CN1048963C

CN1048963C - Lime softening water treatment method and its filtering equipment

Info

Publication number: CN1048963C
Application number: CN 94108062
Authority: CN
Inventors: 杨金旺
Original assignee: ELECTRIC POWER PLANNING AND DE
Priority date: 1994-08-08
Filing date: 1994-08-08
Publication date: 2000-02-02
Anticipated expiration: 2014-08-08
Also published as: CN1106364A

Abstract

The present invention discloses a method and a device for softening lime in water, wherein the device can be used for removing impurities in reaction liquid and different kinds of liquid in the process of reaction crystallization; a shell is in a tube structure that the upper part of the shell is bigger, the lower part of the shell is smaller, and diameter lengths at the middle part of the shell change gradually; a water inlet is arranged at the lower part of the device, and a water outlet is arranged at the upper part of the device; a perforated plate is arranged in a cavity at the upper part of the shell, and filtering material is arranged under the perforated plate. The device has the characteristics of strong capability for dirt capture, small volume and high flow velocity in operation, and the deep filtration of water is realized. A filtering procedure in the technology is accomplished by a filter which can realize deep filtration. The technology has the characteristics of simple system, small land occupation, low construction cost and good water quality.

Description

Lime softening treatment method for water and filtering equipment thereof

The invention discloses a lime softening treatment method of water and a filtering device thereof, belonging to the field of softening treatment of water, being applicable to the supplementary water treatment and urban water supply engineering of large-scale circulating cooling water systems in the departments of electric power, chemical industry, petroleum, metallurgy and the like.

The lime softening treatment of water is a more method adopted in the field of softening treatment of water at home and abroad, a new method for treating water by lime is proposed in recent years, the flow is shown as figure 1, and the lime softening treatment method mainly comprises the following steps: (1.) water is added into the rapid reactor 1 to be mixed with lime cream to carry out softening reaction, calcium carbonate generated by the reaction is crystallized on crystal nuclei, so that most of the calcium carbonate as a reaction product is trapped in the reactor 1, wherein the crystal nuclei are added into the rapid reactor 1 through an external crystal nucleus preparation and injection system H; (2.) Soft water containing a small amount of calcium carbonate particles flows out of the reactor 1, and is filtered by a gravity filter 6 and neutralized by a neutralizer 5 to obtain soft water, wherein in order to ensure the normal operation of the gravity filter G, a water backwashing and air scrubbing system X, a clean water tank Q and a complex wastewater recovery system (comprising a wastewater pool F, a cleaning water tank S, a sedimentation tank 11 and a dehydrator 12 and (3.) a reaction product calcium carbonate intercepted in the reactor 1 is periodically discharged from the reactor 1 and forms a calcined lime after passing through a calcining device 7, and (4.) hot calcined lime generated after calcination is cooled and is sent into a calcined lime storage device 9, and part of the calcined lime is digested to be milk and a metering device 10 and is added into the reactor 1 as a reactant, in the water treatment process, the method basically has no wastewater and slag discharge, the operation condition is good, the calcined lime is recovered and is then calcined to high purity (the content of active calcium oxide is higher than 95%), high-activity (the digestion speed is less than 60 seconds) quicklime, besides self consumption, part of surplus quicklime can be sold for external use, but the problems of larger whole system and higher occupied area and construction cost exist; the filtering equipment in the method is a conventional gravity type filter or a pressure type filter (such as a quartz filter), the filtering materials of the filter are distributed in such a way that the grain size of the upper part is small, the grain size of the lower part is large, when the filter is operated, water flow enters from the upper part and flows out from the lower part, most suspended matters in the water flow are intercepted on the upper surface layer of the filtering materials by the filtering materials with small grain sizes on the upper part, the dirt intercepting capability is low, the equipment is large, the resistance is accelerated in the operation process, the flow speed is low, if the filter is the quartz filter, quartz sand grows and is caked in the long-term operation process: the above problems are existed in the Chinese patent No. CN88109009.3 entitled "lime treatment and slag discharge recycling process system and equipment for water".

The invention aims to provide a lime softening treatment method of water and filtering equipment thereof, and the method can ensure that the whole system is simple, the occupied area is small, the construction cost is low, the effluent quality is good, and the water quality is stable and reliable; the filter equipment can realize deep filtration of water and has the characteristics of strong dirt intercepting capability, small volume, slow resistance increase in the operation process and high operation flow rate.

The purpose of the invention is realized as follows: a process for lime softening of water comprising the steps of: (1.) adding water into a rapid reactor, mixing with lime milk to produce softening reaction, and crystallizing most of the generated calcium carbonate crystal grains on calcium carbonate small crystal nuclei and retaining the calcium carbonate crystal grains in the reactor, (2.) discharging soft water containing a small amount of calcium carbonate particles which are not retained from the reactor, and filtering and neutralizing the soft water to obtain soft water; (3.) the calcium carbonate trapped in the reactor is periodically discharged from the reactor and forms quicklime through a calcining device; (4.) part of calcined quicklime is digested to prepare milk, and is used as a reaction medicament to be sent back to the reactor; wherein: the filtration is completed by a filter capable of realizing deep filtration, small calcium carbonate grains generated by reaction in a rapid reactor are periodically used as a filter material to be sent into the filter, and after the filter is used for a period of time, the small calcium carbonate grains are returned to the rapid reactor; the newly generated calcium carbonate small grains in the reaction process are used as a new filter material to be sent to a filter.

The filtering equipment in the lime softening treatment method of water consists of a shell, a water inlet, a water outlet, a porous plate and a filter material, wherein: the water inlet is arranged at the lower part of the shell, the water outlet is arranged at the upper part of the shell, the porous plate is arranged in the containing cavity at the upper part of the shell, the filter material is arranged below the porous plate, and the shell is of a reducing cylinder structure with a large upper part, a small lower part and a gradual middlepart;

a water distributor is arranged at the progressive body in the middle of the shell; the shell is provided with a filter material inlet and a filter material outlet.

The invention has the advantages that: because the novel filter is used as the filtering unit of the invention, the huge gravity type filter in the original method is replaced, a water backwashing and air wiping system and a clear water tank are saved, a wastewater recovery system is greatly simplified, a wastewater pond and a cleaning water tank are removed, and filter materials and intercepted larger calcium carbonate particles in the filter are taken as crystal nuclei and are periodically sent back to the reactor, thus a crystal nucleus preparation and injection system is saved, therefore, the method of the invention is simple and convenient to operate; compared with the prior method, the method has the following advantages:

compared with the main economic indexes of the prior art, the invention has the table items that 3500t/h 3500t/h of the treatment water of the invention is 3300 ten thousand yuan for construction cost of a hot gas system, 2950 ten thousand yuan for reducing 10 percent of the occupied area, 1.1 hectare, 0.88 hectare, 20 percent of the annual operating cost is reduced, 156.8 ten thousand yuan for reducing 130.0 ten thousand yuan for reducing 17 percent of the wastewater discharge amount, 250t/h 50t/h of the recovery water amount of the wastewater, 250t/h 50t/h, and no wastewater discharge water quality suspended substance, 0-5 ppm of granular or powdery carbon suspended substance, 0-5 ppm of granular or powdery water suspended substance

The calcium carbonate can be recycled, has the alkalinity of about 0.6epm and about 0.6epm, is sold outside and is granular

It can also be used by oneself. 90% to 95% of the granular calcium carbonate

Recovery rate

Because the filter adopts a reducing cylinder structure with a large upper part and a small lower part and a gradual middle part, when water enters and exits from the lower part, the filter material is washed, a fixed bed with a small particle size and a large particle size filter material below is formed on the upper part of the equipment, suspended matters with larger particle size in water flow are firstly intercepted by a large particle size filter layer on the lower part of the fixed bed, and suspended matters with small particle size are intercepted by a small particle size filter layer contacted with the lower part of the fixed bed, so that the whole filter layer has the dirt intercepting capability, the same kind of filter materials with different particle sizes are realized, and the function of deep filtration can be completed; the running resistance rises slowly along with the increase of the dirt in the filter layer, and the running flow rate is high; in addition, the active calcium carbonate filter material in the filter also has stronger adsorption capacity, can adsorb suspended particles in water flow and supersaturated parts of calcium carbonate in the water flow, and ensures that the effluent quality is good; the filter material is periodically replaced by the filter material transfer device, so that the reasonability of the particle size distribution of the filter material, high activity, stable material quantity, reliable equipment operation, stable effluent quality and high recovery rate of granular calcium carbonate are ensured; compared with the prior gravity filter, the gravity filter has the following characteristics:

main data comparison table items of two filters are gravity type filters, the pH value of the filter is 10.010.0 alkalinity (epm) 1.11.1 calcium carbonate supersaturated concentration (epm) is 0-0.050 suspended matter (ppm) 0-50-5 backwashing water consumption (backwashing water quantity/soft water quantity) 4-8%, the operation flow speed (m/h) is 6-830, and whether filter materials are agglomerated or not are not agglomerated

In addition, in the process of the method, one rapid reactor is provided with one filter material conveyor and a plurality of filter units. The transportation, operation, rinsing and filter material return of the materials to the reactor are all controlled by a timing program without manual operation, so that the operation is simple and the operation is reliable.

FIG. 1 is a schematic flow diagram of a prior process;

FIG. 2 is a schematic flow diagram of the process of the present invention;

FIG. 3 is a schematic diagram of the connection relationship of the filter units in the process flow of the present invention;

FIG. 4 is a schematic view of a filter construction according to the present invention;

FIG. 5 is a schematic view of the filter operating conditions of the present invention;

the invention is discussed in further detail below with reference to the accompanying drawings:

example 1:

the connection relation of a water lime softening treatment method and equipment used in the method is shown in figure 2, and comprises a rapid reactor 1, a filtering unit 4, a neutralizer 5, a slag pool 6, a calcining device 7, a flue gas recovery device 8, a quick lime storage device 9, a slaked milk making and metering device 10, a sedimentation pool 11 and a dehydrator 12;

the method comprises the following steps of:

taking normal temperature water with temporary calcium hardness more than 3.0epm as the water to be treated as an example;

(1.) the above water is added into a fast reactor 1, mixed with 1% -5% lime cream (5% in this example), and controlled at PH about 10, double decomposition reaction occurs:

the reaction product calcium carbonate is crystallized on small calcium carbonate crystal nuclei in the rapid reactor 1 and is trapped in the rapid reactor 1; larger suspended particles intercepted by the filter material in the filter unit 4 regularly return to the reactor 1 along with the filter material in the filter and are used as crystal nuclei;

(2.) the water flowing out of the fast reactor 1 is filtered by a filtering unit 4 (pH is about 10) and neutralized by a neutralizer 5 to obtain soft water; a small amount of calcium carbonate particles which are not intercepted in the rapid reactor 1 enter the filtering unit 4 along with water flow, and then are filtered and removed, and the effluent quality of the whole system is as follows: alkalinity: 0.0epm, 0-5 ppm of suspended matter, and supersaturated calcium carbonate: 0, pH is 7.5-8.5; wherein, rinsing water discharged from the filtering unit 4 and calcium carbonate particles carried in the water are sent into a sedimentation tank 11, and are dehydrated by a dehydrator 12 to obtain calcium carbonate powder for external sale;

(3.) the crystal nucleus in the rapid reactor 1 grows up along with the continuous crystallization of the reaction product, and the crystal nucleus is periodically discharged into a slag pool 6 from the reactor 1 according to the operation working condition (for example: when the grain diameter of the crystal nucleus is 2 mm), drained and then sent into a calcining device 7 to be calcined into quicklime; flue gas generated in the calcining process is sent into a flue gas recovery device 8 to obtain liquid carbon dioxide for export sales;

(4.) the hot quicklime generated after calcination is cooled and then sent into a quicklime storage device 9, and part of the hot quicklime is sent into a slaking and milk-making and metering device 10, and the slaking and milk-making is prepared into 1-5% of lime milk, and then the lime milk is sent back into the reactor 1 to participate in softening double decomposition reaction to form a cycle; the rest of the quicklime can be sold externally;

in the process, the soft water recovered in the slag tank 6 and the sedimentation tank 11 is sent to the filtering unit 4.

The key point of the invention is that the change of the filtering method in the step (2) and the corresponding system change brought by the change are the same as the other parts which are not involved in the process in the prior technical proposal; the following is a further detailed discussion of the gist of the present invention:

as shown in fig. 3, the rapid reactor 1 is provided with a water inlet 101, a water outlet 102, a lime milk inlet pipe 104, a filter material returning pipe 106, a slag discharging pipe 103, and a filter material output pipe 105, in order to ensure that the particle sizes of the output calcium carbonate filter material are different and are all within 0.2-1.0 mm, multiple paths of filter material output pipes can be arranged at different height positions of the reactor, and in this embodiment, two paths are arranged to meet the distribution of the particle sizes in the filter;

in the invention, one rapid reactor is provided with one filter material transfer device 2 and a plurality of filters 3, and five filters 3 are set in the embodiment;

wherein, the filter material converter 2 is provided with a filter material input port 202, a water discharge port 201, a filter material output port 204 and a pressure water inlet 203;

the filter 3 is composed of a shell 305, a water inlet 304, a water outlet 301, a porous plate 306, a filter material 307, a water distributor 308, a filter material inlet 302 and a filter material outlet 303, wherein the water inlet 304 is arranged at the lower part of the shell 305, the water outlet 301 is arranged at the upper part of the shell 305, the porous plate 306 is arranged in an accommodating cavity at the upper part of the shell 305, the filter material 307 is arranged below the porous plate 306, the filter material inlet 302 is arranged at the upper part of the shell 305, the filter material outlet 303 is arranged at the lower part of the shell 305, the shell 305 is of a reducing cylinder structure with a large upper part, a small lower part and a gradual middle part, and the diameter ratio of the large diameter to the small diameter; in this embodiment, the major diameter is 2.2 meters, the minor diameter is 0.7 meters, the height of the upper cylinder body can be arbitrarily selected according to the thickness of the required filter layer, 1.6 meters is selected in this embodiment, the height of the lower cylinder body is selected according to the number of the filter materials required by the thickness of the finished bed, 2 meters is selected in this embodiment, as shown in fig. 4.

The water inlet 101 of the rapid reactor 1 is externally connected with water to be treated; the water outlet 102 is connected with the water inlet 304 of the filter 3; the lime milk inlet pipe 104 is connected with the device 10 for preparing and metering the slaked milk;the filter material return pipe 106 is connected with a filter material outlet 303 of the filter 3; the slag discharge pipe 103 is connected with the slag pool 6; the filter material output pipe 105 is connected with a filter material input port 202 on the filter material transfer device 2;

the filter material outlet 204 on the filter material transferrer 2 is connected with the filter material inlet 302 on the filter 3, and the water outlet 201 is connected with the sedimentation tank 11; the pressure water inlet 203 is connected with a booster water pump P;

a water outlet 301 at the upper part of the filter 3 is connected with the neutralizer 5, and the output water is soft water;

the operation state of the system has the following two types:

during the first operation, a certain amount of slaked lime powder with the purity of 80% needs to be purchased externally and used as crystal nuclei in the rapid reactor 1 and filter material in the filter 3 for cultivation (for example, calcium carbonate with the purity of more than 96% is purchased externally, and the slaking agent can also be prepared mechanically), and when the slaking agent 1 discharges slag to a certain amount, namely: when calcined quicklime can meet the requirements of the process, the whole process enters a normal operation state.

During operation, four filters (respectively represented by A, B, C, D) should be operated (for example, five filters are used in the embodiment), one filter (represented by E) is in a standby state, and the filter material transfer device is in a full state; water enters the rapid reactor 1 from the water inlet 101, after softening reaction, flows out from the water outlet 102, enters each filter 3 through the water inlet 304, filter materials are washed up at a lower flow rate, a fixed bed which is large in upper part and small in lower part and canbe mixed with a certain thickness is formed at a position close to the porous plate 306, other parts in the filter 3 are suspension layers with different concentrations, water flow enters the filter layer from a large-particle-diameter filter material, large suspended matters are firstly intercepted by the large-particle-diameter filter material layer, small suspended matters are intercepted by a small-particle-diameter filter material layer which is contacted with the filter layer later, calcium carbonate supersaturation parts in the water flow are removed by the suspension bed and active crystal grains in the fixed bed after passing through the filter 3, meanwhile, the filter material has stronger adsorption force on the calcium carbonate particles in the water flow, small particles in the water flow are adsorbed by the filter material, and are partially fixed into one part of the crystal grains, at the moment, the water flows into, soft water is discharged after neutralization;

when the filter A operates for one period (or a plurality of periods), the filter material needs to be rinsed (or thoroughly backwashed), aiming at removing magnesium hydroxide, tiny calcium carbonate precipitates and other impurities carried in water generated in the double decomposition reaction process so as to ensure the high purity of calcium carbonate grains recovered by the rapid reactor 1 and control the grain diameter of slag discharged by the rapid reactor 1; the larger calcium carbonate particles intercepted in the filter material and the filter material are returned to the rapid reactor together to be used as crystal nuclei. And (3) opening a water inlet valve 304E and a water outlet valve 305E of the E-th stage to classify the filter materials, so that the filter materials with small particle sizes are arranged on the upper layer and the filter materials with large particle sizes are arranged on the lower layer as far as possible, and the aim of deep filtration is favorably fulfilled. After a certain time (e.g. three minutes), closing the drain valve 305E, and simultaneously opening the drain valve 301E, and putting the E filter into normal operation; closing the water outlet valve 301A by the A filter, splitting, simultaneously opening the drain valves 305A and 401, rinsing the filter material, closing the water inlet valve 304A and the drain valves 305A and 401 at a certain time (for example, five minutes), and finishing rinsing;

replacing the filter material of the filter A (if the filter material is thoroughly backwashed, the filter material can be replaced once after a plurality of cycles), opening a filter material discharge valve 303A and a return filter material valve 106F of the rapid reactor 1, starting a filter material delivery pump P, opening a pressure water valve 306A, starting the filter material discharge of the filter A, and after the discharge is finished, closing the filter material discharge valve 303A and the return filter material valve 106F and the pressure water valve 306A of the rapid reactor 1; opening a filter material inlet valve 302A and a drain valve 305A of the filter A, a discharge valve 204F and a water inlet valve 203F of the filter material transfer device 2, conveying the filter material in the filter material transfer device into the filter by using pressure water, closing all valves and a filter material conveying pump P of the filter A and the filter material transfer device 2 after the filter material is transferred, and keeping the filter A in a standby state;

the filter material converter is filled with filter material; opening a filter material delivery valve 105F, a drain valve 201F and a drain valve 401 of the filter material transfer device between the filter material transfer device 2 and the rapid reactor 1, closing the filter material delivery valve 105F after the filter material transfer device 2 is filled with the filter material, opening a filter material delivery pump P and a water inlet valve 205F of the filter material transfer device, timing (for example, after 1 minute), closing the drain valve 201F, the water inlet valve 205F, the drain valve 401 and the filter material delivery pump P of the filter material transfer device after the filter material remained in the pipeline is washed away, and at the moment, keeping the filter material transfer device 2 in a full state;

when the filter B runs for one period (or a plurality of periods) and the filter material needs to be rinsed, the steps of splitting the filter B, delivering the filter material A, replacing the filter material B, filling the filter material by the filter material transfer device 2 and the like are performed according to the steps, and the like, so that circulation is performed.

The valve switches of the steps can be controlled by computer programming.

The inventive content is not limited to the embodiments described.

Claims

1. A process for lime softening of water comprising the steps of: 1. adding water into a rapid reactor (1) to be mixed with lime milk to generate softening reaction, and intercepting most of generated calcium carbonate grains in the rapid reactor (1), 2. soft water containing a small amount of calcium carbonate particles which are not intercepted flows out of the rapid reactor (1), and obtaining finished water after filtration and neutralization; 3. the reaction product calcium carbonate trapped in the fast reactor (1) is periodically discharged from the fast reactor (1), forms quicklime through a calcining device (7), 4, after the hot quicklime generated after calcining is cooled, part of the quicklime is digested to prepare milk, and is returned to the fast reactor (1) as a reaction medicament, and the method is characterized in that: the calcium carbonate small crystal grains crystallized by reaction in the rapid reactor (1) are periodically taken as a filter material and sent into the filter (3), the filter material is used for a period of time and then directly returned to the rapid reactor (1) as crystal nuclei, and the newly generated calcium carbonate small crystal grains in the reaction and crystallization process are also taken as a new filter material and sent into the filter (3).

2. A process for the lime softening of water according to claim 1, characterized in that: during filtering, water enters from the lower part of the filter (3) with the upper part larger than the lower part and the middle part smaller than the lower part gradually, and flows out from the upper part.

3. The filtering apparatus in the lime softening treatment method of water as claimed in claim 1, which is composed of a housing (305), a water inlet (304), a water outlet (301), a porous plate (306), and a filtering material (307), characterized in that: the water inlet (304) is arranged at the lower part of the shell (305), the water outlet (301) is arranged at the upper part of the shell (305), the porous plate (306) is arranged in the containing cavity at the upper part of the shell (305), the filter material (307) is arranged below the porous plate (306), and the shell (305) is of a reducing cylinder structure with the upper part being large, the lower part being small and the middle part being gradual.

4. A filter apparatus in a process for lime softening of water according to claim 3, characterized in that: a water distributor (308) is arranged at the progressive body in the middle of the shell (305).

5. A filter apparatus in a process for lime softening of water according to claim 3 or 4, characterized in that: the shell (305) is provided with a filter material inlet (302) and a filter material outlet (303).

6. A filter apparatus in a process for lime softening of water according to claim 3 or 4, characterized in that: the filter material (307) is small grains of calcium carbonate that are crystallized by reaction in a rapid reactor.

7. A filter apparatus in a process for the lime softening of water according to claim 5, characterized in that: the filter material (307) is small grains of calcium carbonate that are crystallized by reaction in a rapid reactor.