System for improving yield of high-pressure steam in process of preparing acid from sulfur and use method

Abstract

The invention discloses a system for increasing the high-pressure steam yield in the sulfur acid making process and a using method, and relates to the technical field of sulfur acid making. The system comprises a low-temperature heat recovery tower, a low-pressure steam generation unit, a diluter, a high-pressure boiler feed water heater, a conversion system and a steam recycling unit; the heat source is low-pressure steam by-produced by the low-pressure steam generation unit and is used for heating combustion-supporting air entering the sulfur burning furnace and flue gas entering the conversion system; and the high-pressure steam generation equipment is connected with the sulfur burning furnace and is used for receiving high-pressure boiler feed water preheated by the high-pressure boiler feed water heater and the economizer of the conversion system and generating high-pressure saturated steam. And heat energy is wasted.

Description

Technical Field

[0001] This invention relates to the field of sulfuric acid production technology, and in particular to a system and method for increasing the output of high-pressure steam in the sulfuric acid production process. Background Technology

[0002] Sulfur-based sulfuric acid production technology utilizes liquid sulfur as a raw material, which is fully combusted into flue gas under the action of air. This flue gas is then processed through multiple conversions and absorptions to produce high-concentration sulfuric acid. The heat generated during sulfur combustion, conversion, and absorption processes can produce steam as a byproduct. This byproduct steam can be used for steam turbine power generation. However, low-pressure steam power generation has relatively low efficiency. If the high-pressure steam output can be increased through process optimization, the efficiency of the sulfur-based sulfuric acid production plant can be significantly improved, and production costs reduced.

[0003] In the traditional sulfuric acid production process of the low-temperature heat recovery system, a low-temperature heat recovery tower is used to replace the first absorption tower system. The high-temperature sulfuric acid at the outlet is cooled by low-pressure steam produced by the low-pressure waste boiler and then split: part of it is diluted and returned to the low-temperature heat recovery tower to maintain the acid concentration; the other part flows through the low-pressure boiler feed water heater and the demineralized water preheater in sequence before being sent to the second absorption tower system. However, the sulfuric acid temperature at the outlet of the demineralized water preheater is still as high as 131°C, while the second absorption tower circulating acid system requires an inlet acid temperature of about 70°C. This results in the waste heat within the 60°C temperature difference range not being effectively recovered and having to rely on circulating water for cooling, causing a large amount of low-grade heat energy to be wasted and significantly increasing the load and operating cost of the circulating water system.

[0004] Therefore, how to provide a system for increasing the output of high-pressure steam in the sulfuric acid production process by utilizing low-pressure steam to increase the output of high-pressure steam and reduce the consumption of circulating water is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a system for increasing the output of high-pressure steam in the sulfuric acid production process, which effectively solves the technical problem of waste heat in existing low-temperature heat recovery systems and the waste of thermal energy.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A system for increasing the production of high-pressure steam in the sulfuric acid production process includes:

[0008] Low-temperature heat recovery tower;

[0009] The low-pressure steam generating unit is connected to the sulfuric acid outlet of the low-temperature heat recovery tower, and is used to utilize the high-temperature sulfuric acid to produce low-pressure steam as a byproduct, and output the cooled sulfuric acid.

[0010] The diversion loop is configured to divide the cooled sulfuric acid into a circulation path and a heat exchange path; the diluent is connected to the circulation path and is used to dilute a portion of the cooled sulfuric acid and return it to the low-temperature heat recovery tower; the heat exchange path has multiple heat exchangers arranged in series to cool another portion of the cooled sulfuric acid in stages; wherein, at least one of the multiple heat exchangers includes a high-pressure boiler feedwater heater for preheating the high-pressure boiler feedwater;

[0011] The steam reuse unit, whose heat source is the low-pressure steam produced by the low-pressure steam generation unit, is used to heat the combustion air entering the sulfur incinerator and the flue gas entering the conversion system; the high-pressure steam generation equipment, connected to the sulfur incinerator, is used to receive the high-pressure boiler feedwater preheated by the high-pressure boiler feedwater heater and the economizer of the conversion system and generate high-pressure saturated steam; the conversion system is used to receive the high-pressure saturated steam and the flue gas.

[0012] Preferably, the plurality of heat exchangers includes a low-pressure boiler feedwater heater, a high-pressure boiler feedwater heater, and a demineralized water preheater connected in sequence, and the cooled sulfuric acid flows sequentially through the low-pressure boiler feedwater heater, the high-pressure boiler feedwater heater, and the demineralized water preheater for staged cooling.

[0013] Preferably, the sulfuric acid cooled by the demineralized water preheater is conveyed to the secondary absorption tower circulation unit; the secondary absorption tower circulation unit includes:

[0014] The inlet of the second absorption tower circulating acid tank is connected to the sulfuric acid outlet of the demineralized water preheater;

[0015] The inlet of the second-suction tower acid cooler is connected to the outlet of the second-suction tower circulating acid tank, and circulating water is circulated into the second-suction tower acid cooler as a cooling medium.

[0016] The inlet of the second-absorption tower is connected to the outlet of the acid cooler of the second-absorption tower, and the bottom acid outlet of the tower is connected to the inlet of the circulating acid tank of the second-absorption tower, thus forming an acid circulation loop.

[0017] Preferably, the steam reuse unit includes an air preheater and a flue gas preheater;

[0018] The air preheater is installed on the air pipeline between the outlet of the drying tower and the combustion air inlet of the sulfur incinerator.

[0019] The flue gas preheater is located on the flue gas pipeline between the flue gas outlet of the low-temperature heat recovery tower and the inlet of the conversion system.

[0020] Preferably, the low-pressure steam generating unit is a low-pressure waste boiler, and its low-pressure steam outlet is connected to the steam inlet of the air preheater and the flue gas preheater, respectively.

[0021] Preferably, the high-pressure steam generating equipment is a waste heat boiler, whose flue gas inlet is connected to the high-temperature flue gas outlet of the sulfur incinerator, and whose feedwater inlet receives high-pressure boiler feedwater preheated by the high-pressure boiler feedwater heater and the economizer of the conversion system.

[0022] Preferably, it also includes a main fan, the inlet of which is connected to the air outlet of the drying tower, and the outlet of which is connected to the air inlet of the air preheater.

[0023] Preferably, the heat exchange elements of the air preheater and the flue gas preheater are made of carbon steel; the steam condensate produced by the air preheater and the flue gas preheater is returned to the deaerator.

[0024] A method of using the above-described system for increasing high-pressure steam production in sulfuric acid production includes the following steps:

[0025] S1. High-temperature sulfuric acid from the low-temperature heat recovery tower is introduced into the low-pressure steam generation unit, and low-pressure steam is produced by heat exchange, and cooled sulfuric acid is obtained.

[0026] S2. The cooling sulfuric acid is divided into two parts. The first part is sent to the diluent for dilution and then returned to the low-temperature heat recovery tower for recycling. The second part is sent into the heat exchange path for heat recovery.

[0027] S3. The sulfuric acid entering the heat exchange path is sequentially passed through a low-pressure boiler feed water heater, a high-pressure boiler feed water heater, and a demineralized water preheater for three-stage heat exchange, thereby achieving step-by-step cooling of the sulfuric acid and preheating of the boiler feed water and demineralized water.

[0028] S4. The low-pressure steam generated by the low-pressure steam generating unit is introduced into the steam reuse unit to heat the combustion air entering the sulfur incinerator and the flue gas entering the conversion system, respectively.

[0029] S5. The high-pressure boiler feedwater, which has been preheated by the high-pressure boiler feedwater heater, is sent to the economizer of the conversion system for preheating and then sent to the high-pressure steam generator to generate high-pressure saturated steam using the high-temperature flue gas from the sulfur incinerator.

[0030] S6. Introduce the high-pressure saturated steam and the preheated flue gas together into the conversion system.

[0031] Preferably, in step S3, the temperature of the sulfuric acid cooled by the demineralized water preheater is not higher than 70°C, and in step S4, the temperature of the air heated by the air preheater is not lower than 160°C.

[0032] Compared with the above-mentioned background technology, the system for increasing the high-pressure steam output in the sulfuric acid production process provided by the present invention has the following beneficial effects:

[0033] By using a high-pressure feedwater heat exchanger to preheat the high-pressure boiler feedwater with cooled sulfuric acid, the feedwater temperature is increased. At the same time, the flue gas and air are heated by a flue gas preheater and an air preheater, increasing the flue gas temperature and increasing the heat in the steam superheating section of the conversion system. This achieves the transfer of heat from the sensible heat section (low-temperature heat) to the latent heat section (high-temperature heat). Without increasing the fuel consumption of the sulfur incinerator, the high-pressure steam output per ton of acid is increased from about 1.28 tons in the traditional process to 1.45-1.50 tons, effectively enhancing the plant's self-generating capacity.

[0034] By fully recovering low-temperature waste heat and reducing circulating water consumption, all the waste heat from the 131℃→70℃ acid side that originally needed to be cooled by circulating water is used to preheat the high-pressure / low-pressure boiler feedwater and demineralized water, thus avoiding heat waste. At the same time, the load on the second absorption tower acid cooler is significantly reduced, the amount of circulating cooling water used is reduced, and the investment in auxiliary equipment is reduced.

[0035] To achieve high-value utilization of low-pressure steam, the low-pressure steam produced by low-pressure waste boilers is used to heat combustion air and flue gas before conversion. By utilizing steam condensation heat exchange, the heat exchange efficiency is greatly increased, the heat exchange area required for heat exchange is greatly reduced, and the equipment cost is significantly reduced.

[0036] To improve system safety and economy, the air preheater and flue gas preheater use low-pressure steam as an indirect heating medium, avoiding direct contact between concentrated sulfuric acid and the heated fluid. The equipment can be made of carbon steel, which significantly reduces investment costs and eliminates the risk of acid leakage. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of a system connection for increasing the output of high-pressure steam in the sulfuric acid production process, provided by an embodiment of the present invention.

[0039] in:

[0040] 1-Low-temperature heat recovery tower, 2-Low-pressure steam generation unit, 3-Dilutioner, 4-High-pressure boiler feedwater heater, 5-Sulfur incinerator, 6-High-pressure steam generation equipment, 7-Low-pressure boiler feedwater heater, 8-Demineralized water preheater, 9-Secondary absorption tower circulating acid tank, 10-Secondary absorption tower acid cooler, 11-Secondary absorption tower body, 12-Air preheater, 13-Flue gas preheater, 14-Drying tower, 15-Conversion system, 16-Main fan. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] See Figure 1 This application provides a system for increasing the high-pressure steam output during sulfuric acid production, comprising: a low-temperature heat recovery tower 1; a low-pressure steam generation unit 2 connected to the sulfuric acid outlet of the low-temperature heat recovery tower 1, used to utilize high-temperature sulfuric acid as a byproduct to produce low-pressure steam and output cooled sulfuric acid; a diversion loop configured to divide the cooled sulfuric acid into a circulation path and a heat exchange path; a diluent 3 connected to the circulation path, used to dilute a portion of the cooled sulfuric acid and return it to the low-temperature heat recovery tower 1; and a heat exchange path, in which multiple heat exchangers are arranged in series for further processing of the remaining cooled sulfuric acid. The cooling process is tiered; at least one high-pressure boiler feedwater heater 4 is included among the multiple heat exchangers for preheating the high-pressure boiler feedwater; a steam reuse unit, whose heat source is low-pressure steam produced by the low-pressure steam generating unit 2, is used to heat the combustion air entering the sulfur incinerator 5 and the flue gas entering the conversion system 15; a high-pressure steam generating device 6 is connected to the sulfur incinerator 5 and is used to receive the high-pressure boiler feedwater preheated by the high-pressure boiler feedwater heater 4 and the economizer of the conversion system 15 and generate high-pressure saturated steam; the conversion system 15 is used to receive the high-pressure saturated steam and the preheated flue gas.

[0044] In other words, the low-temperature heat recovery tower 1 is used to recover low-temperature sensible heat from flue gas and absorb heat through sulfuric acid circulation to generate high-temperature sulfuric acid; the low-pressure steam generation unit 2 is connected to the sulfuric acid outlet of the low-temperature heat recovery tower 1, receives high-temperature sulfuric acid and uses its heat to produce low-pressure steam as a byproduct, and outputs cooled sulfuric acid at a temperature of about 195°C.

[0045] The diversion loop, located downstream of the low-pressure steam generator unit 2, is configured to distribute the cooled sulfuric acid into a circulation flow path and a heat exchange flow path according to the process ratio.

[0046] Diluter 3 is connected to the circulation path and is used to dilute most of the sulfuric acid and return it to the inlet of the low-temperature heat recovery tower 1.

[0047] The heat exchange path includes multiple heat exchangers arranged in series to cool another small portion of sulfuric acid in stages and recover its low-temperature waste heat; at least one high-pressure boiler feedwater heater 4 is provided in the heat exchanger to preheat the high-pressure boiler feedwater to the process set temperature.

[0048] The steam reuse unit has a heat source from the low-pressure steam produced by the low-pressure steam generator unit 2. It is used to preheat the combustion air entering the sulfur incinerator 5 and the flue gas entering the conversion system 15, respectively, so as to realize the conversion of low-temperature heat into high-temperature heat.

[0049] The high-pressure steam generator 6 is connected to the high-temperature flue gas outlet of the sulfur incinerator 5. It is used to receive the high-pressure boiler feedwater preheated by the economizer of the high-pressure boiler feedwater heater 4 and the conversion system 15, and to generate high-pressure saturated steam using the heat of the flue gas.

[0050] The conversion system 15 is connected at its inlet to the high-pressure saturated steam outlet of the high-pressure steam generator 6 and the flue gas outlet of the steam reuse unit. It is used to catalytically convert sulfur dioxide while superheating the high-pressure saturated steam with high-temperature flue gas, and finally output high-pressure superheated steam for power generation.

[0051] Based on the above embodiments, multiple heat exchangers include a low-pressure boiler feedwater heater 7, a high-pressure boiler feedwater heater 4, and a demineralized water preheater 8 connected in sequence. The cooled sulfuric acid flows through the low-pressure boiler feedwater heater 7, the high-pressure boiler feedwater heater 4, and the demineralized water preheater 8 in sequence for staged cooling.

[0052] In other words, the heat exchangers in the heat exchange path include a low-pressure boiler feedwater heater 7, a high-pressure boiler feedwater heater 4, and a demineralized water preheater 8 connected in series. After being cooled to approximately 185°C, the sulfuric acid flows out from the low-pressure steam generating unit 2 and then flows sequentially through the low-pressure boiler feedwater heater 7, the high-pressure boiler feedwater heater 4, and the demineralized water preheater 8, achieving cascaded heat recovery and step-by-step cooling.

[0053] In the low-pressure boiler feedwater heater 7, sulfuric acid first transfers heat to the low-pressure boiler feedwater to preheat it, while its own temperature initially decreases. Simultaneously, the low-pressure boiler water, after heat exchange, is output into the low-pressure steam generating unit 2. It then enters the high-pressure boiler feedwater heater 4, where the waste heat is used to preheat the high-pressure boiler feedwater, increasing the feedwater temperature entering the high-pressure steam generating equipment 6, thereby increasing the high-pressure steam output. Finally, it flows through the demineralized water preheater 8 to further recover the waste heat from the low-temperature section to preheat the demineralized water.

[0054] After three stages of heat exchange, the temperature of sulfuric acid drops to about 70°C, and then it is transported to the second absorption tower circulation unit, avoiding the energy waste caused by the need to cool the acid flow with circulating water in the traditional process.

[0055] Based on the above embodiments, the sulfuric acid cooled by the demineralized water preheater 8 is transported to the secondary suction tower circulation unit. The secondary suction tower circulation unit includes a secondary suction tower circulating acid tank 9, whose inlet is connected to the sulfuric acid outlet of the demineralized water preheater 8; a secondary suction tower acid cooler 10, whose inlet is connected to the outlet of the secondary suction tower circulating acid tank 9, and circulating water is introduced into the secondary suction tower acid cooler 10 as a cooling medium; and a secondary suction tower body 11, whose inlet is connected to the outlet of the secondary suction tower acid cooler 10, and whose bottom acid outlet is connected to the inlet of the secondary suction tower circulating acid tank 9, thus forming an acid circulation loop.

[0056] In other words, the sulfuric acid, cooled by the demineralized water preheater 8, is delivered to the secondary absorption tower circulation unit at a temperature of approximately 70°C. The secondary absorption tower circulation unit includes:

[0057] The second absorption tower circulating acid tank 9 has its inlet connected to the sulfuric acid outlet of the demineralized water preheater 8, and is used to receive and temporarily store low-temperature concentrated sulfuric acid after waste heat recovery.

[0058] The secondary absorption tower acid cooler 10 has its inlet connected to the outlet of the secondary absorption tower circulating acid tank 9. Circulating cooling water is introduced into the tank as a cooling medium to further remove the dilution heat generated during the absorption process and maintain the absorption acid temperature in a suitable range, usually 50℃-70℃.

[0059] The inlet of the secondary suction tower body 11 is connected to the outlet of the secondary suction tower acid cooler 10, which is used to spray the cooled concentrated sulfuric acid into the tower; the bottom acid outlet of the secondary suction tower body 11 is connected to the inlet of the secondary suction tower circulating acid tank 9, thus forming a closed acid circulation loop.

[0060] Since the sulfuric acid entering the second absorption tower circulation unit has been fully cooled from about 195°C to about 70°C in the front-end heat exchange process, the amount of circulating cooling water required for the second absorption tower acid cooler 10 is greatly reduced, significantly reducing the energy consumption and operating cost of the circulating water system.

[0061] Based on the above embodiments, the steam reuse unit includes an air preheater 12 and a flue gas preheater 13; the air preheater 12 is installed on the air pipeline between the outlet of the drying tower 14 and the combustion air inlet of the sulfur incinerator 5; the flue gas preheater 13 is installed on the flue gas pipeline between the flue gas outlet of the low-temperature heat recovery tower 1 and the inlet of the conversion system 15, and both the air preheater 12 and the flue gas preheater 13 use low-pressure steam as the heating medium.

[0062] In other words, the steam reuse unit includes an air preheater 12 and a flue gas preheater 13. Both of them use the low-pressure saturated steam produced by the low-pressure steam generation unit 2 as the heating medium and preheat the process fluid through condensation and heat release to achieve efficient reuse of low-grade thermal energy.

[0063] Air preheater 12 is installed on the air pipeline between the outlet of drying tower 14 and the combustion air inlet of sulfur incinerator 5, and is used to preheat the ambient temperature air after dehydration in the drying tower to 163°C. After the preheated high-temperature combustion air enters sulfur incinerator 5 at a temperature of 163°C, it can significantly increase the liquid sulfur combustion temperature, thereby raising the initial temperature of the flue gas at the outlet of sulfur incinerator and enhancing the steam production capacity of the subsequent waste heat boiler. In particular, the heating medium used in air preheater 12 is 0.9 MPaG low-pressure steam.

[0064] The flue gas preheater 13 is installed on the flue gas pipeline between the flue gas outlet of the low-temperature heat recovery tower 1 and the inlet of the conversion system 15. It is used to further heat the flue gas passing through the low-temperature heat recovery tower to 163°C, which effectively increases the initial temperature of the flue gas entering the conversion system 15 and provides a higher-grade heat source for subsequent high-pressure steam superheating. In particular, the heating medium used in the flue gas preheater is 0.9MPaG low-pressure steam.

[0065] After the low-pressure steam completes condensation and heat exchange in the air preheater 12 and the flue gas preheater 13, the resulting condensate is uniformly recycled to the deaerator via the condensate drainage system.

[0066] Furthermore, since low-pressure steam is used as the indirect heating medium, the heat exchange elements of the air preheater 12 and the flue gas preheater 13 can be made of carbon steel, avoiding the need for high-cost corrosion-resistant alloys such as stainless steel required for traditional direct heat exchange on the acid side, thus significantly reducing equipment investment costs. At the same time, due to the high heat transfer coefficient of steam condensation, the required heat exchange area is greatly reduced, further optimizing the compactness and economy of the equipment.

[0067] Based on the above embodiments, the low-pressure steam generating unit 2 is a low-pressure waste boiler, and its low-pressure steam outlet is connected to the steam inlet of the air preheater 12 and the flue gas preheater 13, respectively.

[0068] Based on the above embodiments, the low-pressure steam generating unit 2 is a low-pressure waste heat boiler, referred to as "low-pressure waste boiler". Its sulfuric acid inlet is connected to the high-temperature sulfuric acid outlet of the low-temperature heat recovery tower 1, using high-temperature sulfuric acid as a heat source and producing low-pressure saturated steam as a by-product.

[0069] The low-pressure steam outlet of the low-pressure waste boiler is connected to the steam inlet of the air preheater 12 and the flue gas preheater 13 through a steam distribution pipeline. The low-pressure steam produced is supplied to the two preheating devices simultaneously as a heating medium. During operation, the low-pressure steam enters the air preheater 12 and the flue gas preheater 13 and then condenses and releases heat, which is used to heat the combustion air and the flue gas before conversion, respectively. The condensate produced is collected by their respective condensate draining devices and then uniformly transported to the deaerator or boiler feedwater system to achieve dual recovery of working medium and heat.

[0070] In other words, this application realizes the efficient cascade utilization of low-pressure steam. Low-pressure steam, which could originally only be used for low-grade heating or a small amount of power generation, indirectly promotes the increase of high-pressure steam production, thereby effectively converting low-grade thermal energy into high-grade electrical energy or process steam, and improving the energy utilization efficiency of the entire sulfuric acid production system.

[0071] Based on the above embodiments, the high-pressure steam generating equipment 6 is a waste heat boiler, whose flue gas inlet is connected to the high-temperature flue gas outlet of the sulfur incinerator 5, and whose feedwater inlet receives the high-pressure boiler feedwater preheated by the economizer of the high-pressure boiler feedwater heater 4 and the conversion system 15.

[0072] In other words, the high-pressure steam generator 6 is a waste heat boiler, whose flue gas inlet is connected to the high-temperature flue gas outlet of the sulfur incinerator 5 to receive sulfur incineration flue gas; its feedwater inlet receives high-pressure boiler feedwater that has been preheated in two stages.

[0073] Specifically, the high-pressure boiler feedwater is first preheated in the high-pressure boiler feedwater heater 4 using the residual heat of the cooled sulfuric acid; then, the preheated feedwater is transported to the economizer located in the flue gas passage of the conversion system 15 for secondary preheating, which further increases the feedwater temperature; finally, the high-pressure boiler feedwater, which has undergone two stages of preheating, enters the high-pressure steam generator 6.

[0074] Based on the above embodiments, a main fan 16 is also included, whose inlet is connected to the air outlet of the drying tower 14 and whose outlet is connected to the air inlet of the air preheater 12, for conveying dry air to the air preheater 12.

[0075] Specifically, the air from the atmosphere first removes moisture in the drying tower 14 to form dry air. The dry air is then drawn in and pressurized by the main fan 16, and after overcoming the system resistance, it is sent to the air preheater 12.

[0076] Furthermore, the low-temperature heat recovery tower 1, low-pressure waste boiler, diluent 3, high-pressure boiler feed water heater 4, sulfur incinerator 5, waste heat boiler, low-pressure boiler feed water heater 7, demineralized water preheater 8, secondary suction tower circulating acid tank 9, secondary suction tower acid cooler 10, secondary suction tower body 11, air preheater 12, flue gas preheater 13, drying tower 14, conversion system 15, and main fan 16 are all conventional devices known in the field of sulfuric acid production. Their structural forms, connection methods, and basic working principles have been fully disclosed and widely applied in the prior art. Therefore, this application will not elaborate on the specific internal structure and independent operating mechanism of each device.

[0077] The workflow of a system for increasing high-pressure steam production in sulfuric acid production is as follows:

[0078] Ambient air first enters the drying tower 14 to remove moisture and form dry air. The dry air is drawn in and pressurized by the main fan 16 and then sent to the air preheater 12.

[0079] In the air preheater 12, dry air is heated by low-pressure saturated steam from a low-pressure waste heat boiler and then enters the sulfur incinerator 5 as high-temperature combustion air.

[0080] Liquid sulfur is fully combusted with preheated dry air in a sulfur incinerator to generate high-temperature flue gas containing sulfur dioxide.

[0081] High-temperature flue gas enters the high-pressure waste heat boiler, heating the high-pressure boiler feedwater that has been preheated by the high-pressure boiler feedwater heater 4, and producing high-pressure saturated steam as a byproduct. Due to the significant increase in feedwater temperature, more steam can be generated per unit of flue gas, thus increasing the production of high-pressure steam.

[0082] After conversion, the flue gas enters the low-temperature heat recovery tower 1, where the waste heat is absorbed by the circulating concentrated sulfuric acid. The high-temperature sulfuric acid flows out of the low-temperature heat recovery tower 1 and enters the low-pressure waste heat boiler, producing low-pressure steam as a byproduct. Subsequently, it is divided into two streams through a diversion loop:

[0083] In the circulating flow path, most of the sulfuric acid enters diluter 3, is diluted with water, and then returns to the low-temperature heat recovery tower 1 to maintain a stable acid concentration.

[0084] In the heat exchange flow path, a small portion of sulfuric acid flows sequentially through the low-pressure boiler feedwater heater 7, the high-pressure boiler feedwater heater 4, and the demineralized water preheater 8, cooling to 70°C in stages, while simultaneously preheating the low-pressure feedwater, high-pressure feedwater, and demineralized water respectively.

[0085] The low-pressure steam generated by the low-pressure waste heat boiler is divided into two paths: one path enters the air preheater 12 to heat and dry the air; the other path enters the flue gas preheater 13 to heat the flue gas at the outlet of the low-temperature heat recovery tower 1, and then sends it to the inlet of the conversion system 15.

[0086] Sulfuric acid, cooled to approximately 70°C by the demineralized water preheater 8, is fed into the secondary absorption tower circulation unit, which includes the secondary absorption tower circulating acid tank 9, the secondary absorption tower acid cooler 10, and the secondary absorption tower body 11. Because the inlet acid temperature has been significantly reduced, the required circulating cooling water volume for the secondary absorption tower acid cooler 10 is significantly reduced, thus lowering water and electricity consumption.

[0087] A method of using a system for increasing high-pressure steam production in a sulfuric acid production process, as described above, includes the following steps:

[0088] S1. High-temperature sulfuric acid from low-temperature heat recovery tower 1 is introduced into low-pressure steam generation unit 2, and low-pressure saturated steam is produced by heat exchange, and cooled sulfuric acid is obtained.

[0089] S2. Divide the cooled sulfuric acid into two parts:

[0090] The first part is sent to diluent 3, diluted with process water and then returned to low-temperature heat recovery tower 1 to maintain the sulfuric acid concentration in the tower at around 98%.

[0091] The second part is fed into the heat exchange path for waste heat recovery;

[0092] S3. The sulfuric acid entering the heat exchange path is sequentially passed through the low-pressure boiler feed water heater 7, the high-pressure boiler feed water heater 4, and the demineralized water preheater 8 for three-stage heat exchange: the low-pressure boiler feed water is preheated in the low-pressure boiler feed water heater 7; the high-pressure boiler feed water is preheated in the high-pressure boiler feed water heater 4; and the demineralized water is preheated in the demineralized water preheater 8. At the same time, the sulfuric acid is cooled to 70°C in each stage and then transported to the second absorption tower circulation unit.

[0093] S4. Introduce the low-pressure steam generated by the low-pressure steam generator unit 2 into the steam reuse unit, and then pass it into the air preheater 12 and the flue gas preheater 13 respectively:

[0094] Combustion air from drying tower 14 is heated to 160°C–170°C before entering sulfur incinerator 5; flue gas discharged from low-temperature heat recovery tower 1 is heated to 160°C–170°C before entering conversion system 15.

[0095] S5. The high-pressure boiler feedwater, which has been preheated by the high-pressure boiler feedwater heater 4, is sent to the economizer of the conversion system 15 for preheating and then sent to the high-pressure steam generator 6 to generate high-pressure saturated steam using the high-temperature flue gas at the outlet of the sulfur incinerator 5.

[0096] S6. After the high-pressure saturated steam is drawn out, it is sent to the conversion system 15 to generate high-pressure superheated steam for use by the steam turbine generator set or process.

[0097] In step S3, the temperature of the sulfuric acid cooled by the demineralized water preheater shall not exceed 70°C, and in step S4, the temperature of the air heated by the air preheater shall not be lower than 160°C.

[0098] The system provided in this application has the following significant advantages:

[0099] By using a high-pressure feedwater heat exchanger to preheat the high-pressure boiler feedwater with cooled sulfuric acid, the feedwater temperature is increased. At the same time, the flue gas and air are heated by a flue gas preheater and an air preheater, increasing the flue gas temperature and increasing the heat in the steam superheating section of the conversion system. This achieves the transfer of heat from the sensible heat section (low-temperature heat) to the latent heat section (high-temperature heat). Without increasing the fuel consumption of the sulfur incinerator, the high-pressure steam output per ton of acid is increased from about 1.28 tons in the traditional process to 1.45-1.50 tons, effectively enhancing the plant's self-generating capacity.

[0100] By fully recovering low-temperature waste heat and reducing circulating water consumption, all the waste heat from the 131℃→70℃ acid side that originally needed to be cooled by circulating water is used to preheat the high-pressure / low-pressure boiler feedwater and demineralized water, thus avoiding heat waste. At the same time, the load on the second absorption tower acid cooler is significantly reduced, the amount of circulating cooling water used is reduced, and the investment in auxiliary equipment is reduced.

[0101] To achieve high-value utilization of low-pressure steam, the low-pressure steam produced by low-pressure waste boilers is used to heat combustion air and flue gas before conversion. By utilizing steam condensation heat exchange, the heat exchange efficiency is greatly increased, the heat exchange area required for heat exchange is greatly reduced, and the equipment cost is significantly reduced.

[0102] To improve system safety and economy, the air preheater and flue gas preheater use low-pressure steam as an indirect heating medium, avoiding direct contact between concentrated sulfuric acid and the heated fluid. The equipment can be made of carbon steel, which significantly reduces investment costs and eliminates the risk of acid leakage.

[0103] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0104] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A system for increasing the output of high-pressure steam in the sulfuric acid production process, characterized in that, include: Low-temperature heat recovery tower (1); The low-pressure steam generating unit (2) is connected to the sulfuric acid outlet of the low-temperature heat recovery tower (1) and is used to generate low-pressure steam byproduct from high-temperature sulfuric acid and output cooled sulfuric acid. The diversion loop is configured to divide the cooled sulfuric acid into a circulation path and a heat exchange path; the diluent (3) is connected to the circulation path and is used to dilute part of the cooled sulfuric acid and return it to the low-temperature heat recovery tower (1); the heat exchange path is arranged in series with multiple heat exchangers for cooling another part of the cooled sulfuric acid in stages; wherein, at least one high-pressure boiler feedwater heater (4) is included among the multiple heat exchangers for preheating the high-pressure boiler feedwater; The steam reuse unit, whose heat source is the low-pressure steam produced by the low-pressure steam generating unit (2), is used to heat the combustion air entering the sulfur incinerator (5) and the flue gas entering the conversion system (15); the high-pressure steam generating device (6), connected to the sulfur incinerator (5), is used to receive the high-pressure boiler feedwater preheated by the economizer of the high-pressure boiler feedwater heater (4) and the conversion system (15) and generate high-pressure saturated steam; the conversion system (15) is used to receive the high-pressure saturated steam and the flue gas.

2. The system for increasing high-pressure steam production in the sulfuric acid production process according to claim 1, characterized in that, The plurality of heat exchangers include a low-pressure boiler feed water heater (7), a high-pressure boiler feed water heater (4), and a demineralized water preheater (8) connected in sequence. The cooled sulfuric acid flows through the low-pressure boiler feed water heater (7), the high-pressure boiler feed water heater (4), and the demineralized water preheater (8) in sequence for stage-by-stage cooling.

3. The system for increasing high-pressure steam production during sulfuric acid production according to claim 2, characterized in that, The sulfuric acid cooled by the demineralized water preheater (8) is conveyed to the secondary absorption tower circulation unit; the secondary absorption tower circulation unit includes: The second suction tower circulating acid tank (9) has its inlet connected to the sulfuric acid outlet of the demineralized water preheater (8); The inlet of the second-suction tower acid cooler (10) is connected to the outlet of the second-suction tower circulating acid tank (9), and circulating water is introduced into the second-suction tower acid cooler (10) as a cooling medium. The main body (11) of the second suction tower has its inlet connected to the outlet of the acid cooler (10) of the second suction tower, and its bottom acid outlet connected to the inlet of the circulating acid tank (9) of the second suction tower, thus forming an acid circulation loop.

4. The system for increasing high-pressure steam production during sulfuric acid production according to claim 1, characterized in that, The steam reuse unit includes an air preheater (12) and a flue gas preheater (13). The air preheater (12) is installed on the air pipeline between the outlet of the drying tower (14) and the combustion air inlet of the sulfur incinerator (5); The flue gas preheater (13) is located on the flue gas pipeline between the flue gas outlet of the low-temperature heat recovery tower (1) and the inlet of the conversion system (15).

5. The system for increasing high-pressure steam production in the sulfuric acid production process according to claim 4, characterized in that, The low-pressure steam generating unit (2) is a low-pressure waste boiler, and its low-pressure steam outlet is connected to the steam inlet of the air preheater (12) and the flue gas preheater (13), respectively.

6. The system for increasing high-pressure steam production in the sulfuric acid production process according to claim 5, characterized in that, The high-pressure steam generating device (6) is a waste heat boiler. Its flue gas inlet is connected to the high-temperature flue gas outlet of the sulfur incinerator (5), and its feed water inlet receives the high-pressure boiler feed water preheated by the high-pressure boiler feed water heater (4) and the economizer of the conversion system (15).

7. The system for increasing high-pressure steam production in the sulfuric acid production process according to claim 6, characterized in that, It also includes a main fan (16), whose inlet is connected to the outlet of the drying tower (14) and whose outlet is connected to the inlet of the air preheater (12).

8. The system for increasing high-pressure steam production in the sulfuric acid production process according to claim 7, characterized in that, The heat exchange elements of the air preheater (12) and the flue gas preheater (13) are made of carbon steel; the steam condensate produced by the air preheater (12) and the flue gas preheater (13) is returned to the deaerator.

9. A method of using a system for increasing high-pressure steam production in sulfuric acid production as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. High-temperature sulfuric acid from the low-temperature heat recovery tower (1) is introduced into the low-pressure steam generation unit (2), and low-pressure steam is produced by heat exchange to obtain cooled sulfuric acid; S2. The cooling sulfuric acid is divided into two parts. The first part is sent to the diluent (3) for dilution and returned to the low-temperature heat recovery tower (1) for recycling. The second part is sent to the heat exchange path for heat recovery. S3. The sulfuric acid entering the heat exchange path is sequentially passed through the low-pressure boiler feed water heater (7), the high-pressure boiler feed water heater (4), and the demineralized water preheater (8) for three-stage heat exchange, so as to achieve the step-by-step cooling of sulfuric acid and the preheating of boiler feed water and demineralized water. S4. The low-pressure steam generated by the low-pressure steam generating unit (2) is introduced into the steam reuse unit to heat the combustion air entering the sulfur incinerator (5) and the flue gas entering the conversion system (15), respectively. S5. The high-pressure boiler feedwater, which has been preheated by the high-pressure boiler feedwater heater (4), is sent to the economizer of the conversion system (15) for preheating and then sent to the high-pressure steam generator (6) to generate high-pressure saturated steam using the high-temperature flue gas of the sulfur incinerator (5). S6. Introduce the high-pressure saturated steam and the preheated flue gas together into the conversion system (15).

10. The method of use according to claim 9, characterized in that, In step S3, the temperature of sulfuric acid cooled by the demineralized water preheater (8) is not higher than 70°C, and in step S4, the temperature of air heated by the air preheater (4) is not lower than 160°C.

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