A process for desulfurization and purification of converter gas

Abstract

The present application relates to a kind of converter gas desulfurization purification process.Converter gas raw gas is first treated by TSA, then enters hydrolysis desulfurization tower for desulfurization;Desulfurized gas enters deoxidation reactor for deoxidation, and the purified gas after deoxidation is divided into two parts, one part is pressurized by circulating fan and goes to beat cycle;One part is cooled to 40 DEG C after converter gas heat exchange, water cooling and goes to decarburization;The gas after decarburization is directly into desulfurization tower to remove trace COS, CS2, then enters fine desulfurization tower to remove trace mercaptan and dimethyl disulfide.By this process, it can meet the technical requirements of sulfur content less than 0.1mg / Nm 3 , oxygen content is less than 30ul / L, the process has the characteristics of simple flow, high desulfurization purification degree, low investment and operating cost.

Description

Technical Field

[0001] This invention relates to a desulfurization and purification process for converter gas. It removes and purifies impurities such as S, Cl, F, and O2 from converter gas, producing gas that meets the requirements for use as a raw material in the production of chemical products such as methanol or ethylene glycol, falling under the category of coal chemical industry. Background Technology

[0002] Converter gas is a mixture of carbon monoxide and a small amount of carbon dioxide produced during the converter steelmaking process when carbon in molten iron reacts with blown-in oxygen at high temperatures. Its main components are shown in Table 1, containing approximately 50% CO. It has a certain calorific value and can be used as fuel gas. If used as a chemical feedstock, extracting the CO and combining it with coke oven gas for the production of methanol or ethylene glycol can create greater value. Regardless of whether it is used as fuel or a chemical feedstock, desulfurization and purification are prerequisites for its utilization. As shown in Table 1, converter gas contains a large amount of impurities, especially high levels of sulfides. When used as a chemical feedstock, excessive sulfides can poison and deactivate synthesis catalysts, and excessive oxygen can affect the activity of subsequent PSA catalysts. Therefore, it is generally required that the oxygen content of converter gas be reduced to 30 μL / L and the sulfur content to 0.1 mg / Nm³. 3 .

[0003] Table 1. Converter Gas Components

[0004] Components mol% HF (as fluorine) <![CDATA[≤1mg / Nm 3 ]]> <![CDATA[H2]]> 2 As <![CDATA[≤1mg / Nm 3 ]]> <![CDATA[N2]]> 23.87 <![CDATA[CH3SSCH3,mg / Nm³]]> 1.2 CO 50 <![CDATA[H2S,mg / Nm³]]> 1.3 <![CDATA[CO2]]> 22.5 COS, mg / Nm³ 10.2 AR 0 <![CDATA[CH3SH,mg / Nm³]]> 0.1 <![CDATA[CH4]]> 0.07 <![CDATA[C4H4S,mg / Nm³]]> 0.1 <![CDATA[C2H4]]> 0.01 <![CDATA[CS2,mg / Nm³]]> 2 <![CDATA[C2H6]]> 0.01 Tar and dust <![CDATA[≤1mg / Nm 3 ]]> <![CDATA[C3H6]]> 0.01 <![CDATA[PH3]]> <![CDATA[≤1mg / Nm 3 ]]> <![CDATA[C3H8]]> 0.01 1,3-Butadiene 0.01 cyclopentadiene 0.01 <![CDATA[O2]]> 1.5

[0005] The desulfurization method for converter gas mainly uses the traditional "sandwich" process, which involves first removing H2S at room temperature, then raising the temperature to 80-90℃ for COS hydrolysis to convert COS into H2S, then cooling back to room temperature to remove the generated H2S. This method has two drawbacks: ① The "heating and cooling problem": the initial heating followed by cooling increases energy consumption and operating costs. ② When the oxygen content of the converter gas is high, high-temperature hydrolysis easily leads to sulfation, significantly reducing the lifespan of the hydrolysis catalyst.

[0006] Typical noble metal deoxidation catalysts such as Pd / Al2O3 and Pt / Al2O3 generally operate at deoxidation temperatures around 170℃ in CO-rich atmospheres, with deep deoxidation temperatures exceeding 200℃. Sulfide-type deoxidizers like MoS-CoS-Al2O3 typically operate at temperatures above 220℃. When using these catalysts, if the inlet oxygen concentration reaches 1.0%, the exothermic deoxidation reaction can raise the bed temperature above 300℃, leading to exothermic side reactions that cause runaway temperatures and catalyst deactivation through sintering. The carbon produced by these side reactions can also clog catalyst pores, causing further deactivation. Therefore, catalysts such as Pd / Al2O3, Pt / Al2O3, and MoS-CoS-Al2O3 are unsuitable for deoxidation of CO-rich gases such as converter gas.

[0007] CN108977237B describes a method for deoxygenation and fine desulfurization of converter and / or blast furnace gas, including steps such as desulfurization, mixing, deoxygenation, blending, and fine desulfurization. The method involves mixing gas with a high oxygen content with qualified gas with a low oxygen content, then passing the mixed gas into a deoxygenation reactor for deoxygenation treatment to obtain qualified regenerated gas. Simultaneously, a portion of the gas is circulated through a recirculating compressor and used to mix with the gas with a high oxygen content to produce a mixed gas. This allows for real-time, continuous online deoxygenation treatment of the gas. While this patent describes the deoxygenation method, it does not specify the type of deoxygenation catalyst or reactor, nor does it provide information on deoxygenation and desulfurization precision, thus offering limited reference value for industrial applications. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, this invention provides a converter gas desulfurization and purification process, the specific technical solution of which is as follows:

[0009] A certain amount of converter gas first undergoes TSA treatment, then, after exchanging heat with the deoxidized gas through heat exchanger E-101 to raise its temperature to 50-60℃, it enters the hydrolysis desulfurization tower R-101 to remove H2S and COS from the gas. The desulfurized gas then passes through the converter gas start-up heater E-102 before entering the deoxidation reactor R-102. Considering the high and fluctuating oxygen content of the converter gas, a partial recirculation process is adopted to reduce the inlet oxygen content. The deoxidation reactor is an internal heat exchange type isothermal reactor, which reduces bed temperature rise and decreases the amount of circulating gas. To ensure stable long-term operation of the deoxidizer at lower temperatures, secondary lines are installed at the inlet and outlet of the circulating fan to control the inlet oxygen content to approximately 0.75%, and the deoxidation outlet temperature to no higher than 160℃. The recirculated gas after deoxidation in R-102 is cooled by the converter gas water cooler EC-101 and then mixed with the gas after fine desulfurization in R-101, with the deoxidation inlet temperature controlled at 55℃. Part of the deoxygenated gas is cooled by heat exchange in the purified gas heat exchanger EC-101 and then pressurized by the circulating fan K-101 for recirculation; another part is cooled by heat exchange with the raw gas from the TSA converter gas in the converter gas heat exchanger E-101, and then cooled to 40°C by the water cooler EC-102 before decarbonization. MDEA decarbonization is used. The decarbonized gas still contains a small amount of sulfides, failing to meet the requirement of total sulfur less than 0.1 mg / Nm³. 3 The technical requirements necessitate further decarbonization treatment. The decarbonized gas directly enters desulfurization tower R-103, which contains W312 desulfurizing agent to remove trace amounts of COS and CS2. Then, it enters fine desulfurization tower R-104. R-104 has two parallel reactors, R104A and R104B, containing W106 desulfurizing agent to remove trace amounts of mercaptans and dimethyl disulfide. The W106 fine desulfurizing agent is regenerated and reused. Regeneration conditions: device desorption, regeneration gas flow rate 3000-5000 Nm³. 3 The regeneration process involves a regeneration temperature of 200℃, a regeneration cycle of 15-20 days, and a regeneration time of 48 hours per cycle. After treatment using this process, the sulfur content can be reduced to a minimum of 0.1 mg / Nm³. 3 The technical requirement is an oxygen content of less than 30 μL / L. The purified gas after desulfurization and deoxygenation is then sent to the next stage.

[0010] Beneficial Effects: ⑴ A new multi-stage hydrolysis-conversion-absorption desulfurization process: Traditional converter gas desulfurization mainly uses a "sandwich" process, where H2S is first removed at room temperature, then the temperature is raised to 60-90℃ for COS hydrolysis, converting COS to H2S. The temperature is then lowered back to room temperature to remove the generated H2S. This process has two drawbacks: ① The "heating and cooling problem": Heating up and then cooling down increases energy consumption and operating costs. ② Under conditions of high oxygen content in converter gas, traditional hydrolysis catalysts are prone to sulfation poisoning, significantly reducing their lifespan. The new process uses a hydrolysis catalyst resistant to high oxygen content, overcoming the sulfation problem of traditional catalysts. Simultaneously, a matching desulfurizing agent that can be used at higher temperatures is employed. This desulfurizing agent can be used at the same temperature as the hydrolysis catalyst. The multi-stage hydrolysis desulfurization process eliminates the need for repeated heating and cooling, greatly reducing energy consumption. The deoxygenated gas undergoes final desulfurization using W106 mercaptan and thioether fine desulfurizer, which removes trace amounts of residual mercaptan, thioether, and other difficult-to-remove sulfides, ensuring that the total sulfur content after fine desulfurization is <0.1 mg / Nm³. 3 To avoid catalyst poisoning and deactivation in downstream processes. ⑵ Novel non-precious metal sulfur-resistant deoxidizers: Conventional precious metal deoxidizers such as Pd / Al2O3 and Pt / Al2O3 typically operate at deoxidation temperatures around 170℃ in CO-rich atmospheres, with deep deoxidation temperatures exceeding 200℃; MoS-CoS-Al2O3-type sulfur-oxidizing deoxidizers require hydrogen supplementation and generally operate at temperatures above 220℃. When using these two types of deoxidizers, if the inlet oxygen concentration reaches 1.0%, the exothermic deoxidation reaction can cause the bed temperature to exceed 300℃, leading to side reactions such as CO disproportionation, resulting in bed overheating and carbon buildup, causing rapid catalyst deactivation. Wuhan Kelin has innovatively developed a non-precious metal sulfur-resistant deoxidizer. This catalyst can catalyze the reaction of CO and O2 at relatively low temperatures of 80-250℃, reducing oxygen to less than 30ul / L. The deoxidation process does not require additional hydrogen supplementation and exhibits good sulfur resistance. Its price is only one-tenth that of precious metal deoxidizers, significantly reducing equipment investment. (3) Novel uniform temperature reactor and low temperature circulation control technology: In view of the large fluctuation range of oxygen content in converter gas, with the highest content exceeding 1.5% and the adiabatic temperature rise reaching 150~170℃, an internal heat exchange uniform temperature reactor is adopted. After deoxygenation, the oxygen content of the gas at the inlet is controlled by a low temperature circulation control device to be below 0.75%, so that the temperature of the deoxygenation bed does not exceed 200℃, maximizing the service life of the catalyst and ensuring the safe and stable operation of the device. At the same time, the waste heat of the converter gas deoxygenation is fully utilized to heat the raw material gas. According to the change of oxygen content, the circulation gas volume is intelligently adjusted by frequency conversion, which saves both heat energy and power consumption of the circulation machine. Attached Figure Description

[0011] Figure 1 This is a flow chart of the converter gas desulfurization and purification process.

[0012] In the diagram: E101 and E102 are heat exchangers; EC101 and EC102 are water coolers; K101 is a circulating fan; R101 is a hydrolysis desulfurization tower; R102 is a deoxygenation reactor; R103 is a desulfurization tower; and R104A / B are fine desulfurization towers. Detailed Implementation

[0013] The converter gas first undergoes TSA treatment, then exchanges heat with the deoxygenated gas in heat exchanger E-101 to raise its temperature to 50-60℃ before entering the hydrolysis desulfurization tower R-101. The hydrolysis catalyst, using either ordinary or layered loading methods, is used to remove H2S and COS from the gas. The hydrolysis catalyst type is either ordinary or high-oxygen resistant, and the desulfurizing agent is either ordinary or high-temperature resistant. The desulfurized gas then passes through converter gas heat exchanger E-102 before entering the deoxygenation reactor R-102. The deoxygenation reactor is an adiabatic, U-shaped, or tube-type isothermal reactor with internal heat exchange. To ensure long-term stable operation of the deoxygenating agent at lower temperatures, secondary lines are installed at the inlet and outlet of the circulating fan to control the inlet oxygen content to approximately 0.75%, and the deoxygenation outlet temperature to no higher than 160℃. The recirculated gas after deoxidation in R-102 is cooled by the converter gas water cooler EC-101 and then mixed with the gas after fine desulfurization in R-101. The deoxidation inlet temperature is controlled at 55℃. Deoxidation uses W902B deoxidizer developed by Kolin Company to remove oxygen from the converter gas. This deoxidizer is a non-precious metal deoxidizer. Part of the deoxidized gas is cooled by heat exchange in the purified gas heat exchanger EC-101 and then pressurized by the circulating fan K-101 for recirculation. Another part is cooled by heat exchange in the converter gas heat exchanger E-101 with the raw gas from the TSA converter, and then cooled to 40℃ in the water cooler EC-102 before decarbonization. Decarbonization uses MDEA. The decarbonized gas still contains a small amount of sulfides, failing to meet the requirement of total sulfur less than 0.1 mg / Nm³. 3 The technical requirements necessitate further decarbonization treatment. The decarbonized gas directly enters desulfurization tower R-103, which contains W312 desulfurizing agent to remove trace amounts of COS and CS2. This desulfurizing agent uses Ti-Mg as a carrier and dinuclear sulfonated cobalt phthalocyanine sulfonate ammonium and triethanolamine as active components. The gas then enters the fine desulfurization tower R-104. R-104 has two parallel reactors, R104A and R104B, containing W106 desulfurizing agent to remove trace amounts of mercaptans and dimethyl disulfide. The W106 fine desulfurizing agent is regenerated for reuse. Regeneration conditions: device desorption, regeneration gas flow rate 3000-5000 Nm³. 3 / h, regeneration temperature 200℃, regeneration cycle 15-20 days / time, regeneration time 48 hours / time, the purified gas after desulfurization and deoxygenation goes to the next stage. The properties of the raw materials are shown in Table 2;

[0014] Table 2. Main impurities and their contents in raw materials

[0015] HF (as fluorine) <![CDATA[0.5mg / Nm 3 ]]> As <![CDATA[0.6mg / Nm 3 <!-- 3 -->]]> <![CDATA[CH3SSCH3,mg / Nm³]]> 1.2 <![CDATA[H2S,mg / Nm³]]> 1.3 COS, mg / Nm³ 10.2 <![CDATA[CH3SH,mg / Nm³]]> 0.1 <![CDATA[C4H4S,mg / Nm³]]> 0.1 <![CDATA[CS2,mg / Nm³]]> 2 Oxygen content, % 1.5 <![CDATA[PH3]]> <![CDATA[≤1mg / Nm 3 ]]>

[0016] Examples 1-4 were obtained by using different hydrolysis catalysts, desulfurizing agents and hydrolysis desulfurization tower filling methods, and the effects of the examples are shown in Table 3.

[0017] Table 3. Purification effects of different embodiments

[0018]

[0019] Table 3 shows that a step-by-step filling method with shorter intervals is better. Simultaneously using a high-temperature resistant desulfurizer and a high-oxygen resistant hydrolysis catalyst significantly improves the desulfurization effect; in Example 2, the H2S+COS content at the R101 outlet was only 0.05 g / Nm³. 3 The preferred deoxidation catalyst is a non-precious metal Cu-Mn / Al2O3 series deoxidizer, and the use of a tube-and-tube isothermal reactor provides better deoxidation performance than an adiabatic reactor using precious metal Pt / Al2O3. Using R103 / R104 as a control agent can reduce total sulfur to less than 0.1 mg / Nm³. 3 .

Claims

1. A converter gas desulfurization and purification process, characterized in that... Includes the following steps: (1) The converter gas feedstock first undergoes TSA treatment, and then is heated to 50-60℃ through heat exchange before entering the hydrolysis desulfurization tower (R-101) for desulfurization; (2) The desulfurized gas enters the deoxygenation reactor (R-102) for deoxygenation. The purified gas after deoxygenation is divided into two parts. One part is pressurized by the circulating fan (K-101) and then circulated. The other part is cooled to 40°C by the converter gas heat exchange and water cooling before decarbonization. (3) The decarbonized gas is directly fed into the desulfurization tower (R-103) to remove trace amounts of COS and CS2, and then into the fine desulfurization tower (R-104) to remove trace amounts of mercaptans and dimethyl disulfide; The hydrolysis desulfurization tower is filled in stages, with hydrolysis catalyst and desulfurizing agent filled at intervals of 30-80cm from bottom to top; The hydrolysis catalyst is a high-oxygen resistant catalyst; The deoxygenation reactor is filled with a non-precious metal sulfur-resistant deoxygenation catalyst with Cu-Mn as the active component and alumina as the support. The desulfurization tower (R-103) is filled with a desulfurizing agent with Ti-Mg as the carrier and ammonium dinuclear sulfonated cobalt phthalocyanine sulfonate and triethanolamine as active components.

2. The process as described in claim 1, characterized in that: The deoxygenation reactor adopts an internal heat exchange type U-tube isothermal reactor or a tubular isothermal reactor.

3. The process as described in claim 1, characterized in that: The ratio of circulating gas to raw material gas is 0~1:

1. The circulating fan (K-101) adopts low temperature circulation control, which can automatically adjust the circulating gas flow rate according to the inlet oxygen content and control the inlet oxygen content of the deoxygenation reactor to not exceed 0.75%.

4. The process as described in claim 1, characterized in that: Decarbonization was performed using the MDEA decarbonization method.

5. The process as described in claim 1, characterized in that: The fine desulfurization tower (R-104) consists of two parallel towers with the same volume capacity.

6. The process as described in claim 5, characterized in that: The fine desulfurization tower (R-104) is filled with fine desulfurization agent using activated carbon as a carrier; the fine desulfurization agent is regenerated and reused. Regeneration conditions: device desorption is used, and the regeneration gas volume is 3000-5000 Nm³. 3 / h, regeneration temperature 200℃, regeneration cycle 15-20 days / time, regeneration time 48 hours / time.

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