# US 10,870,584 B2 · Integrated process and plant for production of urea and UAS (urea-ammonium sulphate) mixtures

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- Number: US 10,870,584 B2
- Document ID: US10870584B2
- Status: Granted
- Kind: B2
- Application number: 16/461,279
- Filed: 2017-11-16
- Published: 2019-09-12
- Granted: 2020-12-22
- Earliest claimed: 2016-11-16
- Assignees: Saipem S.P.A.
- Applicants: SAIPEM S.p.A.
- Inventors: Lorenzo Bruno; Lino Carlessi
- Web page: https://patentgrep.com/patent/US10870584B2

## CPC

- C01C 1/242: Preparation from ammonia and sulfuric acid or sulfur trioxide
- B01D 47/06: Spray cleaning
- B01D 53/58: Ammonia
- B01D 53/78: with gas-liquid contact
- B01J 4/001: {Feed or outlet devices as such, e.g. feeding tubes}
- C07C 273/04: from carbon dioxide and ammonia
- C07C 273/16: Separation; Purification
- B01D 2247/04: Regenerating the washing fluid
- B01D 2247/101: using a cyclone
- B01J 2204/002: the feeding side being of particular interest
- B01J 2219/00006: Large-scale industrial plants
- Y02P 20/10: Process efficiency
- Y02P 20/141: Feedstock
- C01C: AMMONIA; CYANOGEN; COMPOUNDS THEREOF ({metal hydrides, monoborane, diborane or addition complexes thereof C01B6/00}; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; azides C01B21/08; {compounds other than ammonia or cyanogen, containing nitrogen, non-metals and optionally metals C01B21/082}; metal imides or amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; compounds containing silicon C01B33/00; compounds containing boron C01B35/00)
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

An integrated process for production of urea and urea-ammonium sulphate (“UAS”) comprises: a urea synthesis step carried out in a urea synthesis reactor; a recovery and concentration step, wherein a urea solution produced in the urea synthesis step is progressively concentrated in at least one recovery section and in a concentration section, recovering unreacted ammonia and carbon dioxide and water from said urea solution; a step of producing ammonium sulphate by reaction of sulphuric acid and ammonia in an ammonium sulphate production apparatus; a step of mixing said ammonium sulphate with concentrated urea coming from the concentration section to produce a UAS mixture; in the ammonium sulphate production step, at least a part of the ammonia is provided by at least one off-gas containing ammonia and recovered from the recovery and concentration step.

## Claims

### Claim 1

An integrated urea and urea-ammonium sulphate production process comprising:
a urea synthesis step carried out in a urea synthesis reactor;
a recovery and concentration step in which a urea solution produced in the urea synthesis step is progressively concentrated in at least one recovery section comprising at least a medium pressure recovery section and a low pressure recovery section, and in a concentration section located downstream of said at least one recovery section to recover unreacted ammonia and carbon dioxide and water from said urea solution;
an ammonium sulphate production step carried out in a plurality of stages in series and that occurs by reaction of sulphuric acid and ammonia in an ammonium sulphate production apparatus, wherein:
at least a part of the ammonia is from at least one off-gas containing unreacted ammonia from the urea solution produced in the urea synthesis step that is recovered from the recovery and concentration step,
the at least one off-gas is a medium pressure off-gas from a head outlet of a condenser of the medium pressure recovery section and is supplied to a first stage of the ammonium sulphate production step,
a first low pressure off-gas is supplied from a gas head outlet of a low pressure decomposer of the low pressure recovery section and is supplied to a second stage of the ammonium sulphate production step, and
a second low pressure off-gas is supplied from a head outlet of an absorption tower of the low pressure recovery section and is supplied to a third stage of the ammonium sulphate production step;
a mixing step of mixing said ammonium sulphate with concentrated urea from the concentration section to produce a urea-ammonium sulphate mixture; and
a urea finishing step in which the mixture of ammonium sulphate and urea is granulated or prilled.

### Claim 2 (depends on 1)

The integrated urea and urea-ammonium sulphate production process of claim 1, further comprising a supplying step of supplying the ammonium sulphate production apparatus with a solution of urea produced in the low pressure recovery section of the recovery and concentration step.

### Claim 3 (depends on 1)

The integrated urea and urea-ammonium sulphate production process of claim 1, wherein a urea solution is supplied from a bottom urea outlet of the low pressure decomposer of the low pressure recovery section and is supplied to a fourth stage of the ammonium sulphate production step.

### Claim 4 (depends on 1)

The integrated urea and urea-ammonium sulphate production process of claim 1, further comprising:
drawing gases, purified from the ammonia and containing methane, hydrogen and oxygen, from the ammonium sulphate production step;
burning said drawn gases; and
transferring heat generated by the burning of said gases to an air stream, wherein the transferred heat is at least one of: used for the urea finishing step and further transferred to a water stream to produce steam.

### Claim 5 (depends on 4)

The integrated urea and urea-ammonium sulphate production process of claim 4, further comprising:
a condensing step of condensing water from any gases combusted in the burning of said drawn gases; and
supplying the condensed water to the ammonium sulphate production step to control a temperature in said ammonium sulphate production step.

### Claim 6

An integrated urea and urea-ammonium sulphate production process comprising:
a urea synthesis step carried out in a urea synthesis reactor;
a recovery and concentration step in which a urea solution produced in the urea synthesis step is progressively concentrated in at least one recovery section comprising at least a medium pressure recovery section and a low pressure recovery section, and in a concentration section located downstream of said at least one recovery section to recover unreacted ammonia and carbon dioxide and water from said urea solution;
an ammonium sulphate production step that occurs by reaction of sulphuric acid and ammonia in an ammonium sulphate production apparatus, wherein at least a part of the ammonia is from at least one off-gas containing unreacted ammonia from the urea solution produced in the urea synthesis step that is recovered from the recovery and concentration step;
drawing gases, purified from the ammonia and containing methane, hydrogen and oxygen, from the ammonium sulphate production step;
burning said drawn gases;
transferring heat generated by the burning of said gases to an air stream, wherein the transferred heat is at least one of: used for a urea finishing step and further transferred to a water stream to produce steam;
a mixing step of mixing said ammonium sulphate with concentrated urea from the concentration section to produce a urea-ammonium sulphate mixture; and
the urea finishing step in which the mixture of ammonium sulphate and urea is granulated or prilled.

### Claim 7 (depends on 6)

The integrated urea and urea-ammonium sulphate production process of claim 6, further comprising a feeding step of feeding said ammonium sulphate production apparatus with the at least one off-gas recovered from at least one of the recovery sections.

### Claim 8 (depends on 6)

The integrated urea and urea-ammonium sulphate production process of claim 6, wherein the at least one off-gas is at least one of a medium pressure off-gas from the medium pressure recovery section and at least one low pressure off-gas from the low pressure recovery section.

### Claim 9 (depends on 6)

The integrated urea and urea-ammonium sulphate production process of claim 6, further comprising a supplying step of supplying the ammonium sulphate production apparatus with a solution of urea produced in the low pressure recovery section of the recovery and concentration step.

### Claim 10 (depends on 6)

The integrated urea and urea-ammonium sulphate production process of claim 6, wherein the ammonium sulphate production step is carried out in a plurality of stages in series.

### Claim 11 (depends on 10)

The integrated urea and urea-ammonium sulphate production process of claim 10, wherein said at least one off-gas is a medium pressure off-gas from a head outlet of a condenser of the medium pressure recovery section and is supplied to a first stage of the ammonium sulphate production step.

### Claim 12 (depends on 11)

The integrated urea and urea-ammonium sulphate production process of claim 11, wherein a first low pressure off-gas is supplied from a gas head outlet of a low pressure decomposer of the low pressure recovery section and is supplied to a second stage of the ammonium sulphate production step.

### Claim 13 (depends on 6)

The integrated urea and urea-ammonium sulphate production process of claim 6, further comprising:
a condensing step of condensing water from any gases combusted in the burning of said drawn gases; and
supplying the condensed water to the ammonium sulphate production step to control a temperature in said ammonium sulphate production step.