Method for resource utilization of gasification slag

Abstract

The application provides a method for gasification slag resource utilization, and belongs to the technical field of coal chemical industry. The gasification slag is mixed with a flocculating agent aqueous solution, the obtained mixture is subjected to pressure filtration by using an ultrahigh pressure filter, and a gasification slag filter cake is obtained; the water content of the gasification slag filter cake is below 35%; and the gasification slag filter cake is used to replace part of fuel coal for combustion. By using the ultrahigh pressure filtration and cooperating with the use of the flocculating agent, the water content of the gasification slag can be reduced to below 35%, the heat value of the gasification slag filter cake after pressure filtration is above 3300kcal / kg, the gasification slag filter cake can be used to replace part of fuel coal, and the resource utilization of the gasification slag is realized. The application has good environmental and social benefits, solves the environmental protection problems caused by the high water content of the gasification slag, the transportation pollution of the gasification slag during external transportation and the transfer of the chemical solid waste, achieves the purpose of standard discharge of the gasification slag, and improves the comprehensive utilization value of resources.

Description

Technical Field

[0001] This invention relates to the field of coal chemical technology, and in particular to a method for the resource utilization of gasification slag. Background Technology

[0002] With my country's rapid economic development, environmental pollution has become increasingly serious. Gasification slag is a product of the crude syngas filtered and washed from the coal gasification unit in ammonia production centers (hereinafter referred to as gasification slag). Due to its fine particle size (1-100μm), high moisture content, high viscosity, low value, and inconvenient transportation, its comprehensive utilization is quite difficult. Long-term stockpiling not only occupies a large amount of land but also seriously pollutes the environment. Currently, gasification slag faces the following problems:

[0003] (1) The high moisture content (45-55%) of gasification slag leads to a decrease in comprehensive utilization rate, and the main disposal methods are stockpiling or external sales.

[0004] (2) Gasification slag is transported by truck, which causes prominent environmental problems such as dust, black water dripping and road pollution.

[0005] (3) When the gasification slag is dehydrated to 50-55% by vacuum filter press, the gasification slag filter cake cracks and cannot be further dehydrated by vacuum filtration.

[0006] (4) If gasification residue is treated as solid waste, there is a certain risk of traceability.

[0007] (5) The gasification residue still has a certain amount of heat. When it is reduced to 35%, the heat (lower heating value) can reach 13.86 MJ / kg. Selling it externally will cause a certain waste of resources. Summary of the Invention

[0008] The purpose of this invention is to provide a method for the resource utilization of gasification slag, which not only solves the environmental problems caused by the high moisture content of gasification slag during transportation and processing, as well as the environmental problems caused by the transfer and tracing of chemical solid waste, but also achieves the goal of treating gasification slag to meet emission standards, thereby improving the comprehensive utilization value of resources.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] This invention provides a method for the resource utilization of gasification slag, comprising the following steps:

[0011] The gasification slag is mixed with a flocculant aqueous solution, and the resulting mixture is filtered using an ultra-high pressure filter press to obtain a gasification slag filter cake; the moisture content of the gasification slag filter cake is below 35%, and the calorific value is above 3300 kcal / kg;

[0012] The gasification slag filter cake is used to replace part of the fuel coal for combustion.

[0013] Preferably, the gasification slag has a moisture content of 45-55% and a particle size of 1-100 μm.

[0014] Preferably, the flocculant in the flocculant aqueous solution is polyacrylamide.

[0015] Preferably, the dry weight of the flocculant in the flocculant aqueous solution is 1-5‰ of the dry weight of the gasification slag.

[0016] Preferably, the mass concentration of the flocculant in the flocculant aqueous solution is 1-5‰.

[0017] Preferably, the flocculant aqueous solution also contains a dispersant and a carbonate.

[0018] Preferably, the dispersant comprises polyaluminum chloride; the mass of the dispersant is 1-3% of the dry weight of the gasification slag.

[0019] Preferably, the carbonate comprises sodium carbonate; the mass of the carbonate is preferably 2-3% of the dry weight of the gasification slag.

[0020] Preferably, the pressure of the filter press is above 25 MPa.

[0021] Preferably, before combustion, the gasification slag filter cake is crushed.

[0022] This invention provides a method for the resource utilization of gasification slag, comprising the following steps: mixing gasification slag with a flocculant aqueous solution; filtering the resulting mixture using an ultra-high pressure filter press to obtain a gasification slag filter cake; the moisture content of the gasification slag filter cake is below 35%; and using the gasification slag filter cake to replace part of the fuel coal for combustion. This invention, employing ultra-high pressure filtration combined with the use of a flocculant, can reduce the moisture content of the gasification slag to below 35%, and the calorific value of the filtered gasification slag filter cake is above 3300 kcal / kg, which can replace part of the fuel coal, thus realizing the resource utilization of gasification slag.

[0023] This invention has significant environmental and social benefits. It not only solves the environmental problems caused by the high moisture content of gasification slag during transportation and the source tracing of chemical solid waste transfer, but also achieves the goal of treating gasification slag to meet emission standards and improves the comprehensive utilization value of resources.

[0024] The method of this invention is highly reproducible and has significant promotional value. Attached Figure Description

[0025] Figure 1 is a flowchart of the method for resource utilization of gasification slag according to the present invention. Detailed Implementation

[0026] This invention provides a method for the resource utilization of gasification slag, comprising the following steps:

[0027] The gasification slag is mixed with a flocculant aqueous solution, and the resulting mixture is filtered using an ultra-high pressure filter press to obtain a gasification slag filter cake; the moisture content of the gasification slag filter cake is below 35%, and the calorific value is above 3300 kcal / kg;

[0028] The gasification slag filter cake is used to replace part of the fuel coal for combustion.

[0029] This invention mixes gasification slag with a flocculant aqueous solution to obtain a mixture.

[0030] In this invention, the gasification slag is preferably the product after filtration and washing of crude syngas from a coal gasification unit in a synthetic ammonia manufacturing center. In this invention, the particle size of the gasification slag is preferably 1–100 μm, and the moisture content is preferably 45–55%. The gasification slag used in this embodiment of the invention has the following properties: ash content 39.06%, volatile matter 1.76%, calorific value (as received) 9.95 MJ, total sulfur (dry basis) 1.31%, fixed carbon 59.18%, moisture 46.2%, deformation temperature 1127℃, softening temperature 1186℃, flow temperature 1263℃, silicon dioxide 51.34%, calcium oxide 3.97%, magnesium oxide 0.53%, aluminum oxide 20.66%, ferric oxide 16.61%, potassium oxide 2.47%, sodium oxide 0.18%, titanium oxide 2.18%, phosphorus pentoxide 0.26%, and sulfur trioxide 0.33%.

[0031] In this invention, the flocculant in the flocculant aqueous solution is preferably polyacrylamide (PAM). The mass concentration of the flocculant in the flocculant aqueous solution is preferably 1-5‰, more preferably 2-4‰. If the flocculant dosage is less than 1‰, the lower concentration of the flocculant aqueous solution will increase the dosage, leading to increased pressing and dehydration time and water consumption, resulting in waste. If the dosage is greater than 5‰, a saturated solution will form at room temperature, resulting in some flocculant powder remaining undissolved and wasted. Simultaneously, the increased viscosity will increase the load on the mixer and conveying pump, potentially causing the conveying pump to become clogged and run dry.

[0032] In this invention, the flocculant aqueous solution preferably also includes a dispersant and a carbonate. In this invention, the dispersant is preferably polyaluminum chloride (PAC). In this invention, after adding the flocculant (PAM) solution, the long molecular chain characteristics of the flocculant cause the loose, fine coal slime particles to quickly form large flocs with a diameter of 1-2 cm. This increased mass leads to rapid settling under gravity, preventing suspension. This state is detrimental to pressing and dewatering. The addition of a dispersant in this invention can decompose these large flocs into smaller flocs with a diameter of 0.2-0.5 cm, suspending them. In this invention, the amount of dispersant added is preferably 1-3% of the dry weight of the gasification slag.

[0033] In this invention, the carbonate is preferably sodium carbonate; the dosage of the carbonate is preferably 2-3‰ of the dry weight of the gasification slag. The main function of the carbonate in this invention is to control the pH value of the gasification slag mixture between 7 and 8, preventing equipment corrosion and shortening its service life; secondly, it increases the activity of the mixture, breaking down the small amount of coal tar contained in the gasification slag, preventing it from sticking to the filter cloth and affecting the permeability of the filter cloth.

[0034] In this invention, the dry weight of the flocculant in the flocculant aqueous solution is preferably 1-5‰ of the dry weight of the gasification slag. When the suspended solids content in the gasification slag is high (mass concentration > 30%), the mass of the flocculant is preferably 3-5‰ of the mass of the gasification slag. In this invention, the function of the flocculant is to allow the suspended solids in the gasification slag to form a better colloid, facilitating high-pressure filtration, improving the filtration effect, and reducing moisture content.

[0035] In actual industrial operation, the preferred method for preparing the flocculant aqueous solution is to add the flocculant to the flocculant aqueous solution preparation device by manual feeding, add fresh water from the outer pipe, and start stirring to mix the materials evenly to obtain the flocculant aqueous solution.

[0036] In actual industrial operation, the mixing of gasification slag and flocculant aqueous solution preferably includes: conveying the gasification slag slurry to the buffer conditioning tank through a slurry pump; conveying the flocculant aqueous solution to the buffer conditioning tank; and after the conveying is completed, turning on the agitator of the buffer conditioning tank.

[0037] When the gasification slag is transported to the buffer conditioning tank, the present invention opens the flushing water valve as needed, and the flushing water from the outer pipe flushes the gasification slag transport pipeline and enters the buffer conditioning tank to prevent the gasification slag transport pipeline from becoming blocked.

[0038] After obtaining the mixture, the present invention uses an ultra-high pressure filter press to filter the mixture to obtain gasification slag filter cake.

[0039] This invention preferably employs a plunger pump to deliver the mixture to an ultra-high pressure filter press. The flow rate of the plunger pump is measured and controlled by a flow meter. In this invention, a material return pipeline is preferably installed at the outlet of the plunger pump, through which the material returns to a buffer conditioning tank to facilitate pressure adjustment and prevent overpressure when the mixture particles are large and the concentration is high.

[0040] In this invention, the pressure of the filter press is preferably 25 MPa or higher. The feed pressure is preferably 1.5 to 3 MPa.

[0041] In this invention, the compressed air used for the overpressure is preferably supplied by a compressed air buffer tank.

[0042] After pressure filtration, the present invention yields gasification slag filter cake and filtrate.

[0043] In this invention, the moisture content of the gasification slag filter cake is below 35%, and the calorific value is above 3300 kcal / kg, which can replace part of the fuel coal for combustion.

[0044] Before combustion, the present invention preferably further includes crushing the gasification slag filter cake. The present invention does not have special requirements for the crushing process; a crushing process well-known in the art can be used. Preferably, the gasification slag filter cake is fed into a screw conveyor and crushed during the conveying process. The crushed material then reaches a metering belt and is conveyed by the belt to raw material silo #1.

[0045] In this invention, the obtained filtrate is preferably transported to a filtrate collection tank via a pipeline. A flow meter is added to the filtrate transport pipeline to display the flow rate. After a certain amount of filtrate is collected, the filtrate pump is turned on, and part of the filtrate is transported to pipeline T1701, while the other part is transported to pipeline S1701. Under normal circumstances, the filtrate goes to pipeline T1701 for purposes such as sealing water, flushing water, and desulfurization water for the coal gasification unit. When there is too much water or the water quality is poor, the filtrate goes to pipeline S1701 for buffering.

[0046] The following detailed description of the method for resource utilization of gasification slag provided by the present invention, in conjunction with embodiments, should not be construed as limiting the scope of protection of the present invention.

[0047] Example 1

[0048] The gasification slag has a moisture content of 46.2% and a particle size of 1–100 μm.

[0049] By mass percentage, the gasification slag contains 39.06% ash, 1.76% volatile matter, 9.95 MJ calorific value (as received), 1.31% total sulfur (dry basis), 59.18% fixed carbon, 46.2% moisture, 1127℃ deformation temperature, 1186℃ softening temperature, 1263℃ flow temperature, 51.34% silicon dioxide, 3.97% calcium oxide, 0.53% magnesium oxide, 20.66% aluminum oxide, 16.61% ferric oxide, 2.47% potassium oxide, 0.18% sodium oxide, 2.18% titanium oxide, 0.26% phosphorus pentoxide, and 0.33% sulfur trioxide.

[0050] PAM flocculant was manually added to the flocculant aqueous solution preparation device, along with fresh water from the external pipe. The mixture was stirred to obtain a flocculant aqueous solution with a PAM mass concentration of 5‰ and a PAM dry weight of 2.0‰ of the dry weight of the gasification slag. The flocculant aqueous solution was then transported to a buffer conditioning tank, where PAC powder and sodium carbonate were added. The mass of PAC powder was 3% of the dry weight of the gasification slag, and the mass of sodium carbonate powder was 3‰ of the dry weight of the gasification slag. The mixture was thoroughly stirred in the buffer conditioning tank.

[0051] As shown in Figure 1, the gasification slurry is transported to the buffer conditioning tank by a slurry pump. After the transportation is completed, the agitator in the buffer conditioning tank is turned on to keep stirring, ensuring that the slurry concentration is uniform and preventing stratification and sedimentation, so as to obtain a mixture.

[0052] The mixture is pumped to a CN-UPD ultra-high pressure filter press using a plunger pump. The feed pressure is 1.5 MPa and the filter press pressure is 25 MPa. Filtration is performed to obtain gasification slag filter cake and filtrate. The gasification slag filter cake has a moisture content of 32.2% and a calorific value of 14.5 MJ / kg, which is 3465.5 kcal / kg.

[0053] The gasification slag filter cake is fed into a screw conveyor and crushed during the conveying process. The crushed material reaches the metering belt and is then conveyed to raw material #1 by a steep-angle belt and a tubular belt, which is used to replace part of the coal for subsequent combustion.

[0054] The filtrate enters the collection tank and is then transported to the S1701 pipeline.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for the resource utilization of gasification slag, characterized in that, Includes the following steps: The gasification slag is mixed with a flocculant aqueous solution, and the resulting mixture is filtered using an ultra-high pressure filter press to obtain a gasification slag filter cake; the moisture content of the gasification slag filter cake is below 35%, and the calorific value is above 3300 kcal / kg; The gasification slag filter cake is used to replace part of the fuel coal for combustion; The flocculant in the flocculant aqueous solution is polyacrylamide; The dry weight of the flocculant in the flocculant aqueous solution is 1-5‰ of the dry weight of the gasification slag; The flocculant aqueous solution also contains dispersants and carbonates; The dispersant comprises polyaluminum chloride; the mass of the dispersant is 1-3% of the dry weight of the gasification slag. The carbonate includes sodium carbonate; the mass of the carbonate is 2-3% of the dry weight of the gasification slag.

2. The method according to claim 1, characterized in that, The gasification slag has a moisture content of 45-55% and a particle size of 1-100 μm.

3. The method according to claim 1, characterized in that, The mass concentration of flocculant in the flocculant aqueous solution is 1-5‰.

4. The method according to claim 1, characterized in that, The pressure of the filter press is above 25 MPa.

5. The method according to claim 1, characterized in that, Before combustion, the gasification slag filter cake is crushed.

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