Patent Publication Number: US-6220578-B1

Title: Liquid-gas jet apparatus with multiple nozzles and variants

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 of PCT/IB98/01690, filed Oct. 22, 1998 with priority of RU 97117774, filed Oct. 29, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention pertains to the field of jet technology, primarily to jet apparatuses intended for producing a vacuum in various units, for example in vacuum rectifying columns. 
     There is a liquid-gas jet apparatus known, which comprises a nozzle for feed of a motive vapor medium, a mixing chamber and a diffuser (see, DE patent 51229, class 59 c, 13,1890). 
     This jet apparatus has a low efficiency factor. Additionally, high energy inputs are required to produce the motive vapor medium. 
     The closest analogue to the jet apparatuses described in the present invention is a multi-nozzle liquid-gas jet apparatus, which has a chamber for feed of a liquid medium with a grillage placed at the chamber&#39;s outlet, active nozzles installed in the slots of the grillage, a receiving chamber, a branch pipe for feed of an evacuated gaseous medium, mixing chambers placed in alignment to each nozzle, and a discharge chamber (see book by Sokolov E. Y. and others “Jet apparatuses”, M., Energy, 1970, page 229). 
     This jet apparatus allows evacuation of large amounts of vapor-gas mediums. However such apparatuses have a rather low efficiency factor because of high energy losses during passing of an evacuated medium to the jets of an active (ejecting) liquid medium. Besides, the absence of means preventing ingress of foreign objects, which affect apparatus performance, into the nozzles of the jet apparatus reduces reliability of this apparatus. 
     SUMMARY OF THE INVENTION 
     The present invention is aimed at an increase in efficiency of the multinozzle jet apparatus by reducing energy losses during feeding of evacuated and active mediums, and at an increase in reliability of the jet apparatus by preventing penetration of objects, which could disturb operation of the apparatus, into the nozzles and by preventing reverse flow from the outlet of the jet apparatus into its receiving chamber. 
     The mentioned problem is solved as follows. A multi-nozzle liquid-gas jet apparatus, which comprises a chamber for feed of a liquid medium, a grillage placed at the outlet of the chamber, active nozzles installed in the slots of the grillage, a branch pipe for feed of an evacuated gaseous medium, mixing chambers placed in alignment to each nozzle, and a discharge chamber, is modified so that each nozzle is furnished with a filter element installed at its inlet side. The filter element constitutes a sleeve with longitudinal apertures in its side wall. The total surface area of the apertures of the filter element exceeds more than twice the surface area of the cross-section of the nozzle&#39;s throat, and the width of each aperture in the filter element is at least two times smaller than the shortest distance between the opposite walls in the cross-section of the nozzle&#39;s throat. 
     There is another variant for implementation of the multi-nozzle liquid-gas jet apparatus comprising a chamber for feed of a liquid medium, a grillage placed at the outlet of the chamber, active nozzles installed in the slots of the grillage, a branch pipe for feed of an evacuated gaseous medium, mixing chambers placed in alignment to each nozzle, and a discharge chamber. In this variant each mixing chamber is furnished with an inlet duct located in the receiving chamber, the height of each inlet duct represents from 0.05 to 86 times its diameter. 
     The executed research showed, that in operation of units which include the multi-nozzle liquid-gas jet apparatus the operation is often unreliable. The conditions decreasing reliability are initiated, when a part of a mixture of active and evacuated mediums flows from the outlet of the apparatus back into the receiving chamber of the apparatus. Sometimes foreign objects, for example caix, get into the nozzles of the jet apparatus as well. And because the nozzle of the jet apparatus is the narrowest flow-through canal of the whole unit the throat of the nozzle is blocked up first. All of these factors adversely affect performance of the jet apparatus. On the other hand, conventional filter elements installed at the liquid inlet of the apparatus create big hydraulic resistance and reduce efficiency of the jet apparatus. Besides, the mechanism for feeding of the liquid medium into the nozzles exerts great influence on the operation of the entire jet apparatus, because an equal pressure at the inlets of all nozzles of the multi-nozzle jet apparatus is required for optimal performance of the jet apparatus. 
     It was discovered, that it is advisable to furnish each nozzle with its own filter element. Such a design of the jet apparatus allows the filters to be made hydraulically “transparent”. This means, that these filters practically do not create a pressure differential when a liquid active medium passes through them. Such became possible due to the special design of the filter element. Each filter element represents a sleeve with longitudinal apertures in its side wall. The total surface area of the apertures in each of the filter elements exceeds more than twice the surface area of the cross-section of the nozzle&#39;s throat, and the width of each aperture of the filter element is at least two times smaller than the shortest distance between the opposite walls in the cross-section of the throat. 
     The location of the apertures on the sleeve is also important. It was discovered, that the availability of the longitudinal apertures helps to equalise pressure at the inlets of liquid active nozzles and consequently provides an almost equal flow rate of a liquid active medium through each nozzle. One resulting effect, is that the jet apparatus operates more effectively. 
     Along with the above mentioned important features of the invention, the organization of the access for the evacuated medium to the jets of the liquid active medium has significant influence on operation of the jet apparatus. 
     When the inlet ducts of the mixing chambers are located in the receiving chamber a distributive space is created in the receiving chamber, so that an easier and more uniform access for the evacuated medium to all jets (peripheral and central) of the active liquid medium is provided. As a result effectiveness of the jet apparatus rises due to an increase in its capacity. This taken in conjunction with a more balanced distribution of the active medium to the nozzle inlets prevents reverse flow of the mixture of mediums into the receiving chamber. Consequently operation of the jet apparatus becomes more reliable because of a nearly uniform pressure field of the active medium at the inlets of all nozzles of the jet apparatus and equal admittance of the evacuated medium to all jets for the active medium provides operation of all mixing chambers in the same mode. Thus an occurrence of a pressure difference between the mixing chambers is prevented. Therefore conditions do not exist for an outbreak of a part of the mixture of the active and evacuated mediums&#39; mixture from the discharge chamber into the receiving chamber. Optimal proportions between the height and the diameter of each inlet duct to the mixing chamber was discovered. It was determined, that when the height of the inlet duct represents from 0.05 to 86 times its diameter, the evacuated medium is received with minimum hydraulic losses. When the proportion is more than 86 performance of the jet apparatus is not improved and further increase of the proportion is useless. 
     So, as it is clear from the aforesaid, the described solutions provide an increase in reliability and effectiveness of the multi-nozzle liquid-gas jet apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawing in FIG. 1 schematically represents a longitudinal section of the described multi-nozzle liquid-gas jet apparatus. 
    
    
     DETAILED DESCRIPTION 
     The multi-nozzle liquid-gas jet apparatus comprises a chamber  1  for feed of a liquid medium, a grillage  2  having slots where the grillage  2  is placed at the outlet of the chamber  1 , liquid active nozzles  3  installed in the slots of the grillage  2 , a receiving chamber  4 , a manifold  5  for feed of an evacuated gaseous medium, mixing chambers  6  placed in alignment with each nozzle  3 , and a discharge chamber  7 . Each nozzle  3  is furnished with a filter element  8  installed at the inlet side of the nozzle  3  and constituting a sleeve  11  having longitudinal apertures  9  in the side wall  12  of the filter element  8 . The total surface area of the apertures  9  in each filter element  8  exceeds more than twice the surface area of the cross-sectional area of the throat of the nozzle  3 , the width (P) of each aperture  9  in the filter element  8  is at least two times smaller than the shortest distance (d) between the opposite walls  13  in the cross-section of the nozzle  3  in the zone of the throat of nozzle  3 . 
     Each mixing chamber  6  is furnished with an inlet duct  10  located in the receiving chamber  4 . The height (L) of each inlet duct  10  represents from 0.05 to 86 times the diameter (D) of the inlet duct  10 . 
     The multi-nozzle liquid-gas jet apparatus operates as follows. 
     An active liquid medium goes into the chamber  1 , where it is distributed between the nozzles  3 . From the chamber  1  the liquid medium goes into the liquid active nozzles  3  through the filter elements  8 . The active medium effusing from the nozzles  3  entrains an evacuated gaseous (vapour-gaseous) medium from the receiving chamber  4  into the mixing chambers  6 . In the mixing chambers  6  the liquid active and evacuated gaseous mediums are mixed. A part of the easy-condensable components of the gaseous medium is often condensed in the liquid active medium during mixing of the mediums. A gasliquid mixture from the mixing chambers  6  flows into the discharge chamber  7 . During evacuation, the gaseous medium gets into the receiving chamber  4  of the jet apparatus through the manifold  5 . In the receiving chamber  4  the gaseous medium is uniformly distributed between the mixing chambers  6  in the space in front of the inlet ducts  10 . If foreign objects, which can block the active nozzles  3 , get into the jet apparatus together with the liquid active medium, such foreign objects are entrapped by the filter elements  8 , are washed off by the flow of the active medium and settle on the grillage  2 . Later on the foreign objects are removed from the jet apparatus during scheduled maintenance. 
     INDUSTRIAL APPLICABILITY 
     Present invention can be applied in chemical, petrochemical and some other industries.