Abstract:
Process and apparatus for degassing liquids, namely water, with mobile and stationary application, according to the principle of underpressure generation by suctioning a portion of the liquid from the chamber, which, after the degassing, is filled automatically again with gas-containing liquid, whereupon the next degassing cycle occurs.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a process for degassing liquids in closed systems by applying a pressure which is lower compared to the system pressure. 
     PRIOR ART 
     In removing gases from liquids, primarily from water, one generally differentiates between 
     1. removing (venting) excess gases which exceed the specific solution equilibrium, 
     2. driving out (degassing) chemically dissolved gases. 
     1.) Gases comprised in excess in water generally present considerable problems in circulating systems (heating systems, cooling systems, air-conditioning systems). As extremely fine air bubbles, they generate flow noises, cavitation and erosion in the materials and degrade the uniform heat transport in the pipe network and on the surfaces provided for the heat exchange, such as coolers and heating surfaces. 
     To avoid these problems, ventilation equipment is produced which operates generally with a stop valve disposed in a chamber and connected with a float. When the chamber is filled, the rising float closes the valve. Conversely, the float opens the valve when air enters the chamber. Such ventilation devices are frequently air collection pots, cyclone pots or vessels with massive bodies which are intended for the extremely fine air bubbles to combine into larger ones in order to rise subsequently in the chamber of the ventilator. 
     2.) If greater gas volumes are comprised in the water than are necessary for chemical saturation, this quantity represents a feeding reservoir to reestablish the natural saturation concentration which is lost, for example, through the reaction of a gas with the materials in the solution. In order to drive out the excess gas and also the gases comprised in the solution, thermal degassing equipment is being manufactured in which, on the one hand, by increasing the temperature, the gas solubility is reduced and, on the other hand, the expulsion effect is enhanced thereby that steam is forced through the water to be degassed and the resulting steam bubbles entrain the gas particles in the water and carry them outside to the outside atmosphere. 
     Other devices generate a reduced pressure above the level of the liquid whereupon the gases also escape to the surface. 
     DISADVANTAGES OF PRIOR ART 
     Regarding 1.) 
     According to Henry&#39;s law, ventilation devices can only remove those quantities of gas which are greater than the factors temperature, pressure and medium properties permit in terms of solubility. In principle, in a circulating system two different pressure regions always obtain between intake and pressure region of a circulation pump such that in theory a ventilator disposed on the intake side of a pump should transport gas out of the system. But in practice, narrow limits are set because the ventilator must be under minimum pressure so that its float chamber remains filled. Otherwise the float drops and opens the ventilation valve such that air can be drawn in via the ventilator (the ventilator becomes an aerator). 
     But if a minimum pressure is required on the low-pressure side, the air can only be incompletely removed. A further disadvantage of this type of ventilation is that, due to the high flow rate of the water, the microbubbles can only reach the float chamber of the ventilator in small quantities if at all. 
     Regarding 2.) 
     According to Henry&#39;s gas law, as expanded by Dalton, the partial pressure acting upon a solution, the temperature and the type of medium determine the solubility of gases. With the known technique of thermal degassing, extremely good results can be attained in this regard. A marked disadvantage of this technique, however, is that it requires large and expensive equipment: a steam generator for producing the expulsion steam and a collecting vessel with degasser device comprising large distributor surfaces on which the water can be exposed to the steam. Part of this equipment includes extensive tubing, regulating elements, control means and the safety technique of steam operation. Such thermal degasser installations are a fixed standard component in steam generation installations. 
     In closed cooling water circuits, heating or cooling water circulations, they are neither economically nor practically applicable since the degassed water would have to be heated and subsequently cooled again to the circulation temperature. 
     The problem is similar in so-called fast steam generators in which a relatively small system water quantity is present and for which a thermal degassing installation would be too large. 
     SUMMARY OF THE INVENTION 
     Required is a cost-effective apparatus for mobile and stationary application, with which excess gas, as well as also the chemically dissolved gases, can be removed from a liquid (for example water). It should not be necessary to raise the temperature of the liquid to be degassed and the apparatus should be operable in a simple manner and require low energy for its operation. 
     Solution 
     The task is solved according to the invention thereby that from a water system a portion of the water is extracted and transferred to the degassing container of the described apparatus. By extracting a portion of the liquid and transporting it to a storage container the total pressure (and thus the partial pressures on all gases) is lowered in the degassing container so far that the boiling point of the liquid is exceeded and the liquid boils. The solution equilibrium of the dissolved gases shifts toward the left and as a consequence all excess gases are driven out with the steam bubbles. The temperature of the liquid is not raised. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention and other objects relating thereto, reference will be made to the following detailed description of the invention which is to be read in association with the accompanying drawings wherein: 
     FIG. 1 is a schematic representation of the degassing apparatus of the present invention; 
     FIG. 1 a  illustrates the flow path of fluids in the apparatus shown in FIG. 1 when the apparatus is in a circulation mode; 
     FIG. 1 b  illustrates the flow path of fluid when the apparatus is in an evacuation mode; and 
     FIG. 2 illustrates a further embodiment of the invention. 
    
    
     DESCRIPTION OF THE INVENTION 
     The invention relates to a process for degassing liquids under low pressure with the associated equipment either connected in parallel with the circulation system or, in batch operation, from a first container with gas-containing liquid a specific quantity is extracted, degassed and transferred to a second closed container. 
     FIG. 1 shows such a degassing apparatus. By means of a pump ( 3 ) from a circulation ( 1 ) via a line segment ( 2 ) liquid is removed, pumped via a jet pump ( 4 ) and an automatic valve ( 5 ) through a container ( 6 ) and from there is transferred via a jet pump ( 7 ) and line segments ( 14 ), ( 8 ) and the automatic valve ( 23 ) back into the circulation ( 1 ). The automatic valves ( 11 ) and ( 12 ) are closed. A circulation is generated in the course of which through the container ( 6 ) gas-containing circulating water is flushed. The jet pump ( 4 ) empties the diaphragm pressure storage ( 21 ) completely and recycles the liquid stored there back into the circulating cycle. The circulation time can be set to be of any desired length via a timer clock ( 9 ). 
     At the end of the circulation time the timer clock ( 10 ) starts the evacuation time. Automatic valves ( 11 ) and ( 12 ) are opened and automatic valves ( 5 ), ( 23 ) are closed. The liquid is now pumped in a cycle by pump ( 3 ) via the line segment ( 13 ) through the automatic valve ( 11 ) and through the jet pump ( 7 ), further via line segments ( 14 ) and ( 15 ) through the automatic valve ( 12 ). In the jet pump ( 7 ) a strong current is generated such that on the intake side of the jet pump ( 7 ) a very strong underpressure is generated. In this way the liquid is drawn from the container ( 6 ) and forced with the circulation flow via line segments ( 14 ), ( 15 ), ( 13 ) into the partial line segment ( 16 ) and subsequently through the jet pump ( 4 ) into the diaphragm storage ( 21 ). The size of the diaphragm storage ( 21 ) and its gas supply pressure are calculated and determined according to the liquid quantity equal to the evacuation quantity to be displaced. Depending on the setting of the underpressure and the liquid temperature, the liquid starts to boil spontaneously in container ( 6 ). The driven-out gases rise into the upper pipe outlet ( 17 ) of container ( 6 ) and further into the float chamber of the ventilator ( 18 ). At this point in time they are not yet capable of escaping into the atmosphere via the check valve ( 19 ) since in the container ( 6 ) underpressure still obtains. After the expiration of the evacuation time set on the timer clock ( 10 ), the circulation time starts again on the timer clock ( 9 ). The functions performed during the circulation time have already been described above. During the circulation the container ( 6 ) is again filled completely and the system pressure is exerted onto it. All steam bubbles condense and the gases driven out collect in the pipe outlet ( 17 ) as well as in the ventilator ( 18 ). The liquid level rises into the ventilator ( 18 ) and forces the gases through the ventilator ( 18 ) and the check valve ( 19 ) to the outside. A manometer ( 20 ) has two functions. It indicates the excess pressure as well as also the underpressure during the operating cycles ‘circulation’ and ‘evacuation’. 
     FIG. 1 a  shows the flow paths in the degassing apparatus in the switched state ‘circulation’, i.e. charging the apparatus with gas-containing circulating water. During the circulation the check valve ( 22 ) prevents a shortcircuit between the water inlet and the water outlet of the main circulation. 
     FIG. 1 b  depicts the flow paths in the degassing apparatus in the switched state ‘evacuation’, i.e. of the degassing of the liquid present in container ( 6 ). 
     FIG. 2 shows an apparatus functionally identical with FIGS. 1,  1   a  and  1   b,  however, additionally equipped with a device for collecting and recycling of condensate, as well as with an additional device for replenishing the volume loss, generated during the degassing, with an equal quantity of water. 
     DESCRIPTION 
     Basic settings of the valves with the installation switched off before starting operation: 
     Manual valves  81 ,  82 ,  84 ,  86  are open. 
     Manual valves  79 ,  80 ,  83 ,  85 ,  87 ,  88  are closed. 
     Automatic valves  60 ,  61 ,  62 ,  63 ,  64 ,  65 ,  66 ,  67  are closed 
     Preparing installation for operation: 
     The installation is filled via the replenishment line segment  54 . For this purpose a switch  95  is set to “off”, and switches  94  and  96  are switched to “on”. If switch  96  is switched to “on”, the automatic valve  66  opens and the replenishment water can flow into the installation to the extent the pressure reducer valve  90  is opened. 
     The installation is now filled via the replenishment line segment  54 . The air escapes via the exhaust line segment  55 . The filling process is completed when no air escapes via the pipe line segment and the manometers  104 ,  106 ,  105  and  107  indicate identical pressure. 
     During the filling process the pressure reducer valve  90  is preset toward the end of the fill time to the system pressure obtaining at the inlet point  30 . Subsequently the manual valves  79  and  80  are opened. Thereby within the degasser installation and the water system to be degassed an identical pressure develops. 
     By adjusting the restoring pressure on the pressure reducer valve  90  the final system pressure can be corrected during the degassing. 
     The supply pressures of the diaphragm expansion vessels (MAG)  112  and  113  are set with the installation switched on (main switch  94  to “on”) and the pump switched on (switch  95  to “on”) on the manometer  107  are set to the pressure obtaining during the time of the transfer by pumping (timer  68 ). 
     To set the supply pressure in the MAGs, the manual valves  86  and  84  are closed, subsequently the manual valves  85  and  87  are opened until the MAGs are empty of water. Subsequently the valves are closed again and the gas supply pressure is set in the MAGs by means of nitrogen gas to the previously read-off display of the manometer  107 . The installation is now ready to start and the vacuum degassing can start: 
     Timertime 1 =Timer  68 : transfer by pumping, exchange of water content. 
     Switch  95  switches on pump  40 . Subsequently the program flow is reset by briefly switching on/off the switch  94 . 
     A pump  40  draws water from a water system via the junction point  30  and the pipe line segment  48 , passing through a dirt trap  31  and a check valve  32 , transports it via the pipe line segment  49  into the vacuum vessel or closed container  34  further via the pipe line segment  50  and the junction point  38  back into the water system. The automatic valves  60 ,  61 ,  62 ,  65 ,  66  are opened for this purpose;  63 ,  64 ,  67  remain closed. During the transfer process by pumping, through the jet pump  42  via the pipe line segment  53  the MAG  112  is emptied completely by suction provided it was not completely emptied during the preceding operating step (see below). The pressure on the manometer  102  falls to the supply pressure set in the MAG. In this way it is possible to check whether or not the supply pressure of the MAG  122  is still correct. The time of the transfer by pumping is determined by setting the timer  68  in the control switchboard  76 . The transfer quantity is counted by the contact water meter  33 . It transmits  11  pulses which are indicated on the control switchboard  76  through light  72 . In this way it is possible to determine via the time setting on timer  68  the transfer quantity (exchange quantity). 
     Timertime 2 =timer  69 : suctioning vacuum 
     At the completion of time  68  the switch positions of the automatic valves change: 
     Valves  60 ,  63 ,  64  are open. 
     Valves  61 ,  62 ,  65 ,  66 ,  67  are closed. 
     Valve  67  can open. Explanations in this regard are explained below. 
     A fast internal circulation develops in the pipe line segment  51  with the direction pump  40 &gt;automatic valve  63 , jet pump  41 &gt;automatic valve  64  such that on the intake side of the jet pump and the pipe line segment  58  a strong underpressure is generated and water is suctioned out of the vacuum vessel. Thereby at the output of pump  40  a high pressure is generated through which the suctioned water is forced into the MAG  112  through line segment  49 , the jet pump  42  (now without effect) and the line segment  53 . The display on manometer  102  rises. 
     Via pipe line segment  52  it is ensured that after the automatic valve  65  a very low pressure obtains such that the valve always closes optimally and, in the presence of a vacuum, no water can flow via the pipe line segment  48  into the installation. With a vacuum present, the exhaust line segment  55  is closed via the check valve  44 , the condensate line segment  56  via the automatic valve  67  and the outlet line segment via the check valve  35 . 
     The display on the manometer  107  falls to underpressure. Analogously, the display on the manometer  102  rises. An upper pressure limitation is set on the pressure regulator  97  such that upon reaching an undesirably high pressure the installation switches off automatically and the alarm light  75  lights up. The process of vacuum suction can be observed via the inspection pipe  36 , if the manual valves  81  and  82  are open. 
     If the condensate collection vessel  46  is filled at the beginning of the vacuum suction, i.e. the magnet float  100  of the probe rod  101  is at the upper reed switch  98 , the automatic valve  67  opens and the condensate is suctioned back into the installation until the magnet float has reached the lower reed switch  99 . During times  68  (transfer by pumping) and  71  (pressure equilibration) the valve  67  cannot open. A residual quantity of condensate remaining after the passage of time  70  (maintaining vacuum) must, if necessary, wait for the next cycle to be suctioned back. 
     Timertime 3 =Timer  70 : maintaining vacuum 
     After completion of time  69 , the automatic valve  60  is closed. The valve settings at this time are: 
     Valves  63 ,  64  are open. 
     Valves  60 ,  61 ,  62 ,  65 ,  66 ,  67  are closed. 
     Valve  67  can open if the condensate vessel  46  is full (see above). 
     The internal circulation in the pipe line segment  51  remains extant but no more water is suctioned from the vacuum vessel  34  so that a resting time occurs in which all gas and steam bubbles can rise into the upper region of the vacuum vessel  34  and into the air collection chamber  43 . The rise can be observed on the inspection pipe and it is possible to determine in this way the length of the time  70  which must be set. During this time the internal pressure falls as a function of the water temperature and can be read off on the manometer  107 . 
     Timertime 4 =Timer  71 : internal pressure equilibration 
     At the expiration of time  70  the automatic valve  61  is opened. The valve settings are at this time: 
     Valves  61 ,  63 ,  64  are open. 
     Valves  60 ,  62 ,  65 ,  66 ,  67  are closed. 
     The internal circulation in pipe line segment  51  remains extant. Simultaneously, the water stored in MAG  112  flows via the pipe line segments  53  and  59  into the vacuum vessel  34  such that within the closed installation the pressures can become equilibrated as much as possible. 
     The cycle starts anew. 
     Timertime 1 =Timer  68 : transferring by pumping, exchanging water content. 
     The functions performed in this time have already been described above. 
     After the installation has completed the times  69 =vacuum suctioning,  70 =maintaining vacuum,  71 =internal pressure equilibration and the transfer time  68  has started anew, through the changed valve position (see above) the vacuum is spontaneously broken so that water vapor formed also spontaneously condenses with the consequence that with valve  66  open in the replenishment line segment  54  the volume deficit generated through the degassing is replaced by replenishment water until the system pressure has reached the pressure set on the pressure reducer valve. Simultaneously, the driven-out gas and a residue of non-condensed water vapor escapes (at last under system pressure) via the exhaust line segment  55  into the condensate collection vessel  46 . There line  55  is introduced so deeply that its end is below the residual water level with the result that exiting water vapor can better condense there. 
     Different apparatus embodiments of the process are possible. For example, the liquid extraction for the purpose of evacuation can take place directly by means of a suction pump or with the aid of a piston moving in the downward direction in a cylinder. The principle of the process is the same, which is the reason for omitting a graphic representation of it at this point. 
     Attainable Advantages 
     With the apparatus according to the invention degassing capacities can be achieved which come close to the effect of a thermal degasser. If the issue is driving out oxygen for the purpose of corrosion prevention, the remaining residual quantity of oxygen can usually be tolerated. For the residual corrosion avoidance in special cases either an oxygen-binding chemical product can be added or a corrosion preventive agent which tolerates the presence of oxygen. Since chemical oxygen binders, such as for example sodium sulfite NaSO 3 , such as are conventionally used for corrosion protection, simultaneously place loading on the system with additional salts, the dangerous oversalting of circulations with, for example, sodium sulfate NaSO 4  occurs. The same applies to fast steam generators in which significant quantities of sodium sulfite are used for the purpose of oxygen binding. 
     By driving out oxygen, considerable quantities of water chemicals can be saved in such water, which free the waste water of the loading. 
     Applications 
     Initialization and redevelopment heating systems, cooling water and air-conditioning circulations, degassing of feed water in steam generators, in particular fast steam generators, for stand-down time conservation of steam boilers, degassing of fire protection pipe systems (sprinkler installations) and other applications. 
     LIST OF REFERENCE NUMBERS ON FIG.  2   
       30  inlet 
       31  dirt trap 
       32  check valve line segment  48   
       33  contact water counter 
       34  vacuum vessel 
       35  check valve line segment  50   
       36  inspection pipe 
     
       37 
       37 
     
       38  outlet 
     
       39 
       39 
     
       40  pump 
       41  vacuum pump  1   
       42  vacuum pump  2   
       43  air collection chamber 
       44  check valve line segment  56  exhaust 
       45  exhaust valve actuated via float 
       46  condensate collection vessel 
       47  check valve line segment  58  suctioning back condensate 
       48  pipe line segment system water suctioning 
       49  pipe line segment  1  forcing water into the installation 
       50  pipe line segment water outlet 
       51  pipe line segment internal circulation 
       52  pipe line segment vacuum augmentation 
       53  pipe line segment MAG 1  charging-emptying 
       54  pipe line segment replenishment fresh water 
       55  pipe line segment ventilating 
       56  pipe line segment suctioning back condensate 
       57  pipe line segment manual filling condensate vessel 
       58  pipe line segment vacuum suctioning 
       59  pipe line segment  2  forcing water into the installation 
       60  MV pump at pressure side 
       61  MV vacuum vessel input 
       62  MV vacuum vessel+system output 
       63  MV jet pump input 
       64  MV jet pump output 
       65  MV system+pump input 
       66  MV fresh water replenishment 
       67  MV condensate recycling 
       68  timer transferring by pumping, filling 
       69  timer suctioning vacuum 
       70  timer maintaining vacuum 
       71  timer pressure equilibration 
       72  light circulation 
       73  light pump 
       74  light replenishment 
       75  light excess pressure 
       76  control switchboard 
     
       77 
       77 
     
     
       78 
       78 
     
       79  HV system input 
       80  HV system output 
       81  FV inspection pipe top 
       82  HV inspection pipe bottom 
       83  HV installation emptying 
       84  HV MAG 1  inflow+outflow 
       85  HV MAG  1  emptying 
       86  HV replenishment fresh water 
       87  HV MAG 2  emptying 
       88  HV filling condensate vessel manually 
     
       89 
       89 
     
       90  pressure reducer 
       91  check valve 
     
       92 
       92 
     
     
       93 
       93 
     
       94  switch main 
       95  switch pump on/off 
       96  switch replenishment water automatic/manual 
       97  switch, off, excess pressure 
       98  reed switch vessel full 
       99  reed switch vessel empty 
       100  float with magnet 
       101  probe rod with  2  reed switches 
       102  manometer MAG 1  actual pressure 
       103  manometer MAG 2  actual pressure 
       104  manometer degasser input 
       105  manometer degasser output 
       106  manometer fresh water after pressure reducer 
       107  manometer vacuum vessel+pressure 
     
       108 
       108 
     
     
       109 
       109 
     
     
       110 
       110 
     
     
       111 
       111 
     
       112  MAG 1  water take-up+release 
       113  MAG 2  replenishment after vacuum 
     
       114 
       114 
     
     
       115 
       115