Use of aqueous solution of organic ammonium carboxylate in preventing dusting of fine material and combination of an aqueous solution of organic ammonium carboxylate and fine material

Abstract

The invention relate to use of aqueous solution of organic ammonium carboxylate of formula (I): [NR.sup.1R.sup.2R.sup.3R.sup.4].sup.+n[R.sup.5(COO)].sup.−n, in which R.sup.1, R.sup.2, and R.sup.3 are selected from the group composing of hydrogen and methyl, R.sup.4 is a C.sub.1-C.sub.4-alkyl substituted with a hydroxyl group, R.sup.5 is hydrogen or methyl and n is 1, as a mist or drops in preventing dusting of fine material and in lowering the freezing point of said aqueous solution on the surface of said fine material or on the surface of dust particles obtained from said fine material by spraying said mist or drops onto fine material or onto dust particles obtained from said fine material to neutralize negatively charged dust particles or by changing negatively charged dust particles into positively charged dust particles, wherein said fine material is selected from the group composing of sand, crushed stone, stone powder, crushed expanded clay, or crushed expanded clay aggregate, crushed cement or concrete, cement or concrete powder, chopped organic material, minerals and metal powder.

Claims

1. A method to prevent dusting of fine material selected from the group consisting of sand, crushed stone, stone powder, crushed expanded clay, crushed expanded clay aggregate, crushed peat, wood powder, chopped wood, crushed cement, crushed concrete, cement powder, cement dust, concrete powder, concrete dust, chopped organic material, minerals, metal powder, metal dust, and any combination thereof, the method comprising: providing an aqueous solution of organic ammonium carboxylate of formula (I):
[NR.sup.1R.sup.2R.sup.3R.sup.4].sup.+.sub.n[R.sup.5(COO)].sup.−n,  (I), in which R.sup.1, R.sup.2, and R.sup.3 are independently selected from the group consisting of hydrogen and methyl, R.sup.4 is a C.sub.1-C.sub.4-alkyl substituted with a hydroxyl group, R.sup.5 is hydrogen or methyl, and n is 1, defining an average particle size of the fine material; and selecting average droplet size for application of the solution based on the defined average particle size such that when the average particle size is 125-25 μm, neutralizing negatively charged dust particles or changing negatively charged dust particles into positively charged dust particles is caused by applying said aqueous solution as a mist having an average mist droplet size less than 1.5 times of the average particle size onto the fine material or onto dust particles obtained from the fine material; and when the average particle size is more than 400 μm neutralizing negatively charged dust particles or changing negatively charged dust particles into positively charged dust particles is caused by spraying the aqueous solution as droplets having an average droplet size of 0.4-5.0 mm onto the fine material.

2. The method of claim 1, which additionally comprises controlling the hydrophobicity and the hydrophilicity of the fine material and dust particles obtained from said fine material which control is based on the concentration of ammonium carboxylate in aqueous solution of formula (I).

3. The method of claim 1, wherein the concentration of ammonium carboxylate in the aqueous solution of formula (I) to be sprayed onto fine material or onto dust particles obtained from said fine material is in the range of 1-50% wt, depending on the water content of the fine material or dust particles obtained from said fine material.

4. The method of claim 3, wherein the concentration of organic ammonium carboxylate in the aqueous solution of formula I is in a range of 1-10 wt-%, preferably in the range of 2-5 wt-%.

5. The method of claim 4, wherein the concentration of aqueous organic ammonium carboxylate of formula (I), is selected so, that after the aqueous solution of organic ammonium carboxylate of formula (I) has absorbed water from a surface of the fine material or dust particles obtained from said fine material a water content of the aqueous solution of organic ammonium carboxylate of formula (I) is 85 wt-% or less.

6. The method of claim 5, wherein the concentration of organic ammonium carboxylate of formula I present on the surface of fine material or dust particles obtained from said fine material is in a range of 1-10% wt-%, preferably in the range of 2-5 wt-%.

7. The method of claim 1, wherein a surface of the fine material or surface of dust particles obtained from said fine material is hydrophilic after application of the aqueous solution of organic ammonium carboxylate of formula (I).

8. The method of claim 1, wherein the aqueous solution of organic ammonium carboxylate of formula (I) simultaneously acts as a freezing point depressant.

9. The method of claim 1, wherein the aqueous solution of organic ammonium carboxylate of formula (I) contains distilled water only.

10. The method of claim 1, wherein the concentration of sodium, potassium, calcium and magnesium is 0 M in the aqueous solution of organic ammonium carboxylate of formula (I).

11. The method of claim 1, wherein the aqueous solution of organic ammonium carboxylate of formula (I) is additionally admixed with compounds selected from the group comprising glycols, preferably ethylene glycol or propylene glycol, glycerols and viscosity modifying polymers, so that said aqueous organic ammonium carboxylate composition contains 5 to 97.5 wt-% of water.

12. The method of claim 1, wherein the aqueous solution of organic ammonium carboxylate of formula (I) is additionally admixed with auxiliary substances such as additional corrosion inhibitors, biocides, fragrance(s), coloring agents, surfactants, and viscosity intensifiers, so that the concentration of auxiliary substances is in a range of 0.001 to 10 wt-% from the total weight of aqueous solution.

13. The method of claim 1, wherein the aqueous solution of organic ammonium carboxylate of formula (I) contains formic acid, acetic acid and monoethanolamine or trimethylmonoethanolamine.

14. The method of claim 1, wherein 1.0 to 1.5 liters of the aqueous solution of organic ammonium carboxylate of formula (I) is used per 1000 kg of crushed stone.

15. The method of claim 1, further including a step wherein the aqueous solution of organic ammonium carboxylate of formula (I) is prepared by diluting, in situ, concentrated solution of water and organic ammonium carboxylate of formula (I) with water, in which concentrated solution the concentration of organic ammonium carboxylate of formula (I) is 50 wt-% or 85 wt-%.

16. The method of claim 1, further including a step wherein the aqueous solution of organic ammonium carboxylate of formula (I) is prepared by mixing, in situ, an aqueous solution of 1-5 wt-% of amine with an aqueous solution of 1-5 wt-% of acid.

17. A neutral combination of mist or drops of aqueous solution of organic ammonium carboxylate of formula (I):
[NR.sup.1R.sup.2R.sup.3R.sup.4].sup.+.sub.n[R.sup.5(COO)].sup.−n,  (I), in which R.sup.1, R.sup.2, and R.sup.3 are selected independently from the group consisting of hydrogen and methyl, R.sup.4 is a C.sub.1-C.sub.4-alkyl substituted with a hydroxyl group, R.sup.5 is hydrogen or methyl and n is 1, and fine material selected from the group consisting of sand, crushed stone, stone powder, crushed expanded clay, crushed expanded clay aggregate, crushed peat, wood powder, chopped wood, crushed cement, crushed concrete, cement powder, cement dust concrete powder, concrete dust, chopped organic material, minerals, metal powder, metal dust, and any combination thereof, wherein negatively charged dust particles have been neutralized or changed into positively charged dust particles by spraying the aqueous solution of organic ammonium carboxylate of formula (I) as a mist having average droplet size of less than 1.5 times average particle size of the fine material when the average particle size of the fine material is 125-25 μm, or as drops having average size of 0.4-5 mm when average particle size of the fine material is over 0.4 mm onto the surface of said fine material particles, or onto dust particles obtained from said fine material particles.

18. The neutral combination of claim 17, comprising drops of aqueous solution of organic ammonium carboxylate of formula (I) and fine material, wherein organic ammonium carboxylate of formula (I) will absorb water after water content of said aqueous solution have dropped at or below 15 wt-%.

19. The neutral combination of claim 17 wherein carboxylate originates from acetic acid, in form of fluid and having BOD (biological oxygen demand) of 0.64 mg of O.sub.2 at 20° C. for liter of said fluid in 5 days.

20. The neutral combination of claim 17, wherein carboxylate originates from acetic acid, in form of fluid, and having COD (chemical oxygen demand) of 0.64 mg O.sub.2 at 20° C. for liter of said fluid in 5 days.

Description

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(1) The invention is described below in greater details with the help of examples. Person skilled in the art will recognize that the properties of the compositions studied are such that they will make ideal mineral dust control aqueous solutions having also freezing point depressant properties for binding dusting of streets, ore mines, horse tracks etc.

(2) In the following non-restricting examples, we have presented some specific applications and properties of aqueous solutions comprising organic ammonium carboxylate of formula (I) as well as combinations comprising aqueous solution of organic ammonium carboxylate of formula (I) and fine material selected from the group composing of sand, crushed stone, minerals and metal powder.

Example 1

(3) An ionogenic solution for controlling mineral dust formation was prepared by mixing 1 mole of formic acid (99%) with 1 mole of monoethanolamine (99%). Distilled water was added to the fluid mixture in order to made 3-5% by weight aqueous solution.

(4) The freezing point of the solution was below −5° C., the electrical conductivity of the fluid was 61 mS/cm at 26° C., and pH of the fluid was 7.55 (measured directly from the solution).

Example 2

(5) An aqueous solution was prepared by mixing 1 mole of formic acid (99%) with 1 mole of monoethanolamine (99%). Distilled water was added to the fluid mixture in order to made 3-5 by weight solution in water.

(6) The freezing point of the solution was below −5° C., the Brookfield DV-I viscosity (20 rpm) was 10 mPas at −20° C., 10 mPas at −10° C., 10 mPas at 0° C., and Bohlin VOR viscosity (shear rate 23.1 1/s) was 4 mPas at 10° C., 3 mPas at 20° C., 2 mPas at 40° C., and 1.5 mPas at 60° C. The electrical conductivity of the fluid was 65 mS/cm at 26° C., and pH of the fluid was 7.54 (measured directly from the solution).

Example 3A

(7) Aqueous ammonium carboxylate solution mixture presented in examples 6 and 7 (below) was used in controlling dusting of crushed stone. This mixture comprises of ethanolamine in acetic acid and ethanolamine in formic acid (1:1). This mixture was sprayed as a 3-5% (w/w) aqueous solution in a form of mist or as drops onto surface of crushed stone and crushed stone dust. The sprayed mixture binds some moisture and prevented mineral dust and stone dust forming aerosol with surrounding air thus effectively preventing dusting by preventing forming charged dust particles. Additionally, it lowered freezing of mineral dust and crushed stone/stone dust.

(8) Crushed stone can be, for example, ore mineral originated from mining industry or rubble which have been gathered from town streets. Instead of above-mentioned mixture comprising ethanolamine in acetic acid and ethanolamine in formic acid, one can also use aqueous ammonium carboxylate solution from example 2 (monoethanolamine and formic acid) or cholineamine in acetic acid or cholineamine in formic acid.

(9) Committed peat material/peat dust and wood dust can also be treated in a similar way as crushed stone. Depending on the particle size of wood dust or committed peat/peat dust the aqueous ammonium carboxylate will be sprayed as a mist or as drops onto surface of peat/peat dust or wood dust. Ammonium carboxylate was sprayed as a 3-5% (w/w) aqueous solution. The concentration present in the surface of committed peat material/peat dust and wood dust cannot be measured exactly because water is evaporating from the surface of fine material or dust.

Example 4

(10) Aqueous ammonium carboxylate solution mixture presented in examples 6 and 7 (below) was used in controlling dusting of crushed stone (street rubble) in situ. For this reason, said aqueous ammonium carboxylate solution mixture was sprayed as drops onto pavement or city street. The concentration of ammonium carboxylate can be from 3% w/w up to 85% w/w calculated from the weight of the total aqueous ammonium carboxylate solution.

(11) The sprayed mixture bound moisture and prevented crushed stone dust from forming gas-solid-particle-aerosol with surrounding air by neutralizing charged crushed stone dust particles. Additionally, this mixture lowered freezing point of crushed stone dust particles. This melts ice and snow which otherwise would have formed on crushed stone.

Example 5A

(12) Aqueous ammonium carboxylate solution mixture presented in examples 6 and 7 or example 2 was used in controlling dusting of crushed stone gathered from town street (street rubble): crushed stone was immersed into aqueous ammonium carboxylate solution (ammonium carboxylate concentration was 3-5% w/w). After this treatment the crushed stone can be reused.

Example 5B

(13) Aqueous ammonium carboxylate solution mixture presented in examples 6 and 7 or example 2 was used as a concentrated solution 50% w/w or 85% w/w by immersing crushed stone into said aqueous ammonium carboxylate solution (immersion solution). The actual concentration of immersion solution changed continuously during the immersion treatment because the fine material absorbs different amount ammonium carboxylate and water. Actual concentration of immersion solution varied from 5% w/w to 85% w/w.

(14) After this treatment the crushed stone was applied onto frozen street. The ammonium carboxylate solution on the surface of crushed stone melted the ice and was diluted by means of melted water. After freezing crushed stone formed an excellent grit onto frozen street.

(15) Instead of crushed stone also expanded clay, or expanded clay aggregate can also be treated in a similar way. Expanded clay or expanded clay aggregate can be applied onto pavements in a similar way as crushed stone in city streets.

Examples 6 and 7

(16) Solutions in examples 6 and 7 have been made in the same way as presented in examples 1-2, that is, by mixing 1 mole of an ammonium cation source and 1 mole of a carboxyl anion source (unless otherwise shown) together for obtaining a concentrated fluid and then adding water to the concentrated fluid, for obtaining diluted solutions.

(17) TABLE-US-00001 TABLE 1 In table 1 has been shown formation of possible precipitates from fluids and diluted solutions obtained from fluids. Temperature was 20-25° C. fluid Wt-% from solution 100 90 80 60 40 20 5 pH of 2% Code/ex fluid solution EAE/6 ethanolamine/ Clear Clear Clear Clear Clear Clear Clear 6.8 acetic acid EAM/7 ethanolamine/ Clear Clear Clear Clear Clear Clear Clear 3.7 formic acid

(18) TABLE-US-00002 TABLE 2 The fluid and solution samples from selected examples of table 1 were subjected to chilling to a temperature of +4° C. and then to further cooling to a temperature of −20° C. In these temperatures the possible turbidity, precisipation of these samples was observed. ex 100 90 80 60 40 20 5 Temperature +4 C. 6 ethanolamine/ Clear Clear Clear Clear Clear Clear Clear acetic acid 7 ethanolamine/ Clear Clear Clear Clear Clear Clear Clear formic acid Temperature of −20° C. 6 ethanolamine/ Clear/ Clear/ Clear/ Clear/ Clear/ frozen frozen acetic acid liquid liquid liquid liquid liquid state state state state state 7 ethanolamine/ Clear/ Clear/ Clear/ Clear/ frozen frozen frozen formic acid liquid liquid liquid liquid state state state state

(19) As can be seen from table 1 and table 2 water-based solutions of organic of ammonium carboxylates are clear solutions independent whether they are diluted or not. This means that when they are used in controlling mineral dust, they have no tendency to salt out after sprayed onto surface of crushed stones, sand, soil or metal. Therefore, they do not interfere with, for example vehicle brakes or transport belts used in mining processes.

(20) TABLE-US-00003 TABLE 3 In table 3 has been given results from viscosity measurements compositions of examples 6 and 7. Viscocity was measured with Bohlin method (bold numbers) at shear rate 23.1 1/s and with Brookefield method (normal numbers) at shear rate 20 rpm. Additionally electrical conductivity, ph and redox potential was measured for these compositions comprising fluids and solutions prepared from these fluids by adding distilled water. Composition: fluid Wt-% monoethanolamine/ from solution 100 90 80 60 40 20 5 acetic acid water water wt-% 0 10 20 40 60 80 95 ° C. VISCO- Bohlin shear SITY VOR rate mPas viscosity 23.1 1/s Brookfield 20 rpm DV-I sp3 viscosity viscosity mPas/ −20 (repeat) >20000 >20000 12450 170 35 X X −20 >20000 16740 1700 80 20 X X −10 >20000 5150 700 60 15 10 5 0 27850 2160 330 40 10 10 5 10 15250 1152 210 23 6 2 1.7 20 5665 556 118 15 5 2 1.3 40 1220 154 41 8 3 1.5 1.1 60 345 63 20 5 2 1 0.7 conductivity mS/cm 0.534 2.24 7.1 25.9 46.9 47.8 20.2 T° C. 25.4 25.9 26 25.6 25.4 25.1 24.9 pH° C. 22 7.96 7.81 7.68 7.34 7.07 6.87 6.79 REDOX +31 +54 +69 +107 +146 +179 +216 Composition: fluid Wt-% monoethanolamine/ from solution 100 90 80 60 40 20 5 formic acid water water wt-% 0 10 20 40 60 80 95 pale oily light liquid ° C. VISCO- Bohlin shear SITY VOR rate mPas viscosity 23.1 1/s Brookfield 20 rpm DV-I sp3 viscosity viscosity mPas/ −30 −20 4350 680 230 30 10 X X −10 2830 410 130 20 10 5 X 0 1335 240 75 15 10 5 5 10 646 123 41 9 4 2 1.5 20 325 72 26 6 3 1.7 1.2 40 119 31 13 4 2 1.2 0.95 60 47 17 7 3 1.5 1.1 0.9 conductivity mS/cm 15.9 27.3 40.4 61 65 46.9 16 T° C. 26.1 25.9 25.8 25.6 25.5 25.5 25.8 pH/22° C. 7.75 7.67 7.6 7.55 7.54 7.53 7.51 REDOX potential −321 −244 −164 −110 −75 −48 +4

(21) As can be seen from table 3 the viscosity of compositions varies considerably depending on the quality of the fluid in a composition and fluid-solvent proportion (w/w). No solid crystals will be formed for instance if one uses combination ethanol amine/formic acid. Avoiding solid crystals is also a beneficial property for instance for an aqueous solution used for dust control.

(22) TABLE-US-00004 TABLE 4B The freezing points of selected aqueous solutions of organic ammonium carboxylate of formula (I), wherein R.sup.5 = H (formiate) is given in table 4B. Samples of organic ammonium carboxylate of formula (I) in water and their freezing points: Sample Concentration (wt-%) Freezing point (° C.) Water 0 0 HTF-20 20 −8.96 HTF-25 25 −12.44 HTF-30 30 −16.51 HTF-35 35 −20.13 HTF-40 40 −29.33 HTF-45 45 −39.48 HTF-50 50 −54.95 HTF-55 55 −63.01 HTF-60 60 −84.50

(23) As can be seen from tables 4A and 4B as the concentration of water solutions of organic ammonium carboxylate of formula (I) increases it will readily lead to lower freezing points. For example, those aqueous solutions of organic ammonium carboxylate of formula (I) presented in tables 4A and 4B having concentration about 10 wt-% have a freezing point about −5° C. However, when the concentration of organic ammonium carboxylate of formula (I) in the aqueous solution increases, the freezing point of the aqueous solutions falls considerably, for example when the concentration of aqueous solution is 30 (wt-%) the freezing point of said aqueous solution is about −20° C. When the concentration of aqueous solution is 60 (wt-%) the freezing point of said aqueous solution is about −85° C. The freezing point of −5° C. corresponds to the freezing point of aqueous solutions of organic ammonium carboxylate of formula (I) which are ready-to-use (1-7 wt % aqueous solution). The freezing point of −30° C. and −85% corresponds the freezing point of the aqueous solution of organic ammonium carboxylate of formula (I) which—has been sprayed onto surface of fine material when water has been evaporated.