A PROCESS AND RELATING APPARATUS TO MAKE PURE HYDROGEN FROM A SYNGAS ORIGINATED FROM WASTES GASIFICATION

Abstract

A raw syngas coming from HT gasification of organic wastes, once cooled in a proper heat recovery boiler or in a quencher is treated in a scrubbing section where, by adding an acidic solution followed by alkaline solution and by a WESP, particulate and chlorine compounds are removed and the syngas is ready for conversion, after its compression. In the conversion step CO is converted into C02 and H2 by adding steam; H2S is reduced to sulphur in a solid form, C02 is removed via cryogenic unit or an amine unit and pure H2 is produced.

Claims

1. A process for making Hydrogen from a syngas produced from carbon-matrix waste gasification, without any emission of nitrogen and sulphur, comprising the following steps: a pretreatment step (210) to remove from the raw syngas particulate and the bulk of metals, chlorine and NH.sub.3 compounds a conversion step (220) where HCN, CO and COS present in the pretreated syngas are converted into N.sub.2, CO.sub.2 and H.sub.2S in presence of H.sub.2S; a removal step (230) where H.sub.2S is removed from syngas and then transformed in elementary S; a purification step (240) where CO.sub.2 is removed via a cryogenic unit or amine step, and pure Hydrogen is produced by a PSA unit, wherein the H.sub.2S level into the syngas is controlled by eventually adding waste containing S into the gasification reactor.

2. A process according to claim 1 where the pretreatment step comprises the following subsection: an acid scrubbing (211) a alcaline scrubbing of the syngas (212) and a treatment with a Wet Electrostatic Precipitator (213) and a liquid stream concentrator (214) wherein the syngas is entering the pretreatment at temperature ranging from 50-200 C. and where the liquid streams are pumped from one subsection to the another one, and disposed in (214) where the contaminants are removed as solid form and water is recycled back.

3. A process according to the claim 1 where the conversion step comprises sequentially: a syngas compression (221) a dechlorination and demetallization procedure (221); an high/low temperature sour shift reaction (223) where HCN, COS and CO are converted through the following reactions:
COS+H.sub.2OCO.sub.2+H.sub.2S
CO+H.sub.2.Math.CO.sub.2+H.sub.2
2HCN+2H.sub.2O.fwdarw.N.sub.2+2CO+3H.sub.2.

4. A process according to the claim 1 where the removal step (230) comprises: an absorbing section (231) where H.sub.2S is removed from the syngas and transferred into the absorbing liquor; a regeneration section (232) where absorbing liquor is regenerated and H.sub.2S transformed in S; and a sulphur recovery section (233) where S is separated by the liquor and leaves the unit.

5. A process according to the claim 1 where the final H.sub.2 purification step (240) comprises sequentially: final H.sub.2S removal t (241) to lower down the sulphur content of the stream leaving the absorbing section (231); a cryogenic unit or amine unit (242) for removing CO.sub.2. and a PSA for final purification of Hydrogen.

6. A process according to claim 5 where in the cryogenic unit (242) all the CO2 in the syngas is removed and stored in liquid form.

7. A process according to claim 5 wherein raw hydrogen stream is further purified by a multi-bed PSA to achieve purity higher than 99.9%.

8. A process according to each of claim 1 wherein the pure hydrogen is produced in the range of pressure of 15-30 barg, having compressed the syngas at a pressure of 20-35 barg in the purification process.

9. A process according to claim 1, where Hydrogen is used to make urea throughout the following steps: Ammonia synthesis where pure H.sub.2 and N.sub.2 are reacted to make ammonia; Urea synthesis where ammonia and CO.sub.2 are reacting to make urea.

10. A process according to claim 1, where CO.sub.2 in a liquid form leaving the subsection (242) is pumped to the urea synthesis reactor.

11. A process according to claim 1 wherein the carbon matrix waste is selected from a solid municipal waste, a derived waste fuel as RDF, agricultural waste, urban and/or industrial sludge, biomass, a solid chemical waste and combinations thereof and where the waste composition is such to maintain a H.sub.2S concentration in the syngas high enough to carry a sour CO shift.

12. A process and apparatus according to claim 1 wherein the H.sub.2 required to minimize or avoid any CO.sub.2 emission is obtained by water electrolysis.

13. A process and apparatus according to claim 12 where extra H.sub.2 required to minimize or avoid any CO.sub.2 emission is produced by electrolysis only when excess of electricity is available from the grid.

14. An apparatus for make pure hydrogen from a syngas originated from wastes gasification, without any emission of nitrogen and sulphur, comprising: a pretreatment section (210) to remove from the raw syngas particulate and the bulk of metals, chlorine and NH.sub.3 compounds a conversion section (220) where HCN, CO and COS present in the pretreated syngas are converted into HCN, CO.sub.2 and H.sub.2S in presence of H.sub.2S; a removal unit (230) where H.sub.2S is removed from syngas and then transformed in S; a purification section (240) where CO.sub.2 is removed via a cryogenic unit or amin unit and pure Hydrogen is produced by a PSA unit, and means to control the H.sub.2S level into the syngas by eventually adding waste containing S into the gasification reactor.

15. Apparatus according to claim 14 further comprising: means to carry out a pre-treatment process to purify the raw syngas comprising: an acid scrubbing column (211); an alkaline scrubbing column (212); a Wet Electrostatic precipitator (WESP) (213); means to pump the liquid stream from one unit to the another one up to a liquid stream concentrator (214) wherein contaminants are removed as solid form and water is recycled back; means (221) to perform a compression of the syngas (101) coming from the WESP (231); means (222) for dechlorination and demetallization the compressed syngas; a high/low temperature sour shift reactors (223), where COS and CO present in the syngas are converted through the reactions:
COS+H.sub.2O CO.sub.2+H.sub.2S
CO+H.sub.2.Math.CO.sub.2+H.sub.2
2HCN+2H.sub.2O.fwdarw.N.sub.2+2CO+3H.sub.2 an absorbing unit (231) where H.sub.2S is removed from the syngas and transferred into the absorbing liquor; a regeneration unit (232) where absorbing liquor is regenerated and H.sub.2S transformed in S; a sulphur recovery unit (233) where S is separated by the liquor and leaves the unit; while the stream leaving the absorbing unit (231) enters to a final sulphur removal unit (241) to lower down the sulphur content; said apparatus being further provided a cryogenic unit (242) to remove CO.sub.2 and a Pressure Swing Absorption (PSA) Unit (243) for final purification of Hydrogen.

16. An apparatus according to claim 13 wherein the PSA unit is a multi-bed PSA to achieve purity higher than 99.9%.

17. An apparatus according to claim 12 further comprising a water electrolyzer to produce the H.sub.2 required to minimize or avoid any CO.sub.2 emission.

18. A process according to each of claim 2 wherein the pure hydrogen is produced in the range of pressure of 15-30 barg, having compressed the syngas at a pressure of 20-35 barg in the purification process.

19. A process according to each of claim 3 wherein the pure hydrogen is produced in the range of pressure of 15-30 barg, having compressed the syngas at a pressure of 20-35 barg in the purification process.

20. A process according to each of claim 4 wherein the pure hydrogen is produced in the range of pressure of 15-30 barg, having compressed the syngas at a pressure of 20-35 barg in the purification process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] These and other aspects, features and advantages of which embodiments of the invention are capable of, will be apparent and elucidated from the following description of the embodiments of the present invention, reference being made to the accompanying drawings in which:

[0031] FIG. 1 is a schematic representation of the entire process 200 for making pure H.sub.2 from the syngas produced by wastes gasification

[0032] FIGS. 2 and 3 are schematic representations of the syngas treatment, according to FIG. 1, where the unit 200, has been divided into the four main sections 210-220 and 230,240, respectively.

[0033] FIG. 4 is an overall block diagram for making urea with H2 obtained by the process of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0034] Specific embodiments of the invention are described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be constructed as limited to the embodiments set for herein. Rather, these embodiments are provided so that this disclosure will be through and complete, and will fully convey the scope of the invention to those skilled in the art.

[0035] An overview of one embodiment according to the invention is shown in FIG. 1.

[0036] A raw syngas coming from HT gasification of organic wastes, once cooled in a proper heat recovery boiler or in a quencher is treated in a scrubbing section where, by adding an acidic solution followed by alkaline solution and by a WESP, particulate and chlorine compounds are removed and the syngas is ready for conversion, after its compression. In the conversion step CO is converted into CO.sub.2 and H.sub.2 by adding steam; H.sub.2S is reduced to sulphur in a solid form, CO.sub.2 is removed via cryogenic unit or an amine unit and pure H.sub.2 is produced.

[0037] A more detailed description of unit 200 is given through FIG. 2. The pretreatment section, 210, the CO conversion section, 220, the H.sub.2S removal section 230 and the CO.sub.2 removal and H.sub.2 purification section, 240. The subsystem 210 consists of four subunits, the acid scrubbing column, 211, the alcaline scrubbing column, 212, the Wet Electrostatic precipitator (WESP) 213 and liquid stream concentrator, 214. Liquid streams are pumped from one subsection to the another one, and disposed in 214 where contaminants are removed as solid form and water is recycled back.

[0038] Section 220 consists of: [0039] Syngas compression, 221 [0040] A dechlorination and demetallization section, 222 [0041] A high temperature sour shift, section 223, where COS, CO and other components are converted through the following reactions:

COS+H.sub.2OCO.sub.2+H.sub.2S

CO+H.sub.2.Math.CO.sub.2+H.sub.2

2HCN+2H.sub.2O.fwdarw.N.sub.2+2CO+3H.sub.2

[0042] The 230 section may consist of a process or unit, being the content of sulphur in the wastes quite minimal where H.sub.2S is converted into elementary sulphur and separated from the syngas.

[0043] Section 230 consists of [0044] An absorbing section, 231 where H.sub.2S is removed from the syngas and transferred into the absorbing liquor [0045] A regeneration section, 232 where absorbing liquor is regenerated and H.sub.2S transformed in S

[0046] A sulphur recovery section, where S is separated by the liquor and leaves the unit

[0047] Stream leaving the H.sub.2S removal section, 230, enters the section 240 for the final H2 purification consisting of: [0048] Final sulphur removal, 241 to lower down the sulphur content [0049] Cryogenic unit or amine unit 242, for removing CO.sub.2 [0050] PSA unit, 243 for making pure H.sub.2

[0051] In the cryogenic unit, 242 all the CO.sub.2 in the syngas is removed and stored in a liquid form. The cryogenic separation of the CO.sub.2 is required to purify the CO.sub.2 before its use. The off-gas, produced by the unit may be recycled into the gasifier or disposed throughout the combustion chamber of a steam boiler.

[0052] Raw hydrogen stream, is further purified by a multi-bed PSA to achieve purity higher than 99.9%. Off-gas, will be recycled to the gasifier or routed to the boiler house.

[0053] Pure hydrogen is produced in the range of pressure of 15-30 barg, having compressed the syngas at a pressure of 20-35 barg in section 200.