CN1554280A

CN1554280A - New process for preventing refinery salt from caking

Info

Publication number: CN1554280A
Application number: CNA2003101193643A
Authority: CN
Inventors: 张家凯; 蔡荣华; 张凤友
Original assignee: Tianjin Institute of Seawater Desalination and Multipurpose Utilization SOA
Current assignee: Tianjin Institute of Seawater Desalination and Multipurpose Utilization SOA
Priority date: 2003-12-23
Filing date: 2003-12-23
Publication date: 2004-12-15
Anticipated expiration: 2023-12-23
Also published as: CN1267020C

Abstract

The present invention relates to a new technological process of preventing refined salt from caking. Trace amount of potassium ferrocyanide is added into saturated refined salt solution of pH 7-9 to prepare material solution with potassium ferrocyanide content of 1.0-3.0 mg/L, and the solution is evaporated to concentrate in evaporating crystallizer in the evaporation strength of 0.2-0.4 kg water/hr.L while controlling the material slurry concentration in not higher than 10 vol%, so as to obtain refined salt without caking. The refined salt has potassium ferrocyanide content not higher than 10 mg/kg. The said process is obviously superior to traditional production process.

Description

Prevent the new technology of purified salt caking

Technical field

The present invention relates to the salt manufacturing technology, particularly the purified salt manufacturing technology of artificial method of evaporating.

Background technology

Purified salt is requisite edible product in people's daily life, at the also very wide model of industrial use.Because impurities is few in the purified salt, be specially adapted to some fine chemistry industry.In the process of a large amount of use salt, maximum difficulty is the agglomeration problems of salt.The caking of sodium chloride crystal is its intrinsic characteristic, and this depends primarily on the humidity in the environment.Usually, salt is 75% moisture absorption when above in relative humidity, is lower than at 75% o'clock and emits moisture, and this phenomenon constantly repeats, and when acquiring a certain degree, begins fixed.The factor that influences the salt caking is a lot, and with regard to crystal product itself, importantly granularity, size distribution and crystalline substance are practised (profile of crystal).The particle of salt is big, and is evenly distributed, and then can increase the voidage in the salt deposit, makes salt deposit that certain ventilative degree be arranged, the easier liquidation of salt grain, and it is just little to produce fixed tendency; If the salt grain is thin and skewness, then cause the closelypacked state of salt deposit, promote the fixed of salt grain.The shape of crystal is directly relevant with the contact point between crystal, the easier caking of crystal of the shape that contact point is many between crystal.

In the production of purified salt, granularity and the size distribution of effectively controlling product crystal are very difficult.Moreover, want to guarantee the packing of product excellent, short time storage and to keep storage place to have lower temperature and humidity all be very difficult.Therefore, the profile that changes crystal is alleviated bonding between crystal to reduce the contact point between crystal and evenly to add anti-caking agent, becomes the important method of anti-caking.The anti-caking agent of the alleviation purified salt caking that now adopts has potassium ferrocyanide or basic magnesium carbonate etc.Existing method of adding anti-caking agent is to spray certain density anti-caking agent solution in the wet salt before entering drying process, is dissolved in the product after making it together to enter the drying process dehydration with wet salt.

The observation of long term production and the discovery of test back, the existing additive method that is adopted clicks wherein no matter add, and still adopts which kind of addition manner, all is difficult for accomplishing an amount of, even.Because additive solution can only be sprayed at the superficial layer of salt, and the salt of middle and lower part can not be sprayed onto.After entering drying process, also can only carry out the process of physical mixed, it is excessive that local salt may spray additive solution, and it is very low not to be sprayed onto in the salt of part additive level, even be zero.Therefore, the agglomeration problems of purified salt is difficult to obtain desirable effect all the time.

Summary of the invention

The present invention has taked to change the adding method of conventional anti-caking agent, and by control suitable evaporation rate and pulp density, make anti-caking agent both play the effect of anti-caking, play the effect of crystalline form inhibitor again, in evaporation and crystal process, changed the profile of crystal, contact point between product crystal is significantly reduced, simultaneously, solved anti-caking agent and added an irregular difficult problem.The new technology that prevents the purified salt caking involved in the present invention is to adopt ferrocyanide (sodium ferrocyanide or potassium ferrocyanide) with trace to add pH value in the saturated brine after the making with extra care of 7-9, making concentration is the feed liquid of 1.0～3.0 mg/litre (in sodium ferrocyanide or potassium ferrocyanide), again so that 0.2～0.4 kg of water/hour rising evaporation intensity carries out evaporation and concentration, control its pulp density≤10% (volumetric ratio), can be prevented the purified salt of caking.Ferrocyanide content (in potassium ferrocyanide)≤10 milligram/kilogram in the purified salt.

The purified salt production technology that the present invention relates to has tangible advantage than traditional production technology:

Solve anti-caking agent and added irregular problem, can control the concentration homogeneous of anti-caking agent in the product effectively; The product crystalline form is the cubical or dendritic crystallization of star of concave surface, has changed the profile of sodium chloride cubic crystal, has reduced the contact point between crystal; Small product size density is low, and apparent density is 0.65～1.2 gram/cubic centimetre, has bigger volume when the identical weight than common purified salt; The product dissolution velocity is fast, fast 1.2～2 times than general cube sodium chloride; Product has higher wettability power, and the sticking water yield is higher than 1.2～2 times of cube sodium chloride of equal weight.

The specific embodiment

Embodiment 1

Will be through refining saturated brine, pH=7 adds sodium ferrocyanide, and making its concentration is 1.0 mg/litre.The glass system of putting into Natural Circulation crystallizing evaporator evaporation and concentration, the feed liquid capacity is 10 liters in the crystallizing evaporator, evaporation intensity is 0.39 kg of water/hour rise crystallizing evaporator vaporization chamber pressure 79.5KPa (vacuum), 68 ℃ of evaporation feed temperatures.When salting out, the beginning continuous feed, intermittently salt discharge, charging rate is 9 liters/hour, pulp density 8%.The wet salt of discharging is the ferrocyanide sodium content after dehalogenation, drip washing, oven dry be that 9.0 milligrams/kilogram crystalline form is the product purification salt of concave surface cube and star tree dendritic crystal, and small product size density is 0.70 gram/cubic centimetre.

Embodiment 2

Will be through refining saturated brine, pH=8 adds sodium ferrocyanide, and making its concentration is 2.0 mg/litre.The glass system of putting into Natural Circulation crystallizing evaporator evaporation and concentration, the feed liquid capacity is 10 liters in the crystallizing evaporator, evaporation intensity is 0.30 kg of water/hour rise crystallizing evaporator vaporization chamber pressure-10.4KPa (gauge pressure), 105 ℃ of evaporation feed temperatures.When salting out, the beginning continuous feed, intermittently salt discharge, charging rate is 3 liters/hour, pulp density 7%.The wet salt of discharging is the ferrocyanide sodium content after dehalogenation, drip washing, oven dry be that 7.5 milligrams/kilogram crystalline form is the product purification salt of concave surface cube and star tree dendritic crystal, and small product size density is 1.0 gram/cubic centimetres.

Embodiment 3

Will be through refining saturated brine, pH=9 adds potassium ferrocyanide, and making its concentration is 3.0 mg/litre.Put into steel forced-circulation evaporation crystallizer evaporation and concentration, the feed liquid capacity is 300 liters in the crystallizing evaporator, and evaporation intensity is 0.4 ton of water/hour cubic meter, crystallizing evaporator vaporization chamber pressure 82.3KPa (vacuum), 67 ℃ of evaporation feed temperatures.When salting out, the beginning continuous feed, intermittently salt discharge, charging rate is 80 liters/hour, pulp density 9%.The wet salt of discharging is after dehalogenation, drip washing, oven dry to the ferrocyanide potassium content is that 7.6 milligrams/kilogram crystalline form is the product purification salt of concave surface cube and star tree dendritic crystal, and small product size density is 0.82 gram/cubic centimetre.

Embodiment 4

Will be through refining saturated brine, pH=7.5 adds potassium ferrocyanide, and making its concentration is 3.0 mg/litre.Put into steel forced-circulation evaporation crystallizer evaporation and concentration, the feed liquid capacity is 300 liters in the crystallizing evaporator, evaporation intensity be 0.3 ton of water/hour. cubic meter, crystallizing evaporator vaporization chamber pressure-16.8KPa (gauge pressure), 103 ℃ of feed temperatures of evaporation.When salting out, the beginning continuous feed, intermittently salt discharge, charging rate is 120 liters/hour, pulp density 5%.The wet salt of discharging is the ferrocyanide potassium content after dehalogenation, drip washing, oven dry to be 5.4 milligrams/kilogram be the product purification salt of main body crystalline form with the concave surface cube, and small product size density is 1.1 gram/cubic centimetres.

Claims

1, a kind of new technology that prevents purified salt caking is characterized in that ferrocyanide entering evaporation and concentration in the crystallizing evaporator with after saturated brine evenly mixes, and obtains the purified salt product of the cubical or star tree dendritic crystal of concave surface.

2, the new technology that prevents the purified salt caking according to claim 1, the pH value that it is characterized in that saturated brine is 7～9.

3, the new technology that prevents the purified salt caking according to claim 1 is characterized in that ferrocyanide is sodium ferrocyanide or potassium ferrocyanide, and the concentration behind the adding saturated brine is 1.0～3.0 mg/litre.

4, the new technology that prevents the purified salt caking according to claim 1 is characterized in that the saturated brine that contains ferrocyanide continuously, stably enters in the crystallizing evaporator, control evaporation intensity and pulp density.

5, the new technology that prevents purified salt caking according to claim 4, the evaporation intensity that it is characterized in that feed liquid in the crystallizing evaporator are 0.2～0.4 kg of water/hour rise.

6, the new technology that prevents the purified salt caking according to claim 4 is characterized in that pulp density requirement≤10% (volumetric ratio) in the crystallizing evaporator.