Integrated process for the production of formaldehyde-stabilized urea

Patent metadata

Field	Value
Publication number	US-10077235-B2
Application number	US-201515552063-A
Country	US
Kind code	B2
Filing date	Dec 18, 2015
Priority date	Feb 20, 2015
Publication date	Sep 18, 2018
Grant date	Sep 18, 2018

Abstract

The present disclosure relates to an integrated process for the production of formaldehyde-stabilized urea, starting with producing synthesis gas and including the preparation of methanol, ammonia, urea, and formaldehyde in amounts appropriate for the final product.

First claim

The invention claimed is:

1. A process for producing formaldehyde-stabilized urea comprising the steps of:
(a) generating a synthesis gas comprising hydrogen, nitrogen, carbon monoxide, carbon dioxide and steam in a synthesis gas generation unit, the synthesis gas generation unit comprising a synthesis gas generation stage and a water-gas shift stage;
(b) recovering carbon dioxide from the synthesis gas to form a carbon dioxide-depleted synthesis gas;
(c) directing the carbon dioxide-depleted synthesis gas to a methanol synthesis unit, synthesizing methanol from the carbon dioxide-depleted synthesis gas in the methanol synthesis unit and separately recovering the methanol and a methanol synthesis off-gas comprising nitrogen, hydrogen and residual carbon monoxide;
(d) directing the recovered methanol to a process-dedicated formaldehyde production unit and subjecting the recovered methanol to oxidation with air in the formaldehyde production unit to form formaldehyde;
(e) directing the methanol synthesis off-gas to a methanation reactor containing a methanation catalyst and subjecting the methanol synthesis off-gas to methanation in the methanation reactor to form an ammonia synthesis gas;
(f) directing the ammonia synthesis gas to an ammonia production unit, synthesizing ammonia from the ammonia synthesis gas in the ammonia production unit, and recovering the ammonia;
(g) reacting a portion of the ammonia and at least a portion of the recovered carbon dioxide stream in a urea production unit to form a urea stream; and
(h) stabilizing the urea by mixing the urea stream and a stabilizer prepared using the formaldehyde recovered from the formaldehyde production unit,
wherein a source of air is compressed in stages in a multistage compression unit and a first, low pressure portion of the compressed air is provided to the formaldehyde production unit for the oxidation of methanol and a second, higher pressure portion of the compressed air is provided to the synthesis gas generation unit.

2. The process according to claim 1 , wherein the synthesis gas generation stage is based on steam reforming of a hydrocarbon; or by the gasification of a carbonaceous feedstock.

3. The process according to claim 1 , wherein the synthesis gas is generated by one or more of adiabatic pre-reforming and/or primary reforming in a fired or gas-heated steam reformer or secondary or autothermal reforming with air or oxygen-enriched air.

4. The process according to claim 1 , wherein the water gas shift stage comprises one or more stage of high temperature shift, low temperature shift, medium temperature shift, isothermal shift or sour shift.

5. The process according to claim 1 wherein carbon dioxide removal is effected using absorption or adsorption.

6. The process according to claim 1 wherein the methanol synthesis is operated on a once-through, or a recycle basis in which unreacted gases, after condensate removal, are returned to the methanol synthesis unit in a loop.

7. The process according to claim 1 wherein the methanol synthesis is operated in a single stage at an inlet temperature in the range of from 200° C. to 320° C.

8. The process according to claim 1 wherein crude methanol recovered from the methanol synthesis stage is fed without purification to an oxidation reactor within the formaldehyde production unit.

9. The process according to claim 1 wherein the formaldehyde production unit comprises an oxidation reactor containing a bed of oxidation catalyst.

10. The process according to claim 1 wherein the formaldehyde production unit generates a formaldehyde vent gas which is recycled to one or more stages of (i) synthesis gas generation, (ii) carbon dioxide removal, (iii) methanol synthesis, or (iv) urea synthesis, either directly or after one or more stages of vent gas treatment in a vent-gas treatment unit.

11. The process according to claim 10 wherein the vent gas treatment unit comprises a gas-liquid separator that separates a nitrogen-rich off-gas from liquid methanol.

12. The process according to claim 10 wherein the formaldehyde vent gas is recycled directly without treatment to the methanol synthesis stage or indirectly after it has first passed to an emission control system comprising a catalytic combustor to convert the vent stream into carbon dioxide, nitrogen and steam.

13. The process according to claim 10 wherein the formaldehyde vent gas is recycled directly without treatment to the carbon dioxide removal stage or indirectly after it has first passed to an emission control system comprising a catalytic combustor to convert the vent stream into carbon dioxide, nitrogen and steam.

14. The process according to claim 10 wherein the formaldehyde vent gas is recycled after it has first passed to an emission control system comprising a catalytic combustor to convert the vent stream into carbon dioxide, nitrogen and steam to the urea synthesis stage.

15. The process according to claim 10 wherein the formaldehyde vent gas is recycled directly to the synthesis gas generation unit as a component of a fuel gas.

16. The process according to claim 7 wherein the methanol synthesis is operated in a single stage at an inlet temperature in the range of from 200° C. to 270° C.

17. The process according to claim 2 wherein the hydrocarbon is natural gas, naphtha, or a refinery off-gas.

18. The process according to claim 2 wherein the carbonaceous feedstock is coal or biomass.

19. The process according to claim 1 , wherein:
(a) the first portion of air is compressed to a pressure in the range of from 1.1 to 5 bar absolute before delivery to the formaldehyde production unit;
(b) and the second portion of air is compressed to a pressure in a range of from 10 to 80 bar absolute before air fed to the synthesis gas generation unit; or
(c) both (a) and (b).

20. The process according to claim 1 , wherein the proportion of compressed air fed to the formaldehyde production unit is in a range of from 1.5 to 15% by volume, of the total air fed to the process.

Assignees

• Johnson Matthey Plc

Inventors

• Erlandsson Ola
• Magnusson Andreas
• Pach John David
• Sheldon Daniel

Classifications

• C01B2203/0415

  Purification by absorption in liquids · CPC title

• C01B3/52

  by contacting with liquids; Regeneration of used liquids · CPC title

• C07C45/38

  being a primary hydroxyl group · CPC title

• C07C273/04 Primary

  from carbon dioxide and ammonia · CPC title

• C01B2203/06

  Integration with other chemical processes · CPC title