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Training Manual for Texaco Gasification Shift Process (Process gas flow rate: 100,000 Nm3/h) Section 1: Basic Principles of the Carbon Monoxide Shift Reaction The shift reaction between carbon monoxide and water vapor can be expressed by the following equation: CO + H2O ⇌ CO2 + H2 + Q (1) This shift reaction is exothermic and reversible; the volume of the gases remains unchanged before and after the reaction. Its reaction rate is relatively slow, and only in the presence of a catalyst does it proceed at a faster rate. I. Heat effect of the conversion reaction The conversion reaction is an exothermic reaction, and the heat released during the reaction decreases as the temperature rises. The relationship is given by: Q = 10861 – 1.44T – 0.4×10^-4T^2 + 0.08×10^-6T^3. Here, Q represents the heat released per mole of reaction (in kcal/kgmol), and T represents the temperature in K. The heat released during the reaction at different temperatures is shown in the table below: Table 1: Heat released during the conversion reaction Temperature (K): 298.16, 400, 600, 800, 1000, 1200, 1400 Heat released per kgmol: 10250, 10104, 9820, 9544, 9281, 9034, 8806 In industrial production, once the conversion furnace has reached the desired temperature and normal operation has begun, the heat released during this reaction can be utilized to maintain the continuity of the production process. II. Chemical Equilibrium in Transformation Reactions 1. Equilibrium Constant: Under certain conditions, when the rates of the forward and reverse reactions in a transformation reaction are equal, the reaction reaches an equilibrium state. The equilibrium constant is given by: Kp = (PC02 • PH2) / (Pco • PH2O) = (YC02 • YH2) / (Yco • YH2O). Here, PC02, PH2, Pco, PH2O represent the equilibrium partial pressures of each component, in atm units; while YC02, YH2, Yco, YH2O represent the equilibrium compositions of each component, in terms of mole fractions. The equilibrium constant Kp indicates the quantitative relationship between the products and reactants at equilibrium; therefore, it serves as a measure of the degree to which a chemical reaction has proceeded to completion. As can be seen from Equation (3), the larger the Kp value, that is, the greater the product of YC02 and YH2, the more complete the conversion of carbon monoxide in the feed gas. As a result, less residual carbon monoxide remains in the transformed gas at equilibrium. Since the transformation reaction is exothermic, lowering the temperature favors the shift of the equilibrium to the right; therefore, the equilibrium constant increases as the temperature decreases. There are many equations relating the equilibrium constant to temperature. The following simplified formula is commonly used: lgKp = 1914/T – 1.782 (4), where T represents temperature. The equilibrium constant values for the carbon monoxide conversion reaction at different temperatures are as follows: Temperature, °C: 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800. Kp = (PCO2 • PH2) / (PCO • PH2O): 86.51, 39.22, 20.34, 11.70, 7.311, 4.878, 3.434, 2.527, 1.923, 1.519, 1.228, 1.015. If the temperature is known, the value of Kp can be determined, thereby allowing the calculation of the equilibrium compositions at different temperatures, pressures, and gas compositions. 2 Conversion rate: The degree of conversion of carbon monoxide is usually expressed as a conversion rate, defined as the percentage of carbon monoxide that has been converted compared to the amount of carbon monoxide before conversion. If there are a moles of carbon monoxide in the gas before the reaction, and b moles remain after conversion, then the conversion rate is: X = (a – b) / a × 100% (5) In actual production, the conversion gas contains not only carbon monoxide but also components such as hydrogen, carbon dioxide, and nitrogen; its conversion rate can be calculated based on the gas composition before and after the reaction. As can be seen from the conversion reaction equation (1), for every volume of carbon monoxide that is converted, one volume of carbon dioxide and one volume of hydrogen are produced. Therefore, the volume of the converted gas (on a dry basis) equals the volume of the gas before conversion plus the volume of carbon monoxide that has been converted. Assuming that the volume of the raw gas before conversion is 1 on a dry basis, and denoting the volume percentage of carbon monoxide in the gas before and after conversion as Vco and V’co respectively, the volume of the converted gas is (1 + Vco·X). The concentration of carbon monoxide in the converted gas is given by: V’co = (Vco – Vco·X) / (1 + Vco·X) × 100% (6). After simplification, it can be obtained that X = (Vco – V’co) / … × 100% (7). Under certain conditions, the conversion rate at which the conversion reaction reaches equilibrium is known as the equilibrium conversion rate; it represents the maximum conversion rate under those conditions. When using 1 mole of dry raw gas as a reference, the relationship between the equilibrium constant and the equilibrium conversion rate is given by: Kp = (c + ax*) (d + ax*) / (a – ax*) (b – ax*) (8). Here, a, b, c, d represent the molar fractions of carbon monoxide, water vapor, carbon dioxide, and hydrogen in the raw gas before conversion; x* represents the equilibrium conversion rate, in percent. Using equations (4) and (8), it is possible to calculate the equilibrium conversion rate under different temperature and composition conditions. Subsequently, the equilibrium concentration of residual carbon monoxide in the converted gas can be determined using equation (6). The higher the equilibrium conversion rate, the lower the residual amount of carbon monoxide in the converted gas when the reaction reaches equilibrium. Under large-scale industrial production conditions, the reaction cannot reach equilibrium; therefore, the conversion rate actually cannot attain the equilibrium conversion rate. When necessary, the quality of the production process conditions can be assessed by the degree of proximity between the actual conversion rate and the equilibrium conversion rate. III. Factors Affecting the Chemical Equilibrium of the Shift Reaction 1. Effect of temperature: As can be seen from Equation (4) and Table 2, a decrease in temperature increases the equilibrium constant, which facilitates the progression of the shift reaction to the right. As a result, the equilibrium conversion rate increases, and the residual carbon monoxide content in the shifted gas decreases. When the H2:CO ratio in the original gas is 1:1, the relationship between temperature and the equilibrium conversion rate is shown in the figure. In industrial production, reducing the reaction temperature must be considered in conjunction with the reaction rate and catalyst performance. For gasified gas with a high carbon monoxide content, the reaction is generally carried out at a higher temperature at the beginning in order to accelerate the reaction rate; whereas in the later stages of the reaction, the temperature must be lowered to some extent to ensure complete conversion. This is why a two-stage shift process is used in industry. The reaction temperature is closely related to the active temperature of the catalyst; generally, in industrial applications, the shift catalyst cannot carry out the shift reaction properly when the temperature is below its active temperature, and it will be damaged when the temperature exceeds a certain level. Therefore, the conversion reaction of carbon monoxide must select an optimal operating temperature within the catalyst’s active temperature range. 2. Effect of pressure: The carbon monoxide conversion reaction is an equimolar reaction; the number of gas molecules remains the same before and after the reaction, so the total volume of the gas does not change. Under current industrial operating conditions, pressure has no significant effect. 3. Effect of steam addition amount: Increasing the amount of steam used can drive the shift reaction in the direction of carbon dioxide formation. Therefore. In production, an excess of steam is always added to the feed gas to increase the conversion rate. . (CO:40% H2:50% CO2:5%) (1) The lower the conversion temperature, the more favorable it is for the reaction to proceed, and it also helps to reduce steam consumption. (2) At the same temperature, as the amount of steam used increases, the equilibrium conversion rate also increases, but this increase is initially rapid before slowing down. Therefore, to achieve a very high conversion rate, a significant increase in the amount of steam required. This is not only economically unreasonable, but it also makes it difficult to maintain the temperature of the catalyst layer. 4. Effect of carbon dioxide: During the shift reaction, if the carbon dioxide produced can be removed, the reaction will shift to the right, thereby increasing the conversion rate of carbon monoxide. The method for removing carbon dioxide is to convert carbon monoxide to a certain extent and then send it to a decarburization process to remove carbon dioxide from the gas. However, since the process of removing dioxygen from carbon is relatively complex, it is rarely used in industry. 5. Effects of side reactions: In the conversion of carbon monoxide, side reactions such as carbon deposition and methanation may occur. The reaction equations are as follows: 2CO → C + CO2 + Q (9) CO + 3H2 → CH4 + H2O + Q (10) 2CO + 2H2 → CH4 + CO2 + Q (11) CO2 + 4H2 → CH4 + 2H2O + Q (12) These side reactions not only consume the useful components hydrogen and carbon monoxide in the feed gas, increasing the amount of the unwanted component methane, but the free carbon produced in the carbon deposition reactions can easily adhere to the surface of the catalyst, thereby reducing its activity. All of these side reactions are exothermic reactions involving volume reduction; therefore, lowering the temperature and increasing the pressure facilitate the occurrence of these side reactions. However, in actual production, under the existing process conditions, these side reactions generally do not occur easily. IV. Kinetics of Transformation Reactions 1. Reaction mechanism and kinetic equations: The reaction between carbon monoxide and water vapor, when carried out solely in the gas phase, proceeds very slowly even at a temperature of 1000°C, despite the use of large amounts of water vapor. This is because, during the transformation reaction, the hydrogen-oxygen bonds in the steam molecules must first be broken; then the oxygen atoms are rearranged into carbon monoxide molecules to form carbon dioxide, while the two hydrogen atoms combine with each other to form hydrogen molecules. The bond energy of the hydrogen-oxygen bond in water molecules is very high; considerable energy is required to break the H-O-H bonds. As a result, the reaction proceeds very slowly. And in the presence of a catalyst, the reaction proceeds as follows: +H2O(g)→O+H2 (13) O+CO→+CO2 (14) Where: --- represents the catalyst ； O——represents an intermediate compound, where O—— refers to adsorbed oxygen; that is, the vapor molecules are first adsorbed by the active surface of the catalyst and decomposed into H2 and adsorbed oxygen atoms. The hydrogen enters the gas phase, while the adsorbed oxygen forms an adsorption layer on the catalyst surface. When carbon monoxide comes into contact with the oxygen atom adsorption layer, it is oxidized to carbon dioxide, which then leaves the catalyst surface and enters the gas phase. Then the catalyst adsorbs water molecules again, and the reaction continues. In this way, less energy is required, and the speed **increases**. In process calculations, the commonly used kinetic equations are: (1) Second-order reaction: rco = K(Ya·Yb – (Yc·Yd/Kp)). In equation (15), rco represents the reaction rate, in Nm3CO/m3 of catalyst per hour ； K — reaction rate constant, h-1 ； Kp——equilibrium constant ； Ya, Yb, Yc, Yd —— are the instantaneous amounts and molar fractions of CO, H2O, CO2, and H2, respectively. For the highly variable catalysts (foreign G—3A type), K=EXP(15.99-4900/T); for the domestic B104 type (i.e., C4—2), K=EXP(17.94-6300/T). (2). Power-law kinetic equations: Most kinetic equations fall into this category; they can fully describe the rate of the conversion reaction: rco = k•Pco / (Pcol • PH2O^m • Pco2^n • PH2Q • (1–β)) (16) Where: rco is the reaction rate; K is the rate constant; Pco, PH2O, Pco2, PH2Q represent the partial pressures of each component respectively, in units of atm, L, M; m, n, p are the power exponents; B = (Pco2•PH2O) / (Kp•Pco•PH2O); Kp is the equilibrium constant. Different types of highly active catalysts have different values for these power exponents. The general range is: m = 0.8–1.0, n = 0–0.3, q = 0. 2. Influence of diffusion processes: For conversion reactions, the effect of internal diffusion cannot be ignored. The internal surface utilization rate is related not only to the size, structure, and reactivity of the catalyst, but also to factors such as operating temperature and pressure. For catalysts of different sizes, the utilization rate of the catalyst’s internal surface was calculated comprehensively based on the effective diffusion coefficient of CO at the operating temperature and pressure, as well as the calculated reaction rate. As can be seen from Figure 3, for catalysts of the same size, an increase in temperature at constant pressure leads to an increased diffusion rate of CO; however, the rate constant for reactions on the catalyst’s internal surface increases even more rapidly, resulting in a decrease in the utilization rate of the internal surface. At the same temperature and pressure, catalysts with smaller particles have a higher internal surface utilization rate; this is because the smaller the size of the catalyst, the shorter the length of its capillary pores, which reduces internal diffusion resistance and thus increases the internal surface utilization rate. For catalysts of the same size, at the same temperature, the higher the pressure, the greater the reaction rate; the effective diffusion coefficient of CO decreases significantly, as a result of which the utilization rate of the inner surface drops rapidly with increasing pressure. Section 2 Catalysts for Carbon Monoxide Transformation Reactions: Intermediate-temperature catalysts are classified into two major categories based on their composition: iron-chromium series and cobalt-molybdenum series. Iron-based catalysts have high catalytic activity and good mechanical strength; they can tolerate small amounts of sulfides, possess excellent heat resistance, a long service life, and are relatively low in cost ； The outstanding feature of cobalt-molybdenum catalysts is their good resistance to sulfur; they are suitable for gas containing high levels of sulfides, but they are expensive. 1. Composition and main properties of ferro-chromium catalysts: The main components of ferro-chromium catalysts are iron oxide and the promoter chromium oxide. It generally contains 70–90% iron oxide and 7–14% chromium oxide. In addition, there are small amounts of magnesium oxide, potassium oxide, calcium oxide, and other substances. Reducing iron oxide to ferric oxide can accelerate the conversion reaction ； Chromium trioxide can inhibit the recrystallization of iron tetraoxide, thereby forming a microporous structure in the catalyst, enhancing its heat resistance and mechanical strength and prolonging its service life ； Magnesium oxide can improve the heat and sulfur resistance of catalysts ； Both potassium oxide and calcium oxide can increase the activity of the catalyst. Ferro-chromium catalysts are brown cylindrical or flaky solid particles, with an active temperature range of 350–550°C; they tend to absorb moisture in air, which reduces their activity. The reduced ferro-chromium catalyst burns rapidly when exposed to air, immediately losing its activity. Compounds of sulfur, chlorine, phosphorus, and arsenic, as well as oily substances, can cause poisoning. 2. Cobalt-molybdenum catalysts (1) are resistant to high hydrogen sulfide levels and possess good strength. Therefore, it is particularly suitable for the partial oxidation of heavy oil and coal-based processes. The removal of hydrogen sulfide from the feed gas and carbon dioxide from the shift gas can be considered together to save steam and simplify the process. (2) It has high activity, and its onset activity temperature is much lower than that of ferro-chromium catalysts. To achieve the same conversion rate, the volume of the molybdenum-cobalt catalyst required is only half that of the commonly used iron-based catalysts. (3) During use, if carbon compounds accumulate on the catalyst, it can be burned and regenerated using a mixture of air and steam or oxygen; after being re-sulfurized, it can be used again. (In actual use, this is generally not done.) This sulfur-resistant, highly active, and regenerable cobalt-molybdenum-based shift catalyst is widely used in heavy oil and gasification plants, despite its high cost. The shift catalyst used in our plant is the QCS-03 cobalt-molybdenum sulfur-resistant shift catalyst developed by Qilu Institute. 3. Composition and properties of cobalt-molybdenum catalysts. The compositions of sulfur-resistant shift catalysts reported to date include various formulations, generally containing cobalt oxide and molybdenum oxide. As for carriers, Al2O3 and MgO are the best choices; the advantage of MgO as a carrier is that fluctuations in H2S concentration have less impact on the catalyst’s activity. Some catalysts also contain alkali metal oxides to lower the temperature of the conversion reaction. 4. Sulfidation of cobalt-molybdenum catalysts The actual active components in cobalt-molybdenum catalysts are CoS and MoS2; therefore, they must be sulfidized to acquire conversion activity. The purpose of sulfidation is also to prevent cobalt-molybdenum oxides from being reduced to their metallic state; metallic cobalt and molybdenum can then promote the methanation of CO and H2. This highly exothermic reaction can cause a significant temperature rise, which may damage the catalyst. It can be sulfided using a gas containing H2S, or it can be sulfided with CS2 in the presence of hydrogen. The temperature for sulfidation using hydrogen sulfide can be lower; it can start at 150–250°C. The reaction equations are as follows: CoO + H2S ⇌ CoS + H2O + 3.2 KCal; MoO3 + 2H2S + H2 ⇌ MOS2 + 3H2O + 11.5 KCal. These are reversible exothermic reactions. Therefore, the H2S concentration in the introduced gas should not be too high. The sign that sulfidation is complete is an increase in the concentration of sulfides in the outlet stream; generally, the total amount of sulfides required for sulfidation must exceed 50–100% of the amount calculated based on the chemical equation. The sulfidation reaction is a reversible reaction. Therefore, fluctuations in the sulfur content of the feed gas can lead to sulfur loss from the catalyst, thereby reducing its activity. Cobalt-molybdenum catalysts have hydrogenation properties; therefore, when the content of unsaturated hydrocarbons in the feed gas is high, severe exothermic reactions can occur, which requires special attention. 5. Oxidation and regeneration of cobalt-molybdenum catalysts: After being used for a period of time, cobalt-molybdenum catalysts develop carbon deposition due to the polymerization of heavy hydrocarbons. This not only reduces the catalyst activity but also increases the resistance in the catalyst bed; in such cases, the catalyst should be carbonized for regeneration ； Carbon is usually burned using steam containing 0.4% O2 (i.e., 2% air), with the temperature to be controlled between 350 and 450°C; exceeding 500°C will damage the catalyst. Pressure has little effect on carbonization, but for uniform gas distribution, a gas pressure of 1 to 3 atmospheres is appropriate. During carbon burning, the direction of the gas flow is opposite to that in the normal conversion process; the gas enters from the bottom of the reactor and exits from the top, which helps to reduce damage to the catalyst caused by high temperatures and to blow away dust. During carbonization, the sulfur in the catalyst is also burned off, causing the catalyst to reach an oxidized state. During the carbon burning process, the bed temperature should be closely monitored, and the concentration of air or oxygen should be adjusted to control it. When there is no significant temperature rise in the bed layer, the combustion front has already passed through the reactor. A decrease in the outlet temperature and an increase in O2 in the gas indicate that carbon burning has ended. Slightly increase the oxygen concentration to further burn carbon. If there is no significant increase in temperature, the oxygen concentration can be increased continuously, and finally cooled to below 50°C with air. The catalyst after carbonization must be re-sulfurized before it can be used. To remove the catalyst, since used catalysts are self-igniting at temperatures above 70°C, it must first be cooled to ambient temperature inside the reactor. When shutting down, prepare a faucet to spray water to cool down and extinguish the fire. Apart from one discharge hole, no additional holes should be created, to prevent a sharp rise in the temperature of the catalyst bed due to the \"chimney effect\". Section 3: Selection of Process Conditions for Carbon Monoxide Conversion. To ensure that the conversion process takes place under optimal conditions, achieving high yields, good quality, and low consumption, it is necessary to analyze the impact of various process conditions on the reaction and select the best conditions accordingly. I. Pressure transformation: As mentioned earlier, pressure has almost no effect on the equilibrium of conversion reactions. However, pressurized conversion offers the following advantages: 1. It can accelerate the reaction rate and increase the catalyst’s productivity, thereby allowing for a higher space velocity to boost production capacity. 2. The equipment has a small size, is compactly arranged, and requires less investment. 3. The high condensation temperature of water vapor in the wet shift gas facilitates the recovery and utilization of thermal energy. However, increasing the pressure raises the acidity of the system condensate and accelerates equipment corrosion. If all the steam required for the conversion process is supplied as fresh steam from outside, pressurized conversion will increase the load of high-pressure steam, thereby reducing its capacity to do work. II. Transformation temperature: The transformation reaction is an exothermic reversible reaction. Raising the temperature has opposing effects on both the reaction rate and the chemical equilibrium. When the composition of the reactants and the catalyst remain constant, the temperature at which the maximum reaction rate is achieved is the optimal temperature. The reaction has different compositions at various moments. Corresponding to different conversion rates, the curve formed by connecting the points representing the optimal temperatures for those different conversion rates is called the optimal temperature curve. As shown in Figure 4, line CD represents the optimal temperature curve, while line AB represents the equilibrium curve. Although it is ideal to follow the optimal temperature curve, it is actually impossible to operate strictly according to it, as it is difficult to remove the heat of reaction accurately and continuously as required by the optimal temperature; moreover, at the start of the reaction (X=0), the optimal temperature **exceeds the heat tolerance of conventional high-activity catalysts. The principle for selecting the operating temperature in actual production is as follows: 1 The operating temperature must be kept within the active temperature range of the catalyst. The starting temperature of the reaction should be about 20°C higher than the catalyst’s active temperature, and overheating must be strictly avoided during the reaction. 2 Ensure that the entire transformation process takes place under conditions as close as possible to the optimal temperature. Since the optimal temperature decreases as the conversion rate increases, it is necessary to remove the heat of reaction in a timely manner as the reaction proceeds in order to lower the reaction temperature. Industrially, a multi-stage bed indirect cooling method is employed, using feed gas and saturated steam for heat exchange between stages to remove the heat of reaction. The greater the number of stages, the more the transformation process approaches the optimal temperature curve, but the process also becomes more complex. III. Steam ratio: The steam ratio generally refers to the molar ratio of steam to the feed gas (or carbon monoxide in it). Increasing the steam usage can raise the CO conversion rate, accelerate the reaction rate, and prevent side reactions; however, excessive steam is not only economically unreasonable, but it also increases the resistance in the catalyst bed, prolongs the residence time of carbon monoxide, and raises the load on waste heat recovery. Therefore, the steam ratio must be controlled appropriately based on factors such as the composition of the feed gas, conversion rate, reaction temperature, and catalyst activity. The typical steam ratio for the transformation is: H2O/CO = 3–5. Section 4: Process Flow for Carbon Monoxide Conversion – The water gas supplied from gasification (242.7℃ ； 6.15Mpa (A) ； With a water vapor ratio of 1.50), it passes through the water-gas separator and the water-gas waste heat boiler, where the temperature drops to 230°C, and then through Condenser No. 1. After the condensate is separated in Condenser No. 1, the water gas is divided into two streams: one stream is used for gas distribution and does not pass through the shift reactor, while the other stream is fed into a medium-temperature heat exchanger to be preheated to 260°C before entering the shift reactor. The furnace is equipped with a sulfur-resistant shift catalyst. The CO content in the reaction gas leaving the converter is approximately 14% (on a dry basis), and the temperature is 394°C; after being cooled by the medium-temperature heat exchanger, the temperature drops to 364°C. This gas mixes with the water gas supplied for gas distribution to form shift gas with a CO content of 19% (on a dry basis) and a temperature of 338°C. The transformed gas is heated by the boiler feedwater heater, whose temperature is reduced to 191°C, and then separated in the No. 2 condensate separator. The separated shift gas enters the desalinated water heater, where its temperature is reduced to 70°C; thereafter, it goes into the shift gas water cooler, where its temperature is further lowered to 40°C. Through Condensate Separator No. 3. The shifted gas, after separation of the condensate, is sent to the low-temperature methanol washing unit. The boiler feed water at 140°C from the pipeline network is heated to 235°C by a feed water heater before being sent outside the plant. The condensate separated by Condenser No. 1 enters the condensate of Condenser No. 2, V2503; the condensate from V2503 is then pumped by a high-temperature condensate pump to the gas treatment scrubber tower. The demineralized water from the demineralization station is heated to 116.5°C by a demineralized water heater and then sent to the deaerator in the boiler feedwater system. The condensate from Condenser No. 3 is sent to the old unit’s condensate stripping tower. Catalytic heating sulfidation is carried out at 0.65 Mpa(A). Low-pressure nitrogen is introduced into the shift reactor, heated to 320°C by a nitrogen heater before entering the shift furnace, and the waste nitrogen from the shift reactor is sent to a flare. Section 5: Characteristics of the Main Control Circuits and Devices I. Main Control Circuits 1. Regulation of the water-gas flow rate to the conversion device: The water-gas flow rate control valve is closed during shutdown, while it is used to regulate the system flow rate during normal operation. 2. Water-gas waste boiler level control: Adjusted based on the water inflow to the waste boiler, the amount of steam generated, and its own liquid level. 3. Steam pressure regulation: Adjust the temperature of the water gas after it is cooled by the waste heat boiler, based on the pressure of the by-product steam. 4. Regulation of the converter inlet temperature: This is achieved by adjusting the gas flowing into the converter to pass through a bypass around the medium-temperature heat exchanger. 5. Adjustment of CO ratio: This device operates in a partial conversion mode; to meet the requirements for CO concentration in methanol synthesis, the converted water gas is mixed with unconverted gas to achieve a CO concentration of around 19%. II. Equipment Features 1. Ammonia synthesis requires the complete conversion of CO into hydrogen, whereas methanol synthesis plants need a reformer to supply 19% (VOL) of CO; accordingly, the large amount of moisture present in the water gas must be condensed in the new reformer. 2. A water-gas separator has been specifically installed to remove the condensate water that forms during the long-distance transportation of gas from production to conversion. 3. The converter is heated using 4.0 Mpa superheated steam, while the heating medium is low-pressure nitrogen at 0.5 Mpa. Section 6 Introduction to Main Equipment 1. Converter The converter is an important piece of equipment in the conversion section. Inside the shift converter, the gasified water gas undergoes a shift reaction under the action of a catalyst to produce the raw gas required for synthesizing methanol. This shift converter is an axial fixed-bed reactor with an operating pressure of 6.21 MPa and an operating temperature of 260–410°C. Its design pressure is 6.72 MPa and its design temperature is 430°C. The diameter is φ3000 mm, and the media used are water gas and shift gas. The shell material is 15CrMoR+0Cr18Ni10Ti. To ensure uniform entry of process gas into the catalyst bed, a gas distributor is installed at the gas inlet of the shift converter, and a layer of metal wire mesh and alumina refractory balls is packed on top of the catalyst bed. Directly beneath the catalyst layer are two layers of lower metal mesh and alumina refractory balls. An outlet gas collector is installed at the process gas outlet at the bottom of the converter. Thermocouple sleeves are installed in the converter, and thermocouples are placed there to monitor the temperature of the bed layer. The design parameters of the converter are as follows: Specification: φ3000; Height of the coal contact layer; Operating temperature: 393–410°C; Operating pressure: 6.20–6.31 MPa(A). Material name: Water gas → Converter gas. Insulation thickness of the equipment: 190 mm. Sulfur-resistant catalyst (QCS-03, one layer): H = 3680 mm3; Bulk density: 0.75–0.82 t/m3. Open-ended refractory ceramic balls, KK-φ25/φ50: Bulk density: 1.8 t/m3; Al2O3 content: 20–25%. Materials used: 15CrMoR + 0Crl8Ni10Ti/15CrMoⅢ forged material/0Crl8Ni10Ti. Filling amount: 36,800 kg. II. Waste heat boiler for water gas: The conversion reaction is an exothermic reaction. The water-gas waste heat boiler is designed to recover the waste heat from the high-temperature process gases in the reformer unit, in order to produce superheated steam at 1.0 MPaG. The structure of this device is a U-tube heat exchanger. The steam outlet is equipped with a demister to remove liquid droplets from the generated steam. Manholes are provided on both end caps for installation and maintenance purposes. The main parameters of the water-gas waste heat boiler are as follows: Container type: Number of heat exchange stages: Material: Operating pressure: Design pressure (MPa): Operating temperature: Design temperature (°C): Diameter of heat exchange tubes: Number of heat exchange tubes: Heat exchange area (m2): Inner diameter of the shell: Total length: Shell material: Material of heat exchange tubes: Material of tube sheets: Insulation thickness of the equipment: Category 3. Tube designation: 2. Shell side: 1. Shell side fluid: Boiler feedwater/steam. Tube side fluid: Water-gas. Pressure on tube side: 6.24/6.23 MPa. Pressure on shell side: 3.2/1.4 MPa. Tube side temperature: 6.9 °C. Shell side temperature: 3.6 °C. Tube side temperature range: 240/180 °C. Shell side temperature range: 243 °C/230 °C. Tube side pressure: 250 MPa. Shell side pressure: 245 MPa. Diameter of tubes: φ25×2; Number of tubes: n=730. Outer diameter of tubes: φ1400/φ2000 mm. Total length: 7570 mm. Shell material: 16MnR, 00Crl9Ni10. Tube material: 20MnMoⅢ forged + 00Crl9Ni10. Length of tubes: 120 mm. Last edited by LanDian on 2008-4-10 00:33