Melting and filtration of sulphur

The main raw material of sulphuric acid production is sulphur, coming from the unit of:

  • receiving, filtering and storing of liquid sulphur;
  • receiving, storing, melting and filtering of lump and granulated sulphur.

Melting and filtration unit (hereinafter referred to as MFU), the gondola cars sulphur  unloading unit includes the following process facilities:

  1. Storage for the reception and storing of granulated sulphur;
  2. - granulated sulphur unloading platform;

    - elevated railway track for stripping cars;

  3. Grab crane;
  4. Sulphur belt conveyor with frequency regulation and magnetic separator;
  5. Melting unit;
  6. Sulphur feeding unit;
  7. Precoat tank with pumping equipment;
  8. Filtration unit;
  9. Liquid sulphur tank with pumping equipment;
  10. Liquid sulphur tanks;
  11. PRS (pressure-reducing station)


    Unit production capacity is 45÷80 tons of sulphur per hour.

    Description of melting and filtration unit flowsheet and the process of unloading sulphur from gondola cars  

    Indoor storage is equipped, around the perimeter, with a retaining wall of reinforced concrete slabs up to 3 m high, an unloading platform with installation for simultaneous unloading of gondola cars, two bridge grab cranes for unloading, transfer and stacking of sulphur, a gantry loading system for mechanical sulphur unloading from gondola cars and hatches opening. Wall fencing helps to contain sulphur dust inside the storage and keeps sulphur free from precipitation and dust.

    Solid (granulated, lump) sulphur is supplied in gondola cars. Set of gondola cars is moved to the sulphur storage unloading platform by diesel locomotive. Bins with a conveyor system for transporting sulphur to smelters are placed along the edges of the storage. The loading of bins with sulphur is carried out with a grab crane, as well as truck loaders. Bins are equipped with stainless steel receiving grids made to trap pieces of sulphur larger than 100 mm.

    Melting section is located adjacent to the lump sulphur storage. From the storage, solid (granulated, lump) sulphur is fed to the sulphur smelters through belt conveyor system. Sulphur smelters are cylindrical apparatuses with cone bottom with built-in stack heating elements (registers). Solid (granulated, lump) sulphur with ambient temperature is loaded into the smelters. The process of melting granulated sulphur occurs due to heat transfer through the wall of heating steam elements (registers) inside the smelters. In the center of the smelter there is a propeller agitator in guide cylinder.

    After filtration, liquid sulphur corresponds to the parameters given in Table 1.

    Table 1 - Comparative characteristics of the main parameters before and after filtration

    Parameter

    Before filtration

    After filtration

    Mass fraction of ash, % not more than

    0,02

    0,005

    Mass fraction of base substances, % not more than

    0,06

    0,03

    Mass fraction of base substance, % not more than

    99,98

    99,99