Discussion on the production of refined ammonium in caustic soda plants

I’m currently learning about this; it seems to be an important issue that must be taken into consideration when dealing with double-alkali compounds. It also appears that using ammonium chloride to produce compound fertilizers is a good option! Studying*…

The method we use here is to send it to be turned into compound fertilizer.

Original company’s ammonium nitrate production process: 1. First washing: In the first-washing tank, the AI supplied from the crystallization stage and the wet ammonium brought in from the reserve tank are mixed together to form a slurry that meets the required specifications; this slurry is then pumped into the first-washing thickener using a first-washing pump. II. Second washing: The filtrate in the filtrate tank is sent to the ammonium chloride cold crystallization vessel; the wet ammonium obtained after separation by the first-stage centrifuge is fed into the second-washing mixing tank, where it is washed with recycled mother liquor, and the resulting slurry is then sent to the second-washing thickener ； It overflows into the secondary washing mixing tank; the thick slurry is separated by the secondary washing centrifuge and then sent to the dry ammonium furnace for drying, while the filtrate returns to the secondary washing mixing tank. When the sulfate concentration in the circulating mother liquor, as well as the salt content, reaches a certain level, it is necessary to remove the sulfate or replace the mother liquor (via batch operations). Third, thickening and centrifugal separation of water: The slurry from the first-thickening unit enters the first-centrifuge through a discharge pipe; the wet ammonium produced by this separation process is pushed out by a push plate and then fed into the second-stirring tank via a discharge chute or a wet ammonium conveyor belt, while the filtrate returns to the first-filtrate tank. The slurry from the second washing thickener enters the second washing centrifuge through a discharge pipe; the separated wet ammonium is sent to a wet ammonium conveyor belt via a discharge chute, and then transported to a drying furnace for drying. The filtrate from the second washing centrifuge goes into the second washing tank. IV. Prepare by adding a loosening agent and drying

Below is a brief overview of the 450,000 tons per year ammonium chloride production unit. In this unit, 10,000 tons per year of industrial ammonium chloride is produced; the ammonia mother liquor I originating from the alkali production process flows automatically into the tank for ammonia mother liquor I. From there, it is pumped through the ammonia mother liquor I cooler and the mother liquor heat exchanger, where it exchanges heat with water and mother liquor II to cool down. After that, it enters a collection tank, where it mixes with the recycled semi-mother liquor II coming from the liquid ammonia evaporation external cooler. Together, they then enter the central tube of the cold crystallization reactor. As they move upward through the ammonium chloride crystal bed, the supersaturation of ammonium chloride gradually decreases, allowing the crystals to grow larger. The cryocondenser is equipped with three axial flow pumps; two of them are operated to enable a semi-II cycle, thereby creating supersaturation in the liquid ammonia evaporation external cooler. The supersaturation in the crystal bed is then removed through the crystallizer, allowing the ammonium chloride crystals in the bed to grow larger. Considering the need to produce industrial ammonium chloride, the crystallizer is equipped with three systems: one system for the coalescing and washing process, and the other two systems for the reverse material removal process. In the combined material washing process, the overflow from the top of the cold crystallization vessel goes to the semi-II washing unit, while the slurry obtained is sent to the cold crystallization thickening unit. In the salting-out crystallizer, an axial flow pump is used to circulate the mother liquor; this liquor mixes with the solid raw salt added to it inside the central tube and then flows upward through the crystal bed. The raw salt is continuously dissolved, and the centrifugal effect creates a supersaturation of ammonium chloride. As this supersaturation gradually decreases, the ammonium chloride crystals in the crystal bed grow larger. In the salting-out crystallizer operating in forward flow, the slurry is taken out to the washer, while in those operating in reverse flow, the slurry is sent to the salting-out thickener. The overflow from both the salting-out thickener and the washer is directed to tank II for storing the mother liquor. The slurry from the washer is sent to the cold precipitation thickener; the slurry thinned by the salt precipitation thickener is also sent to the cold precipitation crystallizer via an inverse flow pump. The overflow from the cold precipitation thickener goes to the filtrate tank, while the thinned slurry is sent to the centrifugal ammonium filtration machine. The filtrate flows into the ammonium filtrate tank and is then pumped into the salt precipitation crystallizer by an ammonium filtrate pump. Mother liquor II is pumped to the mother liquor heat exchanger where it is heated before being sent to the caustic soda production process. The sediment at the bottom of Tank II of Mother Liquor II is pumped into the salting-out crystallizer by the Mother Liquor II sediment pump. The refrigerant – liquid ammonia – delivered from the freezing process is sent to #1 Ammonia Liquid Separator, from where it flows by gravity to the liquid ammonia evaporation external cooler. After exchanging heat with the mother liquor, the liquid ammonia circulates naturally back to #1 Ammonia Liquid Separator due to differences in density. The liquid ammonia evaporates within #1 Ammonia Liquid Separator, and the gaseous ammonia, after having its droplets separated in #2 Ammonia Liquid Separator, is sent back to the freezing process, where it is pressurized into liquid ammonia before being sent once again to #1 Ammonia Liquid Separator. The liquid ammonia separated by the 2# ammonia liquid separator is returned to the ammonia evaporation external cooler. The scaling inside the tubes of the liquid ammonia evaporation external cooler is cleaned in rotation using hot ammonia mother liquor I. The methods for producing industrial ammonium chloride include the recrystallization method, and the method of taking high-quality ammonium chloride out of a cold crystallization vessel for thickening, filtration, and drying. The slurry taken out of the cold crystallization vessel using an alkaline unit is sent to a cold thickening device; the overflow from this thickening device goes to the filtrate tank. The thickened slurry is then sent to a centrifuge, and the wet ammonium chloride resulting from centrifugation is conveyed to the dry ammonium furnace via a belt conveyor and an electromagnetic vibrating feeder. The filtrate flows into the ammonium filtration tank, and then is pumped by a filtrate pump into the salting-out crystallizer. The wet ammonium chloride sent to the dry ammonium furnace comes into contact with the wet ammonium chloride using heated air as a boiling medium and heat carrier, thereby removing the moisture from it. The dried ammonium chloride is then sent from the outlet of the dry ammonium furnace to the ammonium chloride storage bin, where the finished product is packaged. The dried and boiling medium is sent to the air heater by a blower; after being indirectly heated by steam, it is fed into the dry ammonium furnace. The exhaust gas from this process undergoes dust removal in a bag filter before being discharged through an exhaust fan. The solid material separated by the bag filter is fed into the ammonium nitrate silo. The medium for heating the air is low-pressure steam at 1.9 Mpa, and the condensate water after heat exchange enters the low-pressure steam network at 0.3 Mpa after flashing.

Table of Ammonium Chloride Consumption Quotas (per 1 ton of finished product)
Serial Number | Name | Calculation Basis | Unit | Consumption Quota | Remarks
--- | --- | --- | --- | --- | ---
I. Main Raw Materials | 1. Ammonium Chloride 100% NH4Cl | t | 1.05 | |
II. Auxiliary Materials | 1. Packaging Bags: 50 kg of ammonium chloride per bag | pieces | 20.5 | Includes losses |
III. Energy | 2. Desalinated Water | t | 0.1 | |
| | 3. Electricity | kWh | ~57.5 | |
| | 4. Steam at 2.0 MPa(A) | t | 0.30 | |
| | 6. Condensate Water at 0.4 MPa(A) | t | -0.3 | Sent back to the boiler room |
| | 7. Compressed Air at 0.8 MPa(A) | Nm3 | 748 | |

Main equipment for 10,000 tons/year industrial ammonium chloride production:
(1) Fluidized bed dryer: Specifications: φ350/φ500×～16000 mm; Material: C.S; Capacity: 75 tons/unit per day; Number of units: 1.
(2) Carbonization tower: Specifications: φ1400×～22500 mm; Material: C.S; Capacity: 75 tons/unit per day; Number of units: 2 (1 in operation, 1 for cleaning).
(3) CO2 compressor: Specifications: 4L-40/2-3.2; Material: assembled components; Capacity: 75 tons/unit per day; Number of units: 2 (1 in operation, 1 as backup).
(4) Clarification tank: Specifications: φ8000×～7000 mm; Material: C.S; Capacity: 75 tons/unit per day; Number of units: 1.
(5) Centrifuge: Specifications: φ1250×625 mm; Material: S.S; Capacity: 75 tons/unit per day; Number of units: 2 (1 in operation, 1 as backup)

The production ratio of caustic soda to ammonium chloride is generally considered to be 1:1 to 1:1.1, depending on the specific details of the process and the scale of the installation. Many domestic plants using the double-salt process have industrial ammonium chloride production facilities, but their scale is small, generally ranging from 10,000 to 20,000 tons per year.

I have a flowchart here, but I haven’t yet learned how to upload it as an attachment. ⊙﹏⊙b Sweat. I’ll keep learning* and upload it later