JP2007231203A - Method for gasifying carbonaceous raw material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To hold a refractory material of an oven wall and the thickness of slag attachment while performing the discharge of the slag stably in a gasification oven of carbonaceous raw materials such as coal, etc. <P>SOLUTION: This method for gasifying the carbonaceous raw material by using a gasification oven of which at least inner wall surface is formed with the refractory material and equipped with an oven wall porous part for putting-in a cooling medium from its outside, while putting-in the cooling medium, gasifying fed materials including the carbonaceous raw materials to fuel by using oxygen-containing gas is provided by increasing the putting-in amount of the cooling medium in the case that at least one content of a component among components constituting molten slag is higher in the molten slag by comparing the ash composition of the fed materials before the gasification with the ash composition of discharged molten slag. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a fuel gas by rapidly gasifying a carbonaceous raw material such as coal in an air flow layer, and discharging ash contained in the coal or the like as molten slag.

In the gas-bed gasification of carbides such as coal, finely pulverized carbide raw materials (carbonaceous raw materials) such as coal are sent to the gasification furnace by airflow conveyance, and are partially oxidized by oxygen or air in the furnace. A method for producing a fuel gas mainly composed of carbon and hydrogen is common. At that time, ash contained in carbides such as coal is discharged as molten slag. A method of protecting the furnace wall by attaching a thin refractory to the water cooling jacket or boiler tube and attaching molten slag on the refractory during the operation of the gasification furnace is used for the furnace wall that constitutes the gasification furnace. It is done. Patent Document 1 discloses a method in which a brick having a hole is provided on a furnace wall of a slag contact portion of a metal refining furnace, and a coolant is introduced from the hole. Patent Document 2 discloses a method of measuring the specific conductivity of the discharged molten slag, estimating the basicity of the slag from the measured value, and introducing the slag component into the furnace according to the estimation result. .
Further, Patent Document 3 discloses a coal gasification furnace in which a coolant jet nozzle is provided on the upper side wall in the gasification chamber in order to lower the temperature of the combustible gas generated in the gasification chamber of the coal gasification furnace. Has been.
JP 59-59820 A JP-A-8-193212 JP 7-278573 A

  In a gasification furnace in which a furnace wall is composed of a water-cooled jacket or a boiler tube and a refractory, it is necessary to increase the fluidity of the slag in order to ensure the discharge performance of the molten slag. As a method for this, a method of increasing the temperature in the gasification furnace is taken, but when the temperature of the gasification furnace is increased, alumina, which is one of the refractory components constituting the furnace wall, is melted into the molten slag. There is a problem that the melting point of the slag is raised and the slag discharge property is deteriorated. In addition, when raw materials with increased slag basicity and lower slag melting temperature are used in the same gasification furnace, refractories of the refractory are promoted. There exists a problem that the thickness of slag adhesion reduces to several mm.

In order to use the refractory structure described in Patent Document 1 for the furnace wall, there is no indication of the amount of coolant input, and if the required amount on the heat balance is set as the input amount, cooling may be performed depending on the situation of the gasification furnace. There is a problem that the refractory melts insufficiently and the unnecessary amount of unnecessary gas is mixed into the generated gas due to excessive coolant.
When the method described in Patent Document 2 is applied to the operation of a gasification furnace, the specific conductivity of the discharged molten slag is measured, the basicity of the slag is estimated from the measured value, and according to the estimation result, A method of adjusting the basicity so that slag can be easily discharged can be considered. In this case, however, there is a problem of wear of the refractory constituting the furnace wall due to the molten slag as described above.
The invention disclosed in Patent Document 3 is originally intended to prevent adhesion of slag, and has a problem that the wall surface is made of metal and the slag layer cannot be held on the surface.

  An object of the present invention is to prevent the refractory constituting the furnace wall from being melted and to stably operate the gasification furnace without deteriorating the slag fluidity at the slag tap.

In order to solve this problem, the gist of the present invention is as follows.
(1) At least the inner wall surface of the furnace wall is formed of a refractory material, and oxygen is supplied while using a gasification furnace having a furnace wall porous portion for introducing a cooling medium from the outside while introducing the cooling medium. In the gasification method of carbonaceous raw material, the feed material containing carbonaceous raw material is converted into fuel gas using the contained gas and the residue containing ash is discharged as molten slag. Compared with the ash composition of the molten slag, the carbon is characterized in that the amount of the cooling medium is increased when the content of at least one of the components constituting the refractory is higher in the molten slag Gasification method for quality raw materials.
(2) In the gasification method according to (1), a basicity adjusting agent composed of a lime component is supplied as a feed material to the gasification furnace, and the basicity of the ash content of the feed material before fuel gasification is reduced to 0. A method for gasifying a carbonaceous raw material, which is adjusted to 1 or more and 1.5 or less.
(3) The gasification method according to (1) or (2), wherein the refractory contains 50% or more of alumina by mass%, and the alumina concentration in the molten slag ash is 25% by mass or less. A method for gasifying a carbonaceous raw material, wherein the amount of cooling medium introduced from the furnace wall porous portion is controlled.

  The “carbonaceous raw material” as used in the present invention refers to a substance mainly composed of carbon and hydrogen such as fossil fuels and biomass such as coal and petroleum, and is a solid substance generated when pyrolyzing coal. Char and liquid tars, petroleum residues, petroleum coke, coal coke, biomass, plastics are included, and these are used alone or in combination. Moreover, carbon is often contained in the molten slag in addition to the ash, but it is usually 1% by mass or less and at most several mass%, and the ash accounts for the majority.

  According to the present invention, it is possible to prevent the refractory constituting the furnace wall from being worn, ensure the fluidity of the molten slag, and operate the gasifier stably.

  When a feed material containing a carbonaceous raw material is converted into fuel gas using an oxygen-containing gas, a gasification gas mainly composed of carbon monoxide, carbon dioxide, hydrogen, and water vapor is generated. The temperature of the gasification furnace is not lower than its melting point because it is necessary to melt and discharge ash contained in carbonaceous raw materials such as coal, biomass, and plastics to be gasified, and is generally about 1300 to 1600 ° C. When the melting point of ash contained in the carbonaceous raw material is higher than the above temperature range, a basicity adjusting agent composed of a lime-based component containing Ca such as limestone is preferably mixed with the feed material in order to lower the melting point. .

The present invention will be described in detail below.
FIG. 1 shows a schematic view of a gasification furnace used in the present invention. In the gasification furnace 1 according to the present invention, at least the inner wall surface with which fuel gas and molten slag come into contact is formed by a furnace wall 6 made of a refractory material. A furnace wall porous portion 5 is provided. The furnace wall 6 may be formed by coating the surface of a water-cooled jacket or boiler tube with a refractory such as alumina, silica, magnesia, or the like, or the furnace wall 6 is formed only from these refractories, You may make it cool the outer peripheral surface of a furnace wall with a water cooling jacket etc. as needed. Moreover, about the furnace wall porous part 5, you may make it form a part of furnace wall 6 with the porous brick which consists of refractories, for example as described in patent document 1, and piping is provided in a refractory. It may be formed so as to be embedded.

  A slag tap 7 is provided on the bottom surface of the gasification furnace 1, and a slag granulating water tank 8 is installed below the slag tap 7. Further, a cooling medium charging port 3 and a cooling medium flow path 4 for charging the cooling medium 11 are provided outside the furnace wall porous portion 5, and the cooling medium 11 charged from the cooling medium charging port 3 is porous to the furnace wall. The gas is passed through the hole of the portion 5 and is introduced into the gasification furnace 1 (arrow 12 in the figure). Further, a gasification burner 2 is attached to the gasification furnace 1 so as to pass through the furnace wall 6, and a carbonaceous raw material 9 to be gasified through the gasification burner 2 from outside, oxygen, air, etc. The oxygen-containing gas / steam 10 is introduced into the gasification furnace 1, and the carbon / hydrogen content in the carbonaceous raw material is partially combusted in the gasification furnace 1. At this time, from the viewpoint of improving the calorific value of the fuel gas, it is preferable to use the oxygen-containing gas / steam 10 having a high oxygen concentration, and it is more preferable to use only oxygen. Oxygen produced by the PSA method, the cryogenic separation method, or the like can be used.

  A product gas (fuel gas) 15 generated by partial combustion in the gasification furnace 1 is discharged from the upper part of the gasification furnace 1 to the outside of the furnace. On the other hand, the ash content in the carbonaceous raw material 9 is melted and most of the ash content adheres to the inner wall surface of the furnace wall 6. The carbonaceous raw material 9 and the ash and other residues of the basicity adjusting agent that are added as necessary adhere to the furnace wall as molten slag as described above, and this molten slag flows down the wall surface by gravity, and further slag taps 7 falls into the water tank 8 for slag granulation (arrow 13 in the figure) and is discharged as granulated slag 14. The molten slag adhering to the wall of the gasification furnace 1 reacts with the refractory constituting the furnace wall 6 when it descends through the wall of the gasification furnace 1, causing melting of the refractory. This becomes particularly remarkable in the vicinity of the gasification burner 2 having a high temperature.

  In the method of the present invention, the surface of the furnace wall porous part 5 is cooled by the cooling medium 11 put into the gasification furnace 1, and it becomes possible to prevent the furnace wall porous part 5 from being melted. As the refractory constituting the furnace wall 6 of the gasification furnace 1, a refractory having a high heat resistance temperature is used, which is greatly different from the ash content composition in the carbonaceous raw material 9. When the refractory on the furnace wall 6 is eluted by reacting with the molten slag, the ash composition of the molten slag 13 changes. Therefore, for example, by measuring the ash composition of the granulated slag 14 that has been discharged and cooled by water as a post-treatment, it is possible to detect the state of melting of the furnace wall 6. As a method for measuring the ash composition of the granulated slag 14, a fluorescent X-ray analysis method is usually used. If it becomes clear that the furnace wall is melted from the ash concentration after the analysis, it becomes possible to prevent the furnace wall 6 having the refractory from being melted by increasing the amount of the cooling medium 11, and the furnace wall. Since it becomes possible to adhere molten slag on 6, the furnace wall thickness can be maintained. With this method, it becomes possible to protect the refractory forming the furnace wall 6 with a minimum amount of cooling medium.

  Generally, when the ash composition of the granulated slag 14 is measured by fluorescent X-ray analysis, about 1 hour is required for sample preparation and analysis. The melting loss of the furnace wall 6 is a traveling speed of about 1 mm or less per hour in a normal operation, and even if the analysis takes about 1 hour, the amount of wear of the furnace wall 6 is small, and the cooling medium 11 is increased. It is possible to recover the furnace wall thickness.

  Of the ash content composition of the molten slag, for example, in the case of an alumina refractory, if the alumina component is higher than the alumina component of the ash content in the carbonaceous raw material, the furnace wall 6 is melted. Leads to a decrease. At this time, if the alumina in the slag exceeds 25% by mass, the melting point of the slag rises and the slag discharge performance deteriorates. For example, the alumina in the ash composition of the molten slag is 25% by mass or less. It is preferable to control the charging amount of the cooling medium.

When the melting point of the ash contained in the carbonaceous raw material 9 is higher than 1500 ° C., a basicity adjusting agent composed of a lime-based component such as limestone is preferably added in advance and used as a feed material together with the carbonaceous raw material. In this case, the basicity of the total of the ash contained in the carbonaceous material 9 (i.e. ash feed) (CaO / SiO ₂₎ of 0.1 or more, those were adjusted to be 1.5 or less It is preferable to use it. If the basicity is lower than 0.1, the melting temperature of the slag rises, and if it is 1.5 or more, the slag viscosity rises and the slag discharge property deteriorates. When the basicity adjusting agent is introduced, the ash composition of the discharged granulated slag 14 is compared with the ash composition of the feed material after the basicity adjustment to estimate the refractory melt condition, The amount of 11 will be adjusted.

  As for the refractory forming the furnace wall 6, it is generally preferable to use a refractory having an alumina content of 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more in order to increase the heat resistance temperature. The balance may contain one or more of carbon, silica, magnesia, iron oxide, zirconia, calcium oxide, and sodium oxide.

  The refractory generally contains 50% by mass or more of alumina. At this time, if the alumina contained in the ash content in the granulated slag 14 exceeds 25% by mass, the fluidity of the molten slag 13 is suddenly deteriorated and hardly flows. It becomes slag. Therefore, the alumina concentration in the ash contained in the granulated slag 14 is measured, and when the alumina concentration exceeds 25% by mass, the amount of the cooling medium 11 is increased to prevent the refractory from being melted and the molten slag. 13 fluidity can be ensured. Although the lower limit is not particularly defined, the concentration of alumina in ash contained in the carbonaceous raw material 9 is preferably the lower limit in the sense of minimizing the amount of refractory melt loss.

  As the cooling medium 11, water, water vapor, pressurized water vapor, gas, or the like can be used, but it is preferable to use gas in consideration of cooling efficiency and stability. As the cooling medium, other than the above, for example, an inert gas such as nitrogen or argon can be cited. In particular, in addition to the inert gas such as nitrogen, the gas in the gasifier 1 is decomposed by receiving heat. In addition, a gas containing hydrocarbons having a cooling effect and a cooling effect can also be used. In order to prevent the concentration of the product gas 15 from decreasing, the product gas 15 can be used as the cooling gas (cooling medium) 11 after cooling and purification.

  The furnace wall porous part 5 in the furnace wall 6 may be used in a particularly high heat load part such as the vicinity of a gasification burner, and the other part of the furnace wall has a refractory structure whose outside is cooled by a water cooling jacket or the like. no problem.

Example 1
An embodiment in which coal is used as the carbonaceous raw material 9 in the gasification furnace 1 and nitrogen (furnace wall cooling gas) is used as the cooling medium 11 will be described below using the apparatus shown in FIG.
The gasification furnace has a cylindrical shape with an inner diameter of 0.9 m and a height of 1.1 m. The bottom of the furnace has a slag tap 7 with an inner diameter of 0.15 m, and the circumference is 0.3 m above the furnace bottom. Four gasification burners 2 are provided at equal intervals in the direction. The furnace wall 6 has a furnace wall porous portion 5 made of a refractory having a porosity within a range of 0.25 m above and below the gasification burner 2. The furnace wall porous portion 5 was made of a refractory having an alumina content of 94 wt% and sodium oxide: 6 wt%, and the holes had an inner diameter of 1 mm and intervals of 15 mm. Moreover, the furnace wall 6 was comprised also about parts other than the furnace wall porous part 5 with the same composition as the said refractory.

In the gasification furnace 1, the gasification coal amount is 1250kg / h, the oxygen amount is 820Nm ³ / h, and the gasification furnace pressure is 2.0MPa. As a result, the thermocouple installed on the gasification furnace ceiling (not shown) The temperature measured at was about 1500 ° C.

The alumina contained in the ash in the coal was 18 wt%, but the alumina contained in the discharged granulated slag 14 ash was 27 wt%, indicating that slag was adhered around the slag tap 7. It was confirmed by a camera (not shown) that observes the tap 7. Thereafter, the furnace wall cooling gas (nitrogen) was reduced from 250 Nm ³ / h of the initial state to the same concentration and almost raw coal in the alumina component contained in granulated slag ash was operated to increase to 310 nm ³ / h, It was confirmed that the molten slag was discharged smoothly. After 200 hours of operation, the furnace body was opened and the thickness of the furnace wall porous part 5 was measured. As a result, 60 mm, which was the same as that during construction, could be held together with the slag layer adhering to the refractory surface.

(Comparative Example 1)
Under the same conditions as in Example 1, the furnace wall 6 was not provided with the furnace wall porous portion 5, and gasification was performed in a furnace in which a water-cooled wall was constructed with a refractory of 60 mm. As a result of the operation for 200 hours as in the example, the thickness of the refractory at the height around the gasification burner and the slag layer adhering to the surface was about 6 mm in total, and the melting damage of the furnace wall during the operation was Admitted.

(Comparative Example 2)
Under the same conditions as in Example 1, 250 Nm ³ / h of the furnace wall cooling gas (nitrogen) was passed through the furnace wall porous part 5 and the operation was performed under constant conditions. After the operation for 200 hours as in Example 1, the operation was stopped, and the thickness of the refractory at the gasification burner peripheral height and the slag layer adhering to the surface after opening the furnace was about 20 mm in total, Melting of the furnace wall porous part 5 during operation was observed.

(Example 2)
Gasification furnace operation was performed using the same gasification furnace as in Example 1, and when the amount of furnace wall cooling gas (nitrogen) was changed from 250 Nm ³ / h in the initial state to 260 Nm ³ / h, discharged granulated slag The alumina concentration in the ash decreased to 25 wt%, and operation was possible without slag adhesion around the slag tap. The furnace body was opened after 200 hours of operation, and the thickness of the furnace wall porous part 5 was measured. The thickness of the refractory and the slag layer adhering to the surface at the height around the gasification burner were combined. What was 60 mm at the time was held in a state of about 55 mm.

It is sectional drawing of the gasification apparatus based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gasification furnace 2 Gasification burner 3 Cooling gas inlet 4 Cooling gas flow path 5 Furnace wall porous part 6 Furnace wall 7 Slag tap 8 Water tank for slag granulation 9 Carbonaceous raw material 10 Oxygen-containing gas and steam 11 Cooling medium 12 Cooling Medium 13 Molten slag 14 Granulated slag 15 Generated gas

Claims (3)

  At least the inner wall surface of the furnace wall is formed of a refractory, and a gasification furnace equipped with a furnace wall porous part for introducing the cooling medium from the outside is used, and the oxygen-containing gas is introduced while the cooling medium is being charged. In the gasification method of carbonaceous raw material, where the feed material containing carbonaceous raw material is converted into fuel gas and the residue containing ash is discharged as molten slag, the ash content composition of the feed material before fuel gasification and the discharged melt Compared with the ash composition of slag, the content of at least one of the components constituting the refractory is increased in the amount of the cooling medium when the molten slag is higher. Gasification method.   Furthermore, a basicity adjusting agent composed of a lime component is supplied as a feed material to the gasification furnace, and the basicity of the ash content of the feed material before fuel gasification is adjusted to 0.1 or more and 1.5 or less. The method for gasifying a carbonaceous raw material according to claim 1.   The amount of the cooling medium charged from the furnace wall porous portion is controlled so that the refractory contains 50% or more of alumina by mass% and the alumina concentration in the molten slag ash is 25% by mass or less. The method for gasifying a carbonaceous raw material according to claim 1 or 2, characterized in that:

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