Method for treating water using nanobubbles and biocides in the production of wood pulp, paper, and cardboard

Abstract

A water treatment procedure using nanobubbles and biocides in the manufacture of wood pulp, paper, and cardboard that can effectively control the microbial population with higher efficiency than those based solely on biocides, minimize the consumption of water and biocides, apply natural elements, and reduce environmental impacts at low cost. The procedure realizes the combined use of gas nanobubbles in an aqueous medium and a conventional biocide, and consists of the following steps for the treatment of supplied and obtained fresh water. 1. Passing water from a river, reservoir, or well (1) through a nanobubble generator (2) into which an oxidizing gas (3) consisting of oxygen-containing air, pure oxygen, or high-purity ozone is injected; 2. Incorporating a biocide (4) into the mixture with the nanobubbles; and 3. Passing the water through a manufacturing process (5).

Description

Technical Field

[0001] Combined use of gas nanobubbles and a conventional biocide in an aqueous medium in the manufacture of wood pulp, paper or cardboard, including water in the manufacturing process, residual water and fresh water from rivers, reservoirs or wells supplied to the manufacturing process.

[0002] The present invention pertains to the industries of wood pulp, paper and cardboard, and specifically to the water treatment processes employed in their manufacture.

Background Art

[0003] Along with the fibers of wood, water is the most important raw material in the paper and cardboard industries, being used at each step of the manufacturing process, as a means of transporting the cellulose fibers along the manufacturing machinery for the preparation of pulp of cellulose fibers, and also for other uses such as the production of energy and steam for thermal and mechanical processes and the cleaning of equipment.

[0004] When manufacturing virgin fiber paper from wood, water is used to separate cellulose fibers from lignin. Even when the raw material being used is recycled waste paper, water is used to separate cellulose fibers from inappropriate materials (staples, sand, plastics, etc.).

[0005] Subsequently, an aqueous solution of cellulose fibers is prepared based on the natural property of cellulose fibers to bond without the need for adhesives in the presence of water.

[0006] Once in the manufacturing machinery, the cellulose pulp passes through different phases where first a sheet is formed on a ground fabric structure where water is extracted by gravity, then it is transported to another part of the process by a roller system, dried by a pressure system, vacuum, and finally completely dried.

[0007] Controlling the biological content of water is the key to the manufacturing process and the quality of the resulting products. In this sense, water can be classified into three types: namely, raw water that is supplied and collected, water in the manufacturing process, and residual water.

[0008] Raw water that is supplied and collected is usually from rivers, reservoirs or wells. This is water that is not usually suitable for human consumption and has not been sterilized. It is water with a high level of microbial contamination, with a strong organic load from chemicals and a tendency for microorganisms that, if not removed, will tend to grow or have a biased growth towards the manufacturing process.

[0009] Conventional treatment of raw water, which is carried out at low cost in the manufacture of pulp, paper and cardboard, is based on chlorine-based, usually sodium hypochlorite type, oxidizing biocides.

[0010] Water in the manufacturing process is that which is used in the manufacturing processes of pulp, paper and cardboard. In the manufacturing process, a large amount of water that is recycled and reused in a closed circuit is required in a continuous cycle, some of which is sent for purification and disposal, and / or recovered, some evaporates in the manufacturing process itself, and the rest is supplied to the process as recycled raw water.

[0011] The conditions to which the water is exposed (pH, conductivity, temperature) and the high contamination from the raw materials (extremely high in recycled paper and cardboard) create conditions favorable for the growth and exponential increase of the microbial population. These uncontrolled increases cause significant problems in the manufacturing process, highlighting the loss of performance of various additives (preservatives, adhesives, defoamers, bleaching agents, etc.) applied to the process, the problem of deposits that cause damage in the population, and quality problems in the final product, especially decomposition problems due to anaerobic conditions in the environment that cause odor and spoilage.

[0012] The microbial treatment actually applied to the water in the process uses organic agents (DBNPA, isothiazolinone, bronopol, glutaraldehyde) and inorganic agents (usually oxidants derived from chlorine types MCA, MCDMH) in a process that is not usually continuous. They are administered at dosing intervals that make them economically valuable and enable proper control of the microbial population to minimize the above-mentioned adverse effects at strategic points in the production circuit.

[0013] This procedure has the inconvenience that the dosage applied to the cost / efficiency ratio of the biocidal treatment of the machine is not sufficient to solve the problems of microbial increase and advanced fermentation processes, and only partial control is achieved in a sawtooth cycle by alternate discontinuous cycles of dosing that are economically infeasible.

[0014] On the other hand, this type of product can cause damage to the conduits and pipelines in the manufacturing process due to corrosion, adding labor risks associated with the operation.

[0015] Furthermore, the worldwide strengthening of national and international laws regulates the formulations available in the market.

[0016] Therefore, it is wise to pursue alternative methods that can accept these inconveniences while enhancing the efficiency and effectiveness of controlling microbial growth.

[0017] One method employed in water treatment is the use of oxygen and ozone. Ozone is a substance whose molecules are composed of three oxygen atoms, has the formula O3, and is a gas at atmospheric pressure. By its very nature, pure oxygen and ozone are strong oxidizing agents and have the ability to remove pathogenic microorganisms, i.e., they are biocides. Usually, it is dissolved in water for use, and higher concentrations are required to obtain a greater biocidal efficiency than necessary, thus increasing costs. Although it exists in the atmosphere in its natural form, for industrial use, ozone is artificially generated by an ozonator or ozone generator, and its generation is carried out by electrical energy. Due to the use of ozone in this competing form of application, it would be advisable to minimize the energy cost and maximize the concentration.

[0018] Furthermore, the actual systems of the concentrations of oxygen and ozone gas in water act through solubilization in the gas phase or low-pressure phase in the industrial fields in which they are utilized. Therefore, once the system is depressurized and / or the dosing point is far from the generation point, the solubilized gas is lost almost immediately. This considerably limits the efficiency of the treatment based on this technology using conventional application means.

[0019] All of the above gives rise to an unmet need in the market for water treatment procedures employed in the manufacturing processes of wood pulp, paper, and cardboard that enables effective control of the microbial population, such as changing the anaerobic environment to an aerobic environment, eliminating odor and fermentation problems, complementing or duplicating the actual treatment at dosing intervals, making significant growth impossible between treatment shocks, and reducing the lethal dose of biocidal treatment. Similarly, having a high water recovery capacity, minimizing water consumption, reducing the consumption of conventional biocides involved in its management and operation, and applying natural gas elements such as oxygen and ozone at high concentrations and high efficiency to reduce environmental impact. All of these enable a treatment with higher efficiency at a lower cost than the current treatment based solely on biocides.

[0020] The document of Patent Document 1 describes an antibacterial treatment method for the water system in the paper manufacturing process, which can maintain an oxidative environment in water, maintain a long-term antibacterial effect, and suppress the increase of anaerobic microorganisms. Therefore, this antibacterial treatment method includes steps of including ultrafine bubbles of oxygen in the water of the clean water circulation water system, the residual water treatment water system, and the recycled raw material supply water system, and steps of adding an antibacterial agent and sodium chlorite.

[0021] On the other hand, the document of Patent Document 2 describes a method for eliminating or reducing bacteria increase or biofilm formation in the paper or cardboard manufacturing process, and the method includes introducing gas bubbles with a diameter of less than 0.5 micrometers into the paper or cardboard manufacturing process.

Prior Art Documents

Patent Documents

[0022]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0023] The object of the present invention is to change an anaerobic environment to an aerobic environment, eliminate problems of odor and fermentation, complement or duplicate the actual treatment during the dosing interval, make significant growth impossible between treatment shocks, reduce the lethal dose of biocidal treatment, enable treatment with higher efficiency than the current treatment based only on biocides, and enable effective control of the microbial population, and obtain a water treatment procedure via nanobubbles and biocides in the manufacturing processes of wood pulp, paper, and cardboard.

[0024] Another object of the present invention is to minimize water consumption, reduce the consumption of conventional biocides involved in its management and operation, and apply natural gas elements such as oxygen and ozone at high concentration, high efficiency and low cost to reduce environmental impact, and obtain a water treatment procedure via nanobubbles and biocides in the manufacture of wood pulp, paper and cardboard, which has high water recovery ability, and other gas elements can also be used. Means for solving the problems

[0025] Nanobubbles are defined as extremely small bubbles with a size of 70 to 120 nanometers (about 2500 at the size of a single salt particle). Nanobubbles can be formed by injecting any gas into a liquid medium (usually aqueous), and due to Brownian motion and non-rising motion, they are small enough to remain in the liquid phase over time. Because of the large contact surface area, the transfer of gas (which can be atmospheric oxygen, pure oxygen or ozone) into water is very efficient, and a high concentration of the gas in the medium can be achieved, which is useful in its use. In this case, the effect as a highly efficient oxidant can be enhanced.

[0026] As described in the specification of Spanish Patent No. 1263409, there is a nanobubble generation facility in the market that can achieve extremely high values of O2 exceeding 30 ppm and O3 exceeding 5 ppm with the supply of high-purity oxygen and / or ozone at the concentration of the gas introduced into its generation. These gases at the above concentrations are highly toxic to all microorganisms present in the medium, achieve a high level of oxidation-reduction potential, and show high efficiency in the control of the above microorganisms through the use of bioluminescence measurement using fast-responsive adenosine triphosphate (ATP) or conventional culture in Petri dishes.

[0027] The procedure of the present invention consists of the combined use of gas nanobubbles in an aqueous medium using any gas, mainly air, pure oxygen or ozone, provided that any gas element that is easy to enter the gas biocide and / or nanobubbles is also utilized, and a conventional (in the broadest definition, extended, origin and / or natural) biocide in the manufacture of wood pulp, paper or cardboard, and includes the water in the manufacturing process, residual water, and raw water from rivers and / or wells supplied to the manufacturing process. The procedure for the object of the present invention consists of the following steps in the case of treating supplied and obtained fresh water.

[0028] 1. Pass the water from a river, reservoir or well through a nanobubble generation facility into which a gas consisting of oxygen in the atmosphere, pure oxygen or high-purity ozone, which is the above-mentioned oxidizing gas, is injected.

[0029] 2. As a supplement to the treatment, incorporate a biocide in a dosage less than that normally required for individual treatments.

[0030] 3. Pass the water through a manufacturing process.

[0031] The order of the above steps can be reversed, i.e., first incorporate the biocide into the water and then pass it through the nanobubble generator. This procedure is as follows. 1. Incorporate a biocide into the water from a river, reservoir or well. 2. Pass the water containing the biocide through a nanobubble generator into which a gas consisting of oxygen-containing air, pure oxygen or high-purity ozone, which is the above-mentioned oxidizing gas, is injected. 3. Pass the water through a manufacturing process.

[0032] In the case of water in the manufacturing process, the procedure consists of the following steps. 1. Incorporate a biocide into the water in the manufacturing process. This is a treatment according to the conventional pattern, emphasizing the strategy of the dosing point, dosing cycle and required dosage. 2. Store excess water at each phase of the manufacturing process. 3. Pass the stored water through a nanobubble generation facility into which a gas consisting of oxygen-containing air, pure oxygen or high-purity ozone, which is the above-mentioned oxidizing gas, is injected.

[0033] The incorporation of nanobubbles can be achieved directly "online" in the manufacturing process itself without water storage. The procedure is as follows. 1. Incorporate a biocide into the water in the manufacturing process. 2. Pass the process water in the engineering flow itself through a nanobubble generation facility into which a gas composed of the above-mentioned oxidizing gas, namely air containing oxygen, pure oxygen, or high-purity ozone, is injected.

[0034] In this form, advanced sterilization can be carried out to reduce the required dosage of conventional biocides, achieve better sterilization results at low cost, and reduce the risks of operation and corrosion to a low level.

[0035] However, in all of the above cases, the gas can be a gaseous biocide instead of air, pure oxygen, or ozone. In this case, although there are no advantages inherent in these components, high efficiency can be obtained due to the high contact area enabled by nanobubbles.

[0036] Along with the specification and claims, the term "comprende" and its variants are not intended to exclude other technical features, components, additives, or steps. For experts in the materials, other purposes, advantages, and features of the invention are inferred in part of the invention and part of the practice of the invention. The following examples and drawings are provided by way of illustration and should not be understood as limiting the present invention. Furthermore, the invention encompasses all possible combinations of the specific preferred embodiments shown in this specification.

Brief Description of the Drawings

[0037] For the purpose of complementing the described explanation and helping to better understand the features of the invention, a set of drawings is attached as an integral part of the explanation, and the following is presented in the drawings by way of illustration and not limitation.

[0038]

Figure 1

[0039]

Figure 2

Embodiments for Carrying Out the Invention

[0040] To identify the elements forming part of the water treatment procedure via nanobubbles in the production of wood pulp, paper, and cardboard, the description of the above procedure is given for two preferred embodiments of the invention using the numbers employed in FIGS. 1 and 2 of this document.

[0041] The water treatment procedure via nanobubbles and biocides in the production of wood pulp, paper, and cardboard consists of the following steps in a preferred embodiment for the treatment of raw water supplied and obtained.

[0042] 1. Pass the water from a river, reservoir, or well (1) through a nanobubble generation facility (2) into which a gas (3) consisting of air containing oxygen, which is the above oxidizing gas, pure oxygen, or high-purity ozone is injected.

[0043] 2. As a supplement to the treatment, incorporate a biocide (4) into the mixture with the nanobubbles at a dosage lower than that commonly used in individual forms.

[0044] 3. Pass the water through the manufacturing process (5).

[0045] In a preferred embodiment, the order of the above steps can be reversed, first incorporating the biocide into the water and then passing it through the nanobubble generator.

[0046] The water treatment procedure via nanobubbles and biocides in the production of wood pulp, paper, and cardboard consists of the following steps in another preferred embodiment for the treatment of the water in the manufacturing process. 1. Incorporate a biocide (4) into the water of the manufacturing process (5). 2. Store the excess water (6) at each phase of the manufacturing process. 3. Pass the stored water (6) through a nanobubble generation facility (2) into which a gas (3) consisting of air containing oxygen as the above-mentioned oxidizing gas, pure oxygen, or high-purity ozone is injected.

[0047] In a preferred embodiment, the incorporation of nanobubbles can be realized directly "online" in the flow of the manufacturing process itself without storing water.

Claims

1. A method for manufacturing wood pulp, paper, and cardboard through water treatment using gas nanobubbles in an aqueous medium and a conventional biocide, comprising: (a) a treatment step for raw water supplied and obtained from a river, reservoir, or well (1), and / or (b) a water treatment step in the manufacturing process of wood pulp, paper, and cardboard, wherein (a) the treatment step for the raw water in the manufacturing process (5) of wood pulp, paper, and cardboard comprises: (a.1) passing the raw water through a nanobubble generator (2) into which gas (3) is injected; (a.2) incorporating a biocide (4); and (a.3) passing a mixture of water, nanobubbles, and biocide through the manufacturing process (5); and (b) the treatment step for the residual water in the manufacturing process of wood pulp, paper, and cardboard comprises: (b.1) incorporating a biocide (4) into the water in the manufacturing process (5); and (b.2) passing the water in the manufacturing process (5) in the flow of the process itself through a nanobubble generating facility (2) into which gas (3) is injected.

2. The method according to claim 1, wherein the gas (3) is selected from (a) an oxidizing gas consisting of air containing oxygen, pure oxygen, or high-purity ozone, or (b) a gaseous biocide.

3. In the manufacturing process (5) of wood pulp, paper, and cardboard, incorporating the biocide (4) into the treatment step for the raw water occurs in the mixture of the raw water and nanobubbles or directly in the raw water from a river, reservoir, or well (1). The method according to claim 1 or 2.

4. In the treatment step for the residual water in the manufacturing process of wood pulp, paper, and cardboard, there is an intermediate step of storing excess water (6) in each phase of the manufacturing process before passing it through the nanobubble generating facility (2). The method according to any one of claims 1 to 3.

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