Evaporation / Crystallisation Challenges in the Fertiliser Market

Keywords: vaporation, crystallisation, potassium chloride (potash), ammonium sulphate, potassium sulphate (SOP), water soluble fertiliser.

In the field of fertiliser production, the main process technologies required commonly include evaporation and/or crystallisation. When designing commercial production applications using these technologies the technical challenges for the designer can be numerous and complex.

Process design challenges may include achieving a high purity requirement for the product salts (crystal habit, size and purity), meeting environmental constraints (for example: no liquid waste stream), achieving high product purity requirements despite the use of waste streams with high impurity contents as a feed material, and optimisation of heat integration for maximum energy efficiency.

Initially, this paper provides a brief overview of the types of evaporation and crystallisation applications (including evaporative, cooling and reactive crystallisation) and describes some of the equipment that can be used for the production of typical crystalline fertiliser products (including falling film, forced circulation, multiple effect, mechanical vapour compression, thermo-compression, PITM (draft tube baffle), growth type, multiple stage vacuum flash). Basic information about the equipment is provided and typical uses reviewed.

Through three case studies, this paper provides an overview of real world experience based on the use of HPD® evaporation and crystallisation systems provided by Veolia. Topics covered in these case studies include:

Developing and validating new processes.

The value of performing laboratory and pilot tests.

Using the right chemistry simulation software or data.

Making appropriate evaporation or crystallisation technology choices.

Considerations in the planning and execution of large scale, highly-integrated, unique and customised projects.

K. Schooley, V. Bourgier and R. Lawson, Veolia Water Technologies, Plainfield, Illinois, USA

32 pages, 12 figures, 3 tables, 10 plates, 5 references