NFM Filter Equipment Division

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Soda Ash

NFM Horizontal Belt Vacuum Filter Specializes in Soda Ash Production

Sodium carbonate (also known as soda ash, washing soda and soda crystals) -- Na2CO3 -- is the water-soluble sodium salt of carbonic acid.

Soda ash is an odorless, white powder that absorbs moisture rapidly from the air (hygroscopic).

It occurs naturally as heptahydrate (mined in several places in US) or, most commonly, it is prepared by chemical reaction (Solvay and Hou process being the most common processes) from sodium chloride (NaCl), limestone (CaCO3) and ammonia (NH3).

2015 world production was 57 million tons, 46% of which is in China.

Soda ash is widely used in the Glass industry (50% of total production), Soap and detergents (15%), Chemical industry (9%), Alumina and metals refining (6%), Glass fibre manufacture, Petroleum refining, Mineral processing in mining, Textile processing, Pulp & Paper.

NFM Soda ash Filtration

Typical soda ash slurry, fed from carbonating tower, contains 15-20% wt of solids, with a temperature between 25 and 50°C. Solids must be efficiently dewatered and washed to minimize NaCl content.

In the past, Rotary Drum Vacuum Filters (either Scraper Discharge or high speed rotary drum filters) were used.  Though the footprint is small, the cake washing efficiency has always been limited.  And counter-current cake washing has been impossible.

Today, many plants are replacing their rotary drum filter batteries with a single Horizontal Belt Vacuum Filter.

The advantages are as follows:

  • Lower cake moisture (savings on drier cost)
  • Increased capacity x m2 filtration area
  • Optimal cake washing efficiency (economical wash: solids ratios), with counter-current washing available
  • High filtration efficiency
  • Low NaCl in cake with minimum water consumption
  • Low pressure steam injection of cake for further moisture reduction

The hydraulic load on the belt filter is significant, so a careful design and precise calculation are necessary in order to minimize the filtration area and to optimize capacity and throughput.

NFM has specific Horizontal Belt Vacuum Filter configurations for Soda Ash filtration:

  • Belt design (thickness, sloped grooves, specifically designed holes for laminar flow)
  • Cake wash water distribution design (to minimize cake dissolution and to reduce water consumption)
  • Long life Soda Ash filter cloth (when used with NFM self cleaning spray bars)
  • Fume hood to prevent any ammonia smell
  • Suitable materials of construction for the salty conditions

Customer specific requirements on design are welcome and fulfilled at our best performance.

Typical NFM Horizontal Belt Vacuum Filter Performances

Cake Moisture:  12-14*% (< 10% with steam injection)

Production: 700-800* Kg/h/m2, soda ash (Solvay-Hou Process), 1000* Kg/h/m2 (Natural Soda Ash)

Wash Water: down to 0.5 m3/t soda ash

NaCl in Filter Cake: down to 0.05*% wt

*These are performance numbers for an average Soda Ash plant. These numbers may vary according to solids Particle Size Distribution and initial NaCl content in the slurry.

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