A flue gas dry desulfurization agent and preparation method thereof

Abstract

The invention discloses a flue gas dry desulfurizer and a preparation method thereof, which relates to the technical field of flue gas purification, and comprises: 80% to 92% slaked lime powder, 5% to 15% expansion agent, 2% to 5% dispersant powder, and 0.5% to 2% free water, wherein the slaked lime powder is prepared by adding water to quicklime powder and slaking, the expansion agent comprises organic salt and inorganic salt, and the dispersant comprises talcum powder. Firstly, quicklime powder and expansion agent powder are mixed, and then mixed with slaking water for slaking, and then dried at low temperature after slaking, and then ground, and then mixed with dispersant powder after grinding to obtain a flue gas desulfurizer. In addition to achieving the desulfurization index, the operating cost of the desulfurizer can be greatly reduced, and the desulfurization products are calcium sulfate and calcium sulfite, which can be used as raw materials for cement plants.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas purification, in particular to a flue gas dry desulfurization agent and a preparation method thereof. Background Art

[0002] Flue gas desulfurization is divided into three categories: wet, semi-dry and dry desulfurization processes. The specific desulfurization process to be adopted needs to be selected according to the actual situation. Among them, SDS (the desulfurizer is sodium bicarbonate powder) dry desulfurization is one of the dry desulfurization processes. It has the advantages of high desulfurization efficiency, less equipment, stable operation of the device, low power consumption, and the flue gas temperature remains basically unchanged after purification, and there is no problem of wet flue gas desulfurization. It is often used in the flue gas purification process for treating low-concentration sulfur dioxide, such as steel mills, sintering plants, and coking plants. This desulfurization process is often used. However, the SDS dry desulfurization process also has disadvantages, such as the high market price of sodium bicarbonate and the high desulfurization operation cost; the desulfurization product sulfate sulfite is difficult to handle.

[0003] In order to reduce operating costs, some companies have also tested using Ca(OH)2 powder or activated Ca(OH)2 powder as a desulfurizer in SDS devices. The tests showed that although Ca(OH)2 powder can remove part of the sulfur dioxide, its desulfurization efficiency is low and cannot meet the emission index requirements. It is necessary to adjust the SDS equipment parameters and the powder dosage to achieve the emission index.

[0004] Therefore, it is imperative to find alternative high-efficiency desulfurizers and solve the difficulties in desulfurization ash disposal. Summary of the invention

[0005] The present invention aims at the above-mentioned technical problems, overcomes the shortcomings of the prior art, and provides a flue gas dry desulfurization agent, comprising: 80% to 92% slaked lime powder, 5% to 15% expander, 2% to 5% dispersant powder, and 0.5% to 2% free water, wherein the slaked lime powder is produced by slaking quicklime powder with water, the expander comprises at least one of an organic salt and an inorganic salt, and the dispersant comprises talcum powder.

[0006] The technical solution further defined in the present invention is:

[0007] The aforementioned flue gas dry desulfurization agent, quicklime powder, expansion agent powder, and dispersant powder have a particle size of more than 325 meshes.

[0008] In the aforementioned flue gas dry desulfurization agent, the expansion agent includes one or more of sodium silicate, sodium sulfate, calcium nitrate, aluminum sulfate, sodium acetate, calcium acetate, magnesium acetate, calcium citrate, and urea.

[0009] Another object of the present invention is to provide a method for preparing a flue gas dry desulfurizer, which comprises the following steps: firstly, quicklime powder and expansion agent powder are mixed, and then mixed with water and matured. During the maturation, the expansion agent does not react with water, but calcium oxide reacts with water. After maturation, newly generated calcium hydroxide adheres to the surface of the expansion agent; after maturation, the calcium hydroxide is dried at a low temperature, and the drying temperature is 60 to 120°C; the dried desulfurizer is then finely ground into fine powder, and the fine powder is mixed with dispersant powder to obtain a flue gas desulfurizer.

[0010] The aforementioned flue gas dry desulfurization agent and preparation method thereof selects a suitable drying temperature according to different expansion agents.

[0011] The above-mentioned flue gas dry desulfurizer and its preparation method, the dried desulfurizer is finely ground into a particle size of more than 325 meshes.

[0012] The above-mentioned flue gas dry desulfurizer and its preparation method, the dried desulfurizer is finely ground into a particle size of more than 525 meshes.

[0013] The beneficial effects of the present invention are: in addition to achieving the desulfurization index, the desulfurization agent can greatly reduce the operating cost of the desulfurization agent, and the desulfurization products are calcium sulfate and calcium sulfite which can be used as raw materials for cement plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0015] This embodiment provides a method for preparing a flue gas dry desulfurization agent according to the following formula:

[0016] Formula 1: 82% slaked lime powder, 15% expander, 2% dispersant powder, 1% free water. This formula is suitable for flue gas desulfurization with a flue gas temperature above 120°C.

[0017] Formula 2: 87% slaked lime powder, 10% expander, 1.5% dispersant powder, 1.5% free water. This formula is suitable for flue gas desulfurization with a flue gas temperature above 150°C.

[0018] Formula 3: 90% slaked lime powder, 7% expander, 2% dispersant powder, 1% free water. This formula is suitable for flue gas desulfurization with a flue gas temperature above 180°C.

[0019] First, quicklime powder and expansion agent powder are mixed, and then mixed with water for aging. During aging, the expansion agent does not react with water, but calcium oxide reacts with water. After aging, newly generated calcium hydroxide adheres to the surface of the expansion agent. After aging, the calcium hydroxide is dried at a low temperature of 60 to 120°C. The dried desulfurizer is then finely ground into fine powder with a particle size of more than 325 meshes, and the fine powder is mixed with dispersant powder to obtain a flue gas desulfurizer.

[0020] Desulfurization principle: After the desulfurizer powder is sprayed into the flue, the expansion agent quickly decomposes at high temperature to produce gas and expand the desulfurizer. The particle size of the desulfurizer powder on the surface of the expansion agent becomes finer to form submicron calcium hydroxide powder. The calcium hydroxide powder is in full contact with sulfur dioxide in the flue gas to achieve the purpose of efficient desulfurization.

[0021] The test was conducted on a 200t / h gas boiler in a steel plant. The boiler used blast furnace gas and coke oven gas as fuel, adopted SDS desulfurization, and was equipped with a bag filter at the rear end. The desulfurizer of the present invention was used to directly replace baking soda using the existing SDS desulfurization device, achieving the expected effect. The specific flue gas parameters are as follows:

[0022] project unit parameter Remark Boiler size 200t / h Rated operating conditions Furnace type Gas boiler fuel Blast furnace gas, coke oven gas Smoke volume (maximum) <![CDATA[Nm 3 / h]]> 290000 Rated operating conditions Exhaust temperature ℃ 140 Rated operating conditions <![CDATA[Initial concentration of SO2]]> <![CDATA[mg / m 3 ]]> ≤200 Rated operating conditions Oxygen content % ≤3

[0023] After the desulfurizer of the present invention is added, the flue gas parameters are as follows:

[0024] project unit parameter Remark Actual operating flue gas volume <![CDATA[Nm 3 / h]]> 278000 Actual exhaust temperature ℃ 112 Actual flue gas oxygen content % 2.8 <![CDATA[Inlet SO2 concentration]]> <![CDATA[mg / m 3 ]]> 130-150 <![CDATA[Outlet SO2 concentration (average value)]]> <![CDATA[mg / m 3 ]]> 27 8 hours operation <![CDATA[Outlet SO2 concentration (minimum value)]]> <![CDATA[mg / m 3 ]]> 12 Desulfurization agent consumption (average value) Kg / h 200 Desulfurization efficiency % ＞90% Expected Results achieve

[0025] It can be seen that the desulfurizer of the present invention can achieve a higher desulfurization efficiency, and the average SO2 emission concentration can also be guaranteed to be stable below 30 mg / Nm³, and the expected effect is obvious.

[0026] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A flue gas dry desulfurization agent, characterized in that: include: 80% to 92% slaked lime powder, 5% to 15% expander, 2% to 5% dispersant powder, and 0.5% to 2% free water, wherein the slaked lime powder is prepared by adding water to quicklime powder and slaking, the expander includes at least one of an organic salt or an inorganic salt, and the dispersant includes talcum powder; The preparation method of the flue gas dry desulfurizer comprises the following steps: firstly, quicklime powder and expansion agent powder are mixed, and then mixed with water for aging; during aging, the expansion agent does not react with water, but calcium oxide reacts with water, and newly generated calcium hydroxide is attached to the surface of the expansion agent after aging; the aging calcium hydroxide is dried at a low temperature, and the drying temperature is 60-120° C.; the dried desulfurizer is then finely ground into fine powder, and the fine powder is mixed with dispersant powder to obtain the flue gas desulfurizer; The quicklime powder, expander powder and dispersant powder have a particle size of more than 325 meshes.

2. A flue gas dry desulfurization agent according to claim 1, characterized in that: The expansion agent includes one or more of sodium silicate, sodium sulfate, calcium nitrate, aluminum sulfate, sodium acetate, calcium acetate, magnesium acetate, calcium citrate and urea.

3. A flue gas dry desulfurization agent according to claim 1, characterized in that: Different drying temperatures are selected according to different expanders.

4. A flue gas dry desulfurization agent according to claim 1, characterized in that: The dried desulfurizer is finely ground into a particle size of more than 325 mesh.

5. A flue gas dry desulfurization agent according to claim 4, characterized in that: The dried desulfurizer is finely ground into a particle size of more than 525 mesh.

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