JPH025459B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a desulfurization agent used in a dry flue gas desulfurization device from coal.

To produce a desulfurizing agent from coal, in order to homogenize the desulfurizing agent, the coal is finely pulverized, then molded (granulated), and carbonized at a temperature of 500°C to 800°C. The carbonized coal is then exposed to oxidizing gases (O ₂ , CO ₂ , SO ₂ ,
_H2O , _Cl2 , etc.) to produce a desulfurizing agent with adsorption activity for _SO2 . In addition, various measures have been proposed to reduce the cost of producing a desulfurizing agent, one of which is to directly crush coal without pulverizing it, carbonize and activate the coal particles of an appropriate particle size, and use them as a desulfurizing agent. etc. In either case, the carbonization operation is an important heat treatment step for promoting carbon crystallization of coal. The carbonized coal is then heated to a temperature of 900℃ to 1000℃.
It is reacted with an oxidizing gas at ℃ to form a desulfurizing agent. Usually, water vapor is often used as the oxidizing gas.

In this way, when producing a desulfurization agent, carbonization and activation steps were essential. As mentioned above, carbonization,
Since the activation operation involves high-temperature treatment, equipment costs and utility costs are high, which increases the cost of producing a desulfurizing agent.

In addition, the desulfurizing agent obtained by this production method generally has a low strength, and further has the disadvantage that the rate of performance deterioration increases due to repeated operations of adsorption and thermal desorption/regeneration.

An object of the present invention is to provide a method for producing a desulfurizing agent that has high strength and exhibits a low rate of performance deterioration even after repeated adsorption and thermal desorption regeneration at a low cost.

The present invention brings coal into direct contact with a gas containing oxygen at a temperature of 400°C or less to promote the coal's specific surface area and pore expansion, and after that, the effective pores contained in petroleum-based heavy oil are released into the pores. 700℃ after attaching metal components
By heat-treating at the above temperature, the residual volatile content in the coal is reduced, and the coal is used as a desulfurization agent.

Therefore, the present invention does not require a steam activation step at high temperature. In addition, the desulfurizing agent produced according to the present invention is brought into contact with combustion exhaust gas containing SO ₂ to thermally desorb and regenerate the desulfurizing agent that has adsorbed SO ₂ , and when these operations are repeated, the adsorption performance usually deteriorates. It has become clear that the amount of desulfurization agent is reduced compared to that produced by the desulfurization agent production method. This is because when SO ₂ is adsorbed to the desulfurization agent, the metal impregnated in the pores of the desulfurization agent acts as a catalyst for the oxidation reaction of SO ₂ .

In addition, when manufacturing desulfurization agents using a normal method, the carbon crystallization of carbonized coal is promoted by carbonization, and then the steam activation reaction is promoted, whereas in the present invention, pores are developed by low-temperature oxidation treatment. It was found that since heat treatment is then performed, the carbon crystal structure becomes denser and the strength of the desulfurizing agent and the filling strength are increased.

In the present invention, methods for impregnating effective metal components into the pores of low-temperature oxidized coal include a method in which petroleum-based heavy oil is impregnated into coal that has been subjected to low-temperature oxidation treatment; There is a method in which low-temperature oxidized coal is impregnated into a water slurry containing ash generated by combustion. Here, petroleum-based heavy oil includes coal tar, crude oil, and direct and indirect residual oil in addition to heavy oil. That is, these petroleum-based heavy oils can be effectively used in the present invention because they contain metal components that are effective as catalysts for the oxidation reaction of SO ₂ .

Hereinafter, the specific process of the present invention will be explained with reference to FIGS. 1 and 2.

FIG. 1 shows an example of the process of the first invention of the present invention. In FIG. 1, raw coal 1 for desulfurization agent is coarsely crushed by a crusher 100, and coal 3 of an appropriate particle size is crushed from a flow 2 by a classifier 101.
get. Pulverized coal 4 can be used as boiler fuel. The classified coal 3 is sent to a low-temperature oxidation treatment device 102
The pores of the coal are developed by partially oxidizing the coal with the oxygen-containing gas 4. In low-temperature oxidation treatment, when the processing temperature exceeds 400℃, the oxidation reaction becomes rapid and difficult to control.
It is preferable to process at temperatures below .degree. The low-temperature treated coal 5 is sent to a cooler 103 to be cooled. The cooling mediums 6 and 7 can be indirectly cooled using air or the like. The cooled low-temperature oxidation-treated coal 8 is then sent to a tank 104 as a slurry 9 of ash and water generated by burning petroleum-based heavy oil such as heavy oil or crude oil, to a tank 104, where it is subjected to low-temperature oxidation treatment. Add 8 coals. The low-temperature oxidation treated coal that has been immersed for a certain period of time is removed from the stream 10 and solid-liquid separator 106
send to In the slurry tank 105, the ash content 10 and water 11 are adjusted to obtain a water slurry 9. In the solid-liquid separator 106, the separated liquid is transferred from the stream 12 to the slurry tank 1.
05 and the solids (coal) is sent from stream 13 to moisture dryer 107. In the dryer 107, hot air 14,
It is efficient to directly contact and dry the material by using the method No. 15. It is efficient to use the hot air 14 by dividing a part of the processing gas 5 of the low-temperature oxidation processing apparatus 102. Moreover, even if some moisture remains in the coal, it is heat-treated in the carbonization furnace 108 in the next step, so there is no need for particularly strict drying in the moisture dryer 107. The dried coal 16 is then sent to a carbonization furnace 106 for carbonization. Here, the carbonization temperature is 700°C or higher.
FIG. 3 shows the relationship between carbonization temperature, MS hardness, and SO ₂ adsorption capacity. If the carbonization temperature is lower than 700°C, the residual volatile matter in the carbonization coal will be 5 to 8%, and sufficient SO ₂ adsorption performance as a desulfurization agent cannot be obtained. However, when the carbonization temperature exceeds 1000°C, the carbon crystals become dense, and although the hardness of the desulfurizing agent improves, the SO ₂ adsorption capacity tends to decrease significantly. Therefore, the carbonization temperature is preferably 700 to 1000°C, but preferably 800 to 1000°C in order to make the carbonization proceed more smoothly. Further, in the carbonization furnace 108, it is particularly preferable to conduct the carbonization in an inert gas atmosphere, but considering economic cost, the carbonization is carried out in direct contact with the combustion exhaust gas to proceed with an oxidation reaction with moisture, H ₂ O, etc. in the combustion gas. is desirable.

As the heat source of the carbonization furnace 108, it is effective to send the combustion exhaust gas 17 from the combustor 109 to the carbonization furnace 108, and carbonize it by directly contacting the coal. Combustor 10
9 is introduced through stream 19, which can be a solid, liquid, or gaseous fuel, and here preferably a near stoichiometric air volume is delivered through stream 20 to remove the oxygen in the flue gas 17. It is preferable to reduce the amount as much as possible from the viewpoint of improving the yield and strength of the final product. Further, in the combustion furnace 109, oxygen in the combustion exhaust gas 17 can be reduced by burning under conditions close to an incomplete combustion state.

Since the processing gas 21 of the carbonization furnace 108 generates flammable gas and a portion of tar, it is divided into streams 22 and 23, and a portion is used as fuel for the combustion furnace 109 and a portion as heating gas for the low-temperature oxidation treatment device 102. can. Carbonized coal 24 is then sent to cooler 110 where it is cooled by indirect heat exchange with air from stream 25. The cooling medium of the cooler 110 can also be indirectly water. When air is used, the air is heated and is divided into streams 26 and 27, and stream 26 joins with supplementary air 28 to become stream 29 and further stream 23.
Flow 4 is formed by combining with the carbonization process gas from Flow 4. Since the low-temperature oxidation processing gas is a low-calorie gas, a portion of the gas is sent to the combustion furnace 109 from the stream 18 via the stream 30, and a portion of the stream 31 is discharged from the system for processing. Also,
The low-temperature oxidation gas in the stream 31 is used as a part of the heat source in the dryer 107, and then separately sent to a combustion furnace (low-calorie gas combustion furnace) for treatment, and then exhausted to the outside of the system. The air source for combustion furnace 109 is also regulated by heated air from stream 27 and make-up air from stream 32. The cooled final product desulfurization agent is obtained from stream 33.

FIG. 2 shows an example of the process of the second invention of the present invention.

The parts in FIG. 2 that differ from the process shown in FIG. 1 are the tank 104 and slurry tank 1 in FIG.
05 solid-liquid separator 106 and moisture dryer 107, an impregnation tank 120 and a viscosity adjustment tank 121 are provided. Therefore, in Figure 2,
Components that are the same as those in FIG. 1 are indicated by the same reference numerals.

The coal 8 cooled by the cooler 103 is transferred to the impregnation tank 12
0 and impregnated with petroleum-based heavy oil.
The amount of heavy oil impregnated is preferably about 10 to 20% of the weight of the coal. Since the heavy oil 35 has a high viscosity, the viscosity is adjusted in a viscosity adjusting tank 121, and then introduced from a flow 36 into an impregnating tank 120, where it is impregnated with coal that has been subjected to low-temperature oxidation treatment. The coal 37 impregnated with heavy oil is then sent to a carbonization furnace 108 and carbonized. Carbonization furnace 108
The heat source is brought into direct contact with the combustion exhaust gas 17 from the combustion furnace 109 to perform carbonization. Carbonized gas generated by partial pyrolysis of heavy oil and carbonized coal becomes gas stream 38, most of which is stream 39.
The fuel enters the combustion furnace 109 and is burned there.
The branched stream 23 can also be used as a heating source for low temperature oxidation treatment. Burnt coal flows from stream 40 to cooler 1
10 to obtain a desulfurizing agent 33 as a final product.

In the process shown in FIG. 2, the temperature conditions in the low-temperature oxidation treatment apparatus 102 and the combustion furnace 108 are the same as in the process shown in FIG.

In addition, when impregnating coal with petroleum-based heavy oil, a surfactant or the like is added to the heavy oil or the heavy oil is heated to lower the viscosity of the heavy oil so that the heavy oil becomes more viscous than the coal. It is also possible to make it easier to penetrate into the pores.

Next, examples of the present invention will be described by showing specific conditions.

FIG. 4 shows the treatment time and the rate of increase in specific surface area when Australian coal is crushed, the coal is classified into 5-7 mmφ, and the coal is subjected to low-temperature oxidation treatment. Processing temperature 320
A case where the treatment temperature was kept constant at 250°C and a gas with an oxygen concentration of 3% was used, and a case where the treatment was performed with a gas with an oxygen concentration of 8% at a constant temperature of 250°C. In either case, the specific surface area of coal increases with treatment time.

Figure 3 also shows that the higher the treatment temperature, the greater the specific surface area of coal.
If the temperature exceeds ℃, it becomes difficult to control the oxidation reaction.

Next, we analyzed the composition of the ash generated in the heavy oil-fired boiler (the ash collected by the electrostatic precipitator) and found that it contained 1.2% H ₂ O, 31.7% (NH ₄ ) ₂ SO ₄ , and 31.7% carbon.
The main components in the ash are Na ₂ O 1.79%, SO ₃ 8.7%, V ₂ O ₅ 1.51%,
_SiO2 0.32%, CaO0.17%, MgO0.17%,
The contents were 0.55% Al ₂ O ₃ , 0.94% Fe ₂ O ₃ , and 0.78% NiO. Add 10 parts of this ash to 100 parts of water, mix and stir to form a slurry, add the low-temperature oxidized coal at a weight ratio of 20 parts to 100 parts of the slurry, and take out the coal after soaking for 5 hours. After drying the coal in air at a temperature of 110°C for 2 hours, it was heat-treated at a temperature of 900°C for 1 hour in an N ₂ gas atmosphere, and then cooled to room temperature in an N ₂ gas atmosphere. It is shown in Figure 5A.

In addition, heavy oil is added to the aforementioned low-temperature oxidation-treated coal at a high temperature.
The temperature was raised to 120°C, 15 parts by weight was sprayed and impregnated with respect to 100 parts of the low-temperature oxidation treated coal, and it was heated at a temperature of 950°C for 1 hour in N ₂ gas, and then cooled in N ₂ gas. The desulfurizing agent obtained is shown in Figure 5B.

On the other hand, Fig. 5C shows the Australian coal in _N2 gas.
Carbonization was carried out at 700°C for one hour, and after cooling, steam activation (steam 15%) was performed at a temperature of 900°C, followed by cooling to obtain a desulfurizing agent.

FIG. 5 shows the results of determining the performance deterioration rate of each desulfurizing agent when adsorption and thermal desorption regeneration were repeated. Cumulative SO ₂ during repeated adsorption/thermal desorption/regeneration
It is expressed as a ratio between the adsorption amount and the initial SO ₂ adsorption amount of the desulfurization agent before repeated adsorption/thermal desorption/regeneration.

Adsorption test is SO ₂ 20000ppm, H ₂ O 10%, O ₂ 6%,
The thermal desorption test is the amount of SO ₂ adsorbed when a simulated combustion exhaust gas containing 82% N ₂ is adsorbed at a temperature of 100℃ for 3 hours.
Desorption was performed in _N2 gas at a constant temperature of 450°C for 45 minutes. The repetition of adsorption/thermal desorption/regeneration is the repetition of the above-mentioned operations.

It is clear that the performance deterioration rate due to repeated adsorption/thermal desorption regeneration is smaller than that of desulfurization agent C for both desulfurization agents A and B of the present invention, and that the desulfurization agent produced by the manufacturing method of desulfurization agent A is particularly superior in that the performance deterioration rate is small.

Further, the strength of the desulfurizing agent was evaluated by measuring the MS hardness (micro strength method) of the desulfurizing agent.

Figure 6 shows the cumulative amount of repeated adsorption/thermal desorption/regeneration.
It is shown as a ratio between the SO ₂ adsorption amount and the MS hardness of each desulfurization agent in the initial state. The hardness of the desulfurizing agent after repeated adsorption/thermal desorption/regeneration increases in the order of desulfurizing agent B > desulfurizing agent A > desulfurizing agent C, and compared to the desulfurizing agent produced by steam activation, the hardness of the desulfurizing agent B, which is produced by the production method of the present invention, is higher than that of the desulfurizing agent produced by steam activation. It became clear that A was also superior in terms of strength.

In the process shown in Figures 1 and 2, after ash or heavy oil is impregnated with low-temperature oxidized coal, the drying, carbonization, and cooling steps are performed in batches. It is also possible to carry out each of these steps in a moving bed type single column system. Furthermore, the present invention has the advantage that conventional steam activation operations are not required. Here, the steam activation conditions are generally such that 15% steam is applied to the carbonized coal at a temperature of 900°C. On the other hand, in the present invention, low-temperature oxidation treatment (below 400° C.) and contact between oxygen-containing gas and coal are extremely effective in terms of thermal energy.

As described above, according to the present invention, there is no need for a steam activation operation, so the cost for producing a desulfurizing agent can be reduced.
Coal that has undergone low-temperature oxidation treatment is impregnated with petroleum-based heavy oil or active ingredients contained in the ash obtained by burning it, and its strength is increased simply by heat treatment, and SO ₂ can be removed by repeating adsorption and thermal desorption regeneration. It is possible to produce a desulfurizing agent with less deterioration in adsorption performance.

[Brief explanation of drawings]

Figure 1 is a flow sheet showing an example of the manufacturing process of the first invention, Figure 2 is a flow sheet showing an example of the manufacturing process of the second invention, and Figure 3 is a diagram showing carbonization temperature and
Diagram showing the relationship between MS hardness and SO ₂ adsorption capacity, 4th
The figure shows the effect of increasing the specific surface area of coal by low-temperature oxidation treatment, and Figure 5 shows the deterioration of the SO ₂ adsorption performance of the desulfurization agent due to repeated adsorption and thermal desorption regeneration.
FIG. 6 is a diagram showing the change in MS hardness of the desulfurizing agent due to repeated adsorption and thermal desorption regeneration. 100...Crushing machine, 101...Classifier, 102
...Low temperature oxidation treatment equipment, 103...Cooler, 10
4...Tank, 105...Slurry tank, 106...
...Solid-liquid separator, 107...Moisture dryer, 108...
... Carbonization furnace, 109 ... Combustion furnace, 110 ... Cooler, 120 ... Impregnation tank, 121 ... Viscosity adjustment tank.

Claims (1)

[Claims] 1. Gas containing oxygen and coal are brought into direct contact at a temperature of 400°C or less, and then the coal is immersed in a slurry containing ash generated by burning petroleum-based heavy oil. , and then heat-treating the solid-liquid separated coal at a temperature of 700°C or higher. 2. It is characterized by bringing oxygen-containing gas and coal into direct contact at a temperature of 400°C or lower, then impregnating the coal with petroleum-based heavy oil, and then heat-treating at a temperature of 700°C or higher. A method for producing a desulfurizing agent.