Method for generating steam from raw water, in particular from blow down water coming from a steam generator

A method for generating steam from a feed water containing solid particles in suspension and mineral materials in solution, wherein the method comprises the following steps:

• (A) directing said feed water into liquid phase water contained in an instant expansion tank, the instant expansion tank containing a liquid fraction of water and a non-liquid fraction of water;
• (B) in said instant expansion tank, heating said feed water by mixing said feed water with a stream recycled from a heat exchanger;
• (C) compressing the liquid fraction in said instant expansion tank and sending the liquid fraction to an inlet of the heat exchanger, the heat exchanger having a non-expanded fraction in a liquid state;
• (D) heating the non-expanded fraction in said heat exchanger while maintaining the non-expanded fraction in the liquid state, the heated non-expanded fraction in the liquid state forming the stream for recycling to said instant expansion tank;
• (E) recycling the stream from step (D) into said instant expansion tank for mixing with said feed water;
• (F) in said instant expansion tank, expanding said stream recycled into said instant expansion tank in step (E) and generating, by instant expansion, a steam stream containing the mineral materials of the feed water;
• and
• (G) separating solid particles at a bottom of said instant expansion tank, the solid particles at the bottom of said instant expansion tank being comprised of the suspended solid particles in the feed water and further solid particles formed from precipitation of mineral materials in solution under action of temperature and/or pressure in said instant expansion tank, and decantation associated with mineral materials derived from vaporization in said instant expansion tank, the separating being as a blowdown containing water and said solid particles;
• (H) directing the blowdown from step (G) to a secondary instant expansion tank to obtain:
• a secondary steam stream, and
• a secondary blowdown containing water and the solid particles of the blowdown of the step (G) which have been decanted in said secondary instant expansion tank.