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Title:
METHOD AND SYSTEM FOR WATER VAPORIZATION
Document Type and Number:
WIPO Patent Application WO/2008/155775
Kind Code:
A2
Abstract:
A method for vaporization of liquid having an initial weight of W 0, using Electro Magnetic Radiation (EMR) of energy E 0, the method comprising: d) subjecting the liquid to the Electro Magnetic Radiation (EMR) yielding an initial vaporization ratio (I), wherein due to the EMR, the weight of the liquid W (t) decreases compared to the initial W 0, subsequently changing the vaporization ratio (II); and wherein the method further comprises: e) manipulating the weight of the liquid W (t) by adding liquid so as to equalize the value of W (t) with the initial W 0 so as to maintain the initial vaporization ratio β 0; or f) manipulating the energy of the EMR over time E (t) so as to maintain the initial vaporization ratio (III).

Inventors:
YANIV, Isaac (75 Yakinton Street, Haifa, 34972, IL)
LIVNEH, Ben-Zion (9071 E Mississippi Ave. #7A, Denver, Colorado, 80247, US)
LURIE, Walter (220 Garfield Street, Denver, Colorado, 80206, US)
Application Number:
IL2008/000846
Publication Date:
December 24, 2008
Filing Date:
June 22, 2008
Export Citation:
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Assignee:
MICROCOAL INC. (Suite 214, 5301 Limestone RoadCity of Wilmingto, Newcastle DE, 19808, US)
YANIV, Isaac (75 Yakinton Street, Haifa, 34972, IL)
LIVNEH, Ben-Zion (9071 E Mississippi Ave. #7A, Denver, Colorado, 80247, US)
LURIE, Walter (220 Garfield Street, Denver, Colorado, 80206, US)
International Classes:
B01B1/00; C10L9/00
Attorney, Agent or Firm:
REINHOLD COHN AND PARTNERS (P.O. Box 4060, Tel Aviv, 61040, IL)
Download PDF:
Claims:

CLAIMS:

1. A method for vaporization of a liquid having an initial weight of Wo, using Electro Magnetic Radiation (EMR) of energy Eo, said method comprising: a) subjecting said liquid to said Electro Magnetic Radiation (EMR) yielding

W an initial vaporization ratio β 0 cc — 9 - , wherein due to said EMR, the

weight of said liquid W( t ) decreases compared to the initial Wo,

W subsequently changing said vaporization ratio /? (0 oc -^- ; and wherein

E o said method further comprises: b) manipulating the weight of said liquid W^ by adding liquid so as to equalize the value of W Q with the initial Wo so as to maintain the initial vaporization ratio β 0 ; or c) manipulating the energy of said EMR over time E Q SO as to maintain the

W 1 , initial vaporization ratio β 0r (0

"C)

2. A method according to Claim 1, wherein step c is accomplished by providing an array of EMR sources having corresponding energies Eo, Ei, E 2 etc. in descending order, so that for each period of time and decreasing weight of the water Wo, Wi, W2 etc. thereof, the liquid is affected by a different EMR source such

3. A method according to Claim 1, wherein step c is accomplished by changing the power of said EMR as a function of time.

4. A method according to any one of Claims 1 to 3, wherein said method further comprises constant removal of vaporized water.

5. A method according to any one of Claims 1 to 4, wherein said liquid is contained within a solid carrier. 6. A method according to Claim 1, wherein the liquid is one of the group comprising water, water based solutions, and inorganic liquids such as Alcohol, Milk, and the like. 7. A method according to Claim 5, wherein said carrier is a mineral.

8. A method according to Claim 5, wherein said carrier is a plant, e.g. wood or grains of organic nature such as corn seeds, or the like.

9. A method according to Claim 5, wherein said method is an organism, e.g. beef.

10. A method according to any one of Claims 5 to 9, wherein said method is used for drying of said carrier by vaporization of liquid therefrom.

11. A method according to any one of the preceding Claims, wherein said liquid is water.

12. A system for vaporization of liquid by EMR, said system comprising a process chamber adapted for containing therewith a liquid to be vaporized of an initial weight Wo, an EMR source of energy Eo associated with said chamber and adapted to convey

said EMR thereto defining an initial vaporization ratio β ϋ ∞ — — and thereby reduce the

E (o) weight of said liquid with time W Q , said system further comprising at least a first control element adapted for maintaining said initial vaporization ratio β 0 by manipulating either the weight of liquid within said chamber Wp/ so

that/? (/) oc = β 0 or the amount of energy conveyed to said chamber by said EMR

E (t) so ϋia.tβ ω ∞ -^- = β 0 .

13. A system according to Claim 12, wherein said process chamber comprises a first inlet adapted for the introduction of liquid therein and a first outlet adapted for removal of product therefrom. 14. A system according to Claim 13, wherein said chamber is of pyramidal shape positioned such that its vertex constitutes a top end thereof and its base constitutes the bottom end thereof.

15. A system according to Claim 13, wherein said first inlet is located adjacent the top end of said process chamber and said outlet is located adjacent the bottom end thereof, whereby the liquid is displaced between said inlet and said outlet by virtue of gravitational forces.

16. A system according to Claim 12, wherein said process chamber is of pyramidal shape and of a horizontal configuration, whereby the inlet and outlet are positioned at a

similar height and elevation, and wherein the liquid is displaced within the chamber horizontally.

17. A system according to any one of Claims 13 to 16, wherein said system further comprises a withdrawal assembly adapted to remove said liquid from said process chamber through said outlet.

18. A system according to Claim 17, wherein said withdrawal assembly is in the form of a conveyer belt.

19. A system according to any one of Claims 12 to 18, wherein said process chamber is connected to an array of waveguides adapted to convey EMR thereto from several EMR sources.

20. A system according to Claim 19, wherein said EMR sources have the same energy E.

21. A system according to Claims 14 and 19, wherein the waveguides of said array are disposed vertically along the height of the pyramid, e.g. one above the other. 22. A system according to any one of Claims 13 to 20, wherein said control element which is in the form of a regulator associated with said inlet and adapted to determine the amount of liquid added to said chamber during operation of the system.

23. A system according to any one of Claims 12 to 22, wherein said process chamber is further formed with outlets vents adapted for the removal of vapors from asid process chamber.

24. A system according to Claim 23, wherein said removal of vapor is achieved by vacuum.

25. A system according to Claim 23, wherein said removal of vapor is achieved by intensified air or gas flow through said process chamber. 26. A system according to any one of Claims 23 to 25, wherein said process chamber comprises a divider adapted to prevent the liquid from entering or blocking said outlet vents.

27. A system according to Claims 26, wherein said divider is perforated.

28. A system according to any one of Claims 12 to 27, wherein said liquid is contained within a solid carrier.

29. A system according to Claim 28, wherein said carrier is a mineral.

30. A system according to Claim 28, wherein said carrier is a plant, e.g. wood.

31. A system according to Claim 28, wherein said method is an organism, e.g. beef.

32. A system according to any one of Claims 28 to 31, wherein said system is used for drying of said carrier by vaporization of liquid therefrom.

Description:

METHOD AND SYSTEM FOR WATER VAPORIZATION

FIELD OF THE INVENTION

This invention relates to the vaporization of water using electro-magnetic radiation (EMR), more particularly to methods for improving vaporization.

BACKGROUND OF THE INVENTION It is publicly known that water subjected to electro-magnetic radiation (EMR) undergoes a vaporization process in which water in the liquid phase is transformed into water vapor. The amount of vapor produced from a given weight of liquid water depends, inter alia, on the energy of the EMR it has been subjected to.

It is well known in the art that subjecting a given amount of water to EMR allows for the extraction of a predetermined maximal amount of water vapor, and that there exists a limit to the amount of water vapor extraction. This has been discussed extensively in numerous papers, often related to the removal of water from substances, among these papers one can highlight "Microwave drying of fine coal" by David P. Lindtroth and "Dewatering of fine coal slurries by selective heating with microwaves" by Aashish Kalra..

SUMMARY OF THE INVENTION

According to the present invention there is provided a method for vaporization of liquid having an initial weight of Wo, using Electro Magnetic Radiation (EMR) of energy Eo, said method comprising: a) subjecting said liquid to said Electro Magnetic Radiation (EMR) yielding

W an initial vaporization ratio β ϋ ∞ — - , wherein due to said EMR, the

weight of said liquid W^ decreases compared to the initial Wo,

subsequently changing said vaporization ratio /3L 1 ∞ — — ; and wherein

said method further comprises: b) manipulating the weight of said liquid W( t ) by adding liquid so as to equalize the value of W Q with the initial Wo so as to maintain the initial vaporization ratio β 0 ; or c) manipulating the energy of said EMR over time E Q SO as to maintain the initial vaporization ratio /? 0

This invention is based on the surprising observation that for a given amount of EMR energy (E) the rate of vaporization of a certain amount of water (W) is directly proportional to the amount of said water and inversely proportional to said energy of said EMR. If β is the vaporization ratio in Kg/KW-hr of EMR, then when applying a given microwave energy £On a certain amount of water W, the amount of water vapors produced will be lower per time unit if the initial amount of liquid water is smaller. It should be noted that in herinafter the following terms and units are used: • Power (P) in [kW]

• Energy (E) in [kW-hr], where E = P x t and t is time [sec]

• vaporization rate (β) in [kg/kW-hr]

• Weight (W) in [kg]

• Contained moisture in solids (a) in [%] Further to the above, a control volume may be defined containing the water in liquid phase exposed to the EMR therein. The control volume may further contain water vapor emitted therein under the effect of the EMR which may be removed therefrom as will be explained hereinafter.

In practical operation, an initial amount of water in the liquid phase having an initial weight Wo is exposed to EMR of an initial energy Eo, yielding a vaporization

W ratio of β 0 ∞ -^- . Under the effect of the EMR, a vaporization process of the liquid

E (o) water occurs in which the water transforms from a liquid phase to the vapor phase. This process gradually reduces the weight of the liquid water from its initial value of Wo to a new value of Wi, maintaining Wi< Wo- As a result, the initial EMR energy of E 0 is now

operating on a smaller weight of liquid water Wi and the vaporization ratio changes to

W lλλ β o '∞ —±- L < β o . It has been observed that when the vaporization ratio changes, the

E (o) amount of water vaporized during a time unit changes as well. Also, in the case of a large change in the vaporization ratio, arcing may occur. This is partially due to the increase in the amount of water in vapor phase which causes the gaseous portion of the control volume to become inductive.

Thus, it is desired to maintain a constant vaporization ratio, allowing for a constant vaporization rate of water per time unit, which will also prevent arcing. In order to maintain a constant vaporization ratio/? , either one of the above disclosed steps b and c may be performed. It should also be noted that throughout the vaporization process, water in the vapor phase is constantly removed from the control volume so as to prevent arcing.

With reference to step c, Reduction of said EMR energy in accordance with the weight of said water may also be achieved by using a series of different microwaves, each having a maximal power of its own. For example, there may be an array of EMR sources including a first tier of EMR sources adapted to operate at 7OkW, a second tier of EMR sources adapted to operate at 6OkW and so on. Once a certain amount of liquid water is vaporized under the effect of the first tier emitters, the liquid water may be exposed to the second tier of emitter. This process may continue until the desired amount of liquid water has vaporizes, and may require several tiers of emitters. The advantage of using an array of emitters relies on the fact that each emitter operates at its optimal maximal power. This is in contrast to reducing the power of the emitters gradually during the process, thus reducing the emitters' efficiency.

According to the present invention there may be further provided a system for vaporization of liquid by EMR, said system comprising a process chamber adapted for containing therewith a liquid to be vaporized of an initial weight Wo, an EMR source of energy Eo associated with said chamber and adapted to convey said EMR thereto

W (o) defining an initial vaporization ratio β 0 ∞ — — and thereby reduce the weight of said

E (o) liquid with time W^, said system further comprising at least a first control element adapted for maintaining said initial vaporization ratio β 0 by manipulating either the

weight of liquid within said chamber W (t / so that/? (r) ∞ = β Q or the amount of

W energy conveyed to said chamber by said EMR EM SO that β u , ∞ — — = β 0 .

The liquid used in said system may be exposed to EMR, either on its own, or as content in carriers such as moisture in solids (for example minerals), plants (for example wood), or organisms (for example beef), and other additional substances where subjecting said water to continuous EMR produces vaporization which reduces the amount of said water in said carrier with time allowing, inter alia, drying of said carrier.

The process chamber may comprise a first inlet adapted for the introduction of liquid therein and a first outlet adapted for removal of product therefrom. The chamber may further have a pyramid shape and may be positioned such that the vertex of the pyramid constitutes a top end thereof and the base of said pyramid constitutes the bottom end thereof. Said first inlet may be located adjacent the top end of said process chamber and said outlet located adjacent the bottom end thereof, whereby the liquid or liquid carrier may be displaced between said inlet and said outlet by virtue of gravitational forces. Alternatively, the process chamber may be of a horizontal configuration, whereby the inlet and outlet are positioned at a similar height and elevation, wherein the fossil fuel is displaced within the chamber horizontally.

The product carrier, e.g. fossil fuel, may be withdrawn from said first outlet using a conveyer belt or similar means. The operation speed of said conveyer belt may be variable and thereby control the operation throughput rate of the upgrading process taking place within said system.

The process chamber may be adapted for the connection of a waveguide thereto adapted to connect said chamber with said EMR source. However, the chamber may be also adapted to be connected to an array of waveguides adapted to convey EMR thereto from several EMR sources. The waveguides of said array may be disposed vertically along the height of the pyramid, e.g. one above the other.

The first inlet may be associated with said control element which may be in the form of a regulator adapted to determine the amount of liquid or liquid carrier which needs to be added to said chamber during operation of the system in order to maintain a desired initial weight, and a subsequent vaporization ratio. In order to maintain the initial vaporization ratio /? 0 , the control element may be adapted to introduce additional

water or water carrier W a< ω so as to maintain the initial amount of water Wg within the chamber. Alternatively or additionally, the pyramid shape of said process chamber may also be used as the control element as will be explained hereinafter.

During operation of the system, liquid or a liquid carrier having an initial weight of Wg is introduced into the process chamber through said first inlet and is exposed to

EMR of Eg from a first waveguide at a height Hj such that the vaporization ratio is

β 0 oc -^I . However, as a result of said EMR, the weight of the liquid is reduced to Wj.

E (o)

Thus, according to the previously disclosed observations, the new vaporization ratio is

W β'∞ — - which would subsequently cause less liquid to vaporize in a given time unit.

E 0 Due to the vertical disposition of the storage chamber, the liquid or liquid carrier is transformed downwards to a height H 2 where it is exposed to the same EMR of Eg only from a second waveguide. However, at this height the cross section of the pyramid is wider suggesting that the amount of liquid or carrier contained within a portion of the pyramid positioned at H 2 is greater than the amount contained at Hj. Thus, the shape of the pyramid functions as the control element regulating the operation of the system such that at every height, the amount of liquid subjected to the EMR is essentially the same.

The product carrier may be withdrawn from said first outlet using a conveyer belt or similar means. The operation speed of said conveyer belt may be variable and thereby control the operation throughput rate of the upgrading process taking place within said system.

According to another design variation, each of the EMR sources connected to the process chamber may have a different maximum energy Eg, Ej, E 2 , etc in descending order. Thus, during operation of the system, after a certain period of time,

W the vaporization ratio changes to β x ∞ — . However, since Wj<Wg, and correspondingly

E 1

W W Ej<Eg, the vaporization ratio is maintained β λ ∞ — = — = β 0 .

E 1 E 0

The chamber may further be formed with outlets vents adapted for the removal of vapors from the process chamber, which may facilitate in prevention of arcing. The removal of vapor from the process chamber may be achieved by vacuum or intensified air or gas flow through the process chamber. The process chamber may also comprise a

divider, which may be perforated, adapted to prevent the liquid or carrier from entering or blocking the outlet vents.

The optimization according to the present invention may be used in a variety of applications, especially for applications in which the removal of liquid water from a solid material is obtained by its vaporization. For example, one such application may be in the field of solid fossil fuel in which coal is dried using EMR to remove liquid water therefrom.

With respect to all of the above, it would be appreciated that the efficiency of the vaporization process does not depend solely on the vaporization ratio and may depend also on various properties of the system including such features as origin, particle shape, particle size, its Dielectric Constant, etc., as well as the chamber's geometry, material of construction, and the amount of liquid or carrier maintained at a predetermined level in order to prevent electrical arcing.

BRIEF DESCRIPTION OF THE DRAWINGS In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic block diagram of a liquid vaporization process in accordance with an embodiment of the process of the present invention; Fig. 2 is a different embodiment of the process of Fig. 1 ;

Figs. 3A to 3D are schematic views of a system and apparatus for removing water from fossil fuel implementing the method according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS In experiments performed on vaporization of water using EMR, the following results have been obtained, as shown in Table. 1A&1B (All measurements taken after first reaching boiling point of the water):

Table. IB

From Table IA it is clear that the water loss due to vaporization decreases over time while the liquid water is exposed to the same EMR power (in the present example

50 kW-hour) and the same energy. Table. IB is the same for a 30KW power. This demonstrates that there exists a direct relationship between the initial weight of the liquid water and the weight of vapor water removed by EMR vaporization. This relationship is contradictory to what a person skilled in the art would predict, and is all together counter-intuitive, was found to be of a great influence on the demise of efficiency in many systems implementing removal of liquid water by vaporization.

It was thus understood that an inventive concept should be created in order to perform an optimization relying on manipulating the ration between the initial weight of the water and the power of the EMR. Referring to Fig. 1, in experiments performed according to the one aspect of the present invention implementing the above concept, a tank 12 is connected to a source of EMR in the form of a MW emitter 14 via a waveguide 16.

In accordance with one experiment, the tank 12 is filled with water having an initial weight W 0 . The wave guide is adapted to transfer the EMR from the MW emitter 14 to the water filling the tank 12 and is adapted to output MW radiation of energy Eo- The water is first exposed to microwave radiation E 0 such that the vaporization

W ratio β 0 may be defined to be β 0 ∞ — - . The microwave radiation is emitted for a given

period of time to during which it is observed that a certain amount of liquid water turns

to vapor Vo which is removed from the tank 12, thus reducing the overall weight of the

W ' liquid water to Wo f =Wo-Vo. This yields a new vaporization ratio /? 0 '= £x — — < β 0 .

E o

Under this vaporization ratio, and in accordance with the previously disclosed observation, the amount of water to be vaporized in the following time period under the same energy Eo of microwave radiation would be less than Vo.

In order to maintain a constant weight of water equal to Wo, additional water W add is introduced into the tank 12 such that Wi= Wo'+ W a dd=W 0 . thus the yielded vaporization ratio is now/? ! ∞ — = — — = — = β 0 as desired.

L 0 L 0 L 0

Turning to Fig. 2, another method for optimizing the vaporization process in the presence of EMR is shown, in which the EMR supplied to the tank 12 by the microwave emitter 14 is constantly reduced. At the beginning of the process, the tank 12 contains liquid water of initial weight Wo and is subjected to EMR of a power Po and energy Eo for a period of time to. After said period of time, the amount of liquid water in the tank

W Yl is reduced to Wi, yielding a vaporization ratio of /? 0 'oc — L < β 0 . The power Po and

E o consequently the energy Eo are then reduced to Pi and Ei, yielding a new vaporization

W ratio of /J 1 oc — - = β 0 , thereby maintaining a constant vaporization ratio. Thus in the

E ι next period of time ti a similar amount of liquid water will be vaporized. The power P and the energy E of the microwave emitter 14 are constantly reduced in accordance with the weight of the liquid water in the chamber 12 thereby maintaining the constant ratio.

Turning to Figs. 3A to 3D, a system for drying of fossil fuel, generally designated 10, is shown implementing the concept of the present invention. In the system shown in Fig. 3A comprises a coal processing unit 20 and an external microwave unit 30 adapted to provide the EMR to the coal processing unit 20 through a series of wave-guides 32.

The EMR unit 30 comprises a main power supply 104, a transformer 105, a rectifier 106 and four magnetrons 107, e.g. of 75Kw power, adapted to provide EMR to the corresponding four waveguides 32. The waveguides 32 may also be connected to a source of inert gas, such as e.g. compressed nitrogen (N 2 ) cylinder, to supply the inert

in order to prevent the creation of fire. The inert may also be CO2 or any other gas suitable for the indicated purpose.

The coal processing unit 20 comprises a process chamber 40, a set of load cells 23, a feeder 24 and a discharge conveyer belt 26. The feeder 24 is adapted to allow coal of a given particle size to enter the process chamber 40, while diverting coal lumps exceeding the desired particle size directly to the discharge conveyer belt 26.

In operation, the coal processing unit 20 receives coal packed in sacks 102 from an external source 101, from where is filled to a receiving hopper 108. The hopper 108 is transported along a conveyer belt 109 until it reaches the load cells 23. The coal processing unit 20 further comprises a suction member 115 adapted to provide vacuum to the process chamber 40 as will be discussed with reference to Figs. 3 B and 3 C. The suction member is connected to a condenser 116 used in a cooling system 50 used for cooling of the entire system 10.

The cooling system 50 comprises a condensate receiver 117 with a condensate pump 118, the condensate receiver 117 being also connected to a vacuum pump 119 such that the cooling system 50 is adapted to provide central cooling water 120 for the entire system 10, and discharge condensate and air to the atmosphere.

Turning to Fig. 3 B, the process chamber 40 is shown comprising a main body 42 shaped in the form of a pyramid and having a feed end 42a at the top of the chamber and a discharge end 42b at its bottom. The body is further formed with a front panel 44a adapted for receiving a set of wave-guides therethrough, and a rear panel 44b fabricated of a perforated surface 45. The front and rear panels 44a, 44b define a cavity 46 within the body 42 adapted to contain therein solid fossil fuel to be processed therein.

The front panel 44a receives therethrough the set of wave-guides 32 which are disposed horizontally. The perforated surface 45 is fitted with dividers 48 forming four sections therebehind 48a to 48d. To each section there is attached an outlet vent 49 adapted for removing vapor and moisture from coal within the chamber 40. The outlet vents 49 are disposed vertically in accordance with the wave-guides 32.

In operation, coal lumps having an initial moisture of X% (calculated by the weight of the fossil fuel entire lump and the weight of the water contained in the said lump) are introduced into the load cells 23 and are transferred to the feeder 24 where size sorting of the coal lumps is performed, during which coal lumps of up to a certain

size, for example 3 inches, are allowed to enter the chamber 40. Coal lumps of a larger size are diverted directly to the discharge conveyer belt 26.

Upon being introduced to the chamber 40, the coal lumps are exposed to EMR incoming through the set of wave-guides from the microwave unit 30. Due to the shape of 42 of the chamber 40, and due to particle size reduction occurring during the process, the amount of solid fossil fuel varies in accordance with the height of the chamber 40, such that at a higher level, a lesser amount of solid fossil fuel is exposed to EMR than that at a lower level. During the exposure to EMR liquid water contained inside the lumps of the solid fossil fuel is released in a vapor phase. The vapor is withdrawn from the inside of the chamber and passes through the perforated surface 45 by means of a vacuum, or airing of the chamber 40. After passing through the perforated surface 45, the vapor is removed by the outlet vents 49. Thus, the perforated surface 45 allows the removal of vapor therethrough, while at the same time preventing the coal lumps from blocking the outlet vents 49. The removal of vapor from the chamber facilitates the prevention of arcing, a phenomenon in which during subjection to EMR the vapor causes the air to become inductive of the EMR ionizing the air and causing a short circuit. Overcoming such short circuit requires shutting down the entire system for a certain period of time which slows down the process and is undesired. Upon exit from the product end 42b of the chamber 40, the upgraded fossil fuel lumps are removed by the discharge conveyer belt.

Thus, when the coal lumps are first introduced to the chamber 40 they are exposed to EMR of power P. This in turn causes vaporization of a certain amount of water from the solid fossil fuel and subsequently a decrease in its moisture content X% which decreases the overall weight of the liquid water in the system. Therefore, in accordance with the observations previously disclosed, when the solid fossil fuel lumps reach a lower level along the chamber, the same EMR will affect a smaller weight of liquid water, and subsequently become less efficient. The pyramidal design of the chamber 40 and the reduction in particle size occurring in the process elegantly provide a solution for this efficiency decrease, since at a lower level of the chamber, a greater amount of fossil fuel is processed, and therefore the overall weight of the water on that level remains practically the same, whereby β remains practically the same. Furthermore, in order to preserve the above ratio, there is no need in changing the

power P of the microwave unit and it may operate at full power throughout the operation the entire system 10.

With further reference to Figs. 3C and 3D, a design variation of the chamber 40 is shown in which the number of wave-guides changes along the height of the chamber 40 allowing better control of the amount of microwave exposure inside the chamber 40.

In Fig. 3D there are show a schematic of the EMR stages, a side view of the chamber, a front view of the chamber and an enlarged view of detail A of the chamber 40.

The chamber comprises six waveguides 140 arranged such that EMR is directed to the processing chamber in three stages denoted Sl, S2, and S3 respectively. At the first stage Sl three waveguides 140 of power 100Kw each are used, at the second stage S2, two waveguides 140 of power 150Kw each are used and at the third stage S3, one waveguide 140 of power 300Kw is used. Thus, in every stage, the sum of power of all waveguides amounts to 300Kw.

It is also observed that the cross-section of the waveguides 140 of the first and third stage Sl, S3 are of smaller dimension than the cross section of the waveguides of the second stage S2. One of the reasons for changing the diameter of the waveguide cross section is to allow the waveguide 140 to provide EMR to the entire cross-section of the chamber 40, i.e. allow it to cover the majority of the processing chamber 40 at the height level thereof. Each waveguide 140 is fitted at an end thereof with a EMR transparent shield

160 adapted to allow EMR from the waveguides 140 to pass into the chamber 40, yet preventing coal from entering the waveguides 140. hi addition, the processing chamber 40 is constantly provided with ambient air 150 adapted to sweep water vapor to the vacuum chamber. It is further observed that the vacuum chamber is separated from the processing chamber 40 by a screen 170 formed of slats 172 adapted to allow water vapor to be sucked into the vacuum chamber while preventing coal particles from doing the same.

With reference to Fig. 3 C, it is observed that the processing chamber 40 is of a width W 1 after the top, feed end 42a, and gradually widens towards the bottom thereof at an angle a until it reaches a width W 2 . Then, it proceeds to become narrower towards the bottom, outlet end thereof 42b having width W 3 , satisfying Wi<W 3 <W 2 . Thus, the processing chamber 40 may be divided into a first, major portion 144a axially spanning between the feed end 42a of width W 1 and the wide most cross section of W 2

of the processing chamber 40, and a second, minor portion 144b spanning between the cross section of width W 2 of the processing chamber 40, to the outlet end 42b of width W 3 . .

The first major portion 144a has an axial length of H 3 , and the minor portion 144b has an axial length of H 5 +H 6 .

It is further observed that within the first, major portion 144a there are disposed four waveguides 140 axially spaced at distances X 1 between one and other, arranged such that the top most waveguide is at an axial distance of H 2 from the feed end 40a. Also disposed within the major portion 144a an array of 3 ambient air channels 152 axially spaced therebetween at a distance X 2 «Xi, such that between each two waveguides 140 there is disposed an ambient air channel 152.

The entire axial span of the processing chamber 40 is generally greater than the widths W 1 , W 2 and W 3 of various cross sections of the processing chamber 40.

In addition to the above, two comparison experiments for solid dewatering have been performed, a first using a common method for EMR dewatering, and a second implementing the concept according to the present invention as follows:

General Features:

• A Microwave Generator supplied by Amtek Inc., USA of Maximum net output energy of 75kW-hr at 915 MHz; • A Polypropylene (PP) Box having the dimension of 42cmx42cmx42cm and having a perforated bottom in order to allow for air flow and/or vacuum to suck the moisture/liquid water/water vapors away from the chamber simultaneously;

• Initial vacuum of 3.2" of H 2 O (low vacuum);

Raw Material:

• PRB (Powder River Basin) Coal - Black Thunder mine which was screened to 2"xO";

• Initial Coal Moisture 27%; • Coal initial Temperature of 6OF;

• Initial Coal sample weight of 3 OKg. Testing work:

• Filling up the PP with Coal;

Measuring initial weight, temperature and moisture of the coal;

Exposing Coal to the microwave radiation for a predetermined time period (In Table 2);

Getting out the PP Box with the Coal for measurement of weight loss temperature and final moisture;

Total interval for measurement is of about 2 minutes.

Table 2: Test No. 1

Table. 2A

10 Initial Water Weight: 30x0.27 = 8.1 kg Final water Weight: 24.3x0.093 = 2.25 kg Total Water weight loss = 5.85 kg * 43.87kg/60kW-hr » β = 0.73 kg/kw-hr

15

Test No. 2

Table. 2B

Initial Water weight: 30x0.27 = 8.1 kg

20 Final water weight: 23.35x0.061 = 1.42 kg Total water weight loss: 6.68kg * 50.1kg/62kw-hr

*Beta= 0.808 kg/kw-hr

The overall improvement in efficiency of coal drying is presented in table. 3 below:

Table. 3