JPS5918394A - Heat transfer pipe for recovering heat of cokes lifting pipe - Google Patents

Abstract

PURPOSE:To improve the coefficient of thermal conductivity of a heat transfer pipe by a method wherein a heat transfer pipe is formed of silicon carbide utilizing lining as aggregate and carbon powder, metallic silicon powder as bonding agent. CONSTITUTION:A cokes oven gas 1 is introduced from a carbonizing chamber 2 to a header pipe 4 through a cokes lifting pipe 3 while heating medium circulates in a heat transfer pipe 7 arranged halfway up the pipe 3 and a heat exchanger 8 externally provided by means of a circulating pump 5 and a circulating pipe 6. The heat transfer pipe 7 is made of a heat transfer jacket 10 circulating the heat transfer medium 9 and a lining material 12 connected to the inner wall of the jacket 10 through the intermediary of silicon carbide mortar 11. The lining material made of silicon carbide, carbon powder and metallic silicon powder may realize high coefficient of thermal conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat transfer tube disposed on the inner wall of a coke oven riser tube in order to effectively recover sensible heat of coke oven generated gas (hereinafter referred to as coke oven J5 gas) in the riser tube.

The coke oven gas generated by carbonization is collected in the Herator tube via the riser pipe above the coke oven.
It is sucked in with a blower, refined to remove impurities, and then used as fuel for factories or as city gas.

In recent years, many attempts have been made to recover the sensible heat generated in coke ovens from the standpoint of energy conservation and effective use of waste heat. The inventors also have a precedent, Japanese Patent Application No. 53-114399.
No., JP-A-55-40736 [Method for recovering heat from coke oven gas] disclosed an invention for a method for recovering sensible heat in a riser pipe section. The gist of this is a heat recovery method that connects a heat exchanger to a heat transfer tube disposed on the inner wall of a riser pipe and recovers sensible heat via an organic heat medium. The present invention relates to a heat exchanger tube suitable for the method of the invention.

In order to recover heat efficiently in the riser pipe section, it is necessary to have both the original function as a riser pipe and the function as a heat exchanger, but this has traditionally been a problem with riser pipes. 1) Tar and carposis in coke oven gas adhere to the inner wall of the riser pipe, causing a narrowing, so-called carposi adhesion.

11) Since the temperature of the inner wall of the riser tube is subjected to a temperature cycle of about 600C to 1200C during coke oven operation, the inner wall of the riser tube is subjected to thermal shock and thermal fatigue loads.

111) Repeated redox reaction with coke oven gas,
Or be corroded by condensed chemical liquid.

etc. In addition to solving these technical problems, the riser pipe must also improve its heat transfer coefficient in order to achieve its function as a heat exchanger.

is important.

In order to solve the above technical problems 11) and 111), the inner surface of a steel riser pipe has conventionally been lined with solid bricks or studs. Furthermore, in recent years, linings have been made of fused silica bricks and the like.

However, the current situation is that these rhinestone materials are by no means satisfactory in terms of the technical problem i) above, as they require constant carbon removal work. In addition, these licorice materials have a thermal conductivity of approximately 2.
It is not preferable for the heat exchanging performance (1) above because it is low, less than kcat/m-b-c, and carbon tends to adhere.

The present inventors have repeatedly conducted various research and development on heat exchanger tubes that have solved all of the above technical problems, and have found that the silicon carbide content is approximately 70% by weight or more and the thermal conductivity is 9 kca/-/1.
It has been found that it is most effective to use silicon carbide bricks with a bending strength of 200 kg/crn2 or more at 12.00C as the inner wall liner material.

As is well known, silicon carbide has high thermal conductivity, low coefficient of thermal expansion, excellent thermal shock resistance, low chemical reactivity to various atmospheres and chemicals, and high emissivity. Silicon carbide bricks containing a large amount of silicon carbide generally exhibit these characteristics depending on the content, density, and bond strength.

The silicon carbide brick used as the lineage material for the inner wall of the heat exchanger tube has a low thermal conductivity when the silicon carbide content is less than 70% by weight.
It has a low emissivity and is susceptible to thermal shock from coke oven gas, resulting in chemical corrosion that is not much different from conventional bricks.

Even if the silicon carbide content is 70% by weight or more, sufficient heat transfer ability cannot be obtained if the thermal conductivity is less than 9 kca4/mh-C, and the bending strength at 1200G is 200%.
If it is less than k17/lri, the mechanical properties will be insufficient, such as cracking or breaking when removing the strong carposi formed on the inner surface.

Next, each material necessary for manufacturing the heat exchanger tube of the present invention will be explained.

The heat exchanger tube for heat recovery of the present invention uses silicon carbide particles as the aggregate, and uses carposi powder, metallic silicon powder, and other binders such as tar and pitch as the binding member. It is made by mixing raw materials, molding them using a vibration molding machine, etc., and firing them in a non-oxidizing atmosphere.

It is preferable to use silicon carbide in an amount of 7 Gt or more by weight, and to adjust the particle size so as to improve the filling properties of the molded product. If the silicon carbide content is less than 70% by weight, desired thermal conductivity and emissivity cannot be obtained, and the heat transfer effect is insufficient. In addition, if it is more than 95%, the moldability of the mixture will deteriorate, and as a result, in the case of large-diameter, thin-walled and large molded height dimensions such as heat exchanger tubes, the molding filling degree will be high throughout the upper, middle, and lower parts of the heat exchanger tube. Carposi powder and metallic silicon powder, which tend to have unevenness and are difficult to mold, each have a weight of 3.
Use ~15%. What is Carposi powder and metallic silicon powder?
By blending them together, silicon carbide can be generated during firing or use, thereby increasing the strength of the heat recovery heat exchanger tube.

In addition to the above-mentioned carbon powder, carbonized components from tar, pitch, etc. are added to the carposi as a source for producing silicon carbide, but the carbon powder used for producing silicon carbide and the metallic silicon powder are used in approximately the same weight. If the weight of both the carposi powder and the metal silicon powder is less than 3 inches, the strength of the heat recovery heat exchanger tube will be insufficient. In addition, if both are 15% or more, if Stc is formed by the reaction of St and C, there will be problems such as a decrease in volume, a higher firing shrinkage rate, and a higher porosity of the fired product. There is something that I don't like. Barposi powder and metal silicon powder have a 0.05
It is preferable to use one having a diameter of mm or less. As the carposi powder, powders such as scaly graphite, artificial graphite, earthy graphite, coke anthracite, and carposi lac can be used. Next, each of these raw materials is thoroughly mixed with other binders such as teril, pitch, phenolic resin, lignidium, and clay. Other binders are fired and remain as part of the bonding member, but their purpose is to be added as a forming aid necessary for forming the heat exchanger tube, so the amount added may be changed as appropriate depending on the type of binder. do. Taking as an example the case where lignidium and clay are used together, it is preferable that the amount is about 5 to 7% by weight. The mixture is molded into a motion molding machine or the like to mold a desired cylindrical heat exchanger tube. Since heat exchanger tubes are constantly heated and cooled rapidly, they are particularly required to have excellent sporicity resistance.

For this reason, it is necessary not only to use raw materials that have excellent scratch resistance and 7/7 properties, but also to use an appropriate molding method to obtain a homogeneous molded product.

For this reason, various methods of molding were devised, and as a result, a molding method using a vibration molding machine or the like was suitable.

The molded article is then fired in a non-oxidizing atmosphere in a conventional manner. By using the above manufacturing method, the thermal conductivity is OK ca
t/mh-C or higher bending strength at 1200C is 200
It was possible to obtain a desired heat exchanger tube with a yield of more than kg/J.

Next, the effects of the riser tube using the heat exchanger tube of the present invention will be explained based on examples.

FIG. 1 is a flow diagram of the heat recovery method. The coke oven nozzle 1 is guided from the carbonization chamber 2 of the coke oven through the riser pipe 3 to the herator tube 4, and the heating medium is circulated through the circulation positive 5 and the circulation J\izu 6.
The heat is circulated between the heat exchanger tube 7 disposed in the middle of the riser pipe and the heat exchanger 8 disposed outside.

FIG. 2 is a detailed explanatory diagram of the heat exchanger tube 7. The heat transfer tube was composed of a heat transfer tube that circulates a heat medium 9 and a heat transfer tube of /15 get 10 and line material 12, and had a total length and height of 2900 mm. For the three types of lineage materials shown in Table 1, heat transfer tubes were installed in three riser tubes each, and a continuous operation test was conducted for about one year.

The material in the table is the silicon carbide lining material of the present invention, and B and C are comparative products.

B is a material with a silicon carbide content of 60%, 7%, and C? -1 It is a fused silica lineage material.

Table 2 shows the test operating conditions, representative recovery M intervals, and heat transfer analysis results.

During the initial 30 days of the test, the collection performance of Rainijizu B was about the same as that of Rainijizu A, but gradually its performance began to decline, and the performance became equivalent to that of Rainijizu C. When we attempted to remove carbon from the inner wall as usual for conventional riser pipes without heat exchanger tubes, we found that the degree of adhesion was smaller on Line A and B and O than on conventional riser tubes. Compared to the usual carposi removal work, it was easier to do. This is thought to be due to the fact that Linin'21 did not form any reactants with the atmospheric gas, making it difficult to develop adhesion strength, and the large temperature difference on the surface of the linen.

For Linin JjB and C, there is a difference between the actual measured value and the calculated value due to the effects of carposi adhesion, etc., whereas for Linin A, there is no performance deterioration due to carposi adhesion, etc., as shown in Table 2. Therefore, the measured values and calculated values almost match. In addition, the heat transferred by convection and conduction on the surface of the heat exchanger tube accounts for about 60 cm, and the heat transferred by radiation accounts for about 40 cm, indicating that the effects of high thermal conductivity and commercial emissivity in Rhineshik A are large. This shows that

As described above, although the silicon carbide heat exchanger tube of the present invention is intended for heat recovery, it reduces the work of removing carposis.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram of the heat recovery method, and FIG. 2 is a sectional view of the heat exchanger tube.

Claims (1)

[Claims] By weight, 70-95% silicon carbide as aggregate, 3-15% carposi powder and 3-15% silicon metal powder as bonding member.
H. A heat transfer tube for heat recovery in a coke oven riser tube, characterized in that the remainder of the other binder is mixed, molded, and fired.