Magnesium Nitrate

Desalination Reject Valorization (Oman Case: 100 MLD Intake)

1. Chemical Principle & Ammonia Mass Balance

In seawater reverse osmosis (SWRO) brine, magnesium is primarily present as dissolved magnesium chloride (MgCl2).

As noted, 4 moles of ammonia (NH3) are utilized per mole of magnesium ion (Mg):

  • 2 moles of ammonia are converted into nitrate (NO3) to bind the magnesium. This yields the target product Magnesium Nitrate [Mg(NO3)2], produced as commercial fertilizer flakes in the hexahydrate form.
  • 2 moles of ammonia bind directly with the displaced chloride ions (Cl) from the magnesium chloride. This yields the co-product Ammonium Chloride (NH4Cl), a high-demand nitrogen fertilizer.

2. Daily Mass Balance (Basis: Gulf of Oman Seawater)

  • Seawater Intake: 100 MLD (100,000 cubic meters per day)
  • Clean Potable Water via Primary RO: 40 MLD (40,000 cubic meters per day)
  • Brine Reject to HPDD Platform: 60 MLD (60,000 cubic meters per day)
  • Dissolved Magnesium in Brine: approx. 130 tonnes of pure magnesium per day

Daily Production & Chemical Inputs:

  • Additional Clean Water via HPDD: approx. 60 MLD (60,000 cubic meters per day)
  • Magnesium Nitrate Flake (fertilizer grade, hexahydrate): approx. 1,370 tonnes per day
  • Ammonium Chloride (dry solid fertilizer): approx. 570 tonnes per day
  • Ammonia Input Requirement (NH3 equivalent): approx. 365 tonnes per day
  • Refined Commercial Salt (NaCl): approx. 2,500 tonnes per day
  • Gypsum (Calcium Sulfate): approx. 130 tonnes per day

3. Process Block Flow Diagram

4. How Salts Precipitate as Solids & 60 MLD Clean Water is Recovered

Elimination of Boilers, MEE, and Cooling Towers:

Conventional thermal plants rely on massive steam boilers, multi-effect evaporators (MEE), and cooling towers that dissipate heat into the air. The HPDD platform operates through direct volumetric mechanical compression:

  1. Vapor rising from the brine is compressed directly using linear hydraulic displacement.

  2. Latent heat released when the vapor condenses is transferred directly back into incoming pressurized brine via internal heat exchangers.

  3. Because thermal energy is recycled inside a closed loop rather than dumped to cooling water, virtually the entire 60 MLD water volume condenses out as pure, high-grade distillate.

Fractional Salt Separation (Clean Solid Output):

Salts do not drop out as an unusable mixed sludge; they are separated in distinct stages governed by solubility differences:

  1. Calcium Sulfate (Gypsum): Drops out first upon initial temperature elevation and is filtered out immediately, preventing pipe scaling downstream.

  2. Magnesium Nitrate: Dosing nitric acid and ammonia reacts selectively with the magnesium ions. Under dedicated thermal concentration, it crystallizes cleanly as pure fertilizer flakes.

  3. Sodium Chloride (Commercial Salt): As water is recovered and the brine approaches saturation, sodium chloride reaches its limit first and precipitates out as high-purity cubic crystals, dewatered via continuous centrifuges.

  4. Ammonium Chloride: Ammonium chloride has higher solubility at elevated temperatures than sodium chloride. By chilling the residual liquor in a secondary step, ammonium chloride crystallizes out separately as a dry solid.

The outcome is Zero Liquid Discharge (ZLD): no liquid effluent remains. 100 MLD seawater intake yields 40 MLD RO permeate plus 60 MLD HPDD recovered water, totaling 100 MLD clean water, alongside separated, market-ready solid chemicals.

5. Alignment with the 3 Promotional Verticals

  1. Industrial ZLD (Textile, Paper, Chemical):

    Replaces the entire traditional utility train (boiler, multi-effect evaporator, condenser, cooling tower) with a single modular HPDD skid, significantly cutting capital costs and energy consumption while recovering process water and dry cake.

  2. Sodium Bicarbonate & Ammonium Sulfate:

    Reacting brine sodium chloride with captured carbon dioxide and ammonia produces sodium bicarbonate (baking soda) and ammonium chloride. Integrating sulfate-rich streams allows direct production of ammonium sulfate fertilizer.

Modular Magnesium Nitrate Platform:

Converts low-value magnesium chloride brine into premium, water-soluble greenhouse fertilizer without requiring mined magnesium rock. This is well-suited for water-scarce agricultural regions like Oman.