Molecular sieve filter for synthesis ammonia process

Abstract

The molecular sieve filter element comprises a filter cylinder, a top cover tube plate and a filter element body, and the filter element body is fixed to the top cover tube plate through conical threads and arranged in the filter cylinder; the number of the filter elements is 30, the diameter of all the filter elements is 60 mm, the height of 12 filter elements close to the air inlet is 500 mm, and the height of the other 18 filter elements is 1000 mm; the filter element comprises an inner cylinder with the diameter of 15mm, 30 filter screen sheets are uniformly fixed around the periphery of the inner cylinder, and the length of each filter screen sheet is 22.5 mm; and a baffle plate in the vertical direction is arranged on one side, provided with the air inlet, in the filter cartridge. The filter is large in filtering area and high in filtering precision, the thickening speed of a filter cake layer of the filter element is reduced, the pressure difference rising speed is relieved, the material consumption of cleaning workers is reduced, pollutant emission is reduced, and the operation hidden danger of a production device is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of synthetic ammonia production, and in particular relates to a molecular sieve filter used in a synthetic ammonia process. Background Art

[0002] In the process of synthetic ammonia production, molecular sieves are needed to remove CO2, CO, H2O and other components in the process gas. Molecular sieves will produce certain solid impurities during operation, and a filtering device needs to be set at its outlet to remove solid powder impurities in the gas. However, the powder generated during the operation of the molecular sieve causes the filter pressure difference to rise quickly, the compressor power consumption increases, and the filter is frequently cleaned online. The existing filter uses the BP-24-20-4-PK (Boll) filter element produced by the German BOLL company. The filter is cleaned 9.3 times per year on average, and each cleaning takes 12 hours, including cutting out equipment, pressure relief, replacement, adding blind plates, removing heads, hoisting, cleaning, resetting, etc. The entire operation process is carried out under high pressure and high hydrogen environment, with a hydrogen concentration of 74% and very dry. The reduced metal powder entrained in the exhaust gas will spontaneously ignite after contacting the air to form sparks, and the operation risk is very high. In addition, the production space on the synthetic ammonia process production line is limited, and it is impossible to increase the filter area by increasing the number or volume of filters to slow down the pressure difference increase. Utility Model Content

[0003] The utility model provides a molecular sieve filter for a synthetic ammonia process, aiming at slowing down the filter pressure difference rising speed without changing the filter volume and the number.

[0004] A molecular sieve filter for a synthetic ammonia process, characterized in that it comprises a filter cartridge, a top cover tube sheet and a filter element, the filter cartridge is a U-shaped barrel, an air inlet connected to the molecular sieve is arranged in the middle of the barrel body, a slag outlet is arranged at the bottom, and the length of the filter cartridge is not less than 1480 mm; the filter element is fixed to the top cover tube sheet through a tapered thread and is arranged inside the filter cartridge; the number of filter elements is 30, the ends of all filter elements are connected in series with each other through soft steel ropes and connected to the inner wall of the filter cartridge, the diameter of all filter elements is 60 mm, the height of 12 of which close to the air inlet is 500 mm, and the height of the remaining 18 is 1000 mm; the filter element comprises an inner barrel with a diameter of 15 mm, 30 filter mesh sheets are evenly fixed around the outer circumference of the inner barrel, and the length of each filter mesh sheet is 22.5 mm; a baffle in a vertical direction is arranged on one side of the filter cartridge where the air inlet is arranged.

[0005] Furthermore, the filter sheet is a multi-layer filter structure, the surface filter is a metal wire mesh, and the inner lining is a non-metal wire mesh.

[0006] The beneficial effects of the utility model are: large filtration area and high filtration accuracy. Without changing the overall volume of the equipment, the total filtration area of ​​the filter element is increased by 3 times on the basis of the existing technology, and the initial pressure difference is 0.025MPa higher than that of the original filter element, with higher filtration accuracy and more effective protection of the downstream compressor impeller and sealing system. By setting a baffle, inertial separation and filtration separation are combined for use. Before the gas enters the filter element, a preliminary gas-solid separation is performed, which slows down the thickening speed of the filter cake layer of the filter element and alleviates the rate of increase in pressure difference. The end-to-end serial positioning of the filter element is increased, and the single-point fixation of the tapered thread of the original filter element port is changed to a double-point fixation at the head and tail ends, which fundamentally solves the problem of the filter element falling off during use. It saves labor and material consumption for cleaning, reduces pollutant emissions, eliminates operating hazards of production equipment and improves economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A schematic diagram of the structure of a molecular sieve filter used in the synthetic ammonia process

[0008] Figure 2 Schematic diagram of the filter element structure.

[0009] Among them: 1-filter cartridge, 2-top cover tube plate, 3-filter element, 31-inner cylinder, 32-filter mesh, 4-baffle, 5-soft steel rope DETAILED DESCRIPTION

[0010] Embodiment 1: A molecular sieve filter element for a synthetic ammonia process, comprising a filter cartridge 1, a top cover tube sheet 2 and a filter element 3, the filter cartridge 1 being a U-shaped barrel, an air inlet connected to the molecular sieve being arranged in the middle of the barrel body, a slag outlet being arranged at the bottom, and the length of the filter cartridge 1 being not less than 1480 mm; the filter element 3 being fixed to the top cover tube sheet 2 by a tapered thread and arranged inside the filter cartridge 1; the number of the filter elements 3 being 30, the ends of all the filter elements 3 being connected in series to each other by a soft steel rope 5 and connected to the inner wall of the filter cartridge 1, the diameter of all the filter elements 3 being 60 mm, the height of 12 of the filter elements 3 near the air inlet being 500 mm, and the height of the remaining 18 of the filter elements 3 being 1000 mm; the filter element 3 comprising an inner barrel 31 having a diameter of 15 mm, 30 filter mesh sheets 32 being evenly fixed on the outer periphery of the inner barrel 31, and the length of each filter mesh sheet 32 ​​being 22.5 mm; the filter mesh sheet 32 ​​being a multi-layer filter mesh structure, the filter mesh on the surface being a metal wire mesh, and the inner lining being a non-metal wire mesh. The filter has a filtration area of ​​19.68 square meters, which is three times the filtration area of ​​existing filters.

[0011] A vertical baffle 4 is provided on one side of the filter cartridge 1 where the air inlet is provided. According to the principle of inertial separation: an obstacle is provided on the path of gas flow, and when the airflow bypasses the obstacle, a sudden turn occurs, and particles or droplets hit the obstacle and are collected. Therefore, the baffle 4 utilizes the sedimentation effect when the airflow bypasses the obstacle to achieve inertial separation, and the particles entrained in the airflow are initially separated, while also providing a certain buffering protection for the filter element 3. After the baffle 4 was installed, it was found that there was more dust at the bottom of the equipment tank during the cleaning process of the filter, while the amount of dust attached to the filter element was significantly less than before, indicating that inertial separation was effective.

[0012] The initial pressure difference of the filter is 0.025MPa higher than that of the existing filter when the filtration area is increased by 3 times, and the filtration accuracy is higher, which more effectively protects the downstream compressor impeller and sealing system; the number of online cleaning times of the filter has been greatly reduced. Under the same working conditions, the pressure difference of the molecular sieve increased by 4-5KPa per operation and regeneration cycle before the project was implemented, and the pressure difference of the molecular sieve increased by only 0.4KPa per operation and regeneration cycle after the project was implemented. The online cleaning cycle was extended, and the annual cleaning times were reduced from 9.3 times to no more than 2 times, saving cleaning manpower and material consumption, reducing pollutant emissions, and eliminating the hidden dangers of the production unit. The pressure difference of the filter rises slowly, and the annual economic benefit is more than 1.8 million yuan calculated by saving the high-pressure steam consumption of the synthesis gas compressor; at the same time, the filter element has achieved domestic substitution, and the purchase cost of a single element has been reduced from 8,000 yuan / element to 4,000 yuan / element. A total of 60 molecular sieve filters are used, and the one-time purchase cost is saved by 240,000 yuan, which is a considerable economic benefit.

Claims

1. A molecular sieve filter for ammonia synthesis process, characterized in that It includes a filter cartridge, a top cover tube plate and a filter element. The filter cartridge is a U-shaped barrel. An air inlet connected to the molecular sieve is arranged in the middle of the barrel body, and a residue outlet is arranged at the bottom. The length of the filter cartridge is not less than 1480mm. The filter element is fixed to the top cover tube plate through a tapered thread and is arranged inside the filter cartridge. There are 30 filter elements, and the ends of all filter elements are connected to each other in series through soft steel ropes and connected to the inner wall of the filter cartridge. The diameter of all filter elements is 60mm, of which 12 elements close to the air inlet are 500mm high, and the remaining 18 elements are 1000mm high. The filter element includes an inner barrel with a diameter of 15mm, and 30 filter mesh pieces are evenly fixed in an annular direction on the outer circumference of the inner barrel, and the length of each filter mesh piece is 22.5mm; a vertical baffle is arranged on the side of the filter cartridge where the air inlet is arranged.

2. A molecular sieve filter for ammonia synthesis process according to claim 1, characterized in that The filter sheet is a multi-layer filter structure, the surface filter is a metal wire mesh, and the inner lining is a non-metal wire mesh.

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