FI77788C - SKUMBEKAEMPNING MED LASERSTRAOLE. - Google Patents

Description

1 77788

Foam control with laser beam - Skumbekämpning med laser-sträle

The invention relates to a method for limiting and / or disposing of foam. At present, mechanical systems on the one hand and chemical defoamers on the other are used as both preventive and repressive methods for removing foam.

Mechanical, preventive equipment usually requires soothing basins, expansion chambers, flow management, and structures that require expensive investments. In many circumstances, they are not at all possible because foam formation occurs at a stage in the process that cannot be altered for production or other reasons. Repressive mechanical means often require extensive structures such as precipitation chambers, rotors, recirculation systems, and other structures, in addition to which the production rate must be reduced and controlled to prevent excessive foam.

Preventive chemical additives that alter the chemical properties of a liquid are not only expensive but often those that affect the actual production process and the final product. By changing the surface tension of the liquid, the surface film, the pH, the amount of particles, the amount of air, the chemical or other properties, the formation of foam can be influenced, but this often adversely affects the final process or the final product. In the case of foodstuffs or other substances of high purity, many chemical changes cannot be made without affecting the final product.

In addition to chemical foaming agents, ultrasonic waves have been used, but 2,77788 act over a fairly limited range. Temperature also affects the stability of the foam. As the temperature of the foam rises, its viscosity decreases; in this case, the flow of liquid from the lamellae of the foam is accelerated, the bubbles of the foam increase and the effect of the disappearance of the bubbles is repeated due to the destructive effect of the liquid droplets. Raising the overall process temperature is expensive, and other production-related factors may require a different temperature.

Mechanical foam limiters and removers have so far had problems with their high cost, energy use, low convertibility, and space requirements.

In addition to costs, the main problem with chemicals is that they either adversely affect industrial waste, adversely affect the actual process if they are returned to the process due to the fluid circulation, or enrich in the process with negative consequences and / or additional costs. Some chemical substances precipitate with foam-forming substances, which causes more problems with the precipitate and mucus. Some form a new surface film in which foaming agents dissolve (such as hydrocarbons, certain alcohols, and esters), but these cause problems for workers and even a fire hazard. Some form emulsions, which in part destroy substances important to the process and in part cause emulsion removal problems. The use of surfactants requires constant monitoring of surface tension, as the repetitive effect of the substances causes new problems. Volatile liquids (which facilitate the formation of foam bubbles) can be used in some special cases, but are only suitable for closed systems in special conditions. Liquid-centered substances such as polyamides or buoyants prevent the actual production process from being speeded up, as they must be held in place and prevented from flowing.

II

3 77788 process fluid included. In addition to mechanical particles, silicones and mineral oils can be used, which displace the existing foaming agent without interfering with it. However, they are not suitable for large-scale production.

The quality of the foam can also be affected both mechanically and chemically, allowing different systems to be combined. Foam is a colloidal system consisting of a dispersed gas in a liquid. The foam has a large liquid surface area relative to the amount of liquid, and the quality of the foam is determined by the relative proportion of gas and liquid (= foam number). If the foam bubbles are small and clearly separated from each other, it is often a stable foam that is difficult to remove mechanically. The lightweight foam forms a polyether foam in which gas bubbles are positioned so that a triangular liquid column is formed at the junction of the three lamellae. The thinner the liquid phase boundary and the liquid layer between the bubbles, and the smaller the amount of liquid in the Plateau boundary, the easier it is to dispose of the foam mechanically, but this usually requires a strong (volume) increase in the foam with its own side effects. It has proved very difficult to control the quality of the foam (foam number and bubble size) on the one hand and the total volume of the foam on the other hand, and to relate these to the process. In the present case, the focus is on disposing of or limiting the foam in or after its natural environment of origin, using minimal energy and so few chemicals that it does not affect the actual product of the process.

The present invention is characterized in that a laser beam in the infrared range is directed at the foam or in the immediate vicinity of the surface of the foam-forming liquid.

«77788

The innovation is the use of a laser beam in the infrared range to limit and eliminate foam. The water molecules in the foam bubbles strongly absorb infrared rays. Absorption causes local heating in the bubbles and disintegration of the foam bubble. The centralized energy in the beam heats the liquid membrane of the gas bubbles and thus reduces the viscosity and surface tension of the liquid. The energy added to the foam accelerates the diffusion of small bubbles into larger gas bubbles in the inhomogeneous foam due to the pressure difference. The result is the disappearance of small bubbles and the enlargement of large ones until they disintegrate. Depending on the quality of the foam, compression of the foam also results in an increase in dry matter content, which increases the surface tension and, in some conditions, disintegrates the foam.

A suitable infrared beam can be generated by a laser characterized by the coherence of the radiation, the narrowness and directivity of the wedge, and the intensity. A suitable type of laser is a carbon dioxide laser with a wavelength of about 10 μm and high power even in continuous use.

Continuous breaking of bubbles results in a limited amount of foam in continuous processes. The beam can be fixed or moving during the process. The radiation source must be positioned so that the beam strikes the point of foam formation or the place where the foam is to be removed.

Previously known mechanical and chemical methods of foam control can be combined with a method based on a laser beam in the infrared range.

The method is particularly applicable to processes in the forest industry with foam problems.

Claims (4)

5,77788 1. A method for controlling and disposing of foam, characterized in that a laser beam in the irrared region is directed at the foam or in the immediate vicinity of the surface of the liquid forming the foam. A method according to claim 1, characterized in that said infrared beam is generated by a carbon dioxide laser having a wavelength cr. r.cin 10 μm. A method according to claim 1, characterized in that the laser beam is fixed or moves close to the surface level of the foam-forming liquid, preventing the formation of foam. Method according to Claim 1, characterized in that the laser beam is directed at the foam already formed.