JPS59217792A - Recovery of waste heat of coke oven and its device - Google Patents

Abstract

PURPOSE:To recover simultaneously a carbonized gas of coke oven and sensible heat of red-hot coke, by joining a preheated waste combustion gas of coke oven with a gas whose temperature is raised by cooling red-hot coke, burning the gases , recovering the sensible heat of the gases by a boiler. CONSTITUTION:A low-temperature waste combustion gas of is preheated by the sensible heat of the high-temperature carbonized gas B of the coke oven 1, and the gas A is introduced to the circulating system 22 of a dry-type quenching device for coke. The gas A is then joined with a gas which is sent to the cooling column 17 to cool red-hot coke in the column and has rise in temperature. The gases are burnt by the catalytic combustor, and the sensible heat of the gases with raised temperature containing the combustion gas is recovered by the boiler 19.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coke oven waste heat recovery method and apparatus, and in particular, the sensible heat of coke oven carbonization gas is recovered by coke oven combustion waste gas, and the sensible heat is used in subsequent coke dry extinguishing equipment. This waste coke oven waste gas is supplied to the heat recovery system of the coke oven, and the waste heat from the coke oven (coke oven combustion waste gas, coke oven carbonization gas, and sensible heat of red-hot coke) can be recovered simultaneously in one system. The present invention relates to a heat recovery method and device.

Conventionally, among the waste heat from coke ovens, sensible heat recovery for red-hot coke through dry extinguishing has been widely practiced.
Currently, equipment costs are relatively high and profitability as heat recovery equipment is low. This may be because coke oven combustion waste gas has a low temperature of 150 to 250℃ at the coke oven outlet, has a lower calorific value than sintering equipment main exhaust gas or hot blast furnace combustion waste gas, and has little utility value on its own. , which used to be discarded without any heat recovery. In addition, the temperature of carbonized gas (coke oven gas) in a coke oven is 60% at the coke oven outlet.
0 to 800℃, and 900 to 1,000℃ for converter gas (
However, although it is lower than the radiant gas, it has a higher calorific value than the converter gas, making it a good candidate for heat recovery. However, coke oven gas contains tar etc.94
If the coke oven is cooled to a temperature below 00 to 450°C, the coke gas will condense and adhere to the inner wall of the riser pipe, which is not favorable for the operation of the coke oven, and it has been considered difficult to recover sensible heat from the coke oven gas.

Recently, a technology has been disclosed to recover sensible heat from coke oven gas and use it to control the humidity of coking coal (Japanese Unexamined Patent Publication No. 57-10018).
(No. 4 and No. 57-100185), however, it is limited to heat recovery in a temperature range that is low enough to condense tar, so there is no room for it alone as a drying heat source, and the recovery temperature of the heat medium is The temperature is as low as 250°C, and conversion to steam or electricity, which has high utility value, is disadvantageous from an efficiency standpoint.

As mentioned above, with the method of recovering and utilizing heat from each waste heat source independently, not only is the equipment cost relatively high, but it is also difficult to ensure profitability as an energy-saving facility with steam recovery and electricity recovery, which have higher added value. It becomes difficult.

The present invention was developed in view of the above circumstances, and its purpose is to recover the sensible heat of coke oven combustion waste gas and coke oven gas, which were conventionally disposed of, by supplying them to coke dry extinguishing equipment. , (1) Quantitative expansion of energy conservation in coke oven factories (Figure n5) (2) Improved profitability of heat recovery equipment (Figure n) (3) A simple structure for converting coke oven combustion waste gas to coke oven gas and An object of the present invention is to provide a method and apparatus for recovering waste heat from a coke oven, which can be used as a common heat medium for recovering the sensible heat of coke and can also recover its own heat.

The above object can be achieved in the following manner according to the present invention. That is, the low-temperature coke oven combustion gas is preheated by the sensible heat of the coke oven's high-temperature carbonization gas of 3-, and the preheated coke oven combustion waste gas is introduced into the circulation system of the coke dry extinguishing equipment and used as circulating gas. At the same time, the introduction position is placed on the upstream side of the waste heat boiler, and the red-hot coke is cooled in the cooling tower and combined with the circulating heated gas to be combusted. This method uses a boiler to recover the sensible heat of the boiler.

In addition, a heat exchanger is installed in the coke oven carbonization gas recovery duct and preheats the coke oven combustion waste gas by bringing the high temperature carbonization gas discharged from the coke oven into indirect contact with the low temperature coke oven combustion waste gas. a communication duct that connects the heat exchanger and the circulation system on the upstream side of the coke dry extinguishing equipment and introduces preheated coke oven combustion waste gas into the circulation system; and a connection part of the communication duct. and a catalytic combustor that catalytically burns a mixed gas of coke oven combustion waste gas introduced from a connecting duct provided in the circulation system between the above-mentioned boiler and the heated gas discharged from the cooling tower outlet. It also includes equipment that has been installed.

4- Hereinafter, a preferred embodiment of the coke oven waste heat recovery method and apparatus according to the present invention will be described with reference to the accompanying drawings.

First, prior to examples, the background and principles of the present invention will be explained in order to facilitate understanding of the present invention.

The main focus of the present invention is to use coke oven combustion waste gas as a common heat medium for recovering the sensible heat of coke oven gas and red-hot coke, and to also recover the heat of the coke oven itself.

Sensible heat recovery from coke oven gas involves indirect heat recovery by guiding the coke oven combustion waste gas to a diaphragm heat exchanger installed in the coke oven gas recovery duct. Since it does not come into direct contact with coke oven gas, it does not adversely affect the quality of coke oven gas. However, in order to recover sensible heat from red-hot coke, coke oven combustion waste gas is brought into direct countercurrent contact with lump coke filled in a cooling tower, so gas components that react with coke become a problem.

Here, an example of the composition of coke oven combustion waste gas as cooling gas (circulating gas) will be shown in comparison with circulating gas used in conventional coke dry extinguishing equipment.

*Total calorific value 4.780 kcat/Nm (rich gas) **Total calorific value 1.200 kcat/Nm5 (poor gas) According to the table, coke oven combustion waste gas contains 02 and 02, which enter from excess combustion air. CO2 and H2 as combustion components
Contains O. Of these, 02 and H2O are components that are not present in the circulating gas components of conventional coke dry extinguishing equipment, and C02
It can also be seen that the amount increases when poor gas is used as fuel. Although there are differences depending on the gas concentration and reaction temperature, H2O and CO2 each undergo a water gas reaction (C + H20→
H2+Co), water gas side reaction (C-1-CO2→2
coke is wasted according to CO), but the generated CO and H
2 has room for effective use. On the other hand, 02 is not preferable because it oxidizes and burns coke and causes a decrease in yield.

Therefore, in the present invention, the above-mentioned solution reaction (
By oxidizing and burning the combustible components CO and H2 generated in water gas reactions and water gas side reactions), the 02 concentration in the red-hot coke cooling gas is reduced to an almost negligible level.

The above-mentioned oxidative combustion is carried out by passing a mixed gas of circulating gas from the cooling tower and coke oven combustion waste gas from the coke oven through a noble metal catalyst bed provided in a circulating gas duct before the waste heat boiler, and bringing the mixture to a low-temperature acid ratio. This oxidation combustion heat increases the temperature of the waste heat boiler inlet gas to thermally compensate for coke loss due to solution loss.

Incidentally, in order to increase the amount of circulating gas due to the introduction of coke oven combustion waste gas, a part of the waste gas from the waste heat boiler is branched from the circulating gas duct before the cooling tower and is dissipated into the atmosphere.

Next, an embodiment of the present invention will be described based on the drawings.

As shown in the figure, reference numeral 1 denotes a chamber-type coke oven, and the coke oven combustion waste gas exiting each flue in a regenerator 2 enters a flue 3. In the existing equipment, the exhaust gas was sucked in by the exhaust gas fan 4 and released into the atmosphere through the chimney 5. However, part or all of the coke oven combustion waste gas is transferred to the duct 6 which is branched into the flue 3. 7 and 8 to separate the streams and guide them to the heat exchanger 10 provided in the riser pipe 9 of the coke oven 1. In this heat exchanger 10, coke oven gas passes through the inner tube, and coke oven combustion waste gas passes through the outer tube, so that even if carbon adheres to the coke oven gas passage, it can be easily removed. It is best to use a double-tube structure that is as simple as possible. High-temperature coke oven gas (600-800°C for 10 heat exchangers) flows from bottom to top in the inner tube, and relatively low-temperature coke oven combustion waste gas (13°C for 10 heat exchangers) flows into the outer tube.
0 to 8-230°C) flows from top to bottom, forming counterflows through the partition wall 11, so that the temperature of the coke oven combustion waste gas at the exit of the heat exchanger 10 is as high as possible. This heat exchanger 1
When installing 0 in an existing coke oven 1, it is preferable to install it in the riser pipe section, which requires almost no modification of equipment or changes in operation, as shown in the example shown, but it can also be installed in the dry boiler 712 or suction main. can. In this case, it is necessary to change the mounting position of the gas-liquid separation device including the ammonium water spraying device 13 to the position after the heat exchanger 10. In the illustrated example, the equipment after the heat exchanger 10, such as the furnace pressure regulating valve 14, the ammonium water spraying device 13, and the dry main 12, may remain as they are. In addition, when designing the heat exchanger 10, in order to prevent the tar in the gas from condensing before the coke oven gas that has passed through the inner tube reaches the ammonium water spraying device 13, the outlet temperature of the heat exchanger 10 is set at 400°C. Care should be taken to ensure that the temperature is ~450°C or higher.

The outer tube of the heat exchanger 10 is connected via a communication duct 16 to a circulating gas duct 15 of a coke dry extinguishing system, which is a downstream equipment of the coke oven 1.

The coke dry extinguishing equipment is the same as the existing equipment, and 17
18 is a cooling tower, 18 is a dust remover, 19 is a boiler, 20 is a cyclone, 21 is a circulation fan, and the circulating gas is sent to the cooling tower 1.
1 to cool the red-hot coke in the tower, and the circulating gas whose temperature has been raised by the cooling and cooling is introduced into the grate 19 to recover heat. Then, in balance with the amount of gas introduced into the circulating gas duct 15 from the communication duct 16, a part of the cooling gas is released into the atmosphere from the exhaust gas duct 23 branched to the gas duct 15 through the chimney 24, and at the same time, the cooling tower 17 is While adjusting the valves 25 and 26 to control the furnace top pressure to atmospheric pressure, the circulation fan 2
1. The exhaust gas fan 21 is operated. The communication duct 16 is connected between the boiler 19 and the dust remover 18 of the coke dry fire extinguishing equipment configured as described above. A mixed gas of coke oven combustion waste gas introduced from the communication duct 16 and heated gas discharged from the outlet of the cooling tower 17 is introduced into the circulating gas duct 15 between the connecting portion of the communication duct 16 and the boiler 19. A noble metal catalytic combustor 28 is provided for catalytically burning the precious metal. This catalytic combustor 28 is constructed by introducing a premixed mixture of fuel and air, and due to the oxidation promoting effect of the catalyst that has been preheated to a predetermined temperature or higher, unlike normal flame combustion, the flame temperature on the surface of the catalyst is low. It has the ability to cause complete combustion. Although the precious metal catalyst used in the catalytic combustor 28 is expensive, it can be recovered and reused, so it is not a big burden in terms of cost.

The present invention will be explained in detail using the above configuration.

The coke oven combustion waste gas A passes through the duct 6 and enters the outer tube of the heat exchanger 10, where it is heated by the sensible heat of the high temperature coke oven gas B flowing through the inner tube. The coke oven combustion waste gas A heated by the sensible heat of the coke oven gas is introduced into the circulation system 22 of the coke dry extinguishing equipment through the communication duct 16, and the circulating gas C cools the red-hot coke in the cooling tower IT. becomes.

In addition, since the coke oven combustion waste gas is introduced into the circulating gas duct 15 before the waste heat boiler 19, the sensible heat of the coke oven combustion waste gas itself and the sensible heat of the coke oven gas recovered The heat is recovered in the tank 19. Therefore, the coke oven combustion waste gas acts as a common heat transfer medium that recovers the sensible heat of both the red-hot coke and the coke oven gas. The increased amount of the circulating coke 7' due to the intrusion of the coke furnace combustion waste 7 is recovered by the boiler 19, and then transferred to the cooling tower 11.
The exhaust gas enters an exhaust gas duct 23 branched from the circulating gas duct 15 in front of the exhaust gas, passes through a chimney 24, and is dissipated into the atmosphere.

As already mentioned, there is a slight difference in the burnup gas composition depending on whether the coke oven fuel gas is rich gas (coke oven gas) or poor gas (coke oven gas + blast furnace gas). It is as follows.

While there is not much difference in O2 in both gases, H2O in rich gas and CO2 in poor gas are large in quantity, and when they come into contact with coke, they cause a solution loss reaction and become the main components. Therefore, no matter which fuel gas is used, a solution loss reaction is induced in the cooling tower 17, and the heated circulating gas discharged from the outlet of the cooling tower 17 contains an appropriate amount of combustible content 12- (CO and ) will be included. The circulating gas containing combustibles and the burnup gas from the coke oven become a mixed gas before the boiler 90 and are sent to the catalytic combustor 28. Therefore, in the mixed gas, the combustible components (CO and H2) in the gas react with 02 at a temperature far lower than the normal combustion temperature, resulting in complete combustion. As a result, the concentration of 02 in the cooling gas flowing into the cooling tower 11 through the waste heat boiler 9 can be reduced to almost zero. Note that the combustion heat generated during combustion is effectively recovered in the boiler 9 together with the sensible heat of the coke.

The amount of combustible material required to consume 02 is estimated based on the gas composition shown in the table, and it is found that when the burnup gas is rich in gas, when the cooling gas passes through the red-hot coke cooling tower 11, the aqueous CO and H are generated by the gas reaction, and the reaction rate of the water gas reaction is 0.22 to 8% of the gas-rich combustion waste gas.
It was found that 5 to 30q6 is sufficient. In addition, when a poor gas burnup gas is used, CO is generated by the water gas side reaction occurring in the cooling tower 17, and the reaction rate of the water gas side reaction is 0.22 to 6% of the poor gas combustion waste gas. On the other hand, it was found that 5 to 20% is sufficient. A reaction rate of this level is normally obtained, but if the above-mentioned reaction rate cannot actually be obtained in the cooling tower 11, combustible components such as rich gas or poor gas are removed before the catalytic combustor 28. Fuel gas nozzle 29
It is sufficient to provide a nozzle 29 and replenish the circulating gas into the distillate 15.

By the way, the aforementioned water gas reaction and water gas side reaction are endothermic reactions, and although the coke cooling performance in the cooling tower 17 is improved, the temperature of the log gas exiting the cooling tower 11 may be slightly lowered. However, it has been found through trial calculations that due to the heat of combustion caused by the above-mentioned mixed gas passing through the catalytic combustor 28, high-temperature gas of 800° C. or higher can be obtained using the waste heat boiler 19.

This is enough to thermally compensate for the loss of coke caused by the solution loss reaction.

In this way, the coke oven combustion waste gas preheated by the sensible heat of the carbonized gas of the coke oven is heat recovered by sharing the boiler 19 of the coke dry extinguishing equipment. Sensible heat can be recovered by combining coke oven combustion waste gas with coke oven gas and red-hot coke, dramatically increasing the energy saving effect of coke oven factories. In addition, although coke dry extinguishing equipment has had problems with the profitability of heat recovery, the present invention makes it possible to increase the amount of heat recovered by sharing a large boiler, making the equipment cost relatively low. Furthermore, by employing the catalytic combustor 28, the coke oven combustion waste gas unavoidably contains 02
Since all of the combustible content is consumed during complete combustion, the amount can be reduced to a negligible level. therefore,
The coke oven combustion waste gas can be used as a total circulating gas, and it does not cause oxidative combustion of coke or reduce yield, and can exhibit the same cooling effect as conventional circulating gas.

In addition, by using the catalytic combustor 28, the temperature of the boiler 19 can be increased without supplementing other heat sources from outside the system, so high-temperature, high-pressure steam can be easily generated.
Energy recovery efficiency is improved as much as possible. As a result, it can contribute to improving the profitability of coke dry extinguishing equipment.

In addition, since the boiler 19 is installed independently from the coke oven equipment, even if the boiler 19 is shut down due to periodic inspections, etc.
It will not interfere with the operation of the coke oven.

In short, the present invention exhibits the following excellent effects.

1) With this method, burnup gas from coke ovens, which was previously discarded, can be used as a common heat medium to recover the sensible heat of coke oven gas and red-hot coke, and it can also recover its own heat. As a result, it is possible to quantitatively expand energy savings in coke oven factories.

2) Since the recovery of the sensible heat mentioned above is carried out in a common boiler, this 7I? The profitability of coke dry extinguishing equipment (heat recovery equipment) that uses coke oven combustion as a component has been greatly improved. It is possible to reduce n02 that is unavoidably contained, and it is possible to effectively eliminate obstacles when using coke oven combustion waste gas as a circulating gas.

4) Furthermore, with this device, waste heat from a coke oven can be effectively recovered with a simple structure of a heat exchanger, a connecting duct, and a catalytic combustor. In particular, since a catalytic combustor is employed, the O2 concentration can be reduced as much as possible through complete combustion, and the coke loss caused by the solution loss reaction can be sufficiently compensated for thermally.

[Brief explanation of the drawing]

The figure is a system diagram showing a preferred embodiment of the coke oven waste heat recovery device according to the present invention. In the figure, 1 is a coke oven, 10 is a heat exchanger, 15 is a circulating gas duct which is an element of the circulation system, 16 is a communication duct,
17 is a cooling tower, 19 is a steel plate, 22 is a circulation system, 28 is a catalytic combustor, A is coke oven combustion waste gas, B is coke oven carbonization gas (coke oven gas), and C is circulation gas. .

Claims (2)

[Claims] (1) Preheat the low-temperature coke oven combustion waste gas with the sensible heat of the high-temperature carbonized gas of the coke oven, and guide this preheated coke oven combustion waste gas to the circulation system of the coke dry extinguishing equipment.
The coke is characterized in that the red-hot coke is then cooled, combined with circulating heated gas, and combusted, and the sensible heat of the heated gas containing this combustion gas is recovered in a boiler. Furnace waste heat recovery method. (2) A heat exchanger that preheats the coke oven combustion waste gas 1 by bringing the high temperature carbonized gas discharged from the coke oven into indirect contact with the low temperature coke oven combustion waste gas, and the heat exchanger and the coke dry extinguishing method. A communication duct that connects the circulation system on the upstream side of the boiler of the equipment and introduces preheated coke oven combustion waste gas into the circulation system, and is installed in the circulation system between the connection part of the communication duct and the boiler. Introduced from the connecting duct
A coke oven waste heat recovery device comprising a catalytic combustor that catalytically burns a mixed gas of coke oven combustion waste gas and heated gas discharged from a cooling tower outlet.