JPS59145280A - Controlling hydrogen concentration in circulating gas in dry process coke quencher - Google Patents

Abstract

PURPOSE:To prevent outside corrosion of heat transfer tubes of a kiln effectively, by controlling a hydrogen concentration of a circulating gas in a dry process coke quencher to a level higher than a specified value. CONSTITUTION:Redhot coke 9 fed into a cooling chambe 4 from a quenching truck 1 is moved in the direction of the arrow by means of 9 blower 5 and is cooled in a boiler 7 and then with a circulating gas supplied to the bottom of the cooling chamber 4 through a blower 6. As volatile matters are separated from coke 9 in the cooling chamber 4 leading to an increase in the hydrogen content in the circulating gas, supply of diluting air from a blower 11 has so far been controlled to a hydrogen content of about 5-10% by means of a regulating valve 15 on the basis of a hydrogen concentration value measured with a gas analyzer. Control of the hydrogen concentration to above 10% makes it possible to prevent corrosion of heat transfer tubes of the boiler.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the hydrogen concentration in an inert gas circulated in coke dry extinguishing equipment in order to prevent corrosion.

In the conventional typical coke manufacturing method, coal is approximately 16
The coke is pushed out of the coke oven in ~22 hours, and when a freight car loaded with coke (called a fire truck) enters a building called a fire tower, it sprays water. At this time, a tremendous amount of white steam rose up, which caused problems for the steelworks as it was mistaken for smoke. There has been a strong desire to be able to recover and reuse the heat without emitting such unpleasant water vapor. Coke dry fire extinguishing equipment was developed in the Soviet Union in response to these needs.

The coke dry extinguishing equipment will be briefly explained in the first drawing. First, the fire extinguishing truck 1 loaded with hot coke is lifted onto the tower 3 by the hoist 2Iζ, and the coke at about 1000°C is dropped into the cooling chamber 4 below, where it is cooled with an inert gas such as nitrogen gas. be done. The inert gas is supplied from the blower 5 to the blowing device 6.
It is supplied to the cooling chamber 4 through. The space above Tower 3, where the fire engine is mounted, will be sealed and dust will be removed using a dust collector. After removing dust, the highly heated inert gas is sent to a boiler 71 to generate steam, and then passed through the dust collector 8 again, pressurized, and recycled again as cooling gas.

In the coke dry extinguishing equipment described above, the hydrogen partial pressure in the circulating cooling gas gradually increases due to the decomposition of volatile components in the charged coke. Therefore, in order to maintain the partial pressure of hydrogen in the circulating gas below a predetermined value, dilution air is blown into the boiler's artificial flue to burn the combustible components (Co, H,) in the circulating gas, resulting in a surplus of A portion of the recycled gas is cooled in the boiler and then extracted to the outside through the circulation fan outlet. Also.

Trace amounts of H, S and S are present in the circulating gas leaving the cooling tower.
Not only is O8 included, but it also contains water vapor produced by the combustion of hydrogen in the circulating gas by dilution air blown into the boiler flue. H, S, S
o, or water vapor, greatly affects the corrosion of the external surface of heat transfer tubes.

This is also clear from the following experimental results.

The experiment was conducted under the combination of steel samples, simulated atmosphere, and temperature conditions shown in Table 1, and the experimental results are shown in Figures 2 to 5.

Shown below.

Table 1 *) N, base, H, 0: 0.7% Figure 2 shows the relationship between the Cr content of steel and the amount of increase in corrosion obtained under the following experimental conditions.

(1) Three levels of atmospheric gas: 2N, gas space, ■, 10%, and H, 8100, 200, 300 ppm (2) Maintained at an ambient temperature of 600°C for 28 hours Cr content up to 5% corrodes regardless of the Cr content The amount increases, and with the increase of H, S at H, 10%, i.e., the partial pressure ratio "Hs8/pH,
The larger the value, the greater the amount of increase in corrosion.

Figure 3 shows atmospheric gas...N, gas space, H810.
%, H, 8200ppm and So, 0.40°120
This is a case of 3 levels of ppm (7) and 2 hours of holding at an ambient temperature of 600° C., and the tendency is almost the same as that shown in FIG.

Figure 4 shows atmospheric gas ---N, gas space, ■.

10%, Has 200 ppmg and SOB 120
ppm.

Showing the relationship with temperature in the case of 4-hour holding, there are two 1.
The amount of increase in corrosion increases with temperature up to 600°C. The reason why it becomes smaller at 700°C is presumed to be due to scale exfoliation.

Figure 5 shows atmospheric gas...H, gas space, H, 32
00ppm, So, 3 levels of 0, 40, 120ppm,
This figure shows the relationship between the amount of H2 and the amount of increase in corrosion when held at a temperature of 600° C. for 4 hours, and shows that the amount of increase in corrosion becomes smaller as the amount of H8 increases.

Table 2 shows the partial pressure ratio PH in coke dry extinguishing equipment,
This is an example of the oxidizing and reducing properties of /PH, O and the atmosphere shown in relation to the temperature range.

Table 2 From Table 2, the larger the PH and /Pa1o, the wider the reducing temperature range, and the reducing range is advantageous for preventing corrosion of boiler heat exchanger tubes. In any case, p,,,/
It can be seen that it changes to oxidation or reduction depending on changes in pH and o.

From the above experimental results, the external corrosion of the high-temperature boiler heat transfer tube in the waste heat boiler of coke dry fire extinguishing equipment has a pH of 18.
It has become clear that it is greatly influenced by /PH and the partial pressure ratio of PH, /PH, and O. In other words, keeping the hydrogen partial pressure in the circulating gas relatively high, at least 10% as shown in Figure 5, and lowering the water vapor partial pressure is an effective method for preventing corrosion of boiler heat exchanger tubes. was discovered. For this reason, as in conventional coke dry extinguishing equipment, air is blown into the boiler inlet flue to reduce the hydrogen concentration in the circulating gas and the hydrogen in the circulating gas is combusted. It was found that this increased the partial pressure of water vapor inside the boiler, causing corrosion on the outer surface of the boiler heat transfer tubes.

In addition to the above-mentioned increase in water vapor partial pressure, the corrosion of boiler heat transfer tubes is caused by H, S, So, etc. in the circulating gas, which have a very large effect.

SO2, etc. are greatly affected by the coke charged into the cooling tower, and it is difficult to arbitrarily control the concentrations of H, S, SO, etc. As is clear from the experimental results, if the hydrogen concentration in the circulating gas is maintained at 10% or more, Has, S
The influence of Oi, H, and O will be alleviated to a considerable extent. Conventional coke dry extinguishing equipment does not have the ability to precisely control the hydrogen partial pressure in the circulating gas, so the hydrogen concentration in the circulating gas changes depending on the amount of volatile components contained in the charged coke. Nevertheless, since no combustion amount control was performed in the boiler inlet flue, the PH, s/PH in the circulating gas entering the boiler
.

In addition to repeated oxidation and reduction due to fluctuations in the partial pressure ratio of PH, /PH, and O, oxidation and reduction due to fluctuations in the amount of residual unreacted oxygen caused by diluted air cause corrosion of boiler heat exchanger tubes. It is thought that As described above, the conventional method of controlling the hydrogen concentration in the circulating gas in coke dry extinguishing equipment has many drawbacks.

The present invention solves the drawbacks of the conventional method of controlling the hydrogen concentration in the circulating gas in coke dry extinguishing equipment, and injects a diluent gas such as air or blast furnace gas according to the measurement signal of the hydrogen concentration in the circulating gas, The present invention provides a method for controlling the dilution of the hydrogen concentration of the circulating gas so that the hydrogen concentration in the circulating gas falls within the above-mentioned range that has an anti-corrosion effect.

Conventional coke dry extinguishing equipment has not been able to prevent external corrosion of boiler heat exchanger tubes, but by adopting the present invention, external corrosion of boiler heat exchanger tubes can be easily prevented.

Next, the hydrogen concentration control method of the present invention will be briefly explained with reference to FIG.

The red hot coke 9 supplied from the fire engine 1 to the cooling room 4 is
The circulating gas cooled by the boiler 7 is again sent by the blower 5 to the blowing device 6 in the lower part of the cooling chamber 4, and the circulating gas cools the filled coke 9 and takes heat from the coke, increasing the temperature of the cooling chamber 4. It is supplied from the intermediate part to the boiler 7 via the flue 10, cooled by the boiler 7, and recirculated. Since volatile components in the coke 9 supplied to the cooling chamber 4 are separated within the cooling chamber 4, the hydrogen concentration in the circulating gas gradually increases. Conventionally, in order to control the hydrogen concentration within the range of 5 to 10%, a part of the circulating gas was combusted by blowing in air using a dilution blower 11 installed in the flue 10 connecting the cooling chamber 4 and the boiler 7. I was letting it happen. The amount of circulating gas increases as diluted air is introduced, but excess circulating gas is extracted from the outlet of the circulation blower 6 by a signal from the pressure controller 12 at the top of the cooling chamber 4, and is discharged outside the system or collected. It has been done. The circulating gas is analyzed by a gas analyzer 13 installed at the outlet of the boiler 7.
However, in conventional coke dry fire extinguishing equipment, this gas analysis value is only used to manage the circulating gas, and is not used to automatically control the dilution rush volume. Ta.

In addition, water vapor was generated because part of the circulating gas was combusted by the diluted air, and there was a strong tendency for the circulating gas to migrate to the oxidation side where corrosion occurred.

In the present invention, the cause of external corrosion of boiler heat transfer tubes is that fluctuations in PH%8/PH, PH, /PHtO in the circulating gas, that is, fluctuations in pH (hydrogen partial pressure), have a large effect on the tubes. As a result of finding that keeping the hydrogen concentration constant at 10% or more is a very effective method for preventing corrosion, the hydrogen concentration was adjusted according to the hydrogen concentration measured by the outlet gas analyzer 13 of the boiler 7. The flow rate of dilution air supplied from the dilution air blower 11 by the dilution air blower 11 is controlled by the control valve 15 to maintain the hydrogen concentration in the circulating gas at 10% or more.

In addition, instead of controlling the dilution air flow rate, blast furnace gas (Co2
0-30%, C0, 15-25%, H, 2-5%, N
, 50 to 55%) to the blowing device 6Ic provided at the lower part of the cooling chamber 4, blast furnace gas supply equipment consisting of a blower 16, a control valve 17, etc. may be provided. Automatic control of the blast furnace gas supply amount is performed by a boiler outlet hydrogen concentration controller 14. When recovering excess gas and supplying it to the blast furnace gas supply equipment, it is necessary to take out the blast furnace gas for dilution from the upstream portion 18 of the recovered gas inlet of the blast furnace gas supply equipment and balance it.

According to the present invention, since the hydrogen concentration in the circulating gas is always maintained at 10% or more, corrosion of the boiler heat exchanger tubes is prevented.
It can be used for a long time and its effects are extremely strong.

[Brief explanation of the drawing]

Figure 1 is a diagrammatic side view of a coke dry extinguishing system, and Figures 2, 3, 4, and 5 show the effects of H, S, So, temperature, and H3 on corrosion increase, respectively. The graph shown in FIG. 6 is a schematic partial side view of a coke dry extinguishing equipment for explaining the hydrogen concentration control method of the present invention. Explanation of symbols 1-...Fire engine, 2...Hoisting machine, 3...Tower, 4...
・Cooling room, 5...Blower, 6...Blowing device, 7...
・Boiler, 8... Dust collector, 9... Red-hot coke, 1
0... Flue, 11... Blower, 12... Pressure controller, 13... Gas analyzer, 14... Hydrogen concentration controller, 15... Control valve, 16... Blower , 17... Control valve, 18--Upstream patent applicant Kawasaki Steel Corporation Figure 1 Figure 2 C Content (Z) Figure 3 Cr Content (Z) Figure 4 Containment (°C ) Figure 5 H2 amount (%) Figure 6

Claims (1)

[Claims] The red-hot coke charged in the coke dry cooling tower is cooled by heat exchange with the circulating gas, and the circulating gas whose temperature has been raised by the heat exchange is supplied to the boiler and the heat is recovered as steam, and the temperature is lowered by the heat exchange. When circulating the circulating gas again to the dry cooling tower, the hydrogen concentration in the circulating gas is measured, and based on this measurement, blast furnace gas for dilution or air for dilution is introduced at the upstream side of the boiler in the circulating gas path. A water-concentration dilution control method for circulating gas in coke dry extinguishing equipment, characterized in that the hydrogen concentration in the circulating gas is maintained at 10% or more.