CN1113682C - Two-segment desulfurizing method for high-temp combustion - Google Patents

Abstract

The invention discloses a high-temperature combustion two-stage desulfurization method. The high-temperature combustion two-stage desulfurization method is to use wind force to blow part of the calcium-based additive powder into the furnace space, and transfer the combustion desulfurization reaction part in the coal seam of the bed-fired furnace to the combustion space and the entire flue gas flow, so as to capture the release from the coal seam to SO ₂ in the flue gas can achieve two-stage desulfurization in the bed and space; and through air distribution, the reducing atmosphere in the high-temperature combustion section and the oxidizing atmosphere in the post-combustion section can be enhanced to achieve simultaneous desulfurization and denitrification under the premise of ensuring combustion efficiency. Effect. The invention can increase the combustion desulfurization efficiency of the layer combustion furnace to 70-80%.

Description

High-temperature combustion two-stage desulfurization method

The invention relates to the removal of combustion products, in particular to a high-temperature combustion two-stage desulfurization method.

In-furnace combustion desulfurization technology, with low cost and simple process, is one of the more effective ways to solve the serious pollution emission problem of industrial boilers with large quantities and wide areas in our country. However, the low combustion desulfurization efficiency of calcium-based desulfurizers in the layer-fired furnace is a worldwide problem. When Ca/S=2, the combustion desulfurization rate is generally 30-50% when Ca/S=2, using the method of directly spraying calcium in the chain furnace; Using the method of pre-mixing with the loose coal into the furnace, the combustion desulfurization rate is generally 20-40%, and there has been no major breakthrough for a long time. Studies have shown that the main reasons for the low desulfurization rate of calcium-based calcium-based additives in the bed-burning furnace are the high-temperature environment (about 1200°C) of the bed during the combustion process of the bed-burning furnace and the long residence time of the sulfur-fixing agent in the bed. (about 1 hour) makes it difficult for the sulfur-fixing reaction product CaSO ₄ to be generated in large quantities or decomposed again. Therefore, we should not only consider the factors of chemical thermodynamics and reaction kinetics, pay attention to the research on the formula of desulfurizer and its microscopic physical and chemical properties, but more importantly, we should find a breakthrough point on the root cause of the thermal environment of the chain furnace to greatly improve Calcium-based desulfurizer combustion desulfurization rate is low in the layer combustion furnace.

The object of the present invention is to provide a method for high-temperature combustion two-stage desulfurization, which can increase the desulfurization efficiency of a layered combustion furnace to 70-80%.

In order to achieve the above object the present invention takes the following measures:

The high-temperature combustion two-stage desulfurization method is to use wind force to blow part of the calcium-based additive powder into the furnace space, and transfer the combustion desulfurization reaction part in the coal seam of the bed-fired furnace to the combustion space and the entire flue gas flow, so as to capture the release from the coal seam to SO ₂ in the flue gas can achieve two-stage desulfurization in the bed and space; and through air distribution, the reducing atmosphere in the high-temperature combustion section and the oxidizing atmosphere in the post-combustion section can be enhanced to achieve simultaneous desulfurization and denitrification under the premise of ensuring combustion efficiency. Effect.

Advantages of the present invention: adopting three desulfurizing agent addition methods of semi-premixed and semi-powder spraying, premixed blast layering and covered blast layering to realize two-stage desulfurization of the bed and space of the layered furnace, from both time and space On the one hand, it overcomes the fundamental defect of simply premixing with loose coal into the furnace or directly spraying calcium into the furnace for desulfurization, so that the combustion desulfurization efficiency of the layer combustion furnace is increased to 70-80%; and through reasonable air distribution, part of the air volume in the high-temperature combustion section is Move to the tail burner section to achieve the effect of simultaneous desulfurization and denitrification under the premise of ensuring combustion efficiency.

Below in conjunction with embodiment the present invention is described in detail:

The two-stage desulfurization methods are three desulfurizer addition methods: semi-premixed and semi-powder spraying, premixed blast layering and covered blast layering; ember section.

The method of adding the desulfurization calcium-based additives is as follows: 1) The semi-premixed semi-powdering method is to mix part of the desulfurization calcium-based additives with the raw coal evenly before the fuel is put into the furnace, and directly spray another part of the desulfurization calcium-based additives into the furnace. The combustion space in the furnace is used to achieve two-stage desulfurization of the bed and space of the layer-fired furnace; The heat and combustion section uses wind force to blow part of the calcium-based additives in the coal seam into the flue gas space, so as to realize two-stage desulfurization of the bed and space of the bed combustion furnace. 3) The method of covering and blasting layering is to feed desulfurization calcium-based additives and raw coal in layers, and evenly cover a thin layer of calcium-based additive powder on the surface of the coal seam and send it into the furnace, and in the preheating and combustion section of the layer combustion furnace Part of the calcium-based additive in the coal seam is blown into the flue gas space by wind force, and the calcium-based additive spread on the surface of the coal seam is blown into the flue gas space to realize two-stage desulfurization of the bed and space of the bed furnace.

The air distribution method is as follows: under the condition that the total air volume is basically unchanged, the air distribution volume in the high-temperature combustion section of the bed furnace is appropriately reduced through air distribution, and the air distribution volume in the tail combustion section is correspondingly increased.

The principle of the present invention: the main reasons for the low desulfurization rate of calcium-based calcium-based additives in the high-temperature combustion in the bed furnace are: ① The organic sulfur in coal begins to decompose to generate SO ₂ at about 400 ° C, and limestone is the most industrially valuable and widely used It is also the most widely used desulfurizer that begins to decompose in large quantities at around 800°C, so the precipitation rate of organic sulfur in the coal in the preheating section of the bed furnace is far greater than the decomposition rate of CaCO ₃ , and a large amount of SO ₂ escapes and disperses from the coal seam to the combustion space; ②In the high-temperature combustion section of the bed-burning furnace, although a large amount of CaCO ₃ has been decomposed into CaO, due to the influence of primary wind speed, the residence time of SO ₂ in the coal seam is only about 1 second, and SO ₂ is mixed with the coal seam The calcium-based additives in the furnace have serious poor contact problems, so a large amount of SO ₂ escapes into the combustion space before it can react with CaO, and leaves the furnace outlet after staying in the combustion flue gas for 3 to 4 seconds; ③ During the combustion process of the layer combustion furnace The high temperature environment of the bed (about 1200°C) and the long residence time of the sulfur-fixing agent in the bed (about 1 hour) make it difficult for the sulfur-fixing reaction product CaSO ₄ to be generated in large quantities or re-decomposed after being generated. If only calcium-based additives are premixed with loose coal or directly sprayed with calcium in the furnace for desulfurization, the desulfurization rate can only reach 20-50%. The high-temperature combustion two-stage desulfurization technology is used to add desulfurized calcium-based additives into the furnace by half-premixed and half-sprayed powder, premixed blast layering or covered blast layering, and part of the calcium-based additive powder is blown into the furnace by wind force. The furnace space transfers the combustion desulfurization reaction part in the coal seam of the bed-fired furnace to the combustion space and the entire flue gas flow, so as to capture SO ₂ released from the coal seam into the flue gas in a timely and effective manner, and realize two-stage desulfurization of the bed and space, from In terms of time and space, it overcomes the difficulty of low desulfurization rate of calcium-based calcium-based additives in the layer combustion furnace, so that the desulfurization rate is greatly increased to 70-80%; The air distribution volume is appropriately reduced, while the air distribution volume in the tail burnout section is increased accordingly to enhance the reducing atmosphere in the high-temperature combustion section and the oxidative atmosphere in the tail burnout section, so that more sulfur precipitated from coal can be generated in the high-temperature reduction zone of the combustion section. CaS with good thermal stability is then converted into more CaSO ₄ in the low-temperature oxidation section of the burnout section, which overcomes the difficulty of poor thermal stability of CaSO ₄ in the high-temperature oxidation zone, thereby greatly improving the combustion desulfurization rate; Part of the air volume in the high-temperature combustion section is moved to the tail combustion section, which makes the high-temperature distribution curve in the combustion section of the bed-burning furnace tend to be uniform and gentle, and at the same time enhances the reducing atmosphere in the combustion section, so that the thermal _NOx and fuel-type _NOx The amount of generation is greatly reduced, and the effect of simultaneous desulfurization and denitrification is better achieved under the premise of ensuring combustion efficiency.

Embodiment: Hangzhou Coal Garden Hotel 4T/H chain furnace, carried out thermal test and desulfurization effect test in January, 1999 by Zhejiang Provincial Energy Saving Technology Testing Center and Zhejiang Provincial Environmental Testing Center Station, before the water film dust collector, use SYC series flue gas sampler sampling, absorption method capture, and iodometric method to analyze the concentration of SO ₂ in the flue gas; after the water film dust collector, use Wuhan Tianhong Intelligent Instrument Factory HT-900 intelligent flue gas analyzer to measure SO in the flue gas ₂ concentration, the application effect of the two-stage combustion desulfurization technology on the 4T/H chain furnace is shown in Table 1.

Table 1 Application effect of two-stage combustion desulfurization technology on 4T/H chain furnace Test conditions 1 2 3 4 Test coal Raw coal (Q _{b, ad} = 28637kJ/kg, S _{t, ad} = 0.81%) calcium based additives / ZD-P type ZD-H type ZD-P type + ZD-H type Ca/S / 1.4 1.4 2 Add method blank single dusting single premix Two-stage desulfurization (half premixed half powder spraying) Boiler load (t/h) 2.74 2.30 2.50 2.21 Vapor pressure (Mpa) 0.71 0.80 0.77 0.77 _O2 concentration in flue gas (%) 14.8 15.7 14.3 15.7 SO ₂ concentration in flue gas (mg/m ³ .N) 1050 524 633 194 SO ₂ emission in flue gas (kg/h) 6.31 4.25 3.81 1.57 Combustion desulfurization rate before dust collector (%) / 32.6 39.6 75.1 Total desulfurization efficiency after water film dust collector (%) 13.0 63.6 - 83.4 Note: Working conditions 2, 3 and 4 are based on the _SO2 concentration in the combustion flue gas of working condition 1, and the combustion desulfurization rate before the dust collector is calculated. The self-sulfur fixation rate of the blank working condition 1 before the dust collector is about 10%.

Claims (5)

1. two-segment desulfurizing method for high-temp combustion, it is characterized in that the partial desulfurization calcium based additives is gone into the stokehold and the raw coal blending is even at fuel, in combustion process, realize the bed desulfurization, utilize wind-force that another part calcium based additives powder is blown into furnace cavity simultaneously, desulphurization during combustion reactive moieties in the grate furnace coal seam is transferred to combustion space and whole flue gas flow, to catch the SO that is discharged into from the coal seam the flue gas timely and effectively ₂, realize bed and space two-stage desulfurization; And, under the prerequisite that guarantees efficiency of combustion, realize the effect of desulphurization denitration simultaneously by the reducing atmosphere of air distribution enhancing high temperature burning zone and the oxidizing atmosphere of afterbody burning segment.

2. a kind of two-segment desulfurizing method for high-temp combustion according to claim 1 is characterized in that said two-segment desulfurizing method is that half premix partly dusts, premix air blast layering and cover three kinds of desulfurizing agent adding methods of air blast layering; And by moving on to the afterbody burning segment behind the part air quantity of air distribution with high temperature burning zone.

3. a kind of two-segment desulfurizing method for high-temp combustion according to claim 1 and 2, the adding method that it is characterized in that described desulfurization calcium based additives is half premix, half spraying powder method, it is that the partial desulfurization calcium based additives is gone into the stokehold and the raw coal blending is even at fuel, and another part desulfurization calcium based additives is directly sprayed into stove internal combustion space, to realize grate furnace bed and space two-stage desulfurization.

4. a kind of two-segment desulfurizing method for high-temp combustion according to claim 1 and 2, the adding method that it is characterized in that described desulfurization calcium based additives is a premix air blast layered approach, it is that the desulfurization calcium based additives is gone into the stokehold and the raw coal blending is even at fuel, and utilize wind-force that the part calcium based additives in the coal seam is dispelled smoke space in grate furnace preheating and burning zone, to realize grate furnace bed and space two-stage desulfurization.

5. a kind of two-segment desulfurizing method for high-temp combustion according to claim 1 and 2, the adding method that it is characterized in that described desulfurization calcium based additives is for covering the air blast layered approach, it is with desulfurization calcium based additives and raw coal layering feed, very thin one deck calcium based additives powder is evenly covered the surface, coal seam to be sent in the stove, and utilize wind-force that the part calcium based additives in the coal seam is dispelled smoke space in grate furnace preheating and burning zone, the calcium based additives that is tiled in the surface, coal seam is dispelled smoke space, to realize grate furnace bed and space two-stage desulfurization.