JP3933509B2 - Potassium chloride recovery method and recovery device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a potassium chloride recovery method and recovery apparatus. More specifically, the present invention relates to a potassium chloride recovery method and recovery device that recovers high-purity potassium chloride and enables recycling.
[0002]
[Prior art]
Conventionally, in order to remove low melting point compounds such as sodium chloride (NaCl), potassium chloride (KCl), heavy metal chloride, sodium sulfate, potassium sulfate, heavy metal sulfate, etc., a bypass is provided, and exhaust gas from a cement firing device is provided. A part is extracted. The extracted cement kiln exhaust gas is solid-gas separated by a cyclone and collects dust having a relatively large particle size including cement raw material components such as calcium, silica, alumina, and iron. The collected dust is returned to the cement kiln. Further, dust having a relatively small particle diameter is removed through a filter means such as a bag filter. This dust contains a low melting point compound. And exhaust gas is returned to a cement baking apparatus.
[0003]
Examples of such a low melting point compound include sodium chloride (NaCl), potassium chloride (KCl), heavy metal chloride, sodium sulfate, potassium sulfate, heavy metal sulfate, and the like. These low melting point compounds may be separated by appropriate separation means and recycled as valuable materials.
[0004]
Of the low-melting compounds, potassium chloride is highly utilized as an industrial salt if it can be separated alone. For example, use as a fertilizer is also conceivable.
However, when potassium chloride is separated, it is difficult to separate from sodium chloride by the conventional method, and in order to improve the purity, a burden is great in terms of process and cost. Therefore, an improvement in recovering potassium chloride with high purity has been desired.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a potassium chloride recovery method and recovery device that can efficiently recover potassium chloride from exhaust gas from a cement firing device with high purity. To do.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention relates to a method for recovering potassium chloride by extracting a part of exhaust gas from a cement baking apparatus and recovering potassium chloride. According to the quantity, a potassium source is introduced into the cement baking apparatus to improve the purity of recovered potassium chloride.
[0007]
Moreover, this invention is a recovery device of potassium chloride in another aspect, It uses with the said cement baking apparatus in the recovery apparatus of potassium chloride which extracts a part of waste gas from a cement baking apparatus, and collect | recovers potassium chloride. A monitoring means for monitoring the chlorine content of the material and a means for supplying a potassium source to the cement baking apparatus according to the chlorine content are provided to improve the purity of recovered potassium chloride. It is characterized by that.
[0008]
In this specification, “materials used in cement burning equipment” includes combustible waste such as limestone, clay, earthenware waste materials, cement materials such as soil, heavy oil used as fuel, pulverized coal, waste plastics, etc. Including things.
In the present specification, “recovery” has a meaning generally understood by those skilled in the art, and “separation only”, “removal only”, or “separated” or “removed” as valuable compounds. Including getting.
In the present specification, the “low melting point compound” includes sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, heavy metal chlorides and sulfates, and the like.
In the present specification, the “cement firing apparatus” refers to a system of the entire firing apparatus including a cement kiln such as a rotary kiln for cement firing and a cyclone, a calcining furnace (preheater), and peripheral devices such as a clinker cooler.
“A part of the extraction gas” means that, in a normal firing device, the main part is the firing process of cement, and since it is linked to peripheral equipment such as a calciner, it is usually in principle to extract all of it. This is because it cannot be obtained. However, it does not eliminate the case where “all” is extracted when possible or necessary.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a potassium chloride recovery method and apparatus according to the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram showing an outline of an embodiment of a cement baking apparatus for carrying out the potassium chloride recovery method and apparatus according to the present invention.
[0010]
The cement firing apparatus 100 according to this embodiment includes a rotary kiln 102, a calcining furnace 104, a suspension preheater 106, and a clinker cooler 108 as main components for cement firing.
[0011]
Here, the embodiment of the method and apparatus for recovering potassium chloride according to the present invention will be described by explaining the operation of the cement baking apparatus 100 including the embodiment of the apparatus for recovering potassium chloride according to the present invention. .
In the present embodiment, first, clay, limestone, and potassium compound from the clay hopper 110, the limestone hopper 112, and the potassium compound hopper 114 are respectively charged into the pulverizer 116.
[0012]
The input ratio of clay and limestone is adjusted according to the intended cement composition. In addition, it is not limited to this Embodiment, The waste material of earthenware and soil can also be used as a cement raw material.
One feature of the present invention is that a potassium compound is charged into a cement baking apparatus. This is because chlorine and potassium are combined in the firing process of the cement raw material to antagonize and prevent sodium chloride formation. This makes it possible to recover high-purity potassium chloride with little sodium chloride contamination when recovering potassium contained in the cement raw material as potassium chloride.
[0013]
In this embodiment, potassium carbonate is added as a potassium compound. The control of the input amount from the hopper 114 will be described later. In addition, examples of the potassium compound (potassium source) that can be added include potassium sulfate and potassium hydrogen carbonate. Two or more compounds can be used in combination. Moreover, it is not a pure compound but may be a potassium-containing material such as fertilizer and its waste product.
[0014]
The cement raw material pulverized by the pulverizer 116 is mixed by the mixer 118 and temporarily stored in the storage silo 120.
Then, according to the processing status of the cement baking apparatus 100, the cement raw material is input to the upper raw material input unit 122 of the suspension preheater 106.
The suspension preheater 106 preheats the cement raw material.
The cement raw material is calcined by the calcining furnace 104 after preheating. In the calcining furnace 104, the cement raw material is calcined by the burner 124.
[0015]
The calcined cement raw material reaches the rotary kiln 102. The rotary kiln 102 includes a burner 126. The burner 126 is fed with a main fuel such as heavy oil and pulverized coal and an auxiliary fuel such as waste plastic containing chlorine and burns to burn the cement raw material.
The cement clinker discharged from the rotary kiln 102 enters the clinker cooler 108 and is cooled by the cooling air 128. These are a series of firing steps for cement raw materials.
[0016]
In the present embodiment, the chlorine concentration, potassium concentration and sulfate sulfur (SO ₃ ) concentration in the cement raw material and the fuel are further monitored by fluorescent X-rays and the like, and the molar ratio of each is 1 ≦ (K-2SO ₃ ). The amount of potassium compound charged into the pulverizer 116 is determined so that /Cl≦1.2.
[0017]
Next, the process of recovering potassium chloride from the extracted exhaust gas will be described in the present embodiment.
First, the extracted exhaust gas is sent to the heating device 130. The extraction operation is performed using an extraction device such as an extraction probe (not shown). The extracted exhaust gas is usually in a temperature range of 400 to 700 ° C. In the heating device 130, this is heated to a temperature of 1100 to 1500 ° C.
[0018]
By heating in this way, the low melting point compound is transferred from the dust side mainly composed of a cement raw material component such as calcium to a vaporized gas component.
The exhaust gas is then sent to the cyclone 132. Here, solid-gas separation is performed, and the dust is returned to the firing step. Here, the low melting point compound is contained in the gas component. Accordingly, the returned dust contains almost no low melting point compound. Examples of the low melting point compound include potassium, sodium, and chlorides and sulfates of metals such as copper, zinc and lead. However, in the present embodiment, the amount of sodium chloride is sufficiently reduced.
[0019]
The extracted exhaust gas containing the low melting point compound is sent to the bag filter 134. Before this, cooling gas is fed in and cooled to a temperature of 120 to 600 ° C. Then, the low melting point compound is separated by the bag filter 134. The separated low melting point compound is recovered from the lower recovery port and sent to the heavy metal recovery device 136.
As the heavy metal recovery device 136, one generally used by those skilled in the art, such as a wet refining device, can be adopted. For example, the recovered dust-like low melting point compound is washed with water, and acid / alkali elution, sulfide precipitation, etc. are appropriately combined and separated as a metal refining raw material containing a zinc component, a copper component, and a lead component. Further, the filtrate and washing water after collecting the heavy metal are sent to the alkali salt collecting device 138.
[0020]
The alkali salt recovery device 138 can recover potassium chloride by various methods. For example, the filtrate and the washing water can be boiled to obtain a supersaturated state, and then cooled and precipitated.
Therefore, for example, potassium chloride that can be reused as a raw material for fertilizer and feed can be recovered.
Conventionally, mixing of sodium chloride has been a problem. However, as apparent from the present embodiment, since the potassium compound is used as a secondary material according to the chlorine content in the material, the purity of the recovered potassium chloride surely exceeds 90% by weight.
[0021]
The gas component of the extracted exhaust gas that has passed through the bag filter 134 is returned to the raw material charging unit 122 again. When the temperature of this gas is 350 ° C. or higher, it contributes to increasing the efficiency of the entire apparatus.
[0022]
The cement baking apparatus 100 includes a waste heat recovery boiler 140, collects waste heat of the exhaust gas, and then exhausts the exhaust gas from the chimney 144 via the bag filter 142.
[0023]
Other Embodiments Although the method and apparatus for recovering potassium chloride according to the present invention have been described with respect to the embodiments of FIG. 1, the present invention is not limited to these embodiments, and the present invention obvious to those skilled in the art. All modifications, changes and additions within the scope of the technical idea are included in the present invention.
[0024]
For example, although the cement kiln is a rotary kiln in the embodiment of FIG. 1, other types of kilns such as a moving bed such as a vertical kiln or a fluidized bed type kiln may be used. Moreover, even if it is a cement baking apparatus which is not equipped with a calcining furnace and / or a suspension preheater, this invention can be implemented.
Further, instead of heating with the heating device of FIG. 1, a combustible material may be put into the inlet hood and burned, and the gas temperature of the inlet hood may be raised to 1100 to 1500 for extraction.
Furthermore, the potassium compound may be charged from the raw material charging unit 122 as long as it is powder, instead of being directly charged into the pulverizer 116.
[0025]
【The invention's effect】
As is apparent from the above description, according to the present invention, there is provided a potassium chloride recovery method and recovery device that can efficiently recover potassium chloride from exhaust gas of a cement firing device with high purity.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram illustrating an outline of an embodiment of a cement baking apparatus including a potassium chloride recovery apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 Cement baking apparatus 102 Rotary kiln 104 Calcining furnace 106 Suspension preheater 108 Clinker cooler 110 Clay hopper 112 Limestone hopper 114 Potassium compound hopper 116 Crusher 118 Mixer 120 Storage silo 122 Raw material input part 124 Burner 126 Burner 130 Heating apparatus 132 Cyclone 134 Bug Filter 136 Heavy metal recovery unit 138 Alkali salt recovery unit 140 Waste heat recovery boiler 142 Bag filter 144 Chimney

Claims (2)

In the method of recovering potassium chloride by extracting a part of the exhaust gas from the cement baking apparatus and recovering potassium chloride, a potassium source is supplied to the cement baking apparatus according to the chlorine content of the material used in the cement baking apparatus. A method for recovering potassium chloride, characterized in that the purity of the potassium chloride that is introduced and recovered is improved. In a potassium chloride recovery device that extracts potassium chloride by extracting a part of exhaust gas from a cement firing device, monitoring means for monitoring the chlorine content of materials used in the cement firing device, and the chlorine content Accordingly, there is provided a means for supplying a potassium source to the cement firing apparatus, and the purity of the recovered potassium chloride is improved.

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