Process and apparatus for separation, removal, and purification of solid carbon outcoming from a hydrogen production reactor by methane and/or hydrocarbons cracking with low CO

1 . An apparatus for continuously separating, removing and purifying a solid residue, resulting from the conversion of hydrocarbons into carbon and hydrogen, from a homogeneous phase having a different density contained in a cracking reactor with which said solid residue is not soluble, said apparatus comprising:

a reactor provided with a shell on which at least one outlet nozzle is provided in order to facilitate the release of the gas/solid stream produced inside said reactor and provided with a barrier of hollow cylindrical shape, made of a refractory material, coaxial with the shell of the reactor adapted to divide the volume of said reactor into a calm annular zone and an inner reaction zone, said barrier being provided with at least one weir at the top and at least one opening at the bottom to allow the homogeneous phase having a different density to pass from the calm annular zone to the inner reaction zone;

at least one distributor placed at the bottom of the reactor for an injection of hydrocarbon into the reactor;

an impeller operable by a shaft driven by a motor placed outside the reactor; and

an exit pipe connecting said reactor to a system configured to separate the solid phase from the gaseous phase, the system comprising:

at least one primary separator,

at least one collection chamber downstream of the at least one primary separator,

at least one intermediate transfer tank downstream of the at least one collection chamber and provided with a MP vent valve connected to a medium pressure circuit,

at least one final storage tank downstream of the at least one intermediate transfer tank and provided with a BP vent valve connected to a low pressure circuit, a second atmospheric ATM vent valve connected to a vent, and a bottom valve configured to discharge solids,

at least one primary valve placed between the collection chamber and the intermediate tank configured to transfer solids from said collection chamber to the intermediate tank,

at least one secondary valve placed between the intermediate tank and the storage tank configured to transfer solids from the intermediate tank to the storage tank, and

a control and automation system for opening the valves by a PLC.

2 . The apparatus according to claim 1 , wherein said homogeneous phase is a melting bath of molten metal and/or molten salt bath.

3 . The apparatus according to claim 2 , wherein said homogeneous phase comprises a catalyst.

4 . The apparatus according to claim 2 , wherein said melting bath has a lower density in the reaction zone, said lower density being induced by the bubbling of the reagents introduced into the reactor by said distributor and also by the bubbling of the reaction products, and a higher density in the annular zone, due to both the separation of the reaction products from the molten mass and also the local cooling of the melting bath due to the distance from the reaction zone.

5 . The apparatus according to claim 2 , wherein the transfer of the molten metal and/or molten salt from the reaction zone to the calm annular zone occurs through one or more special openings present in said barrier and is due to the difference in density between the two zones, said difference in density allowing the layering and collection of the solid carbon on the free surface of the melting bath at the calm annular zone, said solid carbon being produced by the reaction and being insoluble with the melting bath.

6 . The apparatus according to claim 5 , wherein the impeller allows improving the movement of the solid accumulated on the free surface from the central zone to the annular zone and to avoid accumulations of coal above the weir.

7 . The apparatus according to claim 2 , wherein said outlet nozzle from the reactor is angularly offset with respect to a discharge point of the weir to allow the separation of the reaction products from the melting bath during the travel.

8 . The apparatus according to claim 1 , wherein the shell is provided with refractory coating.

9 . The apparatus according to claim 1 , wherein the motor driving the shaft connected to the impeller is of the magnetic coupling type.

10 . The apparatus according to claim 1 , wherein said annular zone of the reactor is connected to said exit pipe configured to discharge the gas/solid stream produced inside the reactor.

11 . The apparatus according to claim 10 , wherein said exit pipe is made of a refractory material.

12 . The apparatus according to claim 10 , wherein said exit pipe is made of a metal material.

13 . The apparatus according to claim 10 , wherein said exit pipe is further provided with a cooling system in order to reduce the temperature of the gas/solid stream from about 1000-1200° C. about 800-900° C.

14 . The apparatus according to claim 1 , wherein said exit pipe is connected to said primary separator, said primary separator being a cyclone separator in which the gas/solid stream is separated and in which a crude gas, mainly consisting of crude hydrogen and methane, is released from the top of said primary separator, while the solids are layered in the lower part of said separator, said solids comprising an amount of absorbed hydrocarbon gases.

15 . The apparatus according to claim 14 , wherein said primary separator has a bottom provided with vibrators in order to prevent dust agglomeration and solid outlet obstruction phenomena.

16 . The apparatus according to claim 14 , wherein said primary separator is further provided with a cooling system.

17 . The apparatus according to claim 1 , wherein said primary separator has a bottom connected to the collection chamber and the collection chamber is provided with a cooling system, and wherein the passage of the solid from the bottom of the primary separator to said collection chamber occurs by gravity.

18 . The apparatus according to claim 1 , wherein said primary valve is an automatic primary valve, said automatic primary valve regulating the passage of the solid from upstream, at higher pressure, to downstream, at lower pressure.

19 . The apparatus according to claim 18 , wherein said MP vent valve is an automatic MP vent valve, said automatic MP vent valve being able to allow the depressurization of said intermediate tank and thus the desorption of the solid-retained gases.

20 . The apparatus according to claim 19 , wherein pressure in said medium pressure circuit is between 4-8 barg.

21 . The apparatus according to claim 18 , wherein said intermediate tank is provided with a coal cooling system.

22 . The apparatus according to claim 1 , wherein the secondary valve is an automatic secondary valve, said automatic secondary valve regulating the passage of the solids from upstream, at higher pressure, to downstream, at lower pressure.

23 . The apparatus according to claim 22 , wherein the low pressure circuit is configured to allow the depressurization of said storage tank and thus the desorption of solid-retained gases.

24 . The apparatus according to claim 1 , wherein gases desorbed by the MP vent valve and gases desorbed by the BP vent valve are recycled to the reactor after compression.

25 . A method utilizing the apparatus according to claim 1 , the method comprising, the following steps occurring at consecutive times:

producing the gas/solid stream comprising carbon and H 2 by cracking reaction inside the reactor;

separating the solid residue by means of insolubility of the solid residue with respect to a melting bath of the homogenous phase;

separating the gas by density difference from the solid residue to produce the solid phase;

removing the solid phase from the reactor by means of external transport due to the gaseous phase exiting the reactor; and

purifying the carbon by means of gradual pressure lowering and gradual cooling.

26 . The method according to claim 25 , wherein movement of solid residue from a discharge point of the weir to the outlet nozzle occurs by dragging, exploiting the movement of the melting bath.

27 . The method according to claim 25 , wherein said purification step occurs by sequentially opening the valves including the following steps:

step 1: primary valve opening,

cycle start: primary valve opening, all remaining valves closed, and

cycle end: all valves closing;

step 2:

cycle start: MP vent valve opening, all remaining valves closed, and

cycle end: all valves closing;

step 3:

cycle start: secondary valve opening, all remaining valves closed, and

cycle end: all valves closing;

step 4:

cycle start: MP vent valve and BP vent valve opening, all remaining valves closed, and

cycle end: all valves closing;

step 5:

cycle start: ATM vent valve opening, all remaining valves closed, and

cycle end: all valve closing;

step 6:

cycle start: bottom valve opening, all remaining valves closed;

cycle end: all valves closing; and

wherein at the end of step 6 the entire sequence starts again from step 1.

28 . The method according to claim 25 , wherein the pressure of said low pressure circuit is between 0.1-1 barg.

29 . The method according to claim 25 , wherein crude gas outcoming from the primary separator is sent to a purification unit which allows the separation between the produced hydrogen from any recyclable gaseous hydrocarbon components inside the reactor after compression.

30 . The method according to claim 29 , wherein the crude gas incoming to the purification unit is pre-treated in a further separation step aimed to the elimination of any solid particles still present in the gaseous phase.