JPH07242788A - Preventing method for deposition in evaporator for concentration - Google Patents

Abstract

PURPOSE: To inhibit the deposition within evaporation tubes for condensing a sugar liquor in a sugar manufactory and a black liquor in the pulp industry by using a blocking agent (mixture) and a deposition inhibitor composed of a terpolymer, a copolymer or a polymer prepared from three types of specific monomers.

CONSTITUTION: (A) As a blocking agent or a blocking agent mixture, EDTA, a salt thereof, DTPA(diethylenetriaminepentaacetic acid) and a salt thereof are used and the amount to be used is 0.0-15.0% based on the solids content. (B) A terpolymer, copolymer or polymer which comprises 85.0-100.0% monomer I represented by formula I (wherein R₁ and R₂ are each H or methyl; X₁ and X₂ are each H or an alkali metal; and Y is hydroxyl, a phosphoric acid group or a sulfonic acid group; and the same is applied to the codes in the following formulae); 20.0-35.0% monomer II represented by formula II; and 10.0-25.0% monomer III represented by formula III is used, and the molecular weight is 15,000-25,000. The amount of the deposition inhibitor to be used in the pulp industry is 15-50 g per ton of the solids content of a black liquor.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

In the sugar and paper industry,
The evaporation process uses more than half of the energy required to operate this type of factory. The liquid referred to this step contains a dissolved mineral salt whose solubility decreases with increasing temperature and with increasing solution concentration.

Some of these salts deposit on the heated surface of the evaporator to form a hard deposit, which acts as a thermal insulator and therefore requires periodic removal to maintain evaporation efficiency. .

The full capacity of an evaporator is based on the amount of water that can be evaporated from a liquid in a given time. This amount of water, on the other hand, is directly related to the heat transfer rate through the calandria tubes of the evaporator. Thus, high heat transfer rates increase both capacity and thermal efficiency.

Several factors which determine the total heat exchange capacity, especially in evaporation systems, are: -Vapor and liquid velocities; -Air and non-condensable gas removal; -Condensate removal on the water vapor side; Materials of construction; -there is cleanliness and wrinkle of the tube surface.

Of these, tube surface cleanliness is the limiting factor most closely associated with heat exchange in sugar mill evaporators.

Deposition can occur on the liquid side as well as on the water vapor side; the biggest problems are usually found on the liquid side due to the high concentration of its salts and / or organic matter.

If these deposits accumulate along the pipe and the loss of capacity and heat exchange efficiency becomes unacceptable, the process is interrupted for cleaning of the unit and, above all, the loss of production. And increase maintenance costs.

The presence of deposits, which require cleaning, indicates that considerable energy is lost due to heat exchange.

Deposits cause thermal insulation and determine the increase in water vapor consumption to continue the work.

Although all deposits found in sugar or black liquor evaporators are often referred to as deposits, the deposits considered herein are mixtures of deposits, sludge and corrosion byproducts. Is.

True deposits are extremely adherent, crystalline and highly insulating; on the other hand, sludge is generally less adherent and amorphous, which is also insulating. is there. Corrosion by-products, if present, are generally incorporated into sediment or sludge.

-Characteristics of evaporators in sugar mills In the sugar industry, the evaporation process is carried out from about 15 ° Brix of sugar liquid solids for subsequent crystallization of sugar to 65-75.
° Helps to concentrate to Brix.

A typical evaporation system has four working columns, as proposed by Rillieux in 1840. Figure 1 shows a simplified diagram of this system.

In the multi-stage working tower evaporator, the steam generated by the evaporator body functions as a heating means for the next working tower, so that the latent heat of the water evaporated in one working tower is transferred to the next working tower. In a series of evaporators arranged for use in heating. External water vapor is first
Heat the working tower of 1. A condenser and air ejector create a vacuum in the last working column to remove non-condensable gases from the system.

The deposits are due to problems in sugar cane harvesting and washing, and to the suspension present in the molasses due to the sulfite treatment, lime treatment, clarification and filtration of the molasses. Generate from a substance. These substances are primarily
Deposit on the evaporator body of.

They can also be produced from non-sugars (mainly inorganic and organic hard salts) in solution, which
It becomes insoluble as the sugar solution is concentrated. These deposits are mainly found in the last working tower.

The deposits are coarser at the bottom of the tube where the sugar liquid has a relatively small turbulence and finer at the top where the sugar liquid is boiling.

In general, the presence of deposits in sugar mills can lead to reduced heat exchange capacity, increased steam consumption, reduced temporary production, premature wear of equipment, and increased maintenance costs.

The production of deposits directly affects production, requires periodic closures for their removal, and involves mechanical or chemical wear of the equipment, which is relevant to the plant. Is annoying. The result of this wear is an increase in maintenance costs due to the need for tube replacement.

Sugar cane sugar liquor contains various impurities, especially mineral salts, whose solubility decreases with increasing temperature and / or its superconcentration and which precipitates on metal surfaces.

Initial deposit formation is the result of crystallization on the hot surface of a concentrated solution of deposited salt. The film of sugar solution in the vicinity of the heated surface tends to saturate even when the total sugar solution volume is below the saturation point. The deposits accumulate with the growth of crystallographic bodies induced by saturation due to contact with the saturated liquid film.

The formation of deposits is influenced by the conditions present in the evaporation system, since they affect the solubility of the salts present in the molasses and the formation of deposits.

The main factors are: temperature, total dissolved solids, pH, sucrose content, and metal wrinkles.

Each of these factors has a direct or opposite effect on the solubility of the salt.

Calcium carbonate is the most commonly found deposit in the multi-stage tower evaporator (in the first and last tower bodies). This indicates the inverse relationship between solubility and temperature and pH.

Calcium sulphate may be found in the pre-evaporator and in the first and second working columns and may reach up to 30% of the deposit; its presence is the third. And not common to the fourth working tower. Its solubility is inversely related to temperature and pH.

Calcium phosphate and iron phosphate show an inverse relationship between solubility and temperature and pH. Both salts show increased solubility with increasing sugar concentration; therefore more often 4.0 to 20.0% in the first column.
It appears in the range of (P ₂ O ₃ ), and is produced in the third and fourth column bodies in a small amount of approximately 0.5 to 2.0%.

[0028] Silica, calcium silicate and magnesium silicate have a direct relationship between solubility and temperature, while solubility decreases with increasing sugar concentration.
The lower temperature results in the deposition of silica, calcium and magnesium silicate in the final evaporation column, combined with increased sugar concentration and solids.

Deposits of calcium oxalate generally occur in the last working column of the evaporator. The solubility of calcium oxalate is not significantly affected by changes in pH and temperature.

Magnesium deposits can be produced in all evaporators of the multi-stage tower system, but in small amounts, ie 0.5 to 3.0% in the form of magnesium oxide.

Iron and other transition metals also form deposits in multi-stage tower sugar liquid evaporators. The most common sources are iron deposits derived as iron (II) ions from water sources, or those formed as a result of system corrosion.

For purposes of illustration, Table 1 shows the compositional profile of the deposits obtained through the particular analysis. These results were confirmed through test samples placed in the system at the beginning of work in the multi-stage working tower evaporator of a sugar cane sugar mill.

Table 1 Deposits (%) Sulfuric acid Carbonic acid Phosphoric acid Silicic acid Organic device Calcium Calcium calcium Calcium iron silicate Calcium object pre-evaporator 49.0 7.5 10.0 12.0 − 18.0 1st action column 36.0 11.0 11.0 11.0 − 26.0 2nd action column 14.0 12.0 7.6 13.0 − 24.0 3rd working tower 0.0 11.0 6.0 14.0 <0.5 27.0 4th working tower 0.0 43.0 1.0 7.0 15.0 33.4 The formation of deposits in the evaporator is once or twice a month cleaning the equipment on average. Required interruptions for.

Inhibition of deposition in the evaporator has a significant impact on the cost of the sugar mill due to the following factors: -reduction in cost with evaporation temperature; -increase in average evaporation capacity; and- Energy cost savings for all plants.

Characteristics of Black Liquor Evaporator Recovery of chemical reactants is an essential part of the sulfate process. The functions of the recovery system in the papermaking industry are: -Creating steam to reduce costs for several operations such as digestion, bleaching and drying; -A heat-treating solution with a composition suitable for its neutralization. Enabling manufacturing; and-eliminating potentially contaminated parts of the effluent.

Black liquor diluted with a portion of the water used to wash the pulp and having a solids content of about 16% is concentrated in a multistage tower evaporator to a solids content of approximately 50%. .

The function of the evaporator is to concentrate the black liquor obtained from the pulp washing liquor to a solids content which, when injected into the recovery furnace, will continue to ignite and burn due to the organic matter it contains. Is.

The composition of black liquor varies considerably in different plants, depending on the white liquor used and on the system and equipment used for digestion. The major part of the alkali in black liquor exists as sodium carbonate or organic compounds, the latter of which has chemistries very similar to those of carbonates. The largest part of non-cellulosic organic substances contained in wood is alkaline lignin, which reacts with sodium hydroxide.
This produces resin soaps and organic acid salts. In the sulphate process, there are significant amounts of sulfur-containing organic compounds other than some mercaptans that cause the characteristic odor of black liquor. Residual alkali present in the liquor is found in the soda process plant liquor as free sodium hydroxide and in the sulfate process plant liquor as sodium hydroxide and sodium sulfide. Also, small amounts of sodium sulphate and silica (SiO ₂ ) are present as well as other substances such as iron oxide, alumina, sodium chloride and potassium hydroxide.

A multi-stage working column evaporator with long vertical tubes has been the most economical means to reach concentrations in the range of approximately 40 to 45%. Five- and seven-stage working tower evaporators with two first working towers contained in a single evaporator body have proven suitable.

Table 2 shows the typical composition of the deposits obtained in the two last working columns of the six-stage working column evaporator system of an alkaline pulp mill.

[0041] During normal operation of Table 2 Compound percentage _{(%) CaCO 3 62.8 MgCO 3} · 3H 2 O 10.6 iron 7.7 Al (OH) ₃ 1.8 silicate 5.5 organics 0 Others 11.6 alkali method, the evaporation system Liquid to pass 1
About 0.35 tons of sediment is deposited for every 000 tons (dry basis). Although this ratio is relatively small, it requires closing the system for cleaning within a period of 4 to 8 months, which means that the closing of the recovery system is typically another unit of the pulp mill. It also requires an interruption of 4
Or 6 days of lost production.

In order to prevent the formation of deposits during the evaporation of sugar liquor in sugar mills, US Pat. No. 4,389,324 discloses polyacrolein or methacrolein compounds, polyacrolein or methacrylic acid compounds, compounds of the copolymers already mentioned. , A polymer composition comprising a polymer of polyacrylamide and maleic anhydride or a mixture of at least three polymers selected from the compounds in combination with vinyl methyl ether. Also, US Patent 4,4
52,703 describes a method consisting of adding a polycarboxylic acid or a salt thereof, and a phosphonate and a polycarboxylic acid telomer to a molasses. Fugo (E. H
ugot), instruction manual for sugar industry engineers (Manual para
Ingenieros Azucareros) 1976 is sugar beet 1
It describes the use of sodium polyphosphate at a rate of 8 g per ton and calcium tetraphosphosugarate at a rate of 5 to 15 g per ton of sugar cane. James CP Chen, Sucrose Handbook (Cane Sugar)
Handbook), 1985, with good results in some parts of Asia, America and Australia, using tetraphosphosugar acids and some organic phosphates, using acrylic acid polymers, and silicon-containing acrylic acid. Mention is made of the use of polymers.

In order to prevent the formation of deposits on the metal surfaces of multi-stage tower evaporators used for the processing of black liquor in the pulp industry, US Pat. No. 4,941,946 describes the introduction stage of a multi-stage tower evaporator system. A method of treating black liquor with an aqueous solution of low molecular weight polyacrylic acid and adding an aqueous solution of a copolymer of sulfonated styrene and maleic anhydride to one of the subsequent working columns is described. U.S. Patent 3,289,734 has 1
A method is described which comprises using a polymeric maleic acid-styrene resin having a molecular weight of less than 10,000. U.S. Pat. No. 4,357,207 presents a method consisting of treating black liquor with polydimethyldiallylammonium chloride or a modified low molecular weight cationic polyacrylamide, and Japanese patent JP 511480 91 is a partially hydrolyzed polyacrylamide or copolymer. Disclosed are polyacrylamide based anti-deposition agents.

The present invention provides that the liquid to be vaporized at any stage of the evaporation process comprises: A) a sequestrant or sequestrant mixture such as EDTA.
-Ethylenediaminetetraacetic acid or its salt, NTA-
Nitrilotriacetic acid or its salt, DTPA-diethylenetriaminepentaacetic acid or its salt, and B) Monomer: and In each of the above formulas, R ₁ and R ₂ are hydrogen or a methyl group; X ₁ and X ₂ are an alkali metal or hydrogen; Y is a hydroxyl group (—OH), a monophosphate group (—P (O ) (OH) ₂ ) or a sulfonic acid group (—SO ₃ X ₃ ) in which X ₃ is an alkali metal or hydrogen, or a terpolymer or copolymer, or a mixture of polymers It relates to a method for preventing the formation of deposits in sugar mill evaporators and in paper mill black liquor evaporators, based on the addition of a mixture of deposition inhibitors.

Examples of monomers I are acrylic acid and methacrylic acid, and salts thereof.

An example of monomer II is 2-acrylamido-2-
Methyl propane sulfonic acid and its salts.

An example of monomer III is 3-allyloxy-1,2-
Dihydroxypropane, 3-allyloxy-2-hydroxypropane monophosphate and 3-allyloxy-2-hydroxypropylsulfonic acid, and salts thereof.

The polymers which are the subject of the present invention are obtained in solution and comprise, in molar ratio, 50 to 95%, preferably 65 to 95% of monomer I, 0 to 35%, preferably 2
0 to 35% Monomer II, and 0 to 35%
Preferably 10 to 25% of monomer III. The molecular weight of this polymer is in the range 15,000 to 65,000, preferably in the range 15,000 to 25,000.

The mixture of components a and b can be used in any solids concentration, the most suitable form for its use being that which is represented by an aqueous solution with a product concentration of 5 to 50%. is there.

Component a or a mixture of components a represents a proportion of 0 to 50%, preferably 0 to 15%, in the final mixture. Component b or a mixture of components b is 50 to 100% in the final mixture,
Preference is given to proportions of 85 to 100%.

Suppression of deposition in a multi-stage tower evaporator using the subject compositions of the present invention is accomplished through the following three mechanisms.

Blocking-a stoichiometric reaction that forms a soluble complex of one or more metal ions. This is a characteristic reaction of component a according to the invention. This reaction takes place to a limited extent with component b.

-Dispersion-Repulsion between the particles of the deposited salt due to the charge of the anti-deposition agent additive.

-Crystal Modification-Surface effect of salt-bearing anti-depositing agents that acquire an amorphous, non-adhesive structure. The effect of crystal dispersion and modification is a property of the group b component (polymer) described above.

As mentioned above, the prior art to date refers to phosphorus-containing compounds, polyacrylic and silicon-containing polyacrylic esters, and several acrylic copolymers of acrylamide or maleic acid.

Phosphorus-containing compounds act according to the above three mechanisms and additionally have a low stability leading to the formation of metal phosphates which participate in the formation of deposits on the evaporation tube. This kind of material increases the mass of the deposit,
Makes the deposit more flexible and facilitates its removal. This type of compound may or may not reduce the mass of the deposit depending on its stability in relation to temperature conditions, pH, and process residence time.

Polyacrylates, like phosphorus-containing compounds, act according to the three mechanisms of prevention described above, often resulting in reduced deposits.
The most relevant drawbacks of their use are the large blockages that are selective in the context of some metal phosphates, sulphates and carbonates and have little or no effect on silicates. To have an effect. Depending on the salt composition of the sugar liquor or black liquor, these compounds can lead to a decrease in the deposits, but they cause an increase in their silica content, making their removal difficult.

Silicon-containing polyacrylates also act according to the above three prevention mechanisms. Its advantages and disadvantages are similar to those mentioned for polyacrylates. The presence of silicon in the molecule also contributes to the formation of non-adhesive colloidal complexes, which, like silicon, allows the molecule to decompose under operating conditions, reducing the silicate content of the deposit. Will contribute to the increase.

The copolymers in general exhibit the same effects as those of acrylic homopolymers or have the potential to act on a wider range of salts.

The polymers of which the appropriate combination is the subject of the present invention act according to the above-mentioned three deposition prevention mechanisms, but mainly through the mechanism of salt dispersion and crystal modification, of sugarcane and sugar beet. Acts on all spectra of salts found in sugar or black liquor concentration processes, such as carbonates, sulphates, phosphates, silicates, oxalates, iron, aluminum, magnesium, calcium, etc. Has the advantage of These copolymers and terpolymers have different ionizable groups, such as carboxylic acid groups, sulfonic acid groups, and complementary functional groups, such as hydroxyl groups, carbonyl groups and amide groups, for the purpose of exhibiting different salts thereof. The action occurs within a wide range of pH and temperature values through different molecular mechanisms. In addition, because of its various functionalities and its affinity for various substances related thereto,
They also show great ability to act on films on organic compounds and / or metal surfaces that act as insulators, forming compounds that form chambers that allow the growth of crystals in the vicinity of the evaporator tube. Prevent.

The present invention further contemplates the use of the sequestering agent itself in combination with the above copolymers and terpolymers in proportions less than that of the polymer. The goal of this joint use is to perfect the operation of the polymer and to enable increased efficiency and economy of the process. The most suitable blocking agent and the amount thereof used are selected according to the composition of the black liquor circulating in the evaporation system. Its use is not expected in a sugar factory evaporator.

The method for preventing sedimentation according to the present invention is applied to the concentration of sugar liquid in a sugar factory, and the pulp is produced at a ratio of 5 to 15 g of the product solid per ton of sugar cane or sugar beet passing through the factory. In the industry 25 to 50 g of product solids per ton of black liquor solids
It requires a compounded composition to be added at a ratio of.

The addition of the compounded composition can be carried out at any point in the evaporation system, and immediately prior to this step, but preferably the composition is in a pre-evaporator, or Add at the inlet of the evaporation tower of 1. If the properties of the system are required, it is recommended that the composition be added at two points, in which case some addition of the product may be added in the first working column or in the pre-evaporator. It is common to carry out the supplemental addition of the composition in the working column before or at the end of the last of the system.
In this case, the product added at the two points may also have a different composition which is suitable for the composition of the sugar or black liquor mineral matter.

The process according to the invention is described below: 40.0 to 60.0% by weight of water under vacuum in a preparative nitrogen-purged reactor with mechanical stirrer, equipped with cooling and heating coils. , 10.0 to 25.0
% By weight of functional monomer, eg 2-acrylamido-2-
Methylpropanesulfonic acid and its salts, 2-methacrylamido-2-methylpropanesulfonic acid and its salts, 3-
Allyl-1-oxypropylsulfonic acid and its salts, or other monomers such as 3-allyloxy-
1,2-dihydroxypropane and 3-allyloxy-2-hydroxypropane monophosphate, 0.05 to 0.45% by weight
Mercaptoalkanoic acid, for example mercaptopropionic acid, and 8.0 to 18.0% by weight of (meth) acrylic acid are added, then under stirring and under a stream of nitrogen,
Start heating at a temperature of 75 to 100 ° C.

-0.03 to 1.45% by weight of alkali metal or ammonium persulfate and 2.0 to 10.0
A mixture containing 1% by weight of water under reflux at a constant flow rate 1
Add to reactor in time.

-Reflux to 1 after this addition is complete
Hold for a period of time and cool the mixture to a temperature of 40 to 50 ° C.

-Next, at a temperature of 40 to 60 ° C, 45
Start adding 5.0 to 20.0 wt% caustic soda over 60 minutes. At this stage,
Correct the pH to 6.0-11.0.

-After this addition is complete, increase the temperature to 60
To 70 ° C for 2 hours and then mix this mixture for 30 hours.
Cool to a temperature of ℃; then adjust the solids to
Check pH.

-Then addition of 0.0 to 15.0% by weight of sequestering agent or mixture of sequestering agents, for example EDTA-ethylenediaminetetraacetic acid or its salts, NTA-nitrilotriacetic acid or its salts, DTPA-diethylenetriaminepentaacetic acid or its salts. Start.

In this way, the anti-deposition agent composition which is the subject of the present invention is obtained.

The invention and the results of its application will be further described with reference to the following examples, which do not limit its scope.

[0072]

【Example】

Example 1 a) 357.0 kg of water, 133.0 kg of 2-acrylamide-
2-Methylpropanesulphonic acid, 1.54 kg of 3-mercaptopropionic acid and 70.0 kg of acrylic acid are charged to the reactor and then heating is started at a temperature of 95 ° C. under stirring and nitrogen flow. b) A mixture containing 5.46 kg ammonium persulfate and 35.0 kg water is added to the reactor under reflux and constant flow over 1 hour. Reflux is maintained for 1 hour after the addition is complete and the mixture is cooled to a temperature of 45 ° C. Then 98.0 kg of 50% caustic soda are added at a temperature of 50 ° C. over 45 to 60 minutes. After the addition is complete, the temperature is maintained at 65 ° C for 2 hours, then the mixture is cooled to a temperature of 30 ° C.

C) In this way it has the appearance of a clear yellow liquid, pH in the range 9.5 to 10.5, 0.245
An anti-sedimentant composition which is the subject of the present invention is obtained, which has an intrinsic viscosity of dl / g and a solids content of 25%.

Example 2 A method and composition similar to Example 1 except that the monomeric 2-acrylamido-2-methylpropanesulfonic acid was replaced with sodium 3-allyloxypropyl sulfonate in step a). Under conditions.

In this way, an antibacterial composition which is the subject of the invention, has the appearance of a clear yellow liquid and has a pH of 6.5 to 7.0, an intrinsic viscosity of 0.12 dl / g and a solids content of 25%. Deposition agent is obtained Example 3 As shown in Fig. 2, it is used for the concentration of sugar liquid in a sugar factory.
A test was conducted to evaluate the performance of the anti-deposition composition of the present invention in a pilot system of a two stage tower evaporator.

For this purpose, the system was fed with 6,000 l of simulated water having the following composition: CaCO ₃ 2,588.0 g Na ₂ SO ₄ 1,457.0 g Na ₂ SiO ₃ 597.0 g FeSO for 1,000 l of water. ₄ 75.4 g MgSO ₄ 545.0 g In 4 days, this solution was concentrated 4 times in each evaporation without leaving in the second working column.

The pH of the solution in the feed reservoir was controlled in the range of 6.0 to 7.0.

Water may be present in the second working column at 35 to
It was heated to 80 ° C and in the first working column to 55 to 104 ° C.

Six SAE 316 having the following dimensions
A test piece (cylindrical) made of stainless steel was used. The length was 445.0 mm, the inner diameter was 44.5 mm, the wall thickness was 1.77 mm, and it was installed inside the evaporator at the height of the tube bundle.

Four programs for anti-deposition, P ₁ , P ₂ , P ₃ and P _4, were evaluated; a blank test was also performed without addition of anti-depositant composition for comparison: P
₁ = 3.0 mg / l of polyacrylic acid ester having a molecular weight of about 2,000.

P ₂ = 15.0 mg / l silicon-containing polyacrylic acid ester.

Both the composition of Example 2 with P ₃ = 3.0 mg / l and the composition of Example 1 with 4.5 mg / l were used together.

The composition of Example 2 with P ₄ = 4.5 mg / l.

The results obtained are shown in Table 3 below, which shows the evaluation of four treatment programs for the prevention of deposition.

Table 3 Product Average Weight Deposited Per Specimen (g) Blank Test 9.90 P ₁ 0.35 P ₂ 1.33 P ₃ 0.53 P ₄ 0.24 Test P ₁ and P ₂ deposits are larger than others It showed hardness.

Tests The deposits of P ₃ and P ₄ were the softest.

The best performance was given by method P ₃ due to the low amount of deposits and the low hardness of the deposits, confirming the ability of the present invention to prevent salt deposits. ing.

Next, FIG. 2 shows a simplified diagram of the pilot system of the two-stage working tower evaporator, (10) of which is the evaporator,
(20) is a heat exchanger and (30) is a test piece.

Various characteristics of the evaporator: Pressure = within 3 kg / cm ² Temperature = Maximum 150 ° C Vacuum = Maximum 64 cmHg Capacity = 280 l (for each body) Flow rate = Maximum 250 l / h Length = 2.5 m Diameter = 500 mm Exchanged area = 3 m ² (for each body) Material = 316 L stainless steel Example 4 In order to evaluate the effect of the product on the processing of black liquor in the pulp industry, the same conditions as in Example 3 were used. Other tests were conducted below.

In this example, the pH of the solution in the feed reservoir was adjusted to 11.0 to 12.0 depending on the practical application.
Controlled to the range of.

The analysis of the deposits in the second working tower is
As shown in Table 4, the following aspects were shown when applying the included treatment methods.

Table 4 Deposition (%) Product CaSO ₄ CaCO ₃ SiO ₂ Blank Test 35.7 21.7 29.5 P ₃ 42.5 25.5 12.0 P ₄ 15.0 6.5 20.4 Table 4 above shows the deposits obtained from P ₃ and P ₄ treatments. Has a lower silica content than the blank test sample, indicating the lower hardness obtained using this treatment program.

The amount of deposit formed is shown in Table 5 below, which is an evaluation of two treatment programs for deposit control. Table 5 Average weight (g) of product deposited on each test piece Blank test 0.56 P ₃ 0.20 P ₄ 0.18 From these results, it was found that methods P ₃ and P ₄ gave a small amount of deposit and a small hardness of the deposit. It can be concluded that it is shown and confirms the ability of the anti-deposition agent which is the subject of the present invention.

Example 5 To 50 kg of the composition of Example 1 is added 41.5 kg of the composition of Example 2 followed by 3.2 kg of the sodium salt of nitrilotriacetic acid with stirring. Stir for 30 minutes until the dissolution of each component is completed. Then 5.3 while still stirring
kg of sodium hydroxide is added to bring the final mixture to a neutral pH for ease of handling. The above composition has a solid dissolved in 31% water. This was continuously treated for 60 days in a weak black liquor that entered the multi-stage tower evaporator system, with a solid content of 46 to 50 per ton of solids in the liquid.
It was added in the ratio of g.

The following scheme, FIG. 3 and Table 6 show the main characteristics of the system which is the subject of this study.

Table 6 Working tower Number of tubes Area (m ² ) 1A 740 999 1B 792 1,068 Steel: ASTM A-249 2 1,101 1,486 Nominal diameter: 2 "3 781 1,054 Pitch: Triangle 4 1,004 1,353 L: 8,475 mm 5 1,283 1,732 Figure 3 above shows a schematic of a six-stage working tower evaporator system, the characteristics of which are as follows: Feed liquid temperature = 73 ℃ to 93 ℃ Working tower 1A temperature = 120 ℃ to 130 ℃ Heating flow temperature = 143 ° C to 148 ° C Feed liquid flow rate = 4,000 to 4,700 l / min Evaporators 1A and 1 considered to be single-action towers during the test
The total heat exchange coefficient of B was followed. The calculation was based on the flow rate, the assumed concentration and temperature of the black liquor at the inlet and the outlet, and the temperature of the heating system.

The deposition rate of calcium in the working towers 1A and 1B was also measured along the test through the analysis of the liquid in the system at the inlet and outlet and the measured flow rate. This was chosen because calcium is the major deposited metal.

Next, Table 7 shows a set of evaporators, a working tower 1
Shows the typical composition of the feed at the inlet of the system consisting of A and 1B, and at the outlet of this set of evaporators,
Table 8 shows typical analytical values of deposits obtained at the end of the evaporation trials in working columns 1A and 1B.

Table 7 Sediment (%) Calcium Magnesium Silica Iron Aluminium Soluble Nium Object Device (mg / l) (mg / l) (mg / l) (mg / l) (mg / l) (%) Fourth Action tower 144.40 23.42 619.02 8.13 16.17 17.31 inlet acts tower 1B 272.28 49.78 1042.62 19.53 42.73 36.91 inlet acts tower 1A 322.50 63.58 1196.47 23.15 54.42 45.13 exit table 8 acts tower 1A 1B analysis (%) silica (SiO ₂₎ 5.2 5.3 potassium (K ₂ O) 2.3 1.3 Calcium (CaO) 33.2 35.3 Magnesium (MgO) 2.9 3.7 Iron (Fe ₂ O ₃ ) 2.0 2.0 Aluminum (Al ₂ O ₃ ) 1.1 0.2 Sodium (Na ₂ O) 2.0 1.3 Loss at 525 ° C 12.3 10.4 1000 loss at ° C. - 525 loss 32.2 32.3 the composition of the schematic (%) at _{℃ 1A 1B CaCO 3 62.8 64.3 MgCO} 3 · 3H 2 O 10.6 13.0 iron _{7.7 5.9 Al (OH) 3 1.8} 0.4 silicate 5.5 5.4 organics 0 0 Other 11.6 11.0 Body tracking heat exchange coefficient (U), and calcium deposition rate (Rd) was performed is applied non first 60 days of the trial.

The average heat exchange coefficient in the first 60 days in these two trials (14 measurements for trials without anti-deposition agent and 16 measurements for trials with the compound described in this example) was: Trial without addition of anti-deposition agent: U = 345.4 kcal / hour m ² ° C-Trial with anti-deposition agent: U = 499.4 kcal / hour m ² ° C.

The calcium deposition rate results shown during the trials with the addition of the anti-depositor compound described in this example are:
The average rate is 45.5 g calcium / min. In previous trials with no addition of product, the deposition rate was significantly higher, with an average notation of 77.2 g calcium / min for the first 30 days and 58.6 g calcium / min for the last 30 days. Changes have occurred.

FIG. 4 below shows the results obtained in more detail.

The overall average of trials without anti-deposition agent is 67.
9 g calcium / min.

According to these measurements, the calculation of the amount of dry solids passing through the system during the same period was calculated as 1.080 tonnes in the trial with the anti-deposition agent of the present example. It gave a larger result of 1.154 tons / day compared to the daily rate.

[Brief description of drawings]

FIG. 1 is an illustration showing a simplified scheme of an evaporator system according to the present invention.

FIG. 2 is an illustration showing a simplified schematic of a pilot system for a two-stage working tower evaporator for testing anti-accumulation agents.

FIG. 3 is an explanatory diagram showing a schematic diagram of a six-stage working tower evaporator system according to the present invention.

FIG. 4 is a chart showing changes in the amount of deposits with and without the use of the anti-deposit agent according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Monica Corato, State of Sao Paulo, Brazil, Sao Paulo Department 93-See Rua Herikichiaves 291

Claims (6)

[Claims] 1. An antisediment mixture is: a) 0.0 to 50.0%, preferably 0.0 to 15.0%, of a sequestrant or sequestrant mixture, for example: E, based on solids content.
DTA-ethylenediaminetetraacetic acid or its salt, NT
A-nitrilotriacetic acid or a salt thereof, DTPA-diethylenetriaminepentaacetic acid or a salt thereof, and b) 50.0 to 100.0%, preferably 85.0 to 100.0%, based on the solid content of 50.0 to a molar ratio.
95.0%, preferably 65.0 to 90.0% monomer
I; Monomer I: 0.0 to 35.0%, preferably 20.0 to 35.0
% Of the following monomer II; monomer II: And 0.0 to 35.0%, preferably 10.0 to 25.0% Monomer III; Monomer III; In each of the above formulas, R ₁ and R ₂ are hydrogen or a methyl group; X ₁ and X ₂ are an alkali metal or hydrogen; Y is a hydroxyl group (—OH), a monophosphate group (—P (O ) (O
H) ₂ ), or a terpolymer or copolymer or a mixture of polymers, wherein X ₃ is a sulfonic acid group (—SO ₃ X ₃ ) in which X ₃ is an alkali metal or hydrogen. A method and a process for preventing the deposition of sugar liquor in a sugar mill and in a vaporizer for the concentration of black liquor in the pulp industry, characterized in that 2. A polymer having a molecular weight of 15,000 or more.
Method for preventing deposition in a vaporizer for concentrating sugar liquor in a sugar mill and black liquor in the pulp industry according to claim 1, characterized in that it is in the range 65,000, preferably in the range 15,000 to 25,000. And preventive steps. 3. A mixture of the above components a and b can be used at any solids concentration, but the most reasonable use is 5.0 of the product in water.
1 to 2 characterized by the fact that it is such that it gives an aqueous solution having a concentration of 5 to 50.0%.
Methods and steps for preventing deposition of sugar liquor in the sugar mill described and in the evaporator for the concentration of black liquor in the pulp industry. 4. The composition containing the above composition is applied to the concentration of sugar liquid in a sugar factory for the concentration of about 5 to 5 parts of solids of product per ton of sugar cane or sugar beet.
For application in the pulp industry for concentration of black liquor, 15 g of product solids per ton of black liquor 15 to
A method for preventing and preventing the deposition of sugar liquor in a sugar mill according to claim 1 and 2 in an evaporator for concentrating black liquor in the pulp industry, characterized in that it is added in a proportion of 50 g. Process. 5. It acts mainly through the mechanism of salt dispersion and crystal modification, and also acts on the entire spectrum of salts found in the sugar liquor of sugar cane and sugar beet or in the process of concentrating black liquor. A method and a process for preventing deposition in a vaporizer for concentrating sugar liquor in a sugar mill and black liquor in the pulp industry according to claim 1, which provides advantages. 6. Sugar production according to claim 1, characterized in that the administration of the formulated composition is achieved at any point of the evaporation system or at a stage immediately before this process. Methods and processes for preventing deposition in evaporators for the concentration of sugar liquor in mills and black liquor in the pulp industry.