JPH0656407A - Sulfur oxides reductor - Google Patents

Abstract

PURPOSE:To enable exact control of the temperature in the moving bed within the optimal temperature range. CONSTITUTION:In a sulfur dioxide reductor in which sulfur dioxide gas and air fed into the column 1 are brought into contact countercurrently with the moving bed 2 formed by the reductant in the column 1 to effect the reduction of the sulfur oxide, a plurality of temperature sensors 7 are arranged vertically in a prescribed interval and a regulator 8 which regulates the amount of the air fed into the reduction column 1 on the basis of values detected from individual sensors 7 weighted largely near the center of the bed 2 and smaller than the center as the values are apart from the center upward or is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sulfur oxide reducing apparatus for reducing sulfur dioxide by bringing it into contact with a reducing agent.

[0002]

2. Description of the Related Art There is a dry desulfurization device as a device for removing sulfur components such as hydrogen sulfide contained in a gas to be treated such as coal gasification gas. This desulfurization device is for removing the sulfur content in the gas by bringing the gas to be treated into contact with a desulfurization agent, and the sulfur dioxide gas generated when the desulfurization agent after the desulfurization treatment is regenerated is subjected to the sulfur oxide reduction device. Reduced and recovered as sulfur.

In the sulfur oxide reducing apparatus, a gas containing sulfurous acid gas is brought into countercurrent contact with a moving bed of a reducing agent containing carbon as a main component, which is formed in a reducing tower, so as to reach a high temperature (about 700 to 900).
It reduces sulfurous acid gas to sulfur gas under (° C).
The optimum value of the reduction reaction temperature depends on the type of the reducing agent, and it is necessary to select a condition in which the conversion rate of sulfurous acid gas is high and the amount of by-products other than elemental sulfur is small. If the reaction between the reducing agent and sulfurous acid gas is performed outside the temperature range of about 700 to 900 ° C,
The reduction reaction proceeds too much, or sulfurous acid gas is not sufficiently reduced.

[0004]

By the way, in the above-mentioned sulfur oxide reducing apparatus, air is supplied together with the gas containing the sulfurous acid gas into the reducing tower, and the calorific value required by the combustion of oxygen and coal in the air. Has been secured. Further, the reducing reaction between the reducing agent and the sulfurous acid gas is likely to occur in the central portion of the moving layer. Therefore, in order to control the temperature in the moving bed within the optimum temperature range,
The flow rate of air supplied into the reduction tower was adjusted by adjusting the valve or the like based on the temperature (measured value) of the central portion of the moving bed.
However, if only the air flow rate is controlled based on the temperature (measured value) of the central portion of the moving layer, the control of the air flow rate will be delayed without taking into consideration, for example, when there is a sharp rise in temperature outside the central portion, In some cases, the temperature in the moving bed cannot be accurately controlled within the optimum temperature range.

Therefore, the present invention has been made in consideration of such circumstances, and an object thereof is to reduce the sulfur oxides, which makes it possible to accurately control the temperature in the moving bed within the optimum temperature range. To provide a device.

[0006]

In order to achieve the above-mentioned object, the present invention supplies sulfur dioxide gas and air into a reducing tower, and countercurrently flows these with a moving bed of a reducing agent formed in the tower. In a sulfur oxide reduction apparatus that reduces sulfurous acid gas by bringing them into contact with each other, a plurality of temperature sensors are arranged in the moving bed of the reduction tower at predetermined intervals in the height direction thereof, and the temperature sensors are obtained from these temperature sensors. Each detected value is weighted with a coefficient that the central portion of the moving bed is large and becomes smaller as it goes up and down from the central portion, and a PID control unit for PID-controlling the air flow rate supplied to the reduction tower based on these values. Is provided.

[0007]

By weighting each detected value obtained from a plurality of temperature sensors provided in the height direction in the moving bed with a coefficient that is large at the center of the moving bed and becomes smaller as it goes up and down from the center. The temperature value in the moving bed, which is measured by the control unit, is measured in consideration of the entire moving bed, but the measurement of the central portion is weighted. Therefore, the control of the flow rate of the air supplied to the reduction tower is mainly performed based on the temperature of the central portion, and even if there is a partial temperature increase outside the central portion, the measured value is affected. It is done based on this. Further, since the air flow rate is adjusted by the PID control, the moving bed temperature fluctuates little and quickly converges to the target value. Therefore, the moving bed temperature can be controlled accurately and smoothly within the optimum temperature range.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a reduction tower formed in a vertical cylindrical shape. From a lock hopper (not shown) provided at the upper part of the reduction tower 1, carbonaceous materials such as anthracite and coke are supplied. The reducing agent is continuously or intermittently supplied into the tower 1 to form a moving layer 2 of the reducing agent that moves in the tower 1 from top to bottom. In addition, unburned components (char) from the bottom of the reduction tower 1
Etc. are discharged.

A gas disperser 3 is disposed below the inside of the reduction tower 1, and a gas conduit 4 for gas containing sulfurous acid gas having a high temperature, for example, 400 ° C., is connected to the gas disperser 3. An air supply pipe 5 is connected to the gas conduit 4 in the vicinity of the reduction tower 1, and a gas containing air and sulfurous acid gas from the air supply pipe 5 is ejected from the gas disperser 3 to the lower side of the moving bed 2 to move inside the moving bed 2. And is brought into countercurrent contact with the reducing agent at high temperature (about 700 to 900 ° C) under high pressure to reduce sulfurous acid gas to sulfur gas. The gas such as the sulfur gas flows out to the gas discharge pipe 6 provided above the reduction tower 1.

Inside the reduction tower 1, a gas disperser 3
A plurality of (six in the illustrated example) temperature sensors 7 are arranged in the upper moving layer 2 at predetermined intervals in the height direction thereof. In addition, in order to measure the temperature distribution in the horizontal direction, it is necessary to install at least three temperature sensors in the horizontal direction when the inner diameter of the reduction tower is 1 m or less.
For those exceeding m, add sensors appropriately. Detection value signals are output from each temperature sensor 7, and these signals are input to the control unit 8.

The control unit 8 multiplies the signal from each temperature sensor 7 by a coefficient weighted according to the location,
The first calculation controller 9 for adding these values to obtain the representative temperature (weighted average temperature) in the moving bed 2 and the representative temperature signal from the controller 9 and the signal of the temperature target value are compared and calculated (PID
Temperature controller 10 for controlling) and a second arithmetic controller 11 for adjusting the signal from the temperature controller 10 in order to prevent the temperature in the moving bed 2 from suddenly rising based on the signals from the temperature sensors 7. And a flow rate detector 12 connected to the air supply pipe 5 and connected to the flow rate controller 14 for generating a control signal to be output to the control valve 13, and the temperature controller 10 performs a second calculation. It is configured to cascade-control the flow rate of air supplied to the reduction tower 1 based on a signal from the controller 11.

The first arithmetic and control unit 9 takes in the signals from the respective temperature sensors 7 and multiplies each measured value (signal) by a coefficient so as to place more weight on the central portion of the moving bed 2 where the reaction occurs most actively. Then, all of these points are added to obtain a representative temperature (weighted average temperature) in the moving bed 2. The coefficient is large as the center of the moving layer 2 is large and becomes smaller as it goes up and down from the center, for example, when there are six sensors 7 (when the coefficients are X _{1 to} X _{6 in} order from the top of the sensor installation place), The two coefficients near the center of the moving bed 2 are X ₃ = X ₄ = 4/14, the two coefficients next closest are X ₂ = X ₅ = 2/14, and the coefficients farther from the center are X ₁ = X ₆ = 1/14. However, X ₁ + X ₂ + X ₃ + X ₄ + X ₅ + X ₆ = 1
And

The temperature controller 10 compares the representative temperature signal from the first arithmetic controller 9 with the signal of the temperature target value (PI).
D control) to generate a flow rate control signal, and the signal is adjusted to the flow rate target value at the start point.
The coefficient varies depending on the size of the device, but the temperature setting value is 730 ℃ (anthracite), proportional constant (P):
2 to 2.5 (proportional band 40 to 50%), integration time (I): about 10 seconds.

The second arithmetic controller 11 multiplies the signal (set value) from the temperature controller 10 by a coefficient x and outputs it to the flow rate controller 14. Specifically, each of the temperature sensors described above is used. Based on a plurality of signals from 7, the respective temperature change rates (temperature change (ΔTs) within unit time) are calculated, and when the maximum value among them exceeds a predetermined value, for example, as shown in FIG. The coefficient x is set so as to reduce the flow rate setting value with various characteristics to limit the air flow. For example, the change rate control start point: 6 ° C./sec, the proportional constant: −20 to −30 ( Rate of change (° C./second).

Next, the operation of this embodiment will be described.

As shown in FIG. 1, the gas containing the sulfurous acid gas is jetted from the gas disperser 3 into the reduction tower 1 through the gas conduit 4 together with the air from the air supply pipe 5 to flow in the moving bed 2. To rise. As a result, the reducing agent is countercurrently contacted with a gas such as sulfurous acid gas, and the sulfurous acid gas is reduced to sulfur gas under high temperature (about 700 to 900 ° C.) and high pressure (SO ₂ + C → 1/2).
S ₂ + CO ₂ ). The gas containing the sulfur gas flows out to the gas discharge pipe 6, and the sulfur gas is recovered as liquid sulfur through a sulfur condenser (not shown) and the like.

The temperature at which sulfurous acid gas is reduced varies depending on the type of reducing agent, but it is necessary to select conditions in which the conversion rate of sulfurous acid gas is high and by-products other than elemental sulfur are small (for example, at a temperature of about 750 to 800 ° C.). To the temperature range). Since the temperature of the moving bed 2 cannot be maintained at the optimum level only by the reduction reaction, the combustion reaction of oxygen in the supplied air and coal (C
Secure the required amount of heat generation by + O ₂ → CO ₂ ). Therefore, by appropriately adjusting the control valve 13 of the air supply pipe 5 to control the flow rate of the air supplied to the reduction tower 1, the moving bed 2
It is possible to control the temperature within the optimum temperature range, and this control is performed by the control unit 8.

The control unit 8 weights the output from each temperature sensor 7 arranged in the moving layer 2 by a predetermined coefficient (coefficients of X _{1 to} X ₆ ) and weights them, and adds them. Moving layer 2
The representative temperature (weighted average temperature) is calculated and the temperature target value is compared and calculated (PID control), and the flow rate controller 14 outputs a control signal to the control valve 13 based on this.

That is, when the representative temperature exceeds the optimum temperature range, the control valve 13 is throttled. On the contrary, when the representative temperature is below the optimum temperature range, the control valve 13 is opened to optimize the representative temperature. It is controlled to be within the temperature range. Here, the air flow rate is controlled based on the representative temperature because the reduction reaction of the sulfurous acid gas and the reducing agent is likely to occur in the central portion of the moving layer 2. 2 When the temperature below is low, the temperature in the moving bed 2 rises from the bottom to the top, which causes a delay in the adjustment of the air flow rate. This is because the temperature difference with the central portion of the moving layer 2 where the reduction reaction easily occurs may become large. Therefore,
A plurality of temperature sensors 7 provided in the moving bed 2 in the height direction
By weighting each detected value obtained from the moving layer 2 with a coefficient that is large in the central part of the moving layer 2 and becomes smaller as it goes away from the central part in the vertical direction, the control section 8 considers the moving layer 2 as a whole and produces the most reaction. The representative temperature weighted in the central portion of the moving layer 2 that frequently occurs is required.

As a result, since the control of the air flow rate by the control unit 8 is mainly performed based on the temperature value of the central portion where the reduction reaction easily occurs, the temperature in the moving bed 2 is controlled within the temperature range where the reduction reaction easily occurs. can do. Further, even if there is a partial temperature rise outside the central portion, the measured value is affected, and the air flow rate to the reduction tower 1 is appropriately reduced based on this, so that a local temperature rise is prevented. Will be. Further, since the PID control performs the arithmetic control for comparing the representative temperature and the temperature target value to generate the flow rate control signal, the flow rate set value changes according to the situation in the moving bed 2, so that the control signal changes rapidly. This prevents the temperature of the moving bed 2 from fluctuating little and quickly converges to the target value.
Therefore, the temperature of the moving bed 2 can be controlled accurately and smoothly within the optimum temperature range.

In addition, the control unit 8 includes a second arithmetic controller 11
Is provided, the signal (set value) from the temperature controller 10 is multiplied by a coefficient x according to the temperature in the moving bed 2,
This is output to the flow rate controller 14. For the coefficient x, the rate of change (temperature change (ΔTs) within a unit time) of each of the plurality of signals from the temperature sensors 7 is calculated, and the maximum value thereof is a predetermined value (for example, 6 ° C./second). ) In the following cases, it is set to 1, and when it exceeds the predetermined value, it is set to less than 1. Therefore, when the temperature in the moving bed 2 suddenly rises as shown in FIG. 3 (a) due to a rapid increase in the SO ₂ concentration in the inlet gas of the reduction tower or a temporary mixture of O ₂ (ΔTs is 6 ° C.
3 / b), even if the instantaneous value (measured value) of the temperature is within the optimum temperature range (below the target value), the output signal to the flow rate controller 14 is as shown in FIG. 3 (b). The air flow rate to the reduction tower 1 is adjusted to be temporarily reduced. As a result, the rapid reaction settles down in a short time, the temperature rise stops, and the temperature of the moving bed 2 does not rise significantly beyond the optimum temperature range. When adjusting the air flow rate after the moving bed temperature exceeds the optimum temperature range, if the temperature rises rapidly when the temperature exceeds the optimum temperature range, the temperature rises to some extent when adjusting the air flow rate. Therefore, the moving bed temperature may greatly exceed the optimum temperature range. In particular, if proportional control alone is used, the air flow rate decreases slowly, and more air is supplied than necessary when the reducing agent is reacting (combusting) rapidly, so the temperature rise does not stop immediately and remains constant for a certain period of time. Since the temperature continues to rise, there is a danger that it will greatly exceed the optimum temperature range and become dangerous.

Then, the temperature change (ΔTs) in the moving layer 2
Becomes less than a predetermined value, the coefficient x becomes 1 and the temperature controller 1
The signal (setting value) from 0 is directly output to the flow rate controller 14.

Therefore, the temperature change (ΔTs) in the moving bed 2
When the temperature tends to rise suddenly, the air flow rate is temporarily reduced, and even if the temperature in the moving bed 2 suddenly rises, it is immediately dealt with. It does not rise significantly beyond the range.

[0025]

In summary, according to the present invention, the detected value obtained from a plurality of temperature sensors arranged in the moving bed is large at the center of the moving bed and becomes smaller as it goes up and down from the center. Since the coefficients are weighted and the flow rate of the air supplied to the reduction tower is PID-controlled based on these values, the excellent effect that the temperature in the moving bed can be accurately and smoothly controlled within the optimum temperature range is exhibited. .

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a temperature change rate and a coefficient.

FIG. 3A is a diagram showing a relationship between time and temperature,
(B) is a figure which shows the relationship between time and a control signal.

[Explanation of symbols]

 1 reduction tower 2 moving bed 7 temperature sensor 8 controller

Claims (1)

[Claims] 1. A sulfur oxide reduction apparatus for reducing sulfurous acid gas by supplying sulfurous acid gas and air into a reducing tower and bringing them into countercurrent contact with a moving bed of a reducing agent formed in the tower. In the moving bed of the reduction tower, a plurality of temperature sensors are arranged at predetermined intervals in the height direction, and the detected value obtained from these temperature sensors has a large central portion of the moving bed. The sulfur oxide reduction apparatus is characterized in that a control unit is provided which weights a coefficient that becomes smaller as the distance from above and below increases, and PID-controls the flow rate of the air supplied to the reduction tower based on these values.