A dry absorption water balance control process method with low-temperature heat recovery

Abstract

The present invention relates to a process method for controlling the dry absorption water balance with low-temperature heat recovery, which includes a drying unit, a low-temperature waste heat recovery unit, a second absorption circulating acid concentration adjustment module, a desorption tower, a drying acid buffer tank and an underground tank arranged in sequence. Beneficial effects: The present invention realizes the problems that when converting low-concentration sulfur dioxide and starting and stopping the acid-making system for smelting flue gas containing converter blowing, the dry absorption process cannot maintain the production of 98% acid water balance, and for the acid-making of smelting flue gas containing converter blowing, due to the periodic operation of the converter, the large fluctuations in the flue gas volume and sulfur dioxide concentration cause changes in the extraction amount of the drying acid, resulting in a low acidity of HRS in a short time and corroding equipment and pipelines. The present invention uses the buffer tank, the underground tank and the pipelines to realize the stable control of the acid concentration of HRS and the second absorption, improves the steam output and outputs the excess drying acid in the form of 93% acid at any time, and solves the water balance problem of the dry absorption process.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas treatment and chemical engineering, and particularly relates to a dry absorption water balance control process method with low-temperature heat recovery. Background Art

[0002] In the production process of sulfuric acid from various sulfur-containing raw materials, a large amount of chemical energy is released during the three main processes of combustion of sulfur-containing raw materials, oxidation of sulfur dioxide, and absorption of sulfur trioxide. There are already relatively mature processes for the utilization of high- and medium-temperature waste heat generated during the combustion of sulfur-containing raw materials and the oxidation of sulfur dioxide. During the drying and absorption processes in sulfuric acid plants, a large amount of reaction heat, condensation heat, and dilution heat are generated, and the utilization of this part of the heat is greatly limited due to the strong corrosiveness of high-temperature concentrated sulfuric acid. Generally, it is removed by circulating cooling water and wasted.

[0003] Generally, in sulfuric acid plants for smelting flue gas, the heat generated from high-temperature waste heat and medium-temperature waste heat has been utilized to produce medium-pressure steam, but the low-temperature waste heat in the drying and absorption parts has not been effectively developed and utilized. At present, low-temperature waste heat recovery technology has been widely applied in sulfuric acid plants using sulfur, and good economic benefits have been achieved.

[0004] The low-temperature heat recovery system uses an alloy that is resistant to high-temperature concentrated sulfuric acid. When the temperature of the alloy is 200 °C and the acid concentration is 99.0 - 99.7%, the corrosion rate is 0.05 mm / a. When the acid concentration is lower than 98%, the alloy will corrode rapidly.

[0005] In the conventional acid series connection process of the drying acid in the low-temperature heat recovery system, a part of the drying acid is connected in series to the diluter of the low-temperature heat recovery system, and the other part is sent from the outlet of the drying circulation pump to the desorption tower for desorption through liquid level control. The acid after desorption directly flows into the second absorption circulation pump tank. When the sulfur dioxide concentration is low during system startup and shutdown and when operating improperly, the excess drying acid will cause the acid concentration in the low-temperature heat recovery system to decrease, corroding equipment and pipelines.

[0006] There are great differences in the utilization of low-temperature waste heat between sulfuric acid plants for smelting flue gas with low-concentration sulfur dioxide and fluctuating flue gas volume and concentration and sulfuric acid plants using sulfur. For sulfuric acid production from smelting flue gas with low-concentration sulfur dioxide and fluctuating flue gas volume and concentration, due to the existence of a flue gas purification system, the sulfur dioxide gas entering the drying tower is saturated with water, making it impossible to balance the water balance in the entire drying and absorption system when the system load fluctuates. The excess drying acid enters the second absorption, resulting in a low acid concentration in the second absorption. It enters the low-temperature heat recovery system through two-stage spraying, reducing the circulating acid concentration in the low-temperature heat recovery system and corroding equipment and pipelines.

[0007] At present, domestic low-temperature heat recovery systems have no application performance in sulfuric acid plants for smelting flue gas with low sulfur dioxide and large fluctuations in flue gas volume and concentration. Summary of the Invention

[0008] The object of the present invention is to provide a dry absorption water balance control process method with low-temperature heat recovery, which solves the technical problems that the existing low-temperature waste heat has not been effectively developed and utilized, resulting in resource waste, and the water balance of the entire dry absorption system cannot be balanced when the system load fluctuates, affecting the safety of equipment. The present invention is achieved through the following solutions.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is: a dry absorption water balance control process method with low-temperature heat recovery, characterized in that it includes a drying unit, a low-temperature waste heat recovery unit, a second absorption circulating acid concentration adjustment module, a desorption tower, a drying acid buffer tank, and an underground tank arranged in sequence;

[0010] Drying unit: used for drying the external flue gas, and the output end of the drying unit is respectively connected to the low-temperature waste heat recovery unit and the desorption tower;

[0011] Low-temperature waste heat recovery unit: recovering and utilizing the low-grade heat energy and supplying it to the second absorption circulating acid concentration adjustment module;

[0012] Drying acid buffer tank: the input end is connected to the desorption tower, the outlet pipe is connected to the second absorption circulating acid concentration adjustment module, and it flows into the second absorption pump tank by using the head difference. An overflow port is arranged on the upper side of the drying acid buffer tank, and the overflow port flows into the underground tank.

[0013] Further, the dried acid after desorption flows into the drying acid buffer tank by using the head difference.

[0014] Further, a regulating valve is arranged between the drying acid buffer tank and the pipeline of the second absorption pump tank to adjust the amount of dried acid flowing into the second absorption pump tank, so as to achieve the purpose of controlling the concentration of the second absorption circulating acid.

[0015] Further, a drying acid production acid pipeline is arranged at the outlet of the underground tank, and a regulating valve is arranged on the pipeline to adjust the liquid level of the underground tank.

[0016] Further, the material of the buffer tank is acid-resistant high-silicon stainless steel.

[0017] The technical effect of the present invention is as follows:

[0018] 1. For the sulfuric acid production device and sulfur-burning sulfuric acid production device with low-concentration sulfur dioxide, and the flue gas volume and concentration fluctuations, when the low-temperature waste heat recovery system has load fluctuations and operation errors, the drying acid buffer tank can balance the concentration of the second absorption circulating acid. The excess dried acid can be produced as finished acid, solving the water balance problem. At the same time, using the dried acid as the second absorption circulating acid concentration, without adding water for adjustment, minimizing the amount of drying acid entering the low-temperature heat recovery system as much as possible, increasing the steam output.

[0019] 2. The technical solution for achieving the object of the present invention is as follows: A part of the dry acid is introduced into the diluter of the low-temperature heat recovery system in series, and the other part of the dry acid is sent from the outlet of the dry circulation pump to the desorption tower for desorption through liquid level control. The desorbed dry acid flows into the provided buffer tank, and then flows from the bottom of the buffer tank into the secondary absorption circulation tank. An automatic valve is set in the pipeline, and it is automatically adjusted according to the concentration of the circulating acid in the secondary absorption circulation tank. When the load fluctuates, the amount of dry acid is balanced by the buffer tank. When the liquid level reaches the overflow port, it automatically flows into the underground tank and is produced as finished acid. When the system water is unbalanced, the dry buffer tank is used to balance the impact on the reduction of the circulating acid concentration in the secondary absorption and low-temperature heat recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the process flow diagram of the present invention.

[0021] Reference numerals: 1 - drying unit; 2 - low-temperature waste heat recovery unit; 3 - secondary absorption circulating acid concentration adjustment module; 4 - desorption tower; 5 - dry acid buffer tank; 6 - underground tank. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Refer to the attached Figure 1 , a dry absorption and water balance control process method with low-temperature heat recovery, characterized in that it includes a drying unit 1, a low-temperature waste heat recovery unit 2, a secondary absorption circulating acid concentration adjustment module 3, a desorption tower 4, a dry acid buffer tank 5, and an underground tank 6 arranged in sequence;

[0023] Drying unit 1: It is used for drying the external flue gas, and the output end of the drying unit is respectively connected to the low-temperature waste heat recovery unit 2 and the desorption tower 4;

[0024] Low-temperature waste heat recovery unit 2: Recovers and utilizes the low-grade heat energy and supplies it to the secondary absorption circulating acid concentration adjustment module 3;

[0025] Dry acid buffer tank 5: The input end is connected to the desorption tower 4, and the outlet pipe is connected to the secondary absorption circulating acid concentration adjustment module 3. It flows into the secondary absorption pump tank by using the head difference. An overflow port is arranged on the upper side of the dry acid buffer tank 5, and the overflow port flows into the underground tank.

[0026] A specific embodiment of this solution is that the desorbed dry acid flows into the dry acid buffer tank 5 by using the head difference. A regulating valve is arranged between the dry acid buffer tank 5 and the pipeline of the secondary absorption pump tank to adjust the amount of dry acid flowing into the secondary absorption pump tank, so as to achieve the purpose of controlling the concentration of the secondary absorption circulating acid. A dry acid production pipeline is arranged at the outlet of the underground tank 6, and a regulating valve is arranged on the pipeline to adjust the liquid level of the underground tank.

[0027] A specific embodiment of this solution is that the dry acid buffer tank 5 is made of acid-resistant high-silicon stainless steel.

[0028] In a specific embodiment of this solution, for the sulfuric acid production plants using smelting flue gas with low-concentration sulfur dioxide, fluctuating flue gas volume and concentration, and the sulfuric acid production plant using sulfur, when the low-temperature waste heat recovery system has load fluctuations and operation errors, the drying acid buffer tank can balance the concentration of the circulating acid in the second absorption stage. The excess drying acid can be produced as finished acid, solving the water balance problem. At the same time, using the drying acid as the concentrated circulating acid in the second absorption stage, without adding water for adjustment, and minimizing the amount of drying acid entering the low-temperature heat recovery system as much as possible, increasing the steam production.

[0029] The technical solution to achieve the object of the present invention is as follows: Part of the drying acid is introduced into the diluter of the low-temperature heat recovery system, and the other part of the drying acid is sent from the outlet of the drying circulation pump to the desorption tower for desorption through liquid level control. The desorbed drying acid flows into the provided buffer tank and then flows into the second absorption circulation tank from the bottom of the buffer tank. An automatic valve is set in the pipeline and automatically adjusted according to the concentration of the circulating acid in the second absorption circulation tank. During load fluctuations, the amount of drying acid is balanced by the buffer tank. When the liquid level reaches the overflow port, it automatically flows into the underground tank and is produced as finished acid. When using the dry buffer tank to balance the system water imbalance, it buffers the impact on the reduction of the circulating acid concentration in the second absorption and the low-temperature heat recovery.

[0030] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A dry absorption and water balance control process method with low-temperature heat recovery, characterized in that It includes a drying unit (1), a low-temperature waste heat recovery unit (2), a second absorption circulating acid concentration adjustment module (3), a desorption tower (4), a drying acid buffer tank (5), and an underground tank (6) arranged in sequence; Drying unit (1): It is used to dry the external flue gas, and the output end of the drying unit is respectively connected to the low-temperature waste heat recovery unit (2) and the desorption tower (4); Low-temperature waste heat recovery unit (2): It recovers and utilizes the low-grade heat energy and supplies it to the second absorption circulating acid concentration adjustment module (3); Drying acid buffer tank (5): Its input end is connected to the desorption tower (4), and the outlet pipe is connected to the second absorption circulating acid concentration adjustment module (3). It flows into the second absorption pump tank by using the head difference. An overflow port is arranged on the upper side of the drying acid buffer tank (5), and the overflow port flows into the underground tank; The dried acid after desorption flows into the drying acid buffer tank (5) by using the head difference. A regulating valve is arranged between the pipeline of the drying acid buffer tank (5) and the second absorption pump tank to adjust the amount of dried acid flowing into the second absorption pump tank, so as to achieve the purpose of controlling the concentration of the second absorption circulating acid.

2. A dry absorption water balance control process method with low-temperature heat recovery according to claim 1, characterized in that A drying acid production pipeline is arranged at the outlet of the underground tank (6), and a regulating valve is arranged on the pipeline to adjust the liquid level of the underground tank.

3. A dry absorption water balance control process method with low-temperature heat recovery according to claim 1, characterized in that, The drying acid buffer tank (5) is made of acid-resistant high-silicon stainless steel.

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