JP5211369B1 - Coal pyrolysis method - Google Patents

Abstract

In a two-chamber two-stage reactor composed of a gasification furnace and a reforming furnace, a change in gas properties when a coal input amount is changed in the gasification furnace is suppressed.
A gasification furnace that protects a furnace wall by a self-coating method in a lower stage, and a gasification type pyrolysis apparatus having two stages of upper and lower chambers provided with a reforming furnace in an upper stage, Coal and oxygen or oxygen and water vapor are introduced to produce gasified gas by partial oxidation, the gasified gas is introduced into the reforming furnace, coal is introduced into the reforming furnace, A coal pyrolysis method for generating gas, oil, and char by pyrolysis of the coal using sensible heat of gasification gas, wherein the furnace wall of the gasification furnace has a boiler structure, and is generated in the boiler. It is characterized in that the amount of steam that has been measured is measured and the amount of oxygen input to the gasifier is reduced when the measured amount of steam is increased.
[Selection] Figure 1

Description

  The present invention relates to a method for producing gas, oil, and char by rapidly gasifying and pyrolyzing coal in an airflow layer using a two-chamber, two-stage airflow layer type pyrolysis apparatus.

  To date, several coal pyrolysis processes have been proposed in which coal is pyrolyzed at high temperatures to produce fuel gas containing hydrocarbon gas such as methane and oil such as benzene, toluene and xylene (BTX). Has been.

  In Patent Document 1, coal is blown into a high-temperature gas generated by gasification of coal and carbonaceous raw material with oxygen, and rapid heating / pyrolysis reaction of coal is performed in an air flow layer, and in particular, BTX is obtained in a high yield. It is possible to reduce the initial cost of the equipment, and there is shown a high thermal efficiency coal pyrolysis method that does not require heat supply.

  Further, in Patent Document 2, coal and hydrogen are blown into a high-temperature gas generated by gasification of coal and carbonaceous raw material with oxygen, and rapid heating / hydrocracking reaction of coal is performed in an airflow layer, A coal hydrothermal pyrolysis method that can obtain a fuel gas such as methane in a high yield is shown.

  In patent document 3, in order to ensure the fluidity | liquidity of the molten slag in a slag tap, the cooling water temperature of the water cooling pipe which comprises a slag tap is monitored, and it inputs into a gasification furnace (combustor) based on a cooling water temperature. An operating method for adjusting the amount of oxygen is shown.

JP-A-5-295371 JP 2004-217868 A Japanese Patent Laid-Open No. 9-13050

  In the processes proposed in Patent Documents 1 and 2, in the lower gasification furnace of the upper and lower two-chamber two-stage reactor, the furnace wall is generally provided with slag self-coating that protects the water-cooled wall and the boiler tube with molten slag. Used. In this method, the wall surface is protected by adhering ash contained in the coal to the water-cooled wall or the boiler pipe constituting the wall surface. In these processes, coal is introduced into the furnace by airflow conveyance, but in the airflow conveyance of powder, the input amount often fluctuates, such as when the pressure balance between the reactor and the supply system changes, and gasification in the lower stage When the amount of coal and other raw materials charged into the furnace fluctuates, the input amount of coal and other raw materials is measured by the change in the weight of the supply hopper. There has been a problem that the oxygen / coal ratio in the gasification furnace fluctuates, the composition of the product gas changes, and the heat generation efficiency defined by, for example, equation (1) decreases. When the amount of coal input varies, the temperature inside the gasifier changes, and if the amount of oxygen input is adjusted so as to suppress the change, the fluctuation can be avoided, but the inside of the gasifier 2 is at a high temperature of about 1500 ° C. Therefore, long-term continuous temperature measurement is practically impossible.

The method of Patent Document 3 is to determine the adhesion state of the molten slag at the slag tap based on the temperature difference between the cooling water in and out of the water-cooled pipe constituting the slag tap, and adjust the amount of oxygen to be charged into the gasification furnace. Since the cooling water amount is generally set so that the cooling water temperature difference is 5 ° C. or less, it becomes about 0.5 ° C. when the amount of heat removal from the gasification furnace is 10%, and 1 ° C. to judge the situation around the slag tap. The following subtle adjustments are required, and there is a problem that measurement errors are likely to occur. Moreover, in the method of patent document 3, the state of the molten slag which flows out from a slag tap is monitored by water temperature, and the condition in a gasification furnace is not monitored.
Heat generation efficiency = (Production gas heat generation amount + Production tar heat generation amount) / (Input coal heat generation amount−Production char heat generation amount) (1)

  The present invention is a method for pyrolyzing coal using a gasification furnace that protects the furnace wall by a self-coating method at the lower stage and a two-stage, two-stage, gas-flow-type pyrolysis apparatus provided with a reforming furnace at the upper stage. In addition, an object of the present invention is to provide a method for pyrolyzing coal, in which even if the amount of coal input to the gasification furnace is increased, there is little decrease in the calorific value of the product gas generated in the reforming furnace.

In order to solve this problem, the gist of the present invention is as follows.
(1) Using a gasification furnace that protects the furnace wall by the self-coating method at the lower stage and a two-stage, two-stage, gas-flow type thermal decomposition apparatus with a reforming furnace at the upper stage, And oxygen or oxygen and water vapor are added to generate gasified gas by partial oxidation, the gasified gas is introduced into the reforming furnace, coal is charged into the reforming furnace, and the gas A coal pyrolysis method for producing gas, oil, and char by pyrolysis of the coal using sensible heat of gasification gas, wherein the furnace wall of the gasification furnace has a boiler structure and is generated in the boiler. The amount of steam is measured, and when the measured amount of steam increases, the amount of oxygen input to the gasifier is reduced.
(2) It is characterized in that the amount of steam generated in the boiler is adjusted to be the amount before the increase in the amount of steam by reducing the amount of oxygen input to the gasifier.
(3) The amount of coal input to the reforming furnace is reduced according to the amount of decrease in the amount of oxygen input to the gasifier.

  According to the present invention, when pyrolyzing coal using a gasification furnace that protects the furnace wall by a self-coating method in the lower stage and a two-stage, two-stage, gas-flow-type pyrolysis apparatus provided with a reforming furnace in the upper stage In addition, since the situation inside the furnace can be quickly grasped and dealt with, even if the amount of coal input to the gasifier increases, there is little reduction in the efficiency of gasification in the reformer and stable pyrolysis gasification of coal Operation becomes possible.

1 is a schematic view of a coal air-flow type thermal decomposition apparatus according to the present invention. It is the figure which showed the relationship between the slag coating thickness and the amount of heat dissipation in a gasification furnace.

  When coal is gasified using oxygen as a gasifying agent, a gasified gas mainly composed of carbon monoxide, carbon dioxide, hydrogen, and water vapor is generated. The temperature of the gasifier must be equal to or higher than the melting point of the ash because it is necessary to melt and discharge the ash contained in the coal to be gasified. The temperature of the gasification gas exiting from the gasification furnace is also the temperature, and by introducing coal into the gasification gas in the reforming furnace, the temperature of the coal is raised and a thermal decomposition reaction is caused to obtain a product.

  The above gasification and pyrolysis reaction can be carried out using a gasification furnace that protects the furnace wall in the lower stage using a self-coating method, and an upper and lower two-chamber, two-stage airflow bed reactor equipped with a reforming furnace in the upper stage. it can. The boundary between the gasification furnace and the reforming furnace has a throat structure, and the two-chamber two-stage can completely separate the part that performs gasification of coal and the part that performs thermal decomposition. It becomes possible to freely set the operating conditions of the part. Here, the two-chamber reactor is a reactor structure in which the gas flow path is partially throttled to partially increase the flow velocity, so that coal particles or the like thrown into the upper chamber fall into the lower chamber. A reactor that can prevent reaction and set independent reaction conditions in each chamber.

  The present invention will be described in detail below. FIG. 1 is a schematic view of a coal air-bed type thermal decomposition apparatus used in the present invention. This apparatus is mainly composed of a reforming furnace 1, a gasification furnace 2, and a throat 3 that connects the two.

  Since the ash contained in the gasification coal 9 becomes a molten slag 15 due to the high temperature due to partial oxidation of the gasification coal 9 in the gasification furnace 2, the slag tap 6 can be discharged from the lower part of the gasification furnace 2. It is preferable to provide a water tank 8 for collecting the slag 15.

  In order to adjust the melting point of the ash contained in the gasified coal 9 or to form a sufficient slag self-coating layer, the gasified coal 9 includes limestone, cinnabar, granite, chamotte, blast furnace slag, etc. and mixtures thereof. The melting point adjusting agent 11 may be added.

  The wall of the gasification furnace 2 is constituted by a boiler tube 17, and the steam generated in the boiler section is separated by a steam drum 19 and discharged by a pressure adjusting valve 21 according to the pressure in the steam drum 19. The amount of discharged steam is measured by a steam flow meter 21 and discharged as generated steam 22.

The gasification furnace 2 is provided with one or a plurality of gasification burners 5 to be charged together with oxygen 12 that is an oxidizing agent for partially oxidizing the gasified coal 9 or oxygen 12 and water vapor 13. ing. In the gasification furnace 2, in order to convert as much carbon and hydrogen components in the hydrocarbons contained in the gasified coal 9 to be supplied into CO and H ₂ as much as possible, the gasified coal 9 and oxygen 12, or oxygen 12 and It is necessary to react with the oxygen 12 and the water vapor 13 before the water vapor 13 is quickly mixed and the volatile matter generated from the gasified coal 9 is sooted. For this purpose, the gasified coal 9, oxygen 12 and water vapor 13 into the gasification furnace 2 are blown by the gasification burner 5 and mixed rapidly. The gasification gas 14 generated in the gasification furnace 2 is sent to the reforming furnace 1 through the throat 3.

  The operation pressure and temperature in the gasification furnace 2 are maintained at, for example, 0.1 to 20 MPa and 1300 to 1700 ° C.

  Next, in the reforming furnace 1, the reformed coal 10 is charged and a coal pyrolysis reaction occurs. This pyrolysis reaction produces gas, solid char, and tar from coal. Gas can be used as fuel or chemical raw material, char can be used as solid fuel, and tar can be used as chemical raw material or fuel. Although it is possible to produce the product by the pyrolysis reaction as the reformed coal 10 alone as the one to be charged into the reforming furnace 1, in addition to the reformed coal 10, one or more kinds of hydrogen, steam, and oxygen are used. At the same time, it is possible to change the properties and amount of the gas and tar generated.

  The operating pressure and temperature in the reforming furnace 1 are maintained at, for example, 0.1 to 20 MPa and 500 to 1200 ° C. Since the reforming furnace 1 and the gasification furnace 2 are connected to each other through a throat, the pressure is operated at substantially the same pressure in both furnaces. When the recovered material is mainly gas and oil, the reforming furnace 1 is operated under a relatively low pressure and temperature condition of normal pressure to less than 1 MPa and temperature of 500 to 800 ° C., and the recovered material is mainly gas. Operates under relatively high pressure and temperature conditions, with a pressure of 1 MPa or more and a temperature of 800-1200 ° C. When the recovered material is mainly a gas, a reforming aid such as steam or hydrogen is added to the reforming furnace 1, or a reforming aid such as steam is added to the gasification furnace 2, so that the reforming furnace 1 It is preferable to promote the gasification reaction inside.

  The char generated in the reforming furnace 1 is preferably used as a fuel for the gasification furnace 2 as a fuel together with the gasified coal 9 and recycled.

  Further, the gasification coal 9 is charged into the gasification furnace 2 by airflow conveyance. However, the amount of gasification coal 9 input is likely to vary due to pressure fluctuations in the gasification furnace 2, and in this case, oxygen 12 If the input amount of the gasified coal 9 is not changed, the state of partial combustion of the gasified coal 9 in the gasification furnace 2 changes, and the composition and temperature of the gasified gas 14 change. When the temperature and composition of the gasification gas 14 change, the temperature of the reforming furnace 1 also changes, and the properties of the produced gas, char, and oil 16 produced also change.

  For example, when the input amount of gasified coal 9 decreases with the amount of oxygen 12 being constant, the ratio of oxygen 12 to gasified coal 9 in the partial oxidation reaction increases in the gasification furnace 2, and gasification occurs. The temperature inside the furnace 2 rises. When the temperature rises, the slag self-coating layer constituting the wall surface of the gasification furnace 2 becomes thin, the amount of heat transferred from the gasification furnace 2 to the boiler tube 17 increases, and the amount of generated steam 22 increases. The change in the generated steam amount 22 is grasped by measuring with the steam flow meter 21, and the gas in the gasifier 2 is reduced by reducing the input amount of the oxygen 12 to an amount where the generated steam 22 is in a stable state. It becomes possible to stabilize the conversion situation.

  FIG. 2 shows an example of the relationship between the thickness of the slag self-coating layer in the gasifier and the amount of heat dissipated. The amount of heat dissipated (= the amount of heat received by the boiler water vapor) increases as the slag self-coating thickness decreases. The slag self-coating thickness is determined by the temperature in the gasification furnace 2 and the temperature of the boiler tube 17 on the furnace wall if the slag property is constant. The temperature fluctuation of the boiler pipe 17 is compared with the temperature fluctuation in the gasification furnace 2. Since it is negligible and can be ignored, it depends on the temperature in the gasification furnace 2.

  Further, when the input amount of the gasified coal 9 is reduced due to the change in the input amount of the gasified coal 9 to the gasifier 2, the amount of the gasified gas 14 sent to the reformer 1 is reduced. If the input amount of is kept the same, the temperature in the reforming furnace 1 decreases, and the properties and yield of the product gas, char, and oil 16 generated by the thermal decomposition reaction change. In order to prevent this change, it is possible to maintain a constant pyrolysis reaction by reducing the amount of reformed coal 10 input according to the amount of oxygen 12 input to the gasifier 1 being reduced. It becomes possible to stabilize the composition and calorific value.

  After stabilizing the reaction state in the furnace by this method, adjustment of gasified coal 9 with fluctuations in the input amount is performed, and the operation state can be brought to the state before change by setting the original operation control value. In addition, it is possible to maintain the ratio of the heat generation amount of the generated gas and tar to the raw material heat generation amount (heat generation efficiency) at a high level.

The heat generation efficiency can be expressed as the following equation, for example.
Heat generation efficiency = (Production gas heat generation amount + Production tar heat generation amount) / (Input coal heat generation amount−Production char heat generation amount) (1)

  Even during steady operation, the state of the furnace is judged based on the amount of steam generated in the gasification furnace wall boiler, and stable operation is possible by adjusting the amount of oxygen 12 to be constant.

  In this example, since the pressure in the reforming furnace 1 and the partial pressure of water vapor are relatively high, the amount of tar generated is small, the composition of the components is hardly changed, and the calorific value is low and stable. The impact on efficiency was negligible.

  In the above method, the case where the fluctuation of the steam amount increases has been described. However, when the fluctuation of the steam amount decreases, the gasified coal 9 increases. In this case, the gas temperature decreases as the gas amount increases. In this case, the slag self-coating layer is not thinned. The influence on the gas composition does not deteriorate the calorific value because the oxygen amount in the gasification furnace 2 is reduced with respect to the coal amount. The problem is the effect on the slag 15 discharge from the slag tap 6 due to the temperature drop of the gasification furnace 2, but this is extremely extreme because the slag adhesion to the furnace wall increases when the temperature drops. The slag tap 6 is not blocked in a short time, and can be dealt with even after confirming the amount of coal input after the fluctuation. For this reason, problems such as deterioration of gas properties occur when the amount of steam increases, but there is no particular problem even if the reverse operation is performed when the amount of steam decreases.

Example 1
An example in the gasification pyrolysis operation using the apparatus shown in FIG. 1 is shown below.
The operating conditions of the gasification furnace 2 were a pressure of 2.5 MPa and a temperature of 1460 ° C., and the operating conditions of the reforming furnace 1 were a pressure of 2.5 MPa and a temperature of 1100 ° C.

Gasified coal 9 pulverized to an average particle size of 40 μm is charged into the gasification furnace 2 at 500 kg / h (coal ash content: 2.7%, volatile content: 45%, moisture content: 5%) by airflow conveyance, and the gasification furnace When steam 13 was charged at 50 kg / h and oxygen 12 at 310 Nm ³ / h, and reformed coal 10 was charged at 162 kg / h into the reformer 1, the gas at the gasifier 2 outlet (throat 3) The amount of the gasified gas 14 is 1134 Nm ³ / h, the amount of heat generated by the gasified gas 14 is 1879 kcal / h, the amount of generated gas at the reforming furnace outlet 7 is 1279 Nm ³ / h, and the amount of generated gas is 2239 kcal / h. It was. The amount of tar produced was negligible.

  When the amount of gasified coal 9 input to the gasification furnace 2 increases from that state to 475 kg / h due to a 5% fluctuation, the amount of steam generated in the furnace wall boiler of the gasification furnace 2 increases from 250 kg / h to 275 kg at a pressure of 4 Mpa. / H.

Next, when the amount of oxygen 12 input to the gasification furnace 2 is decreased and adjusted so that the amount of steam generated in the furnace wall boiler of the gasification furnace 2 is constant, the amount of oxygen 12 input is 298 Nm ³ / h. The amount of gasification gas 14 generated in the gasification furnace 2 is 1088 Nm ³ / h, the gas heating value is 1842 kcal / h, the gas amount at the outlet of the reforming furnace 1 (throat part 3) is 1228 Nm ³ / h, the gas heating value Was 2188 kcal / h. The amount of tar produced was negligible.

  The heat generation efficiency represented by the above formula (1) changed from 79.5% to 78.3% before and after the change in the input amount of the gasified coal 9, but high heat generation efficiency could be maintained ( (The amount of tar produced was very small).

  The change in the amount of heat generated from the gas before the change was -2.0% for the gasification gas 14 at the gasification furnace outlet (throat 3) and -2.2% for the reforming furnace 1 outlet gas.

(Example 2)
In the same apparatus and reaction conditions as in Example 1, when the gasification coal 9 input amount of the gasification furnace 2 fluctuates (increases) by 5%, it is proportional to the decrease rate of the amount of oxygen 12 input to the gasification furnace 2. The example which reduced the input amount of the modified coal 10 is shown.

When variation in the input amount of gasification coal 9, when reduced the amount of oxygen 12 of the gasification furnace 2 from 310Nm3 / h to 298Nm ³ / h (reduction rate of 4%), the same reduction rate, modifying When the input amount of coal 9 was reduced from 162 kg / h to 156 kg / h, the gas amount at the reformer outlet 7 was 1229 Nm ³ / h and the gas heating value was 2204 kcal / h. The amount of tar produced was negligible.

  The change in the calorific value of the product gas from before the change stopped at -1.5% at the reformer outlet gas. By reducing the amount of coal input to the reforming furnace, the pyrolysis reaction in the reforming furnace was changed, and the amount of methane generated was slightly increased as compared with Example 1, and the amount of gas generation and heat generation was increased.

(Comparative example)
The apparatus and reaction conditions are the same as in Example 1, but the case where the amount of oxygen 12 was not adjusted when the amount of gasified coal 9 charged in the gasification furnace 2 was varied is shown below.

The amount of gasification gas 14 in the gasification furnace 2 is 1088 Nm ³ / h, the heat generation amount of the gasification gas 14 is 1781 kcal / h, the amount of generated gas from the reforming furnace is 1227 Nm ³ / h, and the heat generation amount of the generated gas is 2127 kcal. The change in the amount of heat generated from the gas before the change was -5.2% for the gasification gas at the gasifier exit (throat 3) and -5.0% for the product gas from the reforming furnace. The rate of decline was greater than in the examples.

  In this way, the amount of oxygen supplied to the partial oxidation section (gasification furnace 2) is adjusted so that the amount of steam generated in the gasifier furnace wall boiler is constant, and further, the thermal decomposition section (reforming furnace 1). By adjusting the amount of the reformed coal 10 to be supplied to the gas, a gas with a calorific value close to the gas calorific value before the fluctuation can be obtained, and the fluctuation rate is -2 when adjusting only the oxygen amount (Example 1). When the amount of reformed coal is adjusted (Example 2) together with .2% and oxygen amount, it becomes -1.5%, and the fluctuation of the gas calorific value can be kept small.

  In addition, when the gasification furnace wall is replaced with a steam boiler and water-cooled under the conditions of Example 1 (the temperature difference between the inlet and outlet of the cooling water is set to 5 ° C.), the same adjustment as in the example is performed. However, since a temperature difference of only about 0.5 ° C. occurs at the time of fluctuation, the error becomes large and control is difficult.

  Table 1 shows the gas composition and efficiency of the examples and comparative examples together with the state before the change. In Examples 1 and 2, the efficiency is improved compared to the comparative example, and the change in gas composition is also small.

DESCRIPTION OF SYMBOLS 1 ... Reforming furnace 2 ... Gasification furnace 3 ... Throat 4 ... Reformed coal injection nozzle 5 ... Gasification burner 6 ... Slag tap 7 ... Reforming furnace exit 8 ... Water tank 9 ... Gasification coal 10 ... Reformed coal 11 ... Melting point adjusting agent 12 ... oxygen 13 ... water vapor 14 ... gasification gas 15 ... slag 16 ... generated gas, char, oil 17 ... boiler tube 18 ... pump 19 ... steam drum 20 ... pressure regulating valve 21 ... steam flow meter 22 ... generated steam

Claims (3)

Using a gasification furnace that protects the furnace wall by a self-coating method at the lower stage, and a two-stage, two-stage, gas-flow-type thermal decomposition apparatus with a reforming furnace at the upper stage, coal and oxygen are added to the gasification furnace. Alternatively, oxygen and water vapor are introduced to generate a gasification gas by partial oxidation, the gasification gas is introduced into the reforming furnace, coal is introduced into the reforming furnace, and the gasification gas A coal pyrolysis method for producing gas, oil, and char by pyrolysis of the coal using sensible heat,
The heat of coal is characterized in that the furnace wall of the gasifier has a boiler structure, the amount of steam generated in the boiler is measured, and the amount of oxygen input to the gasifier is reduced when the measured amount of steam is increased. Disassembly method.   The coal according to claim 1, wherein the amount of steam generated in the boiler is adjusted to be the amount before the increase in the amount of steam by reducing the amount of oxygen input to the gasification furnace. Thermal decomposition method.   The method for pyrolyzing coal according to claim 1 or 2, wherein the amount of coal input to the reforming furnace is decreased in accordance with a decrease amount of oxygen input to the gasification furnace.

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