Solar receiver installation with pressurized heat transfer fluid system

Abstract

A solar receiver heat transfer pressurized fluid system includes: a pressure relief valve; and a trapping device for separating liquid droplets from a pressurized gas released by the pressure relief valve and to capture the liquid droplets. The trapping device includes: a horizontal pipe; a liquid trap element extending from the horizontal pipe for catching separated liquid droplets; and a vertical exhaust pipe connected to the horizontal pipe substantially in a perpendicular manner and having an open end for discharging in atmosphere the pressurized gas released by the pressure relief valve. The horizontal pipe includes a first connection means for removably connecting at a first end to the pressure relief valve and a second connection means for removably connecting at a second end to the liquid trap element. The vertical exhaust pipe is connected to the horizontal pipe between the first end removably connectable to the pressure relief valve.

Claims

1. A solar receiver heat transfer pressurized fluid system, comprising: a pressure relief valve; and a trapping device configured to separate liquid droplets from a pressurized gas released by the pressure relief valve and to capture the liquid droplets, the trapping device comprising: a horizontal pipe; a liquid trap element extending from the horizontal pipe and configured to catch separated liquid droplets; and a vertical exhaust pipe connected to the horizontal pipe substantially in a perpendicular manner and having an open end configured to discharge in atmosphere the pressurized gas released by the pressure relief valve, wherein the horizontal pipe comprises a first connection means configured to removably connect at a first end to the pressure relief valve and a second connection means configured to removably connect at a second end to the liquid trap element, and wherein the vertical exhaust pipe is connected to the horizontal pipe between the first end removably connectable to the pressure relief valve and the second end removably connectable to the liquid trap element.

2. The system according to claim 1, wherein the vertical exhaust pipe forms a bend to the horizontal pipe.

3. The system according to claim 1, wherein the vertical exhaust pipe has a length of at least 0.5 m.

4. The system according to claim 1, wherein a ratio of a length of the horizontal pipe to a length of the liquid trap element is between 2 and 6.

5. The system according to claim 1, wherein a ratio of length/diameter of the liquid trap element is between 1.5 and 6.

6. The system according to claim 1, wherein the liquid trap element comprises a cap enclosing a wire mesh configured to capture the separated liquid droplets.

7. The system according to claim 6, wherein the wire mesh is comprised of stainless steel, with a wire diameter of between 0.15 mm to 0.35 mm, and with a packing density of between 100 and 250 kg/m.sup.3.

8. The system according to claim 7, wherein the wire mesh is comprised of 304L- or 316L-grade stainless steel.

9. The system according to claim 6, wherein the wire mesh is maintained inside the cap by a wire mesh holder.

10. The system according to claim 1, wherein the heat transfer fluid comprises a molten salt or a mixture of molten salts, liquid sodium, or thermal oil, and wherein the pressurized gas comprises air.

11. A concentrated solar power plant or CSP, comprising: the solar receiver heat transfer pressurized fluid system according to claim 1.

12. The concentrated solar power plant or CSP according to claim 11, wherein the concentrated solar power plant or CSP comprises a solar receptors-supporting tower concentrated solar power plant or CSP.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. Other features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following:

(2) FIG. 1 is a perspective view of one embodiment for a salt trapping device according to the invention, which is connected to a pressure relief valve.

(3) FIG. 2 is an elevation view of the salt trapping device of FIG. 1, connected to the pressure relief valve.

(4) FIG. 3 represents a detailed cross-sectional view of the salt tap element of the salt trapping device according to the invention;

(5) FIGS. 4 and 5 illustrate results of numeric simulations where molten salt particles are injected randomly onto the input line of a computational domain modeling the salt trap of the present invention (cases B and E respectively corresponding to a number of input droplets equal to 100). The speed of the air flow is indicated in three regions of the salt trap device.

(6) FIG. 6 shows a concentrated solar power plant or CSP / solar-receptors supporting tower.

DETAILED DESCRIPTION

(7) In an embodiment, the present invention provides a trapping system for avoiding ejection of hot molten salt flow or droplets in the atmosphere.

(8) In an embodiment, the system is designed to catch at least all molten salt droplets that cannot be cooled down to 50° C. after 200 meter in free fall, in the case of a CSP solar receiver tower plant.

(9) In an embodiment, the present invention also provides a system for catching molten salt droplets of at least 0.25 mm diameter.

(10) A first aspect of the present invention relates to a solar receiver heat transfer pressurized fluid system equipped with a relief valve and a trapping device for separating liquid droplets from a pressurized gas released by the pressure relief valve and for capturing said liquid droplets, said trapping device comprising, in use:

(11) a horizontal pipe;

(12) a liquid trap element extending from the horizontal pipe and capable to catch the separated liquid droplets;

(13) a vertical exhaust pipe connected to the horizontal pipe substantially in a perpendicular manner and having an open end for discharging in the atmosphere the gas released by the pressure relief valve;

(14) the horizontal pipe being provided by a first connection means for removably connecting at a first end to the pressure relief valve and by a second connection means for removably connecting at a second end to the liquid trap element, the vertical exhaust pipe being connected to the horizontal pipe between the first end removably connectable to the pressure relief valve and the second end removably connectable to the liquid trap element.

(15) According to further embodiments of the invention, the solar receiver heat transfer pressurized fluid system is further limited by one of the following features or by a suitable combination thereof:

(16) the vertical exhaust pipe is connected forming a bend to the horizontal pipe;

(17) the vertical exhaust pipe has a length of at least 0.5 m;

(18) the ratio of the length of the horizontal pipe by the length of the liquid trap element is comprised between 2 and 6;

(19) the ratio length/diameter of the liquid trap element is comprised between 1.5 and 6;

(20) the liquid trap element comprises a cap enclosing a wire mesh capable to capture the separated liquid droplets;

(21) the wire mesh is made of stainless steel, with a wire diameter comprised between 0.15 mm to 0.35 mm, and with a packing density comprised between 100 and 250 kg/m.sup.3;

(22) the wire mesh is made of 304L- or 316L-grade stainless steel;

(23) the wire mesh is maintained inside the cap by a wire mesh holder;

(24) the heat transfer fluid is a molten salt or a mixture of molten salts, liquid sodium or thermal oil and wherein the pressurized gas is air.

(25) A second aspect of the present invention concerns a concentrated solar power plant or CSP, preferably of the solar receptors-supporting tower type, comprising a solar receiver heat transfer pressurized fluid system as described above.

(26) The present invention relates to a solar receiver heat transfer pressurized fluid system equipped with molten salt trapping device as illustrated by FIG. 1. The salt trapping device comprises a salt trap element 1 extending from a horizontal pipe 4 at one end thereof, and a vertical exhaust pipe 3 freely open to the atmosphere and connected substantially perpendicularly to the horizontal pipe 4. The salt trapping device is designed to be connected to a pressure relief valve 2, by attaching the horizontal pipe 4 to the pressure relief valve 2 but at its end opposite the salt trap element 1.

(27) Preferably the salt trap element 1 is composed of a cap 7 having in its interior a wire mesh 5 maintained by a wire mesh holder 6. The wire mesh 5 is preferably made of stainless steel, preferably 304L or 316L (molybdenum stainless steel), with a wire diameter comprised between 0.15 mm to 0.35 mm, and preferably of 0.28 mm, as well as with a packing density comprised between 100 and 250 kg/m.sup.3, and preferably of 140 kg/m.sup.3. The other parts of the device are also preferably made of stainless steel.

(28) The working principle of the trapping device is based on a quick change of the air flow direction. The mixed flow of molten salt droplets and pressurized air comes from the pressure relief valve 2 at the entrance of the molten salt droplets trapping system. Thanks to the difference of density between the two fluids, the molten salt droplets will go by inertia into the horizontal pipe 4 and will be separated from the air flow which is released in the vertical pipe 3. The molten salt droplets will then be captured in the wire mesh 5 of the salt trap element 1. The air will flow into the atmosphere at the open end of the exhaust pipe 3.

(29) For an optimal running, the length of the horizontal pipe 4 is comprised between 2 and 3 m.

(30) Preferably, the minimal length of the vertical exhaust pipe 3 is comprised between 0.5 and 1 m.

(31) In a preferred embodiment, the salt trap element 1 has a length comprised between 0.75 and 1.50 m and a diameter comprised between 25 and 50 cm.

EXAMPLE

(32) FIGS. 4 and 5 illustrate results of different simulations performed for the device according to the present invention. In these simulations, molten salt particles are assumed injected randomly onto the input line of a computational domain modeling the salt trap (the simulation conditions have also been subject to certain geometric and physical assumptions). In this digital model, the injection of the molten salt particles takes place when the flow of air is established in stationary mode. Particles are subject to pressure forces (drag), gravity and inertia forces. They have an initial velocity equal to the speed of the air at the entry of the domain and a direction aligned with the axis of the pipe (supposed to be about 309 m/s).

(33) The size of the molten salt particles is comprised between 0.25 and 6 mm diameter. The density and the number of particles has been varied according to 6 different configurations, as shown in Table 1.

(34) TABLE-US-00001 TABLE 1 Injection A B C D E F Temperature [° C.] 242 242 242 494 494 494 Density [kg/m.sup.3] 1936 1936 1936 1776 1776 1776 Quantity [—] 20 100 200 20 100 200

(35) The properties of the air at the outlet of the valve are shown in Table 2, and the thermal properties of the molten salt are shown in Table 3.

(36) TABLE-US-00002 TABLE 2 Air Temperature [° C.] 242.1 Viscosity Sutherland's law Speed [m/s] 310 Prandtl No. 0.72

(37) TABLE-US-00003 TABLE 3 T inlet T outlet 242° C. 494° C. Density [kg/m.sup.3] 1936 1776

(38) The results are illustrated in FIGS. 4 and 5, respectively representing cases B and E, with 100 molten salt droplets. The results show that the density and number of the droplets has only a marginal influence on the working of the trapping device. It is the inertia of the droplets (310 m/s) which gives them a rectilinear trajectory. The latter is very little influenced by the air flow lines and by the gravity.

(39) While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments.

(40) The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.

REFERENCE SYMBOLS

(41) 1 Salt trap element 2 Pressure relief valve 3 Vertical exhaust pipe 4 Horizontal pipe 5 Wire mesh 6 Wire mesh holder 7 Cap 8A, 8B Connection means 10 Concentrated solar power plant/Solar-receptors supporting tower