JPS60238153A - Regeneration of catalyst used in oxidation of carbon monoxide - Google Patents

Abstract

PURPOSE:To keep the high oxidation ratio of CO and to enhance effect for largely conserving energy and reducing operation cost, by simultaneously performing the oxidizing action of CO and the regeneration of a deteriorated catalyst. CONSTITUTION:In a method for regenerating a catalyst used in the oxidation of CO in exhaust gas, oxidizing catalysts 5a, 5c having high activity are arranged in the upstream side of an exhaust gas flowline and deteriorated oxidizing catalyst 5b, 5d are arranged in the downstream side to perform oxidation of CO and the catalysts in the downstream side perform not only the oxidation of CO remaining in the exhaust gas issued from the catalyst beds in the upstream side but also the regeneration of the catalyst deteriorated by said gas. By this method, the high oxidation ratio of CO can be kept and the replacement of the catalyst or the high temp. heating of exhaust gas is dispensed with while CO contained in exhaust gas is oxidized perfectly. As a result, the entire amount of heat of CO-oxidation can be utilized in the regeneration of the deteriorated catalyst and effect for largely conserving energy and reducing operation cost can be enhanced.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a method for regenerating an oxidation catalyst used to oxidize carbon monoxide in exhaust gas, recover oxidation heat, and prevent pollution. .

Conventional technology It is desirable to reduce carbon monoxide, which is generated in the manufacturing process of sintered ore and is contained in exhaust gas, for environmental protection and energy conservation.

The carbon monoxide contained in the exhaust gas due to incomplete combustion has a low concentration and is not oxidized at low temperatures, so methods of oxidizing it using a catalyst have been studied.

However, there is a problem in that the exhaust gas generally contains very small amounts of catalyst poisoning substances, and the catalyst deteriorates in a short period of time.

In other words, in addition to SOx and NOx, sintering exhaust gas contains extremely small amounts of catalyst poisoning substances, so in order to efficiently oxidize carbon monoxide with an oxidation catalyst, the catalyst must be replaced frequently. Alternatively, it is necessary to heat the gas to be treated to a high temperature to thermally desorb the poisonous substances adsorbed on the oxidation catalyst and restore the activity of the catalyst.

In order to regenerate a deteriorated catalyst, a method of regenerating the catalyst by raising the temperature while circulating exhaust gas has been known, and Japanese Patent Application Laid-Open No. 56-168825.56-168826.56-1
No. 68827 and No. 56-169734 also disclose a method of temperature raising regeneration under air circulation. These methods propose a method in which regeneration gas or air is heated, passed through a catalyst layer, and then heat is recovered using a heat exchanger, or a method in which the regeneration gas or air is heated and recycled.

However, in both of these methods, a heating furnace is separately provided to raise the temperature of exhaust gas or air for catalyst regeneration, which is not preferable in terms of energy saving. Furthermore, it requires a blower to circulate the exhaust gas and air, which has the disadvantage of high operating costs.

FIG. 3 shows an example of a conventional treatment flow for sintering exhaust gas.

Sintering exhaust gas contains SOx; 200-300ppm NOx; 150-250ppm Co; 1.0-1.2%, 02.14-16%, etc., so desulfurization, denitrification, and CO oxidation are performed to remove this. It is dissipating into the atmosphere.

After desulfurizing the sintering exhaust gas, the exhaust gas (I) receives heat in a rotary heat exchanger, is pressurized by a booster blower 2, and then heated in a heating furnace 3 to a temperature required for a denitrification reaction, for example, about 400°C. After that, the denitrification reactor 4a.

4b and is reduced by NH3. In the exhaust gas (m) after denitration, the CO in the exhaust gas (m) is oxidized by 02 in the exhaust gas by the CO oxidation catalyst 5 to become C02, and the rotary heat exchanger 1 exchanges heat with the exhaust gas CI) after desulfurization to the atmosphere. It is being dissipated.

When CO in the exhaust gas (m) after denitrification is oxidized with 02 in the exhaust gas by the CO oxidation catalyst 5, oxidation heat is generated, so the exhaust gas (IT) after CO oxidation is usually go-ioo'c.
The temperature rises to approximately 480°C to 500°C. Normally, heating in the heating furnace 3 only needs to be performed when the sintering equipment or other equipment is started up after being shut down or when the Co concentration in the exhaust gas decreases. In some cases, there is no need to heat, and the denitrification reaction or CO
The exhaust gas temperature can be raised to the temperature required for the oxidation reaction.

However, due to changes in sintered ore manufacturing operations,
The degree of od varies greatly. Co concentration is 1,0-1.2%
When the concentration shifts to a higher concentration side, the exhaust gas after CO oxidation (
Since the temperature of IT) increases, there is not much of a problem in this case, but if the Co concentration shifts to the lower concentration side,
If heat to the temperature required for denitrification or CO oxidation cannot be obtained, and the exhaust gas temperature drops as shown in Figure 4, CO will become extremely low.
The # conversion rate decreases and the deterioration of the oxidation catalyst progresses.

On the other hand, if the operation is carried out at a temperature of exhaust gas (m) after denitrification of 420°C or higher, at which the CO oxidation rate is difficult to decrease, #I'MIyl from the culvert is preferred.1. Since the heat exchange rate to the exhaust gas CI) after desulfurization in the rotary heat exchanger 1 is almost constant, heat loss to the atmospheric gas (V) increases, which is unfavorable in terms of energy saving. Furthermore, under high temperatures, the strength of equipment such as ducts, heat exchangers, pressure boosters, etc. is also reduced, posing the problem of requiring large-scale reinforcement and modification.

Means for Solving the Problems The present invention aims to solve the above-mentioned problems by dividing the oxidation catalyst into a plurality of catalyst layers of two or more stages in series with the gas flow. In the upstream stage of the exhaust gas, a highly active catalyst oxidizes CO in the exhaust gas, and in the downstream stage, the CO that could not be oxidized by the upstream catalyst is oxidized and the exhaust gas whose temperature has risen due to CO oxidation regenerates the deteriorated catalyst. It is characterized by

In addition, if the performance deterioration of the front stage oxidation catalyst layer progresses, the positions of the front and rear stage catalyst layers are reversed, and the rear stage catalyst that has completed regeneration is moved to the front stage relative to the gas flow, and the front stage catalyst layer whose performance has deteriorated is placed in the front stage relative to the gas flow. Oxidation or regeneration is performed by changing the location of the catalyst in the latter stage. This reversal of the catalyst position may be achieved by making the catalyst layers in multiple stages rotatable and rotating them intermittently.

Flow sheets for suitably implementing the method of the present invention are shown in FIGS. 1 and 5. FIG. 2 is a partially enlarged view of FIG. 1. In the method of the present invention, catalyst layers are arranged in multiple stages so as to intersect with the flow direction of the exhaust gas (m) after denitrification, and the oxidation of the exhaust gas and the regeneration of the deteriorated catalyst are performed simultaneously. In the examples shown in Figures 1 and 2, turbulence is created on the catalyst surface at right angles to the flow of exhaust gas, and in Figure 5, at an angle of about 45° to the flow of exhaust gas to promote oxidation. The oxidation catalysts [5] are arranged as shown.

The oxidation catalyst 5 is arranged in two stages, a front stage and a rear stage, with respect to the gas flow, as shown in detail in FIG. The number of stages in which this oxidation catalyst is arranged is not limited to two stages, but may be arranged in multiple stages of three or more stages. In the example shown in FIG. 2, two sets of two-stage rotary catalyst layers 6, 6a are arranged in the duct 7. Rotary catalyst layer 6
, 6a are attached with a rotating shaft and a drive device (not shown), and can rotate in two forward and reverse directions or in the same direction as shown by the arrow 80 in FIG.

1, 0 to 1, 2 contained in exhaust gas (m) after action denitrification
% CO is oxidized by about 90% by O2 in the exhaust gas at the front stage oxidation catalysts 5a and 5C, and the exhaust gas heated by the heat of oxidation contacts and passes through the rear stage catalysts 5b and 5d. At this time, CO that has not been completely oxidized in the first stage catalysts 5a and 5c is completely oxidized in the second stage oxidation catalysts 5b and 5d.

Moreover, the temperature of the exhaust gas, which has increased in temperature by about 80 to 100 degrees Celsius by removing oxidation heat, is maintained at a temperature of 42°C, for example, which is necessary to desorb extremely small amounts of poisonous substances adsorbed on the post-oxidation catalysts 5b and 5d.
Since the temperature has risen to 0° C. or higher, these poisonous substances are desorbed and purified, the oxidation catalyst activity is regenerated, and the temperature is transferred to the rotary heat exchanger l. In the rotary heat exchanger 1, the exhaust gas (I
) and is dissipated into the atmosphere.

However, over time, the first-stage oxidation catalysts 5a and 5c gradually adsorb poisonous substances and their oxidation performance decreases (deteriorates). On the other hand, since the regeneration of the latter stage oxidation catalysts 5b and 5d is carried out in a short time,
At a stage when the CO oxidation rate of the pre-oxidation catalysts 5a, 5c has decreased to a certain extent, or periodically, the rotary catalyst layers 6, 6a are rotated by half a rotation in the forward or reverse direction by a drive device (not shown) to remove the pre-oxidation catalyst 5a. , 5c are moved to the rear stage of the gas flow, and the rear stage oxidation catalysts 5b and 5d are moved to the front stage of the gas flow.

In other words, the front-stage oxidation catalyst 5a has deteriorated.

5C is moved to the regeneration side, and the post-oxidation catalysts 5b and 5d are moved to the CO oxidation side.

By repeating this process, a high CO oxidation rate can be maintained and stable operation can be continued.

Note that the first stage oxidation catalysts 5a, 5c and the second stage oxidation catalyst 5b,
A CO concentration meter sensor is installed between the oxidation catalyst 5d and the CO concentration to display the CO concentration, and the CO concentration passing through the pre-stage oxidation catalysts 5a and 5c is constantly monitored.If the CO concentration exceeds a certain value, the rotary catalyst layer 6
, 6a are preferably inverted and reproduced.

Example An example of implementing the method of the present invention on sintering exhaust gas will be shown.

Conventionally, the exhaust gas obtained by desulfurizing and denitrating the sintering exhaust gas is CO2.
If the temperature of the exhaust gas entering the oxidation catalyst is not raised to 420°C or higher, the catalyst will deteriorate (see Figure 4), so after heat exchange of the exhaust gas after desulfurization, the exhaust gas was heated in a heating furnace using fuel. According to the method of the present invention, a one-rotation type catalyst layer was installed as shown in FIG. 1, and the exhaust gas temperature after entering the CO oxidation catalyst of the front stage catalysts 5a and 5c was operated at 405°C. As a result, the latter stage catalyst 5b.

The inlet exhaust gas temperature at 5d becomes 485°C, and at the same time
As shown in the figure, the CO oxidation rate of the catalyst placed in the front stage gradually decreased, and after about 2.5 days, the CO oxidation rate decreased to 90%, so the rotary catalyst layer was rotated half a turn, and no deterioration occurred. When the rear stage oxidation catalyst is moved to the front stage (indicated by the square mark in Figure 6), the original catalyst performance (approximately 95% in Figure 6) is immediately restored.
demonstrated. Then, on the 5.2nd day or 7.8th day, etc.C
By reversing the process when the O oxidation rate reached 90%, a high oxidation rate could be maintained continuously.

In addition, CO installed between the front-stage oxidation catalyst and the rear-stage oxidation catalyst
The concentration meter detected CO, but the CO concentration after the post-oxidation catalyst was almost O. This shows that some CO that passed through the first stage oxidation catalyst was oxidized by the second stage oxidation catalyst.

Effects of the Invention The present invention is capable of maintaining a high oxidation rate of carbon oxide by simultaneously carrying out the oxidizing action of carbon oxide and the regeneration of a deteriorated catalyst. It also eliminates the need for CO2 contained in the sintering exhaust gas.
By completely oxidizing the -carbon oxide, the entire amount of oxidation heat from the -carbon oxide can be used to regenerate the deteriorated catalyst, resulting in significant energy savings and reductions in operating costs, as well as significant environmental improvements.

Further, the method of the present invention has the effect that the oxidation catalysts on the upstream side and the downstream side can be reversed to continuously perform the oxidation of exhaust gas and the regeneration of the catalyst, making it unnecessary to replace the catalysts.

[Brief explanation of drawings]

Fig. 1 is a flow sheet of the denitrification and -carbon oxide oxidation process in which the method of the present invention can be suitably carried out, Fig. 2 is a detailed view of the rotary catalyst bed installation, and Fig. 3 is a conventional method of denitrification and -carbon oxide The flow sheet of the oxidation process, Figure 4 shows the exhaust gas temperature and CO
A graph showing the relationship with the oxidation rate, Figure 5 is a flow sheet of another example in which the method of the present invention is applied (detailed diagram of the rotary catalyst layer installation), and Figure 6 shows the change over time in the carbon monoxide oxidation rate and the catalyst It is a graph showing the relationship with layer inversion. 1... Rotary heat exchanger 2... Pressure booster blower 3... Heating furnace 4a, 4b... Denitrification reactor 5a, 5b, 5c, 5d... - Carbon oxide oxidation catalyst 6.
6a...Rotary catalyst layer 7...Duct 8...Arrow (indicates the direction of reversal) Applicant Kawasaki Steel Co., Ltd. Agent Patent attorney Yoshio Kosugi Patent attorney Kazunori Su Fuji Figure 1 Figure 2

Claims (1)

[Claims] l In a method for regenerating a catalyst used for oxidizing carbon monoxide in exhaust gas, a highly active oxidation catalyst is placed on the L flow side of the exhaust gas flow path, and a deteriorated oxidation catalyst is placed on the downstream side thereof. The upstream catalyst oxidizes CO in the exhaust gas, and the downstream catalyst oxidizes the CO remaining in the exhaust gas that has exited the upstream catalyst layer, and the gas regenerates deterioration. A method for regenerating a catalyst. 2. A device is installed that reverses the upstream and downstream oxidation catalysts and swaps their positions, and the upstream and downstream catalysts are reversed periodically or depending on the degree of decline in the CO oxidation rate, thereby reducing the oxidation of exhaust gas and the deterioration of the catalyst. The method for regenerating a catalyst according to claim 1, wherein the regeneration of the catalyst is performed continuously.