DE102006032609A1 - Recovering halogenated hydrocarbons, especially inhalation anaesthetics from sorption filters, involves passing hot water vapour through a hydrophobic active carbon bed and then a hydrophobic zeolite bed - Google Patents

Abstract

A method for recovering halogenated hydrocarbons (I), especially inhalation anaesthetics removed as associated gases and kept on sorption filters for later release, more especially for removing (I) from expired gases with a water vapor carrier, involves passing an air/water vapour mixture or water vapour through two sorption beds in series containing hydrophobic molecular sieve carbon and hydrophobic zeolite respectively, the gas temperature being 90-100[deg]C at normal pressure. An independent claim is included for a filter for the above method, comprising two filter beds arranged in series.

Description

The Invention relates to a process for the recovery of halogenated hydrocarbons, in particular inhalation anesthetics and a filter on it.

State of the art

sorption become common used for separation, purification and drying of gases. For low-boiling halogenated hydrocarbons (HKW) requirements that dictate environmental demands become.

Easily vaporizable anesthetics commonly used in medical practice, such as enflurane, isoflurane, sevoflurane, and desflurane, are fluorine- and chlorine-substituted hydrocarbons or ethers, which are usually completely released into the environment during or after anesthesia and can harm patients and medical personnel. They also contribute to the "ozone hole" or the "greenhouse effect". An estimate based on the Member States of the EU showed that in 1995 alone there was a pollution of the atmosphere with approximately 700 tonnes of inhalation anesthetics. This amount corresponds to an additional carbon dioxide loading of 0.25% [ Zeitschrift. Anesthesiology u. Intensivmed. 6 (39), 301-306, 1998 ]. In the productive processing as well as the recovery of HKW from exhaust air, in particular from patients with inhalation anesthetics loaded expiratory air of patients, it is a concern to aim for an economically favorable design of the sorption and related processes.

Single-stage filter arrangements.

Reactive activated carbons are already suitable for the purification of process or exhaust air ( DE 37 13 346 . DE 39 35 094 and DE 40 03 668 ). The prerequisites for high sorption capacity combined with optimum regenerability are already in the literature DD 239 947 . DE 36 28 858 and DE 37 31 688 explained. The recovery of HKW can be done with a high degree of recovery by desorption under high temperatures and low pressures. As a result of the heat treatment, however, structural damage to the sorbents as well as the formation of halogen-containing decomposition products of HKW occur.

In DE 37 13 346 and DE 195 49 271 . DE 42 33 577 the removal of HKW by zeolites is described. For sorption of inhalation anesthetics, zeolites have high thermal stability and low catalytic activity for toxic product formation. Recently, low-aluminum and dealuminated zeolites are used as sorbents ( DE 195 32 500 ) used.

As is known, after separation and recovery of inhalation anesthetics on activated charcoal or zeolite filters, further associated gases were merely post-combusted ( DE 42 08 521 ). Thus, recoverable drugs are irrecoverably removed from the filters. In activated carbons with a wide pore spectrum, however, HFCs in the narrow pores are permanently adsorbed. In the recovery of inhalation anesthetics ( DE 43 08 940 and DE 195 49 271 ) high desorption temperatures lead to medically problematic by-products.

For the recovery of HKW hydrophobic zeolitic molecular sieves are used with narrow pore distribution ( EP 0 284 227 ). The desorption takes place below 150 ° C. The inhalation anesthetics are condensed out and recovered. In this case, decomposition products can not be excluded.

Already advantageously used as sorbents the process adapted dealuminated zeolites ( DE 197 49 963 ). The sorbed HKW be desorbed by heating, condensed and recovered. Due to high vapor pressures of the anesthetics, the condensation must be in the range of 2 ° C to 8 ° C. The desorption of isoflurane is carried out under vacuum (about 10 mbar) and with simultaneous heating to about 100 ° C to 160 ° C. The maximum desorption temperature is thus about 60 ° lower than that for activated carbon. Desflurane is desorbed between 90 ° C and 130 ° C.

In a DE 101 18 768 For a filter cartridge, the gentle regeneration with a steam carrier is described. Modified and / or dealuminated zeolites with low water absorption below Ma-2% cause the sorbent and the sorbate gently lowering the desorption temperature. It is advantageous to set a saturated steam temperature under normal pressure around 100 ° C. The condensation of the gases leads to the formation of a geschichtar term pre-separated liquid mixture. The specific lighter thing This layer is returned to the evaporation process while the heavier layer of inhalation anesthetics is post-purified. However, possible degradation products accumulate in the water layer.

Conventional filter arrangements with zeolites have different characteristics of their parameters with regard to adsorption and desorption of inhalation anesthetics, which depend substantially on the conditions of flow and temperature. In order to achieve a standardization of the process control during regeneration without a time delay (hysteresis), a different energy supply is caused, for example, for a filter cartridge, wherein the adsorbed anesthetics can be released from the inside of the cartridge targeted ( EP 0 611 174 . EP 1 222 940 ). Differently acting sorbents in combination are not yet used. Also, specially designed embodiments of filter cartridges for breathing gases are common in order to evenly consume fillings at higher flow velocities ( DE 36 12 924 ) and to avoid local breakthroughs through the filter layer.

In its own suggestion "filter cartridge for recovery low-boiling halogenated hydrocarbons "becomes the gas passage in the upper wall portion of a single filter cartridge designed so that In this area, a plug flow for the gases is formed, wherein a homogenization of the breakthrough curves for inhalation anesthetics is achieved. The anesthetic gases used thus have at the top Edge of the filter insert with the hydrophobic zeolites "good" breakthrough curves on, that is with a steep and clear local as well as timed characteristic of the transition, putting a sharp border between the loaded and still unloaded parts of the Zeolithschüttung trains.

The in the complex complex filtering system is confusing and leaves for his Timing a possible Determination of best values only on the basis of a long-term and empirical Gain of work experience too. One particular problem is one Arrangement in several sorbent beds, in particular of in the Medical technology manageable filters a steep characteristic of the Breakthrough curves with exactly determinable times should have.

Multi-stage filter arrangements

There has been no lack of attempts to increase the degree of loading of sorption beds in the targeted purification of gas streams. In a DE 43 19 327 a crude gas stream is passed aufein ander following through two sorption beds. After completion of the process, the first sorbent bed is regenerated and the direction of flow reversed, so that the second bed is flowed through first. However, the used sorbent is laboriously replaced by a freshly regenerated one.

According to one DE 198 26 684 For example, a gas mixture is contacted with a sorbent at a higher pressure, wherein a component of the mixture is preferably sorbed in a first working stage and desorbed in a second stage under reduced pressure. Both areas are separated from each other so that only the sorbed component crosses into the second area. It combines a rectification of low-boiling gas components with a pressure swing adsorption. The mechanical device for this is complicated and does not meet the requirements of simple filter arrangements.

It is also state of the art that an improvement in sorptive separation is made possible by physical differences, for example in pore sizes, and by changes in the sorbent beds themselves. With unequal gas components, as in the DE 197 06 806 which form mixed proportions of nitrous oxide and anesthetic vapor, their selective separation can be carried out by various molecular sieve types. These can be used mixed together or combined in two different sorbent beds. They have different pore sizes, which could also lead to temporal differences in the processes of sorption. There are two Molsiebbereiche each with different ranges of pore sizes, from 0.8 to 1 nm and 0.3 to 0.5 nm provided, which are flowed through spatially successive. Although good adsorption properties are claimed for both gases, they are made possible on the basis of purely steric and thus static influences in the adjustment of the sorption equilibria. A recovery by means of a carrier gas or vapor is not considered yet. In particular, it is not taken into account that at higher sorption capacities than zeolitic molecular sieves, such as molecular sieve coals, particular dynamic influences occur which additionally improve the sorption properties as well as the recovery of the anesthetics by regeneration by water vapor.

Process control on HKW filters:

In Previous filter arrangements, the process control is essentially by macroscopic definable conditions such as according to geometry and operating parameters fairly controlled. The selectivity In the case of substance separations by sorption, on the other hand, it is necessary determined microscopic parameters. Differences in molecular size in spatial Lattice structure of the sorbents cause static sieving effects as well as obstructions at the grating passage. In contrast, the timing is these separation processes in the associated Filter through a complicated and dynamically acting kinetics with pronounced Imperfections established.

Improvements of sorptive material separations can be provided by changes in the process management. In a monograph " Adsorption process for water purification "by Sontheimer, Frick, Greasy, Horns, Hubele and Zimmer, DVGW Research Center at the Engler-Bunte Institute of the Technical University Karlsruhe, Karlsruhe 1985 at least two-stage procedures are proposed in cocurrent for successively arranged sorption beds, their calculations lead to the best possible values of the final concentrations after the first or further sorption and allow a favorable distribution of the masses of similar sorbents on several sorption beds for a given total mass. These findings are based on set sorption equilibria and can be transferred to filter arrangements for HKW. In particular, it has been known that carbon molecular sieves suitable for the sorption of inhalation anesthetics often have a higher loading than zeolites. However, carbon molecular sieves, in contrast to zeolites, have an unfavorable breakthrough behavior with insufficient utilization of the capacity of the filters. The desorption curves on activated carbons are disadvantageously flatter, and their sorption capacity is advantageously higher.

zeolites already have high load values for halogenated hydrocarbons. However, activated carbons have low desorption temperatures a higher one Substance turnover and can to clean the exhaust air better.

at the determination of breakthrough times on filter assemblies of breakthrough curves it follows that when desorbing a filter with a zeolite shorter Times of breakthrough set with steep curves become. In contrast, using molecular sieve coals longer Breakthrough times observed with flat course of breakthrough curves. The individual static and dynamic parameters are with filters for HKW and inhalation anesthetics difficult to separate from each other and therefore can hardly independently to be examined. That is why it is difficult to get the individual benefits a use of different effective sorbents without optimization to use. It is therefore an urgent matter, the purposefully common Interconnection of at least two sorbent beds of a filter arrangement set.

It has not yet been found that a combination of hydrophobic zeolites with activated carbons of a best value determination of shares in at least two sorption beds of filters for inhalation anesthetics is.

Object of the invention:

It The task is to develop a procedure in which the in the state of Technique described disadvantages can be eliminated.

Characteristic of the specific solution:

The Task became according to the characteristics of the claims solved. According to the invention was a method is provided, wherein for a two-stage filter arrangement a spatially Separate sorption of different absorbable amounts of substance temporal influences justified becomes.

This ensures that a first sorption bed with a hydrophobic molecular sieve charcoal before a second sorption bed with a hydrophobic zeolite in series (one behind the other) are connected. Both represent each a process stage and are flowed through by the Sorptiv spatially successive. Bude stages have a common throughput parameter for the carrier gas, especially for air as well as in the regeneration of the regenerant water vapor. These process variables are naturally dependent on the gas pressure and on the temperature and on the gas flow rate of the carrier gas. The filter assembly may be continuous in a production or gas purification plant or may be configured as a regenerable and suitably evacuated filter cartridge. It becomes a sorption from the carrier gas, in particular a desorption in the carrier gas and a distillation with saturated steam combined. Under normal pressure, the temperatures for regeneration are lowered by up to 10 ° C and the sorbents and sorbates are thermally protected. It is possible to additionally lower the temperatures for the regeneration by lowering the pressure as a result of applying a vacuum. The velocities of the expiratory gases in the flow through the successive stages are 0.2-0.3 m / s, the regeneration-related vapor velocities during regeneration up to 0.4 m ³ / (m ² h), without the breakthrough curves be significantly deformed. The unfavorable breakthrough curves of the carbon filter bed is converted into a favorable by the additional zeolite bed in the filter assembly.

Zeolites with an inner surface of preferably 800-1000 m ² / g, with an average pore diameter of about 0.8 nm are used. Particularly advantageous is the use of dealuminated zeolites and those of the faujasite type. As molecular sieve coals are substances having inner surfaces of preferably 1000-1400 m ² / g and with an average pore diameter of 0.5 to 1 nm in question.

The The invention is illustrated by examples with two tables, without the invention limited to these examples becomes. The only one associated Figure shows: Filter arrangement with two sorption beds and characteristic Breakthrough curves and the following optimization procedure:

Optimization:

embodiments

Example 1:

An inhalation anesthetic, under mild conditions of 20 ° C-30 ° C and under normal pressure, flows through a combined filter comprising an activated charcoal bed and a bed of zeolite. The cross-sectional flow velocities on the filter beds are set at about 0.05 m / s according to Table 1 so that within the two stages there is almost a sorption equilibrium between the sorbents and the anesthetic. Table 1: Optimized parameters of a two-stage sorption parameter Stage no. value dimension inlet concentration 1 5.0 mol.l ^-1 2 1.2 output levels 1 1.2 mol.l ^-1 2 0.05 corrected bed volumes 1 1.5 1 2 0.5 Constants of the Freundlich Isotherms 1 3.0 mol ^1-n · l ⁿ · kg ^-1 2 2.0 Exponents of the Friendly Isotherms 1 0.5 - 2 0.2 Loads of I sorbents 1 3.3 kg / kg sorbent 2 1.9 Quantities of sorbents 1 1.7 kg 2 0.3

Example 2:

• – maximale Beladungen q_max;
• – mittlere Durchbruchzeiten t_B mit der Basis von 5% des Durchbruchbeginns und 95% des Durchbruchendes,
• – mittlere zeitliche Halbwertsbreiten Δt_B für die Durchbruchszeiten,
• – relative zeitliche Halbwertsbreiten Δt_B/t_B dazu
• – die Massenübergangszone MTZ = 2·w_B·Δt_B, bezogen auf die Bettlängen Z; bei denen die auf den Strömungsquerschnitt bezogenen Geschwindigkeiten W_B = 0,2 m/s sind
• – und der qualitative Verlauf der Durchbruchkurven.

Tabelle 2: Verläufe von Durchbruchskurven an Molekularsiebkohlen und Zeolithen Sorbens Typ q_max, kg/kg t_B, min Δt_B, min Δt_B/t_B, – MTZ/Z, – DBK-Verlauf Molsiebkohlen Typ 1 0,35 120 22 0,18 7,2 flach Typ 2 0,78 270 45 0,17 2,4 mäßig flach Zeolithe Z-700, fein 0,21 62 5 0,08 1,2 steil Z-700 0,26 74 8 0,11 1,8 steil TZF 0,26 91 12 0,13 2,0 steil In each case, 50 g of sorbent are introduced and passed through with sevoflurane, which is contained at 1.5% air at 28 ° C. According to Table 2, molecular sieve coals and zeolites were determined as follows:

• - maximum loads q _max ;
• - average breakthrough times t _B with the base of 5% of breakthrough start and 95% of breakthrough end,
• Mean time width half widths Δt _B for the breakthrough times,
• - relative temporal half-widths Δt _B / t _B to this
• - The mass transfer zone MTZ = 2 · w _B · Δt _B , based on the bed lengths Z; in which the related to the flow cross-section speeds W _B = 0.2 m / s
• - and the qualitative course of breakthrough curves.

Table 2: Course of breakthrough curves on molecular sieves and zeolites sorbent Type q _max , kg / kg t _B , min Δt _B , min Δt _B / t _B , - MTZ / Z, - DBK history Molsiebkohlen Type 1 0.35 120 22 0.18 7.2 flat Type 2 0.78 270 45 0.17 2.4 moderately flat zeolites Z-700, fine 0.21 62 5 0.08 1.2 steep Z-700 0.26 74 8th 0.11 1.8 steep TZF 0.26 91 12 0.13 2.0 steep

The Molecular sieves have advantages because of their high capacity, the zeolites due to their steeper breakthrough curves.

B

auf Sorbensbett bezogen

i

Stufenzahl

max

größtmöglichst

T

total; gesamt

0

Stufeneingang

1

1. Stufe

2

2. Stufe

indices

B

based on sorbent bed

i

number of stages

Max

greatest possible extent

T

total; total

0

stage input

1

1st stage

2

2nd stage

Claims (8)

Process for the recovery of halogenated hydrocarbons, especially for inhalation anesthetics, wherein the halogenated hydrocarbons removed from associated gases and / or temporarily temporarily stored on sorption filters and targeted to be released again and especially the removal of Serve expiration gases using a steam carrier, characterized in that in two sorbent beds spatially consecutive a hydrophobic molecular sieve charcoal and a hydrophobic zeolite flows through be, with the added water vapor or water vapor At atmospheric pressure, a temperature of the gases between 90 ° C and 100 ° C has. A method according to claim 1, characterized in that the molecular sieve has inner surfaces of preferably 1000-1400 m ² / g and average pore diameters of 0.5 to 1 nm. A method according to claim 1 and 2, characterized in that the zeolites have an inner surface of preferably 800-1000 m ² / g and average pore diameters of about 0.6 to 0.8 nm. Method according to claim 3, characterized in that that the zeolites are in particular of the faujasite type and have a water absorption capacity of below 2% by mass. Method according to claims 1 to 4, characterized by that by a pressure reduction, the temperatures for regeneration sorbents in addition be lowered. A method according to claim 5, characterized in that the velocities of the expiration gases are 0.2-0.3 m / s and the vapor flow rates related to the flow cross section during regeneration are up to 0.4 m ³ / (m ² h). Filter for carrying the method according to any one of claims 1 to 6, characterized in that two filter beds arranged spatially sequentially are. Filter according to claim 7, characterized in that the loading conditions and the proportions Both sorbents on their respective times for the breakthrough are tuned by the respective filter bed.