CN1263162A - Normal temperature sponge iron deoxidizing agent production method - Google Patents
Normal temperature sponge iron deoxidizing agent production method Download PDFInfo
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Abstract
The production method of sponge iron deaerating agent includes the following steps: the lump hematite, lignite and limestone are added into rotary kiln according to a certain proportion, and a specially-defined temp. is controlled to make reduction treatment under the condition of reduction atmosphere. The ratio of hematite and lignite added in the rotary kiln is carbon to iron 0.52-0.45, and the added quantity of limestone is 4-6% of hematite weight, and the lignite can be added into the rotary kiln by three portions of coal, coarse spraying coal and fine spraying coal, and continuously sprayed into kiln from kiln head or kiln tail. Said invented deaerating agent can be produced continuously, its microporous pore size is smaller, and its deaerating effect is good and service life is long.
Description
The invention relates to a method for producing an oxygen scavenger for removing dissolved oxygen in water in boiler feed water and circulating water systems in the water treatment technology. The method is mainly used for producing the sponge iron deoxidant of the filler type deaerator.
To reduce the corrosion of boilers and circulating water equipment, reducing the dissolved oxygen content in water is one of the most important means. The traditional deoxidization methods, such as thermal deoxidization, vacuum deoxidization, analytic deoxidization and the like, have the defects of large investment, high operation cost, complex operation and maintenance, poor reliability and the like.
The sponge iron deoxidant developed in recent years can remove dissolved oxygen in water at normal temperature, so that the content of the dissolved oxygen in the water can be reduced to be below 0.1mg/L, the operating cost in the deoxidization process is greatly reduced, and the sponge iron deoxidant can be installed at a low position, thereby solving the defects that some deoxidization methods need to be installed at a high position, the capital investment is large, and the energy consumption is large. The sponge iron deoxidant (ZL96120578.4) developed in recent years in China is sintered in a reverse smoke kiln which is an earth method for producing the sponge iron deoxidant and can be used for deoxidization in water, but the sponge iron deoxidant has the defects of high backwashing frequency, high labor intensity, short service life and the like in the deoxidization process due to the fact that the pore diameter of a porous product is large and continuous production is not realized, and the quality is difficult to ensure to be consistent, so that the popularization of the deoxidization method is restricted.
The invention aims to provide a method for producing a normal-temperature sponge iron deoxidant by using a reduction rotary kiln. The method for producing the sponge iron deoxidant is characterized in that blocky hematite, brown coal and a small amount of limestone are added into a rotary kiln according to a certain proportion and are reduced under the control of a specific temperature and a reducing atmosphere. The pore diameter ratio of the deoxidant micropores is small, continuous production can be realized, and the quality is ensured to be consistent. The deoxidant has good deoxidization effect, low backwashing frequency and long service life in the deoxidization process, so that the deoxidization method can be popularized in a large range.
The purpose of the invention is realized as follows:
the method for producing the sponge iron deoxidant is characterized in that blocky hematite, brown coal and a small amount of limestone are added into a rotary kiln according to a certain proportion and are reduced under the control of a specific temperature and a reducing atmosphere. The sponge iron deoxidant is prepared from hematite, lignite and a small amount of limestone. Wherein: the total iron content of the hematite is more than or equal to 66%, and the granularity of the hematite is 5-20 mm; the fixed carbon content of the coal is 45-55%, the ash content of the coal is less than 20%, and the softening temperature of the ash content is higher than 1200 ℃. The continuous adding speed of the hematite is 18-30.5 t/h.
The ratio of iron ore to coal fed into the kiln is such that the carbon-to-iron ratio (C/Fe) is 0.45 to 0.52 (i.e., the ratio of the carbon content of the coal fed into the kiln to the total iron content of the hematite fed into the kiln).
The limestone plays a role in desulfurization, the addition amount of the limestone is 4-6% of the total iron content of the hematite, the granularity of the limestone is 2-4 mm, and the limestone is continuously added at the tail (a feeding end) of a kiln together with the hematite and the added coal.
The lignite charged to the rotary kiln was divided into three parts (charged coal, coarse coal injection and fine coal injection):
(1) the first part is added coal which accounts for 52-65% of the total coal amount entering the kiln, the granularity of the first part is less than or equal to 50mm, and the first part is mixed with hematite and limestone by a kiln tail (a feeding end) and is continuously added into the kiln. The addition speed can be 4-12 t/h.
(2) The second part is coarse coal injection accounting for 23.3-32% of the total coal entering the kiln, the granularity of the coarse coal injection is 6-12.5 mm, and the coarse coal injection is continuously injected into the kiln through a kiln head (a discharge end). The addition rate can be 3-6.3 t/h.
(3) The third part is fine coal injection, which accounts for 11.7-16.2% of the total coal quantity in the kiln, wherein: the grain size is less than or equal to 6mm and accounts for 65 percent, the grain size is 6-12.5 mm and accounts for 35 percent, and the grain size is continuously sprayed into the kiln through a kiln head (a discharge end). The addition rate can be 1.5-3.5 t/h.
The invention uses a reduction rotary kiln, and the reduction temperature is controlled as follows: the temperature of the preheating section is 670-840 ℃, and the temperature of the reduction section is 840-1070 ℃. The temperature is low at the tail of the kiln and high at the head of the kiln.
The rotating speed of the rotary kiln is selected between 0.36-0.44 r/min according to different ore quantities continuously entering the kiln.
The pressure of the kiln head (discharge end) should be kept at micro-positive pressure (2-3 mmH)2O)。
The sponge iron deoxidant of the invention has the deoxidization principle that:
the sponge iron deoxidant contains high-activity iron, and the active iron and dissolved oxygen in water rapidly undergo an oxidation-reduction reaction under the normal temperature condition, and the reaction equation is as follows:
in order to make the dissolved oxygen in water and the active iron in the sponge iron rapidly undergo oxidation-reduction reaction and be widely used in industry, the sponge iron deoxidant is required to have:
(1) the content of metallic iron is high;
(2) and the specific surface area is large. However, the pore diameter of the sponge iron micropores is moderate, otherwise, Fe (OH) in the pores is easily caused3The aggregation of the precipitate is large, so that the precipitate can be applied to Fe (OH) on the surface of the sponge iron3The polymerization force of the precipitate is large, and the precipitate is not easy to wash away during backwashing, so that the surface of the sponge iron can not be contacted with dissolved oxygen in water any more, and the oxygen removal effect is reduced;
(3) the aluminum alloy has certain strength, and is not easy to grind in the using process so as to prevent the aluminum alloy from entering deoxygenated water.
As long as the above conditions are satisfied, the oxygen removing effect can be ensured. The sponge iron deoxidant produced by the method of the invention completely meets the requirements.
The raw materials for producing the sponge iron deoxidant are blocky hematite and brown coal which are added into a rotary kiln according to a certain proportion and are reduced under the control of a specific temperature and a reducing atmosphere. The reaction process is as follows:
and (4) screening, winnowing and magnetic separation system treatment are carried out on the reduced sponge iron deoxidant semi-finished product to obtain a sponge iron deoxidant finished product.
The sponge iron deoxidant is produced by using lump ore, the aperture of the micropores is several times smaller than that of the sponge iron produced by the soil method, and the density of the sponge iron deoxidant is 2.3-2.6 g/cm3The uniqueness of the deoxidant makes the backwashing frequency of the deoxidant greatly reduced, the surface regeneration effect is good, and the service life is prolonged. The oxygen scavenger is effective not only to soft water,and the effect of removing dissolved oxygen in industrial water is also ideal. The content of dissolved oxygen in the treated water can be lower than 0.02 mg/L. The deoxidant can be widely used for the anticorrosion treatment of boilers and circulating water facilities.
The reduction rotary kiln, the vibrating screen, the winnowing machine and the magnetic separator are all universal equipment.
The production process of the blocky sponge iron deoxidant is described in the following with the attached drawings:
FIG. 1 is a process flow chart of the production process of the blocky sponge iron deoxidant.
FIG. 2 is a schematic size view of a reduction rotary kiln used in the examples.
FIG. 3 is a graph showing the oxygen content of the sponge iron deoxidant in the feed water of a 20-ton boiler test (8 months and 10-30 days).
In the figure: 1-chimney, 2-kiln tail cloth bag dust remover, 3-waste heat boiler, 4-ore bin, 5-coal adding bin, 6-limestone bin, 7-coarse coal spraying bin, 8-fine coal spraying bin, 9-after combustion chamber, 10-rotary kiln, 11-kiln head hood, 12-cooling cylinder, 13-cooling cylinder discharge end, 14-buffer bin, 15-vibrating screen, 16, 17, 18, 19-magnetic separator, 20-kiln shell fan, 21-cooling water, 22, 23, 24-air separator, 25, 26, 27, 28-nonmagnetic substance, 29, 30, 31, 32-sponge iron deoxidant.
Firstly, according to the difference of the production quantity, the lump iron ore, the added coal and the limestone which are raw materials output from the ore bin 4, the added coal bin 5 and the limestone bin 6 are continuously added into the rotary kiln 10 from the kiln tail (the feeding end) according to a certain proportion and granularity. From the coarse coal injection 7And the injection coal (coarse coal and fine coal) output from the finecoal injection bin 8 is continuously injected into the rotary kiln 10 from the kiln head (discharge end) to perform the reduction reaction of the ore. The carbon-iron ratio (C/Fe) of the mixture fed into the kiln is 0.45-0.52. The reduction temperature in the kiln varies depending on the kind of ore, the particle size of the ore, and the amount of ore added. The temperature of the reduction section is generally controlled as follows: the high point temperature is 1070 ℃ and the low point temperature is 840 ℃. The temperature regulation in the kiln and the formation of the reducing atmosphere are realized by the air quantity sent by 10 kiln shell fans 20 arranged on the kiln shell. And the pressure of the kiln head (discharge end) is required to be kept at micro-positive pressure (2-3 mmH)2O)。
And cooling the reduced semi-finished sponge iron deoxidant to below 100 ℃ through a cooling cylinder 12, screening through a vibrating screen 15, winnowing through winnowing machines 22, 23 and 24, and magnetic separation through magnetic separators 16, 17, 18 and 19, and separating the sponge iron deoxidant from residual carbon and nonmagnetic substances 25, 26, 27 and 28 to obtain finished products, namely block normal-temperature sponge iron deoxidants 29, 30, 31 and 32.
Screening to obtain sponge iron deoxidant with different grain sizes, and combining the sponge iron deoxidant with different grain sizes according to the dissolved oxygen content in the treated water and the dissolved oxygen content in the treated water, so that the sponge iron deoxidant has enough surface area to contact with the dissolved oxygen in the water, and the optimal deoxidization effect is realized. The dissolved oxygen content in the untreated water is about 6mg/L generally, and the dissolved oxygen content in the treated water can reach below 0.02 mg/L.
The normal-temperature sponge iron deoxidant isa filler type deoxidant and can play a role in filtering in the deoxidization process. The floccule of ferric hydroxide generated by the reaction is intercepted by the massive sponge iron deoxidant and accumulated on the surface of the floccule of ferric hydroxide. Due to the uniqueness of the physical properties of the blocky normal-temperature sponge iron deoxidant, the adsorptivity of the intercepted iron hydroxide floccules on the surface of the sponge iron is very small, the polymerization force of a small amount of iron hydroxide floccules generated in the holes on the iron hydroxide floccules on the surface is not large, so that the iron hydroxide floccules on the surface are easy to be removed after being flushed by back flushing water, and the sponge iron deoxidant rapidly recovers the initial activity, thereby the blocky normal-temperature sponge iron deoxidant has a good deoxidant effect. The deoxidant has excellent deoxidization effect when used for treating soft water (or industrial water), and can be widely applied to the anticorrosion treatment of boilers and circulating water facilities.
The sponge iron deoxidant produced by the method has the following characteristics:
1. the pore diameter of the micropores is less than 3 mu m, and the deoxidant reacts with oxygen in water to produce Fe (OH)3The sediment is easily washed away during backwashing, the regeneration effect of the surface of the sponge iron deoxidant is good, the backwashing frequency is low, and the service life is long.
2. Because the oxygen scavenger is directly reduced from lump ore, the oxygen scavenger has high density (2.3-2.6 g/cm)3) High hardness and low abrasion in the process of removing oxygen.
3. The deoxidant only produces Fe (OH) in the deoxidization process3Sediment, backwash, Fe (OH)3The sediment is flushed out, and no other harmful substances are discharged.
4. Can be continuously produced in large scale and has stable quality.
Example (b):
the raw materials are south Africa Xixing hematite (total iron 66.3%) and Shanxi Shenfu coal (fixed carbon 50.4%). According to the ore adding amount of 27.5t/h, the granularity is 5-18 mm. Adding coal 9.5t/h, the granularity is less than or equal to 50 mm. 0.75t/h of limestone and less than or equal to 4mm of granularity. 5.2t/h of coarse coal injection, and 6-12.5 mm of granularity. 2.6t/h of fine coal injection and 0.5-12.5 mm of granularity. The temperature of the reduction section is controlled to be 840-1070 ℃, the temperature of the preheating section is controlled to be 670-840 ℃, the rotating speed of the rotary kiln is 0.42 r/min, and the pressure of the kiln head (discharge end) is kept at micro-positive pressure (3 mmH)2O)。
The diameter of the rotary kiln is phi 5m, the length of the rotary kiln is 80m, the length of the preheating section is 30m, and the length of the reduction section is 50 m.
Screening the semi-finished product of the sponge iron deoxidant by a vibrating screen, winnowing by a winnowing machine, and magnetically separating by a magnetic separator, and separating the sponge iron deoxidant from residual carbon and nonmagnetic substances to obtain a finished product, namely the massive normal-temperature sponge iron deoxidant. The deoxidant is filled in a deaerator with the water treatment capacity of 20t/h, the diameter is 1.2m, the filling height is 1.1m, and the grain size is different from 1-12.5 mm. The content of dissolved oxygen in the unoxidized water is about 5.8 mg/L. The flow rate of water in the deaerator is 17m/h, the backwashing is carried out once in 24h, and the strength of backwashing water is 19L/m2·S，21The oxygen removing effect is kept below 0.04mg/L and basically about 0.015mg/L all the time (see figure 3).
Claims (3)
1. A method for producing sponge iron deoxidant of normal atmospheric temperature with reducing the rotary kiln, characterized by that said method comprises using lumpy hematite, brown coal and a small amount of limestone to add into rotary kiln according to certain proportion, control and carry on the reduction under the specific temperature and reducing atmosphere; the sponge iron deoxidant is prepared from hematite, lignite and a small amount of limestone as raw materials, wherein the total iron content of the hematite is not less than 66%, the particle size of the hematite is 5-20 mm, and the continuous adding speed of the hematite is 18-30.5 t/h; the fixed carbon content of the coal is 45-55%, the ash content of the coal is less than 20%, and the softening temperature of the ash content is higher than 1200 ℃; the ratio of the hematite to the coal fed into the kiln is that the carbon-iron ratio is 0.45-0.52; the particle size of limestone is 2-4 mm, the addition amount of the limestone is 4-6% of the total iron content of the hematite, and the limestone, the hematite and coal are continuously added at the tail of a kiln together;
the lignite added into the rotary kiln is divided into three parts of added coal, coarse coal injection and fine coal injection:
(1) the first part is added coal which accounts for 52-65% of the total coal amount in the kiln, the granularity of the first part is less than or equal to 50mm, the first part, hematite and limestone are continuously added into the kiln from the kiln tail,
(2) the second part is coarse coal injection accounting for 23.3-32% of the total coal entering the kiln, the granularity of the coarse coal injection is 6-12.5 mm, thecoarse coal injection is continuously injected into the kiln from the kiln head,
(3) the third part is fine coal injection, which accounts for 11.7-16.2% of the total coal quantity in the kiln, wherein: 65% of the powder with the particle size of less than or equal to 6mm and 35% of the powder with the particle size of 6-12.5 mm, and continuously spraying the powder into the kiln through a kiln head;
the reduction temperature of the reduction rotary kiln is controlled as follows: the temperature of the preheating section is 670-840 ℃, the temperature of the reduction section is 840-1070 ℃, and the temperature is low at the tail of the kiln and high at the head of the kiln; the rotating speed of the rotary kiln is 0.36-0.44 r/min according to different ore quantities continuously entering the kiln.
2. The method of claim 1, wherein said kiln head pressure is maintained at a slight positive pressure2～3mmH2O。
3. A process according to claim 1 or claim 2, characterized in that the coal has an ash content of less than 20% and an ash softening temperature of greater than 1200 ℃.
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| CN99122291A CN1089371C (en) | 1999-11-10 | 1999-11-10 | Normal temperature sponge iron deoxidizing agent production method |
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| CN99122291A CN1089371C (en) | 1999-11-10 | 1999-11-10 | Normal temperature sponge iron deoxidizing agent production method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107201420A (en) * | 2017-04-14 | 2017-09-26 | 爱润森德（天津）能源科技有限公司 | The energy comprehensive utilization system and its production technology of a kind of smelting in rotary kiln sponge iron |
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| US4181520A (en) * | 1975-01-14 | 1980-01-01 | Metallgesellschaft Aktiengesellschaft | Process for the direct reduction of iron oxide-containing materials in a rotary kiln |
| DE3527621A1 (en) * | 1985-08-01 | 1987-02-05 | Metallgesellschaft Ag | DEVICE FOR SEPARATING RBERGRAIN FROM THE HOT DISCHARGE MATERIAL OF A TURNTUBE IN THE DIRECT REDUCTION OF MATERIALS CONTAINING IRON OXIDE TO IRON SPONGE |
| CN1043660C (en) * | 1996-11-21 | 1999-06-16 | 北京洁明技贸公司 | Method for prodn. of sponge iron filtering material used for deoxidizing device |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107201420A (en) * | 2017-04-14 | 2017-09-26 | 爱润森德（天津）能源科技有限公司 | The energy comprehensive utilization system and its production technology of a kind of smelting in rotary kiln sponge iron |
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