Method for treating condensate in a pulping process

Abstract

The present invention relates to a method for producing a treated condensate substantially free of organic matter by treating the condensate with at least one of a physical, chemical, chemical-physical treatment or a combination thereof. In addition, there is provided a method for treating condensate in a pulp process fiber line utilizing multiple washing stages with at least the treated condensate circulating in a closed loop before feeding the condensate to the fiber line, the method comprising the steps of: a) identifying colloidal organic compounds in the condensate; b) subjecting the condensate to at least one of a chemical, physical, chemical-physical treatment or a combination thereof; and c) reducing the contamination of the condensate before feeding it to the final washer stage, or to some other stage of the pulping process.

Description

Technical Field

[0001] The present invention relates to a method for producing a treated condensate substantially free of organics and pitch colloids by treating the condensate with at least one of a physical, chemical, chemical-physical treatment or a combination thereof. Background Art

[0002] Industrial processes for producing cellulose-rich pulp from harvested wood are well known and generally involve steps of physically breaking the wood into smaller fragments and particles followed by chemical digestion at elevated temperatures and pressures to dissolve the lignin and separate it from the constituent cellulosic fiber biomass.

[0003] In chemical pulping, wood chips are digested with a chemical solution to dissolve a portion of the lignin, which has the effect of removing lignin, extractives and inorganic matter. The most commonly used digestion methods are sulfite, soda, sulfate or Kraft and modified sulfate.

[0004] The material obtained after the digestion and washing steps of the wood is usually a dark cellulose fiber. The dark color is due to the fact that not all the lignin was removed during the digestion process, and the remaining lignin has been chemically modified. This dark pulp is usually called unbleached pulp or brown stock. If the color of the paper is not important, it can go directly to the papermaking operation, otherwise, the unbleached lignocellulosic pulp is bleached. Bleaching is a term applied to a semi-chemical or chemical step, in which the pulp is treated with an active bleaching agent (e.g., chlorine, chlorine dioxide, ozone, oxygen, hydrogen peroxide, enzymes or mixtures thereof) under controlled time, temperature and pH. The desired result of these reactions is to whiten the pulp to a higher brightness level. Pulp bleaching is most commonly a multi-stage process using chlorine or chlorine-containing compounds (e.g., calcium hypochlorite, sodium hypochlorite and chlorine dioxide). Chlorine bleaching of lignocellulosic pulp is a process well known in the art.

[0005] The pulping process in a fiber production line comprises the basic sequential units of cooking, brown stock washing, oxygen delignification and screening. The pulping process is usually preceded by a chemical or mechanical pretreatment of the prepared wood fiber pieces. Each step of the pulping process is usually followed by a water wash, which can be carried out with process liquor obtained elsewhere in the process, such as by countercurrent washing, which has the attendant advantage of saving. In this sense, current fiber production lines reuse the water evaporated in the process in order to reduce the environmental impact.

[0006] After digestion is complete, solids comprising cellulose fiber pulp are separated from spent digestion liquor, which is often called black liquor and typically contains organic solvents, dissolved lignin, solid and particulate monosaccharides, oligosaccharides, polysaccharides and other organic compounds released from the wood during chemical digestion.

[0007] Lignin and the products obtained from the kraft process or modified kraft process constitute black liquor which is separated in the washing plant and sent to an evaporator to increase the solids concentration and to a recovery boiler. In this plant, black liquor is usually used as fuel to produce steam and electricity, where most of the chemicals used in the kraft process are recovered. The condensate is usually reintroduced in the pulping process in the brown stock washing system, with or without the addition of water.

[0008] Washing of cellulose pulp from digestion is usually done with water or process condensate, i.e. black liquor evaporation system, which system works countercurrent to the fiber line washers. To reduce liquid and gaseous wastes, washing is done in the process by a closed liquid circulation system. Pulp washing is done in a multi-stage countercurrent sequence, where the cleanest water is added in the last stage and the resulting filtrate is used in the previous stages until it reaches the discharge tank or washing zone in the continuous digester.

[0009] The purpose of washing the brown stock after cooking is to remove the maximum amount of dissolved organic matter from the wood using the minimum amount of clean or recycled water from the process and to remove soluble inorganic matter from the cooking liquor that is mixed with the pulp at the end of cooking, to facilitate the bleaching process and to reduce the cost of replacing chemicals lost in the process.

[0010] Recovery of organic matter (i.e., dissolved lignin and carbohydrates) plays a role further downstream in the process. For mills with oxygen delignification and / or bleaching steps, eliminating organic chemicals in the pulp entering these processes reduces operating costs. Since these stages are oxidative in nature, improving lignin removal by enhancing brown stock washing will lead to a reduction in process chemical consumption and reduce the load on waste and effluent treatment plants. In addition, brown stock washing helps to remove unwanted materials such as metals, resins, and wood extractives. Wood extractives that are not successfully removed from the pulp by washing tend to concentrate in downstream processes and form sticky deposits on the equipment, which in turn can lead to the production of poor quality pulp and / or paper by forming spots and holes. The stripping method of the condensate after evaporation is also another method to remove organic matter (usually non-condensable gases).

[0011] In this sense, Opedal et al. in their review article "Colloid stability in thermomechanical pulping and removal of extractives from industrial process waters" teach that physicochemical operations such as sedimentation, flocculation, filtration and pH reduction are effective for separating extractives from process water - that is, water from a thermomechanical pulping process to be reused - thereby performing pitch control in a thermomechanical pulping process.

[0012] However, with regard to the kraft pulping process, it has been determined that the condensate obtained by evaporating black liquor, although previously considered free of contaminants, still contains significant amounts of organic compounds, particularly in the form of colloids and resins, which presents several disadvantages when the condensate is used in a wash pulping process.

[0013] The benefits of reusing condensate are numerous, such as reduced use of energy and water resources, improved working conditions, improved crude material washing systems, reduced consumption of bleaching chemicals (e.g. peroxide, ozone, chlorine dioxide), reduced carbon footprint, reduced fuel consumption, reuse of sensible heat measured in existing thermal energy, which in turn reduces the energy required to convert water into steam, positive impact on the environment, reduced fuel use, and reduced CO2, NO x 、SO x , AO x In view of the discharge of organic pollutants from condensates for reuse in pulping processes, there remains a need in the art to remove organic pollutants from condensates for reuse in pulping processes.

[0014] Therefore, a process for treating condensate from evaporation of brown stock from a cellulosic process remains desirable as it would allow elimination of said organic compounds contaminating the condensate and better control of the pitch, allowing all the aforementioned benefits to be achieved in a closed cycle pulping process. Summary of the invention

[0015] The present invention relates to a method for producing a treated condensate substantially free of organic matter by treating the condensate with at least one of a physical, chemical, chemical-physical treatment or a combination thereof.

[0016] Furthermore, a method for treating condensate in a pulp process fiber line utilizing multiple washing stages with at least treated condensate circulating in a closed loop before feeding the condensate to the fiber line is provided, the method comprising the following steps:

[0017] a) Identification of colloidal organic compounds in condensates;

[0018] b) subjecting the condensate to at least one of a chemical, physical, chemical-physical treatment or a combination thereof; and

[0019] c) Reduce the contamination of the condensate and feed it to the final washer stage, or to some other stage of the pulping process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Shown are images of a condensate sample 2 months after a plant shutdown (A), and an image of a sample from the same location 10 months after a plant shutdown (B).

[0021] Figure 2The "Modified Paprican Colloidal Resin Count Method" analysis of Sample A is shown, with the micrograph depicting colloidal resin in the condensate, indicated by arrows.

[0022] Figure 3 An image of the resin using a UV-Vis spectrophotometer is shown.

[0023] Figure 4 A schematic diagram showing a schematic diagram of the UV-Vis spectrophotometer measurement device Agilent Cary 300.

[0024] Figure 5 A dynamic description of the light attenuation thermal variation measurement method is shown.

[0025] Figure 6 A comparison of delta and deposited resin is shown.

[0026] Figure 7 The delta compared to the mass of deposited resin is shown.

[0027] Figure 8 A diagram showing a multiple single body assembly filter.

[0028] Fig. 9 A diagram showing a filter bag.

[0029] Fig.10 Photographs of filters used for filtering condensate before (left) and after (right) the process of the invention are shown.

[0030] Fig.11 The distribution of particles from the condensate is shown before (left) and after (right) the method of the invention.

[0031] Fig.12 An illustrative explanation of the zeta potential and particle charge is shown.

[0032] Fig.13 Photographs of condensate after 1 minute (left) and 10 minutes (right) of applying the method of the present invention for treating condensate are shown. DETAILED DESCRIPTION

[0033] In cellulose plants using the kraft process, black liquor rich in organic and inorganic materials is a by-product. To recover these materials, the black liquor is sent to a chemical recovery stage consisting of a process of concentrating the liquor by an evaporation system, then burning it in a recovery boiler, where the organic materials are burned, the inorganic materials are calcined, and their salts and alkalis are sent to a causticizing plant for recovery. The black liquor reaching the evaporation system generally has a solid content between 14% and 18%. These solids generally consist of 60% to 70% of dissolved organic materials from the wood and 30% to 40% of inorganic materials from the cooking liquor. A common evaporator system comprises a multiple-effect evaporator having at least several effects, usually six, and operating at a temperature usually up to 150°C. The evaporated water is then condensed in a condenser, for example a surface condenser after the evaporation plant or a condenser for a stripping tower used to clean the dirty condensate from the evaporation plant.

[0034] Typically, hot water is used in the washing stage. The weak black liquor from the cooking stage is directed from the cooking stage to an evaporation stage, in which part of the water is removed from the weak black liquor and thus strong black liquor is produced. The water removed from the weak black liquor, such as the condensate from the evaporation, is typically directed to the washing stage of the brown stock. The strong black liquor produced in the evaporation stage is used to recover steam in the boiler and to generate electricity. In the boiler, the smelt (black liquor after combustion) is washed with green liquor and sent to the causticizing unit. The green liquor is further processed to obtain white liquor, which can be reused for cooking. From the washing and oxygen stages of the brown stock, the pulp is directed to a bleaching unit.

[0035] Black liquor is an aqueous solution composed of organic materials such as lignin, resin compounds, polysaccharides, alcohols. Black liquor also contains inorganic materials from the pulping or cooking system.

[0036] The main purpose of the evaporation system is to concentrate the black liquor from the scrubbing system at a desired concentration and density so that it can be burned in the recovery boiler where the organic material will be burned.

[0037] Condensate recovered from evaporation processes is widely used in a large number of washing plants and bleaching plants in order to save treated water or raw water.

[0038] The evaporation system acts on the chemical properties of the liquid as a whole, including the hydrophobic materials contained in the organic portion present in the liquid.

[0039] According to the present disclosure, extractables and resins refer to low molecular weight organic substances present in condensates from evaporation of brown stock from cellulose processes, which can be extracted with water and / or organic solvents. Examples of substances soluble in organic solvents are fatty acids and esters, long chain alcohols, steroids, phenols and glycosidic substances.

[0040] Lipophilic extractables can agglomerate during the pulping process to form deposits called pitch. Pitch formation and its deposits in the pulp and paper industry lead to reduced production, increased equipment maintenance costs and a significant increase in defects in the final product, which reduces its quality.

[0041] Examples of resins are:

[0042]

[0043] Although the condensate was apparently free of organics, closer inspection revealed relatively high levels of organics (ie, resins) in the condensate. Figure 2 Depicted are colloidal resins in condensate from evaporation of brown stock from a cellulose process.

[0044] A portion of any organic or inorganic matter present in the condensate will be carried over to the fiber line where it should not be present and this may have a deleterious effect on the process.

[0045] The presence of complex organic and inorganic structures as well as some chemical and biochemical demand levels are due to the presence of more than 60 contaminants typically detected in the condensate, which require further treatment processes.

[0046] The present invention discloses a method for treating condensate by initially identifying colloidal resins in condensate from cellulose process brown stock evaporation. The steps performed according to the present invention result in the separation of resins composed primarily of organic matter from the condensate, allowing the measurement and further identification of such compounds and amounts.

[0047] In this sense, one embodiment of the present invention is achieved by a method of producing a treated condensate that is substantially free of organics by treating the condensate with at least one of a physical, chemical, chemical-physical treatment, or a combination thereof.

[0048] Preferably, the method of treating condensate from a pulping operation is a kraft pulping process. The invention is based on the ability of a fiber production line to treat condensable liquids and to provide condensate at a quality level that allows condensate reuse - returning the treated condensate to the pulping operation in a countercurrent manner. Typical volumes are about at least 100m 3 / h, typically even higher. The treatment of the condensate is performed using a method for producing a treated condensate substantially free of organic matter before the condensate is returned to the pulping process fiber production line closed loop. Preferably, the method of the present invention provides a reduction of at least 10 wt% of organic matter in the condensate, thereby producing a treated condensate, preferably 50%, more preferably 80%. Alternatively, the method may be employed without recycling the condensate when a different purpose than reintroducing the water into the fiber production line is preferred, such as any other application or disposal.

[0049] The level of organic matter (resin) in the condensate is relatively high. For example, the total organic carbon (TOC) level of the condensate can be found to be as high as 1.000 mg / L. Therefore, the method of the present invention involves condensate with a total organic carbon and hydrophobic substances of 50 to 1000 mg / L.

[0050] As used herein, treated condensate is condensate that has been subjected to a chemical, physical or chemical-physical treatment as disclosed herein. The treated condensate of the present invention is substantially free of resins having a TOC of less than 60 wt%. Thus, the process of the present invention discloses organic matter that is substantially resinous.

[0051] Specifically, the present invention is achieved by using chemical, physical, chemical-physical treatment or a combination thereof. The treatment of the condensate can be carried out in a system having at least one of coagulation, flocculation or a combination thereof.

[0052] Preferably, the chemical reaction occurs first, followed by a system of coagulation, flocculation and decantation, and then a physical retention system through filters.

[0053] Typically, the amount or concentration of organic matter in the medium is preferably measured by a modified Paprican colloidal resin counting method. This method involves sampling the process pulp and counting the number of colloidal resin particles in a known volume. This volume is called a Neubauer or blood cell counter. The basic principle is as follows: Colloidal resins are semi-solid particles that scatter light. Due to particle scattering, it will block light or attenuate light. The light attenuation is measured by UV-Vis spectrophotometry and is proportional to the resin concentration. The particle concentration includes measuring the number of particles and the cross-section or size of the particles. The relationship between scattering and particle size is non-linear, and the dependence of concentration on light attenuation is an approximation.

[0054] Lignin and some extractives absorb light through the interaction between photons of specific wavelengths and electron orbitals in aromatic molecules. The wavelength dependence of lignin absorbance is sensitive to pH, particularly between pH 9 and 11. The spectrophotometer can be configured to subtract lignin absorbance by using a filtered sample as a reference measurement.

[0055] Molecular absorbance is measured in the UV-Vis region. Molecular absorption in the UV-Vis region is due to electronic excitation in the outer (frontier) orbitals or in aromatic structures and double bond groups. According to Beer's law, absorbance is related to light intensity and concentration.

[0056] Attenuation of light is the reduction of light. This can happen due to molecular absorption, or it can happen due to solid particles or structures blocking the light. Attenuation is a more general term compared to absorbance. Solid or phase separated particles such as resins will attenuate light.

[0057] The science that describes the interaction of light with particles in the resin size range (0.1-20 microns) is Mie scattering.

[0058] Mie scattering is a mathematical method used to study the interaction of light with particles larger than 1 / 10 of the wavelength of light. The Mie scattering equation that defines the interaction of light with particles depends on the number of particles, the particle size, the refractive index of the particles, including the absorptivity of the material from which the particles are made (TMGarver, KHBoegh, GS Hill, D. Henry, HY Yuan, Analysis of the thermal variation of UV-visible attenuance of colloidal substances in Whitewater. Pulp and Paper Canada 103, 20-24 (2002)).

[0059] Figure 5 Schematic diagram of the Agilent Cary 300 UV-visible spectrophotometer measurement equipment.

[0060] In one embodiment of the present invention, a method for treating condensate from a pulping process comprises the following steps:

[0061] a) Identification of colloidal organic compounds in condensates;

[0062] b) subjecting the condensate to at least one of a chemical, physical, chemical-physical treatment or a combination thereof; and

[0063] c) Reduce the contamination of the condensate by feeding it to the final washer stage or some other stage of the pulping process.

[0064] An example of a further stage in a pulping process is the bleaching stage of the process.

[0065] Another preferred embodiment of the present invention is a method for treating condensate in a pulp process fiber line utilizing multiple washing stages with at least the treated condensate circulating in a closed loop before feeding the condensate to the fiber line, the method comprising the following steps:

[0066] a) Identification of colloidal organic compounds in condensate by TOC analysis;

[0067] b) subjecting the condensate to at least one of a chemical, physical, chemical-physical treatment or a combination thereof;

[0068] c) reducing organic contamination of the condensate by mechanical treatment of the condensate;

[0069] d) The condensate is returned to the pulping circuit in countercurrent.

[0070] Preferably, the analysis of TOC in step (a) is performed online; the treatment in step (b) is pH adjustment and / or addition of flocculants and coagulants; and the mechanical treatment in step (c) is decantation, filtration or flotation.

[0071] Furthermore, the condensate is returned to the pulping circuit in counter-current, more preferably by adding condensate at the brown press, the DDW (Drum Displacement Washer) or both.

[0072] More preferably, the condensate treatment is a combination of flocculation and coagulation followed by at least one decantation and filtration step.

[0073] Furthermore, the invention may be implemented by chemical, physical or chemical-physical processing.Other embodiments may include one or more processing in parallel or in series.

[0074] In a preferred embodiment, the present invention can be automated and comprises the following sequence of steps:

[0075] a) Online analysis of TOC in condensate;

[0076] b) sending a signal to the treatment dosage system;

[0077] c) dosing a coagulant into the condensate in a range of 0.2 g to 10 g / g organic TOC;

[0078] d) waiting for 2 to 15 minutes to continue adding flocculant to the condensate in an amount ranging from 0.3 g to 20 g per gram of organic matter known from TOC;

[0079] e) sending the treated condensate to a decanting tank with a retention time of 20 to 40 minutes;

[0080] f) sending the free condensate of the deposited material to a location where it is filtered using a 10 micron filter;

[0081] g) Filter the condensate of this step in a filtration system consisting of a 1.0 micron filter.

[0082] Preferably, in step (d), the waiting time is 5 minutes and the retention time in step (e) is 30 minutes.

[0083] Furthermore, it is worth mentioning that the condensate consists of different molecular weights, has different behaviors and different sedimentation speeds. Therefore, the final removal of the floccules of micelles that did not settle in step (f) will be carried out in step (g) as described above.

[0084] Examples of suitable filters or filtration processes are bag filters, cake filters or any other filter capable of retaining the resin colloid. In experimental tests, the particle size was 10 microns and absolutely for particles less than 1.0 micron. For example, multiple single bag filters include 30m 3 A single filter that can be used multiple times.

[0085] Suitable coagulants for use in the present invention are cationic or anionic polyamines.

[0086] Suitable flocculants for the present invention are cationic polyacrylamide, anionic polyacrylamide or a combination thereof. Polyacrylamides with different molecular weights can be used.

[0087] Examples

[0088] Example 1: Resin Response to Heat

[0089] In most cases, an increase in solution temperature will result in the dissociation of protons and a decrease in particle size. This results in a decrease in light attenuation. At higher temperatures, we have observed the dissociation of lignin from the resin particles.

[0090] It is also assumed that more soluble fatty acids will dissociate as the temperature increases.

[0091] In some cases, the surface of the resin cannot dissociate protons or other components to stabilize with increased charge or decreased size. In these cases, an increase in temperature may lead to increased agglomeration and light attenuation.

[0092] Measurements are performed at different wavelengths and temperatures. The data are analyzed to characterize the temperature dependence of the extinction. Thermal characterization provides parameters related to the stability and concentration of the resin.

[0093] When the amount of depositable resin is higher, delta is higher. These results are consistent with delta measurements providing a measure of the tendency to deposit or a measure of the viscosity of the resin.

[0094] Example 2: Filtering

[0095] In a preferred embodiment of the present invention, the condensate treatment may be filtration. Preferably, the filtration is performed using a filter having a pore size of less than 10 μm, more preferably less than 1 μm. The condensate purification treatment using a filter having a pore size of less than 10 μm provides a retention of 0.000082 g / L, and the purification treatment using a filter having a pore size of less than <1.0 μm provides a retention of 0.006754 g / L, when filtered at 300 m 3 / h condensate flow rate, this is equivalent to extracting 49 kg of material from the condensate per day. When combined, for example, the evaluation of the condensate with 0.2376 mg / L extract, according to the extract content analysis performed with dichloromethane solvent analysis and cell counting (Cytometry), the remaining total organic matter is 0.0984 g / L, providing a removal efficiency of 59% after the first filtration at 10 μm, and after two filtrations at 10 μm and 1 μm, the total organic matter is 0.0220 g / L, with a removal efficiency of 91% relative to the original condensate sample. According to the present invention, when only filtering is performed, the average chemical oxygen demand (COD) reaches 1.558 mg / L and the total organic carbon (TOC) reaches 393.2 mg / L; from the initial average COD of 1.637 mg / L and TOC of 392.9 mg / L condensate. In this sense, filtering does not significantly affect COD or TOC, even if it has a significant effect on the removal of organic matter.

[0096] Example 3: pH reduction

[0097] Another embodiment of the present invention is to reduce the pH of the condensate to provide a treated condensate. Sulfuric acid (10% H2SO4) is added so that the pH of the condensate is at least 6, preferably 5, before re-entering the fiber production line. In one experiment, the resin micelle count was increased from 1.1×10 8 Added to the treated condensate 1.30 × 10 8 , an increase of 18.4%. In another experiment, the micelle count in the resin was increased from 8.80 × 10 6 Added to the treated condensate is 1.32×10 7 , in increments of 50%.

[0098] Table 1 - Analysis of micelle formation by cell counting.

[0099]

[0100] Example 4: Filtration and pH adjustment:

[0101] In another experiment, a combination of filtration and pH adjustment was performed. 10 μm, 5 μm and 0.6 μm filters were used in the condensate adjusted to pH 3. The total hydrophobic particles were measured, and the particle count in the condensate was 2.3 particles / mL, which was reduced to 0.5 particles / mL in the treated condensate, while the average size of the particles in the condensate was 5.02 μm, which was reduced to 1 μm in the treated condensate, which corresponds to a reduction in the total surface area of ​​organic matter in the treated condensate. In addition, the number of compounds identified in the untreated condensate was reduced from 47 compounds to 30 compounds in the treated condensate, following extraction with solvent (DCM / dioxane), drying using a rotary evaporator and evaporation of the solvent. After drying, the components were extracted. Identification was performed using CG-MS.

[0102] A lower amount of hydrophobic particles after filtration can be observed. Filtration can be performed as usual, passing the condensate through a filter or orifice to physically retain the organic material, and introducing the treated condensate into a closed loop or subjecting the treated condensate to another treatment as described herein.

[0103] Example 5: Condensation:

[0104] Another embodiment of the present invention is the coagulation treatment of condensate. Suitable coagulants for use in the present invention are cationic or anionic polyamines.

[0105] Preferably, the coagulant is used in proportion to the organic matter present in the condensate before treatment. Preferably, 0.2 g to 10 g of coagulant is used per gram of organic matter.

[0106] Coagulation may be carried out as usual, mixing the condensate with a polymer coagulation composition; separating the coagulated particles from the treated condensate and introducing the treated condensate into a closed circuit, or subjecting the treated condensate to another treatment as described herein.

[0107] Example 6: Flocculation:

[0108] Another embodiment of the present invention is the flocculation treatment of condensate. Suitable flocculants of the present invention are cationic polyacrylamide, anionic polyacrylamide or a combination thereof. Polyacrylamides with different molecular weights can be used.

[0109] Preferably, the flocculant is used in proportion to the organic matter present in the condensate before treatment. The present invention discloses a flocculant in an amount of 0.3 to 20 grams of flocculant per gram of organic matter.

[0110] Flocculation may be carried out as usual, mixing the condensate with a flocculant composition; separating the flocculated particles from the treated condensate and introducing the treated condensate into a closed circuit, or subjecting the treated condensate to another treatment as described herein.

[0111] The condensate is left with the flocculant until the zeta potential reaches substantially -1 mV to -50 mV. In colloids, the zeta potential is the potential difference across the ionic layer around the charged colloidal ions. In other words, it is the potential in the interfacial double layer at the sliding surface. In general, the higher the zeta potential, the more stable the colloid. A zeta negative potential of less than -15 mV generally represents the beginning of particle agglomeration. When the zeta potential is equal to zero, the colloid will precipitate into a solid. Since the physical properties of suspensions and colloids depend largely on the properties of the particle-liquid interface, the zeta potential is known to have practical applications, among which we can list: destruction of undesirable colloidal dispersions in water and sewage treatment processes, reduction of the cost of additives by calculating the minimum amount required to achieve the desired effect, such as the amount of flocculant added to water during water treatment, characterization of the properties of clay-water systems, etc.

[0112] In the experiment conducted according to the present invention, after 15 minutes, it was noted that organic matter separated from the condensate. According to the present invention, when flocculation was performed, the chemical oxygen demand (COD) reached 281 mg / L and the total organic carbon (TOC) was 55.2 mg / L; from the initial condensate with a COD of 380 mg / L and a TOC of 95.3 mg / L. According to Table 2, the COD reduction in the experiment was:

[0113] Table 2

[0114] sample DQO(mg / L)C Untreated samples 380 The sample after coagulation 281 After condensation and filtration 282

[0115] The condensate is allowed to contact the coagulant for at least 1 minute, preferably 5 minutes.

[0116] Example 7: Coagulation and flocculation:

[0117] In another embodiment of the invention, there is a combination of a coagulant and a flocculant. Ideally, the resins sought to be removed are resins having as main organic constituent compounds, such as butyric acid, thiophenecarboxylic acid, vanillic acid, syringic acid, octasulfur, β-sitosterol, dihydro-2-furanone and glutaric acid.

[0118] Example 8: Results:

[0119] When a combination of coagulants and / or flocculants and filtration is used, the process of the invention provides a resin reduction of at least 50 wt%, preferably 80 wt%, more preferably 90 wt%, even more preferably 98 wt% in the condensate. In addition, the invention provides a condensate having a TOC value of less than 60 mg / L. In addition, the invention provides a process that reduces the TOC in the treated condensate by at least 10%, preferably by 20%, more preferably by 40%, even more preferably by 60% of the TOC in the treated condensate compared to the untreated condensate.

Claims

1. A method for treating condensate in a pulping process, characterized in that The following steps are involved: a) identifying colloidal organic compounds in the condensate; b) subjecting the condensate to a chemical or chemico-physical treatment, wherein the treatment comprises a combination of coagulation and flocculation, wherein the coagulation is performed using at least a cationic polyamine or an anionic polyamine and the flocculation is performed using at least a cationic polyacrylamide, an anionic polyacrylamide or a combination thereof; and c) Reduce the contamination of the condensate by feeding it to the final washer stage or some other stage of the pulping process. The method according to claim 1 , wherein the organic compound is a resin.

3. The method according to claim 1 or 2, wherein in step a) the total carbon content (TOC) of the condensate is at least 30 mg / L.

4. The method according to claim 1 or 2, wherein the coagulation is performed using 0.2 g to 10 g of the coagulating agent per gram of the organic compound.

5. The method of claim 1 or 2, wherein the condensate is contacted with the coagulant for at least 2 minutes.

6. The method of claim 5, wherein the condensate is contacted with the coagulant for at least 5 minutes.

7. The method according to claim 1 or 2, wherein 0.3 g to 20 g of flocculant is used for flocculation per gram of the organic compound.

8. The method according to claim 1 or 2, wherein flocculation is performed until the zeta potential is between -1 mV and -50 mV.

9. A method according to claim 1 or 2, wherein the condensate is from an evaporation step of a pulping operation.

10. A process according to claim 9, wherein the condensate is from a black liquor evaporation step.

11. A process according to claim 1 or 2, wherein the treated condensate is returned to the pulping operation in countercurrent.

12. A process according to claim 11 wherein the treated condensate is returned in countercurrent to the washing system of the pulping operation.

13. The method according to claim 1 or 2, wherein the pulping process is kraft pulping or modified kraft pulping.

14. The method according to claim 12, wherein treatment of the condensate is performed before the condensate is returned in a closed loop to a washing system of the pulping process.

15. The method of claim 1 or 2, wherein the treatment of the condensate provides a resin reduction of at least 50 wt% in the treated condensate.

16. A method according to claim 15, wherein the treatment of the condensate provides a resin reduction of at least 80 wt% in the treated condensate.

17. A method according to claim 16, wherein the treatment of the condensate provides a resin reduction of at least 90 wt% in the treated condensate.

18. The method of claim 17, wherein the treatment of the condensate provides a resin reduction of at least 98 wt% in the treated condensate.

19. The method according to claim 1 or 2, wherein: The method provides a TOC reduction of at least 10% of the TOC in the treated condensate when compared to untreated condensate.

20. The method according to claim 19, wherein: The method provided a 20% reduction in TOC in the treated condensate when compared to untreated condensate.

21. The method according to claim 19, wherein: The method provided a 40% reduction in TOC in the treated condensate when compared to untreated condensate.

22. The method according to claim 19, wherein: The method provided a 60% reduction in TOC in the treated condensate when compared to untreated condensate.

23. The method of claim 1 or 2, wherein the TOC value of the treated condensate is less than 60 mg / L.

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