JPH0678529B2 - Method and apparatus for coal gasification - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a coal gasification method and apparatus for supplying coal into a high temperature furnace together with air and oxygen and converting it into fuel gas.

[Background of the Invention]

In recent years, in order to diversify energy and effectively utilize coal, a technique for supplying coal with oxygen, steam, air or a mixture thereof into a high temperature furnace to gasify the coal has been developed. The coal gasifier uses coal with a large particle size, a fixed bed method in which the coal bed is fixed, fine-grained coal is used, a fluidized bed method in which coal particles flow, and a spouted bed using pulverized coal There are methods, etc. In a gasification furnace using any of these methods, it is possible to obtain a gas having a uniform composition without lowering the gasification efficiency.
The operating conditions are constantly controlled.

The most important factor affecting the gasification temperature and the gasification efficiency in a coal gasifier is the ratio of the supply of the gasifying agent, which is oxygen, air, steam or a mixture thereof, to the coal supply, The ratio needs to be controlled. And the gasification performance of coal is strongly influenced by the properties of coal. However, as described in "Current Status of Fisher-Tropsch Synthetic Technology in South Africa" by Taihyo Kouto in the September 1977 issue of Chemical Industry, coal is not only due to different origins, but even in the same coal mine. , Often different in nature. Therefore, in gasifying coal, it is necessary to control operating conditions commensurate with the type of coal. Therefore, conventionally, the properties of coal are measured at regular intervals during operation of the gasifier, and the operating conditions are changed to suit the properties of the coal measured, and control is performed so that the best operating condition is always maintained. It was However, this method has the disadvantage that it takes a lot of time for the analysis of coal and it is not possible to make an immediate correction for fluctuations in gasification performance. Further, the coal supply amount is measured by detecting the weight change of the coal hopper, the pressure difference of the coal supply pipe, the rotation speed of the coal supply machine, and the like. However, in the present situation, these are continuously
Moreover, it has not yet been measured with good performance, and there is a drawback that it takes time to detect and control changes in the coal supply amount.

[Object of the Invention]

An object of the present invention is to provide a coal gasification method and an apparatus therefor capable of rapidly obtaining and maintaining optimum gasification conditions when the coal type or the coal supply amount changes.

[Outline of Invention]

FIG. 5 shows the relationship between the oxygen ratio λ (the weight ratio of the oxygen supply amount and the coal supply amount) and the gasification temperature, the produced gas concentration, and the gasification efficiency.

As is clear from FIG. 5, the gasifier temperature rises as the oxygen ratio increases. The gas composition of hydrogen, carbon monoxide, and carbon dioxide, which are typical generated gases, is
While the oxygen ratio λ is small, there is no great change with increasing oxygen ratio. However, when the oxygen ratio λ exceeds a certain value, hydrogen and carbon monoxide decrease and carbon dioxide increases. This is for the following reason.

The gasification efficiency includes a carbon gasification rate and a cold gas efficiency, each of which is defined by the following equation.

The carbon gasification rate ηc increases as the oxygen ratio λ increases. On the other hand, the cold gas efficiency ηg has the maximum value with respect to the oxygen ratio λ. The reason for having such gasification characteristics is as follows.

The following reactions occur in the gasification furnace.

First, under the condition that the oxygen ratio λ is small, the coal (C), combustible gas, and CO ₂ and H ₂ O are produced by the thermal decomposition reaction of coal represented by the formula (3). The chaier and combustible gas react with oxygen, and H ₂ O, CO according to the equations (4), (5) and (6)
Generates ₂ . Then, under the condition of low oxygen, unreacted cha remains. The generated H ₂ O and CO ₂ react with each other according to the equations (7) and (8) to produce CO and H ₂ . Among these, the combustion reactions of the equations (4) to (6) are (7) and (8)
The gasification reaction progresses much faster than the gasification reaction of the equation, and the overall reaction is governed by the progress of the equations (7) and (8).

As shown in FIG. 5, when the oxygen ratio λ is small, the temperature is low and the reactions of the equations (7) and (8) are slow, so that unreacted chains remain and the carbon gasification rate tends to be low. However, the temperature rises as the oxygen ratio λ increases, and the amounts of H ₂ O and CO ₂ produced by the equations (4) to (6) also increase.
For this reason, the reactions of equations (7) and (8) become faster, and the carbon gasification rate increases.

On the other hand, the composition of the generated gas is the amount of H ₂ O and CO ₂ generated by the formulas (4) to (6) and the amount of these gases consumed by the formulas (7) and (8). It depends on the ratio of the amount of CO, H ₂ produced. When the oxygen ratio λ increases, (4)-
The amount of H ₂ O, CO ₂ produced by the equation (6) increases. Further, twice the amount of gas (CO + H ₂ or 2CO) is generated with respect to H ₂ O or CO ₂ consumed by the equations (7) and (8). The ratio of the amounts of CO and H ₂ produced at this time is constant regardless of the oxygen ratio, because it follows the equations (7) and (8). Therefore, the total gas composition is (7), (8) from the equations (4) to (6).
When the equation becomes dominant and the oxygen ratio λ is small, the oxygen ratio λ
There is no big change to.

As the oxygen ratio λ increases, as described above, the carbon gasification rate increases and the unreacted charge decreases. Therefore, excess oxygen is generated by the formulas (7) and (8).
It reacts with O and H ₂ to produce H ₂ O and CO ₂ according to the equations (4) to (6). Therefore, the calorific value of the gas decreases, and the cold gas efficiency ηg decreases.

Since the purpose of the gasification furnace is to generate the largest amount of useful gas, it is preferable to operate under conditions that maximize the cold gas efficiency ηg. According to FIG. 5, the composition of the produced gas changes at the optimum oxygen ratio λ. This volume fraction γcc of CO and CO ₂ in the product gas, or by examining the change to oxygen ratio of the volume fraction γhc of H ₂ and CO _2, it becomes more clear.

FIG. 6 shows the relationship, and there is almost no change in the oxygen ratio of γcc and γhc until the cold gas efficiency ηg reaches the maximum. However, when the cold gas efficiency ηg exceeds the maximum, γcc and γhc decrease sharply. This phenomenon, as shown in FIG. 7, shows a similar identification even when the type of coal changes.

The oxygen ratio λ that maximizes the cold gas efficiency ηg differs depending on the type of coal for the following reason.

When the type of coal is different, the ratio of elements such as carbon C and hydrogen H in the coal is different. Then, in order to maximize the cold gas efficiency ηg, it is enough to convert as much carbon as CO,
The amount of oxygen required at this time was calculated by combining equations (4) and (7). It can be inferred from the reaction formula of That is, the oxygen ratio that maximizes ηg increases as the amount of carbon C increases. However, during the gasification reaction, heat generated by equation (3)
There is a thermal decomposition reaction in which CO, H ₂ , CO ₂ and H ₂ O are generated. At this time, some of the carbon in the coal is bound to oxygen in the coal, and some of the hydrogen is released as H ₂ gas, and the remaining carbon and hydrogen are reacted by the reaction of formulas (4) to (5). Take part in. Therefore, more accurately, coal with more C / O or C / H has η
The oxygen ratio that maximizes g is large.

From the above results, by monitoring γcc and λhc, it is possible to know the changes in the oxygen ratio and coal type, and it is possible to operate the gasification furnace under the best conditions at all times.

The present invention has been made on the basis of the above findings.
The concentration ratio of carbon monoxide and carbon dioxide or the concentration ratio of hydrogen gas and carbon dioxide generated as the invention of the above is calculated multiple times, and the absolute value of the difference between the concentration ratio obtained this time and the concentration ratio obtained last time is predetermined. It is configured such that the supply amount of the gasifying agent is increased or decreased depending on whether the value is less than or equal to the above value, and the optimum gasification efficiency can be maintained.

A second aspect of the present invention detects whether or not the ash content in the gasification furnace is melted, and when the ash content is not melted, the gasifying agent supply amount is increased to melt the ash content. While maintaining the molten state, the same operation as in the first aspect of the invention is performed.

In a third aspect of the present invention, in order to realize the above gasification method, a first temperature sensor and a second temperature sensor for detecting the temperatures of the wall surfaces of the gasification chamber and the slag discharge port are provided, and in the generated gas. A concentration detector for detecting concentration components of carbon monoxide, carbon dioxide, and hydrogen is provided, and when the temperature difference detected between the first temperature sensor and the second temperature sensor is a predetermined value or more, While increasing the supply amount of the agent to make the temperature difference less than the predetermined temperature difference, the concentration ratio of carbon monoxide and carbon dioxide or the concentration ratio of hydrogen gas and carbon dioxide based on the component concentration obtained by the concentration detector. The controller is provided to control the supply amount of the gasifying agent by determining the concentration ratio a plurality of times and determining the magnitude of the change in the concentration ratio.

Example of Invention

Preferred embodiments of a coal gasification method and a coal gasification furnace according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a detailed view showing an embodiment of a gasification furnace body according to the present invention.

In FIG. 1, the inside of the gasification furnace main body 10 is a gasification chamber 12
A lower-stage coal burner 14 having an open tip is attached to the lower part of the gasification chamber 12, and an upper-stage coal burner 16 is attached above it. Each coal burner
A pulverized coal supply pipe 18 and a gasifying agent supply pipe 20 are connected to 14 and 16, respectively.

The gasification chamber 12 has a gasification chamber 21 for discharging the coal ash 21.
A slag cooling chamber 26 in which cooling water 24 is stored through a slag discharge port 22 having a diameter smaller than that of the gasification chamber 12 formed at the lower end of the
Is in communication with. Meanwhile, the upper-stage coal burner in the gasification chamber 12
A temperature sensor T ₁ is provided at a position approximately the same height as 16 and at a position a certain distance from the furnace wall toward the center of the furnace. Further, a temperature sensor T ₂ is provided on the wall surface that is almost the same height as the lower coal burner 14, and the slag discharge port 22
A temperature detector T ₃ is also provided at the lower end of the.

As shown in FIG. 2, a produced gas outlet pipe 30 is connected to the produced gas discharge port 28 formed in the upper portion of the gasification furnace main body 10. A dust collector 32 and a desulfurizer 34 are connected to the generated gas outlet pipe 30, and the dust collector 32 and the desulfurizer 34 are connected.
A gas analyzer 36 is inserted between and. The dust collector 32 removes the dust 39 in the produced gas, and the desulfurization device 34 desulfurizes the produced gas that has passed through the dust collector 32 to produce purified gas 38 such as CO, H ₂ , and CH _4. .

The pulverized coal supply pipe 18 is connected to the hopper through the pulverized coal transportation pipe 40.
The pulverized coal conveyed to 42 is adapted to be supplied in a predetermined amount by a pulverized coal supply device 44, and a coal conveying gas pipe 48 having a sluice valve 46 produces a coal conveying gas such as N _2. Supplied.

The control device 52 that controls the flow rate adjusting valve 50 and the pulverized coal supply device 44 provided in the gasifying agent supply pipe 20 includes a gas analyzer 36.
And the signals of the temperature detectors T ₁ , T ₂ , T ₃ are input. Also, at the bottom of the gasification furnace main body 10, a slag cooling chamber
A slag hopper 54 communicating with 26 is provided, and the molten slag 56 is discharged through the slag hopper 54.

The operation of the embodiment configured as described above is as follows.

The control device 52 controls the pulverized coal supply device 44 and the flow rate adjusting valve 50, and supplies the pulverized coal to the lower coal burner 14 and the upper coal burner 16 via the pulverized coal supply pipe 18 and the gasifying agent supply pipe 20. And a gasifying agent. Part of the pulverized coal supplied to the coal burners 14 and 16 is combusted, enters the gasification chamber 12, and is gasified by the reactions shown in the above formulas (3) to (9).
The generated gas generated in the gasification chamber 12 is guided to a dust collector 32 such as a cyclone by a generated gas outlet pipe 30, and dust 39 is collected and removed, and then desulfurized by a desulfurizer 34 to produce a purified gas. 38.

On the other hand, in the gasification chamber 12, the temperature is controlled to be equal to or higher than the temperature at which the coal ash 21 melts, and the melted coal ash (slag) 21 adheres to the furnace wall and flows down. Then, the coal ash 21 is discharged from the slag discharge port 22.
Through which it falls into the cooling water in the slag cooling chamber 26 and is rapidly cooled. The rapidly cooled coal ash 21 is stored in the slag hopper 54 and then periodically discharged as the molten slag 56.

The supply control of the pulverized coal and the gasifying agent performed by the control device 52 is performed as shown in FIG. First, the controller 52
As shown in step 60, takes in the concentration of the gas component gas analyzer 36 is measured at a certain time .theta.i, determining the ratio γcc or ratio γhc of H ₂ and CO _2, the CO and CO ₂ proceeds to step 62 . Then, the controller 52 proceeds to step 64, compares the .gamma.i _-1 measured calculated last time .theta.i _-1 and calculated this time .gamma.i, | value ε which is determined in advance | γi _-1 -γi Determine if it is greater than. And | γi ₋₁ −γi
If | ε, the process proceeds to step 72, where the oxygen ratio λ is made smaller than the current value by Δλ in accordance with the magnitude of | γi ₋₁ −γi |, and then the process proceeds to step 74. In step 74, the previous oxygen ratio λi _-1 is compared with the current oxygen ratio λi,
It is determined whether λi ₋₁ −λi | is smaller than a predetermined value δ. When .vertline..lambda.i- ₁ -.lambda.i | <.delta., The process proceeds to step 76, the current oxygen ratio is maintained, and the process returns to step 60 (loop J).

On the other hand, if it is determined at step 64 that | γi ₋₁ −γi | <ε, the routine proceeds to step 68, where it is determined whether the previous control was loop J, and the previous control was loop J.
If so, jump to step 76, maintain the current oxygen ratio, and proceed to the next measurement. In step 68, when the previous control is not loop J, the routine proceeds to step 70, where the oxygen ratio λ is made larger than the current value by Δλ, and the routine proceeds to step 74. If it is determined in this step 74 that .vertline..lambda.i- ₁ -.lambda.i | .delta., The process does not proceed to step 76 but returns directly to step 60 (loop I). Therefore, in the case of passing through the loop I, the next measurement is performed in a state where the oxygen ratio is increased or decreased by Δλ from the current value λ.

As a criterion for increasing / decreasing λ, there are a method of making Δλ proportional to | γi ₋₁ −γi |, a method of making ε / | γi ₋₁ −γi | proportional, etc., but in an embodiment described later, Δλ = 0.5 × | It was set to γi ₋₁ −γi |.

The above loop J is provided because once the optimum oxygen ratio is found, it is fixed at the oxygen ratio until the gas composition fluctuates and the operation is continued for a while. Even if the optimum oxygen ratio is found, the oxygen ratio constantly fluctuates in the vicinity of the optimum oxygen ratio, and the gas composition and the gas production amount slightly change.

A specific example of coal gasification according to the above control flow will be described below.

Charcoal A having the characteristics shown in FIG. 6 was fed at a rate of about 20 kg per hour. First, gasification was started by setting λ = 0.6 Kg / Kg, and the gasification furnace was operated according to the control flow shown in FIG. 3 with γcc as a detection factor. Generated gas measurement interval is 3
As a result of operating with a constant coal supply amount with ε = 0.4 and δ = 0.2, the oxygen ratio was stable at λ = 0.78 Kg / Kg, and the cold gas efficiency ηg was 71% at this time.

From this state, the coal was switched to B coal having the characteristics shown in FIG. After a few minutes from the moment of switching, γcc began to fluctuate toward a larger direction, and the oxygen ratio λ began to decrease from the beginning. The oxygen ratio λ tended to decrease for about 10 minutes, and after increasing and decreasing for a while, the oxygen ratio became constant about 20 minutes after switching the coal, and λ was 0.64 Kg / Kg. The cold gas efficiency at this time was 73%. It should be noted that if ε, δ, Δλ, etc. are made appropriate according to the characteristics of the gasification furnace, such as the size of the gasification furnace, the optimum conditions can be changed in a shorter time.

FIG. 4 is a flow chart showing a control example of another gasification method.

This embodiment is applied to coal in which it is difficult to flow down the coal ash 21 even when the operating conditions of the gasifier are near the maximum cold gas efficiency. As for the coal ash 21, the molten slag is more easily discharged than the powdered ash, so-called fly ash. Therefore, it is preferable to operate the gasification furnace at a temperature equal to or higher than the melting temperature of the coal ash 21 to increase the coal ash recovery efficiency.
Therefore, for coal in which the coal ash 21 does not melt at the gasification temperature near the maximum cold gas efficiency, it is necessary to further increase the oxygen ratio λ to raise the gasification temperature. In this case, the concentration ratio γ of the generated gas composition is obtained, and it is determined whether or not the coal ash 21 is flowing from the gasification chamber 12 to the slag cooling chamber 26 via the slag discharge port 22. This decision is
It is possible by examining the temperature distribution in the gasification furnace,
When the temperature difference between the temperature detector T ₂ and the temperature detector T ₃ is small, the coal ash 21 is flowing well, and when the temperature difference is large, it can be determined that the flow of the coal ash 21 is poor. .

Therefore, the controller 52 takes in the measurement value of the gas analyzer 36 in step 80 of FIG.
At, it is determined whether the temperature difference ΔT detected by the temperature sensor T ₂ and the temperature sensor T ₃ is smaller than a predetermined value τ. The value of τ is set to 110 ° C., for example, and when ΔT is determined to be smaller than τ, the process proceeds to step 84, and the third and subsequent steps are performed.
The same processing as shown in the figure is performed.

On the other hand, if ΔTτ is determined in step 82, the process proceeds to step 86, the oxygen ratio λ is increased, and the process returns to step 80.

Next, a specific example of coal gasification by the control method shown in FIG. 4 will be described.

C coal has a melting temperature of coal ash 21 of 1580 ° C. The gasification status of this coal is as follows. First, λ = 0.7K
The operation was started under the condition of g / Kg. Initially, ΔT = 240 ℃
Therefore, λ increased, ΔT = 100 ° C. was reached after about 20 minutes, and within a few minutes thereafter, it was stabilized at λ = 0.81 Kg / Kg. At this time, the cold gas efficiency was 70%. When the operation was started under the condition of λ = 0.9Kg / Kg, ΔT = 80 ℃ at this time
Therefore, λ decreased, and after about 15 minutes, ΔT = 150 ° C., and once stabilized at λ = 0.75 Kg / Kg. At this time, the cold gas efficiency was 72%. However, 5 minutes after λ became stable, ΔT = 200 ° C., and λ started to rise. These 5 minutes were unsteady when the gasification temperature decreased even if λ was constant. Approximately 10 minutes after λ started to rise, ΔT = 110 ° C., and the temperature stabilized at λ = 0.82 Kg / Kg.

As described above, in this example, the optimum gasification conditions can be easily found by monitoring the composition of the produced gas,
The responsiveness of the control can be made extremely fast to several to ten and several minutes even with respect to changes in the gasification operation amount and coal type. Further, since the ratio of carbon monoxide and carbon dioxide in the generated gas, the ratio of hydrogen gas and carbon dioxide, or both of them are detected, the accuracy of the optimum operating conditions can be improved. Furthermore, by monitoring the temperature at the inner wall of the gasification furnace and the slag discharge port, and by monitoring the composition of the produced gas, the flow condition of the coal ash can be grasped, so that the cold gas efficiency is always maximized under the slag flow condition. It is possible to operate the gasification furnace. Moreover, even if the melting temperature of coal ash is unknown, it is possible to automatically set the optimum operating conditions according to the properties of the coal species.

〔The invention's effect〕

As described above, according to the present invention, even when the coal type or the coal supply amount changes, it is possible to quickly obtain the optimum gasification condition and hold the optimum gasification condition to perform the gasification of coal.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a detailed view of an embodiment of a gasification furnace body of a coal gasification furnace according to the present invention, and FIG. 2 is a configuration block diagram of an embodiment of a coal gasification furnace according to the present invention. FIG. 3 is a flow chart of an embodiment of a coal gasification method according to the present invention, and FIG. 4 is a flow chart showing another embodiment of a coal gasification method according to the present invention,
FIG. 5 is a characteristic diagram showing the relationship between the oxygen ratio and gasification temperature, produced gas concentration, and gasification efficiency, and FIGS. 6 and 7 are coal characteristics showing the relationship between the oxygen ratio and the produced gas component concentration ratio. It is a figure. 10 …… Gasification furnace main body, 12 …… Gasification chamber, 14, 16 …… Coal burner, 18 …… Pulverized coal supply pipe, 20 …… Gasification agent supply pipe, 22 …… Slag discharge port, 26 …… Slag cooling room, 28 ……
Generated gas outlet, 32 …… Dust collector, 34 …… Desulfurization device, 36
...... Gas analyzer, 44 …… Pulverized coal supply device, 52 …… Control device, T ₁ , T ₂ , T ₃ …… Temperature detector.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Morihara 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitate Works, Ltd., Hitachi Research Laboratory (72) Inventor Mitsuhiro Matsuo 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Nitate Works Co., Ltd. Hitachi Research Laboratory (72) Inventor Yoshiki Noguchi 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi, Ltd.

Claims (5)

[Claims] 1. Coal and gasifying agent are fed into a high temperature furnace,
In the method of gasifying coal, the concentration ratio of the generated carbon monoxide and carbon dioxide or the concentration ratio of hydrogen gas and carbon dioxide is obtained multiple times, and the difference between the concentration ratio obtained this time and the concentration ratio obtained last time is calculated. When the absolute value is a predetermined value or more, the amount of the gasifying agent is decreased, and when the absolute value is less than the predetermined value, the amount of the gasifying agent is increased. And coal gasification method. 2. Coal and gasifying agent are fed into a high temperature furnace,
In a coal gasification method for gasifying coal, it is detected whether or not the ash content in the furnace is melted, and when the ash content is not melted, the supply amount of the gasifying agent is increased to reduce the ash content. Along with melting, the concentration ratio of carbon monoxide and carbon dioxide or the concentration ratio of hydrogen gas and carbon dioxide generated in the molten state of the ash is obtained multiple times, and the concentration ratio obtained this time and the concentration ratio obtained last time When the absolute value of the difference is equal to or greater than a predetermined value, the amount of the gasifying agent is reduced,
A method for coal gasification, wherein the amount of the gasifying agent is increased when the absolute value is less than a predetermined value. 3. A furnace body having a gasification chamber formed therein,
A burner for supplying coal and a gasifying agent to the gasification chamber,
In a coal gasification furnace having a slag discharge port formed below the gasification chamber for discharging ash and a generated gas discharge port for guiding generated gas generated in the gasification chamber to the outside, the gasification chamber A first temperature sensor for detecting the wall temperature of the
A second temperature sensor that detects a wall surface temperature of the slag discharge port, a concentration detector that detects concentrations of a plurality of components in the generated gas, a detection value of the first temperature sensor, and the second temperature sensor. And a computing unit for obtaining the difference between the detected value and the temperature difference output by the computing unit by increasing the supply amount of the gasifying agent when the temperature difference output by the computing unit is a predetermined value or more. In addition to making it less than a predetermined value, the component concentration ratio is calculated based on the component concentration obtained by the concentration detector, and the absolute value of the difference between the concentration ratio calculated this time and the concentration ratio calculated last time is
When the amount of the gasifying agent is reduced to a predetermined value or more,
A coal gasifier comprising a control device for increasing the amount of the gasifying agent when the absolute value is less than a predetermined value. 4. The burner is provided in a plurality of stages in the vertical direction of the furnace body, and the first temperature sensor is provided on a furnace wall at a position corresponding to the lowest stage of the burners provided in the plurality of stages. The lime gasifier according to claim 3, characterized in that 5. The coal gasification apparatus according to claim 3, wherein the predetermined temperature difference is 110 ° C.