JP6098765B2 - Method of injecting pulverized coal into oxygen blast furnace - Google Patents

Description

  The present invention relates to a method for blowing pulverized coal into an oxygen blast furnace that generates pure blast furnace gas containing no nitrogen from the top of the furnace by blowing pure oxygen and pulverized coal from a tuyere.

An oxygen blast furnace generally generates and recovers blast furnace gas containing no nitrogen (hereinafter also simply referred to as “nitrogen-less blast furnace gas”) from the top of the furnace by blowing pure oxygen and pulverized coal as a reducing material from the tuyere. Known as a blast furnace. The nitrogen-less blast furnace gas can be used as a raw material for the synthetic chemical industry. In this oxygen blast furnace operation, it is necessary to operate the temperature in the combustion region of the tuyere (feather tip temperature) at a high temperature of 2000 ° C. to 2600 ° C. As a prior art for that purpose, for example, Patent Document 1 proposes a method of controlling the temperature of the tuyere tip within a predetermined temperature range by blowing high-temperature furnace top gas containing CO ₂ from the tuyere.

  In addition, as a conventional operation example of an oxygen blast furnace, there is a method in which pure oxygen, pulverized coal, and heavy oil are blown from a tuyere (see Patent Document 2). Furthermore, as another conventional operation example of the oxygen blast furnace, there is a proposal to use a pulverized coal whose combustibility is improved when pure oxygen and pulverized coal are blown from a tuyere (see Patent Document 3). Furthermore, Patent Document 4 proposes an operation method in which pure oxygen is preheated to increase the amount of pulverized coal blown (see Patent Document 4).

JP 60-159104 A JP-A-63-171807 JP 63-166914 A JP-A 63-169310

  In the prior art described in the above-mentioned Patent Documents 1 to 3, blown pure oxygen and pulverized coal are used at room temperature. However, in these prior arts, in order to increase the temperature of the tuyere tip combustion region (tuyere tip temperature) to a high temperature of 2000 ° C. to 2600 ° C., the igniting of the pulverized coal to be blown is accelerated to improve the combustibility. . However, in order to realize early ignition of pulverized coal, it is necessary to raise the temperature of the pulverized coal to a certain temperature or higher. On the other hand, as a method for satisfying the requirement, for example, Patent Document 4 proposes a method of preheating with pure oxygen.

  However, in order to preheat with pure oxygen, a pure oxygen preheating facility is required separately. In addition, regarding the technique disclosed in Patent Document 4, exhaust heat is used as a heat source for the preheating facility. However, in an actual blast furnace, it is difficult to procure such exhaust heat in the vicinity of the blowing facility.

  An object of the present invention is to propose an effective method for efficiently generating nitrogen-less blast furnace gas useful as a gas for synthetic chemical industry by using a pulverized coal that is preferable as pulverized coal to be blown into an oxygen blast furnace.

The inventors have intensively studied to overcome the above-mentioned problems of the prior art and to realize the object. As a result, the inventors have developed the present invention according to the following summary configuration. That is, the present invention generates a blast furnace gas that does not contain nitrogen by blowing pulverized coal together with pure oxygen from the tuyere and performs the pulverized coal blowing operation on the oxygen blast furnace that is recovered from the top of the furnace. This is a method of injecting pulverized coal into an oxygen blast furnace with a content of 25 mass% or more (excluding volatile content of 33.4 mass%) .

Further, the present invention according to the above configuration further includes
(1) Use pure oxygen and pulverized coal blown from the tuyere at room temperature;
(2) The volatile content of the pulverized coal is 30 mass% or less,
(3) The amount of pulverized coal blown in (PCR) is 200 kg or more per 1 ton of hot metal,
It can be considered that a more preferable solution can be provided.

  According to the method of injecting pulverized coal into the oxygen blast furnace according to the present invention, by using high volatile content pulverized coal having a volatile content of 25 mass% or more as pulverized coal, the amount of pulverized coal injected can be reduced without a preheating device or its heat source. You can increase it. In addition, according to the present invention, by using a pulverized coal that is preferable as pulverized coal blown from the tuyere, the temperature in the combustion area before the tuyere of the oxygen blast furnace can be easily and quickly increased. Thus, nitrogen-free blast furnace gas can be efficiently generated and recovered, which leads to stable supply of synthetic chemical industry gas.

It is a basic diagram which shows an example of the oxygen blast furnace to which the pulverized coal blowing method of this invention is applied. It is a basic diagram which shows an example of the pulverized-coal combustion test furnace for measuring the combustion rate of pulverized coal under the conditions in which pure oxygen and pulverized coal are blown into the oxygen blast furnace. It is a graph which shows an example of an experimental result. It is a graph which shows the other example of an experimental result.

  FIG. 1 is a diagram showing an example of an oxygen blast furnace and its peripheral equipment used in the pulverized coal blowing method according to the present invention. In the configuration shown in this figure, 1 is an oxygen blast furnace, 2 is a mixer for mixing coke oven gas (C gas) and blast furnace gas (B gas) to obtain a mixed gas (M gas), and 3 is the above M Burner for preheating gas and blowing it into the furnace, 4 is a generator for generating electricity using blast furnace top exhaust gas, 5 is an oxygen plant for producing pure oxygen, and 6 is for blowing oxygen or the like into the oxygen blast furnace 1 The tuyere to use.

  In the configuration shown in FIG. 1, as in the conventional blast furnace, in the oxygen blast furnace 1, sintered ore and coke are introduced from the top of the furnace. Also, room temperature pure oxygen is blown into the furnace from the lower tuyere 6. Pure oxygen is produced from air in the oxygen plant 5 using a separation technique such as cryogenic separation, and consumes electric power at that time. Therefore, a method is used in which power is generated by the generator 4 using C gas, B gas, which is a combustion gas containing a large amount of CO, or M gas obtained by mixing these gases, and pure oxygen is produced using the generated power. In addition, from the tuyere 6 at the bottom of the blast furnace, tuyere blowing gas such as pulverized coal, natural gas, and coke oven gas is blown together with pure oxygen.

  One of the features of the pulverized coal blowing method into the oxygen blast furnace according to the present invention is that the volatile content of the pulverized coal blown together with pure oxygen from the tuyere is 25 mass% or more. The reason is as follows.

  In the case of a conventional blast furnace, pulverized coal is used as the blowing reducing material, and its volatile content is about 20 mass%. This level of volatile matter is classified as so-called low volatile coal (see, for example, Japanese Patent Application Laid-Open No. 2003-286511). Now, in such a low volatile matter pulverized coal, since coal occupies most of weight, it is thought that more coke can be reduced than the highly volatile coal of 25 mass% or more with the same blowing amount.

  By the way, an oxygen blast furnace generally has no equipment or heat source for preheating oxygen. Therefore, normal oxygen and pulverized coal are used. Therefore, in the case of this furnace, pulverized coal passing through the raceway (the tuyere tip combustion zone, the temperature is maintained at a high temperature of 2000 ° C. or higher and the diameter is about 1 m) in which the coke is swirling. If the air is blown at a speed of 200 m / s, the time required to pass this raceway is several milliseconds. Therefore, it is preferable that the pulverized coal is ignited as early as possible before entering the raceway.

  In this regard, in the case of the conventional oxygen blast furnace, since the pulverized coal with a low volatile content is blown in, the temperature is not sufficiently increased until the pulverized coal reaches the raceway. Therefore, in order to induce early ignition and combustion, an oxygen preheating device as described in Patent Document 4 is inevitably required. On the other hand, when pulverized coal with a high volatile content and a high volatile content is blown in as in the present invention, ignition becomes much easier than with a pulverized coal with a low volatile content. In particular, in an oxygen blast furnace such as the present invention in which pre-heating of blown oxygen is not performed, it is desirable to blow high volatile matter pulverized coal, that is, pulverized coal having a volatile content of 25 mass% or more. The upper limit of the volatile content is not particularly limited, but is preferably about 30 mass% or less.

  In the present invention, the reason why the volatile content is limited to 25 mass% or more is that, as can be seen from the examples described later, early ignition-combustion of pulverized coal can be achieved, and a high substitution rate can be obtained. The reason why it is preferable to set the volatile content to 30 mass% or less is that the substitution rate is still higher than that of the conventional blast furnace as shown in the examples to be described later. It is for showing.

  In the present invention, the high volatile matter pulverized coal is, for example, mixed with a predetermined amount of a relatively low volatile matter pulverized coal from North America and a relatively high volatile matter pulverized coal such as from Australia or the United States. A component prepared at a fraction of 25 mass% or more, preferably about 30 mass% or less is used.

  FIG. 2 is a diagram showing an example of a pulverized coal combustion test furnace that measures the combustion rate of pulverized coal under conditions of injecting pure oxygen and pulverized coal into an oxygen blast furnace. This pulverized coal combustion test furnace 11 is 1400 mm high × 1000 mm long × 400 mm wide. In addition, a cyclone 13 is provided on the upper part of the pulverized coal combustion test furnace 11 via a pipe 12, and combustion gas generated in the furnace is separated into exhaust gas and dust by the cyclone 13. An upper portion of the test furnace 11 has a pipe line 14 connected to a coke storage tank 15 so that the coke 16 stored in the coke storage tank 15 can be loaded into the test furnace 11. It has become. Further, the test furnace 11 is provided with a measurement probe 17 for measuring temperature, pressure, gas composition, and the like on the side surface thereof, and a tuyere 18 is provided on the side of the furnace substantially opposite to the measurement probe 17. Further, the tuyere 18 is provided with a blow pipe 19. The blow pipe 19 is provided with a pure oxygen blowing lance 20 for blowing pure oxygen, a pulverized coal blowing lance 21 for blowing pulverized coal, an observation hole 22 and the like. Reference numeral 23 denotes a raceway which is a combustion zone in front of the tuyere 18.

  Using the pulverized coal combustion test furnace 11, the combustion rate of pulverized coal simulating the blowing conditions of an oxygen blast furnace was measured. In this combustion test equipment that reproduces an oxygen blast furnace, it is difficult to measure the combustion rate by direct sampling of pulverized coal because of the high temperature, so (coke consumption / pulverized coal injection amount) is defined as the substitution rate, and pulverized coal The burning rate of was measured indirectly. When the pulverized coal combustion rate decreases, the residual oxygen increases and the coke consumption increases, so the replacement rate decreases.

  Here, the temperature of the blown gas is 1000 ° C., which is the same as that in the conventional blast furnace, and the room temperature in the oxygen blast furnace according to the present invention. The amount of pulverized coal (PCR) is the same as that in the conventional blast furnace. The oxygen blast furnace condition according to the invention was set to an amount corresponding to 150 kg per 1 ton of hot metal. In the conventional blast furnace conditions, the oxygen concentration in the pulverized coal blowing gas was 25%, and in the oxygen blast furnace conditions according to the present invention, the pulverized coal blowing gas was 100% oxygen gas.

FIG. 3 shows the experimental results. From the result shown in this figure, in the example of the conventional normal blast furnace, the substitution rate decreases as the volatile content increases at a volatile content of 15 mass% or more. This is because the amount of carbon in the pulverized coal is relatively reduced by the increase in the volatile content. Although pulverized coal is less expensive than equal-weight coke, the low substitution rate has low cost merit, and the reducing material ratio, which is the sum of the coke ratio and pulverized coal ratio, is increased. In particular, it is not preferred because it increases CO ₂ emissions.

  On the other hand, under the oxygen blast furnace conditions according to the present invention, it can be seen that the substitution rate gradually increases when the volatile content is 15 mass% or more, and exceeds the substitution rate of the conventional blast furnace operation example at 25 mass% or more. Further, when the volatile content is 25 to 30 mass%, a substantially constant good substitution rate is shown. However, when it exceeds 30 mass%, it is better than the substitution rate of the conventional example, but the substitution rate slightly decreases. The reason for this is thought to be that in blast furnaces, pulverized coal should naturally burn easily in pure oxygen, but low volatile pulverized coal is ignited late at room temperature, resulting in a lower substitution rate. On the other hand, in the case of the high volatile matter as in the present invention, even if it is used at room temperature, the volatile matter becomes an ignition source, so that the substitution rate is increased because it is ignited early.

  Furthermore, FIG. 4 shows the experimental results when both the conventional blast furnace conditions and the oxygen blast furnace conditions according to the present invention have an amount of pulverized coal injection (PCR) equivalent to 200 kg per 1 ton of hot metal. Compared with the experiment corresponding to 150 kg per 1 ton of hot metal shown in FIG. 3, it can be seen that while the conventional example is reduced by 5 to 3%, in the present invention, the maximum is only about 2%. This is because, in the conventional method, the amount of oxygen necessary for the combustion of pulverized coal is relatively lowered and the ignitability is deteriorated, whereas in the present invention, since the ignition is determined by the amount of volatile matter, the decrease in the substitution rate is suppressed. Conceivable.

  Thus, in the experiment using the oxygen blast furnace test furnace conducted by the inventors, it is preferable to use pulverized coal having a higher volatile content, particularly pulverized coal having a volatile content of 25 mass% or more as the blown pulverized coal. I was able to confirm.

  The pulverized coal blowing method according to the present invention described above is not only an oxygen blast furnace using high volatile pulverized coal having a volatile content of 25 mass% or more as pulverized coal, but also a nitrogen-less blast furnace gas useful as a synthetic chemical industry gas. The present invention can be applied to various uses that require technology for promoting the occurrence.

DESCRIPTION OF SYMBOLS 1 Oxygen blast furnace 2 Mixer 3 Burner 4 Generator 5 Oxygen plant 6 Tuyere 11 Pulverized coal combustion test furnace 12, 14 Pipe line 13 Cyclone 15 Coke storage tank 16 Coke 17 Measuring probe 18 Tuy 19 Blow pipe 20 Pure oxygen blowing lance 21 Pulverized coal blowing lance 22 Observation hole 23 Raceway

Claims (4)

When pulverized coal is blown into the oxygen blast furnace to generate nitrogen-free blast furnace gas by blowing pulverized coal together with pure oxygen from the tuyere, the volatile content of the pulverized coal is 25 mass% or more ( However, a method for injecting pulverized coal into an oxygen blast furnace characterized in that the volatile content is 33.4 mass%) .   The method for injecting pulverized coal into an oxygen blast furnace according to claim 1, wherein the pure oxygen and the pulverized coal injected from the tuyere are those at room temperature.   The method for injecting pulverized coal into an oxygen blast furnace according to claim 1 or 2, wherein the volatile content of the highly volatile pulverized coal is 30 mass% or less.   The method for injecting pulverized coal into an oxygen blast furnace according to claim 1 or 2, wherein the amount of pulverized coal (PCR) is 200 kg or more per 1 ton of hot metal.

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