JPS5944346B2 - Method for recovering heat from coke oven gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering heat from coke oven gas, and particularly to a method for efficiently recovering gas sensible heat generated during coal carbonization in an industrial coke oven.

As is well known, when coke is manufactured by carbonizing coal in a coke oven, so-called coke oven gas is generated.

This gas is collected in a header pipe through a riser pipe on each furnace, sucked in by a blower, purified by removing impurities, and then used as fuel gas in factories.

This coke oven gas is 130X103K cal
/coal- (temperature of 600 to 800°C), and in recent years, attempts have been proposed to recover the sensible heat possessed by coke oven gas and use it for energy conservation.

The applicant also connected a heat exchanger to a heat exchanger tube installed on the inner wall of the riser tube, using an organic heat medium (such as alkyldiphenyl), which has a high boiling point, is highly fluid at low temperatures, and is thermally stable and can be used in the liquid phase at normal pressure. We have previously filed an application for a heat recovery method that involves circulating coke oven gas (which has excellent properties) and recovering the sensible heat of coke oven gas through the heat transfer medium. 53-114
No. 399).

The heat recovery method disclosed in Japanese Patent Application No. 53-114399 has the following advantages.

(1) Since heat is transferred in a liquid state, it has high thermal conductivity and can efficiently recover heat.

(2) Organic heat carriers can be regenerated, and the same heat carrier can be used continuously for a long period of time as long as it does not leak.

(3) By using it at normal pressure and in a liquid phase state, the piping is small and long-distance transportation is possible using a liquid pump, which requires less space and reduces equipment costs than when recovering with air.

The method of recovering heat from coke oven gas at the coke oven riser using the above-mentioned organic heating medium can be said to be an extremely effective method, but when applied to an actual coke oven, New problems arise that must be resolved.

That is, it is necessary to consider that the amount of heat held by coke oven gas is not constant during the carbonization cycle but fluctuates.

Figure 1 shows an example of this variation. A maximum value (indicated by point A) occurs during carbonization, and furthermore, at the end of carbonization, the amount of heat transfer increases rapidly due to combustion and dissipation due to carbon incineration in the riser tube. However, it is nearly twice the average value.

On the other hand, considering the efficiency of the utilization of the recovered heat, it is desirable to maintain the organic heat medium at a high temperature level as close to the boiling point as possible.

This is also related to the expansion of coke oven gas usage technology and the reduction of the heat transfer area of heat exchangers.

Therefore, it is necessary to operate with the temperature of the heat medium at the exit side of the riser kept constant close to the boiling point.

However, as mentioned above, the sensible heat of the coke oven gas fluctuates during the carbonization cycle, so if the operation is close to the boiling point of the heating medium, the boiling point will be exceeded at points A and B in Figure 1. The organic heat medium vaporized in the pipes will cause a very alarming situation, such as a simmering phenomenon and, in some cases, pipe destruction.

Therefore, in order to prevent the above-mentioned situation from occurring, a method can be considered in which a control valve is provided on the heat medium inlet side of the riser tube and the flow rate is controlled based on the temperature of the outlet side.

However, with this method, a control valve must be installed for each of the many riser pipes, which is disadvantageous in terms of equipment, and because there are many control valves, the pressure drop is large, and the circulation pump capacity is There are problems such as the need to increase the size, and it is not practical.

Furthermore, it is conceivable to install a cooler or a steam removal tank on the heat medium outlet side of the riser pipe, but this would result in an increase in the number of equipment, that is, an increase in the maintenance load, an increase in the capacity of the heat medium circulation pump, and the same problems as above.

In view of these circumstances, the inventors of the present invention have determined that when recovering the sensible heat of coke oven gas through an organic heat medium at the riser pipe position, there is no risk of vaporization of the heat medium, and the temperature is as low as possible at the boiling point of the heat medium. As a result of various research and experiments on a method for recovering heat from coke oven gas that can be operated at similar temperatures and has advantages in terms of equipment and work, as well as efficient heat recovery and is highly practical, we have developed a coke oven. It has been discovered that the above problems can be solved by grouping a large number of risers in consideration of operational characteristics.

That is, an object of the present invention is to be able to most efficiently recover gas sensible heat generated during coal carbonization in an industrial coke oven, and to perform rational heat recovery in accordance with the actual conditions of coke oven operation. An object of the present invention is to provide a method for recovering heat from coke oven gas.

However, the feature is that each riser pipe is grouped for each furnace kiln that shows a similar heat fluctuation pattern based on the order of coke oven operation (coal loading work), and each group is independently The aim is to control the outlet temperature so that it remains stable at a temperature close to the boiling point.

In general, the order of coke oven operation is set at intervals of multiple windows (for example, in order of 5 ovens or 2 ovens) from the viewpoint of local reduction of coke oven furnace temperature and balance of generated coke gas.

For example, in the case of 100 kilns/furnace group, the order of 5 kilns is #1°, #6, #11,...#91. #96. Next #3 and #8.

...#98, and further #5 to #100. The order is #2 to #91° and #4 to #99.

Therefore, the heat transfer amount variation pattern shown in FIG.
1... shows similar heat transfer patterns.

In the present invention, each riser pipe of a plurality of furnaces showing similar heat transfer patterns is grouped, and specifically, the organic heat medium outlet side of these riser pipes is connected by a common header pipe, and the riser pipes are grouped together. This is to control the exit side heat medium temperature.

The number of riser pipes to be grouped may be arbitrary, and may be determined depending on the total number of furnaces.

As the actual heating medium temperature control means on the exit side of the riser, so-called cascade control, which controls the heating medium flow rate with respect to the temperature setting, is suitable.

The present invention will be described below based on embodiments shown in the drawings.

Figure 2 shows the basic flow of a coke oven gas heat recovery facility to which the present invention is applied.
1 is a coke oven, 2 is a coke oven gas distribution riser pipe provided at the upper part of the coke oven 1, 3 is a heat exchanger, and 4 is a heat medium circulation pump.

It is preferable to provide a flow path 5 in the wall portion of the riser tube 2 to allow the heat medium to flow in a spiral shape, so as to expand the heat transfer area and efficiently absorb the amount of heat from the coke oven gas.

The heat medium is sent into the flow path 5 from the supply port at the bottom of the riser pipe 2 by the pump 4, heated by the heat of the coke oven gas, discharged from the discharge port at the top, and sent to the heat exchanger 3.

The heat medium whose temperature has been lowered by heat exchange in the heat exchanger 3 is sent again to the riser pipe by the pump 4 and is used for circulation.

In this heat recovery method using heat medium circulation, it is desirable to keep the temperature at the exit side of the riser of the heat medium as close to the boiling point of the heat medium as possible from the viewpoint of efficiency. There is a risk that the heat transfer medium will vaporize as the amount of heat transfer fluctuates.

The present invention adopts the control flow shown in FIG. 3 in order to prevent such risks and achieve efficient heat recovery.

That is, in FIG. 3, #1 to #20 indicate the coke oven riser pipes 2, and 20 examples are listed for convenience.

As described above, the riser pipe 2 is provided with a flow path through which an organic heat medium flows.

3 is a heat exchanger, and 4 is a heat medium circulation pump.

Further, 6 is a main pipe on the supply side of the pump 4, and the main pipe 6 is 5
It branches into main branch pipes 7a to 7e, and further branches to each branch pipe 7a to 7e.
1e is divided into five branch pipes each, and these branch pipes are connected to the inlet side of the rising pipe 20.

For example, the branch pipe 7a is divided into branch pipes 8a to 8d, and the same applies to the other branch pipes.

In the present invention, when connecting the branch pipes 7a to 7e and the 20 riser pipes 2, the riser pipes 2 are grouped according to similar heat transfer variation patterns, and the grouped riser pipes are combined into one riser pipe. Connect to branch pipe.

In the illustrated example, one # of rising pipes = 1, 6, 11°16 is A.
Group, #2, 7, 12, 17 as B group, #3,
8, 13, 18 are group C, #4, 9, 14, 19 are group D, #5, 10゜15.20 are group E, total of 5 groups, group A is a branch pipe? a
, B group is branch pipe 7b, C group is branch pipe 7c,
The D group is connected to the branch pipe 7d, and the E group is connected to the branch pipe 7e via branch pipes.

The outlet sides of the riser pipes 2 are connected to the main supply pipes 9 to the heat exchanger 3 via branch pipes.

Further, control valves 10a to 10e are installed in each of the branch pipes 7a to 7e, and the valves control the flow rate of the heat medium according to commands from flow rate controllers 11a to 11e, respectively.

On the other hand, a temperature detection end 12 for detecting the temperature of the heat medium to be discharged is provided immediately after the exit side of each riser pipe 2, and the temperature detected by these ends is determined based on the above-mentioned grouped block unit. temperature controllers 13A to 13
It is input to E.

In the temperature controllers 13A to 13F, the temperature is as close as possible to the boiling point of the heat medium (for example, when alkyldiphenyl is used as the heat medium, the boiling point is 286°C, so
The set temperature may be approximately 270° C.), and when at least one exit temperature in the group exceeds the set temperature, a corresponding amount of heat medium flow signal is sent to the flow rate controller 11. 3. Conversely, when a temperature lower than the set temperature is detected, the valve can be operated in the same process to reduce the flow rate of the heat medium.

In this way, the temperature of the heat medium at the exit side of the riser pipe 2 is stabilized around the set temperature, and the heat medium is not vaporized (circulated), and the heat amount of the coke oven gas is transferred to the heat exchanger 3. The equipment is then collected and sent from there to any facility for use.

In the figure, 14 is a pressure regulator installed in the main pipe 6;
Reference numeral 5 denotes a control valve provided in a conduit connecting the inlet and outlet sides of the circulation pump 40 in a bypass manner, and its opening degree is controlled by a command from the pressure regulator 14.

The pump pressure is adjusted to the optimum pressure by these regulator 14 and valve 15.

Further, 16 is a storage tank for replenishing the heat medium provided in the inlet pipe of the circulation pump 40, and 11 is a replenishment pump thereof.

Furthermore, although not shown in the illustrated circulation system, it is preferable to arrange equipment that can deal with abnormal leakage of the heat medium.

As a result of using the heat recovered in this way as a preheating source for blast furnace gas for coke oven combustion, the blast furnace gas was heated from 25℃ to 6℃.
It can be stably preheated to 0℃, and the conventional preheating steam 1.5. It became possible to reduce the total amount of t/Hr.

In the heat recovery method of the present invention described above, when recovering the heat amount of coke oven gas by supplying an organic heat medium to the riser tube, a large number of riser tubes are divided into multiple riser tubes, each having a similar heat transfer pattern. Since the temperature of the heat medium at the outlet side of the riser pipe is controlled for each group, the control mechanism is not complicated and the number of control devices can be reduced, which is extremely advantageous in terms of operation and equipment.

Moreover, since the heat medium temperature can be managed by grouping, it is easy to perform heat recovery operations for coke oven gas, and stable operation is possible at temperatures close to the boiling point of the heat medium, resulting in extremely high heat recovery efficiency (advantages of There is also.

Therefore, the present invention is a heat recovery method most suitable for application to actual industrial coke ovens, and its industrial value is extremely large.

[Brief explanation of drawings]

Figure 1 is a chart showing the heat transfer pattern of coke oven gas during coal carbonization, Figure 2 is a schematic diagram showing the basic configuration of the coke oven gas heat recovery system, and Figure 3 is the heat recovery method of the present invention. FIG. 3 is a schematic diagram illustrating an example of the overall control flow of the method. 1...Coke oven, 2...Rising tube, Meter...Heat exchanger, 4...Heat medium circulation pump, 5...Heat Medium flow path, 6... Heat medium supply main pipe, 7a to 7e... Branch pipe, 8...
・Branch pipe, 9... Pipe line, 10a to 10e...
...Control valve, 11a-11e...
Flow rate controller, 12...Temperature detection end, 13A~1
3E... Temperature controller, 14... Pressure regulator, 15... Control valve, 16...
...Storage tank, 17...Replenishment pump.

Claims (1)

[Scope of Claims] 1. A heat exchanger is connected to a heat medium flow pipe disposed at a coke oven riser pipe to circulate an organic heat medium, and sensible heat recovery of coke oven gas is achieved through the organic heat medium. In doing so, each riser pipe is grouped for each furnace kiln that shows a similar heat fluctuation pattern based on the coke oven operating order, and each of these grouped riser pipes is independently determined so that the temperature at the outlet side of the heat medium reaches the boiling point. A method for recovering heat from coke oven gas, which is characterized by recovering heat by controlling it so that it is stabilized at a temperature close to that of the coke oven. 2. The heat recovery method according to claim 1, wherein the temperature at the outlet side of the heat medium in the grouped riser pipes is controlled by adjusting the flow rate of the heat medium.