A method for preparing desulfurizing agent using chemical sludge from papermaking wastewater plant

Abstract

The invention discloses a method for preparing a desulfurizer by utilizing chemical sludge from a papermaking wastewater plant. The method comprises four steps of drying the chemical sludge, heating the chemical sludge by using heat generated by burning biological sludge, high-temperature treating the generated solid, and preparing a columnar dry desulfurizer. With a special processing device, the invention can convert the iron element in the chemical sludge from the papermaking wastewater plant into ferric oxide, making it a high-quality raw material for preparing a biogas dry desulfurizer, thereby eliminating the secondary pollution of the sludge and realizing the recycling of waste resources.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste recycling, and in particular relates to a method for preparing a desulfurizing agent by utilizing chemical sludge from a papermaking wastewater plant. Background Art

[0002] In newsprint mills, wastewater generated after deinking of waste paper is mainly treated through sedimentation tanks, anaerobic treatment, aerobic treatment, Fenton advanced oxidation treatment and other processes. The sludge after the aerobic treatment process is called biological sludge. Because of its high fiber content and calorific value of more than 3,000 calories, it can be directly burned in an incinerator; and the sludge after Fenton advanced oxidation treatment is called chemical sludge. After this process, most of the various organic substances in the sewage are oxidized by Fenton reagents, and the remaining sludge contains less organic matter, and the calorific value is low and cannot be burned. Landfilling will cause pollution to the environment. According to analysis, the dryness of the chemical sludge is 45-50%, the organic content is 30-40%, and the content of the remaining inorganic matter is about 60-70%. Scanning electron microscope-energy spectrometer analysis test of inorganic matter shows that the main elements are Si, Fe, and Al, and the Fe element has the largest content. (The source of Fe element is mainly FeSO4 added in the process of Fenton advanced oxidation, the source of Si element is water glass Na2O·nSiO2 added in the process of waste paper deinking, and the source of Al element is polymerized AlCl3 added in the process of papermaking).

[0003] At present, the method for treating chemical sludge in paper mills is to mix it with sedimentation sludge and residual sludge from secondary biological treatment, add inorganic conditioning agents and polymer flocculants, and then pump the mixed sludge to a sludge dewatering machine for dehydration. The dehydrated sludge is then subjected to subsequent treatment such as incineration or landfill. However, due to the addition of a large amount of inorganic conditioning agents and polymer flocculants, this method not only increases the dosing cost of sludge treatment, but also increases the mass of sludge dehydration, increases the dehydration load, and at the same time, the recovery rate of iron in the sludge is very low, and the concept of recycling waste resources cannot be realized. Simultaneous combustion with biological sludge will produce more difficult-to-treat waste gas, which is extremely unfavorable for tail gas treatment; and biogas contains a large amount of hydrogen sulfide gas. If this part of the gas is directly burned with biogas without adsorption treatment, it will cause greater pollution to the environment. The existing desulfurization technology generally uses a desulfurizer to remove it, but the cost of the desulfurizer is high, which makes the desulfurization technology of hydrogen sulfide difficult to promote and apply. Therefore, how to obtain a more economical desulfurizer has become one of the problems to be solved in the prior art. Summary of the invention

[0004] In view of the above shortcomings, the present invention provides a method for preparing a desulfurizer from chemical sludge in a papermaking wastewater plant. The basic idea is that during the water treatment of waste paper deinking wastewater, biological sludge has a high calorific value and can be burned, while chemical sludge has a low calorific value but contains reusable iron elements. The chemical sludge formed after four-stage advanced oxidation is dried → the heat generated by burning the biological sludge is used to heat the chemical sludge → the solid generated by high-temperature treatment is used to prepare a columnar dry desulfurizer. In conjunction with a special processing device, the iron element in the chemical sludge in the papermaking wastewater plant is converted into ferric oxide, making it a high-quality raw material for preparing a biogas dry desulfurizer. Not only the secondary pollution of the sludge is eliminated, but also the recycling of waste resources is realized, thereby realizing the concept of reusing the chemical sludge discharged from the papermaking wastewater plant and recycling the waste resources.

[0005] The specific technical solution adopted by the present invention is: a method for preparing a desulfurizing agent from chemical sludge in a papermaking wastewater plant, and the specific steps are as follows:

[0006] (1) After being processed by the plate and frame filter press, the dryness of the chemical sludge is 50-60%; the dryness of the biological sludge is 55-65%. The two types of sludge are stored separately and transported to the incinerator separately;

[0007] (2) In an incinerator of a special device for preparing desulfurization agent from chemical sludge in a papermaking wastewater plant, the biological sludge is mixed with coal powder at a ratio of 10-20% by mass, and the biological sludge is burned. When the temperature in the furnace reaches above 800°C, the chemical sludge is fed in through the feed port of the screw propeller, and driven by the screw propeller, the chemical sludge enters the part of the screw propeller located in the furnace of the incinerator. By adjusting the speed of the screw propeller, the residence time of the sludge in the screw propeller in the furnace is ensured to be 10-20 minutes; in the high-temperature furnace, the organic matter in the chemical sludge is completely oxidized and decomposed, and the hydrated iron ions are oxidized into active iron oxide, which enters the silo through the discharge port, and enters the discharge silo through the discharge port under the action of the screw propeller, and becomes the main active raw material for preparing the desulfurization agent after cooling;

[0008] (3) Add 5-10 parts of active zinc oxide as an auxiliary agent, 20-30 parts of calcium oxide as a binder, 10-20 parts of ammonium bicarbonate as a pore-forming agent, and 20-30 parts of water to 100 parts of the above-mentioned activated iron oxide cooled to room temperature, stir and mix evenly, and extrude it through a screw extruder to form a columnar iron oxide desulfurizer.

[0009] The various additives added in the above step (3) include active zinc oxide as an auxiliary agent to improve its adsorption; the added calcium oxide turns into calcium hydroxide paste when in contact with water, which, on the one hand, plays a bonding role; on the other hand, the substance is alkaline and can improve the adsorption of hydrogen sulfide in biogas; and the added ammonium bicarbonate is easy to decompose and produce gas, which can form a large number of pores inside the desulfurizer during the preparation process, increase the specific surface area, and improve the adsorption rate of hydrogen sulfide. By controlling the dosage of the above various substances within the above range, they can be better coordinated with the activated iron oxide prepared by itself, achieve the effect of waste utilization, and have a better effect on the adsorption of hydrogen sulfide.

[0010] Furthermore, in the step (3), 8 parts of active zinc oxide auxiliary agent, 25 parts of calcium oxide as a binder, and 15 parts of ammonium bicarbonate pore-forming agent are added. With the above dosage, the desulfurizer finally obtained has the best desulfurization effect.

[0011] The above-mentioned papermaking wastewater plant chemical sludge preparation desulfurization agent special device has the following specific structure:

[0012] The device comprises an incinerator, wherein a screw propeller penetrating the furnace is arranged above the furnace of the incinerator, and the feed port and propulsion motor of the screw propeller are both located outside the furnace; the discharge port of the screw propeller is located on the other side of the furnace, and the discharge port is directly connected to the discharge bin through a discharge bin pipeline; an air outlet is also arranged above the discharge port of the screw propeller, and the air outlet is connected to an exhaust gas treatment device through an air guide pipeline;

[0013] In addition to the activated iron oxide prepared as described above, the use of the above-mentioned process and equipment also has the following advantages: the waste gas generated by the chemical sludge during the heating process is discharged separately through the air outlet of the screw propeller and enters the corresponding tail gas treatment device for treatment; since the chemical sludge does not undergo the combustion process, but only undergoes the high-temperature reaction process, it does not produce waste gas that would only be produced by combustion, which facilitates subsequent treatment. At the same time, since it is not treated together with the biological sludge, it avoids the secondary reaction of the two to produce more waste, and also avoids a series of problems such as gas treatment difficulties caused by the mixed treatment of the waste gases treated by the two.

[0014] In summary, the above-mentioned process method, in conjunction with a dedicated treatment device, can convert the iron element in the chemical sludge of the papermaking wastewater plant into ferric oxide, making it a high-quality raw material for preparing a biogas dry desulfurizer. This not only eliminates the secondary pollution of the sludge, but also realizes the recycling of waste resources, thereby realizing the reuse of chemical sludge discharged from the papermaking wastewater plant and the concept of waste resource recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic structural diagram of the device for preparing a desulfurizing agent from chemical sludge in a papermaking wastewater plant;

[0016] In the figure: 1 is a propulsion motor, 2 is a screw propeller, 3 is a propulsion screw, 4 is an incinerator, 5 is a discharge bin, 6 is a discharge bin pipeline, 7 is an exhaust gas treatment device, 8 is an air guide pipeline, 9 is an air outlet, and 10 is a feed inlet. DETAILED DESCRIPTION

[0017] Example 1

[0018] A method for preparing a desulfurizing agent from chemical sludge in a papermaking wastewater plant, the specific steps are as follows:

[0019] (1) After being processed by the plate and frame filter press, the dryness of the chemical sludge is 50%; the dryness of the biological sludge is 55%. The two types of sludge are stored separately and transported to the incinerator separately;

[0020] (2) In the incinerator of the special device for preparing desulfurization agent from chemical sludge of papermaking wastewater plant, the biological sludge is mixed with coal powder at a ratio of 20% by mass, and the biological sludge is burned. When the temperature in the furnace reaches above 800°C, the chemical sludge is fed in through the feed port of the screw propeller, and driven by the screw propeller, it enters the part of the screw propeller located in the furnace of the incinerator. By adjusting the speed of the screw propeller, the residence time of the sludge in the screw propeller in the furnace is ensured to be 20 minutes; in the high-temperature furnace, the organic matter in the chemical sludge is completely oxidized and decomposed, and the hydrated iron ions are oxidized into active iron oxide, which enters the silo through the discharge port, and enters the discharge silo through the discharge port under the action of the screw propeller, and becomes the main active raw material for preparing the desulfurization agent after cooling;

[0021] (3) Add 5 parts of active zinc oxide as an auxiliary agent, 20 parts of calcium oxide as a binder, 10 parts of ammonium bicarbonate as a pore-forming agent, and 20 parts of water to 100 parts of the above-mentioned activated iron oxide cooled to room temperature, stir and mix evenly, and extrude it through a screw extruder to form a columnar iron oxide desulfurizer.

[0022] The desulfurizer obtained above was used to remove hydrogen sulfide in biogas (the removal method was the dry desulfurization technology in the prior art, the desulfurizer was filled in the dry desulfurization tower, and the dosage can refer to the prior art). At the same time, the inventor used a conventional desulfurizer for a control test, and the results are as follows:

[0023] Main component content Before desulfurization After desulfurization (existing technology) After desulfurization (the present invention) Target value <![CDATA[CH4]]> 70％ 98.5％ 98.9％ ≥97％ <![CDATA[H2S]]> 4％ <![CDATA[4.6mg / m 3 ]]> <![CDATA[2.2mg / m 3 ]]> <![CDATA[≤8mg / m 3 ]]> Removal rate (%) 99.992 99.996

[0024] It can be seen that the desulfurization effect of the desulfurization agent provided by the present invention is basically the same as that of the prior art or even slightly improved. At the same time, the desulfurization agent provided by the present invention is prepared from waste such as chemical sludge, which has better environmental protection and social benefits.

[0025] Example 2

[0026] A method for preparing a desulfurizing agent from chemical sludge in a papermaking wastewater plant, the specific steps are as follows:

[0027] (1) After being processed by the plate and frame filter press, the dryness of the chemical sludge is 60%; the dryness of the biological sludge is 65%. The two types of sludge are stored separately and transported to the incinerator separately;

[0028] (2) In the incinerator of the special device for preparing desulfurization agent from chemical sludge of the papermaking wastewater plant, the biological sludge is mixed with coal powder at a ratio of 10% by mass, and the biological sludge is burned. When the temperature in the furnace reaches above 800°C, the chemical sludge is fed in through the feed port of the screw propeller, and driven by the screw propeller, it enters the part of the screw propeller located in the furnace of the incinerator. By adjusting the speed of the screw propeller, the residence time of the sludge in the screw propeller in the furnace is ensured to be 15 minutes; in the high-temperature furnace, the organic matter in the chemical sludge is completely oxidized and decomposed, and the hydrated iron ions are oxidized into active iron oxide, which enters the silo through the discharge port, and enters the discharge silo through the discharge port under the action of the screw propeller, and becomes the main active raw material for preparing the desulfurization agent after cooling;

[0029] (3) Add 100 parts of the above-mentioned activated iron oxide cooled to room temperature, 10 parts of activated zinc oxide as an auxiliary agent, 30 parts of calcium oxide as a binder, 20 parts of ammonium bicarbonate as a pore-forming agent, and 30 parts of water, stir and mix evenly, and extrude through a screw extruder to form a columnar iron oxide desulfurizer.

[0030] The desulfurizer obtained above was used to remove hydrogen sulfide in biogas (the removal method was the dry desulfurization technology in the prior art, the desulfurizer was filled in the dry desulfurization tower, and the dosage can refer to the prior art). At the same time, the inventor used a conventional desulfurizer for a control test, and the results are as follows:

[0031] Main component content Before desulfurization After desulfurization (existing technology) After desulfurization (the present invention) Target value <![CDATA[CH4]]> 70％ 98.1％ 98.8％ ≥97％ <![CDATA[H2S]]> 4％ <![CDATA[5.6mg / m 3 ]]> <![CDATA[2.2mg / m 3 ]]> <![CDATA[≤8mg / m 3 ]]> Removal rate (%) 99.990 99.995

[0032] It can be seen that the desulfurization effect of the desulfurization agent provided by the present invention is basically the same as that of the prior art or even slightly improved. At the same time, the desulfurization agent provided by the present invention is prepared from waste such as chemical sludge, which has better environmental protection and social benefits.

[0033] Example 3

[0034] A special device for preparing a desulfurizer from chemical sludge in a papermaking wastewater plant comprises an incinerator 4, wherein a screw propeller 2 penetrating the furnace is arranged above the furnace of the incinerator 4; the discharge port of the screw propeller 2 is located on the other side of the furnace, and is directly connected to a discharge bin 5 through a discharge bin pipe 6; an air outlet 9 is also arranged above the discharge port of the screw propeller 2, and the air outlet 9 is connected to an exhaust gas treatment device 7 through an air guide pipe 8; the feed port 10 of the screw propeller 2 and the propulsion motor 1 are both located outside the furnace.

Claims

1. A method for preparing a desulfurizing agent using chemical sludge from a papermaking wastewater plant, characterized in that: The specific steps are as follows: (1) After being processed by the plate and frame filter press, the dryness of the chemical sludge is 50-60%; the dryness of the biological sludge is 55-65%. The two types of sludge are stored separately and transported to the incinerator separately; (2) In the incinerator of the special device for preparing desulfurization agent from chemical sludge in the papermaking wastewater plant, the biological sludge is mixed with coal powder at a ratio of 10-20% by mass, and the biological sludge is burned. When the temperature in the furnace reaches above 800°C, the chemical sludge is fed in from the feed port of the screw propeller, and driven by the screw propeller, it enters the part of the screw propeller located in the furnace of the incinerator, ensuring that the sludge stays in the screw propeller in the furnace for 10-20 minutes; in the high-temperature furnace, the organic matter in the chemical sludge is completely oxidized and decomposed, and the hydrated iron ions are oxidized into active iron oxide, which enters the silo through the discharge port, and enters the discharge silo through the discharge port under the action of the screw propeller, and becomes the main active raw material for preparing the desulfurization agent after cooling; A screw propeller (2) penetrating the furnace is arranged above the furnace of the incinerator (4); the discharge port of the screw propeller (2) is located on the other side of the furnace and is directly connected to the discharge bin (5) via a discharge bin pipeline (6); an air outlet (9) is also arranged above the discharge port of the screw propeller (2), and the air outlet (9) is connected to an exhaust gas treatment device (7) via an air guide pipeline (8); the feed port (10) of the screw propeller (2) and the propulsion motor (1) are both located outside the furnace; (3) Add 5-10 parts of active zinc oxide as an auxiliary agent, 20-30 parts of calcium oxide as a binder, 10-20 parts of ammonium bicarbonate as a pore-forming agent, and 20-30 parts of water to 100 parts of the above-mentioned activated iron oxide cooled to room temperature, stir and mix evenly, and extrude it through a screw extruder to form a columnar iron oxide desulfurizer.

2. The method for preparing a desulfurizing agent using chemical sludge from a papermaking wastewater plant according to claim 1, characterized in that: In the step (3), 8 parts of active zinc oxide auxiliary agent, 25 parts of calcium oxide as a binder, and 15 parts of ammonium bicarbonate pore-forming agent are added.

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