DE19947444A1 - New gas pump, useful for collection of used anesthesia gases, comprises a compressor unit with controllable temperature - Google Patents

Abstract

A gas pump in a system for collection of used anesthesia gases comprising a compressor unit fully immersed in a water bath with controllable temperature, is new. An Independent claim is also included for collection of used anaesthesia gases comprising compression of the gas without preliminary drying and/or analysis.

Description

The invention relates to a gas pump and its use for recovery of anesthetic gas when ventilating a patient with anesthetic gas.

Gas pumps or gas compressors are usually only for dry gases Suitable, because otherwise only short downtimes are achieved due to corrosion the.

Conventional compressors are cooled today by either air cooling or water cooling directly cool the actual cylinder or / and a heat exchanger is connected downstream.

Gas pumps for high pressures are in "Ullmann's Encyclopedia of Technical Chemistry, 4th edition, volume 3: Process engineering II and reaction apparatus, Ka Chapter: Printing technology, Verlag Chemie, Weinheim 1973, pp. 83-98, especially pp. 87-95 " described.

The problem of handling moist gases occurs, for example, in medicine African area, especially when handling moisture-saturated exhaled gases during anesthesia.

DE 37 12 598 A1 (Siemens) also describes an inhalation anesthesia machine a reservoir for an anesthetic like xenon. The expiratory gas (Ausat gas) of the patient after filtering out water vapor and Carbon dioxide is fed to the reservoir directly or via a compressor and from there returned to the patient.

DE 44 11 533 C1 (Georgieff et al.) Describes an anesthetic machine with a back extraction plant for xenon. This is done in the recovery plant breathed breathing gas after pre-cleaning compressed and into a Druckbe introduced container, which is received in a cooling device.  

The systems and procedures mentioned are part of an anesthesia system stems are used for direct return of the xenon to the patient during anesthesia. The systems and processes are very complex in terms of equipment. The usually moist gases must be dried for processing.

In gas technology it has been extremely difficult to use a moist gas with a compress suitable compressor. This is to prevent corrosion Previously, gas was reserved through a suitable, additional drying step delt.

The requirement for today's gas compressors (compressors) tion if these are operated in operating rooms after significantly reduced Noise levels.

The invention has for its object to promote and compression suitable gas pump, especially for quiet operation, ready put.

The object was achieved by a gas pump with the be in claim 1 written characteristics.

By using a water bath in which the complete compressor of the Gas pump is arranged, the crankcase can be heated and on the other hand dissipate the heat of compression. At the same time, the Ge noise levels can be reduced. The gas pump is therefore suitable for use in operating rooms where only low noise levels are allowed (in the Order of magnitude of normal conversation volume).

The gas pump is used to compress a gas mixture containing water vapor used, is prevented by tempering the water bath that Water condenses in the compressor (especially in the compressor room and in the Crankcase). The water bath advantageously has a temperature in the range from 50 to 100 ° C, preferably 70 to 95 ° C and particularly preferably 80 to 95 ° C.  

The gas pump is e.g. B. a hermetically sealed piston pump with double stage piston. The pump is preferably a dry-running piston pump. Thanks to the hermetic construction, the pump enables lossless Compression of gases.

Gas pumps (gas compressors), which work as gas-free as possible, are particularly suitable. Such gas compressors are e.g. B. hermetically gastight piston pumps. It is particularly advantageous to use a dry-running, completely gas-tight piston compressor which is constructed at least in two stages, preferably three-stage or multi-stage. The piston compressor is usually constructed as a crosshead-type compressor ("dry-running") or as a plunger-type compressor. A plunger type compressor is particularly advantageous because there is no oil in the entire system (oil-less compressors). The multi-stage design (e.g. 2, 3, 4, 5, 6, 7, 8, 9 or 10 stages) of a piston compressor, in particular as a plunger-type compressor, is not a problem in contrast to a membrane compressor. The engine is in usually connected via a magnetic coupling to the hermetically sealed compressor housing, whereby extremely high tightness, in particular less than 10 ^-3 mbar II sec., is achieved.

Suction at low pressures and ver up to the high pressure range poetry will be more particularly through the use of a new modified stage (with two double cylinders) dry-running hermetically sealed Piston pump reached. This pump works without gas loss because of the leaks are fed back into the system via the pistons. This is only possible with completely enclosed pumps. By applying heat from outside, in particular by a water bath, water can be prevented from condensed out of the pump. This water bath can also be used for heating dissipation of the compression heat can be used. In addition, this one direction the advantage that the noise level caused by the compressor, can be significantly reduced. That is, this pump is also suitable for the Compression of gases saturated with water vapor. That is, a predrying of the Gases are no longer required. A simple water separator between the 2nd and 3rd stages are sufficient to remove the water. A dryer for that Gas (e.g. cartridge with molecular sieve or other drying agent) can  then omitted.

The gas pump according to the invention is advantageous in a gas collection system used to recover anesthetic gas from anesthetic waste gas.

The invention is explained with reference to the drawing.

Fig. 1 is a diagram showing the structure of a dual-stage piston with a preferred for tempering gas pump,

Fig. 2 shows a schematic of a gas collection device with a temperature-controlled gas pump with two cylinders, each with two levels,

Fig. 3 shows a schematic of a gas collection device with a temperature-controlled gas pump with three cylinders each with two levels,

Fig. 4 shows a diagram of a gas collection device with a temperature-controlled gas pump with two single-stage cylinders.

The cylinder 1 shown in Fig. 1 has two stages of gas compression. The cross section of the cylinder in the area of the first stage is larger than the cross section of the cylinder in the area of the second stage. The cylinder 1 contains a gas inlet opening 2 and a gas outlet opening 3 in the region of the first stage. The cylinder contains a gas inlet opening 4 and a gas outlet opening 5 in the region of the second stage. Gas outlet opening 3 of the first stage and gas inlet opening 4 of the second stage are connected to a gas line 10 (pressure line). Check valves 7 , 8 and 9 are arranged outside the cylinder. The piston 6 has a head part with a larger cross section and a lower part with a smaller cross section, corresponding to the areas for the first and second stage in the cylinder.

In the gas collection device shown in FIG. 2, a pump with two cylinders is used, each with two stages (see FIG. 1). The first cylinder (shown at bottom left) contains the first stage 11 and the second stage 12 , the second cylinder (shown at bottom right) contains the third stage 13 and the fourth stage 14 . Levels 11 , 12 , 13 and 14 are selected so that the maximum adiabatic compression temperatures do not exceed 250 ° C (e.g. level 11 , 1st level, cylinder diameter 4 cm; level 12 , 2nd level, 3, 4 cm (ring piston) (for a "normal" piston this would be 2.1 cm for the 2nd step); step 13 , 3rd step, 1.2 cm; step 14 , 4th step, 1.04 cm (ring piston ) (for a "normal" piston this would be 0.6 cm for the 4th stage) with a stroke of 3.2 cm). The specified diameters for stages 12 and 14 correspond to those of an annular piston, ie the actual diameter for "normal" pistons would be much smaller.

Only by combining the double piston ( Fig. 1) is it possible to build a compressor for small delivery quantities and for high pressure ranges with conventional components.

The gas is compressed at a pressure of 0.5-0.7 bar abs. via compression in stage 1 (stage 11 ) up to a pressure of approx. 1.8-2.8 bar. In the 2nd stage (stage 12 ) a pressure of approx. 6.5-8.0 bar is sealed. In the 3rd stage (stage 13 ) to 28-35 bar and in the 4th stage (stage 14 ) to up to 120 bar.

The pistons of the two cylinders are driven by the drive 16 . In the input of the compressor (before stage 11 ), a buffer tank 15 is net angeord. The buffer tank is usually a container, but can also be a line piece with an enlarged internal cross section. This buffer tank 15 is designed so that its volume corresponds to at least 120 times the line and dead space volume of the compressor after the second stage. This is necessary because when the compression process is stopped, the compression pressure must be released so that the compressor can start again. The buffer takes up the complete amount of gas.

The gas collection device contains a check valve 19 at the gas inlet. A bypass gas line with shut-off valve 20 is advantageously arranged between the buffer tank 15 and after the exit from stage 14 . Gas is compressed by the pump and the gas is pumped via the check valve 21 and three-way valve 22 into the pressure gas container 17 or 18 . The pressure gas containers 17 and 18 are advantageously equipped with pressure measuring devices 23 and 24 .

In the gas collection device shown in Fig. 3, a pump with three cylinders is used. The pressure can be increased to 500 bar by a further, third cylinder with a double stage (stage 25 ). Since the stages for the pressure increase must be made smaller in relation to their compression, the 5th (stage 25 ) and 6th stage (stage 26 ) would now be very small. This can be elegantly avoided with the double piston, in that the 5th stage (stage 25 ) is the same size or between the diameter of the 3rd and 4th stage (stages 13 and 14 ) and the 6 stage (stage 26 ) is larger in diameter than that 4th stage (stage 14 ) is, according to the compression ratio between 4 and 6th stage. That is, the 5th stage is actually a buffer. A pressure control valve 27 is arranged between the 5th and 6th stages. This ensures that the pressure is first released from the 4th stage to the 5th stage and is released by the pressure control valve 27 into the 6th stage (stage 26 ) only when the pressure in the 5th stage (stage 25 ) that corresponds to the 4th stage (level 14 ). Due to the construction of the double piston (see Fig. 1), the compression space can be made very small.

The gas pump itself is constructed as a unit with a canned motor or with a magnetic coupling. This makes the system hermetically sealed to the outside. Leakage losses only enter the crank through the piston surfaces housing on. By connecting the crankcase to the 1st stage who which the leakage losses are fed back into the system. At the Gassam due to the high value of xenon, there is a possibility 100% recovery of xenon from the exhaust gas from the Anesthesia.

With an anesthesia machine, it must always be ensured that the patient ent receives enough oxygen and the ventilation circuit is not sucked empty or exposed to excessive pressure.

This is achieved by a simple principle, which is that before the Suction a fixed throttle in combination with a differential pressure valve is installed. The locally installed extraction systems are common today a suction pressure of 0.2 bar abs. on. That is, the pressure in the ventilation circuit drops run with the suction valve open e.g. B. to 2 mbar above atmospheric pressure and if the differential pressure valve is set to 2 mbar, air flows into the  Suction with on and the ventilation circuit is no longer suctioned. As already mentioned, these systems can be combined by pumps realize me. However, this has the disadvantage that different pumps with a variety of individual parts and controls must be used. In addition, the compression pistons are required in conventional pumps due to the low suction power, very small. This leads to either not enough is sucked in at the required pressures or when in use larger pistons are no longer pumped into the high pressure range.

In the gas collecting device in FIG. 4, a single-stage double cylinder is used as an alternative to the two-stage pelzylinder Dop. The advantage of this variant is that you can use the usual seals available on the market today and only need to make new cylinders and cylinder housings.

The compression takes place here first in an intermediate container 37 with a volume of preferably 10 l. This container is brought to a pressure of 5 to 10 bar, preferably 7 bar. When the container 37 has reached this pressure or when it no longer has to be suctioned off, the input three-way valve 28 is automatically switched over and it becomes the intermediate container 37 into a further intermediate container 38 to a residual pressure within 1 to 30 seconds, preferably 8 seconds from 1 to 6 bar, preferably up to 2 bar, emptied. When the first intermediate container 37 has reached the pressure of 2 bar and the pressure in the second intermediate container 38 has risen to greater than 8.5 bar, the valve for feeding from the first intermediate container is closed and the valve for feeding from the second intermediate container is opened and compressed into the collecting container 17 or 18 . The collection container is available at least twice and is automatically switched when the filling pressure is reached (e.g. from 17 to 18 ). A temperature monitoring ensures that only the critical temperature of xenon is filled to prevent overfilling of the container due to the liquefaction of xenon below the critical temperature and above the critical pressure.

Claims (8)

1. Gas pump with temperature-controlled compressor. 2. Gas pump according to claim 1, characterized by one, two, three or more single-stage or two-stage pistons ( 6 ). 3. Gas pump according to claim 1 or 2, characterized in that the Ver is placed closer to a water bath. 4. Gas collection system for the recovery of anesthetic gas from anesthesia Exhaust gas containing a gas pump according to one of claims 1 to 3 suction of gas and compression at low pressure or high pressure. 5. Gas collection system according to claim 4, characterized in that the gas collection system contains a pressurized gas container ( 17 or 18 ) for gaseous filling with gases containing anesthetic gas. 6. A method for collecting anesthetic gases, characterized in that anesthetic gas-containing exhaust gas from an anesthesia device for recovery with a gas pump according to one of claims 1 to 3, and then compressed without drying and / or analysis of the gas composition at high pressure in a compressed gas container ( 17 or 18 ) is collected in gaseous form until this compressed gas container is filled. 7. The method according to claim 6, characterized in that anesthetic gas containing exhaust gas from an anesthesia machine only for recovery sucks and is collected when the exhaust gas reaches a predetermined min has the residual content of the anesthetic gas. 8. The method according to claim 6 or 7, characterized in that xenon as Anesthetic gas is used.