ES2334541A1 - Procedure for the regeneration of carbon materials adsorbients with water vapor (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Procedure for the regeneration of adsorbent carbonaceous materials with water vapor. Process for the regeneration of carbonaceous adsorbent materials based on the gasification reaction with water vapor of the substances adsorbed by said materials, using temperatures above 550ºC and a pressure between 25 and 175 bar. The invention also relates to a system for carrying out said method. (Machine-translation by Google Translate, not legally binding)

Description

Procedure for the regeneration of materials carbonaceous adsorbents with water vapor.

The present invention relates to a procedure for the regeneration of carbonaceous materials adsorbents already depleted, based on the degradation reaction with water vapor, at moderate pressure, of contaminants retained

Prior art

Activated carbon is a carbonaceous material, highly porous, with a high surface area and some exceptional adsorbent properties; generally the size of Pore is very small (micropores with diameters smaller than 2 nm).

The carbonaceous material from which it is constituted it has a real density close to 2 g / cm3, however, given the large porosity has an apparent density between 0.5-0.6 g / cm3.

It is manufactured from a wide variety of Carbon-rich materials, such as: wood, coconut shell and other fruits, bones of olives and other fruits, as well as coal mineral (peat, brown coal, coal and anthracite). Starting material conditions the properties of the activated carbon that is obtained, especially porosity and hardness.

Activated carbon has multiple applications since it is capable of removing virtually any compound organic that is in the gas or liquid phase. Currently used in many industries, but it is the water treatment of human consumption and wastewater that demand it most.

During the regeneration process the coal exhausted is subjected to those conditions in which the Adsorption balance in favor of desorption. This balance shifting can be achieved by procedures very diverse, such as: raising the temperature, changing the acid-base ionization equilibrium, extracting the substances retained with appropriate solvents, etc. In general the Regeneration procedures can be classified into three large Groups: thermal, chemical and biological methods. Of all of them, the temperature increase is the one that allows faster and efficiency in desorption, for this reason thermal regeneration is the most common procedure, although today they are emerging Other methods that provide good results.

One of these methods is regeneration with steam in which the spent carbon is subjected to the action of steam from water at temperatures between 160-240ºC, under pressure atmospheric Under these conditions, water vapor raises quickly the temperature of the coal and favors desorption. In addition to cooling, water vapor condenses and adsorbs on the  surface of the coal, displacing the adsorbed compounds, with which improves the desorption process.

It is a regeneration method especially designed for the recovery of carbons used in disposal of organic solvents. Its effectiveness in this field is high, although It is strongly conditioned by the amount of steam used. For other carbons contaminated with other compounds the effectiveness It is quite minor and in all cases has the disadvantage of that retained substances are not destroyed during the process being released

Another of the regeneration methods is based on the thermal desorption of the compounds retained by activated carbon, using liquid water under subcritical conditions, that is, at temperatures and pressures lower than those of the critical point (critical point of water: critical temperature: 374.10 ° C and critical pressure: 223.7 bar) at which dissolved oxygen has been removed (Salvador, F. and Sánchez Jiménez, C., 1996, Carbon , 34 (4), 511-516). Liquid water in these conditions is capable of desorbing and / or extracting contaminants that are adsorbed in activated carbon. In this way, the original adsorption capacity of the coal is recovered. The main drawbacks of this method are that it requires the use of high pressures and high water consumption, resulting in the recovery of the smallest microporosity being very difficult. On the other hand, pollutants are not destroyed, being released.

Another method is the regeneration with water supercritical adsorbent carbonaceous materials (ES2127113 A1). In this procedure the spent carbon is regenerated by treatment with supercritical water, that is to say with water that found at a temperature and pressure higher than its critical point. Water in these conditions is a fluid capable of tear off or remove from the surface of spent carbon the compounds there retained. The regeneration procedure is complete with the destruction of desorbed contaminants by adding an oxidant to the water stream supercritical after crossing the bed of coal.

Supercritical water regeneration is very effective, requires very short treatment times and temperatures less than 600ºC. Water consumption is moderate and is closely related to the effectiveness of the regeneration.

However, it has the disadvantage that at use very high pressures, greater than 250 bar, and temperatures elevated, the facilities are very expensive and difficult to handle. In addition the total destruction of the desorbed contaminant requires a post oxidation treatment. That treatment originates corrosion problems in the facilities, demanding the use of special materials that make the process more expensive.

Description of the invention

The present invention relates to a regeneration process of adsorbent carbonaceous materials, such as activated carbons and activated carbon fibers, by treating it with water vapor at temperatures preferably higher than 600-625 ° C and pressures moderate around 75 bar (7.5.10 6 Pa).

The invention simplifies the regeneration procedure with respect to procedures previous known by a person skilled in the art, with the objective of its viability on an industrial scale.

Under these conditions regeneration occurs mainly because the pollutant (in most cases organic compounds) is destroyed by a process of gasification due to the hydrolytic action of water at high temperature:

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This decomposition can occur while the contaminant adsorbed on the surface of the coal. What facilitates its removal from the surface, thus accelerating the adsorbent regeneration.

It can also happen that high temperature facilitate desorption of the contaminant without decomposing it, decomposition occurring once you have left the surface.

Activated carbon can also be attacked by the water gasifying it:

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However, this attack is much slower and It only happens if the temperature is very high. Studies conducted in the laboratory shows that at 625ºC the contaminants are they gasify quickly, while activated carbon makes it very slowly. According to these studies, with a treatment time of 5-7 minutes you can get a 95-100% of the regeneration. However, during This time the amount of gassed coal is negligible. So then, selecting the temperature you can get the degradation of pollutants without causing mass losses in activated carbon

The pressure used is the minimum pressure necessary for water vapor to penetrate the porosity more Fine coal and regenerate. Therefore, the pressure is also a key factor in the regeneration process by favoring the water penetration into the microporous structure of coal. The studies show that with a pressure of about 75 bar is enough for water vapor to enter the entire porous structure of most activated carbons trade and regenerate them. However, lower pressures could be enough for those coals that had a very wide microporosity and higher pressures would be necessary to regenerate ultramicroporous coals. These last two types Coals are very rare.

Water in the regeneration process of The present invention performs different functions:

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Act as a chemical reagent in the hydrolysis or gasification of pollutants However, in the regeneration with water Supercritical acts as a solvent or extractant. This difference It is especially important since acting as a chemical reagent The amount of water needed is much smaller.

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further acts as a means of heat transport, heating the structure porous of the coal, and can also perform thermal desorption of adsorbed contaminates.

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How means of transporting desorbed and degraded products, from the inside of the pores to the outside.

When water acts as a reagent, it is not they need large quantities, being sufficient that it is in excess against the contaminant. Generally spent carbon can store 10% by weight of contaminants so the amount of water to be used must be greater than 10% by weight of coal at regenerate.

Being the amount of water to heat very Small makes the process very economical.

The water stream after leaving the coal bed can partially carry contaminants degraded or not degraded. To achieve much more degradation full water stream can be maintained at the temperature of regeneration or higher for a sufficient time for it to Degrade all contaminants.

The differences between water regeneration supercritical and with moderate pressure water vapor are the following:

With supercritical water the water used is found in a supercritical state, that is, at higher temperatures of 374.10ºC, using temperatures close to 600ºC, and high pressures, greater than 223.7 bar; while with steam of water, the water is in a state of steam, and although the temperature is high the pressure is much lower than in the Supercritical water regeneration. This introduces great simplifications in the design and management of facilities, making them also much cheaper.

With supercritical water, the regeneration is produced as a result of the extraction or dissolution of contaminants retained on the surface, so that the supercritical water acts as a solvent, and the amount of water necessary is high, and has a great influence on the duration of process; while with steam, the regeneration is produces as a consequence of the chemical reaction of water with contaminants retained. Being a chemical reaction the process speed is controlled by the proportion water / contaminant This implies that water consumption is very small and therefore also energy expenditure.

With supercritical water, the destruction of pollutants are performed at a later stage by oxidation of the same in supercritical conditions. Supercritical oxidation of pollutants complicates the regeneration process by having that add an oxidant, and is cause for greater corrosion in the equipment. On the other hand, with water vapor, the regeneration of coal and the destruction of pollutants is done in a single stage, without addition of reagents. This means less corrosion in the installation, as well as a simplification of the process and a lower economic cost.

Therefore, a first aspect of the present invention relates to a process for the regeneration of carbonaceous adsorbent materials comprising a reaction of gasification of contaminants retained in these materials by treating it with water vapor at a higher temperature at 550 ° C. and at a pressure of between 25 and 175 bars. Preferably the temperature can be between 600-625 ° C and the pressure can be between 50 and 100 bars and more preferably around 75 bar.

Adsorbent carbonaceous materials are materials carbon such as activated carbon or carbon fibers activated

A second aspect of the present invention is refers to a system of regeneration of carbonaceous materials adsorbents by the process of the invention.

Throughout the description and the claims the word "comprises" and its variants not they intend to exclude other technical characteristics, components or Steps. For experts in the field, other objects, advantages and features of the invention will be apparent in part from the description and in part of the practice of the invention.

To complement the description that is being performing and in order to help a better understanding of the characteristics of the invention, according to one or a few examples of practical realization of it, is accompanied as part member of this description, a set of drawings with character Illustrative and not limiting.

Brief description of the figures

Fig. 1.- Shows a schematic elevation view of a reactor for carrying out the process of the invention.

Fig. 2.- Represents a schematic view of a reactor similar to that of Fig. 1, in which the regeneration water is introduced by the upper and lower part of the hot zone of said reactor.

Fig. 3.- Represents a schematic view of a reactor similar to that of Fig. 1 in which another reactor is coupled, a heat exchanger and a cooling medium.

Detailed statement of embodiments

The invention will be illustrated below by means of embodiments or examples that are not intended Limit it.

Example 1

Being a very fast process, which use high temperatures and moderate pressures, the procedure more advisable would be to use a continuous process. In Fig. 1 the scheme of a reactor to perform said process.

It is a tubular reactor (10), placed vertically, with a widening at the top (11) and another at the bottom (12). The one at the top (11) is destined to store the coal that you want to regenerate. He bottom (12) collects the regenerated carbon.

The coal passes to the bottom (12) of continuous way by gravity, thanks to a vane dispenser (13), or other similar device known to any expert in The matter. The speed with which it passes is controlled with the speed of rotation of the vanes.

The bed of coal located in the central part of the reactor is kept warm at the process temperature, which is about 625 ° C by a metal tube concentric (14) inside which there is an electrical resistance. This radial heating from the center of the bed, towards the Exterior has the following advantages:

It is very effective, by taking advantage of all the heat of the heating bar.

It is very fast to directly affect coal.

Outer wall of the reactor will be at a lower temperature than inside, thus increasing the mechanical strength of the walls of the reactor.

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The hot zone of the reactor (17) where it has place the regeneration treatment is kept separate from the cold storage and collection areas thanks to some shirts refrigerators (15).

The bed temperature is measured with different thermocouples (16). A temperature programmer controls the heating of the heating bar.

The regeneration water must be introduced into the hot zone of the reactor (17), from the bottom (18), to a pressure of about 75 bar and in countercurrent with the bed of carbon, to prevent desorbed or degraded contaminants they are re-adsorbed on the regenerated carbon, and it leaves by the upper part (19).

The only drawback is that if the flow of water vapor is large could prevent the carbon from falling by gravity. This inconvenience can be saved depending on the bed height, reactor section and water flow (by increasing the height of the bed the weight of the bed increases, and at increase the section, the speed of the water flow decreases).

The coal can be loaded and removed easily from the reactor by dragging with water.

When the coal stored on top has been regenerated, passing all of it to the bottom, the process regeneration ends, and it is necessary to reload the reactor, so the process cannot be considered as continuous but as semi-continuous, so that autonomy is conditioned by the storage and collection capacity.

Other facilities are possible especially if a discontinuous regeneration process is chosen.

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Example 2

Another embodiment is seen in Fig. 2, where water is introduced into the hot zone (17) of the reactor (10) by the upper part (19), which favors the movement of the bed down, and at the bottom (18), which prevents the pollutants are re-absorbed in the regenerated carbon, and remove it by an intermediate zone (20), such that the flow of water that enter from the top (19) is greater than the one that enters through the lower part (18), and thus achieve the descent of the bed.

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Example 3

As shown in Fig. 3, the current effluent (1) from the reactor (10) can be taken to another degradation reactor (21), where the temperature is maintained or increases, remaining the time necessary for the completion of the degradation of pollutants

For greater energy use there the possibility of placing a heat exchanger next (22) that would allow preheating the regeneration water (18) that enters the main reactor (10).

Finally the effluent stream cools by means of a cooling system (23) before going through a pressure regulating valve (24) with which the pressure in the installation and the effluent solution is discharged to atmospheric pressure.

In general, for all embodiments water can be introduced into the reactor (10) with a pump of membrane or piston, or the like, that can provide a pressure higher than the process (75 bar). The piston is more advisable because it keeps the flow more constant although there are variations of the pressure in the reactor; however, it has the disadvantage of possible losses from the plunger, demanding more control and maintenance.

The most recommended materials for the zones in which the temperature is high they are: Inconel 625, Inconel 718, Hastelloy C-276, etc. The tubular reactor and the bar heater could be protected from corrosion by a ceramic shirt

The installation must be protected against overpressure with relief valves and rupture and front discs to overheating.

Claims (13)

1. Procedure for the regeneration of adsorbent carbonaceous materials by a reaction of gasification of contaminants retained in said materials and which includes its treatment with water vapor at a temperature above 550ºC and at a pressure between 25 and 175 bars. 2. Method according to claim 1, where the temperature used is between 600ºC and 625ºC. 3. Procedure according to any of the claims 1 or 2, wherein the pressure used is between 50 and 100 bars 4. Method according to claim 3, where the pressure used is about 75 bar. 5. Procedure according to any of the claims 1 to 4, wherein the desorbed contaminants thermally they also degrade in the same procedure. 6. Procedure according to any of the claims 1 to 5, wherein the carbonaceous material is carbon activated. 7. Procedure according to any of the claims 1 to 5, wherein the carbonaceous material is a fiber of activated carbon. 8. System of regeneration of carbonaceous adsorbent materials with water vapor characterized in that it comprises:

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a tubular and vertical reactor (10) comprising:

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a superior cold zone (11) intended to store the coal that you want to regenerate,

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an intermediate hot zone (17) where regeneration occurs, in which a tube is found metallic (14) equipped with a heating resistance inside the bed of coal,

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a lower cold zone (12) intended to store the regenerated carbon,

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nail cooling jackets (15) that hug the tubular reactor (10) between the intermediate hot zone (17) and the cold zones (11, 17),

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some conduits (18, 19) connected to the intermediate hot zone (17) through which circulates, enters and / or leaves regeneration water.

9. System according to claim 8, characterized in that the reactor internally has a vane dispenser (13) prior to the lower cold zone (12). 10. System according to any of claims 8 or 9, characterized in that the ducts (18, 19) comprise:

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a upper duct (19) located at the top of the area hot intermediate,

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a lower duct (18) located in the lower part of the area hot intermediate.

A system according to any one of claims 8 to 10, characterized in that it additionally comprises an intermediate conduit (20) that starts from the reactor (10) and is located between the upper (19) and lower (18) conduits, becoming an outlet conduit of the reactor (10), while the upper (19) and lower (18) conduits are constituted into water inlet conduits to the reactor (10). A system according to any one of claims 8 to 11, characterized in that it further comprises a degradation reactor (21) that receives an output current from the reactor (1) to complete the degradation of the contaminants. 13. System according to claim 12, characterized in that it further comprises a heat exchanger (22) that preheats the regeneration water entering the reactor (10).