the catalyst according to the present invention AnhA~e~ the above merits by reducing cataly~t poi~oning by NOx~ The method of reactivating the 15 catalyst makes it r~s;hle to reactivate the cataly3t of ~ l activity due to the po;~oning and to use it - repeatedly. The investment for the apparatus for LC~ ating the laser gas is low and the space necess~ry for the npparatus i5 also umall.
EXAMPLES
;E~n~Al ~~mple An experimental apparatus as illustrated in Fig.2 was composed and ~3~d to determine the acti~ity, extent of 25 p~;~o~ing and effect of reactivation. In the figure numeral ~efe ~I.ce 11 ;n~ic~tes a gas mixer; 12, a gas heater; 13, a reactor; 14, a pressure maintAin;ng valve; 15, a gae , .

~ :, .. : . . -: :, .. .

analyser; and 16, a gas meter~ The cataly~t u~ed was of the following specification:
Pt-Al203 ~supported Pt: 4.3 g/liter) Particles (particle sizes 3 + 0.3 mm) Bulk density 0.36 kg/liter 6 Pore volume ~BET) 1.4 cm3/g There were surplie~ N2 gas and two kind~ of mixed gases (N2 ~ NO/N02 and He + C0 + ~2) from bombs to the mixer 11 at a determined rates, and thus obtained mixed gases were, 10 after being heated in a heater 12 to a determined temperature, intro~nce~ into the re~c~o~ 13. The gases from the reactor pa~s the pressure maint~;ning valve 14 and were ~ubjected to volume measurement, and then, treated by an exhau~t system for release~ Analysis of the gases were 15 carried out with the apparatus 15 e~irpe~ at ~he downstream of the pressure maintAin~ng valve.
Fir~tly, N2 gas contAin;ng N0 o~ 100 ppm was ~ i at a rate of SV = 5000 /Hr, and the tempe~a~ure was ch~nged from 20~C to 50~C and 150~C, to observe chAng~ in adsorption ZO . At 20~C and 50~C, a breakthrough, i.e~, detection of N0 at the outlet of the re~c~o~ was appreciated 5 minute~ after the introduction of the gas. At 150~C, h~ eL, it was detenmined that it takes about 10 minutes until the breakthrough be~ins. Thus, it was found that the time until 25 the breakthrough i8 lonqer at a higher tempela~ure.
Then, after having the active point~ poisoned with N0, He-C0-02 (C0/02 = 2/1) mixed ga~ was pa~sed to deter~i n9 ln .
-whether the activity ~ec~v6~. When an N2 ga~ contyalintn~ NOof 58.1 ppm wa~ passed at 88~C for 140 minutes, the catalytic activity for the reaction of CO + ~2 became extre~ely low.
~hen, paQ~ing pure N2 gas at 100~C for 7 minute~ resulted in a temporary ~ec~vaLy of the activity, but the activity decreased in a short period, and the Lacove~y of the activity was 50 % or so.
In order to investigate the influence of the reaction tempeL~re, experiments under the conditions ~hown in Fig.3 lO were c_rried out. At first, the catalyst pretreated with He-CO gas wa~ subjected to NO-poiQon;n~ ~with the above mentioned N2 gas contAin;n~ 58.1 ppm NO) to the saturation, and then He-CO-O2 mixed gas ~CO/O2 = 2~1) was pA~seA at 80~C.
In the fir~t 2 hour~ activity was appreciated, but it 15 d~croaJed rapidly. After ~ hours N2 gas was passed at 330~C
for 6 hour~, and no ~cuv~ of the acitvity waq appreciated.
The ro~ction tempe ~uLe was elevated to 200~C, and He- CO-02 mi~ed gas ~CO: 0.60 ~, ~2: 0.30 ~, the hAl~nte:He) - -was pAs~ed at a rate of SY = 5000 /Hr. The activity 20 l~cu._L~d to the initial level. In the graph of Fig.3, a temporary decrease of the activity i~ t~c~l~ed after 19 hours. This might have ~een cfl~e~ by rerun of the exp~rim~mt~ after stan~ing without flowing gas fo~ a whole day, and the reason i8 cQn~i~tred to be that the adsorbed CO
25 and ~2 moved around on the c~atalyst surface to inactivate the active point~ ~h~.~of.

.. ..
: , . , :

-- , ~ , :,. : - .

. .
. . ~ .

2~62~08 The catalyst was subjected to NO-poinsoning under the same conditions as mentioned above, and then, to reactivation with the mixed gas of the same composition a~ above and under the conditioDs of temperature and flow rate also mentioned above. The results are shown in Fig.4. From the graph of the figure it is understood that the catalyst, even after lap~e o$ 30 hour~, retains sufficient activity to promote the reaction of CO + ~2-The gases of three different composition~ similar to 10 those after u~e in the carbon ~io~ gas laser generatorwsre sllrpli~ , and the content~ of CO and NO at the outlet of the r~actor were determined. The results are as in Fig.5. The catalyst activity remained high without remarkable ch~ng~. The reason why the CO-content is 15 relatively high i~ aonsidered to be the preferential reactions of:
~0 + 0.5 ~2 = N~2 N~2 + 2 Co - 2 C02 + 0~5 N2 to the reaction~ of:
NO + CO = 0.5 N~ + C02 CO + 0.5 ~2 ~ C~2 On the basis of the fact that the content of NO is ~u~essed low, it is ~ec~ed that, even though NOx occurs in the laser gas after use, the catalyst will not be significantly 25 d~teriorated and can be used for a long time.
Wor~in~ le 1 In the apparatus of the structure shown in Fig.l, a cylindrical r~aator was u3ed and a mesh was placed in the bottom thereof, on which 12 liters of 0.5% Pt-Al2O3 catalyst was packed with pack;n~ of Raschig rings thereon.
S Temperature sensors were put in the cataly~t layer for m~a~uring the ch~nges of the tem~eraLuL~s at the upper part ~gas inlet side), intermediate part, and the lower part ~gas outlet side) of the catalyst layer ~o a~ to det~ i n~ how the activities change at the respective parts of the catalyst lO layer.
The reac~ol was combined with a carbon dioxide gas laser generator, to which a He-N2-CO2 mixed gas was supplied through a mass-flow control valve. A portion of the gas was ~ampled and transferred to the above regeneration apparatus 15 with a blower. The transferred gas was, after being eubjected to heat recovery at the heat ~Y~hAn9er~ heated at the heater and int~ud~\ce~ into the reactor at a temperature of 250 - 300 ~C for recambination reaction of the side products at the catalyst layer. The gas, by way of the heat 20 aY~hAn~er~ moves to the cooler and is cooled to a t - a~re lower than that of the laser chamber. The coole~ ga~ i~
recycled to the laser generator after beinq filtered for removal of the dust.therein.
Qantitative analysis of NOX wa~ done at the inlet and 25 the outlet of the reactor under keeping the temperature of the catalyst layer constant at 300~C with varying quantities of the recycled gas, and the gas conversion and O2-re~ctivity were calculated. The results are ~hown in Table 1.
~ hen, He-N2-C02 mixed ga~ contA; n; ng C02 of O . 6 % ~ ~2 of 0.3 % and NO of 26 ppm or 162 ppm were su~rl;sd to the reactor at variou~ temperatures. The space velocity was 500 ~Hr. The xeactivity of CO and the reactivity of NO showed the ~h~n~8 ~p9n~;ng on the temp~Latule as illu~trated in Fig.6. From the data it is evident that the reactivities incr~a~e drastically at the tempeL L~e above 200~C. This 10 effect saturatQs at thQ temperature around 240 - 250 ~C, and therefore, a temp~rature higher than this limit provides no further merit. The upper limit of the reaction temperature, 350~C, was ~9ci~ from the practical vi~w points such as easines~ in control.

Quantity Co~c~enLrations C~ n~rations Conv~l~ions 02 of Recy- of Ga~e~ at o~ Ga~e~ at of Ga~es RQacti-cled Gas na~-~-ol Inlet R~C~G~ Outlet vity (N liter ~ppm) (ppm) (%) (~) /min.) NO N02 NO~NO N02 NOx NO N~2 NOx ____________ ___ ___ ____ ____ ____ ______ 400 2971100 9 28 3~ 6g.0 60.6 63.0 g9.~
400 316192 8 25 33 74.2 59.0 64.1 99.4 500 4093133 10 31 41 75.0 66.7 69.2 98.8 600 501060 5 nil 5 90.0 100 91.7 99.8 700 315485 5 13 18 83.8 75.9 78.8- 99.2 1000 1407021020 nil 20 85.7 100 90.5 99.8 . . ' , 20627~8 Work; n~ ~YAm~le ~
After having the catalyst poisoned by contacting N2-gas contA;ning NO of S8.1 ppm at 88~C as described in the above working example, a ~e-CO-O2 gas cont~; n; ng CO of 0.6 %
and ~2 Of 0.30 % was passed through the catalyst layer under the conditions of t~mperature 400~C, and space velocity of 2,000 /Hr for 3 hours to reactivate the catalyst.
~ hen, a He-CO-O2 mixed qas cont~inlng NO of 66.4 ppm in addition to CO of 0.6 ~ and ~2 of 0.3 % (simulated to the 10 state of the laser gas aftex use) was passed through the apparatus at 270~C and space velocity of S,000 /~r for ~g~neL~-ion of the ~as.
The r~activity of CO and the reactivity of NO ~re as shown in Pig.7. It was ascertained that, in view of the lS fact that th~ activities are kept at the lev~l as high as 100 % or near, the above reactivation of the catalyst was effective.
Workin~ Exam~le 3 A new cataly~t was p~9~9~ in the reactor, to which a 20 He-gas contAin;n~ CO of 1,000 ppm was passed at 150~C and space velocity of 300 /Hr for 1 hour to pretreat the catalyst.
Then, a He-CO-O2 mixed ga~ cont~; n i ng NO of 6 3 . 6 ppm in addition to CO of 0.6 % and ~2 of 0.3 ~ (also, simulated 25 to the ~tate after use of the laser ga~) wa3 passed through the apparatus at 240 - 250 ~C for reactivation of the reactor. The reactivity of CO was maintained at 100 ~ for a long period of time as seon in Fig.8. The activity of the catalyst which was not subjected to the above reactivation treatment i8 also shown in Fig.8. Fig.8 show~ decrease of the acitvity after 3 - 4 hours of running.
Working ~Y~mDlo 4 O~c;~ation of the carh~n dioxide ga~ la~er was carried out under the following conditions;
Mixêd gas composition C02/N2/He = 1/1/5 Ropeating rate 100 pps Laser output 620 W
Chamber volume 1000 liters Volume in the ~;~ch~rging zone 1 liter Pres~ure in the la~er gas 1 atm.
The ,~ ~Gl u~d in Example 1 was used as the 15 l~a ~a~G~ of the gas, with which the mixed ga~ was resen~.a~ under the conditions below:
Te~,a~ure of ~ ne-ation 200~C
P,~a~u,. in L~3f~--ator 1 atm.
Ratê in gas recycling 1 m3/min.
Space velocity 5,000 ~Hr The O2-~c~nc~rations in the Ch '- were prio~icAlly measured. The re~ults are shown in Fig.9 in comparison with the case of uSlng no gas Le~a.~e~aLo~. As seen in Fig.9, if the ~ rator is not used, arcing occurs only 5 minutes after initiation of the laser s~cilation, and after 20 minute~ ~2 co~c~ ra*ion r~t~-' to 20,000 ppm, at which level no further operation can be continued. On the other ,, ~ ' , , '' ' ,' ' ,: ' ' ~
, ~ ' ' ' ' ': ' ' ' ' ' hand, in case of using the regenerator, ~2 concentraion does not ~-c~ 2,000 ppm and operation of the laser generator for a long period i3 poBs~hle.
The ~hAn~ in the la~er output with passage of the time was observed al50 in comparison of use and non-use of the gas regenerator. The results are as shown in Fig.10.
From this figure it is unde~tood that, lf the regenerator is not u~ed, the la~er output ~ fic~ntly decreases, and that, contrarily to this, if used, the laser output can be maintained at al~ost a constant level.

...
,."~. ~ . ~ .
.
. ~
- , . . ~. - - .- .

- .
- . , .

Claims (3)

1. A method of regenerating He-N2-CO2 mixed gas for reuse in a carbon dioxide gas laser generator comprising contacting the mixed gas used in the laser generator with a precious metal catalyst at a temperature exceeding 200°C and up to 350°C to react CO and O2 with NO x in the used gas; utilizing the reaction heat for preheating the unreacted mixed gas; cooling the reacted mixed gas to a temperature usable in the laser oscillation; removing dust from the mixed gas; and recycling the mixed gas to the laser generator.

2. An apparatus for regenerating He-N2-CO2 mixed gas for a carbon dioxide gas laser generator, comprising a gas preheater for preheating the mixed gas used in the laser generator; a reactor which has a heating means and is packed with a precious metal catalyst for reacting CO and O2 with NO x in the preheated mixed gas; a gas cooler for cooling the gas after the reaction; a filter for removing dust from the gas after cooling; a means for recycling the regenerated gas to the laser apparatus; and a means for supplying a He-CO-O2 mixed gas to the reactor packed with the catalyst for reactivating the catalyst.

3. An apparatus for regenerating He-N2-CO2 mixed gas according to claim 2, wherein the catalyst is a platinum catalyst supported on alumina.