Ann: Minbos Signs EPCM Contract for Cabinda Phosphate Project, page-88

I asked Chat GPT how to make P4 from phosphate.

Needless to say it is a very complicated procedure, and I can see how a partner with the expertise & capital, would be required.
I noticed in the DFS the fuel price used was US 27c a litre. If fuel is so cheap I presume gas is as well?
Because any process that requires temperatures above 1,000 deg usually requires gas & lots of it (such as the Lithium hydroxide plants)
If gas is also cheap in Angola, it would be a no brainer to locate such a plant here along with the cheap power which could be used for the later stage of heating to 300-400 deg

Converting phosphate into yellow phosphorus, which is represented by the chemical formula P4, involves a multistep process. Here's a general outline of the steps involved:

1. Preparation of Calcium Phosphate: Start with a source of phosphate, such as calcium phosphate (Ca3(PO4)2). This compound is commonly found in mineral deposits like rock phosphate. If necessary, the calcium phosphate can be extracted and purified.

2. Production of Calcium Phosphide: Calcium phosphide (Ca3P2) is prepared by reacting the calcium phosphate with carbon (usually in the form of coke or charcoal) in an electric furnace. The reaction occurs at high temperatures (around 1,200-1,300°C) and in an environment devoid of oxygen:

   Ca3(PO4)2 + 6 C → 2 Ca3P2 + 6 CO

   The carbon reduces the phosphate to phosphide, and carbon monoxide (CO) is produced as a byproduct.

3. Conversion of Calcium Phosphide to Phosphine: Calcium phosphide is then reacted with water (H2O) or dilute acid (such as hydrochloric acid, HCl) to generate phosphine gas (PH3):

   Ca3P2 + 6 H2O → 3 Ca(OH)2 + 2 PH3

   Alternatively:

   Ca3P2 + 6 HCl → 3 CaCl2 + 2 PH3

   Phosphine is a toxic and flammable gas, so appropriate precautions should be taken when handling it.

4. Preparation of Yellow Phosphorus: The phosphine gas obtained in the previous step is further processed to obtain yellow phosphorus. The typical method involves passing the phosphine gas through a hot tube or furnace made of refractory material (such as quartz) at high temperatures (around 300-400°C):

   4 PH3 → P4 + 6 H2

   The phosphine decomposes into yellow phosphorus (P4) and hydrogen gas (H2).

It's worth noting that the production of yellow phosphorus from phosphate is an industrial process carried out in specialized facilities due to the hazardous nature of the chemicals involved. The steps mentioned here provide a general overview, but the specific conditions and equipment used may vary depending on the scale and requirements of the production process.