Double-circulation desulfurization process for enhancing removal of condensable particulate matters based on condensation effect

Abstract

The invention belongs to the field of environmental protection and energy utilization, and particularly relates to a double-circulation desulfurization process for enhancing removal of condensable particles based on a condensation effect. Firstly, according to the process, a heat exchanger is used for achieving cooling and heat exchange of Ca (OH) 2 slurry which is added with a scale inhibitor and is higher in activity and alkalinity, the cooled upper circulation spraying slurry can enhance the desulfurization exothermic reaction and corrosion prevention about SO2 absorption, and meanwhile condensation growth and removal of particulate matter and condensable particulate matter such as SO3 are promoted. Secondly, cooling and heat exchange are conducted on the desulfurized flue gas through a condensation pipeline additionally arranged below the mechanical demister, and reinforced removal of large-particle-size particles through the demister is achieved by promoting condensation and growth of the particles and condensable particles such as SO3 in the cooled desulfurized flue gas. And finally, cold media in the heat exchanger and the condensation pipeline complete circulation through a circulating pump, absorb heat of desulfurization slurry and flue gas and are used for waste heat recycling of primary air or boiler feed water and the like, the heat loss of the coal-fired power plant is reduced, and the energy utilization rate is increased.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and energy utilization, specifically involving a dual-cycle desulfurization process that uses heat exchangers and condenser pipes to cool desulfurization slurry and flue gas to enhance the condensation effect and strengthen the removal of condensable particulate matter, while simultaneously improving desulfurization efficiency and recovering waste heat. Background Technology

[0002] Guided by national strategic needs such as energy conservation and emission reduction in coal-fired power plants, the Blue Sky Protection Campaign, and the in-depth fight against pollution, significant progress has been made in controlling emissions of conventional pollutants such as SO2 and particulate matter in recent years. However, emissions of unconventional pollutants, such as condensable particulate matter, have been increasing year by year, and condensable particulate matter emissions typically account for more than 50% of total particulate matter emissions, even exceeding 80%, thus their harm cannot be ignored. Current research on condensable particulate matter in coal-fired flue gas, both domestically and internationally, mainly focuses on testing methods, removal efficiency, component detection, and characteristic analysis. Much of this research aims to enhance condensable particulate matter removal by controlling operating conditions such as flue gas temperature, humidity, flow rate, slurry concentration, and spray volume. However, there are few reports on synergistically enhanced removal of condensable particulate matter from desulfurization tower flue gas by utilizing and optimizing existing processes or structures, starting from existing equipment or devices.

[0003] Single-tower dual-circulation desulfurization technology is a highly efficient flue gas desulfurization process developed from the traditional single-tower single-circulation process. By setting up a conical liquid collection hopper within the absorption tower, the slurry system is divided into two independent circulation loops, each undertaking different functions. It surpasses the traditional single-circulation process in efficiency, economy, adaptability, and reliability. Its core advantage lies in independent optimized control through functional zoning: the lower circulation zone has a low slurry pH and focuses on efficient oxidation of calcium sulfite and gypsum crystallization, improving the quality of by-products; the upper circulation zone has a high pH and focuses on efficient absorption of residual SO2, achieving deep desulfurization at a lower liquid-to-gas ratio. For the removal of condensable particulate matter, currently, using condensation and other methods to promote its growth and removal is a feasible approach. Therefore, based on the single-tower dual-cycle desulfurization technology, this invention proposes a dual-cycle desulfurization process that enhances the removal of condensable particulate matter based on the condensation effect, by increasing the pH of the slurry and reducing the temperature of the slurry and flue gas in the upper circulation zone of the dual-cycle desulfurization process, taking into account both physical and chemical reactions, ultimately promoting the condensation, growth, and removal of condensable particulate matter such as SO3, and realizing the recovery and utilization of waste heat from coal-fired power plants. Summary of the Invention

[0004] This invention proposes a dual-cycle desulfurization process based on the condensation effect to enhance the removal of condensable particulate matter. On the basis of the single-tower dual-cycle desulfurization technology, a heat exchanger and condensation pipeline are added to achieve slurry and flue gas cooling. The condensation effect enhances the removal of condensable particulate matter in the desulfurization flue gas, while realizing the recovery and utilization of waste heat from coal-fired power plants.

[0005] This invention mainly includes the following:

[0006] A dual-cycle desulfurization process based on condensation effect to enhance the removal of condensable particulate matter includes a lower circulation desulfurization tower body, an upper circulation desulfurization outer tower, an oxidation fan, and a gypsum discharge pump. Coal-fired flue gas enters the lower circulation desulfurization tower body through the flue gas inlet of the desulfurization tower. The flue gas flows upward sequentially through the lower circulation spray layer, the upper circulation spray layer, and a demister. The slurry in the lower circulation desulfurization tower body and the upper circulation desulfurization outer tower is forced to oxidize by air pumped in by the oxidation fan. The gypsum generated after oxidation is discharged by the gypsum discharge pump. The lower circulation spray layer is formed by pumping CaCO3 slurry from the lower circulation desulfurization tower body into mechanical atomizing nozzles via the lower circulation slurry pump. The liquid and flue gas achieve counter-current contact; the upper circulating spray layer is formed by the Ca(OH)2 slurry in the upper circulating desulfurization outer tower being pumped into the mechanical atomizing nozzle by the upper circulating slurry pump. The slurry collected in the collection hopper is returned to the upper circulating desulfurization outer tower through the conveying pipe. The conveying pipe and the upper circulating desulfurization outer tower are equipped with a partition wall heat exchanger and an immersion coil heat exchanger. The cold medium (air or water, etc.) in the heat exchanger is powered by the cold medium circulation pump to achieve circulating heat exchange; the demisting device consists of a lower condensing pipe and an upper mechanical demister. The cold medium (air or water, etc.) in the condensing pipe is provided by the cold medium circulation pump and achieves heat exchange and cooling of the desulfurization flue gas.

[0007] First, in a dual-cycle desulfurization process based on the condensation effect to enhance the removal of condensable particulate matter, an indirect heat exchanger outside the slurry delivery pipe and an immersed coil heat exchanger in the outer tower of the upper circulation are added to the upper circulation. The cold medium (air or water, etc.) in the heat exchanger is circulated by the cold medium circulation pump and achieves cooling and heat exchange of Ca(OH)2 slurry. The cooled upper circulation spray slurry can enhance the desulfurization exothermic reaction related to SO2 absorption on the one hand, and promote the condensation, growth and removal of particulate matter and condensable particulate matter such as SO3 on the other hand.

[0008] Secondly, in a dual-cycle desulfurization process based on the condensation effect to enhance the removal of condensable particulate matter, a condensation pipeline is added between the upper circulation mechanical atomizing nozzle and the mechanical demister. The condensation pipeline carries a cold medium (air or water, etc.) that is circulated by a cold medium circulation pump and achieves cooling and heat exchange of the desulfurization flue gas. By promoting the condensation and growth of particulate matter and condensable particulate matter such as SO3 in the cooled desulfurization flue gas, the demister can enhance the removal of large-diameter particulate matter.

[0009] Meanwhile, in a dual-cycle desulfurization process based on the condensation effect to enhance the removal of condensable particulate matter, a scale inhibitor is added to the outer tower of the upper circulation desulfurization system. The Ca(OH)2 slurry, which is more alkaline, active, and soluble, is pumped into a mechanical atomizing nozzle via the upper circulation slurry pump to form a spray layer, thereby enhancing the desulfurization effect, preventing scaling, reducing equipment corrosion rate, and extending equipment lifespan. The slurry collected in the collection hopper is returned to the outer tower of the upper circulation desulfurization system via a conveying pipe. The Ca(OH)2 can be derived from CaO calcined from CaCO3, making it easy to add and mix during the production process of coal-fired power plants, which helps optimize the production process of thermal power plants and improve production efficiency.

[0010] Finally, in a dual-cycle desulfurization process based on the enhanced removal of condensable particulate matter through condensation effect, the cold medium (air or water, etc.) in the indirect heat exchanger, immersion coil heat exchanger, and condensation pipeline added to the dual-cycle system is circulated by a circulating pump to achieve cooling and heat exchange of the desulfurization slurry and flue gas. The cold medium, such as air or water, after absorbing heat can be used for waste heat utilization such as primary air or boiler feedwater, which helps to reduce heat loss in coal-fired power plants and improve energy efficiency.

[0011] Beneficial effects

[0012] This invention has the following innovative features compared to existing processes:

[0013] First, based on the dual-circulation process, physical and chemical reactions are fully utilized, while simultaneously reducing the slurry temperature and increasing the slurry pH, ultimately promoting the condensation, growth, and washing removal of condensable particles such as SO3.

[0014] Secondly, a condensation pipeline is added to the dual-circulation process to promote the condensation and growth of condensable particles by reducing the flue gas temperature, and large-diameter particles are removed by using the existing demister.

[0015] Finally, based on the dual-circulation process, heat exchangers and condenser pipes are used to achieve heat exchange between the slurry, flue gas and cold medium, thus completing the recovery and utilization of waste heat from coal-fired power plants.

[0016] Compared with existing technologies, the present invention has the following advantages:

[0017] First, by fully integrating the single-tower dual-circulation technology, the cold medium (air or water, etc.) in the indirect heat exchanger outside the slurry delivery pipe and the immersion coil heat exchanger in the upper circulation outer tower is comprehensively utilized to achieve cooling and heat exchange of the more alkaline and active Ca(OH)2 slurry. The cooled upper circulation spray slurry enhances the desulfurization reaction of SO2 absorption and promotes the condensation, growth, and removal of particulate matter and condensable particulate matter such as SO3. At the same time, the addition of scale inhibitors to the slurry can prevent scaling and extend the service life of the equipment.

[0018] Secondly, a condensation pipeline is added between the upper circulation mechanical atomizing nozzle and the mechanical demister in the dual-circulation desulfurization technology. The cold medium (air or water, etc.) in the condensation pipeline cools and heats the desulfurization flue gas. By promoting the condensation and growth of particulate matter and condensable particulate matter such as SO3 in the cooled desulfurization flue gas, the demister can effectively remove large-diameter particulate matter.

[0019] Finally, the cold medium (air or water, etc.) in the indirect heat exchanger, immersion coil heat exchanger and condenser pipeline added on the basis of dual-circulation desulfurization technology is circulated by the circulation pump and absorbs the heat of desulfurization slurry and flue gas, and is used for primary air or boiler feedwater for waste heat utilization, which helps to reduce the heat loss of coal-fired power plants and improve energy utilization efficiency. Attached Figure Description

[0020] Figure 1 A schematic diagram of a dual-cycle desulfurization process based on the condensation effect to enhance the removal of condensable particulate matter.

[0021] 1-Lower circulation desulfurization tower main body; 2-Upper circulation desulfurization outer tower; 3-Oxidation fan; 4-Gypsum discharge pump; 11-Desulfurization tower flue inlet;

[0022] 12-CaCO3 slurry; 13-lower circulating slurry pump; 14-mechanical atomizing nozzle; 21-Ca(OH)2 slurry; 22-upper circulating slurry pump;

[0023] 23-Mechanical atomizing nozzle; 24-Liquid collecting hopper; 25-Slurry delivery pipe; 26-Indirect heat exchanger; 27-Immersed coil heat exchanger;

[0024] 28 - Cold medium circulation pump; 31 - Condensate piping; 32 - Mechanical demister Detailed Implementation

[0025] As per the instruction manual Figure 1 As shown, the coal-fired flue gas enters the main body (1) of the lower circulation desulfurization tower through the flue gas inlet (11). The flue gas flows from bottom to top through the lower circulation spray layer, the upper circulation spray layer and the demisting device.

[0026] The lower circulating spray layer is formed by the CaCO3 slurry (12) in the lower circulating desulfurization tower body (1) being pumped into the mechanical atomizing nozzle (14) by the lower circulating slurry pump (13), and the sprayed slurry and flue gas are in reverse contact; the upper circulating spray layer is formed by the Ca(OH)2 slurry (21) in the upper circulating desulfurization outer tower (2) being pumped into the mechanical atomizing nozzle (23) by the upper circulating slurry pump (22), and the slurry collected in the collection hopper (24) is returned to the upper circulating desulfurization outer tower via the conveying pipe (25). 2) The conveying pipe (25) and the upper circulating desulfurization outer tower (2) are equipped with a partition heat exchanger (26) and an immersion coil heat exchanger (27). The cold medium (air or water, etc.) in the heat exchanger is powered by the cold medium circulation pump (28) to achieve circulating heat exchange. The demisting device consists of a lower condenser pipe (31) and an upper mechanical demister (32). The cold medium (air or water, etc.) in the condenser pipe (31) is provided by the cold medium circulation pump (28) to achieve heat exchange and cooling of the desulfurization flue gas.

[0027] Finally, the desulfurized flue gas is discharged from the desulfurization tower after passing through the demister. The slurry in the main body (1) of the lower circulation desulfurization tower and the outer tower (2) of the upper circulation desulfurization tower is pumped into the air by the oxidation blower (3) for forced oxidation. The gypsum generated after oxidation is discharged by the gypsum discharge pump (4). By passing through the above-mentioned dual-circulation desulfurization process based on the condensation effect to enhance the removal of condensable particulate matter, the flue gas can achieve enhanced removal of SO2 and condensable particulate matter as well as the recovery and utilization of waste heat.

Claims

1. A dual-cycle desulfurization process based on the condensation effect to enhance the removal of condensable particulate matter, characterized in that, The system includes a lower circulation desulfurization tower body (1), an upper circulation desulfurization outer tower (2), an oxidation blower (3), and a gypsum discharge pump (4). The coal-fired flue gas enters the lower circulation desulfurization tower body (1) through the desulfurization tower flue inlet (11). The flue gas flows upwards sequentially through the lower circulation spray layer, the upper circulation spray layer, and the demister. The slurry in the lower circulation desulfurization tower body (1) and the upper circulation desulfurization outer tower (2) is forced to oxidize by air pumped in by the oxidation blower (3). The gypsum generated after oxidation is discharged by the gypsum discharge pump (4). The lower circulation spray layer is formed by the CaCO3 slurry (12) in the lower circulation desulfurization tower body (1) being pumped into mechanical atomizing nozzles (14) by the lower circulation slurry pump (13). The sprayed slurry and flue gas achieve reverse contact. The upper circulation spray layer is formed by… The Ca(OH)2 slurry (21) in the upper circulation desulfurization outer tower (2) is pumped into the mechanical atomizing nozzle (23) by the upper circulation slurry pump (22). The slurry collected in the collection hopper (24) is returned to the upper circulation desulfurization outer tower (2) through the conveying pipe (25). The conveying pipe (25) and the upper circulation desulfurization outer tower (2) are equipped with a partition heat exchanger (26) and an immersion coil heat exchanger (27). The cold medium (air or water, etc.) in the heat exchanger is powered by the cold medium circulation pump (28) to achieve circulating heat exchange. The demisting device consists of a lower condenser pipe (31) and an upper mechanical demister (32). The cold medium (air or water, etc.) in the condenser pipe (31) is provided by the cold medium circulation pump (28) and achieves heat exchange and cooling of the desulfurization flue gas.

2. The dual-cycle desulfurization process based on condensation effect to enhance the removal of condensable particulate matter according to claim 1, characterized in that, in An indirect heat exchanger (26) is added outside the slurry delivery pipe (25) on the basis of the upper circulation and an immersion coil heat exchanger (27) is added in the upper circulation outer tower. The cold medium (air or water, etc.) in the heat exchanger is circulated by the cold medium circulation pump (28) and the Ca(OH)2 slurry (21) is cooled and heat exchanged. The cooled upper circulation spray slurry can enhance the desulfurization exothermic reaction related to SO2 absorption on the one hand, and promote the condensation, growth and removal of particulate matter and condensable particulate matter such as SO3 on the other hand.

3. The dual-cycle desulfurization process based on condensation effect to enhance the removal of condensable particulate matter according to claim 1, characterized in that, in A condenser pipe (31) is added between the upper circulating mechanical atomizing nozzle (23) and the mechanical demister (32). The condenser pipe (31) is filled with a cold medium (air or water, etc.) that is circulated by a cold medium circulation pump (28) to achieve cooling and heat exchange of the desulfurization flue gas. By promoting the condensation and growth of particulate matter and condensable particulate matter such as SO3 in the cooled desulfurization flue gas, the demister can effectively remove large-diameter particulate matter.

4. The dual-cycle desulfurization process based on condensation effect to enhance the removal of condensable particulate matter according to claims 1 and 2, characterized in that, The Ca(OH)2 slurry (21) with stronger alkalinity, activity and solubility of scale inhibitor added to the upper circulation desulfurization outer tower (2) is pumped into the mechanical atomizing nozzle (23) by the upper circulation slurry pump (22) to form a spray layer to enhance the desulfurization effect, prevent scaling, reduce the equipment corrosion rate and extend the service life of the equipment. The slurry collected in the collection hopper (24) is returned to the upper circulation desulfurization outer tower (2) through the conveying pipe (25). The Ca(OH)2 can be obtained from CaO calcined from CaCO3, which is convenient to add and mix in the production process of coal-fired power plants, which helps to optimize the production process of thermal power plants and improve production efficiency.

5. A dual-cycle desulfurization process based on condensation effect to enhance the removal of condensable particulate matter, as described in claims 1, 2, 3, and 4, characterized in that, in The cold medium (air or water, etc.) in the additional indirect heat exchanger (26), immersion coil heat exchanger (27) and condenser (31) on the basis of dual circulation is circulated by the circulation pump (28) to achieve cooling and heat exchange of desulfurization slurry and flue gas. The cold medium such as air or water after absorbing heat can be used for waste heat utilization such as primary air or boiler feedwater, which helps to reduce the heat loss of coal-fired power plants and improve energy utilization.

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