CN1153140A

CN1153140A - Method for producing potassium sulfate, iron protocarbonate and compound fertilizer using waste acid liquor from titanium pigment plant

Info

Publication number: CN1153140A
Application number: CN 95112616
Authority: CN
Inventors: 刘璞
Original assignee: WUHAN ENVIRONMENT PROTECTION BUREAU
Current assignee: WUHAN ENVIRONMENT PROTECTION BUREAU
Priority date: 1995-12-29
Filing date: 1995-12-29
Publication date: 1997-07-02

Abstract

A process for preparing potassium sulfate, ferrous carbonate and compound fertilizer with waste acidic liquid from titanium oxide plant includes such steps as addition of ammonia for neutralization, filtering, addition of potassium chloride to filtrate for metathesis, and processing by ammonium carbonate to obtain said title products. Its advantages are low cost and favouring to environmental protection.

Description

Method for producing potassium sulfate, ferrous carbonate and compound fertilizer by using waste acid liquor of titanium dioxide factory

The invention relates to the technical field of chemical products, in particular to a method for producing potassium sulfate, ferrous carbonate and compound fertilizer by using waste acid liquor of an iron white powder factory.

Titanium dioxide is a chemical product, more than 60 manufacturers (distributed in 16 provinces and cities) exist in China, the total output is about 10 ten thousand tons/year, and the quantity of the waste acid liquid is about 8 times of the output, namely 80 ten thousand tons/year. Comprises the following components: containing sulfuric acid (H)₂SO₄) 15-20 percent of iron sulfate, 5-8 percent of ferrous sulfate, and the other components of water and a small amount of substances such as titanium, aluminum, chromium, barium, magnesium, manganese, phosphate and the like. If the pollution is discharged to the outside and causes serious pollution to the environment, the pollution is generally existed in fact. To solve this problem, many organizations and individuals have done a lot of work for many years, and up to now, five treatment methods have been known, which are summarized as follows:

and (I) adding a large amount of water for dilution and then discharging the water to the outside. The method is contrary to the national environmental protection law and can not be used for a long time.

And (II) neutralizing and filtering the mixture by using lime milk or calcium carbonate, and discharging the product. The method can eliminate acid liquor pollution, but consumes a large amount of lime or calcium carbonate, generates a large amount of solid waste, and is unreasonable in economic and environmental protection effects.

And (III) adding iron scraps to react to produce ferrous sulfate. Technically, the method is feasible, but the social demand of the ferrous sulfate is not large, and the ferrous sulfate is not easy to sell except in individual areas, so the method cannot be popularized widely.

And (IV) reacting with the ground phosphate rock to produce the phosphate fertilizer. Theoretical and practical results have long proved that the quality of the phosphate fertilizer prepared by the method is poor and is unfavorable for agriculture.

And (V) reacting with ammonia water, and then producing ammonium sulfate through the processes of air oxidation, filtration, concentration, crystallization separation and the like. The method has long production period, low work efficiency, high energy consumption and low cost, and people are generally reluctant to adopt the method.

In general, the above five approaches have significant drawbacks (or limitations).

The invention aims to provide a novel process method, thereby achieving two purposes: (1) all the components in the waste acid liquid are fully utilized, so that the pollution of the components to the environment is thoroughly eliminated; (2) the potassium sulfate, compound fertilizer, ferrous carbonate and other products which are needed by the society are produced in large quantity, so that the social needs can be met, and the production cost of the products is lower (compared with the conventional production method), thereby enhancing the economic benefit of enterprises. In addition, the potassium sulfate is an agricultural chemical product which needs to be imported in large quantity in China, potassium sulfate production plants are built in many places in China at present, and the process method provided by the invention has a certain reference function on the plants.

The process method can be implemented by using conventional chemical equipment and means, and has no difficulty in operation in each step. The specific implementation method is as follows:

(1) the waste acid liquid is taken out and put into an enamel reaction kettle, and strong ammonia water (with the concentration of about 20 percent) is gradually added under stirring for neutralization until the PH value is 4.5. In the process, the temperature of the material can rise automatically (from room temperature to about 75-80 ℃), and polypropylene rubber or wood boards are used for heatAnd filtering and separating by using a frame filter. The filter cake is a hydrate of titanium, aluminum, chromium, barium, etc., and can be used in combination by a known method, and the filtrate is (NH)₄)₂SO₄And FeSO₄The aqueous solution of (a), which usually also contains MgSO₄MnSO4, phosphate, and the like. The contents of the three components are completely determined by the properties and the compositions of ilmenite used in the production of titanium dioxide plantsRegardless of the method of operation of the present invention. Generally speaking, MnSO₂And phosphate, but MgSO₂The content of (A) varies widely, sometimes less than 2 g/l, sometimes up to more than 30 g/l. It is to be expressly understood that the presence of these three substances is not detrimental to the practice and effectiveness of the present invention.

(2) The filtrate obtained in the previous step is the starting material of the operation in the step, potassium chloride is added for double decomposition reaction after concentration, and potassium sulfate is generated according to the following formula:

(MgSO when MgSO is present in solution₄And MnSO₂Similar metathesis reactions can also occur or be promoted).

The operation method comprises the following steps: transferring the filtrate into enamel pot, heating, evaporating, concentrating (preferably under reduced pressure for improving work efficiency), and stopping concentrating when total sulfate concentration reaches 3M (i.e. 3 mol/L). When the temperature of the materials is 60-70 ℃, potassium chloride is added under sufficient and effective stirring (the rotating speed is 80-100 r/m), and the adding amount of the potassium chloride is theoretical amount. After the addition, stirring is continued, the jacket is opened to cool water at the same time, when the temperature of the materials is reduced to about 30 ℃, the materials are discharged, filtered, pumped and dried, and then are uniformly pumped and washed by proper amount of clear water, and finally, a centrifuge is used for fully spin-drying the materials. The dried product is the agricultural potassium sulfate. The specification of the product is as follows: containing potassium oxide (K)₂O) is more than or equal to 42 percent, nitrogen (N) is 2 to 2.5 percent, iron (Fe) is 0.8 to 1.0 percent, chloride (cl) is less than or equal to 1 percent, and free water is less than or equal to 5 percent. If a product with higher purity or completely dry is desired, chemical engineering can be usedThe above general means may be used to carry out the purification and drying treatment. However, the potassium sulfate for agricultural use of the above specifications is very suitable for agricultural use and does not require purification, as far as agricultural workers are concerned. As a result of the refining, the product isThe nitrogen, iron and chloride in the fertilizer are completely or mostly removed, and the nitrogen, a small amount of iron and a small amount of chloride are just substances necessary for the growth of crops.

(3) The solution after the agricultural potassium sulfate is separated contains quite a plurality of ferrous salts (FeSO)₄And FeCl₂) The concentration is generally 0.32-0.54M, and in order to properly utilize the resource, separation is needed, the invention adopts an ammonium carbonate treatment method to make ferrous salt FeCO₃The precipitated form is isolated. The reaction formula is as follows:

during this treatment, small amounts of ferric iron (from the oxidation of Fe) in the solution are also precipitated (in the form of Fe (OH))₃↓〕

The ammonium carbonate used can be agricultural ammonium bicarbonate and concentrated ammonia water as raw materials, and is prepared by the following method: 290Kg of agricultural ammonium bicarbonate is taken, 510 liters of water and 324 liters of 20 percent ammonia water are added, and the mixture is stirred until the solution is clear. The solution is (NH)₄)₂CO₃Solution, concentration about 3.45M. It is volatile and should be stored under sealed condition.

The specific operation process for separating the iron salt is as follows: concentrating the solution (including filtrate and washing liquor) into a reaction pot (enamel or resin glass fiber reinforced plastic anticorrosive single-layer reaction pot can be used), stirring, measuring total volume and Fe concentration, slowly adding ammonium carbonate solution (5% more than theoretical amount) under stirring, stirring for 10-15 min, discharging, suction filtering, and uniformly pumping and drying appropriate amount of water. The precipitate is ferrous carbonate, and the yield is about 90% of the theoretical amount.

Ferrous carbonate is a raw material for producing red iron oxide or other iron-containing compounds.

(4) The solution after separating ferrous carbonate is a solution containingThere is a mixture of a plurality of chemical fertilizers,roughly a composition of (NH)₄)₂SO₄50 g/l, NH₄Cl190 g/l, KCl110 g/l, FeSO₄5-6 g/L, small amount of MgSO₄Trace amount of MgSO₄And trace amounts of phosphate. Because the components are known quick-acting fertilizers and have high concentration, the fertilizer is actually a liquid compound fertilizer and can be directly popularized and used. In addition, it can also be made into solid compound fertilizer by the processes of concentration, crystallization and drying. The product can be used as a commercial fertilizer for direct sale, and can also be made into granular multielement compound fertilizer with wider application by a phosphorization and granulation process.

The present invention utilizes the waste acid liquid from titanium white powder plant to produce potassium sulfate, ferrous carbonate and compound fertilizer. Meanwhile, the pollution of three wastes to the environment is completely eliminated, and considerable economic and social benefits are achieved.

The invention relates to a specific implementation method. The exact data on inputs and outputs depend on the specific composition of the spent acid solution, which is explained in detail in the examples:

example a certain waste acid solution (obtained from wuhan titanium dioxide works at 5 months and 18 days 95 years) has the following properties and components: dark yellow clear liquid with specific gravity of 1.233, containing effective acid (as H)₂SO₄Calculated) 17.5%, FeSO₄5.6% of total titanium (in terms of TiO)₂Calculated) 0.45 percent. 10 liters of the waste acid liquor is taken and operated according to the process method provided by the invention. The operation conditions and specific data of each step are as follows:

(1) adding 10L of waste acid solution into enamel barrel, gradually adding 20% ammonia water under stirring until pH is 4.5 (total adding 3.8Kg), heating at 75 deg.C, filtering with polyester cloth (natural filtering, and squeezing to obtain 12.3L of filtrate containing (NH)₄)₂SO₄1.56M，FeSO₄0.32M，MgSO₄0.02M，MnSO₄0.01M phosphate: trace.

(2) Placing theabove filtrate (all)) Boiling and concentrating in an enamel barrel until the volume is 7.8L (the total sulfate concentration is 3.01M), stopping heating, adding 3.68Kg of 95% potassium chloride under stirring when the temperature of the material is reduced to 70 ℃, continuing stirring and reducing the temperature by using a cold water bath after adding, discharging and draining when the temperature of the material is reduced to 28 ℃, uniformly pumping and washing by cold water for multiple times (the total cold water is 1.1L), and finally drying by using a centrifuge. 3.70kg of a drying product (namely the agricultural potassium sulfate) is obtained, and the test result is as follows: potassium oxide (K)₂O) 42.1%, N2.2%, Fe 0.95%, and Cl 0.80%.

(3) Collecting the filtrate and washing liquid obtained from the above operation in an enamel barrel, stirring to obtain a total volume of 8.7L, and slowly adding 3.45M (NH) containing Fe0.37M under stirring₄)₂CO₃0.98L (105% of theory) is added, the mixture is stirred for 12 minutes, then is filtered, and is washed by 0.4L of water and is dried to obtain 0.86Kg of dried product, and the dried product is 0.35 Kg.

(4) The filtrate and washing liquor after ferric salt precipitation are separated out and are 8.5 liters in total, and are stirred uniformly, and the main components are as follows: (NH)₄)₂SO₄51.6 gram liter, (NH)₄)₂SO₄189 g/l, KCl111.3 g/l, FeSO₄5.4 g/l.

The liquid is concentrated, crystallized and dried to obtain solid matter with total weight of 3.4Kg and fertilizer components including nitrogen (N) 15.1% and potassium oxide (K)₂O)17.5 percent and iron (Fe)0.50 percent.

The nature and composition of the acid liquor used in this example are very generally representative, and it can be seen thatthe material data using the process of the invention is roughly as follows (in terms of 1000 litres of acid liquor): adding ammonia (according to 100% NH)₃76Kg, 368Kg of potassium chloride (95%), 32.5Kg of ammonium carbonate (100%), 370Kg of potassium sulfate for agricultural use,340Kg of compound fertilizer and 35Kg of ferrous carbonate.

Claims

1. A method for producing potassium sulfate and compound fertilizer by using waste acid liquor of a powdery iron oxide factory is characterized by comprising the following steps: the waste acid liquor is used as basic raw material, and through the processes of adding ammonia to make neutralization, filtering, adding potassium chloride to make double decomposition, separation and drying so as to obtain potassium sulfate, and the separated solution is passed through the processes of separating iron salt to obtain the invented compound fertilizer.

2. The method for producing potassium sulfate, ferrous carbonate and compound fertilizer by using the waste acid liquor of the titanium dioxide factory as claimed in claim 1, which is characterized in that: the method for separating iron salt adopts ammonium carbonate treatment method to make ferrous salt use FeCO₃Is precipitated and is filtered and separated to obtain ferrous carbonate and compound fertilizer.