Process and relating apparatus to make pure hydrogen from a syngas originated from wastes gasification

Abstract

A process and apparatus for producing pure hydrogen from a syngas generated by the high temperature gasification of municipal, agricultural or industrial derived wastes. The process is able to make pure hydrogen to be further reacted with nitrogen to make ammonia and urea.

Claims

1. A process for making hydrogen without any emission of nitrogen and sulphur, comprising the following steps: gasification in a gasification reactor of a carbon-matrix waste to produce raw syngas, wherein the carbon matrix waste is selected from the group consisting of municipal waste and refuse derived fuel; pretreatment (210) of the raw syngas to remove particulates, metals, chlorine, and NH.sub.3 compounds, to produce a pretreated syngas; conversion (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, wherein the conversion comprises a high temperature sour shift reaction (223) where the HCN, COS and CO are converted through the following reactions:
COS+H.sub.2O ⇄CO.sub.2+H.sub.2S
CO+H.sub.2O .Math.CO.sub.2+H.sub.2
2 HCN+2H.sub.2O.fwdarw.N.sub.2+2 CO+3H.sub.2; removal (230) where H.sub.2S is removed from the pretreated syngas and then transformed into elementary S; and purification (240) where CO.sub.2 is removed from the pretreated syngas via a cryogenic unit or an amine unit, and pure hydrogen is produced by a pressure swing absorption unit, wherein the method further comprises, wherein the H.sub.2S level in the raw syngas by adding waste containing S into the gasification reactor, wherein the increasing is to maintain a concentration high enough to carry out the high temperature sour shift reaction (223).

2. The process according to claim 1 wherein the pretreatment (210) comprises: an acid scrubbing (211); an alkaline scrubbing of the syngas (212); 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 wherein liquid streams are pumped from one subsection to the another one, and disposed in the liquid stream concentrator (214) where contaminants are removed as solid form and water is recycled back.

3. The process according to claim 1 wherein the conversion comprises sequentially, prior to the high temperature sour shift reaction (223): syngas compression (221); and further dechlorination and demetallization procedure.

4. The process according to claim 1 wherein the removal (230) comprises: an absorbing section (231) where H.sub.2S is removed from the syngas and transferred into an 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 removal step (230).

5. The process according to claim 1 wherein the purification (240) comprises sequentially: final further H.sub.2S removal (241) to lower down the sulphur content of a 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. The process according to claim 5 wherein in the cryogenic unit (242) all the CO.sub.2 in the syngas is removed and stored in liquid form.

7. The process according to claim 5 wherein a raw hydrogen stream incoming from the removal step (240) is further purified by a multi-bed PSA to achieve purity higher than 99,9%.

8. The process according to 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. The process according to claim 1, wherein Hydrogen is used to make urea throughout the following steps: ammonia synthesis where H.sub.2, incoming from purification step (240), and N.sub.2 are reacted to make ammonia; urea synthesis where ammonia and CO.sub.2 are reacting to make urea.

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

11. The process according to 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.

12. The process according to 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

(1) 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:

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

(3) 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.

(4) FIG. 4 is an overall block diagram for making urea with H2 obtained by the process of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(5) 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.

(6) An overview of one embodiment according to the invention is shown in FIG. 1.

(7) 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.

(8) 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.

(9) Section 220 consists of: Syngas compression, 221 A dechlorination and demetallization section, 222 A high temperature sour shift, section 223, where COS, CO and other components are converted through the following 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

(10) 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.

(11) Section 230 consists of 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 A sulphur recovery section, where S is separated by the liquor and leaves the unit

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

(13) 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.

(14) 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.

(15) 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.