Patent Publication Number: US-11377414-B2

Title: Plant and process for concentrating tartaric acid

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to Italian Patent Application No. 102019000015288, having a filing date of Aug. 30, 2019, which is hereby incorporated by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a plant and process for concentrating tartaric acid, in particular by means of a continuous process. 
     BACKGROUND ART 
     Tartaric acid is a white, crystalline diprotic organic acid. It is naturally present in many plants, especially grapes and tamarind (as well as other fruits). One of the salts thereof, potassium bitartrate, commonly known as cream of tartar, develops naturally in the winemaking process. 
     Industrially, tartaric acid is produced in large amounts. It is obtained from lees, a by-product of wine fermentation. 
     Tartaric acid has various fields of application. One of the uses thereof, when mixed with sodium bicarbonate, is as a leavening agent. As such, it can be added to foods as an antioxidant agent or to impart a sour taste. It is often added to certain foods such as candies, jams, and fruit juices to impart a sour taste thereto. It is used as an antioxidant and emulsifier in bread-making and in the preparation of leavening agents for cakes and bread. It is used in wine to balance the acidity thereof. It is used in the preparation of medicines: for example, mixed with sodium bicarbonate, it is used in the preparation of effervescent products to aid digestion. As for industrial applications, tartaric acid has the ability to chelate metal ions such as calcium and magnesium. Therefore, it is used both in the agricultural industry and in the metallurgical industry, to favor, for example, the complexation of micronutrients present in soil or for cleaning metal surfaces (aluminum, copper, iron, or metal alloys). 
     To date, the production process of tartaric acid includes a concentration step in which the diluted tartaric acid undergoes a concentration process, in order to obtain concentrated tartaric acid. 
     This process usually takes place inside an evaporation plant. The physical principle on which this type of plant is based is an evaporation principle which exploits the different boiling points (and therefore evaporation) of the components of a solution (diluted tartaric acid in this case). Indeed, the solutions subjected to this type of process usually consist of a solute having a higher boiling point than that of the solvent. Thereby, by heating the solution up to the solvent boiling temperature, the latter will evaporate, concentrating the solution. 
     The possibility of arranging a plant capable of concentrating tartaric acid which is produced efficiently and with low energy consumption is thus a need felt in the market. 
     Furthermore, the tartaric acid solutions to be concentrated are usually solutions whose tendency to crystallization is high, which makes them problematic solutions when placed in an evaporation plant. Indeed, using an easy crystallization solution inside an evaporation plant can cause the formation of encrustations inside the walls of the plant where the solution flows, with consequent damage to the plant itself. 
     When working with an evaporation plant for concentrating solutions, another parameter to consider is the measurement of the concentration of the solution to be concentrated. In fact, it is important that the solution is only extracted from the plant when it is certain that the solution has reached a certain concentration value. Therefore, the identification and use, within the plant, of a system which allows the continuous measurement of the concentration of the solution to be concentrated is an important aspect for the good yield of the concentration process. 
     SUMMARY OF THE INVENTION 
     Therefore, it is object of the present invention to provide a plant and process for concentrating tartaric acid which is efficient, ensures low energy consumption, allows an easy concentration of solutions tending to crystallization, and has a system for the continuous measurement of the tartaric acid concentration to be concentrated. 
     This object is achieved by a plant and process for concentrating tartaric acid as outlined in the appended claims, the definitions of which form an integral part of the present patent application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood from the following detailed description of preferred embodiments thereof, given by way of not limiting example, with reference to the accompanying drawings, in which: 
         FIG. 1  shows the plant for concentrating tartaric acid according to the present invention. 
         FIG. 2  shows a detail of the plant of  FIG. 1 . 
     
    
    
     In the accompanying drawings, equal or similar elements will be indicated by the same reference numerals. 
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1 and 2 , a first object of the present invention is shown, i.e., a plant  10  for concentrating a tartaric acid solution comprising: 
     a first  12  and a second  14  evaporation unit, in which said first  12  and second  14  evaporation units are arranged in series; 
     a pump for feeding a diluted tartaric acid solution  16  into said first evaporation unit  12 ; 
     a barometric condenser  18  placed downstream of said second evaporation unit  14 , 
     a system for feeding a first low-temperature vapor  20  into said first evaporation unit  12 . 
     Preferably, the tartaric acid solution comprises tartaric acid and sulfuric acid, the latter at a concentration between 3% and 5%, preferably about 4%. 
     Preferably, each of said first  12  and second  14  evaporation units comprises: 
     i) a heat-exchange evaporation chamber  22 , in which the first vapor comes into contact with the tartaric acid solution to be concentrated, 
     ii) a liquid-aeriform separation chamber  24 , connected to a head portion  26  of said evaporation chamber  22 . 
     Preferably, the first vapor is saturated aqueous vapor having a temperature between 70° C. and 90° C., preferably about 80° C. 
     Preferably, said heat exchange evaporation chamber  22  is an apparatus known to those skilled in the art in which thermal energy is exchanged between two elements having different temperatures. According to a preferred embodiment of the present invention, the above elements are the tartaric acid solution and the first vapor. In fact, the heat-exchange evaporation chamber  22  receives the first low-temperature vapor, by means of which the exchange of thermal energy takes place between the first vapor and the tartaric acid solution. This thermal energy exchange allows to heat the solution until the boiling temperature of the tartaric acid solution is reached, resulting in the formation of a second vapor (vapor of the solvent contained in the tartaric acid solution) and accumulation in the head portion  26  of the evaporation chamber  22  of an aeriform phase consisting of the aforesaid second vapor. Indeed, the amount of energy required for evaporation is supplied by the first low-temperature vapor. 
     Preferably the heat-exchange evaporation chamber  22  of the first evaporation unit  12  receives the first low-temperature vapor from the system for feeding the first low-temperature vapor  20 . 
     The liquid-aeriform separation chamber  24  is also preferably an apparatus known to those skilled in the art in which a separation of the aeriform phase coming from the head portion  26  of the evaporation chamber  22  is carried out. In fact, the aforesaid aeriform phase may also comprise, in addition to the second vapor produced by the evaporation of the tartaric acid solution, the tartaric acid particles dragged from the evaporation chamber  22 . Therefore, inside the liquid-aeriform separation chamber  24 , there is a separation between the properly aeriform phase (second vapor) and the dragged tartaric acid particles. 
     Two unitary operations are thus carried out inside the evaporation chamber  22  and the separation chamber  24 : the heat exchange between the first vapor and the tartaric acid solution and the separation between the properly aeriform phase and the dragged tartaric acid particles. 
     Preferably inside the heat-exchange evaporation chamber  22  of the second evaporation unit  14 , the tartaric acid solution has a temperature between 50° C. and 60° C., preferably about 56° C., and a pressure between 0.07 BarA and 0.11 BarA, preferably about 0.09 BarA. While on the other hand, preferably, inside the heat-exchange evaporation chamber  22  of the first evaporation unit  12 , the tartaric acid solution has a temperature between 60° C. and 70° C., preferably about 66° C. 
     According to a preferred embodiment of the invention, the barometric condenser  18  is connected to a vacuum pump  52  and to a system for circulating water  54  inside the condenser. Advantageously, the barometric condenser  18  condenses the properly aeriform phase exiting the second evaporation unit  14 . 
     Furthermore, preferably, the separation chamber  24  of the second evaporation unit  14  is connected to the barometric condenser  18  through an acidic solution separation chamber  44  being placed in an intermediate position between the separation chamber  24  of the second evaporation unit  14  and the barometric condenser  18 . The function of the acidic solution separation chamber  44  is to separate any acidic residues present in the properly aeriform phase exiting the separation chamber  24  of the second evaporation unit  14 . 
     Each of said first  12  and second  14  evaporation units also preferably comprises a connecting portion  28  which connects the liquid-aeriform separation chamber  24  to a bottom portion  30  of said evaporation chamber  22 , in which said connecting portion  28  comprises a column  32  which extends along a vertical axis. 
     Preferably, the column  32  of the first evaporation unit  12  is connected to the pump for feeding a diluted tartaric acid solution  16 , thus allowing the introduction of the diluted tartaric acid solution to be concentrated into the first evaporation unit  12  and therefore into the plant  10 . 
     Each of said first  12  and second  14  evaporation units further comprises, preferably, a recirculation pump  34  for the tartaric acid solution operatively connected to said connecting portion  28 , for recirculating the tartaric acid solution from said separation chamber  24  to said evaporation chamber  22 . 
     According to a preferred embodiment, the tartaric acid particles, dragged from the evaporation chamber  22  and separated from the properly aeriform phase inside the liquid-aeriform separation chamber  24 , fall by gravity into the column  32 , joining the tartaric acid solution already present in the connecting portion  28 . 
     The presence of the recirculation pump  34 , allowing the recirculation of the tartaric acid solution, advantageously allows to have a forced-circulation plant  10  for concentrating a tartaric acid solution. The forced circulation creates a turbulent motion inside the tartaric acid solution which ensures a high exchange coefficient between the first vapor and the tartaric acid solution and allows an easy concentration of a solution tending to crystallization such as that used in the plant  10  according to the present invention. 
     Furthermore, the presence of recirculation pumps  34  and of a pair of evaporation units placed in series advantageously ensures low energy consumption. 
     According to a preferred embodiment of the plant  10  of the present invention, said first  12  and second  14  evaporation units are, preferably, connected by a pipe for transferring the partially concentrated tartaric acid solution  36  placed at a bottom portion  38  of said evaporation units  12 ;  14  and by a pipe for transferring the properly aeriform phase  40  from a head portion  42  of the separation chamber  24  of the first evaporation unit  12  to the evaporation chamber  22  of the second evaporation unit  14 . 
     These connections not only allow the series connection of the two evaporation units  12 ;  14 , but also the passage of the partially-concentrated tartaric acid solution and of the properly aeriform phase, created in the first evaporation unit  12 , from the first evaporation unit  12  to the second evaporation unit  14 . In particular, the pipe for transferring the partially concentrated solution  36  preferably connects a bottom portion of the connecting portion  28  of the first evaporation unit  12 , placed downstream of the column  32 , with a bottom portion of the column  32  of the second evaporation unit  14 . 
     Still according to a preferred embodiment of the plant  10  according to the present invention, the column  32  of the connecting portion  28  of the second evaporation unit  14  preferably and advantageously comprises a pair of facing-flange pressure sensors  46 , each coupled to a fluid separator preferably in tantalum, in which the pressure sensors  46  are placed at a distance between 1.5 m and 2.5 m, preferably about 2 m, and are connected to a differential pressure transmitter  48  in turn connected to a volumetric pump  50  for extracting concentrated tartaric acid from the plant  10 , said volumetric pump  50  being controlled on the basis of an electrical signal sent by the differential pressure transmitter  48  between 4 mA and 20 mA. 
     Preferably, said control takes place by means of a feedback control adapted to allow the extraction of concentrated tartaric acid from the plant  10  only when the pressure value detected by the differential pressure transmitter  48  is within ideal values between 1 kg/l and 1.5 kg/l, values which correspond to the sending, by the differential pressure transmitter  48 , of the electrical signal between 4 mA and 20 mA. 
     The pair of sensors  46  is preferably placed at the aforesaid distance along a vertical axis along which the column  32  of the connecting portion  28  extends. 
     As known, the fluid separators are used when the pressure sensors  46  to which they are coupled must not come into contact with the process fluid. Therefore, they serve the function of transmitting the pressure variations of the fluid flowing in the plant  10  to the instrument (the differential pressure transmitter  48 , in the case of the present invention), while keeping it isolated from the pressure sensor  46 . Suitable types of fluid separators according to the present invention are, for example, fluid separators in titanium, nickel, tantalum. The fluid separators of the present invention are preferably in tantalum. 
     The differential pressure transmitter  48  is also preferably connected to a flow rate sensor  56  placed downstream of the volumetric pump  50 . The function of the flow rate sensor  56  is to measure the flow rate of concentrated tartaric acid exiting the plant  10 . Preferably, the flow rate sensor  56  carries out a second control on the volumetric pump  50 . Preferably said second control also takes place by means of a feedback control adapted to keep the flow rate within ideal values. Preferably said ideal values are between 0 m 3 /h and 10 m 3 /h. 
     For a detailed description of the operation and diagram of the signals transmitted by the pressure sensors  46 , and by the flow rate sensors, to the volumetric pump  50 , reference should be made to the following of the present description. 
     The present invention further relates to a process for concentrating tartaric acid comprising the steps of: 
     providing a plant  10  according to the above description; 
     performing a first concentration, by evaporation, of the diluted tartaric acid solution, inside the first evaporation unit  12 ; 
     performing a second concentration, by evaporation, of the partially concentrated tartaric acid solution from the first evaporation unit  12 , inside the second evaporation unit  14 ; 
     According to a preferred embodiment of the present invention, the process for concentrating tartaric acid preferably comprises the following steps: 
     providing a plant  10  according to the above description; 
     performing a first concentration, by evaporation, of the diluted tartaric acid solution, inside the first evaporation unit  12 ; 
     performing a second concentration, by evaporation, of the partially concentrated tartaric acid solution from the first evaporation unit  12 , inside the second evaporation unit  14 ; 
     setting, as a basal pressure difference ΔP measured between the first and second sensors of the pair of sensors  46  present in the column  32  of the connecting portion  28  of the second evaporation unit  14 , the pressure difference which would be measured in a 2 m high water column, corresponding to a density of 1 kg/l, and assigning the zero value to said ΔP. 
     measuring the pressure of the tartaric acid solution flowing inside the column  32  of the connecting portion  28  of the second evaporation unit  14  by means of the aforesaid pair of pressure sensors  46 ; 
     sending the measured pressure values to the differential pressure transmitter  48 , which, when detecting a ΔP value equal to a density between 1 kg/l and 1.5 kg/l, preferably about 1.3 kg/l, sends an electrical feedback control signal between 4 mA and 20 mA, preferably about 17 mA, to the volumetric pump  50  which controls the extraction of the concentrated tartaric acid solution from the second evaporation unit  14 . 
     Therefore, the process for concentrating tartaric acid according to the present invention preferably begins with the introduction, by means of the feed pump  16 , of the diluted tartaric acid solution into the column  32  of the connecting portion  28  of the first evaporation unit  12 . From here the diluted tartaric acid solution flows, due to the recirculation pump  34 , into the heat-exchange evaporation chamber  22  of the first evaporation unit  12 . Here the diluted tartaric acid solution encounters the first low-temperature vapor, coming from the feed system  20 , and an exchange of thermal energy takes place between the first vapor and the diluted tartaric acid solution. This exchange of thermal energy leads to an increase in the temperature of the diluted tartaric acid solution until the boiling temperature thereof is reached. Once the aforesaid boiling temperature has been reached, the solvent contained within the solution begins to evaporate, creating a second vapor. An aeriform phase thus accumulates in the head portion  26  of the evaporation chamber  22 , consisting of the aforesaid second vapor and any residual tartaric acid particles which are dragged during the evaporation. This aeriform phase then passes inside the liquid-aeriform separation chamber  24  of the first evaporation unit  12 , in which the separation takes place between the properly aeriform phase (second vapor) and the tartaric acid particles dragged by the head portion  26  of the evaporation chamber  22 . The tartaric acid particles dragged by the head portion  26  of the evaporation chamber  22  fall by gravity into the column  32  of the connecting portion  28  of the first evaporation unit  12 , thus adding themselves to the diluted tartaric acid solution coming from the feed pump  16 . The properly aeriform phase passes instead inside the pipe for transferring the properly aeriform phase  40  to enter the heat-exchange evaporation chamber  22  of the second evaporation unit  14  where it meets the partially concentrated tartaric acid solution coming from the first evaporation unit  12 . In fact, the pipe for transferring the partially concentrated tartaric acid solution  36  which connects to a bottom portion of the column  32  extends from a bottom portion of the connecting portion  28 , placed downstream of the column  32 , of the first evaporation unit  12  of the connecting portion  28  of the second evaporation unit  14 . Through this pipe  36  the partially concentrated tartaric acid solution passes from the first evaporation unit  12  to the second evaporation unit  14  and enters the column  32  of the connecting portion  28  of the second evaporation unit  14 . The partially concentrated tartaric acid solution is transported here, due to the action of the recirculation pump  34 , inside the heat-exchange evaporation chamber  22  of the second evaporation unit  14  where it meets the aforesaid properly aeriform phase and where a heat exchange between the two takes place. The properly aeriform phase heats the partially concentrated tartaric acid solution until it reaches the boiling temperature thereof. Once this temperature has been reached, the solvent of the partially concentrated solution begins to evaporate, creating, as for the first evaporation unit  12 , an aeriform phase comprising a second vapor and any tartaric acid particles. As in the first evaporation unit  12 , also in the second evaporation unit  14  the aeriform phase passes into the separation chamber  24  (of the second evaporation unit  14 ) where the separation between the properly aeriform phase (second vapor) and the tartaric acid particles takes place, which fall by gravity into the column  32  of the connecting portion  28  of the second evaporation unit  14 . The properly aeriform phase of the second evaporation unit  14  instead passes inside the acidic solution separation chamber  44  where the separation of any acidic gases present in the properly aeriform phase takes place. The properly aeriform phase exiting the acidic solution separation chamber  44  passes inside the barometric condenser  18  where the condensable vapors are condensed and extracted from the plant  10 , while any non-condensable gases are extracted by means of a vacuum pump  52 . 
     The pair of pressure sensors  46  is present inside the column  32  of the connecting portion  28  of the second evaporation unit  14 , the pair measuring the pressure of the tartaric acid solution in transit. The pressure measurement value is sent to the differential pressure transmitter  48  which when it detects a pressure value between 1 kg/l and 1.5 kg/l (preferably when it detects a pressure signal of about 1.3 kg/l), pressure values set as ideal set points, sends a signal (between 4 mA and 20 mA, preferably about 17 mA) to the volumetric pump  50 , thus controlling the extraction of the concentrated tartaric acid solution from the second evaporation unit  14 . 
     Downstream of the volumetric pump  50  there is also preferably a flow rate sensor  56 , the purpose of which is to measure the flow rate of the concentrated tartaric acid solution exiting the second evaporation unit  14 . If the measured range is between 0 m 3 /h and 10 m 3 /h, (preferably about 4.5 m 3 /h), flow rates set as ideal set points, the flow rate sensor  56  sends a second feedback control signal to the volumetric pump  50 , controlling the extraction activity of concentrated tartaric acid from the plant  10 . 
     Therefore, the plant  10  and the process for concentrating tartaric acid according to the present invention have the advantages of ensuring low energy consumption, allowing an easy concentration of solutions tending to crystallization, and allowing the continuous measurement of the tartaric acid concentration to be concentrated. 
     The plant  10  and the process for concentrating tartaric acid according to the present invention also have the advantage of accurately obtaining concentrated tartaric acid, due to the repeatability provided by the double feedback control mechanism provided in the plant  10  and in the related process. The presence of the two feedback controls allows to maintain the pressure values, and therefore the concentration, of the concentrated tartaric acid and the values of the flow rate of concentrated tartaric acid leaving the plant  10  around ideal pre-set values, thus ensuring accuracy and repeatability.