JPH0343276Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an oxygen delignification apparatus suitable for chemical pulp processing, particularly for medium consistency pulp processing.

[Conventional technology]

Papermaking and dissolving pulp are manufactured using wood as a raw material, while chemical pulp is manufactured by chipping wood, cooking it, and then performing various treatments such as washing, selection, and bleaching. At this time, in order to bleach the pulp, delignification equipment is mainly carried out on the cooked pulp by a chemical reaction, and in particular, the use of oxygen in the delignification equipment has recently attracted attention.

Figure 2 is a system diagram of a conventional delignification process using oxygen, in which 1 is a digester in which raw material wood chips are digested with caustic soda (NaOH) and steam to produce cooked pulp; This is an oxygen delignification device connected to 1. The oxygen delignification device 2 includes a mixer 4 for mixing the cooked pulp with oxygen from an oxygen tank 3, and a reaction tube for delignifying the cooked pulp introduced through the mixer 4 under a pressure of 2 to 5 kg/ ^cm2 . 5, and a blow tank 6 that is connected to the reaction tube 5 and separates the delignified pulp blown from the reaction tube 5 into gas and liquid. The gas phase is sent to step 7 and treated, and the gaseous phase portion is discharged to boiler 9 via pipe 8, where it is combusted and then released into the atmosphere. Note that the heat from the boiler 9 is used for private power generation and the like.

Oxygen delignification treatment is carried out as described above, but depending on the operating conditions, the gas phase of the blow tank 6 may have a composition of approximately 60% oxygen and 10 to 18% carbon monoxide (CO), producing an explosive mixed gas. To operate safely, it is necessary to dilute the gas phase to make it non-explosive.

[Problem that the invention attempts to solve]

However, even if the CO concentration is diluted to less than 1/4 of the lower explosive limit (12.5%) using a large amount of air, if the oxygen concentration exceeds 25% in the diluted state, an alarm must be installed under the High Pressure Gas Control Law. becomes compulsory and complicated. Therefore, it is necessary to further dilute the oxygen with air, but air originally contains about 20% oxygen, so using air to lower the oxygen concentration is not effective and requires a large amount of air, making it difficult to use equipment. It is economically inconvenient. It is also possible to dilute with an inert gas such as nitrogen, but this is not economical as it requires purchasing a large amount of nitrogen gas.

[Means for solving problems]

This invention was made in view of the above-mentioned disadvantages.
We focused on the fact that the waste gas emitted into the atmosphere during oxygen production in pressure fluctuation oxygen production equipment (hereinafter referred to as O ₂ PSA) used in the field of air separation technology contains a large amount of nitrogen components. and the O ₂
The above-mentioned disadvantages were solved by applying PSA to oxygen delignification treatment. That is, the oxygen delignification apparatus according to the present invention is characterized in that it uses O ₂ PSA as an oxygen supply means and is configured to introduce waste gas discharged from the O ₂ PSA into the gas phase of the reaction column. .

〔Example〕

FIG. 1 is a system diagram showing an embodiment of the present invention, in which the same components as in FIG. 2 are given the same reference numerals.

In the figure, 10 is a two-cylinder type O ₂ PSA, which includes an adsorption cylinder 11a filled with an adsorbent such as zeolite,
11b are used alternately, and the pressure difference between adsorption and regeneration is used to separate oxygen from the air and supply it to Misaki 4. That is, the blower 1 for introducing air
2 is connected to the adsorption column 1 via pipes 13, 14a, 14b.
1a, 11b, and the adsorption cylinders 11a,
11b is connected to the mixer 4 via valves 15a, 15b and a pipe 16, and is further connected to the vacuum pump 1 for desorption via valves 18a, 18b to the adsorption cylinders 11a, 11b.
9 is connected, and the vacuum pump 19 is connected to the blow tank 6 via a pipe 20, a buffer tank 21, a dehumidifier 22, and a blower 23.

Therefore, the air sucked by the blower 12 is compressed to, for example, 5 kg/cm ² and the air is
The oxygen is introduced into the adsorption column 11a, where nitrogen and impurities such as moisture and carbon dioxide are adsorbed (adsorption step), and oxygen is supplied to the mixer 4 via the valve 15a and the pipe 16. At this time, the other adsorption cylinder 11b
is in the regeneration process, and valve 15b and pressure equalization valve 17
is closed, valve 18b is opened and vacuum pump 19
The adsorption column 11b is evacuated and impurities such as nitrogen and moisture adsorbed in the previous cycle and a small amount of oxygen are desorbed and stored in the buffer tank 21 via the pipe 20. After the adsorption cylinder 11b is regenerated by the evacuation, the pressure equalization valve 17 is opened for a short time and the adsorption cylinder 1 is regenerated.
A part of the oxygen in 1a is introduced into adsorption cylinder 11b to equalize the pressure in both cylinders 11a and 11b, and then valve 14
a is closed and the valve 14b is opened, the adsorption cylinder 11b enters the adsorption process, and the adsorption cylinder 11a enters the regeneration process, and is thus continuously used.

Note that the regeneration process described above is only an example,
In addition to the above, there are various regeneration methods, such as opening the pressure equalization valve 17 and introducing a part of the oxygen from the adsorption cylinder in the adsorption process into the adsorption cylinder in the regeneration process, or even using vacuum exhaust in combination with this. be.

As mentioned above, oxygen from the O ₂ PSA 10 is introduced into the reaction column 5 through the mixer 4 and used for delignification treatment, while the waste gas stored in the buffer tank 21 is passed through the dehumidifier provided as necessary. After being dehumidified in the container 22, it is pressurized by the blower 23 and introduced into the gas phase portion of the blow tank 6. In this way, the waste gas from O ₂ PSA10 is about 90% nitrogen,
Since it contains about 10% oxygen and a large nitrogen content, the gas phase of the blow tank 6 can be easily made into a non-explosive mixed gas, making subsequent processing safer.

Note that since the O ₂ PSA is operated by switching adsorption cylinders, the waste gas from the O ₂ PSA is also intermittent, but this can be smoothed by providing a buffer tank 21 if necessary.

[Effect of idea]

As mentioned above, the oxygen delignification apparatus of the present invention uses O 2 PSA, which is used in the field of air separation technology, as an oxygen supply means, and in this field, nitrogen-rich O ₂ PSA, which is simply released into the atmosphere, is used as an _oxygen supply means. The waste gas from the blow tank is introduced into the gas phase of the blow tank, and this gas phase, which can become an explosive mixture depending on the operating conditions, can be made non-explosive, allowing for safe operation and great implementation effects. . In addition, this device uses O ₂ PSA
Since it uses waste gas from the plant, it has high economic value and is practical.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an embodiment of the present invention;
The figure is a system diagram showing a conventional example. 1... Digester, 2... Oxygen delignification equipment, 4
...Mixer, 5...Reaction column, 6...Blow tank, 10...O ₂ PSA, 11a, 11b...Adsorption column, 12, 23...Blower, 19...Vacuum pump, 21...Buffer tank.

Claims (1)

[Scope of utility model registration request] A pressure-fluctuation type oxygen production device, a mixer for mixing oxygen gas from the device into cooked pulp, a reaction column for delignifying the cooked pulp introduced through the mixer, and a delignification device blown from the reaction tube. It consists of a blow tank that introduces lignin-treated pulp and separates gas and liquid, and divides the liquid phase into the next pulp treatment process and the gas phase into the exhaust gas treatment process. An oxygen delignification apparatus characterized in that the exhaust gas from the apparatus is introduced into the gas phase portion of the blow tank.