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Notes on Solar Salt Making by Different Methods This paper is prepared to serve as guide or reference for those who are or getting to be involved in the solar salt production project. Data are obtained from documents searched from the internet. 1. Salt production using Plastic sheets by Community Development Library (internet file name is salt production using plastic sheets)

Notes on Solar Salt Making by Different Methods

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This paper is prepared to serve as guide or reference for those who are or getting to be involved in the solar salt production project. Data are obtained from documents searched from the internet

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Page 1: Notes on Solar Salt Making by Different Methods

Notes on Solar Salt Making by Different Methods

This paper is prepared to serve as guide or reference for those who are or getting to be involved in the solar salt production project. Data are obtained from documents searched from the internet.

1. Salt production using Plastic sheets by Community Development Library (internet file name is salt production using plastic sheets)

2. Documentation on Solar Salt Experiences in Mondragon (Center for Empowerment and Resource Development, Inc. –CERD). Internet file name is documentation on solar salt

Page 2: Notes on Solar Salt Making by Different Methods

experiences in Mondragon

a. Every module has three different size and measure different deep for the salt production.  b. 1st Box – 6 inches deep, 1.20 meter Length and 80 cm. width. Contains 7 water cans (Evaporation basin). In 15 – 17 Days (depends on weather condition), the seawater was transferred to second box called evaporation process for about 15 days.

c. 2nd box –  3 inches deep 1 meter X 1 meter, After 15 days, the sea water was transferred to the third box for crystallization process.

d. 3rd box -    1 inch deep 1 meter X 1 meter. Crystallization process occurred after 10 days.Then it was harvested and ready for market

e. Every 18 water can of seawater produced 14 kls of salt for a minimum of 25 days under direct sunlight and 27-28 days during dry and wet season but salt was not produced at all with continuous rains.

f. There were also observations done by the household during harvest time. There were bigger salt granules harvested in the afternoon compared to those harvested in the morning. Hence they recommended that harvesting be done in the morning for better and smaller granules. g. The salt granules produced by the fisherfolk was already tested by the DOST. Result showed that there was only 87 % sodium chloride content in the granules. The country’s ASIN Law requires 97% as standard content of sodium chloride. Hence the program needs to look for ways to increase the volume and the salt content of the fisherfolk’s product

1. 3. Maine Solar Salt Project (Greenhouse structure) in Maine, USA (internet file name is Maine Sea Salt Company, Natural Sea Salt , Solar -Evaporated Salt )

a. This is the case of Maine Sea Salt Company whose source of sea water is in the interior part of the Bucks harbor near the port as shown in the picture and map below. Google maps showing source of sea water within Bucks Harbor

Page 3: Notes on Solar Salt Making by Different Methods

b. This is a big commercial size production of salt, the process of which is presented below.

Page 4: Notes on Solar Salt Making by Different Methods

c. The produced salt is packed in bottles and other type of containers (Internet file name is Solar Salt from the Maine Sea Salt Company

4. The science of solar salt making

a. Data on specific gravity of sea water or brine solution, volume of brine remaining, kg of salts or water remaining in solution are presented in the Table below

Source: Internet fine name is Solar Salt Production Process

b. The data indicate that as sea water has specific gravity of 1.0247 with corresponding total salts content of 35.038 kgs in 1 cu.m. of sea water with corresponding salinity reading of 35.036 ppt. When using a hydrometer calibrated at 25oC, the salinity of 35.038 ppt will read 1.0247 in the hydrometer.

c. By making a graph on the above tabulated data, the corresponding depth of the sea or

Page 5: Notes on Solar Salt Making by Different Methods

brine solution during its progressive evaporation as manifested by increasing specific gravity until precipitation of CaSO4 and then NaCl can be determined as shown below.

1) From the 6-inch water depth to 0.64 inch, the 1st to precipitate is CaSO4 by 87.6% of the 1.416 kg or 1.241 kg content of CaSO4 per 1,000 liters (1 cu.m.) of sea water and this happens when the specific gravity of sea water is 1.21

2) At more or less 0.64 inch of water in which there is the presence of CaSO4 precipitate, the brine is transferred to another tray, pond or compartment leaving the CaSO4 precipitate behind. If the CaSO4 will not be removed and just allow the further evaporation to proceed, then the salt will have a bitter taste.

3) The brine is allowed to further evaporate down to ½ half of the 0.64” or 0.32” with specific gravity of 1.245 or 28.5 degree Baume reading. At this point, NaCl has precipitated to about 19.7 kgs per cu.m. of sea water or 72% of the total 27.28 kgs of NaCl in 1 cu.m. of sea water. When the precipitate is removed from the remaining brine solution, the NsCl purity is

Page 6: Notes on Solar Salt Making by Different Methods

99.7 %. Remaining volume of brine is 39.4 liters from the 1 cu.m. of sea water. The 39.4 liters of brine contains 0.028kg CaSO4, 0.742kgs KCl, 3.375kgs of MgCl2, 0.086kg of NaBr and 35.10 kg of water. Hydrometer can be used in measuring the specific gravity of the sea water or brine solution which can be converted to salinity reading based on the water temperature; there is a conversion table for this purpose.

4) If evaporation of the sea water will be done until all the salts are precipitated without remaining brine solution, then NaCl purity will just be 27.28kgs of NaCl divided by 35.039 of total salts = 77.85% purity.

5) The higher percentage purity of NaCl will be determined by how much volume of brinesolution should be left behind in retrieving NaCl salts. Distance from shoreline where sea water

supply is fetched does not influence purity of NaCl.

6) The lower percentage purity of NaCl salt that is produced in certain projects could be due to the fact that, aside from not separating the CaSO4 salt which is the 1st to precipitate, the remaining brine solution left after the last stage of evaporation or the crystallization stage was less than the required 0.0394 cu.m. (39.4 liters) if the starting volume was 1 cu.m. of sea water. If the starting volume is equivalent to the 6 inch-water depth, then the final depth is 0.32 inch or 0.8cm of brine. Therefore, accuracy in measuring the remaining volume of brine solution is the “trade secret” in making high quality NaCl salt product.

7) In the Maine solar salt production process, the water is “pumped into one of four (soon to be eight) settling houses, where it is allowed to evaporate up to 80 percent.  Then any large impurities the first filter may have missed have settled to the bottom of the evaporation floors and are left behind when the water is pumped to the finishing houses. Any foreign material that may remain is removed during this process as the water is passed through a 5-micronfilter . . . What is left after the final evaporation is pure salt with the taste of an ocean breeze.”

Prepared by:

Edmundo EnderezAugust 21, 2012