KR20230086828A - Reducing apparatus of vacuum carburizing harmful exhaust gas and method for reducing vacuum carburizing harmful exhaust gas using the same - Google Patents

Abstract

The present invention relates to a vacuum carburizing harmful exhaust gas reduction device and a vacuum carburizing harmful exhaust gas reduction method using the same. and a catalyst carrier carrying a catalyst containing at least one selected from the group consisting of Pt, Pd, and alloys thereof, wherein exhaust gas subjected to heat treatment in the high-temperature decomposition unit contacts the catalyst carrier. It is characterized in that it includes; part.
According to the present invention, it is possible to dramatically reduce harmful substances such as carbon monoxide, nitrogen oxides, benzene, and total hydrocarbon (THC) in exhaust gas discharged through a vacuum pump during a vacuum carburizing process.

Description

Reducing apparatus of vacuum carburizing harmful exhaust gas and method for reducing vacuum carburizing harmful exhaust gas using the same}

The present invention relates to a vacuum carburizing harmful exhaust gas reduction device and a vacuum carburizing harmful exhaust gas reduction method using the same, and more particularly, carbon monoxide, nitrogen oxides, benzene, THC ( It relates to a vacuum carburizing harmful exhaust gas reduction device that can dramatically reduce harmful substances such as total hydrocarbon) through high heat and catalytic treatment, and a vacuum carburizing harmful exhaust gas reduction method using the same.

In recent years, securing durability of transmission parts has emerged as one of the major challenges in line with the trend of high-performance and high-output automobile engines.

In the case of general gas carburizing of automobile transmission gears or shaft parts, due to the presence of oxygen in the gas in the heat treatment atmosphere, Si, Cr, and Mn elements, which are elements that increase hardenability in gear materials, meet, and oxides such as SiO2, Cr2O3, and MnO2 form grain boundaries on the top surface of the base material. It is segregated to produce grain boundary oxidation, which provides a cause of lowering the bending fatigue strength and contact fatigue strength of gears or shafts. A heat treatment process to improve these problems is a low-pressure vacuum carburizing process.

The vacuum carburizing process is a new heat treatment method in which carburizing is performed in a vacuum atmosphere and quenching with high-pressure gas, and durability (fatigue resistance and wear resistance) is dramatically improved because an abnormal surface layer is not generated, and when carburizing It is known as a new carburizing method that can shorten production time because there is almost no carbon dioxide generation, gas is mainly used as a quenching medium, and it is eco-friendly because there is almost no waste oil/wastewater treatment. there is.

When such a vacuum carburizing process is applied, the grain boundary oxide layer is reduced to zero, and the bending fatigue strength is improved by 20% and the contact fatigue strength is also improved by 30% or more. In particular, low-pressure vacuum carburizing is an eco-friendly heat treatment process, which calculates the surface area of the gear or shaft, which is the object to be treated, before processing, and carburizes the carbon flux in consideration of the target effective hardening depth in a pulse-like carburizing and diffusion process. In addition, it is a heat treatment method with excellent productivity as it can be processed at a high temperature of about 1050 degrees.

In the vacuum carburizing process, acetylene (C2H2) in the carburizing step and nitrogen (N2) in the diffusion step are used, and exhausted through a vacuum pump, synthetic oil (ester, RCOO-R') in the pump and acetone (CH3OH) partially coming out of the acetylene cylinder Carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (Sox), volatile organic compounds (VOCs), tar, soot (particulate matter), etc. Since it is present in the exhaust gas, a problem of polluting the atmospheric environment has arisen.

In order to solve this problem, conventionally, tar, soot, etc. are filtered out of exhaust gas through a filter at a low temperature, and harmful exhaust gases passing through are treated using a catalyst such as Ti, but the filter is clogged due to excessive tar and soot generation. However, problems such as accelerating poisoning and deterioration of the catalyst still occurred.

The present invention was derived to solve the above problems, and harmful substances such as carbon monoxide, nitrogen oxides, benzene, and total hydrocarbon (THC) in exhaust gas discharged through a vacuum pump during the vacuum carburizing process are removed through high heat and catalyst treatment. It is an object to provide a vacuum carburizing harmful exhaust gas reduction device and a vacuum carburizing harmful exhaust gas reduction method using the same, which can improve stability and efficiency by dramatically reducing.

In order to achieve the above object, the vacuum carburizing harmful exhaust gas reduction apparatus according to the present invention includes a high-temperature cracking unit for heating the exhaust gas discharged from the vacuum pump in the vacuum carburizing process to 500 to 1500 ° C.; and a catalyst carrier carrying a catalyst containing at least one selected from the group consisting of Pt, Pd, and alloys thereof, wherein exhaust gas subjected to heat treatment in the high-temperature decomposition unit contacts the catalyst carrier. It is characterized in that it includes; part.

Air may be injected into the high-temperature decomposition unit to create an oxidizing atmosphere,

The volume ratio between the injected air and the introduced exhaust gas may be 1 to 3:1, and the air may be injected so that the hydrogen concentration inside the high-temperature decomposition unit becomes 4% by volume or less.

The catalyst carrier may be a ceramic honeycomb carrier.

The catalyst may be supported on a catalyst support including La-doped alumina, and may further include a catalyst improver including zeolite.

Another present invention is a vacuum carburizing harmful exhaust gas reduction method using the vacuum carburizing harmful exhaust gas reduction device, comprising: introducing exhaust gas discharged from a vacuum pump in the vacuum carburizing process and introduced into a high-temperature decomposition unit; heating the exhaust gas flowing into the high-temperature decomposition unit to 500 to 1500 °C; and introducing the exhaust gas subjected to heat treatment in the high-temperature decomposition unit into the high-temperature catalyst unit and contacting the catalyst carrier.

The introduced exhaust gas may be heated in an oxidizing atmosphere by injecting air into the high-temperature decomposition unit.

According to the present invention, harmful substances such as carbon monoxide, nitrogen oxides, benzene, and total hydrocarbon (THC) in the exhaust gas discharged through the vacuum pump during the vacuum carburizing process can be drastically reduced through high heat and catalytic treatment.

By heating the exhaust gas introduced into the high-temperature cracking unit according to the present invention at a high temperature to cause an exothermic reaction and a combustion reaction, it is possible to oxidize and remove hydrocarbon substances, tar, soot, etc. in the exhaust gas, and furthermore, carbon monoxide Oxidation of can also be removed at the same time.

In addition, even when the exhaust gas heated to a high temperature of 500 degrees or more comes into contact with the catalyst carrier of the high-temperature catalyst part according to the present invention, excellent catalytic reactivity can be maintained even at a higher temperature due to the ceramic honeycomb carrier having excellent heat resistance.

1 is a flow chart for explaining a vacuum carburizing harmful exhaust gas reduction apparatus according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail through examples. However, the above embodiments are intended to be explained in detail to the extent that those skilled in the art can easily practice the invention, which means that the technical spirit and scope of the present invention are limited. I don't.

C ₂ H ₂ and N ₂ , which are vent gases generated in a typical high-temperature carburizing process, react with the pump oil of the vacuum pump 120 and undergo organic chemical pyrolysis, resulting in incomplete carbon monoxide (CO ), nitrogen oxides (NOx), sulfur oxides (SOx), and VOCs (volatile organic compounds). In addition, these fraudulent vent gases react at high temperature with acetone (CH3OH) partially emitted from an acetylene cylinder, oxygen contained in a furnace refractory board, etc., and undergo organic chemical thermal decomposition to generate carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (Sox), and rare organic compounds. (VOCs), tar, soot, etc. are included in the exhaust gas and emitted.

Therefore, in the present invention, the exhaust gas discharged through the vacuum pump 120 through the vacuum carburizing furnace 110 is introduced into the high-temperature cracking unit 210, and then heated to 500 to 1,500 ° C., preferably using an electric heater or a gas burner. More specifically, when heated to 800 to 1,000 ° C, harmful substances in the exhaust gas cause an exothermic reaction and combustion reaction, so that hydrocarbon substances, tar, soot, etc. in the exhaust gas are oxidized and removed, and carbon monoxide is also oxidized. can be removed

At this time, when air is injected into the high-temperature decomposition unit 210 to create an oxidizing atmosphere inside, it is advantageous for complete combustion and exothermic reaction. The air injection may be performed through a blower at a front end of the vacuum pump 120 .

It is effective that the air injection is 1 to 3:1 relative to the total flow rate of the introduced exhaust gas. In addition, since the concentration of hydrogen (H 2 ) is as high as 30% by volume or more in the exhaust gas from which acetylene (C 2 H ₂ ) gas is decomposed, there is a risk of explosion when reacting with oxygen. Therefore, it is preferable to adjust the air injection so that the hydrogen concentration inside the high-temperature decomposition unit 210 becomes 4% or less after the air injection.

If it does not pass through the high-temperature decomposition unit 210, the low-temperature exhaust gas discharged from the vacuum pump 120 directly contacts the catalyst of the high-temperature catalyst unit 220, which will be described later. In this case, tar or soot Accumulation in the catalyst may cause a problem of rapidly deteriorating catalyst activity and durability.

Next, some or all of the exhaust gas heated in the high-temperature decomposition unit 210 is introduced into the high-temperature catalyst unit 220 including the catalyst supporter and comes into contact with the catalyst supporter.

The catalyst carrier includes at least one catalyst selected from the group consisting of Pt, Pd, and alloys thereof, and it is preferable that the catalyst carrier is a ceramic honeycomb carrier to enhance heat resistance. The ceramic honeycomb carrier may be, for example, a cordierite honeycomb carrier.

If a carrier such as a spherical, pellet, or disk type instead of a honeycomb carrier is used, the back pressure of the exhaust gas may increase, which may cause problems in the operation of the apparatus of the present invention and reduce the efficiency of exhaust gas purification. may be Therefore, when the honeycomb carrier is used, there is an advantage in that the exhaust gas flows more smoothly.

More specifically, in order to minimize back pressure, the honeycomb ceramic carrier is preferably 400 cell density and 6 mil wall thickness (400/6 cell/in2). Note, the larger the cell density rk, the smaller the wall thickness, and the larger the volume of the catalyst, the larger the total surface area of the catalyst, so catalyst efficiency can be improved, but back pressure can be high.

The catalyst may include one or more catalysts selected from the group consisting of Pt, Pd, and alloys thereof. The catalyst can easily oxidize tar, soot, carbon monoxide, HC-based hydrocarbons, etc. as an oxidation catalyst, and is preferably a Pt/Pd-based catalyst, Pt;Pd = 4/1.

In order to maximize the efficiency of the catalyst, it may be supported on an alumina catalyst support to increase the surface area of the catalyst. Furthermore, in order to improve heat resistance, an alloyed alumina catalyst support doped with a rare earth component may be used, and for example, an alumina catalyst support doped with lanthanum (La) may be used.

When the alumina catalyst support is not included, the surface area decreases rapidly as the temperature rises, and thus the catalytic performance may be reduced.

In addition, the catalyst carrier according to the present invention may further include a catalyst promoter such as zeolite in order to efficiently remove tar, soot, long chain hydrocarbons, etc. from a low temperature.

Hereinafter, a vacuum carburizing harmful exhaust gas reduction method using the vacuum carburizing harmful exhaust gas reduction device 100 according to the present invention described above will be described.

First, the exhaust gas discharged and introduced from the vacuum pump 120 in the vacuum carburizing process is introduced into the high-temperature cracking unit 210. (S1 step)

Thereafter, the exhaust gas flowing into the high-temperature decomposition unit 210 is heated to 500 to 1500 °C. (Step S2) Since the heating method and reason have been described above, it is omitted. Next, the exhaust gas subjected to heat treatment in the high-temperature decomposition unit 210 is introduced into the high-temperature catalyst unit 220 and brought into contact with the catalyst carrier to cause a catalytic reaction. (Step S3) In particular, it is advantageous for complete combustion and exothermic reaction to heat the introduced exhaust gas in an oxidizing atmosphere by injecting air into the high-temperature decomposition unit 210 before the step S2. The air injection may be performed through a blower in front of the vacuum pump 120. It is effective that the air injection is 1 to 3: 1 relative to the total flow rate of the introduced exhaust gas, and since the concentration of hydrogen (H ₂ ) is as high as 30% by volume or more in the exhaust gas from which acetylene (C2H2) gas is decomposed, oxygen and In case of reaction, there is a risk of explosion. Therefore, when the hydrogen concentration in the high-temperature decomposition unit 210 becomes 4% or less by the air injection, the risk of explosion can be reduced.

<Experiment evaluation>

1. Manufacture of vacuum carburizing harmful exhaust gas reduction device according to the present invention

First, a catalyst carrier was prepared using a cordierite honeycomb ceramic carrier. The honeycomb ceramic carrier had a 400 cell density, a 6 mil wall thickness of 400/6 cell/in2, and a carrier volume of 2 L. Next, 350 g/L base of La doped alumina catalyst support and 50 g/L base of zeolite as a promoter were added to the honeycomb carrier. Thereafter, Pt and Pd were impregnated into the alumina catalyst support at a ratio of 4:1 and 9/g/L base to synthesize a wash coat, which was then coated on the cordierite ceramic support. The coating amount of the catalyst was 9 g/L, and a high-temperature catalyst part made of stainless steel was prepared to construct the catalyst system.

Thereafter, the outlet of the high-temperature decomposition unit and the inlet of the prepared high-temperature catalyst unit were connected.

2. Measurement of the concentration of each harmful exhaust gas

The exhaust gas discharged from the vacuum pump of the vacuum carburizing unit was connected to flow into the prepared high-temperature decomposition unit. The specific operating conditions of the vacuum carburizing unit were as follows.

1) Vacuum carburizing furnace carburizing temperature: 980 ℃

2) Vacuum Carburizing Furnace Quantity: 10 X Vacuum pump 2 X MDS 1

3) Always running vacuum pump

4) Oil for vacuum pump: Synthetic oil (Ester oil with additives) / n-phenyl-1-naphthylamine additive 0.1 to 0.5% by weight

5) Exhaust gas temperature after passing through the vacuum pump: 25~35℃

Exhaust gas discharged after passing through the vacuum pump passes through the vacuum carburizing harmful exhaust gas reduction device manufactured according to the present invention (Example) and exhaust gas that does not pass through the reduction device according to the present invention after passing through the vacuum pump The results of measuring the concentration of each hazardous substance in (Comparative Example) were as follows. For reference, the gas input to the vacuum carburizing furnace for measuring the concentration of each hazardous substance was as follows.

(1) When measuring the concentration of NOx, SOx, and CO: After inputting 1,000 ℓ/hr of N2, supplying 4,000 ℓ/hr of C2H2 at 980 °C and 30 SEC by convection heating

(2) When measuring THC concentration: 4,000ℓ/hr of C2H2 at 980 ℃, 30SEC input

(3) When measuring benzene concentration (collection measurement): 4,000 ℓ/hr of C2H2 at 980 ℃, 60SEC input

3. Results of concentration measurement for each harmful exhaust gas

In the exhaust gas (Example) that has passed through the vacuum carburizing harmful exhaust gas reduction device manufactured according to the present invention, carbon monoxide (CO) O ppm, nitrogen oxides (NOx) 1 ppm, sulfur oxides (Sox) 1 ppm, THC (Total Hydrocarbon) 80 ppm, benzene 0 ppm was confirmed.

On the other hand, in the case of the exhaust gas (comparative example) discharged from the vacuum pump without passing through the exhaust gas reduction device according to the present invention, carbon monoxide (CO) 12600 ppm, nitrogen oxides (NOx) 290 ppm, sulfur oxides (Sox) 20 ppm , THC 12900 ppm, benzene 9 ppm.

Through this, it was confirmed that when the vacuum carburizing harmful exhaust gas reduction device according to the present invention is applied, harmful substances in exhaust gas discharged are greatly reduced.

100; vacuum carburizing part
110; vacuum carburizing furnace
120; vacuum pump
200; Vacuum Carburizing Harmful Exhaust Gas Reduction Device
210: high temperature decomposition part
220: high temperature catalyst

Claims (9)

A high-temperature decomposition unit for heating the exhaust gas discharged from the vacuum pump in the vacuum carburizing process to 500 to 1500 ° C; and
A high-temperature catalyst unit including a catalyst carrier carrying a catalyst containing at least one selected from the group consisting of Pt, Pd, and alloys thereof, wherein exhaust gas subjected to heat treatment in the high-temperature decomposition unit contacts the catalyst carrier A vacuum carburizing harmful exhaust gas reduction device, characterized in that it comprises a.
According to claim 1,
The vacuum carburizing harmful exhaust gas reduction device, characterized in that air is injected to the high-temperature decomposition part to create an oxidizing atmosphere.
According to claim 2,
Vacuum carburizing harmful exhaust gas reduction device, characterized in that the volume ratio of the injected air and the introduced exhaust gas is 1 to 3: 1.
According to claim 1,
Vacuum carburizing harmful exhaust gas reduction device, characterized in that for injecting the air so that the hydrogen concentration inside the high-temperature cracking unit is 4% by volume or less.
According to claim 1,
The vacuum carburizing harmful exhaust gas reduction device, characterized in that the catalyst support is a ceramic honeycomb carrier.
According to claim 1,
The catalyst is a vacuum carburizing harmful exhaust gas reduction device, characterized in that supported on a catalyst support containing La-doped alumina.
According to claim 6,
The vacuum carburizing harmful exhaust gas reduction device, characterized in that the catalyst support further comprises zeolite.
In the vacuum carburizing harmful exhaust gas reduction method using the vacuum carburizing harmful exhaust gas reduction device according to any one of claims 1 to 7,
Step of introducing the exhaust gas discharged from the vacuum pump in the vacuum carburizing process into the high-temperature cracking unit;
heating the exhaust gas flowing into the high-temperature decomposition unit to 500 to 1500 °C; and
introducing the exhaust gas subjected to heat treatment in the high-temperature decomposition unit into the high-temperature catalyst unit and contacting the catalyst carrier;
Vacuum carburizing harmful exhaust gas reduction method comprising a.
According to claim 8,
Vacuum carburizing harmful exhaust gas reduction method, characterized in that by injecting air into the high-temperature cracking unit to heat the introduced exhaust gas in an oxidizing atmosphere.

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