A PROCESS FOR PRODUCTION OF AMMONIA FROM INERT-FREE SYNTHESIS GAS IN MULTIPLE REACTION SYSTEMS

Abstract

In a process for the production of ammonia in at least two reaction systems, in which ammonia is produced from a portion of the synthesis gas in each of the systems with a part-stream being withdrawn, the make-up gas is essentially inert-free, the downstream system is at the same pressure or at a higher pressure than the upstream system and the make-up gas is sent once through a make-up gas (MUG) converter unit, the residual synthesis gas coming from the MUG converter unit is optionally pressurized to a higher pressure before being sent to an inert-free synthesis loop. This way, an economically attractive production of ammonia is feasible with synthesis gases not containing inerts.

Claims

1. A process for the production of ammonia in at least two reaction systems, in which ammonia is produced from a portion of the ammonia synthesis gas in each of the at least two systems with a part-stream being withdrawn, the make-up gas is essentially inert-free, the downstream system is at the same pressure or at a higher pressure than the upstream system, and the synthesis gas or make-up gas is sent once through a make-up gas (MUG) converter unit, and wherein the residual synthesis gas coming from the MUG converter unit is optionally pressurized to a higher pressure before being sent to an inert-free synthesis loop.

2. Process according to claim 1, wherein the make-up gas is coming from a nitrogen wash unit (NWU).

3. Process according to claim 1, wherein the first synthesis system operates as a once-through reactor system.

4. Process according to claim 1, wherein all of the at least two synthesis systems operate as once-through reactor systems with the exception of the last synthesis system.

5. Process according to claim 1, wherein the last synthesis system operates as a recycle loop system.

6. Process according to claim 1, wherein each synthesis system is separated from the next downstream synthesis system by one or more compression stages.

7. Process according to claim 1, wherein the downstream system is at the same pressure as the upstream system.

Description

EXAMPLE

[0032] Table 1 shows the key figures for a comparison of a 3000 MTPD ammonia plant based on an inert free synthesis loop, with a 3000 MTPD ammonia plant based on an inert free make-up gas and the make-up gas converter unit placed at three different pressure levels. It is shown that it is possible to produce at least 20% of the ammonia in the MUG unit.

[0033] Considering that the circulation flow can be used as an in-dicator for the synthesis loop equipment size, it is shown that an MUG unit reduces the size of the synthesis loop by at least 15%. This reduction in synthesis loop size repre-sents a possible capex saving, but more importantly it pro-vides a possibility to build a higher capacity ammonia plant, either in form of a new plant or as a capacity increase of an existing plant.

[0034] It should be noted that the numbers for production and circulation flow can be further optimized.

TABLE-US-00001 TABLE 1 base case: 3000 MTPD ammonia plant with inert-free synthesis loop MUG unit Synthesis loop MUG unit NH.sub.3 Synthesis loop pressure pressure production % of circulation flow kg/cm.sup.2 .Math. g kg/cm.sup.2 .Math. g total production % of base case 30 196 10 97 84 196 15 90 192 196 20 85