KR20120009982A - Process Design Method for Water Conversion based on Forward Osmosis, and Recording Medium for the Same - Google Patents

Abstract

PURPOSE: A method for planning a forward osmosis desalination process and a recording medium thereof are provided to combine the process conditions for feedback for maximizing profits, thereby efficiently searching the process conditions for an economic desalination process. CONSTITUTION: A draw solute type of draw solution is selected. Physical properties for the draw solute type are acquired. The utility consumption and investment cost for separating processes of the draw solute are calculated by the physical properties of the draw solute. A separation process is displayed at a minimum cost based on the total of the utility consumption and investment cost. The draw solute type is selected by the usage purpose of desalinated water by a forward osmosis.

Description

Process Design Method for Water Conversion based on Forward Osmosis, and Recording Medium for the Same}

The present invention relates to a forward osmosis desalination process design method and a recording medium therefor. More specifically, the process design method selects and combines the most important process conditions in the forward osmosis desalination in a manner that maximizes profit. The present invention relates to a forward osmosis desalination process design method and a recording medium for allowing the designer to design a desalination process with the most economical process conditions for the forward osmosis desalination.

Due to climate change due to global warming and industrial water increase due to industrialization, the global water shortage problem is getting serious. The solution to the water shortage is the desalination technology using seawater which is abundant on the earth. Methods for removing salt from seawater can be divided into evaporation and reverse osmosis. Compared to the evaporation method, which consumes a lot of energy, the reverse osmosis method is a technology of commercialization stage, such as a lot of development and installation of a plant. However, reverse osmosis also consumes a lot of energy because it requires the use of a high pressure pump to produce water. Therefore, technology development for forward osmosis method with low energy consumption is required.

Osmosis is the movement of water due to the difference in osmotic pressure when different concentrations of solution are separated by membranes with selective permeability. Reverse osmosis (RO) is a process in which pure water is obtained by applying artificial pressure above osmotic pressure to high feed water and moving from high concentration to low concentration. Reverse osmosis is a process that uses water pressure, but in the forward osmosis (FO) process, water transfer occurs due to the osmotic pressure difference between the membranes.

In order to generate water flow in the forward osmosis process, a higher concentration of draw soluton is used than the feed water. The induction solution should have a higher osmotic pressure than the feed water, and the induction solution diluted in the forward osmosis process should be easy to reconcentrate. Solutes used in the induction solution include sulfur dioxide, aliphatic alcohols, aluminum sulfate, glucose, fructose, potassium nitrate, ammonium bicarbonate and the like.

Osmotic phenomena between membranes using an induction solution causes the movement of water from the seawater to the high concentration solution, and the method of separating and concentrating the inducing solution from the diluted induction solution and reusing it to produce fresh water is forward osmosis seawater desalination. A research team from Elimelech, a professor at Yale University, USA, demonstrated the pilot-scale desalination of seawater using an induction solution containing an appropriate ratio of ammonium carbonate and ammonium hydroxide.

1 is a conceptual diagram of forward osmosis seawater desalination using an ammonia-derived solution of carbon dioxide.

Referring to FIG. 1, pretreated water is introduced into one end of the membrane and a draw solution is introduced into the other end of the membrane. The water of the seawater introduced into one end of the membrane by osmotic pressure is introduced into the induction solution at the other end, and the solute of the induction solution is recovered again, and then converted into drinking water through a post-treatment process.

However, the forward osmosis method requires more process variables (eg, solute type, solute separation method, and operating conditions) than reverse osmosis, and the economical efficiency of the process is largely determined by the selection of such process variables.

Therefore, the problem to be solved by the present invention is to provide a process design method of forward osmosis desalination, which can select the optimal process conditions in a more economical manner.

Another object of the present invention is to provide a recording medium having recorded thereon program instructions for implementing the design method.

In order to solve the above problems, the present invention is a process design method of the forward osmosis desalination process, the method comprises the steps of selecting the type of solute induction solution; Obtaining physical property information on the selected type of inducing solute; Calculating utility requirements and investment costs of a plurality of separation processes for the derived solutes according to the obtained physical properties of the derived solutes; And displaying the minimum cost separation process among the plurality of separation processes as an optimal process based on the sum of the calculated utility cost and the investment cost as an optimal osmosis type desalination process design method. .

In one embodiment of the present invention, a plurality of types of candidates are selected in advance, and the above-described steps are performed for each of the selected solutes.

In addition, the kind of the inducing solute may be selected based on the use of water desalted by the osmotic pressure method. The separation process may be a distillation process or a membrane separation process, and the above-described steps for each process may be performed.

The present invention also provides a process design method of the forward osmosis desalination process, the method comprising the steps of (a) determining the purity of the solute candidate group and the production water according to the use of the production water; (b) searching for a separation process for the derived solute candidate group; (c) a process combination of maximizing profits is selected from among a combination of processes consisting of candidate groups of the induced solutes, types of each separation process, and operating conditions (pressure, number of steps) of each separation process. Provide a process design method of forward osmosis desalination process.

According to one embodiment of the invention, the step of separating the derived solute is a distillation step, the profit is calculated from the following formula (1).

Profit f (x) = price of desalted water R (x)-raw material cost M (x)-utility cost U (x)-investment cost I (x) (1)

In formula (1), x is a combination function of the pressure of the distillation process, the number of distillation column stages and the number of columns for the selected inducing solute.

According to another embodiment of the present invention, the investment cost is calculated from the following equation (2).

C _P = F _M C _V + C _PL + C _T (2)

In Equation (2), C _P is the total installation cost, C _V Is the vessel price of the distillation column (outer wall), C _PL is the price of the platform and ladder, C _T is the price of the tray tray and F _M is the price of the column material.

In addition, the said vessel price is determined from following formula (3).

Cv = exp [A + B * ln (W) + C * ln (W)] (3)

In Equation (3), A, B, and C are coefficients for price, and W is calculated as π (Di + tS) (L + 0.8Di) tSρ as the weight of the vessel (Di is the diameter of the vessel and L is the vessel). The length (height) of ts is the wall thickness of the vessel).

According to another embodiment of the present invention, the steps (b) and (c) are repeatedly performed for each of the inducer candidate groups, and the method may further include comparing the profits of the inducer candidate groups.

The present invention also provides a recording medium having recorded thereon program instructions for implementing the above method.

The forward osmosis process design method according to the present invention can feed back to the designer by combining the process conditions (solute type, separation process, process conditions, operating conditions) to maximize profits. This allows the designer to effectively search for the process conditions of an economical desalination process by using the present invention as compared to a method of simulating the process conditions for each solute and then optimizing it again from an economic point of view.

1 is a conceptual diagram of a seawater desalination process of the forward osmosis method.
2 is a flowchart illustrating a process design method according to an embodiment of the present invention.
Figure 3 is a step diagram of the process design method of the forward osmosis desalination process according to an embodiment of the present invention
Figure 4 is a step diagram of a process design method of the forward osmosis desalination process according to another embodiment of the present invention.
5A and 5B show a utility cost simulation process.
6 to 8 illustrate a practical example in which a preferred combination of process conditions is selected according to the present invention.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In addition, in order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals in the drawings indicate the same members.

Throughout the specification, when an element is referred to as " including " an element, it does not exclude other elements unless specifically stated to the contrary. The terms "part", "unit", "module", "block", and the like described in the specification mean units for processing at least one function or operation, And a combination of software.

In the present invention, in the forward osmosis-type freshwater treatment process, a candidate group of inducing solutes used in the induction solution is selected, and the information on the separation process, process conditions, and profits for the selected induction solutes is optimized. The present invention relates to a forward osmosis desalination process design method that presents the designer with the type of solute, separation process, and process conditions.

2 is a flowchart illustrating a process design method according to an embodiment of the present invention.

Referring to FIG. 2, first, physical properties are obtained from a physical database (DB) of candidate solutes. That is, the present inventors noted that the selection and separation process of the inducing solute in the forward osmosis desalination process is important in advance, and that the physical property information of the inducing solute candidate group is important for modeling and simulating it. That is, the present inventors use the physical property database which includes all the physical property information necessary for each separation process, depending on the type of separation process so suitability of the solute used in the induction solution. For example, thermal processes based separation processes such as distillation require boiling points, volatilities, chemical equilibrium constants, solubility, activity coefficients, and membrane processes. The physical properties such as mass transfer constants, solubility, solute penetration, etc. are required. This information can be calculated through parameters such as charge number, ionic radius, ionic strength, and so on, which are intrinsic properties of the solute, such as binary parameters and nonrandomness factors to express the non-ideality of the solute. In one embodiment of the present invention, the liquid activity coefficient model such as ElecNRTL, Pitzer, OLI MSE model and Redlich-Kwong-Soave equation is applied, but the scope of the present invention is not limited thereto.

Referring back to Figure 2, by simulating the separation process of the derived solutes based on the obtained physical property information, the process and energy required for separation of the derived solutes are predicted and calculated.

In other words, in the case of an electrolyte system, which accounts for most of the inducing solutes, in addition to the phase equilibrium in the separation process, accurate simulation is possible only when the chemical equilibrium is predicted. Simultaneously, the equilibrium between the gas and liquid phases of the molecules changes with temperature, pressure, and composition. This combination of chemical equilibrium and phase equilibrium models yields gas-liquid equilibrium (VLE) data, which can be used to simulate a variety of separation processes, for example thermal processes.

For example, induction distillation by distillation process, in addition to using a single distillation column, multi-stage column distillation (MSCD), multi-stage flash (MSF), and multi-effect distillation (MSD) And the like, it is possible to calculate the amount of utility required by these various process methods. In addition, the present invention further considers the initial cost of the installation of each process system as the investment cost, and considers the cost together with the utility cost to design an optimal desalination process combination. In the present invention, the simulation process for selecting solutes does not have enough information in the design of the actual process, and the appropriate solutes will always change depending on the energy price and the value of the produced water, investment cost, toxicity to the human body, environmental problems, etc. Note that it is essential to take this into account as it can. In other words, the inventors of the present invention can not determine the solubility suitability simply by thermodynamic efficiency, and thus, as an alternative, the new method of determining the inducing solute, the separation process, and the operating conditions through the profit maximization method that considers economic factors as a whole. To provide a desalination process design method.

Figure 3 is a step diagram of the process design method of the forward osmosis desalination process according to an embodiment of the present invention.

Referring to Figure 3, first, the type of solute derived induction solution is selected. In the selection of the inducing solute, not only one kind of inducing solute is selected, but a plurality of candidate groups are selected according to the purity, capacity, and the like of the produced water. For example, ammonium carbonate can be separated at a concentration of 50 ppm in agricultural water and 2 ppm or less in drinking water, and in drinking water, it is preferable to exclude substances such as sulfides and cyanide, which are highly toxic, from industrial candidates. In the case of water it is preferred to exclude highly corrosive oxides, chlorides, hydroxides. In this way, candidate groups of inducible solutes are selected in advance according to the use, purity, capacity, and the like of the produced water.

Thereafter, physical property information of the selected type of inducing solute is obtained. The physical property information may be various kinds of information required for a separation process as described above, and the required physical property information may be obtained from a conventional chemical property database.

Utility requirements and investment costs of a plurality of separation processes for the derived solutes are then predicted and calculated according to the obtained property information of the derived solutes. That is, the utility includes all the energy sources such as electricity, water, and gas required to maintain the separation process, and the utility requirement can be expressed in the form of cost. In addition, the present invention considers the initial installation cost required to process the selected production capacity as described above in the form of an investment cost, and based on the profit including the sum of the obtained utility cost and the investment cost. In the separation process, the separation process showing the maximum profit is represented as an optimal desalination process.

In one embodiment of the present invention, a plurality of kinds of materials may be selected in advance as the inducing solute, and the above-described steps may be performed for each of the selected inducing solutes. That is, utility cost and investment cost for each separation process are calculated according to the purity and capacity of the production water selected in advance for candidate materials A, B, and C. Thereafter, the separation process that can minimize the sum of the calculated utility cost and investment cost, and the optimum operating conditions and profits of the separation process are calculated and displayed. Subsequently, a material showing the maximum profit among candidate materials is selected, and an optimum separation process and operating conditions corresponding to the material are fed back to the designer.

In one embodiment of the present invention, the separation process is a distillation process or a membrane separation process, and all of the above-described steps are performed for each process.

Figure 4 is a step diagram of a process design method of the forward osmosis desalination process according to another embodiment of the present invention.

Referring to FIG. 4, the method first determines the purity of the derived solute candidate group and the produced water according to the use of the produced water. For example, in the case of drinking water, purity is determined by relevant laws and regulations, and candidate solute candidate groups are determined. Subsequently, a separation process for the candidate solute candidate group is searched, and then a process of maximizing profits among the process combinations consisting of candidate groups of the induced solutes, types of each separation process, and operating conditions (pressure, fraction) of each separation process. The combination is selected.

Another embodiment of the present invention provides a design method for feeding back the designer the process conditions that can generate the maximum profit for the separation process after the distillation process.

As a factor in selecting an optimal process condition in the present invention, profit is provided, wherein the profit is represented by the following formula.

Profit f (x) = price of desalted water R (x)-raw material cost M (x)-utility cost U (x)-investment cost I (x) (1)

Further, in another embodiment of the present invention, the pressure, stage number, and column number of various distillation processes may be used in the method of separating the solutes by distillation process, where the profit may be arbitrarily determined pressure, stage and Consideration is given based on the number of columns.

That is, the present invention simulates the separation process through various simulation programs using the physical property information and the phase equilibrium information as shown in FIG. 5, and calculates and obtains the number of distillation column and the required energy for the unit production means. . Figure 5a shows the chemical equilibrium state represented by the above formula by calling the activity coefficient of the NH3, H2O, CO2, NH4 +, OH-, H3O +, OH-, CO32- active ingredient for ammonium carbonate through a database (Datebase), 5B illustrates a process of simulating a separation process in a distillation column by calculating a phase equilibrium state represented by the above formula. The simulation may be performed through a chemical simulation program such as HYSIS, PRO-II, ASPEN, but the scope of the present invention is not limited thereto.

In the present invention, together with the utility cost which is the maintenance cost as described above, the investment cost which is the initial cost is considered in the process design, and the investment cost is calculated from the following equation (2).

C _P = F _M C _V + C _PL + C _T (2)

In Equation 2, C _P is the total installation cost, C _V Is the vessel price of the distillation column (outer wall), C _PL is the platform and ladder price, C _T is the distillation column tray price and F _M is the coefficient of distillation column material, and the coefficient increases as the price increases. .

In addition, the vessel price is determined from the following equation (3),

Cv = exp [A + B * ln (W) + C * ln (W)] (3)

In Equation (3), A, B, and C are coefficients for price, and the coefficient increases as the price increases. W is also calculated as π (Di + tS) (L + 0.8Di) tSρ by the weight of the vessel, where Di is the diameter of the vessel and L is the length (height) ts of the vessel. That is, in the initial investment cost, since the large-capacity distillation column vessel (outer wall) becomes a very important part, the present invention includes the total installation cost as one parameter.

In the present invention, the process conditions based on the above-described separation process search and profit for each of the derivatives candidate groups are simulated, and thus the profits for each of the derivatives candidate groups can be compared. That is, the most profitable combination is searched among numerous combinations for each candidate solute candidate group, each process type, and operation conditions (pressure, number of stages) of each process, and the found combination is displayed and fed back to the designer.

Hereinafter, a practical example in which a preferred combination of process conditions is selected according to the present invention will be described.

Example of execution  One

1. Conditions

Energy price: 0.008 $ / khw

Use of production water: Drinking water

Production capacity of the plant: 200 kg per hour

Purity: 2 ppm

2. Results (see Figure 6)

Under the above conditions, it is most effective to use ammonium carbonate as the solute, atmospheric pressure, 13 stages, and a single distillation column (column number 1).

Example of execution  2

1. Conditions

Energy price: 0.02 $ / khw

Use of production water: Drinking water

Production capacity of the plant: 200 kg per hour

Purity: 20 ppm

2. Results (see Figure 7)

Under these conditions, 0.07 atmospheric pressure, single distillation column, 11 stages are the most economical.

Experimental Example  3

1. Conditions

Energy price: 0.05 $ / khw

Use of production water: Drinking water

Production capacity of the plant: 400 kg per hour

Purity: 1ppm

2. Results (see Figure 8)

Under the above conditions, 0.07, 0.28 atmospheric pressure, double distillation column (column number 2), 14 stages are most effective.

The present invention can feed back to the designer the combination information of the process that maximizes the profits, the process conditions thereof, and the type of flow solu- tion that can achieve this, based on the physical property information according to the derived solute.

In addition, the design method according to the present invention can be embodied as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of the recording medium include ROM, RAM, optical disk, magnetic tape, floppy disk, hard disk, nonvolatile memory, and the like, and also include a carrier wave (for example, transmission through the Internet). The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible.

Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (13)

In the process design method of the forward osmosis desalination process, the method
Selecting a type of inducing solution of the inducing solution;
Obtaining physical property information on the selected type of inducing solute;
Calculating utility requirements and investment costs of a plurality of separation processes for the derived solutes according to the obtained physical properties of the derived solutes; And
And a step of displaying the minimum cost separation process among the plurality of separation processes as an optimal process based on the sum of the calculated utility cost and the investment cost.
The method of claim 1,
The derivation method of the forward osmosis desalination process, characterized in that the plurality of candidates are preselected, the step of claim 1 is performed for each of the selected solutes.
The method of claim 2,
The kind of the induced solute is a forward osmosis desalination process design method, characterized in that selected based on the use of water desalted by the osmotic pressure method.
The method of claim 1,
The separation process is a distillation process or a membrane separation process, the forward osmosis desalination process design method, characterized in that all of the steps of step 1 for each process.
A recording medium having recorded thereon program instructions for implementing the process design method according to any one of claims 1 to 4.
In the process design method of the forward osmosis desalination process, the method
(a) determining the purity of the solute candidate group and the production water according to the use of the production water;
(b) searching for a separation process for the derived solute candidate group;
(c) a process combination of maximizing profits is selected from among a combination of processes consisting of candidate groups of the induced solutes, types of each separation process, and operating conditions (pressure, number of steps) of each separation process. Process design method of forward osmosis desalination process.
The method of claim 6,
Separation process of the induced solute is a distillation process, the process design method of the forward osmosis desalination process.
The method of claim 7, wherein
The profit is calculated by the following formula (1) process design method of the forward osmosis desalination process.

Profit f (x) = price of desalted water R (x)-raw material cost M (x)-utility cost U (x)-investment cost I (x) (1)
In formula (1), x is a combination function of the pressure of the distillation process, the number of distillation column stages and the number of columns for the selected inducing solute.
The method of claim 8,
The investment cost is a process design method of the forward osmosis desalination process, characterized in that calculated from the following formula (2).

C _P = F _M C _V + C _PL + C _T (2)
In Equation (2), C _P is the total installation cost, C _V Is the vessel price of the distillation column (outer wall), C _PL is the price of the platform and ladder, C _T is the price of the tray tray and F _M is the price of the column material.
The method of claim 9,
The vessel price is a process design method of the forward osmosis desalination process, characterized in that determined from the following formula (3).
Cv = exp [A + B * ln (W) + C * ln (W)] (3)

In Equation (3), A, B, and C are coefficients for price, and W is calculated as π (Di + tS) (L + 0.8Di) tSρ as the weight of the vessel (Di is the diameter of the vessel and L is the vessel). The length (height) of ts is the wall thickness of the vessel).
The method of claim 6,
The process design method of the forward osmosis desalination process, characterized in that the steps (b), (c) is repeated for each of the candidate substance candidate group.
The method of claim 11, wherein the method is
The process design method of the forward osmosis desalination process characterized in that it further comprises the step of comparing the profit for each candidate group of the derived material.
A recording medium having recorded thereon program instructions for implementing the process design method of the forward osmosis desalination process according to any one of claims 6 to 12.

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