JPS60206489A - Method and apparatus for post-treatment of prepared fresh water - Google Patents

Abstract

PURPOSE:To obtain drinking water having good quality, by guiding a part of prepared fresh water to the side of a limestone decomposition furnace to mix the same with formed quick lime and, thereafter, allowing the resulting mixing to absorb carbon dioxide while mixing the treated water with high purity carbon dioxide from the decomposition furnace and the remaining formed fresh water. CONSTITUTION:An externally heated limestone decomposition furnace 2 is provided in close vicinity to the installation place of the evaporation apparatus 1 of a fresh water making apparatus, for example, a seawater desalting apparatus and distilled water being fresh water formed from an evaporation 3 is introduced into a calcium dissolving apparatus 5 through a pipe 4, because contains only several ppm of TDS and unsuitable for drinking water, to impart hardness. That is, carbon dioxide generated by the decomposition of limestone in the heated decomposition tower 2' of the limestone decomposition furnace 2 keeps high purity and enters the calcium dissolving apparatus 5 to be dissolved in fresh water and CaCO3, H2O and CO2 are reacted in the dissolving apparatus 5 to form Ca(HCO3)2 in a dissolved state and hardness is imparted to fresh water.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a post-treatment method and device equipped with an ultra-small limestone decomposition furnace for converting produced fresh water obtained in a desalination device into a water quality suitable for water flow. be.

Even if some of the lime in limestone contains dolomite (dolomite), which is replaced by magnesia, the reaction will be completely the same, so in this invention, some explanations will be omitted, but all parts indicated by Ca This includes the case where Ca is 10Mq.

Since the fresh water obtained by the desalination equipment contains almost no mineral components, it corrodes the piping materials of the subsequent water supply system and has a poor taste as drinking water.

In order to compensate for these shortcomings, a method has been adopted to make manufactured water by adding calcium carbonate or slaked lime and carbon dioxide gas to fresh water.Generally, a container filled with limestone, a so-called limestone filter, is installed. Fresh water that has absorbed carbon dioxide gas passes through it, and calcium bicarbonate is produced through the following reaction, increasing hardness.

CaCO3+ ) 120 + CO2 −+Ca(To1co,) 2 − ... (1) This limestone filter usually uses easily available and inexpensive 2
Although limestone with a particle size of ~20mm is used, it is often of low purity and contains impurities, has a slow dissolution rate, and even if hardness is imparted, the water quality may be poor, so this limestone filter is The amount of fresh water processed is low compared to the capacity.
Therefore, large-scale salt water desalination equipment must be equipped with dozens of such filters, which increases equipment costs and requires limestone to be added to each filter, making this replenishment work, along with the work of discharging undissolved slime, quite complicated. Met.

On the other hand, carbon dioxide gas can sometimes be obtained by decomposing and extracting bicarbonate components in seawater in desalination equipment, so it would be reasonable to use this method, but in this case, ammonia, oil,
There is a risk of containing impurities such as bromine, and when hydrazine is used as an oxygen scavenger for the boiler of the steam for the extraction ejector.

In this case, there is a risk that hydrazine or the like may be mixed into the carbon dioxide gas being extracted, which is a problem.

In addition, carbon dioxide gas can be obtained through a process in which carbon dioxide gas produced by burning oil or gas is recovered using a solvent such as ethanolamine, or purchased liquefied carbon dioxide gas can be used; The system is of the same type as a large-scale system, making it complicated and requiring more power for pumps, etc., as well as requiring a large number of equipment and increasing construction costs, which also poses health problems. The latter is impractical as it causes a rise in price (running costs). In other words, in this case, the former would be an unreasonable scale-down for the requirement of about number + N]n''/H (CO2 etc.), and the latter would result in slightly too much consumption and the fear of running out of supply. It is.

As mentioned above, the required amount of carbon dioxide gas is several tens of N m'/l.
-1 (as CO2), and as limestone
The handling time is only a small number of 00h/h, and the small diameter limestone corresponding to this concavity is continuously processed, and the decomposition time is orders of magnitude shorter than industrial scale limestone with a diameter of several tens of mm or more. Therefore, the retention amount is small, making it suitable for heating inside a pipe such as a ceramic pipe described later.The concept is completely different from that of a conventional lime furnace, so the present invention is a newly developed ultra-small limestone decomposition method. Combining the furnace with a desalination unit organically to produce a higher purity slaked lime solution or milk of lime, even with slightly lower grade limestone, and then utilizing lower purity IAM gas. First, a slurry of fine particles of calcium carbonate is produced, and then the generated carbon dioxide gas is reacted with the fine particles of tunorsium carbonate in fresh water to efficiently produce calcium hydrogen carbonate. That is, before the above reaction formula (1), the following reaction Ca (OH) 2 + CO 2 − + CaC0z + H 20 −−−−−−−−−−−−−−−−−−−−−−−− (2) is performed to capture dilute carbon dioxide gas and to avoid generating C calcium carbonate. This is a method of dissolving calcium bicarbonate in fresh water by reacting the produced calcium carbonate with fresh water and carbon dioxide gas according to equation (1), which is economical, allows for smaller and more continuous equipment, and passes water quality standards. This was done for the purpose of obtaining stable drinking water. The present invention will now be described with reference to the accompanying drawings.

An externally heated limestone decomposition furnace (2) is installed close to the installation location of the desalination equipment, for example, the seawater desalination evaporation equipment (1), and the distilled water, which is fresh water produced from the evaporator (3), is
It contains only a few ppm L of DS and is not suitable for drinking as it is, so in order to reform it, it is introduced into the calcium dissolving device (5), which will be described in detail later, through the pipe (4), and the hardness is adjusted as described later. Gives FI4.

On the other hand, the limestone decomposition furnace (2) shown in an enlarged manner is of an external heating type, and for example, a thermal decomposition tower (2- ) can use ultra-small tubes with diameters of several meters or meters, and limestone of several mm in diameter is charged into the furnace from the top popper (6) through the double charging valve (7). (8) is heated to 900°C or higher through the furnace wall (10) by a heater (9) such as a burner using petroleum as fuel in the thermal decomposition tower (2'), and is converted into quicklime and carbon dioxide gas. The quicklime decomposes into a cooling zone at the bottom of the furnace (
11), the air from the blower (12) is indirectly cooled by the cooler (13) through which it flows, and then passes through the pipe (15) with the discharge valve (14) to the lower quicklime digester (16). to fall. It goes without saying that a device other than a burner can be used as the heater (9), and it is considered advantageous to use electricity as the heat source, especially when the heater is small. The charging valve (7) and the discharge valve (14) each have a sealing mechanism (
Of course, measures such as installing a sealing gas in the pipe (15) to prevent air from entering (not shown) and sealing the pipe (15) to prevent the generated carbon dioxide from leaking to the outside are of course taken. Water vapor, which is condensed in the subsequent step (2), is particularly preferred for use in sealing or sweeping without lowering the purity of carbon dioxide gas. The material for the furnace wall may be a heat-resistant metal such as Inconel, and a ceramic such as SiC or Al1.
0J, other heat-resistant materials such as pyroceram and cermet are used.

The freshwater before entering the calcium dissolving device (5) of the desalination device (1) is charged into the quicklime digester (16) via a branch pipe (17), and slaked lime solution or milk of lime is produced in the device. Impurities are turned into silt by the thickener (18) installed inside and discharged from the lower part (19), and the purified products are discharged through the pipe (19).
20) and is sent to the first stage carbon dioxide absorber (21). In the quicklime digester (16), when the purity of the charged quicklime is high, a long pipe can be used instead of a container.

In the first stage carbon dioxide absorption tower (21), combustion exhaust gas from the burner passes through the outer periphery of the thermal decomposition tower (2'), passes through the duct (22), and passes through the pipe (24) in the heat exchanger (23). After being cooled by heat exchange with the air, it is ejected to the bottom (26) through a pipe (25), and the carbon dioxide gas in the exhaust gas reacts with the slaked lime solution or milk of lime in the vessel to produce CaC01. This cacOi has a small particle size and is convenient for subsequent transport and reaction. Excess exhaust gas is removed from the upper pipe (27)
It is released more into the atmosphere. In this way, low-purity carbon dioxide gas can be used to generate CaCO3, which is economical.

A circulating water guide cylinder (28) is provided inside the first stage carbon dioxide absorber (21) to allow the reaction to occur smoothly.

Since the CaCO3 generated here has a small particle size, it becomes a slurry and flows through the pump (29) and the pipe (30), and the CaCO3 reaches the calcium dissolving device (5) at a concentration of, for example, about 0.5%. It passes through the lever and mixes with the overlying fresh water. In addition to the above-mentioned combustion exhaust gas, the first stage carbon dioxide absorber (21) contains some limestone decomposition gas, carbon dioxide obtained from other sources, such as boiler exhaust gas, bleed gas from a seawater desalination equipment, or in the air. Low-purity carbon dioxide gas or the like may be used alone or in combination.

In the above explanation, a part of the produced fresh water is transferred to the quicklime digester (16).
However, in some cases, the pipe (, 4) may be omitted and the entire amount of generated fresh water may be introduced. In this case as well, if the limestone is of high purity and contains almost no impurities, the container (16) may be omitted and a long pipe may be used instead.

The carbon dioxide gas generated by the decomposition of limestone inside the thermal decomposition tower (2') of the limestone decomposition furnace (2) maintains high purity.
1), enters the calcium dissolving device (5) and is dissolved in fresh water, and in the dissolving device (5) CaCO3, “H20, CO
2 reacts, Ca (HCo,) is dissolved and produced, giving hardness to fresh water. At this time, as mentioned above, CaCO5 has a small particle size, so the reaction rate is high, and it cannot be used as a filter like a conventional limestone filter. Does not require large-scale equipment.

The hardness required for the treated fresh water taken out from the tube (32) is about several tens of ppm in terms of hydrogen carbonate ions,
30) The production of this amount of hydrogen carbonate ions from about 5% Ca CO3 is possible due to the fact that the carbon dioxide gas used is highly pure and easily soluble, and the reaction time is shortened. The lucium melting device (5) can be made small and the internal m
The structure is extremely simple; all that is required is that it can be sufficiently mixed and dissolved, and the carbon dioxide absorption part is a simple base model or a pipe of an appropriate length as shown in the figure to carry out the reaction.
33) is sufficient.

When a portion of the produced quicklime can be used for purposes other than the main post-treatment in the vicinity, a portion of the high-purity carbon dioxide gas generated by heating the limestone is used instead of the low-purity carbon dioxide gas mentioned above. However, the amount of energy required to heat the limestone to produce carbon dioxide gas in this area would consume too much energy, making it impractical unless a small amount of quicklime is always needed at that location.

The present invention installs a desalination device and an externally heated limestone decomposition furnace in the vicinity, organically communicates with each other, and directs a part or all of the produced fresh water to the quicklime produced in the limestone decomposition furnace to turn it into lime milk or slaked lime solution. If there are impurities, they are first separated by sedimentation, and then low-purity carbon dioxide such as externally heated limestone decomposition furnace combustion exhaust gas, some limestone decomposition gas, and carbon dioxide obtained from other sources are absorbed singly or in combination. After that, the high-purity carbon dioxide gas generated in the furnace is further reacted to produce calcium hydrogen carbonate in fresh water, so low-purity carbon dioxide gas in the combustion exhaust gas can be used effectively without being disposed of.
In addition, unlike conventional limestone filters, the calcium dissolving device does not require intermittent and troublesome work such as filling and replenishing limestone, but can improve work efficiency because it is continuous. The condition of the furnace or r is the case where the amount of carbon dioxide gas from the decomposition furnace alone is insufficient depending on the type of fuel used in the heater (9), and the amount of permeated water is When Ca(
Due to the strong reactivity of OH)z, an absorption tower can be installed to capture several hundred ppm of carbon dioxide gas in the air, thereby making up for the shortage. Further, if there is sulfur in the fuel, the captured sulfur content as CaSO4 etc. can also be an effective source of calcium.

Furthermore, the addition of carbon dioxide gas reduces the particle size of Ca.
Since CO3 is generated, the reaction rate with high-purity carbon dioxide gas, which is easy to dissolve, in the subsequent calcium dissolving device increases. Incidentally, since the calcium carbonate fine particles of the present invention have a specific surface area several hundred to tens of thousands of times larger than that of a limestone filter made of limestone with a diameter of several millimeters, the melting device can be small and simple in shape, and the passage speed of fresh water can be reduced. It increases the C processing capacity that can be done by humans, and if there is some extra space in the piping length, it can be made smaller by using part of it, or new additional equipment can be omitted, and the purity can be improved. It is possible to operate even with inferior limestone as a raw material because it uses small particles, and weathered shells with sand mixed in can be considered as a target.On the other hand, even if the concentration of carbon dioxide gas is low, the produced CaCO3 can be converted to high-grade one.
Up to the reaction in Equation (2), carbon dioxide gas from a low Fl place, or even the atmosphere in extreme cases, can be used, and the carbon dioxide in Equation (1) can be self-sufficient, so each component can be is well balanced and there is no waste, and if there is a limestone quarry near the desalination plant, even if only low-grade limestone can be mined, it can be used effectively, which is particularly effective.

[Brief explanation of drawings]

The figure is a partially enlarged flowchart 1 in an embodiment of the present invention. (1)... Desalination equipment, (2)... External heating limestone decomposition furnace, (2')...
... thermal decomposition tower, (3) ... evaporator, (5) ... calcium dissolution device, (6) ...
... Small collar, (7) ... Double valve for charging, (9) ... Heater, (12) ... Blower, (13) )...Cooler, (14)...Discharge valve, (16)...Quicklime digester, (18)...Thickener,

Claims (7)

[Claims] (1) An externally heated limestone or limestone containing bitter material (hereinafter referred to as limestone) decomposition furnace is installed near the desalination equipment, and a part of the produced fresh water is led to the limestone decomposition furnace and mixed with the produced quicklime. This is made into lime milk or slaked lime solution, and this is made to absorb limestone decomposition furnace combustion exhaust gas, some limestone decomposition gas, and carbon dioxide gas obtained from other sources, either alone or in combination, and this and the limestone generated from the limestone decomposition furnace are combined. A method for post-processing produced fresh water, characterized by imparting hardness by mixing and absorbing pure carbon dioxide gas and remaining produced fresh water. (2) An external heated limestone decomposition/furnace is installed near the desalination equipment, and the produced fresh water is led to the limestone decomposition furnace side and mixed with the produced quicklime to form a slaked lime solution, which is then mixed with the limestone decomposition furnace combustion exhaust gas, Adding hardness to the produced fresh water by absorbing limestone decomposition gas and carbon dioxide gas obtained from other sources, either alone or in combination, and by mixing and absorbing high purity carbon dioxide gas generated from the limestone decomposition furnace. A method for post-treatment of produced fresh water, characterized by: (3) The desalination device and the calcium dissolution device through which the produced fresh water passes are externally heated limestone comprising a limestone hopper, a thermal decomposition tower having a charging valve and a discharge valve, a quicklime digester, and a first stage carbon dioxide absorber. A freshwater after-treatment device installed close to the decomposition furnace. (4) The produced fresh water after-treatment device according to claim 3, wherein the desalination device is an evaporator and the produced fresh water is distilled water. (5) The produced fresh water after-treatment device according to claim 3, wherein the desalination device is a reverse osmosis device, and the produced fresh water is permeated water. (6) The produced fresh water after-treatment device according to claim 3, wherein the calcium dissolving device is a basic type or a carbon dioxide absorbing portion consisting of long piping. (7) The produced freshwater after-treatment device according to claims 3, 4, 5, and 6, wherein the charging valve and the discharge valve have a sealing mechanism.