Study of the Foaming Properties of Certain Substances
Abstract Generated abstract
This study evaluates the foaming performance of several substances for air-mechanical fire-extinguishing foam, focusing on foam expansion and stability relative to the commonly used PO-1 foaming agent. Using the Ertikovsky method and GOST 6948-54 tests, the authors compare PO-1, aminonitroparaffin, sulfate soap, recycle soap, a foam reagent, coke-chemical wastewater, and mixtures of these materials with PO-1. Aminonitroparaffin and sulfate soap showed strong foaming properties but were considered impractical because of cost, while several additives reduced PO-1 performance. Wastewater from a coke-chemical plant, especially in mixtures with PO-1, substantially increased foam stability and in some formulations reduced PO-1 consumption, with the effect attributed partly to surface tension reduction and possible formation of fine precipitates.
Full Text
Study of the Foaming Properties of Certain Substances
S. A. Babenko, L. F. Prosekova, O. I. Popova,
V. K. Telnova, E. V. Chaban
(Presented by the scientific seminar of the departments of PMAKhP and OKhT)
In recent years, air-mechanical foam has found broad application for extinguishing many combustible substances and, above all, liquids whose specific gravity is less than the specific gravity of water.
Air-mechanical foam is obtained on the cells of a mesh, to which a finely dispersed foaming liquid is supplied; this liquid is a solution of a foaming agent in water and, in significant volumes, air [1].
The expansion ratio and stability, which determine the fire-extinguishing properties of foam, are governed chiefly by the quality of the foaming agents. The foaming agent PO-1 has received the widest use in firefighting practice. However, the insufficient expansion ratio and especially the low stability of the foam obtained using the foaming agent PO-1 prompted us to carry out the present work.
The following substances were tested as foaming agents:
- Foaming agent PO-1, consisting of kerosene contact, bone glue, ethylene glycol, and caustic soda.
- Sulfate soap—a product of wood processing in the pulp-and-paper industry.
- Recycle soap was obtained by saponification of recycle, a petroleum-refining product.
- Aminonitroparaffin (ANP)—a cation-active substance.
- Foam reagent—a waste product from the production of synthetic fatty acids.
- Wastewater from the Kemerovo coke-chemical plant, containing 0.53 g/L oils, 0.28 g/L phenols, and 0.32 g/L pyridine bases. In addition, the wastewater contains ammonia, chlorides, sulfates, and other substances.
The substances numbered 2, 3, and 4 possess, along with foaming properties, collecting properties as well; therefore they are used in the ore-processing industry for the flotation of useful minerals.
The foaming properties of the indicated substances were evaluated by measuring the expansion ratio and stability of foams by the method of Ertikovsky [2] and according to GOST 6948-54 [3]. The first method is more productive and makes it possible to study foams of any stability.
The expansion ratio of air-mechanical foam is determined by the amount of air contained in its composition and can be expressed as the ratio-
ratio of the volume of foam to the volume of the foaming liquid or, under comparable conditions, by the height of the foam column. Foam stability is understood as its ability to be preserved for a certain time.
Table 1
Height of the column and stability of the foam
| Name of substances | Concentration of the substances studied in water, % | Height of foam column, cm | Foam lifetime, sec |
|---|---|---|---|
| PO-1 | 0.5 | 8 | 50 |
| PO-1 | 1.0 | 28 | 110 |
| PO-1 | 2.0 | 40 | 360 |
| ANP | 1.0 | 15 | 50 |
| ANP | 2.0 | 20 | 620 |
| ANP | 4.0 | 35 | 880 |
| Sulfate soap | 2.0 | 10 | 125 |
| Sulfate soap | 6.0 | 25 | 660 |
| Recycle soap | 1.0 | 5 | 45 |
| Recycle soap | 6.0 | 30 | 180 |
| Foam reagent | 2.0 | 10 | 5 |
| Foam reagent | 4.0 | 40 | 35 |
| Wastewater | 100 | 30 | 5 |
| Wastewater + PO-1 (1:1) | 2.0 | 23 | 840 |
| Wastewater + PO-1 (1:2) | 2.0 | 35 | 900 |
The influence on the expansion ratio and stability of the foam of the concentration of the foaming agent in water and of the ratio of additives to the foaming agent PO-1 was studied. The water temperature was \(18^\circ\mathrm{C}\). Table 1 gives the results of measuring the height of the foam column and its lifetime with the addition of various foaming agents. The studies began with a concentration of 0.1% and increased to 2–6%. The reagents studied give a considerable foam expansion ratio and stability when a concentration of 2% is reached. ANP showed good foaming at \(\mathrm{pH} = 2\). In the remaining experiments, with the exception of wastewater, the medium was neutral. Wastewater gives abundant foam, but very unstable.
Since the reagents ANP and sulfate soap, which give the best results in foaming, are expensive and cannot be recommended for firefighting purposes, at the next stage of the study the goal was set of finding the amount of these additives to the foaming agent PO-1 in order to improve its properties. Additives of ANP, sulfate
soap, recycle soap, and foam reagent to the foaming agent PO-1 in ratios of 1:1 and 1:2, and a mixture concentration of 2%, showed that the foaming properties of PO-1 deteriorate. Additions of wastewater significantly improved the foam stability from 360 sec without additives to 840–900 sec (Table 1).
Table 2
Effect of the amount of wastewater on the foaming properties of PO-1
| No. of experiments | Name of substances | pH of substances | Foam expansion | Foam stability, min |
|---|---|---|---|---|
| 1 | PO-1 | 1.5 | 5.5 | 9 |
| 2 | PO-1 | 7.0 | 6.0 | 14 |
| 3 | Wastewater + PO-1 = 1:2 | 3.0 | 6.0 | 31 |
| 4 | Wastewater + PO-1 = 1:1 | 4.0 | 5.0 | 28 |
| 5 | Wastewater + PO = 2:1 | 5.0 | 3.0 | 15 |
| 6 | Wastewater + PO-1 = 4:1 | 6.5 | 2.3 | 12 |
| 7 | Wastewater + PO-1 = 4:1 (10% soln.) | 6.5 | 8.5 | 45 |
| 8 | PO-1, foaming of wastewater | 1.5 | 9.0 | 20 |
| 9 | PO-1, foaming of wastewater + tap water (1:1) | 1.5 | 8.5 | 80 |
To find the optimal amount of wastewater to be added to the foaming agent PO-1, at which its properties would be the best, studies of foam expansion and foam stability were carried out according to GOST 6948-54. The concentration of the foaming agent, as well as of the mixtures, was 2%; only for the mixture of wastewater and PO-1 in a ratio of 4:1 was the concentration 10%.
The pure foaming agent PO-1 adopted for the study forms a foam with an expansion of 5.5 and a stability of 9 min (Table 2). The GOST requirements for the foaming agent PO-1 are: expansion 10, stability 30 min. From a comparison of these values it is evident that the PO-1 under investigation falls considerably short of the requirements, especially in stability; the pH of PO-1 was 1.5. According to [3], PO-1 should have a neutral medium; however, neutralization with soda improved the foaming properties of PO-1 only slightly. Preliminary mixing of PO-1 with wastewater improves its foaming properties. In this case, the expansion and stability of the foams change differently. The best results for expansion were obtained
in experiment 8, where the PO-1 foaming agent was mixed with wastewater in a ratio of 1:50 and foamed without the addition of water. A foam stability equal to 80 min was obtained in experiment 9, when PO-1 was added for foaming a mixture of wastewater and tap water in a ratio of 1:1. Since delivering large quantities of wastewater to the site of a fire is irrational, then, based on the experimental results, it is possible to recommend for foam formation a composition consisting of one part wastewater and two parts PO-1 (experiment 3). The consumption of foaming agent is thereby reduced by one third, while the quality of the foam, judging by its stability, increases almost 3.5-fold in comparison with foam formed by PO-1 alone. Also worthy of attention is a mixture of wastewater and PO-1 in a ratio of 4:1 (experiment 7). A 10% composition of such a foaming agent (the PO-1 consumption is the same as in experiment 1) forms foam with an expansion ratio of 8.5 and a stability of 45 min.
Table 3
Surface tension of solutions used for foaming
| No. of experiments | $\dfrac{\mathrm{dyn}}{\mathrm{cm}}$ |
|---|---|
| 1 | 40.3 |
| 3 | 44.0 |
| 4 | 43.8 |
| 5 | 47.7 |
| 6 | 51.2 |
| 7 | 39.2 |
| 8 | 36.6 |
| 9 | 40.0 |
The role of the foaming agent is reduced to lowering the surface tension of the liquid. This proposition is also valid in our case. The lower the surface tension, the higher the foam expansion ratio (Tables 2 and 3). The increase in foam stability at the same surface tension of the liquid can be explained by the formation of fine precipitates during the interaction of the substances contained in the wastewater and PO-1.
LITERATURE
- E. P. Savkov, G. N. Vasil'ev. High-expansion foam fire-extinguishing agent. Moscow, Stroiizdat, 1965.
- G. O. Ertikovskii. Formation of flotation foam. GONTI, Moscow, 1939.
- Instruction on the procedure for transporting, storing, and checking the quality of PO-1 and PO-6 foaming agents. Moscow, 1961.