Abstract:
The invention relates to a method for washing textile and the like, especially in large scale industrial applications, and to a system for carrying out this method.

Description:
BACKGROUND OF THE INVENTION 
     1) Field of the Invention 
     The present invention relates to a method for washing textile and the like, especially in large scale industrial applications, and to a system for carrying out this method. 
     2) Prior Art 
     Water is one of the most important elements in a washing process whereby the object is to clean articles, for example textile, subjected to said process. As well as water, the washing result is dependent on other factors such as wash temperature, detergent and the mechanical action of washing. 
     There is a growing need for improved wash processes, especially with a particular emphasis on reducing the amount of water used due to the scarcity thereof in particular areas, and during hot seasons. Methods are also currently sought for reducing the amount of detergent used in order to prevent environmental problems which result when the detergent is released into the environment after use. 
     In certain areas of England for example, water is rationed during hot summers leading to problems for laundromats and industrial laundries. 
     Furthermore in some remote areas with poor access, such as the Greek islands, water has to be transported there by truck. This means that when this water is finished, there is a shortage of water until the next delivery. This is especially a problem for hotel laundries on such islands. 
     Moreover the price of water is ever increasing so that ways to reduce water usage are becoming increasingly sought after. 
     Due to these problems, much research has been done into the recycling of water in washing processes. 
     An existing method for treating water in a washing machine is described in the European patent application 0 467 028 from Zanussi. 
     SUMMARY OF THE INVENTION 
     This application describes a method for filtering water by means of reverse osmosis for domestic washing machines and dish washers, which has the object of softening the water, so that the amount of detergent necessary to provide an effective wash can be reduced. Purified water from the reverse osmosis step is stored in a tank until needed in the washing machine. 
     The concentrate from the reverse osmosis filter (which contains contaminants) is guided away, and kept in a separate tank such that this concentrate can be used for carrying out the first rinse cycle on a subsequent wash program. 
     Water from the last rinse from the previous wash program is returned to the first tank from where water is guided to the reverse osmosis unit whereby about 20% of the water in any giving wash program is recycled. 
     An object of the present invention is to provide an improved washing process wherein water is recycled for reuse in both main wash and rinse cycles while retaining and reusing heat in water. 
     According to a first aspect the present invention provides a process for washing objects such as textile and the like, comprising the steps of: 
     a) guiding water and detergent into a washing machine; 
     b) carrying out one or more wash and/or rinse cycles In the machine; 
     c) guiding the water from step b) into a reverse osmosis unit, where the water is subjected to reverse osmosis in order to remove contaminants from the water; 
     d) recycling water front step c) into the washing machine for use by one or more wash and/or rinse cycles wherein substantially all the recycled water is subjected to the reverse osmosis step c). 
     A significant saving in water and energy is provided with this process, with a reverse osmosis unit, contamination with a molecular weight of &lt;100 can be separated. 
     The recycled water is preferably used in at least two separate rinse cycles, and most preferably in a subsequent washing program. 
     Rinsing consumes a large part of the water necessary in washing processes especially with white wash for example for hotel and hospital linen. Until now, waste water from washing machines has not been resused for rinsing this sort of textile washed in the machine due to the risk of textile damage. In general, fresh mains water is used for this. 
     The water quality requirements for rinsing are different than for the use of water by other wash program phases. One of the main differences in the quality requirements of rinse water is the salt content thereof. If this salt content is too high in the so-called finishing equipment, it is difficult to treat the textile, whereby brown stains are caused on the textile which can also yield skin irritations. Waste water from the washing process has a high salt content mainly due to the salts present in the detergent. On using the process according to the present invention purified water can however be recycled for reuse in the rinsing phases where the main part of water is required for an individual program. 
     It is preferable to subject water which enters the washing cycle for the first time to a pre-treatment step (for example pre-filtration), before it enters the washing machine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details, characteristics and advantages of the present invention are laid out in the claims and the following specific description which refers to the figures wherein: 
     FIG. 1 schematically shows a first embodiment of a system of apparatus for carrying out the process according to the present invention; 
     FIG. 2 schematically shows a second embodiment of a system of apparatus for carrying out the process according to the present invention; 
     FIG. 3 schematically shows a working embodiment of a system of apparatus according to the present invention, and 
     FIG. 4 is a graph showing the capacity per hour of a plant as schematically shown in FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Mains water is guided through a conduit  2  into a washing machine  4  (FIG.  1 ). A pre-treatment unit (not shown) is arranged in this conduit  2 . Used washing water is guided from the washing machine  4  through a waste water outlet  6  into a second conduit  8  whereafter it is pumped into a first reservoir  12  by means of a pump  10 . Water is pumped through a conduit  14  from the reservoir  12 , by means of the pump  16 , into a reverse osmosis unit  18  where the washing water is purified and salt is removed from it. This purified water is pumped from the reverse osmosis unit  18  into a second reservoir  22  via a third conduit  20 . From this reservoir  22 , this water is pumped back into the washing machine  4  by means of the pump  26  through a conduit  24  for reuse. As the water is directly re-used, there is effectively no build up of undesirable smells which could transfer to the washed textiles. 
     During a washing program any additionally required water can be supplied to the machine through the conduit  2 . The required amount of fresh mains water is dependent on the amount of water that remains in the textile after removal from the machine following washing and centrifuging, as well as the water remaining behind in the concentrate, which is guided away from the reverse osmosis separating unit  18  via the conduit  28 . Since the contaminant concentrate is removed from the recycled water no substantial build up of salt occurs. 
     This concentrate is preferably brought to a biological break-down unit where it can be biologically broken down by micro-organisms. Due to the relatively small volume of concentrate, the required amount of buffered water is greatly reduced by contrast to existing systems; buffer tanks with a capacity of roughly 2-3 m 3  can be used instead of 600-800 m 3 . 
     The system  30  (FIG. 2) comprises twice the system apparatus as the system according to FIG. 1, i.e. comprises two reservoirs and one reverse osmosis unit for treating waste water separately from the pre-wash and waste water from the main wash ( 2 - 28 ,  2 - 28 ′) respectively, in order to optimize the system with respect to quality requirements. A filter unit for removing coarser material, for example a micro or ultra filtration unit, can be added on the waste water unit in order to further improve the process. 
     With respect to FIG. 1, calculations have demonstrated the following water and energy savings. 
     Saving Calculation for FIG.  1 : 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Washing process for standard white wash on a washer-extractor 
               
             
          
           
               
                   
                   
                   
                 Temperature 
                 Delta 
               
               
                   
                 1/kg IN 
                 1/kg OUT 
                 ° C. 
                 T 
               
               
                   
                   
               
             
          
           
               
                 Pre-wash 
                 4 
                 3 
                 35 
                 25 
               
               
                 Main wash 
                 3 
                 3 
                 70 
                 60 
               
               
                 Rinse 1 
                 5 
                 5 
                 36 
                 26 
               
               
                 Rinse 2 
                 5 
                 5 
                 36 
                 26 
               
               
                 Rinse 3 neutral 
                 5 
                 5.4 
                 36 
                 26 
               
               
                 Remaining moisture 
                 0.6 
               
               
                 in the textile 
               
               
                 Total water consumption 
                 22 
               
               
                 Total water discharge 
                   
                 21.4 
               
               
                   
               
             
          
         
       
     
     Water Saving 
     A recovery of 70% means that a saving of roughly 68% is achieved on the total water consumption, i.e. 14.98 l. 
     Energy Saving 
     In existing systems a determined heat content is discharged into the sewer. If one takes a reference temperature of 10° C. for incoming mains water, 2752.68 kJ of heat are discharged per kg textile. 
     If that water is recycled according to the system of the present invention, 6.42 l at 40° C. are discharged. This has a heat content of 808,92 kJ/kg textile. This represents a saving of 71% with respect to the existing situation. 
     Savings Calculation for FIG.  2 : 
     When one carries out the same calculations for FIG. 2, wherein the waste water from the pre-wash is separately treated, a water saving of 72% with respect to the total water consumption is achieved. 
     In this case the energy saving is 75% 
     Furthermore the waste water purification is more economical since filtration of water from the pre-wash can be carried out more easily and cheaply. This is due to the lower requirements with respect to the reuse of water for a pre-wash. 
     Experimental 
     Table 2 shows experimental results from a wash program carried out in a system according to FIG.  1 . 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                 Water 
                   
                   
               
               
                   
                   
                   
                 consumption 
                 Water 
                 Water 
               
               
                   
                   
                   
                 in liters 
                 supplied 
                 supplied 
               
               
                   
                 Time in 
                 Temperature 
                 water per 
                 from 
                 from the 
               
               
                   
                 minutes 
                 in ° C. 
                 kg textile 
                 the mains 
                 filter unit 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Soak 
                 0.5 
                   
                   
                   
                   
               
               
                 Pre-wash 
                 12 
                 31 
                 4 
                 1 
                 3 
               
               
                 Drain 
                 0.5 
               
               
                 Main 
                 10 
                 70 
                 4 
                   
                 4 
               
               
                 wash 
               
               
                 Drain 
                 0.5 
               
               
                 1. rinse 
                 4 
                 50 
                 6 
                   
                 6 
               
               
                 Inter- 
                 2 
               
               
                 mediate 
               
               
                 centrifuge 
               
               
                 2. rinse 
                 4 
                 30 
                 7 
                   
                 7 
               
               
                 Inter- 
                 2 
               
               
                 mediate 
               
               
                 centrifuge 
               
               
                 1. rinse 
                 4 
                 15 
                 7 
                 6 
                 1 
               
               
                 End 
                 10 
               
               
                 centrifuge 
               
               
                 Total 
                 49.5 
                   
                 28  
                 7 
                 21  
               
               
                   
               
             
          
         
       
     
     The average temperature of the water from the filter unit was 36° C. 
     Of the water provided for filtering, roughly 75% is filtered and reused in the washing process. In the residue, being 25% (concentrate), the contamination was present which was filtered out. 
     In the soak/pre-wash only 3 liters of water, coming from the filter unit, was used per kg textile so that due to the addition of mains water the temperature in the bath is somewhat reduced. 
     In the pre-wash phase the dose of detergent used is roughly 20 g of detergent per kg of textile, and another 12.5 g of detergent er kg textile is supplied in the main wash. 
     A batch washing installation  50  (FIG. 3) consists of a soaking compartment  52 , a main wash compartment  54 , a rinse compartment  56 , and a neutralizing compartment 58, which controls the pH. 
     In working, typically 4 m 3 /hour is taken from the soak compartment  52 , this being stream  59 , and 6 m 3 /hour is taken from the main wash compartment  54 , this being stream  60 , these two streams  59 ,  60  respectively being combined to form stream  61  which is guided into a storage tank  62 . 
     From the storage tank  62 , stream  64  is pumped through pump  66  at a rate of 10 m 3 /hour to emerge as stream  68  which is guided through a course filter unit  70 , Stream  72  emitting from the filter  70  is guided into a second storage tank  74 . 
     Stream  75  is guided from this second storage tank  74  and pumped through a second pump  76  at a rate of 10 m 3 /hour (stream  77 ). 
     This stream  77  is guided into a reverse osmosis unit  78 . A concentrate stream  80  comprising undesirable contaminants and salts, is guided away from the reverse osmosis unit  78  at a rate of 2 m 3 /hour. 
     A purified stream  82  is guided away from the osmosis unit  78  at a rate of 8 m 3 /hour into a third storage tank  84 , into which fresh mains water  86  at a rate of 2 m 3 /hour is also guided. 
     Stream  88  is guided from the storage tank  84  through a pump  90 , the stream  92  being pumped by pump  90  at a rate of 10 m 3 /hour back into the batch washer  50  to a compartment of choice. 
     FIG. 4 shows the flow rate and flow temperature of the streams as measured in the system as shown in FIG. 3 during a period of 20 hours. 
     The invention is not limited to the above description, the requested rights are rather determined by the following claims.