FI126748B - Process and system for treating solid waste containing calcium - Google Patents

Process and system for treating solid waste containing calcium Download PDF

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Publication number
FI126748B
FI126748B FI20145851A FI20145851A FI126748B FI 126748 B FI126748 B FI 126748B FI 20145851 A FI20145851 A FI 20145851A FI 20145851 A FI20145851 A FI 20145851A FI 126748 B FI126748 B FI 126748B
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Finland
Prior art keywords
calcium
calcium chloride
solution
solid waste
hydrochloric acid
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FI20145851A
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Finnish (fi)
Swedish (sv)
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FI20145851A7 (en
Inventor
Kari Saari
Tomi Heikkinen
Pasi Virtanen
Folke Örså
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Upm Kymmene Corp
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Priority to FI20145851A priority Critical patent/FI126748B/en
Publication of FI20145851A7 publication Critical patent/FI20145851A7/en
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/20—Halides
    • C01F11/24—Chlorides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
    • B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/50—Carbon dioxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/04—Regeneration of pulp liquors or effluent waste waters of alkali lye

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • General Chemical & Material Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Water Supply & Treatment (AREA)
  • Processing Of Solid Wastes (AREA)

Description

METHOD AND SYSTEM FOR THE TREATMENT OF CALCIUM-CONTAINING SOLID WASTE
FIELD OF THE INVENTION
The invention relates to a method for the treatment of calcium-containing solid waste obtainable from a chemical recovery process of a chemical pulping process. The invention further relates to a system for the treatment of and to the use of a calcium-containing solid waste obtainable from a chemical recovery process of a chemical pulping process.
BACKGROUND OF THE INVENTION
Chemical pulping processes and the chemical recovery processes involved produce several waste byproducts that need to be disposed of. Traditionally, solid waste such as green liquor dregs produced in the chemical recovery processes has been landfilled. However, as environmental regulations restricting waste disposal tend to become stricter, there is a need to reduce the total amount of the waste and and the content of harmful substances in it. WO 2010/107511 describes a method for obtaining particulate calcium carbonate and activated carbon particles from a pulp mill. US 2004/0055715 discloses a method of treating solid containing material derived from effluent or sludge from a plant for de-inking paper, the material containing calcium. CN 101648725 describes a produciton method of industrial calcium chloride from shells. RU 2291109 describes a method for preparing calcium chloride. CN 102476822 discloses a pharmaceutical-grade calcium chloride production process.
PURPOSE OF THE INVENTION
The purpose of the invention is to provide a new type of method for the treatment of calcium-containing solid waste obtainable from a chemical recovery process of a chemical pulping process. Further, the purpose of the invention is to provide a system for the treatment of calcium-containing solid waste obtainable from a chemical recovery process of a chemical pulping process.
SUMMARY
The method according to the present invention is characterized by what is presented in claim 1.
The system according to the present invention is characterized by what is presented in claim 15.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:
Fig. 1 is a schematic illustration of a system for implementing the method for the treatment of a calcium-containing solid waste obtainable from a chemical recovery process of a chemical pulping process.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method for the treatment of a calcium-containing solid waste obtainable from a chemical recovery process of a chemical pulping process, wherein the method comprises treating the calcium-containing solid waste with hy drochloric acid so that a solution comprising calcium chloride (CaCl2) and carbon dioxide (C02) is formed.
In the context of this specification, the term "calcium-containing solid waste" should be understood as referring to a calcium-containing solid waste obtainable from a chemical recovery process of a chemical pulping process. The calcium-containing solid waste may, in principle, be any solid waste obtainable from a chemical recovery process of a chemical pulping process, for instance a causticizing process. The causticizing process may, in this context, include also the processing of green liquor and green liquor dregs. The calcium contained in the solid waste may be e.g. in the form of calcium carbonate (CaC03) , calcium oxide (CaO), or calcium hydroxide (Ca(OH)2). Suitable calcium-containing solid wastes may include e.g. green liquor dregs, lime mud, lime slaker grits, solid waste obtainable from purification of flue gas from lime sludge reburning, burnt lime and any mixtures thereof. The calcium-containing solid waste may comprise various other components derived from the raw material for pulping, such as wood; for instance magnesium in the form of carbonate, oxide or hydroxide, aluminium, phosphorus (e.g. in the form of phosphates), manganese, sodium, iron, zinc, various heavy metals, and/or incombustible material, such as material derived from lignin.
The calcium-containing solid waste may be pretreated prior to treatment with hydrochloric acid. For instance, one or more of the other components of the calcium-containing solid waste indicated in the previous paragraph may be removed from the calcium-containing solid waste prior to the treatment with hydrochloric acid.
The calcium-containing solid waste may be dry or slurried e.g. with water prior to treatment. The pH of the calcium-containing solid waste is typically alkaline prior to treatment.
In an embodiment, the calcium-containing solid waste comprises calcium carbonate (CaC03) .
In an embodiment, the calcium-containing solid waste comprises at least 30 %, or at least 40 % calcium carbonate by the dry weight of calcium carbonate to the dry weight of the calcium-containing solid waste.
The calcium-containing solid waste may comprise, for instance, 40-50 %, 40-60 %, or 30-70 % calcium carbonate by the dry weight of calcium carbonate to the dry weight of the calcium-containing solid waste.
In an embodiment, the calcium-containing solid waste is carbonated prior to the treatment with hydrochloric acid. The carbonation may be done e.g. by adding carbon dioxide to a solution or slurry of the calcium-containing solid waste. The carbonation may increase the calcium carbonate content of the calcium-containing solid waste, e.g. of burnt lime.
In an embodiment, the calcium-containing solid waste is selected from the group consisting of green liquor dregs, lime mud, lime slaker grits, solid waste obtainable from purification of flue gas from lime sludge reburning, burnt lime, wherein the burnt lime is optionally carbonated, and any mixtures thereof .
In an embodiment, the calcium-containing solid waste is green liquor dregs. The green liquor dregs may also comprise lime mud, for instance green liquor dregs that are separated from green liquor using a filter precoated with lime mud.
In an embodiment, incombustible material is removed from the green liquor dregs prior to the treatment with hydrochloric acid. The incombustible material (carbon fraction) may have a lower specific weight than other components of the green liquor dregs. The removal may be done e.g. by flotation or foaming.
In an embodiment, the calcium-containing solid waste is lime mud.
In an embodiment, the calcium-containing solid waste is lime slaker grits.
In an embodiment, the calcium-containing solid waste is solid waste obtainable from purification of flue gas from lime sludge reburning. Solid waste obtainable from purification of flue gas from lime sludge reburning typically contains a significant amount of calcium carbonate. It may be obtained from an electrostatic precipitator used for purifying flue gases from a lime sludge reburning kiln.
In an embodiment, the calcium-containing solid waste is burnt lime. Burnt lime comprising calcium mainly in the form of CaO may be carbonated by adding carbon dioxide to a solution or slurry of burnt lime (hydrated lime) prior to the treatment with hydrochloric acid.
The method may be used for treatment of calcium-containing solid waste from a chemical pulping mill, in which chemical pulp is produced using the so-called sulphate or kraft process.
In this context, the term "pulp" should be understood as referring to a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from a natural fibre based material. So-called kraft or sulphate processes can be used for producing pulp.
In an embodiment, the chemical pulping process is a kraft pulping process.
The treatment may be performed e.g. by mixing the calcium-containing solid waste and hydrochloric acid in a reactor.
In this context, the term "hydrochloric acid" refers, as it commonly does in the art, to an aqueous solution of hydrogen chloride (HC1). Concentrations of HC1 of about 40 % (w/w) or slightly above may be obtained. Typically, hydrochloric acid for industrial purposes is available as solutions with a hydrogen chloride concentration up to about 38 % (w/w) . The concentration of the hydrogen chloride is not critical for the treatment, and even fairly diluted hydrochloric acid may be used for the treatment according to one or more embodiments. Higher concentrations of hydrochloric acid may be more economic. In embodiments in which concentrated hydrochloric acid is used, the concentration of the obtainable solution comprising calcium chloride is high, and the need for concentration or evaporation of the solution comprising calcium chloride may be reduced or eliminated.
In the context of this specification, the term "hydrochloric acid" may also refer to an aqueous solution consisting of hydrochloric acid.
In an embodiment, the concentration of hydrogen chloride in the hydrochloric acid is at least 10 % (w/w), or at least 20 % (w/w), or at least 30 % (w/w), or 10 - 40 % (w/w) , or 20 - 40 % (w/w) , or 30 - 38 % (w/w).
In an embodiment, the molar ratio of hydrogen chloride contained in the hydrochloric acid to calcium contained in the solid waste is at least about 1:3, or at least about 1:2, or at least about 1:1, or in the range of about 1:1 to about 2:1, or at least about 2 :1.
The treatment may be done by adding hydrochloric acid to the calcium-containing solid waste, or the hydrochloric acid may be mixed with the calcium-containing solid waste.
The method may be implemented as a continuous or a batch process.
In an embodiment, the method comprises mixing the calcium-containing solid waste with hydrochloric acid to obtain a mixture; and adjusting the pH of the mixture to a pH below 7, or to a pH below about 5, or to a pH in the range of about 2 to about 6.5, or to a pH in the range of about 2 to about 5.
The calcium-containing solid waste may be dry or slurried prior to mixing with hydrochloric acid.
In an embodiment, the method comprises mixing the dry or slurried calcium-containing solid waste with hydrochloric acid to obtain a mixture; and adjusting the pH of the mixture to a pH below 7, or to a pH below about 5, or to a pH in the range of about 2 to about 6.5, or to a pH in the range of about 2 to about 5. A suitable pH for the mixture obtainable by mixing the calcium-containing solid waste with hydrochloric acid is an acidic pH, i.e. a pH below 7; in such a pH a solution comprising calcium chloride is obtained. The pH may also be below about 5. If the pH is below about 2, various other components such as impurities of the calcium-containing solid waste will also be readily solubilized, and thus the solution comprising calcium chloride obtainable may contain increased amounts of other components such as impurities, for instance heavy metals.
The temperature during the treatment is not critical, and the treatment may be performed e.g. in ambient temperature, or at a temperature of 0 - 100°C. The reaction between the solid waste and the hydrochloric acid may, however, produce heat; cooling is typically not necessary but may be used, if desired.
In an embodiment, the method comprises separating the solution comprising calcium chloride. The separation may be effected e.g. by filtration, cen trifugation, decantation, clarification, flotation or sedimentation.
The method may comprise one or more steps comprising treatment with hydrochloric acid and separation of the solution comprising calcium chloride obtained. Additional treatment steps of non-reacted calcium may improve the efficiency and yield of calcium chloride obtainable.
In an embodiment, the method comprises separating solid matter suspended in the solution comprising calcium chloride; and treating the separated solid matter with hydrochloric acid so that a secondary solution comprising calcium chloride and carbon dioxide is formed.
In an embodiment, the method comprises mixing the separated solid matter with hydrochloric acid to obtain a mixture; and adjusting the pH of the mixture to a pH below 7, or to a pH below about 5, or to a pH in the range of about 2 to about 6.5, or to a pH in the range of about 2 to about 5.
The separated solid matter may be dry or slurried prior to mixing with hydrochloric acid.
The separated solid matter, i.e. solid matter separated from the solution comprising calcium chloride, may still comprise significant amounts of calcium. Further, it may be beneficial to perform a first treatment of the calcium-containing solid waste so that a portion (but not all) of the calcium contained in the solid waste is converted to calcium chloride. This may improve yield of calcium chloride and/or reduce the amount of impurities in the solution comprising calcium chloride.
The secondary solution comprising calcium chloride may be combined with the solution comprising calcium chloride, i.e. the first solution comprising calcium chloride, or it may be recovered and treated further separately. The secondary solution comprising calcium chloride may also comprise remaining solid matter suspended therein, e.g. matter that is not soluble in and does not react with the hydrochloric acid. In an embodiment, the method comprises separating the remaining solid matter suspended in the secondary solution comprising calcium chloride.
The remaining solid matter may be separated e.g. in the same manner as the solid matter suspended in the (first) solution comprising calcium chloride. The pH of the recovered solid matter may also be adjusted e.g. by adding an acidic or an alkaline agent. The separated solid matter may be washed e.g. with water. The washing may allow removing and/or recovering any remaining calcium chloride and may adjust the pH of the recovered solid matter. The solution obtainable from washing the remaining solid matter may be recovered and optionally combined with the solution comprising calcium chloride and/or with the secondary solution comprising calcium chloride.
In an embodiment, the method comprises treating the calcium-containing solid waste with hydrochloric acid so that a solution comprising calcium chloride and carbon dioxide is formed; separating the solution comprising calcium chloride and solid matter suspended in the solution comprising calcium chloride; treating the separated solid matter with hydrochloric acid so that a secondary solution comprising calcium chloride and carbon dioxide is formed; separating the secondary solution comprising calcium chloride and the remaining solid matter suspended in the secondary solution comprising calcium chloride; and optionally washing the separated remaining solid matter.
In an embodiment, the method comprises mixing the dry or slurried calcium-containing solid waste with hydrochloric acid to obtain a mixture; adjusting the pH of the mixture to a pH below 7, or to a pH below about 5, or to a pH in the range of about 2 to about 6.5, or to a pH in the range of about 2 to about 5 to obtain a solution comprising calcium chloride and carbon dioxide; separating the solution comprising calcium chloride and solid matter suspended in the solution comprising calcium chloride; mixing the separated solid matter with hydrochloric acid to obtain a mixture; adjusting the pH of the mixture to a pH below 7, or to a pH below about 5, or to a pH in the range of about 2 to about 6.5, or to a pH in the range of about 2 to about 5 to obtain a secondary solution comprising calcium chloride and carbon dioxide; separating the secondary solution comprising calcium chloride and the remaining solid matter suspended in the secondary solution comprising calcium chloride; and optionally washing the separated remaining solid matter.
In an embodiment, the method comprises recovering the solution comprising calcium chloride, the carbon dioxide and/or the secondary solution comprising calcium chloride. For possible end uses or disposal, the calcium chloride in the solution or solutions obtainable may be treated further. Various methods for recovering carbon dioxide gas are known.
In an embodiment, the method comprises adjusting the pH of the solution comprising calcium chloride and/or the secondary solution comprising calcium chloride.
In an embodiment, the method comprises adjusting the pH the separated and/or recovered solution comprising calcium chloride and/or the secondary solution comprising calcium chloride. The pH may be adjusted with an acidic agent or with an alkaline agent, such as Ca(OH)2, CaO, NaOH, NH4OH or a mixture thereof.
The pH may be adjusted to an essentially neutral pH, e.g. to a pH or about 7, or to a pH of about 6 to about 8.
In an embodiment, the method comprises adjusting the concentration of the solution comprising calcium chloride and/or the secondary solution comprising calcium chloride. The concentration of the separated and/or recovered solution comprising calcium chloride may be adjusted e.g. by adding water or an aqueous solution. The adjustment may also be made online during or after the treatment e.g. in a reactor by monitoring the density of the treatment mixture (i.e. mixture comprising calcium-containing solid waste, hydrochloric acid and the solution comprising calcium chloride) and by adjusting the density of the treatment mixture. Such adjustment may also adjust the concentration of the separated and/or recovered calcium chloride solution.
The separated and/or recovered solution comprising calcium chloride and/or the secondary solution comprising calcium chloride may comprise e.g. Mg in the form to MgCl2 and other components, including impurities such as heavy metals. Such other components and impurities may be removed from the separated and/or recovered solution comprising calcium chloride and/or the secondary solution comprising calcium chloride using a suitable purification method, for instance precipitation.
In an embodiment, the method comprises concentrating the solution comprising calcium chloride and/or the secondary solution comprising calcium chloride .
In an embodiment, the method comprises crystallizing, drying and/or flaking the calcium chloride, i.e. the calcium chloride obtainable from the solution comprising calcium chloride and/or the secondary solution comprising calcium chloride.
Any methods for concentrating, crystallizing, drying and flaking calcium chloride known in the art may, in principle, be used.
The yield of calcium chloride may be e.g. about 60 % (w/w) of the calcium contained in the calcium-containing solid waste, but may depend e.g. on the type of the calcium-containing solid waste, the amount of the hydrochloric acid and other factors.
In an embodiment, the method comprises purifying, compressing and/or liquefying the carbon dioxide. The purifying may comprise e.g. washing the carbon dioxide to remove acids and/or purifying the carbon dioxide using an activated carbon filter.
The present invention also relates to use of a calcium-containing solid waste obtainable from a chemical recovery process of a chemical pulping process for producing calcium chloride and/or carbon dioxide .
In the context of the use and the system, the calcium-containing solid waste may be any calcium-containing solid waste described in this specification .
In an embodiment, the calcium-containing solid waste comprises calcium carbonate.
In an embodiment, the calcium-containing solid waste comprises at least 30 %, or at least 40 % calcium carbonate by the dry weight of calcium carbonate to the dry weight of the calcium-containing solid waste.
In an embodiment, the calcium-containing solid waste obtainable from a chemical recovery process of a chemical pulping process is selected from the group consisting of green liquor dregs, lime mud, lime slaker grits, solid waste obtainable from purification of flue gas from lime sludge reburning, burnt lime, wherein the burnt lime is optionally carbonated, and any mixtures thereof.
In an embodiment, the calcium-containing solid waste is green liquor dregs.
The present invention further relates to a system for the treatment of a calcium-containing solid waste obtainable from a chemical recovery process of a chemical pulping process, wherein the system comprises an apparatus for mixing the calcium-containing solid waste with hydrochloric acid to obtain a solution comprising calcium chloride and carbon dioxide; and a separation apparatus for separating the solution comprising calcium chloride from solid matter suspended in the solution comprising calcium chloride.
The apparatus for mixing the calcium-containing solid waste with hydrochloric acid to obtain a solution comprising calcium chloride and carbon dioxide may comprise e.g. a reservoir, tank or reactor. The apparatus may further comprise means for mixing them, for instance a mixer or impeller.
The separation apparatus for separating the solution comprising calcium chloride from solid matter suspended in the solution comprising calcium chloride may be e.g. a filtration apparatus, a centrifugation apparatus, a decantation apparatus, a clarification apparatus, a flotation apparatus or a sedimentation apparatus .
The apparatus for mixing the calcium-containing solid waste with hydrochloric acid to obtain a solution comprising calcium chloride and carbon dioxide may have a flow connection, e.g. a conduit or piping, to the separation apparatus for conveying the mixture to the separation apparatus.
In an embodiment, the system further comprises an apparatus for mixing the separated solid matter with hydrochloric acid to obtain a secondary solution comprising calcium chloride and carbon dioxide; and a separation apparatus for separating the secondary solution comprising calcium chloride from solid matter suspended in the secondary solution comprising calcium chloride.
In an embodiment, the apparatus for mixing the separated solid matter, i.e. solid matter separated from the solution comprising calcium chloride, with hydrochloric acid to obtain a secondary solution comprising calcium chloride and carbon dioxide is a second apparatus for mixing the separated solid matter with hydrochloric acid to obtain a secondary solution comprising calcium chloride and carbon dioxide. In an embodiment, the separation apparatus for separating the secondary solution comprising calcium chloride from solid matter suspended in the secondary solution comprising calcium chloride is a second separation apparatus for separating the secondary solution comprising calcium chloride from solid matter suspended in the secondary solution comprising calcium chloride.
The apparatus for mixing the separated solid matter with hydrochloric acid to obtain a secondary solution comprising calcium chloride and carbon dioxide may be similar to or different from the apparatus for mixing the calcium-containing solid waste with hydrochloric acid to obtain a solution comprising calcium chloride and carbon dioxide. It may comprise e.g. a reservoir, tank or reactor, and may further comprise means for mixing the separated solid matter and the hydrochloric acid, for instance a mixer or impeller.
In an embodiment, the system further comprises an apparatus for washing the solid matter separated from the solution comprising calcium chloride and/ or the secondary solution comprising calcium chloride. Such an apparatus allows for washing the solid matter e.g. with water in order to remove any remaining calcium chloride and/or hydrochloric acid from the solid matter .
The carbon dioxide gas produced in the apparatus for mixing the calcium-containing solid waste with hydrochloric acid and/or in the apparatus for mixing the separated solid matter with hydrochloric acid may be removed, or it may be recovered. For removal, said apparatus or apparatuses may comprise an outlet orifice or conduit for removing carbon dioxide.
In an embodiment, the system comprises an apparatus for recovering the carbon dioxide. Various types of apparatuses for recovering carbon dioxide are known and may be utilized in the system. For instance, the carbon dioxide may be suctioned using a vacuum apparatus .
In an embodiment, the system comprises a purification apparatus for purification of the recovered carbon dioxide. Such a purification apparatus may comprise e.g. an activated carbon filter. In an embodiment, the system comprises a liquefaction apparatus for liquefying the recovered carbon dioxide.
The system may also comprise e.g. an evaporation apparatus for evaporating water from the solutionis) comprising calcium chloride. The system may further comprise an apparatus for drying; an apparatus for crystallizing; and/or an apparatus for flaking the calcium chloride.
In an embodiment, the system comprises a chemical pulping system. Such a chemical pulping sys tem may comprise e. g. a digestion apparatus for cooking pulp; a washing apparatus for washing pulp; and a bleaching apparatus for bleaching pulp.
In an embodiment, the system comprises a caus-ticizing system. The causticizing system may comprise a soda recovery unit, a lime slaking unit, a lime sludge reburning kiln, and/or an apparatus purification of flue gas from lime sludge reburning, such as an electrostatic precipitator.
In an embodiment, the system comprises a separation apparatus for separating green liquor dregs. Such a separation apparatus may comprise e.g. a green liquor dregs filter or separator. The green liquor dregs filter may be precoated with lime mud.
The embodiments of the invention described hereinbefore may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment of the invention. A method, a system or a use, to which the invention is related, may comprise at least one of the embodiments of the invention described hereinbefore.
An advantage of the present invention is that the calcium-containing solid waste may be converted to a salt product that is not particularly harmful to the environment.
An advantage of the method according to the present invention is that it is a low cost process. It also does not require significant investments for equipment and reagents. For example, hydrochloric acid is readily available e.g. as a byproduct of various reactions .
An advantage of the method according to the present invention is that the solution comprising calcium chloride or the calcium chloride purified therefrom may have various uses e.g. as brine or for ice and dust control on roads.
An advantage of the method according to the present invention is that the carbon dioxide produced may have various uses e.g. in the industry.
EXAMPLES
Reference will now be made in detail to the embodiments of the present invention, an example of which is illustrated in the accompanying drawing.
The description below discloses some embodiments of the invention in such a detail that a person skilled in the art is able to utilize the invention based on the disclosure. Not all steps of the embodiments are discussed in detail, as many of the steps will be obvious for the person skilled in the art based on this specification.
For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components.
Figure 1 illustrates a system according to one embodiment of the present invention that is suitable for the treatment of calcium-containing solid waste obtainable from a chemical recovery process of a chemical pulping process. Various components that may be a part of the system have not been included in this schematic illustration for simplicity.
In this exemplary embodiment, the system comprises an apparatus 1 for mixing the calcium-containing solid waste with hydrochloric acid to obtain a solution comprising calcium chloride and carbon dioxide, such as a reactor. The reactor may comprise e.g. a reservoir, which may be internally coated with an acid resistant coating. The apparatus 1 may further comprise means for mixing, for instance a mixer or an impeller, for mixing the calcium-containing solid waste with hydrochloric acid. The system also comprises a conduit 6 for conveying the calcium-containing solid waste to the apparatus 1 and a conduit 7 for conveying hydrochloric acid to the apparatus 1. The conduits 6 and 7 may be connected to a reservoir containing the calcium-containing solid waste and hydrochloric acid, respectively. The conduit 6 may also be connected to a separation apparatus for separating green liquor dregs and/or to a caustization system. In the apparatus 1, the calcium-containing solid waste and hydrochloric acid form a reaction mixture, and a solution comprising calcium chloride and carbon dioxide is produced. A conduit 7 for conveying an acidic and/or an alkaline agent, such as hydrochloric acid and/or Ca(OH)2, is connected to the apparatus 1 for mixing the calcium-containing solid waste with hydrochloric acid and allows for adjusting the pH of the mixture of the calcium-containing solid waste and the hydrochloric acid. A conduit 8 for conveying water is connected to the apparatus 1 and allows for the adjustment of the concentration and/or density of the mixture in the apparatus 1.
The carbon dioxide produced may be collected and recovered by an apparatus 5 for recovering the carbon dioxide, which is connected via a flow connection 9, e.g. a conduit or a piping, to the apparatus 1 for mixing the calcium-containing solid waste with hydrochloric acid. The system further comprises an apparatus 11 for the treatment of the recovered carbon dioxide. In this embodiment, it comprises an apparatus for the purification and for liquefying the carbon dioxide. The apparatus 5 for recovering the carbon dioxide may be in flow connection 10 to the apparatus 11 for the treatment of the recovered carbon dioxide.
The reaction mixture will typically comprise, in addition to the calcium chloride, solid matter suspended therein. The system therefore comprises a separation apparatus 2 for separating the solid matter suspended in the solution comprising calcium chloride from said solution. A flow connection 13, e.g. a con duit or a piping, for conveying the solution comprising calcium chloride from the separation apparatus 2 is provided. The solid matter is, in this embodiment, conveyed to an apparatus 3 for mixing the separated solid matter with hydrochloric acid to obtain a secondary solution comprising calcium chloride and carbon dioxide. The apparatus 3 may be similar to the apparatus 1. The separation apparatus 2 and the apparatus 3 for mixing the separated solid matter with hydrochloric acid may be connected via a flow connection 12, such as a conduit or a piping, for conveying the separated solid matter to the apparatus 3. A conduit 7 for conveying an acidic and/or an alkaline agent, such as hydrochloric acid and/or Ca(OH)2 is connected to the apparatus 3 for mixing the separated solid matter with hydrochloric acid and allows for adjusting the pH of the mixture of the solid matter and the hydrochloric acid. A conduit 8 for conveying water is connected to the apparatus 3 and allows for the adjustment of the concentration and/or density of the mixture. The system further comprises a separation apparatus 4 for separating the remaining solid matter suspended in the secondary solution comprising calcium chloride, if any, and carbon dioxide. The separation apparatus 4 has a flow connection 14, e.g. a conduit or a piping, to an apparatus 15 for recovering the secondary solution comprising calcium chloride. The apparatus 15 for recovering the secondary solution comprising calcium chloride may again comprise a conduit 7 for conveying an acidic and/or an alkaline agent and a conduit 8 for conveying water to the secondary solution comprising calcium chloride. The conduits 7 and 8 allow for adjusting the pH and the concentration and density of the recovered secondary solution comprising calcium chloride. The recovered secondary solution comprising calcium chloride may be removed from the system for disposal or end use, or it may be combined with the solution comprising calcium chloride obtained from the separation apparatus 2. To this end, a conduit 20 for conveying the secondary solution comprising calcium chloride may be provided.
Any solid matter separated from the secondary solution comprising calcium chloride may be conveyed via a flow connection 16, e.g. a conduit or a piping, to an apparatus 17 for washing the solid matter separated from the secondary solution comprising calcium chloride. A conduit 8 for conveying water to the apparatus 17 for washing the solid matter separated from the secondary solution comprising calcium chloride may be provided for washing the separated solid matter. The solution obtainable from washing the separated solid matter may be conveyed to an apparatus 19 for recovering the solution obtainable from washing the separated solid matter via a flow connection 18. A flow connection 20 between the apparatus 15 for recovering the secondary solution comprising calcium chloride and the apparatus 19 for recovering the solution obtainable from washing the separated solid matter may be provided for combining the solutions. Again, the apparatus 19 for recovering the solution obtainable from washing the separated solid matter may comprise a conduit 7 for conveying an acidic and/or an alkaline agent and a conduit 8 for conveying water for adjusting pH, concentration and/or density of the recovered solution (s) .
The system may further comprise an apparatus 21 for treating the recovered solution(s) comprising calcium chloride. The apparatus 21 may comprise e.g. an apparatus for evaporating the solution(s) comprising calcium chloride, or an apparatus for drying, crystallizing and/or flaking the calcium chloride.
Any connections and flow connections between components of the system may be direct or indirect. EXAMPLE 1 - Treatment of green liquor dregs with hydrochloric acid
Green liquor dregs samples were obtained from a kraft pulp mill and slurried with water. Hydrochloric acid (36 % w/w) was mixed with the slurry and the mixture was allowed to react.
Solid matter was separated from the calcium chloride solution obtained by filtration. Calcium content of the solution was determined by flame atomic absorption spectrometry and was found to be approx. 18 g/1.
It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.

Claims (17)

1. Menetelmä kemiallisen massanvalmistuspro-sessin kemiallisesta talteenottoprosessista saatavissa olevan kalsiumpitoisen kiinteän jätteen käsittelemiseksi, jossa menetelmä käsittää käsitellään kalsiumpitoista kiinteää jätettä suolahapolla, niin että muodostuu hiilidioksidia ja kalsiumkloridia käsittävä liuos; erotetaan kiinteä aine, joka on suspensoituna kalsiumkloridia käsittävään liuokseen, käsitellään erotettua kiinteää ainetta suolahapolla, niin että muodostuu hiilidioksidia ja kalsiumkloridia käsittävä toinen liuos, ja otetaan talteen kalsiumkloridia käsittävä liuos ja/tai kalsiumkloridia käsittävä toinen liuos.A process for treating calcium-containing solid waste from a chemical recovery process of a chemical pulping process, the method comprising treating a calcium-containing solid waste with hydrochloric acid to form a solution comprising carbon dioxide and calcium chloride; separating the solid suspended in the calcium chloride solution, treating the separated solid with hydrochloric acid to form a second solution of carbon dioxide and calcium chloride, and recovering the calcium chloride solution and / or the second calcium chloride solution. 2. Patenttivaatimuksen 1 mukainen menetelmä, jossa kalsiumpitoinen kiinteä jäte käsittää kalsium-karbonaattia .The method of claim 1, wherein the calcium-containing solid waste comprises calcium carbonate. 3. Patenttivaatimuksen 1 tai 2 mukainen mene telmä, jossa kalsiumpitoinen kiinteä jäte käsittää vähintään 30 % tai vähintään 40 % kalsiumkarbonaattia kalsiumkarbonaatin kuivapainon perusteella suhteessa kalsiumpitoisen kiinteän jätteen kuivapainoon.The method of claim 1 or 2, wherein the calcium-containing solid waste comprises at least 30% or at least 40% calcium carbonate based on the dry weight of the calcium carbonate relative to the dry weight of the calcium-containing solid waste. 4. Jonkin patenttivaatimuksista 1-3 mukainen menetelmä, jossa kalsiumpitoinen kiinteä jäte valitaan ryhmästä, joka koostuu viherlipeäsakasta, mee-sasta, kalkinsammutuslaitteen hiekasta, kiinteästä jätteestä, joka on saatavissa savukaasun puhdistuksesta meesanpolton yhteydessä, poltetusta kalkista, jossa poltettu kalkki on valinnaisesti karbonoitua, ja niiden mistä tahansa seoksista.The method according to any one of claims 1 to 3, wherein the calcium-containing solid waste is selected from the group consisting of green liquor precipitate, honey, lime slurry sand, solid waste obtainable in flue gas purification during lime sludge combustion, lime burned with lime, optionally burnt lime, any mixtures thereof. 5. Jonkin patenttivaatimuksista 1-4 mukai nen menetelmä, jossa vetykloridin konsentraatio suolahapossa on vähintään 10 % (w/w) tai vähintään 20 % (w/w) tai vähintään 30 % (w/w) tai 10 - 40 % (w/w) tai 20 - 40 % (w/w) tai 30 - 38 % (w/w).The process of any one of claims 1 to 4, wherein the concentration of hydrochloride in hydrochloric acid is at least 10% (w / w) or at least 20% (w / w) or at least 30% (w / w) or 10-40% (w / w). w) or 20-40% (w / w) or 30-38% (w / w). 6. Jonkin patenttivaatimuksista 1-5 mukainen menetelmä, jossa suolahapon sisältämän vetyklori-din moolisuhde kalsiumpitoisen kiinteän jätteen sisältämään kalsiumiin on vähintään noin 1:3 tai vähintään noin 1:2 tai vähintään noin 1:1 tai alueella noin 1:1 - noin 2:1 tai vähintään noin 2:1.The process according to any one of claims 1 to 5, wherein the molar ratio of hydrochloride in hydrochloric acid to calcium in the calcium-containing solid waste is at least about 1: 3 or at least about 1: 2 or at least about 1: 1 or in the range of about 1: 1 to about 2: 1 or at least about 2: 1. 7. Jonkin patenttivaatimuksista 1-6 mukainen menetelmä, jossa menetelmä käsittää sekoitetaan kuivaa tai lietettyä kalsiumpi-toista kiinteää jätettä suolahapon kanssa seoksen saamiseksi; ja säädetään seoksen pH-arvo pH-arvoksi, joka on alle 7, tai pH-arvoksi, joka on alle 5, tai pH-arvoksi, joka on alueella noin 2 - noin 6,5, tai pH-arvoksi, joka on alueella noin 2 - noin 5.The method of any one of claims 1 to 6, wherein the method comprises mixing dry or slurried calcium-containing solid waste with hydrochloric acid to form a mixture; and adjusting the pH of the mixture to a pH of less than 7, or to a pH of less than 5, or to a pH of from about 2 to about 6.5, or to a pH of from about 2 to about 5. 8. Jonkin patenttivaatimuksista 1-7 mukainen menetelmä, jossa menetelmä käsittää kalsiumklori-dia käsittävän liuoksen erottamisen.The process according to any one of claims 1 to 7, wherein the process comprises separating a solution comprising calcium chloride. 9. Jonkin patenttivaatimuksista 1-8 mukainen menetelmä, jossa menetelmä käsittää hiilidioksidin ottamisen talteen.The process according to any one of claims 1 to 8, wherein the process comprises capturing carbon dioxide. 10. Jonkin patenttivaatimuksista 1-9 mukainen menetelmä, jossa menetelmä käsittää erotetun ja/tai talteen otetun kalsiumkloridia käsittävän liuoksen ja/tai kalsiumkloridia käsittävän toisen liuoksen pH-arvon säätämisen.The process according to any one of claims 1 to 9, wherein the method comprises adjusting the pH of the separated and / or recovered calcium chloride solution and / or the second calcium chloride solution. 11. Jonkin patenttivaatimuksista 1-10 mukainen menetelmä, jossa menetelmä käsittää kalsiumkloridia käsittävän liuoksen ja/tai kalsiumkloridia käsittävän toisen liuoksen konsentraation säätämisen.The method of any one of claims 1 to 10, wherein the method comprises adjusting the concentration of the calcium chloride solution and / or the second calcium chloride solution. 12. Jonkin patenttivaatimuksista 1-11 mukainen menetelmä, jossa menetelmä käsittää kalsiumkloridia käsittävän liuoksen ja/tai kalsiumkloridia käsittävän toisen liuoksen konsentroimisen.The process according to any one of claims 1 to 11, wherein the method comprises concentrating a solution comprising calcium chloride and / or another solution comprising calcium chloride. 13. Jonkin patenttivaatimuksista 1-12 mukainen menetelmä, jossa menetelmä käsittää kalsiumklo-ridin kiteyttämisen, kuivaamisen ja/tai hiutaloimisen.The process according to any one of claims 1 to 12, wherein the process comprises crystallization, drying and / or flocculation of calcium chloride. 14. Jonkin patenttivaatimuksista 1-13 mukainen menetelmä, jossa menetelmä käsittää hiilidioksidin puhdistamisen, kompressoimisen ja/tai nesteyttä-misen.The process according to any one of claims 1 to 13, wherein the process comprises purifying, compressing and / or liquefying carbon dioxide. 15. Järjestelmä kemiallisen massanvalmistus-prosessin kemiallisesta talteenottoprosessista saatavissa olevan kalsiumpitoisen kiinteän jätteen käsittelemiseksi, jossa järjestelmä käsittää laitteen (1) kalsiumpitoisen kiinteän jätteen sekoittamiseksi suolahapon kanssa, niin että saadaan hiilidioksidia ja kalsiumkloridia käsittävä liuos; erotuslaitteen (2) kalsiumkloridia käsittävän liuoksen erottamiseksi kiinteästä aineesta, joka on suspensoitunut kalsiumkloridia käsittävään liuokseen; laitteen (3) erotetun kiinteän aineen sekoittamiseksi suolahapon kanssa, niin että saadaan hiilidioksidia ja kalsiumkloridia käsittävä toinen liuos; ja erotuslaitteen (4) kalsiumkloridia käsittävän toisen liuoksen erottamiseksi kiinteästä aineesta, joka on suspensoitunut kalsiumkloridia käsittävään toiseen liuokseen.A system for treating calcium-containing solid waste from a chemical recovery process of a chemical pulping process, the system comprising: (1) mixing calcium-containing solid waste with hydrochloric acid to obtain a solution comprising carbon dioxide and calcium chloride; a separator (2) for separating the calcium chloride-containing solution from a solid suspended in the calcium chloride-containing solution; a device (3) for mixing the separated solid with hydrochloric acid to form a second solution comprising carbon dioxide and calcium chloride; and a separator (4) for separating the second calcium chloride solution from the solid suspended in the second calcium chloride solution. 16. Patenttivaatimuksen 15 mukainen järjestelmä, jossa järjestelmä käsittää laitteen (5) hiilidioksidin ottamiseksi talteen.The system of claim 15, wherein the system comprises a device (5) for capturing carbon dioxide. 17. Patenttivaatimuksen 15 tai 16 mukainen järjestelmä, jossa järjestelmä käsittää kaustisointi-järjestelmän ja/tai erotuslaitteen viherlipeäsakan erottamiseksi.The system according to claim 15 or 16, wherein the system comprises a causticizing system and / or a separating device for separating the green liquor precipitate.
FI20145851A 2014-09-30 2014-09-30 Process and system for treating solid waste containing calcium FI126748B (en)

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