JP2007051181A - Method for recovering sensible heat of coke oven gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering sensible heat of coke oven gas in high efficiency, keeping valuable tar component as it is and preventing the leak of coke oven gas to outer atmosphere. <P>SOLUTION: Coke oven gas is brought into direct contact with DME and/or methanol to decompose the DME and/or methanol with steam existing in the coke oven gas and the sensible heat of the coke oven gas of this state is recovered in the form of chemical energy. The temperature of the coke oven gas in the above process is preferably ≥400°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for recovering the amount of heat of a coke oven gas generated in a coke oven, so-called sensible heat.

  Although the sensible heat of the high-temperature coke oven gas generated from the coke oven is enormous, it is cooled by using the latent heat of water by spraying water, and it is not fully utilized at present. .

  Conventionally, many methods have been proposed to recover the sensible heat of the coke oven gas. For example, Patent Document 1 discloses a method in which a heat exchanger is installed in a high-temperature coke oven gas and the sensible heat of the high-temperature coke oven gas is recovered through an organic heat medium.

  However, the sensible heat recovery method using the heat exchanger disclosed in Patent Document 1 has the following problems. That is, since the high-temperature coke oven gas generated from the coke oven is unrefined and contains fine solids and tar components, the surface of the heat exchanger is covered with these substances, and the heat exchange rate decreases. In addition, the coke oven is operated by several dozen furnaces, and even if a part of the coke oven is stopped, not all the furnaces are completely stopped, so the coke oven gas starts operation. Then, it continues to occur for several decades until the operation is stopped. For this reason, when the heat exchanger becomes dirty, it is usually cleaned, but it is difficult to clean the heat exchanger attached to the coke oven gas.

  On the other hand, in Patent Document 2 and Patent Document 3, by applying a metal such as molybdenum, tungsten, tin or crystalline aluminosilicate on the surface of the heat exchanger that contacts the coke oven gas, the tar content is decomposed. A method for preventing the adhesion of tar content is disclosed.

Patent Document 4 discloses that coke is produced by introducing limestone into a rising pipe portion through which high-temperature coke oven gas passes and producing hydrogen from carbon dioxide gas generated by decomposition of limestone and moisture contained in the coke oven gas. A method of recovering sensible heat of furnace gas and simultaneously recovering and using quick lime generated by decomposition of limestone is disclosed.
Japanese Patent Publication No.59-44346 JP-A-7-188664 JP-A-8-134456 JP 2003-292961 A

  However, in Patent Documents 2 and 3, the tar content contained in the coke oven gas is a graphite electrode for aluminum refining, a negative electrode material for lithium ion secondary batteries, a carbon black raw material for tires, and a polyvinyl chloride plasticizer raw material. Useful components such as naphthalene, which is a raw material for phthalic anhydride, and benzene, which is a raw material for 6-nylon, are included. Decomposing tar content lowers the amount and quality of these products, and socially. Has a big impact.

  On the other hand, in the method using limestone disclosed in Patent Document 4, it is necessary to open the lid on the upper part of the riser pipe in order to put limestone, and it is necessary to open the extraction port in order to take out the generated quicklime. is there. For this reason, when the lid and the outlet are opened, unrefined high-temperature coke oven gas is diffused into the atmosphere, causing environmental pollution. In addition, in order to hold the limestone in the riser, it is necessary to narrow the flow path of the coke oven gas in the riser, which causes the riser to be blocked by tar and carbon contained in the unrefined coke oven gas. .

  In this way, the coke oven gas contains a large amount of sensible heat, but contains fine solids and tar components, so it can be used simply by being cooled by spraying water from the viewpoint of stable operation over the long term. The situation has not been done.

  In view of the above circumstances, the present invention is a coke oven gas sensible heat recovery method that efficiently recovers coke oven gas sensible heat without releasing the coke oven gas to the atmosphere without changing the useful tar content. The purpose is to provide.

  As a result of the present inventors diligently researching to solve the above problems, as a means for recovering the sensible heat of the high temperature coke oven gas, attention is paid to the decomposition reaction of dimethyl ether and / or methanol which is an endothermic reaction, and the coke oven gas It was found that the sensible heat of the coke oven gas can be efficiently recovered by converting the sensible heat of this into chemical energy of the decomposition reaction of dimethyl ether and / or methanol.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] DME and / or methanol is brought into direct contact with coke oven gas, the DME and / or methanol is decomposed by water vapor contained in the coke oven gas, and the sensible heat of the coke oven gas in that state is reduced. A sensible heat recovery method for coke oven gas, which is recovered as chemical energy.
[2] The method for recovering sensible heat of coke oven gas according to [1], wherein the temperature of the coke oven gas is 400 ° C. or higher.

  According to the present invention, sensible heat of high-temperature coke oven gas that has been conventionally cooled only by water and can be recovered in the form of chemical energy can be used to prevent global warming and maintain the environment. Not only has a great effect, it can also contribute greatly to energy saving in coke ovens.

  The present invention converts the sensible heat of coke oven gas into chemical energy by utilizing a reforming reaction, that is, a decomposition reaction of dimethyl ether and / or methanol, which is an endothermic reaction.

  The reforming reaction, that is, the decomposition reaction of dimethyl ether and / or methanol first proceeds according to the following two formulas.

(CH ₃ ) ₂ O + H ₂ O → 2CH ₃ OH (1)
CH ₃ OH → CO + 2H ₂ (2)
Formula (1) is a reaction in which dimethyl ether is hydrolyzed by water vapor contained in the coke oven gas, and 2 moles of methanol are produced per mole of dimethyl ether. Formula (2) is a reaction in which methanol is decomposed, and synthesis gas that is a mixture of carbon monoxide and hydrogen is generated. These two reactions are endothermic reactions, and the amount of heat of 5.7 kcal per mole of dimethyl ether is absorbed by the reaction of the formula (1). On the other hand, the amount of heat of 21.7 kcal per mole of methanol is absorbed by the equation (2).

  Furthermore, the methanol produced | generated by (1) Formula produces | generates the synthesis gas which is a mixture of carbon monoxide and hydrogen next by (2) Formula. That is, the decomposition reaction of dimethyl ether is the reaction shown in the formula (3), and an amount of heat of 49.0 kcal is absorbed per mole of dimethyl ether.

_{(CH 3) 2 O + H} 2 O → 2CO + 4H 2 (3)
Furthermore, the carbon monoxide produced | generated by reaction of the said (3) type | formula may produce the water gas shift reaction of (4) type | formula further with water.

CO + H ₂ O → CO ₂ + H ₂ (4)
The reaction of formula (4) is an exothermic reaction of 9.8 kcal per mole of carbon monoxide, but the overall reaction formula when this reaction occurs is as shown in the following formula (5). It becomes an endothermic reaction of 29.3 kcal, and it becomes possible to recover sensible heat at the same time as cooling the gas.

_{(CH 3) 2 O + 3H} 2 O → 2CO 2 + 6H 2 (5)
According to the equilibrium calculation, the reaction of the formula (5) is almost completely biased toward the product side at a temperature of 250 ° C. or higher. However, the substantial reaction does not proceed without the catalyst. It is known that the reaction proceeds almost completely at a temperature of 300 to 350 ° C. when a catalyst is used. The catalyst active in this reaction is a metal catalyst or a metal oxide catalyst, and in particular, a metal catalyst or metal oxide catalyst using copper that is extremely weak against hydrogen sulfide is said to have high activity. However, since the coke oven gas contains a large amount of hydrogen sulfide derived from coal as a raw material, these catalysts cannot be used directly. For the above reason, as a result, the cooling of the coke oven gas by the formulas (3) and (5) has not been conventionally performed.

Therefore, the present inventor has fully considered the above situation, and conducted careful consideration and earnest research.
Nitrogen was bubbled into room temperature water, saturated, mixed with dimethyl ether and passed through an empty ceramic cylindrical reactor maintained at a predetermined temperature. The flow rate of nitrogen was fixed at 500 cc per minute in the standard state. Further, dimethyl ether was made equal to the water vapor flow rate. The reaction product produced as described above was analyzed by gas chromatography. The obtained results are shown in Table 1.

  From Table 1, it can be seen that dimethyl ether completely disappeared by the reaction and carbon monoxide was produced in a high yield.

  As a result, by directly injecting dimethyl ether and / or methanol into a high-temperature coke oven gas, the reaction of the equations (2), (3) and (5) proceeds without making a catalyst essential, and the coke oven It has been found that the gas is cooled, and the present invention has been completed.

  Since the reforming reaction of dimethyl ether first proceeds from the hydration reaction of dimethyl ether as shown in the formula (1), it requires equimolar moisture with dimethyl ether. Further, in the case where the water gas shift reaction of the formula (4) proceeds, twice the amount of water is required with respect to dimethyl ether. That is, the total amount of water is 3 times that of dimethyl ether. As the water necessary for these reactions, the water contained in the coke oven gas can be used. If the moisture contained in the coke oven gas is insufficient to decompose dimethyl ether and / or methanol, it can be supplemented separately. Carbon monoxide and hydrogen generated by the reforming reaction of dimethyl ether are originally contained in the coke oven gas and can be used as fuel as they are. In addition, the supply amount of dimethyl ether and / or methanol can be freely selected, and the supply amount of dimethyl ether and / or methanol is determined based on the moisture amount necessary for the decomposition in consideration of the moisture in the coke oven gas. You can also. However, even if dimethyl ether or methanol remains, the cooling effect is reduced, but it can be used as a fuel as it is. Therefore, in the present invention, the amount of dimethyl ether and / or methanol supplied is the amount of water or carbon dioxide in the coke oven gas. It is not limited by the amount of gas.

  Further, when dimethyl ether and / or methanol is directly blown into the coke oven gas, both dimethyl ether and methanol may be liquid or gaseous. Although dimethyl ether is a gas at normal temperature and pressure, it easily becomes a liquid when pressurized or cooled, and is normally stored under pressure by being pressurized. Therefore, blowing in liquid is advantageous in terms of the process. The storage pressure of dimethyl ether is about 0.7 to 0.8 MPa, depending on the ambient temperature, and is sufficiently high relative to the pressure of the coke oven gas. It is possible to blow into the furnace gas, which is further advantageous in this respect. On the other hand, since methanol is in a liquid state at normal temperature and pressure, it is advantageous to blow it in a liquid state. As described above, both dimethyl ether and methanol can be blown in liquid form, and the vaporization heat can be used for cooling the coke oven gas by blowing in liquid form. Therefore, sensible heat recovery of coke oven gas is possible. Efficiency is even better.

  Further, dimethyl ether and methanol may be used alone or in combination. The mixing ratio is also completely arbitrary and can be appropriately selected depending on the economic situation and the process status. Furthermore, dimethyl ether has two general production methods: a direct method of producing dimethyl ether directly from synthesis gas, and an indirect method of producing methanol once and further producing dimethyl ether. In any case, the reaction route is produced via methanol, and since the dimethyl ether before purification contains methanol, the production method of dimethyl ether to be used is not limited. In the method of the present invention, since dimethyl ether and methanol can be arbitrarily mixed, the above-mentioned dimethyl ether before purification can be used in the same manner.

  Various methods can be employed for blowing dimethyl ether and / or methanol into the coke oven gas. Liquid dimethyl ether and / or methanol may be sprayed into the coke oven gas using a spray nozzle or the like, or dimethyl ether and / or methanol may be gasified with a heater and mixed with the coke oven gas. It is also possible to simply mix dimethyl ether and / or methanol in a liquid state. However, among the above, since the heat of vaporization of dimethyl ether and / or methanol can be efficiently used for sensible heat recovery of high-temperature coke oven gas, the method of blowing in the above-mentioned mist form is the most efficient, and liquid dimethyl ether and / or Methanol is preferably blown into the coke oven gas in the form of a mist.

  In addition, dimethyl ether and / or methanol is a simple method to be blown into the coke oven rising pipe, but can also be blown into the upper portion of the coke oven. In this case, for example, it is necessary to make a hole in the brick of the coke oven and pipe it. However, since the upper part of the coke oven can be cooled, the effect of suppressing coking to the ceiling in the furnace is expected. it can.

  The temperature of the coke oven gas to be contacted with dimethyl ether and / or methanol is preferably 400 ° C. or higher, and more preferably 700 ° C. or higher. When the temperature is lower than 400 ° C., the thermal decomposition rate of dimethyl ether and / or methanol is slow, which is not preferable. On the other hand, there is no upper limit of the temperature of the coke oven gas according to the present invention. In general, the temperature of the coke oven gas is at most about 1,100 to 1,200 ° C., and there is no problem in applying the present invention.

  In the dust generated at the time of producing coke, there may be a mixture of components that exhibit catalytic action on the above formulas (1) to (5). In this case, the thermal decomposition action and the catalytic action occur simultaneously, and the reactions of the above formulas (1) to (5) proceed more rapidly, so that the present invention is more effectively exhibited and preferable. In addition, in order to use the catalytic action together, it is possible to add a substance that becomes a catalyst. However, unrefined coke oven gas contains hydrogen sulfide, and a substance that becomes a metal or metal oxide catalyst is often poisoned by this hydrogen sulfide. Therefore, when using a metal or metal oxide as a catalyst, it should be performed while confirming the effect.

  When dimethyl ether and / or methanol is mixed with the coke oven gas according to the present invention, the temperature of the coke oven gas decreases due to the decomposition reaction of dimethyl ether and / or methanol. At this time, when the temperature of the coke oven gas is less than 400 ° C., the reforming reaction or reduction reaction of dimethyl ether and / or methanol hardly proceeds. Therefore, the lower limit of the temperature decrease due to the sensible heat recovery of the coke oven gas is preferably set to 400 ° C. However, in the case where a substance having the above-described catalytic action exists, the reaction proceeds sufficiently even at a temperature of 400 ° C. or lower, and this is not limited.

  In general, when a treatment such as desulfurization is performed, the coke oven gas is cooled to 100 ° C. or lower. In this case, after applying the present invention, cooling to 100 ° C. or less may be performed by a conventional method, for example, cooling with water.

  FIG. 1 is a diagram showing an embodiment of the present invention. In FIG. 1, the high-temperature coke oven gas generated inside the coke oven 1 passes through the riser 2 and is cooled by the low water supplied from the low water supply equipment 3 through the low water nozzle 4. The cooled coke oven gas is collected through the dry main 5 and sent to a coke oven gas purification facility (not shown). Here, a DME nozzle (or methanol nozzle) 6 for introducing dimethyl ether and / or methanol is attached to the lower part of the ascending pipe 2. Then, dimethyl ether and / or methanol is supplied from the DME nozzle or methanol supply equipment 7 through the DME nozzle (or methanol nozzle) 6 into the ascending pipe 2.

In FIG. 1, dimethyl ether was charged from the DME nozzle 6 at a rate of 190 kg / hr with respect to the coke oven gas at 850 ° C. generated at a rate of 4500 Nm ³ / hr. After charging dimethyl ether, the coke oven gas temperature dropped to 710 ° C. Dimethyl ether was not detected in the produced coke oven gas. Moreover, the carbon monoxide in the product gas increased at 90 Nm ³ / hr. From these results, the conversion rate of dimethyl ether is 100%, the yield of carbon monoxide is 96%, DME and / or methanol is efficiently decomposed, and the sensible heat of coke oven gas is efficiently recovered as chemical energy. You can see that

  Since the present invention can recover the sensible heat of coke oven gas in the form of chemical energy, it is useful as various sensible heat recovery methods including sensible heat recovery of coke oven gas.

It is a figure which shows one embodiment of this invention. Example 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coke oven 2 Rising pipe 3 Aqueous water supply equipment 4 Aqueous water nozzle 5 Dry main 6 DME nozzle (or methanol nozzle)
7 DME nozzle or methanol supply equipment

Claims (2)

  The DME and / or methanol is brought into direct contact with the coke oven gas, the DME and / or methanol is decomposed by water vapor contained in the coke oven gas, and the sensible heat of the coke oven gas in this state is converted into chemical energy. Coke oven gas sensible heat recovery method, characterized in that   Coke oven gas temperature is 400 degreeC or more, The sensible heat recovery method of the coke oven gas of Claim 1 characterized by the above-mentioned.

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