Abstract:
A maple sap reverse osmosis system that comprises a feed pressure pump configured for receiving maple tree sap, a filter bank, at least one pressure pump operatively connected to the feed pressure pump through the filter bank, at least one recirculation pump operatively connected to the at least one pressure pump, each recirculation pump having an associated housing having an input positioned at a bottom portion of the housing, a permeate output and a concentrate output, the housing enclosing a membrane producing permeate and concentrate from the maple sap and an air inlet operatively connected to a housing in a exit position. The housings are serially connected from an entrance position housing to the exit position housing through associated inputs and concentrate outputs and wherein the housings can be completely drained of liquid through the input of the entrance position housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefits of U.S. provisional patent application No. 61/282,629 filed on Mar. 9, 2010, which is herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a reverse osmosis system for maple tree sap. 
     BACKGROUND 
     Collecting the sap of maple trees to make maple syrup and other derivative products has been known for centuries by North-American Indians and more recently, it has been eagerly taken over by the colonists and is now a thriving industry in the North East United States and south east of Canada. Like most industry, it has to modernize in order to remain profitable and a number of inventions have automated the process. 
     That is why, over the years, various systems have been used to improve the production of maple syrup. The most expensive and time consuming part of the process of making maple syrup has to do with the boiling of the sap so as to create the sugary concentrate—the maple syrup. 
     It has been found that by using reverse osmosis, a more concentrated sap can be produced, which requires less boiling time, thus a saving in energy cost. Reverse osmosis for the purpose of filtering water has been known for decades and by discarding the pure water and keeping the concentrate, an improved process for making maple syrup was born. 
     However, because of their configuration, common reverse osmosis systems take a fair amount of time to drain, are subject to loss of sap during cleanup, are subject to frost because of the difficulty in completely draining the system of liquid and require great quantities of water to properly wash. 
     Furthermore, common reverse osmosis systems are also subject to downtime caused by the repair, maintenance and replacement of filter banks. 
     Accordingly, there is a need for a reverse osmosis system that addresses the above-mentioned problems. 
     SUMMARY 
     The present disclosure relates to a maple sap reverse osmosis system comprising:
         a feed pressure pump configured for receiving maple tree sap;   a filter bank;   at least one pressure pump operatively connected to the feed pressure pump through the filter bank;   at least one recirculation pump operatively connected to the at least one pressure pump, each recirculation pump having an associated housing having an input positioned at a bottom portion of the housing, a permeate output and a concentrate output, the housing enclosing a membrane producing permeate and concentrate from the maple sap; and   an air inlet operatively connected to a housing in a exit position;
 
wherein the housings are serially connected from an entrance position housing to the exit position housing through associated inputs and concentrate outputs and wherein the housings can be completely drained of liquid through the input of the entrance position housing.
       

     The present disclosure also relates to a maple sap reverse osmosis system comprising:
         a feed pressure pump configured for receiving maple tree sap;   a filter bank;   at least one pressure pump operatively connected to the feed pressure pump through the filter bank;   at least one recirculation pump operatively connected to the at least one pressure pump, each recirculation pump having an associated housing having an input, a permeate output and a concentrate output positioned at a bottom portion of the housing, the housing enclosing a membrane producing permeate and concentrate from the maple sap; and   an air inlet operatively connected to a housing in an entrance position;
 
wherein the housings are serially connected from the entrance position housing to an exit position housing through associated inputs and concentrate outputs and wherein the housings can be completely drained of liquid through the concentrate output of the exit position housing.
       

     The present disclosure further relates to a maple sap reverse osmosis system comprising:
         a feed pressure pump configured for receiving maple tree sap;   a plurality of filter banks;   a set of path selectors being configured to provide maple tree sap to selected filter banks;   at least one pressure pump operatively connected to the feed pressure pump through the filter banks;   at least one recirculation pump operatively connected to the at least one pressure pump, each recirculation pump having an associated housing having an input, a permeate output and a concentrate output, the housing enclosing a membrane producing permeate and concentrate from the maple sap; and   an air inlet operatively connected to a housing in an entrance position;
 
wherein the housings are serially connected from the entrance position housing to an exit position housing through associated inputs and concentrate outputs.
       

    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Embodiments of the disclosure will be described by way of example only with reference to the accompanying drawing, in which: 
         FIG. 1  is a schematic representation of the maple sap reverse osmosis system in accordance with a first illustrative embodiment of the present disclosure; 
         FIG. 2  is a schematic representation of the maple sap reverse osmosis system in accordance with a second illustrative embodiment of the present disclosure; 
         FIG. 3  is a schematic representation of the maple sap reverse osmosis system in accordance with a third illustrative embodiment of the present disclosure; 
         FIG. 4  is detailed view of a first example of a membrane sub-system in accordance with an illustrative embodiment of the present disclosure; 
         FIG. 5  is detailed view of a second example of a membrane sub-system in accordance with an illustrative embodiment of the present disclosure; 
         FIG. 6  is detailed view of a third example of a membrane sub-system in accordance with an illustrative embodiment of the present disclosure; 
         FIG. 7  is detailed view of a fourth example of a membrane sub-system in accordance with an illustrative embodiment of the present disclosure; 
         FIG. 8  is a schematic representation of the maple sap reverse osmosis system of  FIG. 2  further showing the storage sub-system; and 
         FIG. 9  is a schematic representation of the maple sap reverse osmosis system of  FIG. 1  or  3  further showing the storage sub-system. 
     
    
    
     DETAILED DESCRIPTION 
     Generally stated, the non-limitative illustrative embodiment of the present disclosure provides a reverse osmosis system for maple tree sap with improved concentrate recuperation and draining of washing soap and permeate. In a further illustrative embodiment, the reverse osmosis system for maple tree sap is provided with redundant feed pumps and filter banks. 
     Although reference is made throughout the present disclosure to a reverse osmosis system using osmosis membranes, it is to be understood that the description equally applies to similar technologies such as, for example, nano-filtration membranes. 
     Referring to  FIG. 1 , there is shown a maple sap reverse osmosis system  100  in accordance with a first illustrative embodiment of the present disclosure. The reverse osmosis system  100  is generally composed of a pumping sub-system  110 , a membrane sub-system  120  and a washing sub-system  130 . A drain valve V 11  allows the redirection of various liquids at the entry of the reverse osmosis system  100  to the drain. 
     The pumping sub-system  110  includes a feed pump  112 , receiving maple sap from valve v 9 , permeate from valve v 10  or washing fluid from valve v 8 , and a set of pressure pumps  114 . Between the feed pump  112  and pressure pumps  114  are located two banks of filters  116   a  and  116   b  comprising three filters each, for example 5 micron filters. 
     In operation, a single filter bank  116   a  or  116   b  is used, for example filter bank  116   a , while the other filter bank, i.e. filter bank  116   b , is on standby in case of a failure or for maintenance to one or more filter of first filter bank  116   a.    
     The selection of which filter bank  116   a  or  116   b  is in use may be done manually or the pumping sub-system  110  may further include controllers, actuators and sensors so as to detect failures in one or more filter and provide automatic switching between the filter banks  116   a  and  116   b  by selectively activating valves V 13   a  and V 13   b . This redundancy of the filter banks  116   a ,  116   b  limits costly system downtime, for example normal clogging of the filters alone may require maintenance three to four times a day. Furthermore, an alarm or display may inform an operator previous to a complete stop (for example by detecting a psi variation) that one or more filter of a filter bank requires repairs, maintenance or replacement due to, for example, clogging of the filters. This feature is quite useful as it allows an operator to change a filter bank without having to stop the entire system  100  which may require the shutting down of as many as 15 different motors which then have to be restarted again after the filter bank is replaced. 
     It is to be understood that the number of filter banks, as well as the number of filters per bank, may vary. 
     The membrane sub-system  120  includes a set of housings  125 , each having therein an osmosis membrane, with associated recirculation pumps  124  and a check-valve air inlet  152 . The housings  125  and their interconnections will be further detailed below. 
     It is to be understood that the number of housings  125  and recirculation pumps  124  may vary. 
     The washing sub-system  130  includes a washing tank  132 , a set of redirection valves V 4 , V 5 , V 6 , V 7  and V 8 , and a drainage valve V 12 . The redirection valves V 4 , V 5 , V 6  and V 7  allow the redirection of concentrate  104  and permeate  106  from the membrane sub-system  120  to respective holding tanks (not shown), the redirection of permeate  106  from the permeate holding tank into the washing tank  132  to be mixed with a cleaning agent to form a washing solution and the redirection of the washing solution, through valve V 8 , into the internal components of the membrane sub-system  120 . 
     Although not shown, it is to be understood that the reverse osmosis system  100  also includes all the electronics and electrical components necessary for its operation. Also, flow meter gauges providing visual indications of the permeate and concentrate may also be included. 
     Referring to  FIG. 2 , there is shown a maple sap reverse osmosis system  100 ′ in accordance with a second illustrative embodiment of the present disclosure. The reverse osmosis system  100 ′ is generally composed of a pumping sub-system  110 ′, a membrane sub-system  120 ′ and a washing sub-system  130 . 
     In this illustrative embodiment, the pumping sub-system  110 ′ includes two sets of feed pumps and filter banks, a first set comprising feed pump  112 ′ a  and filter bank  116 ′ a , and a second set comprising feed pump  112 ′ b  and filter bank  116 ′ b . The filter banks  116 ′ a  and  116 ′ b  comprise four filters each, for example 5 micron filters. 
     In operation a single set of feed pumps and filters is used, for example feed pump  112 ′ a  and filter bank  116 ′ a , while the other set, feed pump  112 ′ b  and filter bank  116 ′ b , is on standby in case of a failure or for maintenance to one or more components of the first set, i.e. feed pump and/or filter. 
     Again, the selection of which set of feed pump and filters may be done manually or the pumping sub-system  110 ′ may also include controllers, actuators and sensors so as to detect failures in one or more component of a feed pump and filter bank set and provide automatic switching to between sets by selectively activating valves V 13   a  and V 13   b . This redundancy of the feed pumps  112 ′ a ,  112 ′ b  and filter banks  116 ′ a ,  116 ′ b  limits costly system downtime. Furthermore, an alarm or display may inform an operator before a complete halt of the system  100  that one or more feed pump and/or filter of a filter bank requires repairs, maintenance or replacement due to, for example, clogging of the filters. 
     It is to be understood that the number of sets of feed pumps and filter banks, as well as the number of feed pumps and filters per set, may vary. 
     The membrane sub-system  120 ′ includes a set of housings  125 , each having therein an osmosis membrane, with associated recirculation pumps  124 , and a pressure regulator  126  with associated compressed air inlet  138 . The housings  125  and their interconnections will be further detailed below. 
     It is to be understood that the number of housings  125  and recirculation pumps  124  may vary. 
     In this embodiment, the washing sub-system  130  is as described in  FIG. 1 . 
     It is to be understood that the pumping, membrane and washing sub-systems may be combined in various configurations. For instance,  FIG. 3  shows a maple sap reverse osmosis system  100 ″ in accordance with a third illustrative embodiment of the present disclosure in which the pumping sub-system  110 ′ of  FIG. 2  is combined with the membrane  120  and washing  130  sub-systems of  FIG. 1 . In a further alternative embodiment (not shown), a maple sap reverse osmosis system may combine the membrane sub-system  120 ′ of  FIG. 2  with the pumping  110  and washing  130  sub-systems of  FIG. 1 . 
     It is also to be understood that the other alternative embodiments may include one of the described sub-systems with commonly used sub-systems. 
     Referring now to  FIG. 4 , there is shown a first detailed example of a membrane sub-system  120 ′ in accordance with the general configuration of the membrane sub-system  120 ′ of  FIG. 2 . In this example, the membrane sub-system  120 ′ is provided with a set of four housings  125  with associated recirculation pumps  124 . Each housing  125  includes therein an osmosis membrane  122 , for example with a capacity of 600 GPH at 500 psi. 
     The pumping sub-system  110  provides maple sap to the membrane sub-system  120 ′ through conduit  108  which is connected to the input  128  of the bottommost housing  125  at position BA. The intermediary housings  125 , at positions IA, are interconnected by their respective outputs  129  and inputs  128 . The output  129  of the topmost housing  125 , at position TA, provides the concentrate  104 . 
     It should be noted that the input  128  of each housing  125  is placed at the bottom, which facilitates the draining of the housing  125 . However, the draining valve  137  being located at the lowest point of the system  100 ′, a few inches from the ground, and the concentrate holding tank being usually elevated with respect to the draining valve  137 , complicate the task of recuperating expensive concentrate still in the various housings  125 . Accordingly, the draining may be accomplished by injecting compressed air through the compressed air inlet  138  of the topmost housing  125  (position TA), the remaining maple sap being forced by the compressed air and gravity in a reverse path through the housings  125  outputs  129  and inputs  128  to be recuperated and redirected to the concentrate holding tank using valve  136 . The compressed air inlet  138  may be provided with a pressure regulator  126  to control the air pressure into the housings  125 . 
     Referring to  FIG. 5 , there is shown a second detailed example of a membrane sub-system  120 ′ in accordance with the general configuration of the membrane sub-system  120 ′ of  FIG. 2 . In this example, the positioning of the housings  125  inputs  128  and outputs  129  have been inversed, i.e. the input  128  is located on a top portion of the housing  125  while the output  129  is located on a bottom portion of the housing. This allows the use of valves V 1  combined with valve V 7  to recuperate concentrate in the concentrate holding tank or with valve V 6  to redirect liquids to the washing tank for draining (see also  FIG. 2 ). 
     Referring to  FIG. 6 , there is shown a third detailed example of a membrane sub-system  120 ′ in accordance with the general configuration of the membrane sub-system  120 ′ of  FIG. 2 . In this example, the configuration of the membrane sub-system  120 ′ is similar to that of membrane sub-system  120 ′ of  FIG. 4  scaled to include eight housings  125  with associated recirculation pumps  124 . It is to be understood that the number of housings  125  and associated recirculation pumps  124  may vary as required. Furthermore, because the membrane sub-system  120 ′ uses compressed air or vacuum, the various housings need not be stacked and may be disposed in side by side banks, e.g. two banks of four in the illustrated example, by connecting the output  129  of each topmost housing  125  to the input  128  of the bottommost housing  125  of the next bank. 
     Referring now to  FIG. 7 , there is shown a fourth detailed example of a membrane sub-system  120 ′ in accordance with the general configuration of the membrane sub-system  120 ′ of  FIG. 2 . In this example, the configuration of the membrane sub-system  120 ′ includes a generally vertical housing  125  with its input  128  placed at a bottom end and the other components placed similarly as with the previously described membrane sub-system  120 ′ (see  FIG. 4 ). It is to be understood, however, that the membrane sub-system  120 ′ may comprise a plurality of generally vertical housings  125 . 
     It should be noted that in the above configurations, an oil-less air compressor should be used with compressed air inlet  138  in order not to contaminate the osmosis membranes  122  within the housings  125 . Alternatively, an air filter eliminating any traces of oil vapor may be used with an oil based compressor. 
     It is to be understood that although the above alternative configurations have been described with reference to membrane sub-system  120 ′, these also apply to membrane sub-system  120  using a vacuum system instead of compressed air. 
     With regard to the configuration of the membrane sub-system  120  of  FIGS. 1 and 3 , the draining may be accomplished by connecting a vacuum system commonly used by maple grove operators to collect sap from maple trees to conduit  108 . In this configuration, a vacuum regulator  150  is used to protect the osmosis membranes  122  which, typically, required the pressure to remain below 5 psi. Alternatively, a water pump connected to conduit  108  may be used to extract the concentrate still in the housings  125  and to redirect it at the output of the pump to the concentrate holding tank  144 . 
     Referring now to  FIG. 8 , there is shown the connections between the washing sub-unit  130  and the membrane sub-system  120 ′ of  FIG. 2  to a tank sub-system  140  comprising a concentrate holding tank  144 , a maple sap holding tank  142  and a permeate holding tank  146 . It should be noted that the pumping sub-system is not shown in this figure. 
       FIG. 9  shows the connections between the washing sub-unit  130  and the membrane sub-system  120  of  FIGS. 1 and 3  to a tank sub-system  140  comprising a concentrate holding tank  144 , a maple sap holding tank  142  and a permeate holding tank  146 . It should be noted that the pumping sub-system is not shown in this figure. 
     In conventional systems, concentrate is recuperated by injecting permeate into the membrane sub-system in order to push the concentrate out of the housings. This has the disadvantage that of diluting the concentrate (e.g. from 15′brix down to 2′brix) thus adding pure water into the concentrate holding tank. At some point the operator simply redirects the concentrate/permeate mixture to the drain in order to limit the addition of pure water into the concentrate holding tank. This results in concentrate waste. However, the use of compressed air, vacuum or a water pump as provided with the present membrane sub-system  120 ,  120 ′ allows for the complete recuperation of the concentrate still present in the housings  125  at the end of each day, e.g. 160 liters at 15′brix, compared to about 800 liters at 4′brix with the conventional method. 
     Further to the recuperation of concentrate, the present membrane sub-system  120 ,  120 ′ also provides for the evacuation of the washing solution from the housings  125  after a cleaning cycle, which accelerates the process and greatly reduces the amount of permeate required for rinsing. 
     Once the membrane sub-system  120 ,  120 ′ has been properly rinsed with permeate and then drained, as described above, the reverse osmosis system  100 ,  100 ′,  100 ″ can be restarted easily with a concentrate quickly attaining 15′brix as the housings  125  are free of permeate that affect the concentration of the sap entering the system at startup. This is a great advantage as the evaporation of the concentrate is a costly operation and any added permeate adds greatly to the cost. 
     A further advantage of the present membrane sub-system  120 ,  120 ′ is that the complete draining of all liquid from the individual housings  125  allows the reverse osmosis system  100 ,  100 ′,  100 ″ to be located in an unheated location. 
     It is further to be understood that the feed pump and filter bank set redundant configuration of the pumping sub-system  110 ′ may also be used with reverse osmosis systems other than the above described reverse osmosis systems  100  and  100 ′. 
     Although the present disclosure has been described by way of particular embodiments and examples thereof, it should be noted that it will be apparent to persons skilled in the art that modifications may be applied to the present particular embodiments without departing from the scope of the present disclosure.