PROCESS AND APPARATUS FOR HIGH PRESSURE GAS COOLING IN AN ATMOSPHERIC OVEN
Field of the Invention The present invention is directed to a process and apparatus for recycling and purifying a cooling gas, such as helium gas, in the presence of a treatment gas, such as a cementing gas, for use with an atmospheric furnace to treat the components.
BACKGROUND OF THE INVENTION Conventionally. cementing and treating the components, such as steel components, generally requires a heat treatment followed by a rapid cooling treatment using a fluid such as oil. The process that uses oil can originate safety and environmental interests. Exposure of the oil to a temperature of 900 ° C may cause the oil to volatilize and / or oxidize. The oxidized oil represents a degradation of the oil that must go beyond the cooling bath or be removed when the oil is changed. In any case, the oxidized oil and oil changes represent a waste stream that could be placed in or partially recycled. Generally, the oil remains in the treated components removed from the oil cooling bath. The oil tends to drip from the custom components that are handled or moved to the cleaning area. Incenses, landslides, and other hazards may occur as a result of the use of an oil cooling process.
^, a ^ ... ^ .., ....-...- it || t | (| | | | 1, | Components coated with spent cooling oil may require an additional cleaning step before they are shipped or manufactured.) Additionally, cooling with oil may cause the components to become significantly distorted. Problems proposed by the use of the oil as a cooling medium, gas, such as helium, has been used to cool the components after having been heated in an oven.US Patent No. 5,158,625 describes a process for heat treatment of the articles when cementing them in a medium of recycled gas that is in contact with the treated articles.The cementing gas is cooled by means of a thermal exchanger, of the type in which helium is used as a cementing gas, and stored under maintenance pressure in a regulating container At the end of a cementing operation, a helium charge is removed from the treatment enclosure, in the final phase by means of a pump until a main vacuum is obtained. The extracted helium is produced to purify the pressure by means of a compressor associated with a mechanical filter, and the helium under pressure is sent to a purifier in which the impurities are removed, after which it is transferred, if desired, after recompression in the regulator container. U.S. Patent No. 5,938,866 discloses an apparatus for treating components by means of a gas mixture, comprising primarily a first light gas and less quantities of a second gas being heavier than the first gas. The apparatus has a treatment chamber, wherein the treatment occurs and a concentration, and purification device in which the gas mixture is concentrated and purified to increase the concentration of the first gas. The treatment chamber comprises an outlet member provided in an upper part of the treatment chamber and the means for moving the gas mixture up and out through the outlet member being positioned. U.S. Patent No. 4,867,808 describes a process for the thermal treatment of metal machine parts when heated in a vacuum oven followed by cooling in a refrigerant gas under higher atmospheric pressure and with refrigerant gas circulation. United States No. 5, 1 73, 524 describes a gas rapid cooling process wherein an increased cooling rate of an article heated to a high temperature is achieved by flowing a mixture of inert gas of helium and another inert gas over the article under turbulent flow conditions. An object of the present invention is to provide a process for recycling a cooling gas in an atmospheric heat treatment furnace system. Another object of the present invention is to provide a process for recycling a cooling gas, such as helium, in an atmospheric cement kiln system. It is an object of the present invention to provide an apparatus for the gas treatment of the components in an atmospheric furnace and having m iors for the cooling of the components of the oven
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atmospheric using a recycled cooling gas. Another object of the present invention to provide a process and aoarato that effectively provides means to recycle a gas cooling ce, such as helium, in an atmospheric furnace and cementitious' cja! The cooling gas is maintained at a consistent cooling temperature as required for the component to be processed.
BRIEF DESCRIPTION OF THE INVENTION The invention relates to a process for the thermal treatment of the components in an atmospheric heat treatment furnace. CLT comprises the steps of: • 3 treating a component in an atmospheric furnace with a gas Such a process is carried out in a manner such as an endothermic gas, heated to a desired temperature required to treat the component, and feeding the heat-treated component containing the gas into a cooling chamber. feed a cooling gas into the cooling chamber to face the treated component and mix with the gas. = • = - E--: c feed the treatment gas and the gas mixture tra: a ~ e c ce to step (c) into a gas recovery chamber where gas ce "eatment and cooling gas are separated for prc :: -:: "= '_ ~ purified gas and process gas cooling and feeding the treatment gas purified of step (d)
^^^^^^^^^ ^ jie Mey back to the cooling chamber effectively recycling such as the cooling gas back to the cooling chamber; and (f) removing the cooled treated component from the gas cooling chamber. If the furnace is approved to cool the pressure, then the cooling chamber could be removed and therefore refer to the cooling chamber in steps (b), (c), (e) and (f) should mean the furnace according to it is described in step (a) of the new process of this invention. The process of this invention is suitable for the treatment of components made of carbon, alloy steels and utensils.
Of particular importance are steel cementing grades such as grades AISI 51 20, 81 1 5, 8620 and 931 0. A principal use of novel process of this invention is to be used in atmospheric cement kilns in which the treatment g. it can be at least one gas selected from the group comprising methane, methane, carbon monoxide, nitrogen, propane and butane. A common treatment gas for cementing is the endothermic gas that consists of approximately 20% carbon monoxide. 4 O of hydrogen and 40% of nitrogen. The treatment gas could be heated to about 750 ° C and about 1200 ° C, preferably about 800 ° C and about 1000 ° C. For the cementing treatment of the components, the cement cements should be heated to between about 850 ° C and about 10 ° C: C, and preferably about
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900 ° C and accl atively 950 ° C. The cooling gas could be at least one gas selected from the group consisting of helium, preferably ~ 5-: as the main component (> 50%) and the group consisting of argon and carbon monoxide as the component less. The preferred cooling could be helium. The cooling gas is presumed to be at least 37 psia and preferably between about 7 psia and about 890 psia, and more preferably about 147 psia and about 368 psia. : -5-: The cooled treated is generally removed from the atmospheric pressure chamber and slightly above the ambient temperature, also referred to as subject. to an apparatus for the treatment ce • connertes by a gas in an atmospheric furnace that compnae _- -c - or atmospheric adapted to receive the treatment gas. -competent to be treated by gas, the atmospheric furnace aooo sce a ^ -a cooling chamber that is adapted to receive e:The coil of the atmospheric furnace and a cooling gas are added to the refrigeration coupled to a recovery device that is scaled to receive the spent treatment gas and the gas. It has means for separating the gases in order to proportions of the purified cooling; the recovery device: - oe gss acoco 3co to the cooling chamber and adapted to transmit e oas o.- - 'caco in the cooling chamber; and the operable apparatus of the cooling gas can be recycled between the ce-to-e-tc chamber and the recovery device.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagram of a gas cooling system. Figure 2 is a schematic of a helium / endothermic gas cooling system of the present invention. Figure 3 is a schematic of another embodiment of a helium gas cooling system of the present invention.
DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows an orientation equipment that will allow helium cooling for an atmospheric cement kiln using an endothermic gas or a vacuum cement kiln using a gas such as propane or methane. At the end of the cementing stage, the furnace 1 is opened and the components and the atmosphere inlet of the furnace, by means of the duct 2, heated the chamber to vacuum 3. The heated vacuum chamber 3 is sealed from the furnace 1 and the helium cooling chamber 5. In the closing of the chamber under a slow vacuum 3, the atmosphere is eliminated by means of a vacuum pump 9. During the entire process, the heated vacuum chamber 3 remains in place. the oven temperature in such a way that the components do not start to cool. Following the elimination of the atmosphere of the chamber at a slow vacuum 3, the chamber can be filled or not filled with helium at a pressure, for example , approximately 14.7 psia The components will move to the helium cooling chamber 5 when the chamber has satisfied the following
5. A I-.3¿.-t J, ^ conditions. The chamber 5 is empty of the previous charge of the components, the chamber has been sealed from the external atmosphere, and the external atmosphere has been removed from the chamber 5 by means of the vacuum pump 9. Once the seal between the chambers 3 and 5 are broken, the components will move to chamber 5 and the seal will once again be established between chambers 3 and 5. Chamber 5 will thus receive helium at the cooling pressure (eg 290 psia ). Following the cooling operation, helium is removed from chamber 5 via conduit 10 to the helium recovery system 1 1 and thus the components are moved to the next stage in the process, for example, fabrication. The spent helium is purified to a desired level in the helium recovery system 1 1 and the purified helium returns to chamber 5 via conduit 1 2. The atmospheric cementing processes that are cooled with helium find the use of helium very expensive if they do not recycle the helium or require the additional capital cost for the furnace equipment. The subject invention recycles the helium with the present cementing gases and maintains a consistent cooling atmosphere as needed by the components to be processed. Figure 2 shows one embodiment of a novel process of the subject invention. Various components described in Figure 1 have the same numerical indicators according to the components in Figure 2. The cemented components plus the atmosphere of the furnace moves directly into the cooling chamber 3 and is thus sealed from the h orno 1 The cooling chamber 3 is pressurized to the same with the cooling gas of the cooling gas recovery system and the components are cooled. The cooling gas plus the furnace atmosphere is thus removed from the cooling chamber 3 by means of the cooling gas recovery system 7. The cooled components are thus moved in the next step in the process 5 (e.g. ). Figure 2 shows the difference between the modality described by Figure 1 above and the subject invention. The subject invention results in a reduced equipment cost and process complexity. Both require the use of a cooling chamber. However, the 10 previous recovery systems were not feasible to eliminate the cementing gases. Table 1 shows a typical cementing gas composition that could enter the cooling chamber when evacuation of the chamber is not performed. In addition to water, a significant amount of carbon dioxide, carbon monoxide, methane, hydrogen and nitrogen enter the system. With the addition of the cooling gas at 20 bar, the cementing gas will represent 5% of the total gas in the cooling chamber. TABLE 1
The purification of spent cooling gps could not be
i i immiiMMiiWflitf.f - "* -? - *" * "--¡r ~? y -ii *" - * possible without oxygen since oxygen must be added to remove hydrogen. The subject invention could be used as a catalyst followed by a molecular filter to purify the entire cooling gas stream and return the pure helium to the cooling chamber. Figure 3 shows a gas recovery system in which the cooling gas flows from the cooling chamber 20 via the duct 24 to the suction side of the screw compressor submerged in oil 25. The pressure of the suction side of the compressor of screws submerged in oil 25 is controlled to a maximum by the pressure regulator 23. The screw compressor submerged in oil 25 will discharge the cooling gas to 1 50 psig or more. The discharge of the screw compressor submerged in oil 25 will pass through the oil removal equipment (not shown) into the conduit 26 and then through the suction side of the diaphragm compressor 27. The discharge
15 of the compressor 27 is at a higher pressure such as 575 psig (-40 bar absolute) Between the oil removal equipment and the compressor 27, approximately 60% of the total flow through the diaphragm compressor 27 of the cooling gas take part of the bifurcation 29 and pass through the membrane 30 The membrane will reject the methane, carbon monoxide, carbon dioxide and nitrogen through the valve 32. penetrated membrane will regress to the suction side of the compressor of screws submerged in oil 25 oor medium of duct 22 and duct 24 The cross-sectional areas for feeding, penetration and refining are given in Table 2
• - * - - • < The value shown in Table 2 represents the composition of the steady state of the gas in the cooling chamber (ie, the cooling gas plus the endo gas). ). The penetration to approximately 94% pure helium will mix with the unpurified gas and pass through the catalyst and the removal of water. The composition of the gas in the receiver before the equalization with the cooling chamber is approximately 95% pure helium. In the equalization with the cooling chamber, the endo gases as shown in Table 1, decrease the purity of the helium to approximately 90%. Oxygen was not shown in the simulation below but could occur because the air inlet valve 34 feeds the suction of the compressor 25. The oxygen was completely consumed in the conversion of hydrogen to water and the carbon monoxide to dioxide carbon. The presence of oxygen in the membrane is expected to have a negligible impact on helium recovery and final steady-state gas composition. TABLE 2 PROCESS PARAMETERS CALCULATED For Membrane 1 9
Recovery percent of helium in stream No. 22 = 99.44 Recovery percent of nitrogen in stream No. 33 = 81 .40 Recovery percent of hydrogen in stream No. 33 = 0.97 Recovery percent of carbon monoxide in the stream Current No. 33 =
78. 64. Percent recovery of water in stream No. 33 = 0.02 Percent recovery of carbon dioxide in stream No. 33 =
1 8.40 Percent recovery of methane in stream No. 33 = 83.91 The hot gas from the diaphragm compressor 27 passes through the catalyst layer 36 to convert some hydrogen into water and carbon monoxide to carbon dioxide. Oxygen is provided for the reaction by the air inlet valve 34 to the suction side of the oil submerged screw compressor 25. The valve 34 allows air to enter the cooling gas recovery system and is controlled by a signal of the hydrogen analyzer 38. When the hydrogen level is above a predetermined reference point, the hydrogen analyzer 38 will send a signal to the valve 34 to be left in the air. The analyzer 38 maintains an excess of hydrogen in the system. The combination of the catalyst and the excess of hydrogen or rig will initiate the elimination of oxygen at the PPM level such as <; 1 0 PPM The hydrogen analyzer is located in the conduit 40 after the valve 42. Following the catalyst 36, the gas stream is cooled in the thermal exchanger 44 and passes through the separator 46.
, i? i to eliminate the water dragged. The entrained water passes to an interceptor and is discharged from the system. The interceptor can be operated by a float or a stopwatch (T). The interceptor seals the external air cooling gas recovery system and does not allow the cooling gas to escape from the cooling gas recovery system. The cooling gas will fill the cooling gas ballast tank 48 of the valve 56 until the pressure reaches, for example, 590 psig as measured by PIT 50. Not all the gas in the cooling chamber is removed from the cooling system. recovery of cooling gas and some cooling gas is lost during purification with the membrane 30. The replacement of the cooling gas lost with helium is made on the suction side of the screw compressor submerged in oil 25. When the pressure of Suction of the oil-submerged screw compressor falls under a predetermined reference point, then the helium manufacture will flow from the helium store 52 to the control valve (not shown). Once the cooling gas ballast tank 48 reaches a predetermined reference point pressure, then the cooling gas recovery system has finished and closed. When the cooling gas recovery system is closed, the pivot valve 54 closes. The air / nitrogen or other gas fills the cooling chamber and the components are removed. The empty chamber is closed and purified with nitrogen or another gas. A new chamber of hot components is thus located in the cooling chamber 20 and the cooling gas ballast tank 48 is equalized with the chamber. cooling 20 through the pivot valve 60. The next cycle begins. For the preferred embodiment of the subject invention, the cooling gas pressure requirements of about 10
5 bars or less could use only one compressor. For approximately 90% purity of helium and conversion of carbon monoxide, the compressor could circulate 60% of the gas recovered in the cooling chamber through the compressor and through the membrane. Therefore, the compressor could remove 875 CF of the cooling gas from the
10 cooling chamber. From the discharge of the compressor, 525 CF could pass through the membrane back to the suction side of the compressor. For a 15 minute time cycle, the compressor 27 could move 1 400 CF or 5600 SCHF. In this way, the compressor 27 is significantly smaller at 3500 SCFH. One more compressor
15 small 27 is saved in the cost of capital and the cost of operation over the previous technique. A water separator could be used to remove stray water (Figure 3 # 46). The heat exchanger 44 could be expanded with a cooler for lower volumes of water in the cooling gas. The amount of water in the cooling gas could
20 constant pressure as a saturated gas, at the temperature and pressure of the stream, entering the ballast tank 48. Modifications can be made to the gas recovery system of the cooling of the object object as follows: . The cooling chamber 20 may not be required if the chamber of the furnace was set for the cooling pressures. He
Cooling gas recovery system could stay the same. 2. A separate vacuum pump could be used in a side process connected to the duct 24 before the valve 23 to evacuate the cooling chamber 20 in such a way that a
5 greater percentage of cooling gas. The vacuum pump could ignite after the cooling chamber reached atmospheric pressure. 3. Diaphragm and oil submerged screw compressors could be replaced with another style of compressors and / or
10 combine in a compressor. 4. The purification side stream flowing through the membrane could take place anywhere after the discharge of the compressor 27. 5. The purification of the side stream could replace the membrane 30 with molecular filter or a purification. 6. The purification of the side stream could use a molecular filter or other membrane in the reaffirmed stream of the membrane 30 to increase helium recovery. As well, the refining could be placed in a separate hall and serve as a purification gas for
20 the cooling chamber. 7. The molecular filter or other membrane could be added to the penetration of the membrane 30 for further purification. 8. The valve 34 could be pure oxygen input instead of air. 9. The heat exchanger 44 could be increased with a
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refrigerator to further reduce the amount of water in the cooling gas. 10. The system could operate continuously if a line and a valve were placed between the cooling gas ballast tank 5 48 and the lateral side of the screw compressor submerged in oil 25, in this way, allowing the system to operate continuously could increasing the helium content of the cooling gas or a smaller compressor 25 to obtain the same helium content in the cooling gas. 10 11. More than one cooling chamber can be used in a cooling gas recovery system. The equipment can be measured based on the number of cooling chambers and the controls are adjusted in such a way that the cooling gas in each cooling chamber can reach the desired gas pressure and composition. 12. The minimization of the amount of oxygen present in the cooling chamber 20 during the cooling step could require a scrubbing gas through the cooling chamber before the introduction of the hot components. The purification gas could be nitrogen, argon, helium, or endothermic gas used in the process
20 Cementing 13 To achieve an oxygen-free cooling chamber, a separate chamber can be added to receive the components of the cooling chamber. The additional chamber could have a purification of nitrogerc argon or helium. 25"< 4 The ballast tank 48 can provide a gas of
purification to the cooling chamber 20. The cooling gas recovery system could be established to operate continuously. However, after the components are removed from the cooling chamber 20, the valves 60 and 54 can be opened and allow the gas to purify the cooling chamber 20 for a period of time. At the end of the debugging, the valve 56 could be closed first and then the valve 22 could be closed, leaving the chamber at close atmospheric pressure. Then, the next cycle could begin with the addition of the hot components to the cooling chamber 20. 1 5. The gas flow through the conduit 29 could be reduced resulting in the purity of the lower helium as the cooling gas. The helium purity of 40% or more can be used depending on the desired cooling curves in the cooling chamber. 1 6. The oxygen or air can be introduced into the cooling gas recovery system after the compressor 27. The introduction of additional gas after the compressor could reduce the flow through the valve 34 since the membrane could not reject anything of oxygen. This option could have the greatest value when pure oxygen is used to oxidize hydrogen and carbon dioxide 1 7. The catalyst temperature and type can be adjusted to minimize or virtually eliminate the conversion of carbon monoxide to carbon dioxide. A 90% helium purity requires only 40% of the current through conduit 29 when the carbon monoxide is not oxidized. A 40% flow in conduit 29
ka n represents a 33% reduction over the preferred method as described above. Table 3 shows the feeding, refining and penetration compositions when carbon monoxide is not converted to carbon dioxide. The membrane is about four times as efficient in discharging carbon monoxide as its carbon dioxide. Another advantage is that it is required less oxygen consumption for the oxidation of the cooling gas recovery system This option could be the preferred method if the reduction in the cooling chamber of carbon dioxide to carbon monoxide is possible and undesirable. TABLE 3 PROCESS PARAMETERS CALCULATED For the Membrane 30 without conversion CO FEED REAF. PENETRA. F, MMSCFD (60F) 1 0.07797 0.922 PRES, psia 15000 150.00 6.00 TEMP., F 10800 108.00 10800 Molecular Weight 6 18 25.55 4.54 Viscos, cp 00206 00185 0.0203 CONCENTRATIONS,% Mol HELIO 888000 M0.0000 95.4633 NITROGEN 56000 58.9144 1.0917 HYDROGEN 2 1000 04003 22437 MONOXIDE C = CARBON 28000 28.5080 0.6261 WATER 02000 0.0007 0.2169 CARBON DIOXIDE 04000 1 0937 03413 METANO 0 1000 1.0829 0.0169
Recuperator ccr cent of helium in the stream No 22 = 99 12 Recuperator ccr cent of nitrogen in the stream No 33 = 8202 Recuperator ce cent of h? D ogen in the stream No 33 = 1 49 Recuperator hundred percent of carbon in the stream No 33 =
*** a ~ J "- '" - ^ ¿¿g 79.38. Percent recovery of water in stream No. 33 = 0.03 Percent recovery of carbon dioxide in stream No. 33 = 31 .32 Percent recovery of methane in stream No. 33 = 84.43 The invention is not limited to the shown and it will be appreciated that it is intended to cover all modifications and equipment within the scope of the appended claims.