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This post was last edited by sailan on 2010-12-10 15:12. I. Introduction: After steam reforming, natural gas undergoes further transformation, which increases the H2 concentration in the feed to the PSA unit. This helps to improve the H2 yield, reduces the investment required for PSA systems, and increases the calorific value of the PSA off-gases, allowing them to be reused as fuel gas in the first-stage furnace. II. Brief description of the process flow: The natural gas coming from the boundary area is compressed to a pressure of about 2.5 Mpa, and then enters the first-stage furnace feed gas preheater where it is heated to around 380°C. The sulfur content in the feed gas is reduced to 0.1 ppm through an iron-manganese desulfurization unit and a zinc oxide desulfurization unit. The purified feed gas is mixed with process steam at a water-to-carbon ratio of 3.5; the resulting mixture is heated to 500°C in the convective coil of the first-stage furnace, after which it enters the tubes of this stage where it undergoes steam conversion reactions under the action of a catalyst. The heat required for these reactions is provided by burning fuel gas in the burners located at the top. The converted gas exits the first-stage furnace at a temperature of around 850°C and a pressure of 1.98 Mpa, with a residual methane content of approximately 4.3%. A stream of converter gas generates medium-pressure steam at approximately 2.6 Mpa in a converter gas waste heat boiler; after heat is recovered in a boiler feedwater preheater, it enters the conversion process. The temperature of the converted gas entering the transformation process is approximately 340°C. Upon entering the medium-shift reactor, the CO in the converted gas reacts with water vapor under the action of the medium-shift catalyst to produce H2 and CO2, releasing a large amount of reaction heat that raises the temperature of the gas. The medium-shift gas produced in the medium-shift reactor enters the medium-shift waste boiler, where it is cooled to 210°C before entering the low-shift reactor. Under the action of the catalyst in the low-shift reactor, the CO content in the medium-shift gas is reduced to 0.5%. The temperature of the low-shift gas exiting the reactor is 233°C; after condensation and separation, this gas proceeds to the pressure swing adsorption process. The process condensate coming out of the separator is pressurized by a pump and then fed into the stripping tower, where it is stripped using medium-pressure steam. The steam exiting the tower is used as process steam for conversion, while the liquid at the bottom of the tower is sent to the chemical water treatment station after heat recovery and cooling. The pressure swing adsorption process (PSA) consists of 6 adsorption towers, 1 forward gas discharge buffer tank, 1 desorbed gas buffer tank, 1 product hydrogen buffer tank, and 1 desorbed gas compressor. The low-temperature shift gas, with a pressure of approximately 1.61 Mpa and a temperature of 40°C, first enters the PSA unit, flowing from the bottom of the tower into the adsorption tower that is in the adsorption state (one adsorption tower is always in this state). Under the sequential adsorption by various adsorbents, impurities such as H2O, CO, CO2, CH4, and N2 are adsorbed, while the hydrogen that is not adsorbed flows out from the top of the tower. After the pressure is adjusted to a stable level, it is sent to subsequent processing stages. III. Process principles: 1. Conversion principle: CH4 + H2O(vapour) = CO + 3H2 (endothermic). 2. Shift principle: CO + H2O(vapour) = CO2 + H2 (exothermic). 3. Pressure swing adsorption: Low-pressure gas undergoes sequential adsorption by various adsorbents, during which impurities such as H2O, CO, CO2, CH4, and N2 are adsorbed, while H2 is released as a product from the adsorption tower. IV. Brief Operation Instructions 1. Normal maintenance of the position 1.1 Normal maintenance at the site: 1.1.1 Conduct regular inspections, make careful comparisons, and meticulously analyze the data related to the process conditions in order to gain insights and determine whether the operating equipment is functioning properly. 1.1.2 Check whether the oil temperature and pressure, speed of the exhaust fan, oil level in the oil tank, cooling water, and related instruments are all normal. Check whether the inlet and outlet pressures, outlet flow rate, current, oil circuit system, and bearing temperature of various other pumps are normal. 1.1.3 Whether the operation of the single-stage furnace is satisfactory, including the combustion conditions and the proper functioning of the conversion tubes. 1.1.4 Maintenance of the boiler system, including sludge removal; according to analysis, chemical dosing is used to adjust the process parameters within the specified range. 1.1.5 Check whether the water levels in each jacket are normal. 1.1.6 Maintain the normal operation of the desulfurization system and the conversion system. 1.1.7 Check whether there are any leaks in the flanges and pipelines of various equipment, and whether all instruments and control valves are operating properly. 1.1.8 Conduct on-site inspections on time, fill in reports and records; if any abnormalities are detected, they must be reported to superiors immediately, appropriate actions taken, and a proper handover of duties must be carried out. 1.1.9 Regular maintenance of the PSA process to ensure the proper operation of the adsorption and regeneration processes. 1.2 Normal maintenance of the control station: 1.2.1 The equipment at the station must be kept clean, dry, and at an appropriate operating temperature, to prevent failures caused by water, oil, dust, etc., as well as to avoid damage to the equipment by small animals, thereby ensuring the safety and reliability of the equipment. 1.2.2 Maintain the stability of steam systems at all levels, including stability in flow rate, temperature, and pressure, and supply stable steam to external users. 1.2.3 Maintain and regulate the stable operation of various units, adjusting parameters such as unit speed, outlet flow rate, and outlet pressure in response to changes in environmental conditions (temperature, circulating water temperature, inlet pressure, etc.). 1.2.4 Maintain the stable operation of all catalyst-related equipment, prevent significant fluctuations and the hazards they may cause, and strictly keep the relevant process parameters of these devices within acceptable and safe ranges. 1.2.5 Control and regulate the stability of the liquid level, operating pressure, temperature, or flow rate in various towers and separation tanks, to prevent hazards caused by air ingress or excessive liquid levels. 1.2.6 Maintaining the normal and stable operation of various large and small pumps, focusing on parameters such as flow rate, inlet and outlet pressures, and current. 1.2.7 Perform regular maintenance on relevant electrical appliances, instruments, and control valves to ensure they operate within their sensitivity range. 1.2.8 Adjust various process parameters in a timely and appropriate manner to ensure the normal and safe operation of the equipment. 2. Brief description of plant startup: 2.1 Startup of utility systems: 2.1.1 Commissioning of the circulating water system 2.1.2 Commissioning of the instrument air system 2.1.3 Commissioning of the N2 system 2.1.4 Commissioning of the boiler feedwater system 2.1.5 Establishment of the system’s steam piping network 2.2 Startup of the process systems: 2.2.1 Replacing N2 with O2 in the desulfurization, conversion, and medium-pressure transformation systems