JPS6314646B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses a toluene solution of complex salts such as aluminum chloride and cuprous chloride, as typified by the Cosolve method.
This paper relates to a method for regenerating an adsorption device used in CO gas absorption separation equipment. Tenneco Chemicals' Cosolve method is a known method for recovering and purifying CO gas from a mixed gas containing CO gas emitted from coke oven gas, converter gas, cement kiln gas, water gas, etc. Most CO gas absorption separation equipment uses toluene solutions of complex salts, and the following requirements are required for these processes. (1) Since the CO absorption liquid contains complex salts such as aluminum chloride, the presence of moisture will chemically change the complex salts, making it an extremely moisture-averse process. (dew point temperature -60℃ or less). (2) Since toluene is vaporized and entrained in the product CO gas, toluene is gradually depleted, so it is necessary to recover the toluene. Also, since toluene in the product CO gas becomes an impurity in the product, It is desirable to remove as much as possible. (3) Since toluene is vaporized and entrained in the residual waste gas from which CO gas has been absorbed, it is necessary to recover this toluene as well. In order to meet the above process requirements, the present invention arranges each adsorption device at a functional position in the process so that the equipment can be operated using the most effective dehydration method and toluene recovery method for each requirement. CO gas absorption separation equipment that can be used as a system that can operate at a high level of dryness for dehydration and at close to the ultimate recovery rate (over 99.8%) for toluene recovery using a rational energy-saving method. This was developed with the aim of providing a method for regenerating adsorption equipment for CO gas absorption type separation equipment that uses toluene solutions of complex salts such as aluminum chloride and cupric chloride. The drying of the crude raw material gas, the recovery of toluene in the product gas, and the recovery of toluene in the waste gas are each performed using a two-column switching type adsorption device, and one tower is used for the drying process in the crude raw material gas drying process. While one column is in use, the waste gas discharged from the equipment is used to carry out the regeneration process of thermal desorption and cooling, and one column each is used in the recovery process of product CO gas and toluene in the waste gas. During the recovery step of adsorbing and recovering toluene, each of the other towers branches and utilizes a part of the crude raw material gas after drying to carry out the regeneration step of thermal desorption and cooling of toluene. It is something to do. That is, in the method of the present invention, three sets of two-column switching type adsorption devices are attached to the CO gas absorption type separation equipment, and the first
In one of the adsorption devices, the crude raw material gas is dehydrated and dried to a dew point temperature of -60°C or lower and sent to the equipment as raw material gas, while in the other tower, the CO gas is removed in the equipment. The dry waste gas is used to perform the regeneration process of thermal desorption and cooling, and the second adsorption device recovers the toluene in the product CO gas in the equipment in one tower and supplies it to the required plants as a complete product CO gas. etc., and in the third adsorption device, in one tower, toluene in the waste gas discharged from the equipment is recovered and the waste gas is sent to the adsorption tower in the regeneration process of the first adsorption device. On the other hand, a part of the dried raw material gas is sent to the other towers of the second and third adsorption devices to carry out the regeneration process of thermal desorption and cooling of toluene, and to convert the desorbed toluene into the dried crude raw material gas. By returning the raw material gas to the flow and feeding it into the equipment, high purity product CO gas can be obtained and toluene can be recovered at a high rate. Next, an example of an apparatus for carrying out the method of the present invention will be explained with reference to the drawings. The figure shows an example of a process flow sheet in which the method of the present invention is applied to a CO gas absorption type separation equipment using a toluene solution of a complex salt.
CO gas absorption type separation equipment, A1 is CO absorption tower, A
2 is CO vaporization tower, 1 is raw gas inlet, 2 is product CO
The gas outlet 3 is a waste gas outlet, and the raw material gas introduced into the CO absorption tower A1 from the raw material gas inlet 1 is transferred to the CO absorption tower A1.
CO is absorbed by a toluene solution of complex salt in 1,
In the CO absorption liquid, CO is vaporized in the CO vaporization tower A2,
The product gas is discharged from the outlet 2, but since this equipment A is well known, detailed explanation will be omitted. 10 is a first adsorption device for dehydrating the crude raw material gas to a dew point temperature of -60°C or less, and an adsorption tower 1
1 and 11a, and in the state shown in the figure, the crude raw material gas is introduced from below through the inlet 12 into the adsorption tower 11, and the adsorption tower 1
The adsorption tower 11 is dehydrated and dried to a dew point temperature of -60°C or less in the adsorption tower 11, and then passed through a pipe from the upper part of the adsorption tower 11 to the control valve 17.
The gas is sent to the raw material gas inlet 1 of equipment A through. On the other hand, the adsorption tower 11a is in the regeneration process, and the adsorption tower 11a is in the regeneration process.
The dry waste gas discharged from the CO absorption tower A1 from which the CO gas has been removed is used as hot air in the heater 15 for thermal desorption of the adsorption tower 11a in a one-through manner, and the subsequent cooling after heating bypasses the heater. After cooling to approximately room temperature, the waste gas is discharged from the outlet 14. In the case of heating, if the raw material gas before dehydration is at a high temperature, this heat is recovered and used as a heat source for desorption and regeneration. You can also do it. 20 is a second adsorption device for recovering toluene in the product CO gas vaporized in the CO vaporization tower A2 of equipment A and discharged from the outlet 2;
1 and 21a, and in the state shown in the figure, the product CO gas discharged from the outlet of the CO vaporization tower A2 is introduced from below into the adsorption tower 21, and in the adsorption tower 21, the product CO gas is The toluene entrained by the CO gas is adsorbed, the toluene is collected to 3 vol.ppm or less, and the toluene is sent as a high-purity product CO gas to the required plant etc. from the outlet 13. On the other hand, adsorption tower 2
1a is in the regeneration process, and a part of the crude raw material gas dried in the first adsorption device 10 is branched to the heater 16.
The toluene in the tower 21a is heated by heating and then introduced into the adsorption tower 21a from above to desorb the toluene in the tower 21a, and the desorbed toluene is returned to the dry raw material gas flow along with the gas flow, and the CO absorption It is sent to tower A1. The dry raw material gas is also used for cooling subsequent to the heating of the adsorption tower 21a, and the heater is bypassed to cool the adsorption tower 21a to approximately room temperature. This allows toluene to be recovered without being discharged outside the system. 30 is a third adsorption device for recovering toluene in the waste gas from which CO gas has been absorbed and removed from the crude raw material gas that has been dehydrated and sent to the CO absorption tower A1, and is a two-tower switching type adsorption tower 31, 31a. In the illustrated state, CO gas is absorbed and removed in the CO absorption tower A1, and the waste gas of the crude raw material gas discharged from the waste gas outlet 3 is introduced from below into the adsorption tower 31, and the waste gas is introduced into the adsorption tower 31 from below. 31, the toluene in the waste gas is adsorbed and recovered and discharged, heated through a heater 15, and then introduced from above into the adsorption tower 11a in the regeneration process of the first adsorption device 10, where it is thermally desorbed and cooled. After performing this, it is discharged from the outlet 14. On the other hand, the adsorption tower 31a is in the regeneration process, and the second adsorption device 20
Similar to the adsorption tower 21a in the regeneration process, a part of the crude raw material gas dried in the first adsorption device 10 is branched and heated by the heater 16 before being transferred to the adsorption tower 3.
1a from above to desorb the toluene in the column 31a, and the desorbed toluene is entrained in the gas flow and returned to the dry crude raw material gas flow;
It will be sent to the CO absorption tower A1. The cooling subsequent to heating also bypasses the heater 16 and cools to approximately room temperature. In addition, the second and third adsorption devices 20, 3
When the crude raw material gas before dehydration is at a high temperature during heating in the regeneration process at 0, this heat can be recovered and used as a heat source for desorption and regeneration, as in the case of the first adsorption device 10. Furthermore, in the Joki flow sheet, the adsorption towers 21a and 3
1a is heated by the same heater 16,
If the respective switching cycle times or regeneration schedule times are different, dedicated heaters can be provided for each. The above-mentioned first to third adsorption devices are attached to a CO gas absorption type separation equipment to constitute a process employing the method of the present invention. The comparison is as follows. First, when dehydrating and drying crude raw material gas, generally
A N ₂ circulation system is adopted, but this requires extra N ₂ gas as a gas source and also requires a regeneration blower, cooler, drain separator, pressure regulator, etc. that are unique to the circulation regeneration system. In addition, the number of automatic switching valves is almost twice as large as that in the present invention, which not only complicates the equipment and process, but also results in a poor drying level in the drying process, making it difficult to obtain a low dew point temperature. Next, regarding the recovery of toluene, in the method of cooling and liquefaction, it is usually cooled to around 6 to 10℃, but the toluene content in the product gas is
Kg/cm ² G at 10°C is 3400 vol.ppm, whereas in the case of the present invention, up to 3 vol.ppm can be adsorbed and recovered, so if a plant with a product CO gas production of 1000 Nm ³ /hr is operated for one year (8000 hr), It is calculated that 114 tons of toluene is consumed in the conventional cooling and liquefaction method, but in the method of the present invention, only 0.1 ton is consumed. There is also a method of recovering toluene using activated carbon adsorption and steaming desorption using a general solvent recovery system, but in this case as well, the equipment is
A condenser, decanter, solvent pump, drain pump, etc. are required, and since toluene is dissolved in the drain, the recovery rate is lower than the method of the present invention.Toluene in the drain causes pollution, so toluene in the drain should be removed. This is necessary. On the other hand, since the recovered toluene is saturated or more dissolved in water, it cannot be returned to the plant without dehydration, which not only complicates the process, but also requires an adsorption tower due to the corrosive nature of the equipment specific to steaming regeneration. , condensers, decanters, valves, piping, etc. must be made of expensive stainless steel. The above are the advantages of the method of the present invention, and if we look at them for each device, they are as follows. 1st adsorption device (1) Since it is a one-through regeneration of dried waste gas, it is not only possible to easily obtain a dew point temperature of -60℃ to -80℃ in the dehydration process, but also the device is simpler than the N circulation regeneration type. equipment costs can be reduced. (2) There is no process such as replacement with N ₂ in the regeneration process,
Easy to operate and less likely to malfunction. (3) Since there is no need for N ₂ for regeneration and operation is resource and energy efficient, annual operating costs can be reduced considerably. (4) Waste gas from regenerated exhaust does not cause any pollution when burned, so it can be used as fuel. (5) There is no need to reduce the pressure in the adsorption process or the regeneration process,
Processing can be performed at the pressure supplied during the process. Second adsorption device Compared to the cooling liquefaction toluene recovery device, (1) The toluene content remaining in the product gas is 3400 vol.ppm at a pressure of 4 Kg/cm ² G10°C in the cooling liquefaction method, but 3 vol.ppm in the method of the present invention. The recovery rate is extremely high as it is less than ppm. (2) The amount of toluene depleted per year is extremely large in the cooling liquefaction method, which affects the production cost of CO gas.
In the method of the present invention, it is almost negligible. (3) In the cooling liquefaction method, the toluene after liquefaction is returned to the system by a pump or the like, so there is no need for a pump, a recovery tank, a liquid level controller, etc., whereas the method of the present invention does not require these. In addition, compared to conventional solvent recovery equipment, (1) The conventional method uses a steaming desorption method, but this requires a process of drying the activated carbon after steaming, and the heat load of drying is large, making operation difficult. Although the cost would be excessive, this is not necessary in the method of the present invention, so the operating cost is extremely low. (2) After steaming and desorption, the water layer and toluene layer are separated in a decanter, but since the toluene is dissolved in the water side, it cannot be disposed of as waste water and the amount of toluene consumed is large; Since the water content is at or above the saturation solubility, it cannot be returned to the system as it is, and a toluene drying device is therefore required, further increasing operating costs. (3) The steaming desorption method requires a condenser, decanter, drain pump, toluene pump, etc., which not only complicates the equipment, but also requires the use of stainless steel in many parts due to corrosion problems.
Although the equipment cost is high, the method of the present invention does not have such a problem. (4) In the case of the conventional method, the pressure in the adsorption process must be reduced to near atmospheric pressure, which increases the size of the equipment and is uneconomical. Third adsorption device It is exactly the same as the second adsorption device, and both the cooling liquefaction method and the conventional solvent recovery method have problems such as equipment cost, operating cost, pollution problem, corrosion problem, consumption of toluene, etc., but the present invention There are no such problems with the method. Next, examples of the method of the present invention will be described. The converter gas (LDG) discharged from the converter was used as a crude raw material gas and processed under the conditions of pressure 5 Kg/cm ² G, temperature 10° C., moisture saturation, and component composition shown in Table 1.

[Table] The above gas was first introduced into the first adsorption device and adsorbed and dehydrated, resulting in drying to a dew point temperature of -72°C. The adsorption tower was regenerated by thermal desorption and cooling using waste gas from which the toluene content was reduced to 2 vol.ppm in the third adsorption device. The composition of the waste gas at that time was as shown in Table 2.

[Table] Part of the crude raw material gas (LDG) that has been dehydrated and dried in the first adsorption device is branched and the toluene in the second and third adsorption devices is used for desorption and regeneration, so it is heated and used for desorption and regeneration. After being sent to the equipment for regeneration, it was combined with some other gas and supplied to the CO gas absorption and purification equipment. From this equipment, the product gas and the remaining waste gas are separated, both of which contain toluene and flow out. The product gas is cooled to a temperature of 10°C at a pressure of 4 Kg/cm ² G and contains 3400 vol.ppm of toluene, which is passed to the adsorption tower that is not being regenerated in the second adsorption device to adsorb toluene. As a result, the toluene concentration in the device outlet gas was 2 vol.ppm.
I was able to reduce it to below. The composition of the product gas at that time was as shown in Table 3.

[Table] In addition, the waste gas has a pressure of 4.5Kg/cm ² G, a temperature of 12℃,
Toluene is discharged from the CO absorption and purification equipment with a concentration of 3600 vol.ppm, but by passing it through the adsorption tower that has not been regenerated in the third adsorption device and adsorbing toluene, the toluene concentration after passing can be reduced.
We were able to remove it to less than 2vol.ppm. The composition of this gas is shown in Table 2. As a result, according to the method of the present invention, the crude raw material gas can be dried to a dew point temperature of -72°C, the toluene in the product gas can be reduced to 2 vol.ppm or less, and the toluene in the waste gas can be dried to a dew point of -72°C. It has also become clear that the amount can be reduced to 2vol.ppm. Incidentally, the recovery rate of toluene was 99.9%. The present invention is as described above, and includes an adsorption device attached to CO gas absorption type separation equipment according to the method of the present invention.
By configuring a CO gas separation and purification device, the configuration of the device can be made extremely simple, which not only reduces the cost of the device. There are only three outlets: the outlet for product gas and the outlet for waste gas that can be used as fuel, and there is no element of pollution. In addition, since moisture does not coexist, there is no risk of equipment corrosion, the operating cost is extremely low compared to other methods, and there is no need for regeneration gas such as _N2 gas.
Furthermore, when the crude raw material gas is at a high temperature, the heat can be utilized, and a number of effects that cannot be expected with conventional methods are produced, making it extremely useful industrially.

[Brief explanation of the drawing]

The figure is a process sheet for CO gas absorption type separation equipment that employs the method of the present invention. A... CO gas absorption separation equipment, 10... 1st
Adsorption device, 20...second adsorption device, 30...third
Adsorption device, 11, 11a... Crude gas dehumidification adsorption tower, 12... Crude gas inlet, 13... Product gas outlet, 14... Waste gas outlet, 15... First adsorption device regeneration heater, 16... Second and third adsorption device regeneration heaters, 17... Flow rate control valve for branching dry raw material gas and controlling flow rate, 21, 21a...
Toluene adsorption tower in product gas, 31, 31a...
Toluene adsorption tower in waste gas.

Claims (1)

[Claims] 1. In a method for regenerating an adsorption device for CO gas absorption type separation equipment using a toluene solution of complex salts such as aluminum chloride and cuprous chloride, etc., drying of crude raw material gas, recovery of toluene in product gas, and recovery of toluene in waste gas. The recovery of each column is carried out using a switching type adsorption device with two columns, and in the drying process of crude raw material gas, while one column is in the drying process, the other column uses the waste gas discharged from the equipment. In the recovery process of product CO gas and toluene in waste gas, while one tower is in the recovery process adsorbing and recovering toluene, the other tower is It is characterized in that a part of the crude raw material gas after drying is used in a branched manner to carry out the regeneration process of thermal desorption and cooling of toluene.
A method for regenerating an adsorption device for CO gas absorption type separation equipment.