阅读说明：本技术 一种不带入污染性铬元素的通用水泥生产方法 (Production method of general cement without polluting chromium element ) 是由 段平娥 高小育 于 2021-10-09 设计创作，主要内容包括：本发明公开了一种不带入污染性铬元素的通用水泥生产方法,通过在常规通用水泥生产工艺的粉磨工序环节加入复合型除铬剂,并利用粉磨过程使复合型除铬剂接触均匀,达到良好的除铬效果。本方法使用的复合型除铬剂具有良好的分散性和储存性,本方法应用领域广,适合于各类通用水泥的制备。(The invention discloses a method for producing general cement without polluting chromium elements, which adds a compound chromium removing agent in the grinding procedure of the conventional general cement production process, and utilizes the grinding process to ensure that the compound chromium removing agent is uniformly contacted, thereby achieving good chromium removing effect. The composite chromium remover used in the method has good dispersibility and storability, and the method has wide application field and is suitable for preparing various universal cements.)

1. A production method of general cement without polluting chromium elements comprises the following steps:

s1 raw material crushing and pre-homogenizing: crushing the limestone raw material into particles with the particle size of 25-75 mm, and then piling the particles, wherein the storage time is 5-10 d;

preparation of raw material S2: mixing the pre-homogenized limestone particles with clay and iron powder to obtain raw materials, grinding the raw materials, carrying out air flow separation and collection treatment, and storing collected products for 1-2 days before homogenization;

s3 raw material homogenization: putting the raw materials into a homogenizing warehouse, metering the raw materials processed by the homogenizing warehouse through an automatic weighing system, and feeding the raw materials into a preheating system;

s4 preheating and decomposing raw material: the raw material is sent into a rotary kiln for calcination after heat exchange, temperature rise and decomposition, and the decomposition rate of the raw material in the working procedure is controlled to be more than 90 percent;

and (3) sintering of S5 clinker: raw materials are fed from the tail part of the rotary kiln and are subjected to rotary calcination, the calcination temperature is controlled to be 1350-1450 ℃, the materials are discharged from the kiln head, and the clinker enters a clinker warehouse to be stored for 10-15 days;

s6 grinding: mixing the stored clinker with desulfurized gypsum, limestone, furnace slag and slag to obtain a clinker mixture, adding a compound chromium removal agent into the clinker mixture, and then grinding to obtain cement powder;

and S7 packaging products: and weighing and packaging the cement powder to obtain the cement product.

2. The method for producing universal cement without introducing polluting chromium elements as claimed in claim 1, wherein: the addition amount of the composite chromium removing agent is 0.05-0.08 wt% of the clinker mixture.

3. A method for producing universal cement without introducing polluting chromium elements according to claim 1 or 2, characterized in that: the composite chromium removing agent is prepared from a reducing agent, calcium stearate and an anticaking agent in a mass ratio of (18-25): (6-9): 1 of the mixture formed.

4. A method for producing universal cement without introducing polluting chromium elements according to claim 3, characterized in that: the composite chromium removing agent is prepared from a reducing agent, calcium stearate and an anticaking agent in a mass ratio of 20: 9: 1 of the mixture formed.

5. A method for producing universal cement without introducing polluting chromium elements according to claim 3, characterized in that: the anticaking agent is any one of potassium ferrocyanide, tricalcium phosphate, silicon dioxide and microcrystalline cellulose.

6. A method for producing universal cement without introducing polluting chromium elements according to claim 3, characterized in that: the reducing agent is any one of ferrous phthalocyanine, a dispersion type reduction composite material and an oriented type reduction composite material.

7. The method for producing universal cement without introducing polluting chromium elements as claimed in claim 6, wherein: the preparation method of the dispersion type reduction composite material comprises the following steps: mixing 2.5-4 parts of reduced graphene oxide and 375-600 parts of methanesulfonic acid by weight of X1, and performing ultrasonic treatment for 45-60 min at power of 550-850W to obtain a reduced graphene oxide suspension for later use; adding 4-6 parts by weight of ferrous phthalocyanine into the reduced graphene oxide suspension obtained in the step X1 by X2, and mixing at a stirring speed of 300-480 rpm for 15-30 min to obtain a ferrous phthalocyanine mixed solution for later use; and X3, adding the ferrous phthalocyanine mixed solution obtained in the step X2 into 1500-2000 parts of water by weight, mixing at a stirring speed of 60-120 rpm for 0.5-1 h, standing for 1-2 h, finally, centrifuging the mixture at a speed of 8000-12000 rpm, filtering to obtain a solid centrifugal product, washing the centrifugal product with water and alcohol until the pH value is neutral, freeze-drying at-60-80 ℃ for 8-12 h, crushing, and sieving to obtain the dispersed reduction composite material.

8. The cement prepared by the general cement production method without polluting chromium elements according to any one of claims 1 to 7.

Technical Field

The invention relates to the technical field of cement preparation, in particular to a production method of general cement without polluting chromium elements.

Background

The cement is a building material with wide application, is inseparable with the production and life of human beings, and people have a great deal of chances of contacting with cement products in daily life. In the production and manufacturing process of cement, substances harmful to human bodies or the environment are introduced due to the influence of factors such as preparation processes, raw materials and the like. Hexavalent chromium or water-soluble chromium (vi) is a common harmful element contained in cement, hexavalent chromium has water solubility, and in the classification of harmful substances, hexavalent chromium belongs to a swallowable poison and a suction polar poison, has very obvious harm to human bodies, can cause skin allergy by contacting with human skin, has carcinogenicity after being sucked into human bodies, belongs to a first group of substances listed in the list of toxic and harmful water pollutants, and has continuous harm to the environment. Therefore, in the health and environmental needs, the hexavalent chromium content must be controlled in the production of cement.

Patent CN 111320402A discloses a cement production process capable of reducing chromium content in cement, which reduces the chromium content in cement by introducing barium-containing waste residue in preparation and optimizing production flow, but the invention has more requirements on raw materials and narrower application field; patent CN 113087428A provides a chromium reducing agent, a preparation method thereof and cement, sodium nitrite is used as a chromium removing agent instead of ferrous sulfate to reduce the chromium content of the cement, but the invention can increase the alkali content in the cement and possibly reduce the mechanical property of the cement under complicated climatic conditions.

Disclosure of Invention

In view of the above defects in the prior art, the technical problem to be solved by the present invention is to provide a method for producing general purpose cement without polluting chromium elements, to reduce the content of polluting chromium elements in the finished cement product, and to solve the problems in the prior art that ferrous sulfate used as a chromium removing agent is easy to oxidize and difficult to store, and has poor dispersibility due to agglomeration.

In the prior art, a reducing agent method is mainly used for eliminating the influence of polluting chromium elements in cement, namely, reducing hexavalent chromium with strong pollution in the cement into trivalent chromium with low toxicity by using a reducing agent. The reducing agents commonly used in the prior art include ferrous sulfate, zinc salt, manganese salt, organic aldehyde reducing agents, sodium borohydride and the like. The reducing agent has obvious defects, and the zinc salt has strong hygroscopicity, can absorb moisture in air to deteriorate, has more storage requirements and high use cost, and is difficult to realize large-scale application; although the manganese salt, the organic aldehyde reducing agent and the sodium borohydride can reduce the polluting hexavalent chromium in the cement, the manganese salt, the organic aldehyde reducing agent and the sodium borohydride have certain toxicity, secondary pollution is easily caused by improper use, and the application field is narrow; ferrous sulfate is a reducing agent which is most widely applied in the prior art, has low price and relatively small toxic and side effects, but also has the problems of easy oxidation, difficult storage and caking caused by moisture absorption, and the difference of the chromium removal effect of the ferrous sulfate before and after cement grinding is large because the ferrous sulfate is more easily combined with oxygen in the air to be oxidized in a high-temperature environment generated by grinding friction, thereby reducing the chromium removal performance.

In long-term production practice, the inventor finds that compared with the method of adding the chromium-removing reducing agent after cement grinding, the method has a better theoretical chromium-removing effect by adding the reducing agent in the grinding process, the reducing agent and the cement can be uniformly mixed by utilizing the grinding process, reducing substances are more fully contacted with hexavalent chromium in the grinding process, and pollution is reduced. However, due to the high temperature environment of the grinding process, the stability of the reducing agent in the process is poor, and the actual chromium removal performance is lower than the effect of adding the reducing agent after grinding. The inventor finds that the phthalocyanine is a planar macrocyclic conjugated system consisting of four isoindole units, and has higher stability to light and heat due to the unique molecular configuration; because the molecular center has a cavity structure, the phthalocyanine has strong coordination capability and can coordinate with metal elements to form a complex. Based on the physicochemical characteristics of phthalocyanine, the inventor uses phthalocyanine ferrous iron obtained by coordinating phthalocyanine and ferrous iron particles as a chromium reducing agent. The ferrous phthalocyanine has better stability than ferrous sulfate in the grinding process, and on one hand, the planar macrocyclic conjugated system of the ferrous phthalocyanine can reduce the contact between ferrous iron at the center and air and reduce the loss of a reducing agent caused by air oxidation; on the other hand, the existence of the conjugated system effectively provides steric hindrance, can prevent agglomeration of the reducing agent, improves the dispersibility of the reducing agent and is beneficial to storage.

The inventor combines a reducing agent, calcium stearate and an anticaking agent according to a specific proportion to obtain the chromium removing agent with good chromium removing effect. The calcium stearate is added into the chromium removing agent, stearic acid anions are favorable for promoting the adsorption of trivalent chromium and forming chromium stearate, the reduction of hexavalent chromium into trivalent chromium is a dynamic balance process according to a chemical reaction balance mechanism, and when the concentration of the reduced trivalent chromium and the trivalent chromium existing in cement is reduced due to the adsorption of stearate radicals, the reaction is favorable for developing towards the direction of reduction reaction, so that the reduction effect of the reducing agent on the hexavalent chromium is improved.

In order to achieve the purpose, the invention adopts the following technical scheme:

a production method of general cement without polluting chromium elements comprises the following steps:

s1 raw material crushing and pre-homogenizing: crushing the limestone raw material into particles with the particle size of 25-75 mm by using a conventional crusher, and then piling the particles, wherein the storage time is 5-10 d;

preparation of raw material S2: mixing the pre-homogenized limestone particles with clay and iron powder to obtain raw materials, grinding the raw materials, carrying out air flow separation and collection treatment, and storing collected products for 1-2 days before homogenization;

s3 raw material homogenization: the conventional homogenization method in the field is adopted, the raw materials are placed into a homogenization warehouse by a material distributor, and the raw materials treated by the homogenization warehouse are metered by an automatic weighing system and sent into a preheating system;

s4 preheating and decomposing raw material: the raw material is preheated by the conventional method in the field, and is sent into a rotary kiln for calcination after heat exchange, temperature rise and decomposition, and the decomposition rate of the raw material in the working procedure is controlled to be more than 90%;

and (3) sintering of S5 clinker: raw materials are fed from the tail part of the rotary kiln and are subjected to rotary calcination, the calcination temperature is controlled to be 1350-1450 ℃, the materials are discharged from the kiln head, and the clinker enters a clinker warehouse through a conveying device and is stored for 10-15 days;

s6 grinding: mixing the stored clinker with desulfurized gypsum, limestone, furnace slag and slag to obtain a clinker mixture, adding a compound chromium removal agent into the clinker mixture, and then grinding to obtain cement powder;

and S7 packaging products: and weighing and packaging the cement powder to obtain the cement product.

Preferably, the composition of the raw material in step S2 is 12-18 wt% of clay, 2-4 wt% of iron powder, and the balance being limestone particles after pre-homogenization.

Preferably, the clinker mixture in step S6 comprises desulfurized gypsum 4-6 wt%, limestone 5-7.5 wt%, slag 4-6 wt%, and the balance of the stored clinker.

Preferably, the addition amount of the compound chromium removing agent in the step S6 is 0.05-0.08 wt% of the clinker mixture.

Preferably, in the step S6, the composite chromium removing agent is a reducing agent, calcium stearate, and an anti-caking agent in a mass ratio (18-25): (6-9): 1 of the mixture formed.

Preferably, the anticaking agent is any one of potassium ferrocyanide, tricalcium phosphate, silicon dioxide and microcrystalline cellulose.

Preferably, the reducing agent is any one of ferrous phthalocyanine, a dispersion-type reduction composite material and an orientation-type reduction composite material.

On the basis of the prior art scheme, the inventor makes an improvement, the reduced graphene oxide can provide a larger surface area for reducing hexavalent chromium, and the reduced graphene oxide and a reducing agent are combined to prepare the composite material. The reduced graphene oxide has a reticular thin layer structure, so that on one hand, agglomeration and caking of the reducing agent due to electrostatic attraction can be prevented, and the reducing agent distributivity is improved; on the other hand, the method is beneficial to the electronic exchange between the reducing agent and the hexavalent chromium, and further improves the reducing capability of the reducing agent.

Preferably, the preparation method of the dispersion type reduction composite material comprises the following steps:

mixing 2.5-4 parts of reduced graphene oxide and 375-600 parts of methanesulfonic acid by weight of X1, and performing ultrasonic treatment for 45-60 min at power of 550-850W to obtain a reduced graphene oxide suspension for later use;

adding 4-6 parts by weight of ferrous phthalocyanine into the reduced graphene oxide suspension obtained in the step X1 by X2, and mixing at a stirring speed of 300-480 rpm for 15-30 min to obtain a ferrous phthalocyanine mixed solution for later use;

and X3, adding the ferrous phthalocyanine mixed solution obtained in the step X2 into 1500-2000 parts of water by weight, mixing at a stirring speed of 60-120 rpm for 0.5-1 h, standing for 1-2 h, finally, centrifuging the mixture at a speed of 8000-12000 rpm, filtering to obtain a solid centrifugal product, washing the centrifugal product with water and alcohol until the pH value is neutral, freeze-drying at-60-80 ℃ for 8-12 h, crushing, and sieving to obtain the dispersed reduction composite material.

In order to improve the directional adsorption capacity of the dispersion type reduction composite material to hexavalent chromium, the inventor further improves the reduction-oxidation graphene serving as a base material in the composite material, introduces active groups such as calcium ions on the surface of the reduction-oxidation graphene, directionally combines the active groups with hexavalent chromium in cement through strong interaction, and reduces the hexavalent chromium into trivalent chromium by using a reducing agent.

Preferably, the preparation method of the directional reduction composite material comprises the following steps:

y1, ultrasonically treating 3-5 parts of reduced graphene oxide and 800-1200 parts of water for 1-2 hours at the power of 550-850W by weight, continuously adding 15-20 parts of calcium nitrate and 8-12 parts of diammonium hydrogen phosphate after the ultrasonic treatment is finished, and mixing and reacting at the stirring speed of 480-720 rpm for 1-2 hours to obtain a reaction mixed solution for later use;

y2, adjusting the pH of the reaction mixed liquid obtained in the step Y1 to 10-11 by using a sodium hydroxide aqueous solution with the concentration of 1-2 mol/L, mixing for 3-4 h at the stirring speed of 360-480 rpm, then reducing the stirring speed to 120-180 rpm, continuing mixing for 4-6 h, filtering, washing with water, washing with alcohol, freeze-drying for 8-12 h at the temperature of-60 to-80 ℃, crushing and sieving to obtain the directional adsorption type reduced graphene oxide for later use;

y3, mixing 2.5-4 parts by weight of the oriented adsorption type reduced graphene oxide obtained in the step Y2 with 375-600 parts by weight of methanesulfonic acid, and carrying out ultrasonic treatment for 45-60 min at 550-850W to obtain an oriented adsorption type reduced graphene oxide suspension for later use;

y4, adding 4-6 parts by weight of ferrous phthalocyanine into the directional adsorption type reduced graphene oxide suspension obtained in the step Y3, and mixing at a stirring speed of 300-480 rpm for 15-30 min to obtain a ferrous phthalocyanine mixed solution for later use;

y5, adding the ferrous phthalocyanine mixed solution obtained in the step Y4 into 1500-2000 parts of water by weight, mixing at a stirring speed of 60-120 rpm for 0.5-1 h, standing for 1-2 h, finally, centrifuging the mixture at a speed of 8000-12000 rpm, filtering to obtain a solid centrifugal product, washing the centrifugal product with water and alcohol until the pH value is neutral, freeze-drying at-60-80 ℃ for 8-12 h, crushing, and sieving to obtain the oriented reduction composite material.

The introduction and the function of each raw material in the formula of the invention are as follows:

iron phthalocyanine: the chemical intermediate, the complex formed by the coordination of phthalocyanine and iron element, the plane large ring conjugate system composed of four isoindole units at the periphery of the molecule, has higher stability to light and heat, and is used as the reducing agent of polluting chromium element.

Calcium stearate: the organic compound and white powder can be used as a waterproof agent, a lubricant, a clinker additive and the like, and the chromium removing agent is used as an auxiliary material of the chromium removing agent to increase the lubricity, participate in absorbing trivalent chromium and enhance the reduction effect of a reducing agent on hexavalent chromium.

Reducing graphene oxide: the material obtained by reducing graphene oxide and removing surface oxidized functional groups has stable properties, and is used as a matrix to be combined with ferrous phthalocyanine to form a composite material, so that the dispersion performance of the ferrous phthalocyanine is improved.

Ammonium hydrogen phosphate: inorganic substances, colorless transparent monoclinic crystals or white powders, are used as raw materials for processing reduced graphene oxide in the invention.

On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

The invention has the beneficial effects that:

compared with the prior art, the composite chromium removing agent is added in the cement grinding process, so that a good chromium removing effect is achieved, the composite chromium removing agent is stable in performance and good in dispersity, and the problems that a ferrous sulfate chromium removing agent in the prior art is poor in stability, easy to oxidize and absorb moisture and agglomerate are solved.

Compared with the prior art, the invention uses the ferrous phthalocyanine as the main component of the compound chromium remover, the periphery of the ferrous phthalocyanine molecule is provided with a plane large ring conjugated system consisting of four isoindole units, the stability to light and heat is higher, the contact between ferrous iron at the center and air can be reduced, and the loss of a reducing agent caused by air oxidation is reduced.

Compared with the prior art, the invention provides a dispersion type reduction composite material consisting of ferrous phthalocyanine and reduced graphene oxide, and the material prevents the reducing agent from agglomerating due to electrostatic attraction by utilizing a reticular thin layer structure of the reduced graphene oxide, so that the distributivity of the reducing agent is improved; in addition, the method is favorable for the electronic exchange between the reducing agent and the hexavalent chromium, and improves the reducing capability of the reducing agent.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

Some raw material parameters in the comparative examples and examples of the invention are as follows:

ferrous phthalocyanine, Wuhanxin Wei, and chemical industries, Inc., CAS number: 132-16-1;

calcium stearate, wuhanxinchang chemical limited liability company, CAS No.: 1592-23-0;

reduced graphene oxide, particle size 1000 mesh, Henan hexa-Industrial graphite Ltd;

diammonium phosphate, suzhou longheng chemical ltd, CAS number: 7783-28-0.

Example 1

A method for producing ordinary Portland cement 42.5 without polluting chromium elements comprises the following steps:

s1 raw material crushing and pre-homogenizing: crushing the limestone raw material into particles with the particle size of 40mm by using a crusher, and then piling the particles in a circular homogenizing storage yard with the diameter of 100m for 10 days;

preparation of raw material S2: mixing the pre-homogenized limestone particles serving as a raw material main body with clay and iron powder by a conveying device to obtain a raw material, grinding, separating air flow and collecting the raw material by adopting a conventional method in the field, and storing the collected product for 1.5 days before homogenization; the raw material comprises 18 wt% of clay, 3 wt% of iron powder and the balance of limestone particles after pre-homogenization;

s3 raw material homogenization: placing the raw materials into a homogenizing warehouse by using a material distributor, metering the raw materials processed by the homogenizing warehouse by using an automatic weighing system, and feeding the raw materials into a preheating system;

s4 preheating and decomposing raw material: the raw material is sent into a rotary kiln for calcination after heat exchange, temperature rise and decomposition, and the decomposition rate of the raw material is 96 percent;

and (3) sintering of S5 clinker: raw materials are fed from the tail part of the rotary kiln and are subjected to rotary calcination, the firing temperature is 1350 ℃, the raw materials are discharged from the kiln head, and the clinker enters a clinker warehouse through a conveying device to be stored for 12d to obtain the stored clinker;

s6 grinding: mixing desulfurized gypsum, limestone, slag and clinker to obtain a clinker mixture, continuously adding a composite chromium removing agent which accounts for 0.06 wt% of the mass of the clinker mixture into the clinker mixture, mixing, and sending the mixture into a grinding device for processing to obtain cement powder, wherein the fineness of the cement powder is 325 meshes; in the clinker mixture, the desulfurized gypsum accounts for 4 wt%, the limestone accounts for 5 wt%, the slag accounts for 6 wt%, the slag accounts for 5 wt%, and the balance is clinker;

and S7 packaging products: and weighing and packaging the cement powder to obtain the cement product.

The composite chromium remover is prepared from ferrous phthalocyanine and calcium stearate in a mass ratio of (20): 9, and (c) forming a mixture.

Example 2

A method for producing ordinary Portland cement 42.5 without polluting chromium elements comprises the following steps:

s1 raw material crushing and pre-homogenizing: crushing the limestone raw material into particles with the particle size of 40mm by using a crusher, and then piling the particles in a circular homogenizing storage yard with the diameter of 100m for 10 days;

preparation of raw material S2: mixing the pre-homogenized limestone particles serving as a raw material main body with clay and iron powder by a conveying device to obtain a raw material, grinding, separating air flow and collecting the raw material by adopting a conventional method in the field, and storing the collected product for 1.5 days before homogenization; the raw material comprises 18 wt% of clay, 3 wt% of iron powder and the balance of limestone particles after pre-homogenization;

s3 raw material homogenization: placing the raw materials into a homogenizing warehouse by using a material distributor, metering the raw materials processed by the homogenizing warehouse by using an automatic weighing system, and feeding the raw materials into a preheating system;

s4 preheating and decomposing raw material: the raw material is sent into a rotary kiln for calcination after heat exchange, temperature rise and decomposition, and the decomposition rate of the raw material is 96 percent;

and (3) sintering of S5 clinker: raw materials are fed from the tail part of the rotary kiln and are subjected to rotary calcination, the firing temperature is 1350 ℃, the raw materials are discharged from the kiln head, and the clinker enters a clinker warehouse through a conveying device to be stored for 12d to obtain the stored clinker;

s6 grinding: mixing desulfurized gypsum, limestone, slag and clinker to obtain a clinker mixture, continuously adding a composite chromium removing agent which accounts for 0.06 wt% of the mass of the clinker mixture into the clinker mixture, mixing, and sending the mixture into a grinding device for processing to obtain cement powder, wherein the fineness of the cement powder is 325 meshes; in the clinker mixture, the desulfurized gypsum accounts for 4 wt%, the limestone accounts for 5 wt%, the slag accounts for 6 wt%, the slag accounts for 5 wt%, and the balance is clinker;

and S7 packaging products: and weighing and packaging the cement powder to obtain the cement product.

The composite chromium remover is prepared from ferrous phthalocyanine and silicon dioxide in a mass ratio of (20): 1 of the mixture formed.

Example 3

A method for producing ordinary Portland cement 42.5 without polluting chromium elements comprises the following steps:

s1 raw material crushing and pre-homogenizing: crushing the limestone raw material into particles with the particle size of 40mm by using a crusher, and then piling the particles in a circular homogenizing storage yard with the diameter of 100m for 10 days;

preparation of raw material S2: mixing the pre-homogenized limestone particles serving as a raw material main body with clay and iron powder by using a conveying device to obtain a raw material, wherein the water content of the mixed raw material is 2.5 wt%, grinding, airflow separation and collection of the raw material are carried out by adopting a conventional method in the field, and the collected product is stored for 1.5 days before homogenization; the raw material comprises 18 wt% of clay, 3 wt% of iron powder and the balance of limestone particles after pre-homogenization;

s3 raw material homogenization: placing the raw materials into a homogenizing warehouse by using a material distributor, metering the raw materials processed by the homogenizing warehouse by using an automatic weighing system, and feeding the raw materials into a preheating system;

s4 preheating and decomposing raw material: the raw material is sent into a rotary kiln for calcination after heat exchange, temperature rise and decomposition, and the decomposition rate of the raw material is 96 percent;

and (3) sintering of S5 clinker: raw materials are fed from the tail part of the rotary kiln and are subjected to rotary calcination, the firing temperature is 1350 ℃, the raw materials are discharged from the kiln head, and the clinker enters a clinker warehouse through a conveying device to be stored for 12d to obtain the stored clinker;

s6 grinding: mixing desulfurized gypsum, limestone, slag and clinker to obtain a clinker mixture, continuously adding a composite chromium removing agent which accounts for 0.06 wt% of the mass of the clinker mixture into the clinker mixture, mixing, and sending the mixture into a grinding device for processing to obtain cement powder, wherein the fineness of the cement powder is 325 meshes; in the clinker mixture, the desulfurized gypsum accounts for 4 wt%, the limestone accounts for 5 wt%, the slag accounts for 6 wt%, the slag accounts for 5 wt%, and the balance is clinker;

and S7 packaging products: and weighing and packaging the cement powder to obtain the cement product.

The composite chromium remover is prepared from ferrous phthalocyanine, calcium stearate and silicon dioxide in a mass ratio of (20): 9: 1 of the mixture formed.

Example 4

A method for producing ordinary Portland cement 42.5 without polluting chromium elements comprises the following steps:

s1 raw material crushing and pre-homogenizing: crushing the limestone raw material into particles with the particle size of 40mm by using a crusher, and then piling the particles in a circular homogenizing storage yard with the diameter of 100m for 10 days;

preparation of raw material S2: mixing the pre-homogenized limestone particles serving as a raw material main body with clay and iron powder by a conveying device to obtain a raw material, grinding, separating air flow and collecting the raw material by adopting a conventional method in the field, and storing the collected product for 1.5 days before homogenization; the raw material comprises 18 wt% of clay, 3 wt% of iron powder and the balance of limestone particles after pre-homogenization;

s3 raw material homogenization: placing the raw materials into a homogenizing warehouse by using a material distributor, metering the raw materials processed by the homogenizing warehouse by using an automatic weighing system, and feeding the raw materials into a preheating system;

s4 preheating and decomposing raw material: the raw material is sent into a rotary kiln for calcination after heat exchange, temperature rise and decomposition, and the decomposition rate of the raw material is 96 percent;

and (3) sintering of S5 clinker: raw materials are fed from the tail part of the rotary kiln and are subjected to rotary calcination, the firing temperature is 1350 ℃, the raw materials are discharged from the kiln head, and the clinker enters a clinker warehouse through a conveying device to be stored for 12d to obtain the stored clinker;

s6 grinding: mixing desulfurized gypsum, limestone, slag and clinker to obtain a clinker mixture, continuously adding a composite chromium removing agent which accounts for 0.06 wt% of the mass of the clinker mixture into the clinker mixture, mixing, and sending the mixture into a grinding device for processing to obtain cement powder, wherein the fineness of the cement powder is 325 meshes; in the clinker mixture, the desulfurized gypsum accounts for 4 wt%, the limestone accounts for 5 wt%, the slag accounts for 6 wt%, the slag accounts for 5 wt%, and the balance is clinker;

and S7 packaging products: and weighing and packaging the cement powder to obtain the cement product.

The composite chromium remover is a dispersion type reduction composite material, calcium stearate and silicon dioxide in a mass ratio of 20: 9: 1 of the mixture formed.

The preparation method of the dispersion type reduction composite material comprises the following steps:

mixing 2.5 parts of reduced graphene oxide and 500 parts of methane sulfonic acid by weight of X1, and carrying out ultrasonic treatment for 60min at the power of 550W to obtain a reduced graphene oxide suspension for later use;

adding 4 parts by weight of ferrous phthalocyanine into the reduced graphene oxide suspension obtained in the step X1 by X2, and mixing at a stirring speed of 480rpm for 25min to obtain a ferrous phthalocyanine mixed solution for later use;

and X3, adding the ferrous phthalocyanine mixed solution obtained in the step X2 into 1800 parts of water by weight, mixing for 1h at a stirring speed of 120rpm, standing for 2h, finally centrifuging the mixture at a speed of 12000rpm, filtering to obtain a solid centrifugal product, washing the solid centrifugal product with water, washing with alcohol until the pH value is neutral, freeze-drying for 8h at-80 ℃, crushing, and sieving with a 200-mesh sieve to obtain the dispersion type reduction composite material.

Example 5

A method for producing ordinary Portland cement 42.5 without polluting chromium elements comprises the following steps:

s1 raw material crushing and pre-homogenizing: crushing the limestone raw material into particles with the particle size of 40mm by using a crusher, and then piling the particles in a circular homogenizing storage yard with the diameter of 100m for 10 days;

preparation of raw material S2: mixing the pre-homogenized limestone particles with clay and iron powder by a conveying device to obtain raw materials, grinding the raw materials, separating gas flow, collecting by conventional method in the field, and storing the collected product for 1.5 days before homogenizing; the raw material comprises 18 wt% of clay, 3 wt% of iron powder and the balance of limestone particles after pre-homogenization;

s3 raw material homogenization: placing the raw materials into a homogenizing warehouse by using a material distributor, metering the raw materials processed by the homogenizing warehouse by using an automatic weighing system, and feeding the raw materials into a preheating system;

s4 preheating and decomposing raw material: the raw material is sent into a rotary kiln for calcination after conventional heat exchange, temperature rise and decomposition, and the decomposition rate of the raw material is 96 percent;

and (3) sintering of S5 clinker: raw materials are fed from the tail part of the rotary kiln and are subjected to rotary calcination, the firing temperature is 1350 ℃, the raw materials are discharged from the kiln head, and the clinker enters a clinker warehouse through a conveying device to be stored for 12d to obtain the stored clinker;

s6 grinding: mixing desulfurized gypsum, limestone, slag and clinker to obtain a clinker mixture, continuously adding a composite chromium removing agent which accounts for 0.06 wt% of the mass of the clinker mixture into the clinker mixture, mixing, and sending the mixture into a grinding device for processing to obtain cement powder, wherein the fineness of the cement powder is 325 meshes; in the clinker mixture, the desulfurized gypsum accounts for 4 wt%, the limestone accounts for 5 wt%, the slag accounts for 6 wt%, the slag accounts for 5 wt%, and the balance is clinker;

and S7 packaging products: and weighing and packaging the cement powder to obtain the cement product.

The composite chromium remover is a directional reduction composite material, calcium stearate and silicon dioxide in a mass ratio of 20: 9: 1 of the mixture formed.

The preparation method of the directional reduction composite material comprises the following steps:

y1, carrying out ultrasonic treatment on 3 parts of reduced graphene oxide and 800 parts of water for 1.5h at the power of 550W by weight, continuously adding 17.5 parts of calcium nitrate and 10 parts of diammonium hydrogen phosphate after the ultrasonic treatment is finished, and mixing and reacting at the stirring speed of 720rpm for 1h to obtain a reaction mixed solution for later use;

y2, adjusting the pH value of the reaction mixed liquor obtained in the step Y1 to 11 by using a sodium hydroxide aqueous solution with the concentration of 1mol/L, mixing for 3 hours at the stirring speed of 480rpm, reducing the stirring speed to 180rpm, continuously mixing for 4 hours, filtering, washing with water, washing with alcohol, freeze-drying for 8 hours at the temperature of minus 80 ℃, crushing, and sieving with a 200-mesh sieve to obtain the directional adsorption type reduced graphene oxide for later use;

y3, mixing 2.5 parts by weight of the oriented adsorption type reduced graphene oxide obtained in the step Y2 with 500 parts by weight of methane sulfonic acid, and carrying out ultrasonic treatment for 60min at 550W to obtain oriented adsorption type reduced graphene oxide suspension for later use;

y4, adding 4 parts by weight of ferrous phthalocyanine into the directional adsorption type reduced graphene oxide suspension obtained in the step Y3, and mixing at a stirring speed of 480rpm for 25min to obtain a ferrous phthalocyanine mixed solution for later use;

y5, adding the ferrous phthalocyanine mixed solution obtained in the step Y4 into 1800 parts of water by weight, mixing for 1h at a stirring speed of 120rpm, standing for 2h, finally centrifuging the mixture at a speed of 12000rpm, filtering to obtain a solid centrifugal product, washing the centrifugal product with water and alcohol until the pH value is neutral, freeze-drying for 8h at-80 ℃, crushing, and sieving with a 200-mesh sieve to obtain the directional reduction composite material.

Comparative example 1

A method for producing ordinary Portland cement 42.5 without polluting chromium elements comprises the following steps:

s1 raw material crushing and pre-homogenizing: crushing the limestone raw material into particles with the particle size of 40mm by using a crusher, and then piling the particles in a circular homogenizing storage yard with the diameter of 100m for 10 days;

preparation of raw material S2: mixing the pre-homogenized limestone particles serving as a raw material main body with clay and iron powder by using a conveying device to obtain a raw material, wherein the water content of the mixed raw material is 2.5 wt%, grinding, airflow separation and collection of the raw material are carried out by adopting a conventional method in the field, and the collected product is stored for 1.5 days before homogenization; the raw material comprises 18 wt% of clay, 3 wt% of iron powder and the balance of limestone particles after pre-homogenization;

s3 raw material homogenization: placing the raw materials into a homogenizing warehouse by using a material distributor, metering the raw materials processed by the homogenizing warehouse by using an automatic weighing system, and feeding the raw materials into a preheating system;

s4 preheating and decomposing raw material: the raw material is sent into a rotary kiln for calcination after heat exchange, temperature rise and decomposition, and the decomposition rate of the raw material is 96 percent;

and (3) sintering of S5 clinker: raw materials are fed from the tail part of the rotary kiln and are subjected to rotary calcination, the firing temperature is 1350 ℃, the raw materials are discharged from the kiln head, and the clinker enters a clinker warehouse through a conveying device to be stored for 12d to obtain the stored clinker;

s6 grinding: mixing desulfurized gypsum, limestone slag, slag and clinker to obtain a clinker mixture, continuously adding a composite chromium removing agent which accounts for 0.06 wt% of the mass of the clinker mixture into the clinker mixture, mixing, and sending the mixture into a grinding device for processing to obtain cement powder, wherein the fineness of the cement powder is 325 meshes; in the clinker mixture, the desulfurized gypsum accounts for 4 wt%, the limestone accounts for 5 wt%, the slag accounts for 6 wt%, the slag accounts for 5 wt%, and the balance is clinker;

and S7 packaging products: and weighing and packaging the cement powder to obtain the cement product.

Test example 1

The water-soluble chromium (VI) content was measured on Portland cement 42.5 produced using the universal cement production method of the invention without introducing contaminating chromium elements. The test method is carried out according to the specific requirements of GB 31893-. The results of the 42.5 water-soluble chromium (VI) content test of the Portland cement produced by the general cement production method without introducing polluting chromium elements are shown in Table 1.

Table 1: table of water-soluble chromium (vi) content test results

Test set	Water soluble chromium (VI) content (mg/kg)
		Example 1	5.63
Example 2	6.17
		Example 3	4.98
Example 4	3.87
		Example 5	3.46
Comparative example 1	14.60

The polluting chromium element in the cement production mainly comes from chromium elements contained in processing equipment or raw material ores, and the lower the hexavalent chromium content in the cement is, the lower the pollution of chromium in the cement is. It can be seen from the comparison between the examples and the comparative examples that the method for producing the universal cement without introducing the polluting chromium element can reduce the content of hexavalent chromium in the finished cement product by adding the compound chromium remover in the cement grinding process. The reason may be that ferrous phthalocyanine obtained by coordination of phthalocyanine and ferrous iron particles is used as a chromium reducing agent, the stability is good in the grinding process, a planar macrocyclic conjugated system of phthalocyanine can reduce the contact between ferrous iron at the center and air, the loss of the reducing agent caused by air oxidation is reduced, meanwhile, the reducing agent, calcium stearate and an anticaking agent are combined according to a specific proportion, stearic acid anions are favorable for promoting the adsorption of trivalent chromium and forming chromium stearate, according to a chemical reaction balance mechanism, the reduction of hexavalent chromium into trivalent chromium is a dynamic balance process, and when the concentration of the reduced trivalent chromium and the trivalent chromium existing in cement is reduced due to the adsorption of stearate, the reaction is favorable for developing towards the direction of the reduction reaction, so that the reduction effect of the reducing agent on the hexavalent chromium is improved.

Test example 2

The hygroscopicity of the compound chromium removal agent used in the general cement production method without polluting chromium elements is tested, and the test is carried out according to the specific requirements of GB/T1913-. The test temperature was 25 ℃, the ambient air humidity was 50%, each group was tested 6 times, and the results were averaged. The moisture absorption test results of the composite chromium removing agent are shown in Table 2.

Table 2: compound chromium removing agent hygroscopicity test result table

The moisture absorption rate reflects the capacity of dust to absorb water from ambient air, and in the use of the field, the lower the moisture absorption rate of the chromium removing agent is, the more the application requirement can be met, and the higher the moisture absorption rate of the chromium removing agent is, the more difficult the chromium removing agent is to be stored in practical application. The comparison of the examples shows that the composite material composed of the ferrous phthalocyanine and the reduced graphene oxide has a lower moisture absorption rate compared with the ferrous phthalocyanine, and the reason for the composite material is probably that the reduced graphene oxide has few hydrophilic groups on the surface, is not easy to combine with water molecules, can delay the processes of moisture absorption, agglomeration and deterioration of the chromium removal agent, and is beneficial to long-time storage.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.