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X-concentrate grade when adding PEO-1; â—‹-concentrate grade when adding PEO-1 [next]
Adjusting foam to reduce fuel oil consumption during phosphate flotation
Quoted from: R·Snow et al
Introduction
Long chain fatty acids used in the flotation industry undergo an ionization process in the pH range of 4 to 0. At a pH of about 8, a fatty acid ion-molecular complex (RCOOH-RCOO-) with a ratio of 1:1 will be formed. Within this pH range, these surfactants clearly play a dual role of collector and frother, this phenomenon tends to produce excessive phosphate flotation foam, and the current common practice to add a large amount of fuel Oil to reduce foam.
Non-polar hydrocarbon oils play an important role in flotation. Florida phosphate industry about a year spent about 1.5 billion pounds of fuel oil, which is No. 5 fuel oil and more oil or coal oil. One of the effects of these oils is to significantly increase the contact angle between the mineral and the bubbles, thereby accelerating the kinetics of the reaction, making large particle flotation possible. These are all due to the strong adhesion of individual ore particles to the bubbles, or the combined flotation of air-mineral-fuel oil aggregates and individual ore particles. Fuel oil and kerosene can also be used as solvents for tal oil fatty acids and fatty amines. Easy to use. More importantly, they also increase the floatability of the collector. Fuel oil also plays an important role in controlling foam performance. Nevertheless, according to Gruber et al., fuel oil did not play an important role in accelerating the adsorption rate of oleate on phosphate minerals. The study also found that, when using the mineral water plant, the fuel oil will promote fatty acid adsorbed on the silica surface.
Industrially, an excessive amount of fuel oil is used to control the foam. At present, two technologies are mainly used to defoam. That is, either by neutralizing the surfactant that forms the foam, or by finding a substitute for the surfactant to defoam. Thus, the addition of a suitable metal ion and the anionic surfactant form insoluble metal salt can effectively suppress generation of foam, this time, no alcohol nonionic polyoxyethylene surfactant is present in the system. It is also effective to add an oppositely charged surfactant which forms an insoluble precipitate with the foam-forming surfactant or which forms a very low residual concentration of mixed micelles. Insoluble fatty acids, alkyl phosphates and alkylamine compounds can all function in this manner.
The second method of eliminating the surface elasticity of the bubble relies on the exclusion of the adsorbed surfactant from the interface with an almost insoluble oil film. Silicone resins and perfluorocarbon oils are very effective suds suppressors if they are dispersed in an aqueous solution with or without a diluent. [next]
Although the current concentrating plant is using a large amount of fuel oil to control the foam, it still faces the problem of excessive foaming in many concentrating plants and causes a large amount of fatty acid waste. Fuel oil is unlikely to be the most effective in removing phosphate flotation foam. The addition of small amounts of additives or commercial defoamers can significantly reduce the amount of fuel oil used. Since fuel oil is not as biodegradable as other flotation agents (such as fatty acids and amines), excessive use of fuel oil not only causes economic losses, but also causes environmental problems.
The first step in the research project was to discuss the comparison of various petroleum derivatives as foam conditioners/auxiliary collectors in the Florida phosphate anion roughing. Next, the potential value of rosin oil as a partial replacement for some petroleum derivatives was determined, and as a result, these agents reduced the pollution of the floating water.
Fuel oils, including No. 5 oil, reclaimed oil and Bunker C oil/diesel blends, have been commonly used to control foam characteristics and increase the "traction" of the Tar oil collector. These petroleum derivatives currently cost about $0.04 to $0.07 per pound (in large quantities). The use of cheaper pharmacies as a partial replacement for petroleum products is a challenging task because effective alternatives not only inhibit excess foam but also do not use additional harvesting in rough selection. The agent can not reduce the "traction".
If a more expensive alternative agent (or combination of agents) enhances the collector's ability to capture without adversely affecting flotation selectivity, the resulting phosphate recovery can be improved. All processing costs. For example, replacing sodium fuel with sodium silicate and rosin oil can improve foam characteristics and improve the grade of the rough concentrate (feedstock of the amine flotation circuit), thereby increasing the recovery of the roughing loop and the amine flotation (select) loop. .
The rosin oil can be prepared from natural rosin or tall oil rosin acid de-smoothing base. It is generally a mixture of cyclic hydrocarbons and unequal amounts of impurities. When produced from tall oil of terpineic acid, the rosin oil contains some fatty acids and unreacted pine acid. The rosin oil used in this test was produced many years ago by Westvaco and has an acid number of 50. [next]
1 test
1.1 Flotation feedstock
Three flotation feedstock samples are currently used in laboratory tests. These samples were labeled as ore samples A, B and C, respectively. Table 1 gives the analysis results of the feed samples. Mineral samples A and B mainly contain brown phosphate, while mineral sample C mainly contains black phosphate. The B-mine sample - 200 mesh "mud" content is 4 times that of the A and C mineral samples.
Table 1 Analysis of three sample samples
Sample
solid(%)
P 2 O 5 content (%)
Insoluble content (%)
A
B
C
92.0
82.8
83.8
10.12
7.82
4.26
69.19
75.67
86.62
1.2 Evaluation of flotation reagents
The coarse selection of the A sample uses NH3 as the pH adjuster and 11 different hydrocarbon base oils as the foam regulator. The crude selection of the ore sample B and the sample C was adjusted using sodium carbonate to adjust the pH value, and two kinds of Tal oils produced by Liqro GA Co., Ltd., which had been used in the past, were used as the foaming agent for the mineral sample A flotation. In the flotation tests of mineral samples B and C, N-Brand sodium silicate was used to increase flotation selectivity and improve foam characteristics. Table 2 lists the specific gravity and price of the foam conditioner used in the A sample test. Table 3 exemplifies the foam modifiers of the alternative fuel oils evaluated in the test.
Table 2 Petroleum additive test results
Product
Specific gravity
Price/dollar·pound -1
Product
Specific gravity
Price/dollar·pound -1
mineral oil
Kerosene
Diesel oil
White mineral oil
No. 5 oil
PCS fuel oil
0.75
0.81
0.86
0.88
0.89
0.91
0.248
0.074
0.063
0.381
0.049
no data
IPC fuel oil
Buker C fuel oil
Philflo fuel oil
Rosin oil
oil
0.92
0.96
0.98
0.98
0.84
0.060
0.033
0.140
0.300
0.425
2 results and discussion
2.1 Evaluation of rosin oil and petroleum derivatives
2.1.1 Comparison of various hydrocarbon foam conditioners
In the laboratory flotation test, the N play amount is 0.70 to 0.86 lb / / t, and the pH value is 9.0 ~ 9.2. The slurry solid concentration is 74%-75%, the pulping time is 2min, and the mineral sample A ore dressing flotation uses NH 3 to adjust the pH value. The amount of Tal oil A is about 1.1 lb / / t, the amount of 11 different hydrocarbon base oil conditioning agent is 0.4 or 0.6 lb / t (foaming agent: Tar oil A ratio of 0.4: 1.0, additional foam Conditioner: The ratio of Tal oil A is 0.6.1.0). Tap water was used for all tests. Figure 1 visually shows the recovery of P 2 O 5 for each agent in a histogram. From the results of Figure 1, PCS fuel oil, IPC reclaimed oil, Coastal #5 fuel oil and diesel oil are the most effective foam conditioners from the point of view of cost indicators; and from the recovery index, white mineral oil and West -vaco rosin oil is also very effective. Nonetheless, their higher unit price will limit their ability to completely replace fuel oil in flotation plants.
Table 3 Test foam regulator
Product
Specific gravity
Price/dollar·pound -1
Product
Specific gravity
Price/dollar·pound -1
No. 5 fuel oil
Rosin oil
Tributyl citrate
P-400 polyethylene glycol
0.88
0.98
0.97
1.01
0.049
0.300
1.800
1.060
Mazu DF
160-17 oil
CC6983-16A oil
CC6983-16B oil
1.02
101
0.98
3.35
no data
no data
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Figure 1 Recovery of flotation sample A using different foam conditioners
Adjuster dosage: â–¡-0.6 lb/t; â– -0.4 lb/t
When the laboratory flotation test does not use a foam conditioner, the flotation results obtained are very poor. There are two indicators of foam regulators (Philflo oil and Westvaco rosin) containing cyclic hydrocarbon oils. Additional flotation tests have shown that replacing some of the fuel oil with rosin oil is considered to be highly desirable. [next]
2.1.2 Effect of rosin oil
Four petroleum-based rosin oil foam regulators were selected to replace the fuel oils (diesel, PCs fuel oil, Coastal #5 fuel oil and IPC reclaimed oil) for flotation tests. 0.2 lb/t of Westvaco rosin + 0.4 lb/t of fuel oil replaces 0.6 lb/t of fuel oil. The results of the flotation test comparison are shown in Figure 2. The test results show that when 1/3 of rosin oil is used instead of petroleum-based modifier, the flotation recovery of concentrate P 2 O 5 is increased by 1.3% to 5.5%; meanwhile, the concentrate insoluble content is increased by 0.95%~ 7.89%. In the flotation, the use of some rosin oil ensures that the foam is stable for at least 2 min, thus increasing the recovery of concentrate P 2 O 5 . The presence of some fatty acids and rosin acids in commercial rosin oil (acid number = 50) is also a cause of the high recovery of concentrate P 2 O 5 .
Fig. 2 Effect of rosin oil on the A index of different oil flotation samples
â–¡-0.6 lb/t oil; â– -0.4 lb/t oil +0.2 lb/t rosin oil [next]
In order to further evaluate the potential of partial replacement of fuel oil by rosin oil, three exploratory flotation experiments were carried out with mineral sample B. Sodium carbonate was added (amount of 0.84 to 1.44 lbs/t) to adjust the pH to 9.0 to 9.2. In addition to the last test, Liqro GA Tal oil collector (1.0 lb/t) was used. As can be seen from Figure 3, rosin oil also improved the recovery.
Figure 3 Effect of rosin oil on flotation recovery of ore sample B
It should be noted that if only rosin oil (plus sodium silicate) is used as the foam conditioner, although the selectivity of the flotation is good, the P 2 O 5 recovery rate and the flotation rate are lowered. If only all of the foam conditioner is replaced by Tal oil (1.8 lb/t), not only is the foam too much, but the concentrate recovery rate is low. [next]
In order to further evaluate the application possibilities of rosin oil as a foam regulator in the black phosphate ore flotation in southern Florida, eight flotation tests were performed on the sample C. Add sodium carbonate (amount of 0.80 to 1.32 lb / / t) to adjust the pH of 9.0 ~ 9.2. In addition to the last test, Liqro GA Tal oil was used as a collector at a rate of 1.0 lb/t. In some tests, 0.4 lb/t sodium silicate was also added. The feed and PCS and Cargill fuel oil slurry and flotation parameters were applied again in the test.
When using No. 5 fuel oil (amount of 0.6 lb / / t) without adding sodium silicate, the flotation selectivity is poor. When sodium silicate is present, the selectivity is greatly improved. Fuel oil (0.6 lbs/t), rosin oil (0.2 lbs/t) and sodium silicate (0.4 lbs/t) work best together in terms of total concentrate grade/recovery. The results of the flotation concentrate obtained from this low grade ore were as follows: P 2 O 5 grade 29.67%, insoluble content 13.19%, P 2 O 5 recovery rate 90.6%.
2.1.3 Flotation observation phenomenon and comments
Rosin sour soap (rosin soap) was used as a Florida phosphate industry collector for many years. The indicators obtained with it are not good and usually produce bulky foam. In this test, rosin oil was used instead of 1/4 to 1/3 of the fuel oil to produce a good flotation foam which was maintained during the 2 min test. This may be due to the interaction between rosin oil, fuel oil, tar oil and sodium silicate, which affects the flotation rate and foam characteristics, but the specific reasons are not fully understood. In local phosphate flotation plants, the use of sodium silicate not only improves the selectivity of flotation, but also speeds up flotation and improves foam characteristics.
In the fractionation plant for the production of Tal oil, it is an interesting idea to develop an industrial flotation phosphate mineral collector by a method of directly removing the high-grade turpentine oil vapor. Since the collector contains fatty acid and rosin oil and a small amount of rosin acid, only a small amount of fuel oil is required for the phosphate flotation. We are still not sure about the economics of producing such collectors. At present, we do not even know whether the process of deamination can be carried out when the raw material to be processed contains a large amount of fatty acid. If this is not possible, a mixture of fatty acid and rosin oil will be produced in the fractionation plant, which is undesirable. If we can find a flotation manufacturer that needs our help, we are willing to discuss the practicality of this method with the chemists at the Tar Oil Fractionation Plant. [next]
2.2 Using foam conditioner as a partial replacement for fuel oil
The flotation test discussed in the first part demonstrates that fuel oil No. 5 is the most viable foaming agent and additive for fatty acid flotation phosphate when considering both flotation index and cost; the test also showed that it partially replaced No. 5 fuel oil. It is possible to obtain the same or better phosphate recovery at this time. This part of the research focused on how to optimize the partial replacement of No. 5 oil, especially with rosin oil.
In addition to No. 5 fuel oil and rosin oil, five kinds of foam conditioners were used in the laboratory to replace about 25% of No. 5 fuel oil for flotation test. In addition to the foam regulator, the conditioner has a pH adjuster (sodium carbonate) and a phosphate collector (Liqro GA TO and No. 5 fuel oil). For ease of comparison, the foam-adjusting surfactant was also added to the flotation water in the following flotation test. The current prices of the various foam conditioners tested are listed in Table 3. The foam modifiers listed are all soluble in kerosene (1 part of the agent: 4 parts of kerosene). Except for CC6983-16B, the solubility of other agents in water is very small, even almost insoluble. This surfactant forms a stable milky emulsion in water. Two industrial surfactants are condensates of the tal oil fatty acid with 5 or 8 moles of ethylene oxide.
2.2.1 Different surface active foam conditioners partially replace No. 5 fuel oil
The flotation recovery of some foam regulators instead of fuel oil is shown in Figure 4. The figure also shows the results of adding the foam conditioner to the agitation tank and the flotation tank.
All experimental ore samples were used in an amount of 500 g (dry) and slurried for 2 min at 75% solids. Except for the slow flotation rate of tributyl phosphate, the flotation time was 3 min, and the other experimental flotation time was 2 min. In all tests, the amount of Tal oil collector and No. 5 fuel oil was 1.0 and 0.6 lb/t, respectively, and the amount of sodium carbonate was 0.84 to 0.92 lb/t. The pH was adjusted to 9.0 to 9.2, and the amount of foam regulator was 0.2 lb / t, equivalent to the concentration of the modifier in the flotation slurry is 20·10 -6 . [next]
The data in Fig. 4 shows that in 14 tests, the recovery of concentrate P 2 O 5 obtained by flotation was 92.6% to 97.0%, and the P 2 O 5 grade was 16.98 to 27.75%. All foam conditioners achieved satisfactory phosphate recovery. The characteristics of flotation foam are different, some are very good, and some are too much foam. Flotation requires a very long flotation time when using tributyl phosphate. Adding a condensate of Tal oil to ethylene oxide to the slurrying stage produces excessive foam. Using MazuDF160 silicone, Dow P-4000 polyethylene glycol, Westvaco rosin oil and No. 5 fuel oil produced the best foam characteristics. It is worth noting that the foam properties of some surfactants vary depending on whether they are added directly to the slurry tank or to the flotation slurry.
Figure 4 Effect of the type of foam conditioner and the point of addition on the recovery rate â– Add to the flotation cell; port - add to the paddle [next]
3.2.2 Effect of rosin oil addition
In the four trials, the rosin oil was added to the pulping stage at a rate of 0.0, 0.1, 0.2 and 0.4 lb/t, respectively. The amount of Tal oil and fuel oil is fixed at 1.0 and 0.6 lb/t, respectively. The concentrate P 2 O 5 grade and the recovery average calculated from the standard deviation were not statistically different. In order to achieve a recovery of concentrate P 2 O 5 higher than 95%, the amount of rosin oil is at least 0.2 lb / t. The curve in Figure 5 illustrates this more clearly.
Fig. 5 Effect of rosin oil on the flotation results of ore sample B when Tal and No. 5 fuel oil are used at 1 and 0.6 lb/t
â– P205 grade of a concentrate; â—P 2 O 5 recovery rate of a concentrate [next]
2.2.2 Effect of sodium silicate dosage
In a set of flotation tests, three foam conditioners were selected to illustrate the improved selectivity and foam characteristics of 0.4 lb/t sodium silicate. As in previous experiments, Tal oil (0.6 lbs/t) and fuel oil (1.0 lbs/t) were used as standard collectors for phosphate flotation. Add sodium silicate to the last 20 s of the pulping stage. Other independent flotation variables are identical to previous flotation experiments.
The results show that the use of sodium silicate can increase the grade of P 2 O 5 in concentrates by 5% to 6%, and the recovery of concentrate P 2 O 5 by Westvaco rosin oil and Dow P-4000 is reduced by 2% to 3%; The use of sodium silicate plus human quantified CC6983-16B foam conditioner increased the P 2 O 5 recovery by 1%. Sodium silicate can significantly improve foam properties.
2.3 Foam adjustment of nonionic polymers
The flotation of coarse-grained phosphate minerals is more difficult due to the greater mass of the ore and the reduction in foam stability. Improvements in fluid dynamics (reducing turbulence), foam stability, and hydrophobicity of the surface of the particles all increase the flotation index. Despite many efforts, the flotation results of coarse-grained phosphates are still not satisfactory. Further research is needed to improve the flotation of coarse particles.
Surfactant PEO (polyethylene oxide) has been successfully used in deinking flotation and mineral flotation. It has been reported that PEO-modified foaming agents provide better flotation for coarse minerals. The purpose of this study was to evaluate the effect of using a nonionic polymer as a flotation aid with conventional anionic fatty acid or fuel oil collectors to increase phosphate flotation recovery.
2.3.1 Effect of PEO molecular weight
The test results show that several PEO polymers have achieved satisfactory results when used in combination with conventional fatty acid or fuel oil collectors. At this time, the grade of P 2 O 5 obtained by PEO is similar to that of PEO. More importantly, the test results indicate that the effect of PEO polymers is directly related to their molecular weight. When the molecular weight of the polymer is less than 1200 or more than 8,000, it does not significantly promote the recovery of P 2 O 5 . The most effective polymer has a molecular weight between 1200 and 8000, since PEO-1 is an industrial product and it gives the best flotation. Therefore, the following laboratory tests mainly use PEO-1. [next]
2.3.2 Impact of PEO Addition
The test results of flotation of coarse particles with PEO-1, fatty acid and fuel oil mixture (the amount of which is 500 g/t) are shown in Fig. 6. When only 500 g/t fatty acid and fuel oil are added (ie no PEO-1 is added), the phosphate concentrate has a P 2 O 5 recovery of only 20%; conversely, if 10% of PEO-1 is added, P 2 O 5 recovery rate can reach 80%-85%. When the amount of PEO-1 exceeds 20%, the P 2 O 5 recovery rate decreases slightly. If 500 g/t of 100% PEO-1 is added, there is no phosphate floating (Figure 6).
Figure 6 Effect of PEO-1 on the grade and recovery of phosphate concentrate
(Coarse feed. The total dosage of the agent is 500 g/l, fatty acid: fuel oil mass ratio is 7:3, PH 9)
The solid line is the recovery of concentrate P 2 O 5 and the dotted line is the grade of concentrate P 2 O 5 [next]
2.3.3 Effect of collector dosage when adding PEO-1
The results of the comparison between the addition of PEO-1 and the use of fatty acid and fuel oil flotation coarse particle feedstock are shown in FIG.
It can be seen from the figure that the amount of phosphate minerals floating is very limited when the amount of collector added is less than 700 g/t. Only fatty acids and fuel oils are used as collectors, and the recovery of concentrate P 2 O 5 is only 20% to 60%. As expected, PEO-1 facilitates phosphate flotation, which promotes phosphate recovery at lower levels of fatty acids and fuel oils. For example, with only 10% PEO-1 added, 85% to 90% phosphate minerals float when the collector is 500 g/t (in contrast, when PEO-1 is not added, only 60% phosphoric acid) Salt minerals are up); to achieve 85% flotation recovery, 1200g/t of traditional fatty acid and fuel oil collectors are required.
Figure 7 Effect of dosage and dosage of phosphate on P 2 O 5 grade and recovery of phosphate concentrate
(Coarse feed, 10% polymer, 90% fatty acid / fuel oil (7:3), PH 9)
â–¡- Concentrate grade when PEO-1 is not added; â–³- Concentrate recovery rate when PEO-1 is not added;
3 Conclusion
In phosphate flotation, some foam conditioners can replace 30% of fuel oil, of which rosin oil is the most promising. Its more expensive price can be offset by increasing the recovery rate.
The addition of a nonionic polymer (PEO-1) to the coarse-grained phosphate flotation reduces the amount of fuel oil by 50%. PEO-1 achieves this by increasing the contact angle, increasing foam stability, and promoting the dispersion of fatty acid collectors.
(Ye Guohua; Tong Xiong Li Changgen)
(051204)
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