GB2309017A - Particles of hygroscopic substances having water-permeable shells for use in physical phase-changing device - Google Patents

Abstract

A hygroscopic particle device 1, 2 consisting of a plurality of component robust enclosed shell 1 particles made from a water permeable substance whose innards are a water soluble hygroscopic substance 2. By diffusion of the mobile water species from the component particles, the particles spontaneously suspend themselves in a free pure water volume. Enclosing the component particles by a filtration membrane 4 admits the free pure water volume but holds back the particles. The device has application to the following: wet scrubbers, dehumidifiers, water desalination/purification, artificial self irrigating soils and energy production.

Description

A Versatile Physical Phase Changing Device This invention relates to a versatile hygroscopic particle and the spontaneous phase change of water vapour to liquid by hygroscopic substances.

The technology of micro-encapsulation allows the invention of a catalyst which promotes the spontaneous phase transition of water vapour to liquid water by the diffusion of water vapour across the selective membrane of a microencapsulation particle to its hygroscopic innards where it changes phase to the liquid form and spontaneously diffuses to suspend the micro-encapsulation particles in a free highly pure volume of water. The spontaneous nature of the phase transition - fully justified by thermodynamic analysis - results in: Cheap wet scrubbers for cleaning exhaust gases and general air-streams.

Self-regenerative dehumidifiers, regeneration is achieved by the gravitational potential energy of the condensed liquid in the free liquid water volume flowing away from the device.

Low energy consumption water purification'desalination: An artificial self-irrigating soil.

Energy production from the gravitational potential energy of the free water volume and/or the hot exit stream of vapour not condensed by the device.

According to the present invention (figure 2) there is provided a device consisting of a plurality of component robust enclosed semi-permeable shell particles 1, 2 made from a substance permeable only to water 1 whose component particle innards are a hygroscopic water soluble substance or substances 2 that spontaneously suspend themselves in a free volume of highly pure water permeated from within plurality of said components to without largely devoid of said hygroscopic substance or substances.

This patent will first set out the thermodynamic theory of: First order phase transitions.

A theoretical analysis of how a phase changing catalyst can be made.

A practical implementation of the catalyst by micro-encapsulation technology (the 'core' technology of this patent) and explanation of how the free water volume arrives (by reference to figures 3, 4, 5 and 6). Three specific core embodiments of the invention are described by Examples I, II, Ill.

I will then explain uses or configurations of the core technology that meet the first bulleted points in this description by reference to examples IV to XIII.

First order phase transitions First order phase transitions involve latent heat; when a substance changes phase it does so at constant temperature whilst heat energy is supplied. The energy discrepancy between the high and low energy phases is termed the latent heat. The possibility arises, if spontaneous phase transitions are possible.

of a spontaneous temperature rise due to energy balance considerations involving the latent heat: Consider the following (idealised) process:

M(vapour) at T1 e First Order state changing process o k x M(vapour) at T2 (1 (1 - k) x M(liquid) at T1 where M is mass of the working substance T1 and T2 are Kelxin temperatures, T2 ) T1 k is a mass fraction 0 S k I: < l Let the process occur at constant pressure.For the First Law modelling, I can use enthalpy: - H=U+PV eqn. 1 where H is the enthalpy of a substance and is a state variable U is the internal energy (state variable) P is pressure V is volume By the conservation of energy (Ist Law), Enthalpy of reactants before process = Enthalpy reactants after.

Enthalpy of M(vapour) at T1 AH = MCL(T,-T"f) + ML eqn. 2 where CL is the specific heat capacity of the liquid phase T,,f is a reference temperature L the latent heat of phase transition.

Enthalpy of(l-k) M(liquid) at T1: AH2 = (1k) MCL(T1-Tref) eqn. 3 Enthalpy of k M(vapour) at T2: AH3 = k M(CL(T1-TreO + L) + k MCv(T2-Tl) eqn. 1 where Cv is the specific heat capacity of the vapour phase Thus by 1st Law AH1 =#H2+#H3 # T2-T1 = (l-k)L / kCv eqn. 5 A temperature rise is predicted by the First Law.

However, first law modelling is not enough, one must use the Second Law in conjunction with the First.

For the Second Law modelling I shall break the process into two steps: Step 1: Heat withdrawn as part of gas is condensed (l-k) M(vapour) < (1 -k) M(liquid) Change in entropy at constant temperature AS, = -(l-k) ML / T1 eqn. 6 Step 2: Heat added as remaining vapour heated. k M(vapour) &commat; T1 < k M(liquid) # T2 Change in entropy of ideal gas like substance AS2 = k MCV ln (T2 t T,) eqn. 7 Total change in entropy is AS, + AS2 > 0 bv 2nd Law. Working the inequality.

k#L/(T1Cvln(T2/T1)+L) ineq. 8 All terms on the right hand side are finite and positive so k is less than unity. Hence the idealised process tells us that there exists a process or 'catalyst' capable of causing a spontaneous temperature rise in a substance by causing a spontaneous phase change in the substance. There are real substances that can cause a spontaneous phase change of water - thcse are known as hygroscopic substances. In thc nest section I shall prove that a phase changing catalyst can be made by use of hygroscopic substances and semi-permeable membranes.

Thermodynamic Analvsis of a Phase Changing. Catalvst Reference figure 1.

Figure 1 shows a vessel with a hygroscopic solution 2 inside it, at the bottom a semi-permeable membrane 1 allows the passage of liquid but not the hygroscopic agent. This is a manifestation of the device that can be analysed along the same lines as in the proceeding section of this description. It is in a environment consisting of a vapour atmosphere at T1 Kelvin.

is the chemical potential of the vapour at T1 Kelvin.

p1 is the chemical potential of the liquid at T1 Kelvin at the reference level height g= i = Pep6 is the chemical potential of the vapour at T1 at the altitude of the device opening (h meters), #e g= = pe 1 is the chemical potential of the liquid at the device exit pe 1 > ,ul which is elevated above the reference level height.

h is the chemical potential of the liquid in the hygroscopic solution ph < p g near the device opening bot is the chemical potential of the hygroscopic solution at the bottom of the vessel bot h > p6T2 is the chemical potential of the vapour at T2 Kelvin gT2 > g k is a mass fraction.

The vapour flows are modelled as having negligible effect on Pe g etc. At the vessel's surface there exists a thin layer of hygroscopic liquid at T2 Kelvin, all the excess heat from the condensation of the vapour is carried away by the exit vapour - I only model the steady state.

Using the thermodynamic identity near equilibrium: dU=TdS - PdV + #i idnj eqn. 9 It can be shown for two systems (A to B) transferring matter and enthalpy between them that the total entropy production is:dS=(1/TB- 1/TA)d# - #i( iB/TB - iA/TA)dni where TA, TB are absolute temperatures PA, PB are pressures VA, VB are volumes d is a transfer of enthalpy dn is a transfer of matter Using equation 10 to model the device depicted in figure 1.

Step 1) Heat withdrawn as part of vapour is condensed, (l-k) M(vapour) - > (1 -k) M(liquid) Change in entropy Second = -(l-k) / T1 (ph - p,jçdn = -(1-k)/Ti( h - g)dn eqn. 11 Step 2) Heat added as remaining vapour heated, k M(vapour) &commat; T1 o k M(liquid) C)a T2 Change in entropy dSHest = k (1/ T2 - 1/Ti) d# - k (pgT2 / T2 - 961 T,)dn eqn. 12 Step 4) The change in entropy as liquid leaves the hygroscopic solution by flow across the semi permeable membrane: : dSMcrnb = -(l-k) T1 ( - bot h)dn eqn. 13 We postulate that the total change in entropy, dScond + dSHeat + dSM,",b is greater than zero and that T2 is greater T 1 for the operation of the device to occur.

Surnaming, cancelling botch and ph which are equal and rearranging the inequality we see that: (pe j - pe g)dn < k ( < I IT2- 1) d - ( (T, IT2) ,n - g)dn) Since the left hand side is positive and d# = hOdn (ho is the molar enthalpy of the vapour) which is massive, the right hand side is negative. Thus we write k as:k < (pe j-pe g)/(-((T1/ T2) gT2)+(T1/T2 - 1) ho) ineq. 14 We note that k is less than unity and the process occurs. Conceptually, as long as the vapour pressure at height is greater than the vapour pressure exerted by the hygroscopic solution, then water will condense forming a 'head' that squeezes water through the membrane.The temperature rise of the exit gas stream and the potential energy of the condensed water leaving the device provide energy sources.

A Practical Implementation of the Core Technology The core technology can be implemented by making small robust particles 1,2 (figure 2) whose enclosing walls are a semi-permeable membrane 1 and innards are hygroscopic solution 2. I shall now prove that a plurality of component particles 1, 2 spontaneously suspend themselves in a free water volume.

(Vesicles refers to component particles 1, 2) Let N spherical vesicles (the don't have to spherical but they will most likely be) of radius r be in a volume of water V.

Total volume of vesicles = (4/3)N7rr3 eqn. 15 Total volume of water and vesicles = V + (4/3)N=r3 eqn. 16 The solution inside the Vesicles is made from a bulk solution of hygroscopic agent and water of concentration c say.

By diffusion and at equilibrium, the chemical potential of water inside the vesicle is equal to the chemical potential of water outside vesicle. Thus approximately:- Concentration of water inside vesicle = Concentration of water outside the vesicle eqn. 17 = > Total volume of water / Total volume of water and vesicles = c (approximately, neglect width of vesicle wall) = > V/(V+4/3Nxr3)=c Solving for V, the free volume of diffused water: v=(4/3)N#r (c/l-c) eqn. 18 Thus, Free Water = Total Volume of Vesicles x Constant Three specific embodiments and methods of making the core technology are now given by examples I.

II and Ill.

Example l Reference to figures 3 and 4. Figure 4 shows magnified section of particle shell membrane 1.

Step 1: A vessel containing mostly non-polar solvent 3 that has above it the hygroscopic solution 2 and above that a layer of detergent or surfactant or shell-wall-primer 5 which serves a dual process of forming the reverse micelles and being a primer for the semi-permeable membrane surface 1.

Step 2: On mixing the substances in the vessel a colloidal suspension in the non-polar solvent 3 is formed in which the reverse micelles are the hygroscopic solution 2 surrounded by the detergent or surfactant or shell-wall-primer 5 molecules. The detergent molecules form a repellent shield with the non-polar solvent 3 nearby so that the micelles don't coalesce.

Step 3: A polymerisation initiator is added or heat or light to the suspension so that some crosslinking 6 between the detergent or surfactant or shell-wall-primer 5 molecules occurs so that robust mutually repellent particles are formed 1, 2.

Step 4: The robust particles 1, 2 suspend themselves spontaneously in water when placed in a humid atmosphere by the action of the hygroscopic solution 2. This water can be decanted by enclosing the plurality of components 1, 2 in a filtration membrane 4 (figure 3).

Example II Reference to figure 5.

Starting with preexisting micro-encapsulation products of colloidal size in the form of a hollow shell, they are placed in a concentrated solution of the hygroscopic substance 2 so that it diffuses into the innards of the colloidal micro-spheres. The surface properties of the micro-spheres are then changed by chemical reaction, heat, electromagnetic radiation or nuclear radiation so that it is only permeable to water; the hygroscopic substance or substances stays within the shell 1. The mechanism of the surface transmutation can be by cross-linking of the shell material 6 (figure 4) or physical displacement of molecules or creation of channels within shell 1 leading to some kind of selective pore 7.

Example III Reference to figure 6.

The steps of encapsulation by polymer shell 1 can be done several times forming particles within particles, if very high rejection of hygroscopic substance or substances 2 is wanted and hence long filter life from the retention of the said solution. The semi-permeable shell membrane 1 being near ideal will not significantly affect the flux rate over the un-nested version described in figures 3. 4 and 5.

Specific embodiments of the core technology in configuration or applications is now discussed.

Example lV: Wet scrubber configuration Figure 7 shows a configuration of the filtration membrane 4 (figure 3) as long threads enclosing the component particles 1. 2. A fibrous mass 8 of these threads is placed in a pipe 12 to form a wet scrubber. The input air-stream 9 impinges on the fibrous mass 8 and exits 10 cleaned of soluble gases and particulates which are dissolved or suspended respectively in the output water stream 11 Example V: A Self-regenerative dehumidifier In a configuration similar to that depicted in figure 7, an air-stream 9 is dehumidified by the configuration 8, 12 with a conditioned air-stream 10 (soluble noxious smells and smoke removed) and outflow 11 exiting.The dehumidifier is self-regenerative because on vertical orientation, the potential energy of the condensed water runs out so no energy is needed to operate it. Also the dehumidifier flushes itself during operation lengthening the dehumidifier s life.

Example Vl: Low energy consumption water Durificationldesalination system Reference figure 7, 8, 9.

The first depiction is of flash conversion from a water bed since the operation of the device 8 is to deplete the atmosphere of water vapour it flashes' across. This action is assisted by the flashing chamber being under pressure. Device 8 (figure 7) is shown here as an annulus ring in a centrifuge (figure 8) to greatly assist separation of water from the device 8.

The second depiction shows a forced evaporation arrangement with an aerated water bed; vapour passes into the device 8.

Example Vll: An artificial soil Reference figure 2 An artificial soil can be formed by adding the component particles 1, 2 to soil or sand directly. The water attracting properties of the particles would render the soil self irrigating and more workable.

Example VIII: An air-snace heater Figures 10 shows humid air passing into the device configuration 8, 12. The heated output air is mixed 13 with cold room air.

Figure 11 shows an arrangement where the input air is kept entirely separate from the hot air exiting the device configuration by the intenention of a heat exchanger 14.

Example Ix: A source of electrical power Figure 12 shows the hot air leaving the device configuration 8. 12 impinging on a thermocouple which directly generates electrical power.

Example X: A source of rotational tower I Figure 13 shows the output hot vapour from the device configuration 8, 12 via a heat exchanger 14 heating a closed conventional turbine circuit that provides a source of rotational power.

Example Xl: A source of rotational power 11 Figure 14 shows how the gravitational potential energy of the condensed exit water powers a turbine directly.

Example XII: Svstcms other than water based Lowered vapour pressure by solute action in non-aqueous systems can be utilised with the same core technology 1. 2 (figure 2). The technique benefits from different liquid substances with: higher latent heat; a greater temperature range between phases; bctter liquid flow and closely relatcd better.

membrane separability.

Example XIII: Operation of first ordcr phase changing principle in a thermodvnamicallv closed, isolated environment Reference figure 15.

Consider a gas in a gravity field in a closed isolated universe at equilibrium. A strange way of looking at this equilibrium case is to consider that gas molecules with a vertically upwards component to their motion are doing work against gravity and that ones with a component vertically downwards are doing work on the gas system. The two work terms obviously cancel because the gas does not heat up no net energy has been supplied to the system. How is it possible that work is being done in a closed isolated system with obviously no matter or enthalpy transfer to it? A change of viewpoint is needed Consider a Second Law analysis of heat flow from two reservoirs at TA and TB Kelvin respectively, heat flow from Reservoir A to Reservoir B.The total change in entropy is: dST = ZQ / TA + BQ I TB eqn. 19 This implies: SQ = dST TATB I (TA - TB ) eqn. 20 Therefore our gas in a closed, isolated universe at equilibrium with TA = TB is capable of transferring limitless amounts of heat energy within itself at constant temperature. Heat energy continually cycles around the gas, though the amount of heat energy in transit is limited by the First Law - no energy is being created.

dU = #Q - #W eqn. 21 The gas is at a constant temperature so dU is zero (Eqn. 21 is The First Law ). Internal energy U is a measure of the temperature of the gas which is constant in our analysis (internal energy is also constant with the altitude of the gas). Thus by the First Law (eqn. 21) if dU is zero and 5Q is nonzero, then work SW is being done.

In general we have the possibility of doing work in constant entropv svstems where, overall, the change in entropy of the complete system is zero. I shall prove this.

Imagine within our total system we have n subsystems transferring heat 4 from system at temperature T, to system at temperature T,*, T l.

System 1 60 T (6ql) System 2 r T2 (X2)e System 3 ( T3(6q3)i ...- > System n ( Tn - < -- ôqn One can appreciate a flow of heat from system to system if T, > T but how could the cycle complete itself since Tn < T1? There has to be some kind of spontaneous tempcrature rise.

First Order Phase Chants allow limitless flow of heat from a low energy phase to a higher energy phase because the process occurs at constant temperature. This has already been proven by equations 20 and 21 for the case of a gas in a gravity field. Added to this the possibility of causing a spontaneous phase change from the high energy phase by say, an imbalance in chemical potential (hygroscopcity for example) and a sDontaneous temperature rise becomes possible.

One can view this enquiry in another manner, the Statistical Mechanics of the problem. Figure 15 shows the Maxwell-Boltzmann Distribution of speeds of thermal particles (behaving classically). First order phase changes can be viewed as a sorting Drocess since thermal particles with sufficient kinetic energy surmount a fixed potential energy barrier between the phases. The sorting of thermal particles for purposes of energy generation is called the Maxwell Demon Paradox and was always thought to be impossible.

Mechanisms other than first order phase changes exist as long as thermal particles have to surmount a fixed (or relatively unvarying) energy barrier. The key point is that the barrier must not become randornised by the random motions of the thermal particles themsleves. The sorting process might not be spontaneous as it is with first order phase changes but triggered or invoked so that the net supply of energy produced is greater than that required for triggering.

Claims (18)

1. According to the present invention (figure 2) there is provided a device consisting of a plurality of component robust enclosed semi-permeable shell particles 1, 2 made from a substance permeable only to water 1 whose component panicle innards are hygroscopic water soluble substance or substances 2 that spontaneously suspend themselves in a free volume of highly pure water permeated from within plurality of said components to without largely devoid of said hygroscopic substance or substances.

2. A device as claimed in Claim 1 whose component particles is enclosed by a filter membrane 4 (figure 3) such that the free water volume decants off to form highly pure water devoid of the plurality of said component particles.

3. A device as claimed in Claims 1 or 2 that spontaneously condenses water vapour to pure liquid water and spontaneously separates (figure 2) the liquid water from the device by the gravitational potential energy of the condensed liquid water (figure 1) flowing out.

4. A device as claimed in Claims 1, 2 or 3 whose said robust component particles' shell is made by the chemical polymerisation stabilisation of the reverse micelle particles (figure 4) formed in the emulsification of a non-polar liquid and detergent or surfactant or shell-wall-primer and hygroscopic solution by the chemical cross-linking of the detergent or surfactant or shell-wall- primer micelle wall 5 (figure 3 and 4) as hereinbefore described by example I.

5. A device as claimed in Claims 1, 2 or 3 whose said robust component particles are formed from prexisting microencapsulation products whose innards are hollow or substitutable, placed in a concentrated solution of the hygroscopic substance or substances so that it (hygroscopic solution 2) diffusers into the innards of said particles; the surface of the said particles is changed by chemical reaction, heat, electromagnetic radiation or nuclear radiation so that it is permeable only to water: the hygroscopic solution stays inside the particle (figure 5) as hereinbefore described by example II.

6. A device as claimed in Claims 1, 2, 3, 4 or 5 with a repeating process forming nested particles within particles (figure 6) as hereinbefore described by example III which can act as component particles described in Claim 1.

7. A device as claimed in Claims l, 2, 3, 4, 5 or 6 for use in a wet-scrubber (figure 7) to remove particulate matter or soluble gases from a damp air stream by a configuration of the device described in Claims 1, 2, 3, 4 or 5 as a fibrous mass 8 which allows the passage of air through it so that the particulate matter or soluble gases leave the device respectively suspended or dissolved in the exit water 11 as hereinbefore described by example IV.

8. A device as claimed in Claims 1, 2, 3, 4, 5, 6 or 7 for use as a self-regenerative dehumidifier as hereinbefore described by example V.

9. A device as claimed in Claims 1, 2, 3, 4, 5, 6 or 7 for use in a low energy consumption water purification/desalination system by the collection by: flashing from a water bed due to lowered vapour pressure above the water bed from the action of said device (figure 8) or forced evaporation by aeration of the water bed (figure 9); transport of vapour and subsequent condensation of water vapour by the said device as hereinbefore described by example VI.

10. A device as claimed in Claims 1, 2. 3. 4. 5, 6 or 7 for use as an artificial soil by the direct mixing of the component particles 1. 2 (figure 2) to soil or the fibrous mass 8 (figure 7) to form a self irrigating soil as hereinbefore described by example Vll.

CLAIMS (continued)

11. A device as claimed in Claims 1 2 3 4 5 6 or 7 in configuration with a mixing chamber 13 (figure 10) to mix the hot exit vapour with a damp input air stream or via a heat exchanger 14 (figure 11) to serve as an air space heater as hereinbefore described by example VIII.

12. A device as claimed in Claims 1 2 3 4 5 6 or 7 in configuration with a thermocouple assembly (figure 12) to generate electrical power as hereinbefore described by example IX.

13. A device as claimed in Claims 1 2 3 4 5 6 or 7 in configuration with a heat exchanger (figure 13) to power a turbine to provide a source of rotational power as hereinbefore described by example X.

14. A device as claimed in Claims 1 2 3 4 5 6 or 7 in a vertical configuration with a turbine (figure 14) powered by the gravitational potential energy of the exit water stream to generate rotational power as hereinbefore described by example XI.

15. A device as claimed in Claims 1,2,3,4,5,6,7,11,12,13 or 14 that spontaneously changes the phase by the first order of a substance other than water using the same mechanism of vapour pressure reduction in non-aqueous solution by solutes and semi-permeable membrane separation as hereinbefore described by example XII.

16. AdeviceasclaimedinClams 1,2,3,4,5,6,7,11,12,13,14 or 15 in operation as a heat pump or refrigerator.

17.AdeviceasclaimedinClaimsl 1, 2, 3, 4, 5, 6, 7, 11, 12, 13, 14 or 15 or by some other first order phase transition principle that is a first order phase changing catalyst.

18. A device as claimed in Claims 1, 2, 3, 4, 5, 6, 7, 11, 12, 13, 14, 15 or 16 that generates a spontaneous difference in temperature or any net expression of potential energy by the spontaneous or invoked or triggered first order phase change principle in a thermodyhamically closed, isolated environment pervaded by working substance as hereinbefore described by example XIII.

In the above Claims, a list of claims is declared by example: Claims 1, 2, 3 and so on; meaning Claims 1 or 2 or 3 and so on.