How to purify high-temperature gas at 500°C-650°C?

I heard that there are filters capable of withstanding temperatures up to 650 degrees, with filter elements made of iron-based alloys. But I’m not sure if it can filter coal dust.

For this, we can use our company’s ultra-high temperature bag filter; the FLEX-KLEEN brand from the United States is capable of handling high-temperature flue gases, up to 800°C. For detailed inquiries, contact 290855706@qq.com

A granular layer dust collector is used, with high-purity quartz sand as the filter media

The question is whether the presence of coal tar could affect filtration of dust; this is something that deserves consideration

The impact of coal tar on the system is reduced due to the drop in temperature; once the system’s temperature issue is resolved, everything else is fine

Bag dust collection is used; if tar adheres to the filter bags, the problem becomes difficult to resolve

Using ceramic filtration for dust removal in the Shell gasification process should yield good results.

For some owner-led projects, the providers and designers of the process technology packages for various units such as the gasification unit, conversion unit, purification unit, and synthesis unit are different; therefore, it is very important to select a competent design institute. I feel that some of the overall design institutes (and even the project owners) lack the comprehensive coordination capabilities needed to manage the overall project as well as the technical design teams for various components. For example, their overall strength and capabilities, along with their experience in project design and operation, are not on par with those of the technical design institutes handling individual components. Considering the responsibilities associated with the risks in the operation of its own unit design, the Unit Technology Design Institute often sets relatively strict requirements for the input conditions of its own unit (that is, the output results of the previous unit). I have also reviewed the technical specification documents for the gasification units and conversion units of certain projects. It is specified that for the gas supplied to this conversion unit (i.e., the gas output from the gasification unit’s purification process), the dust content on a dry basis must be less than 3 mg/Nm^3, and the amount of liquid droplets carried in the gas must not exceed 1 mg/Nm^3. The reason is to prevent dust carried in the purified gas produced by the gasification unit from accumulating at the inlet section of the pre-conversion reactor, thereby hindering the proper operation of that unit. Looking back on those years with the projects for producing synthetic ammonia and methanol from coal (300,000 tons per year, 500,000 tons per year, 800,000 tons per year, 1.2 million tons per year), it seems that such strict requirements were never imposed. Moreover, in terms of both cost and operating expenses, the conversion unit cannot be compared to the gasification unit; why then force the gasification unit to meet such stringent requirements, which ultimately leads to increased operating costs for the entire project? Moreover, isn’t there in the gas inlet section of the pre-conversion reactor a series of ceramic balls of different sizes and heights to serve as inert sections? Isn’t the catalytic reaction section also equipped with various combinations of active sections? Couldn’t the pre-conversion reactor and the main conversion reactor be designed using a hybrid process? From the perspective of the overall economic efficiency of the owner’s future projects, I believe that it is possible to mitigate the stringent requirements on gas supply from the upstream gasification units through competitive optimization and innovative design of unit process combinations. Even if that’s not the case, I’m not the owner; I’m either the supplier of the unit process package or the design institute. Therefore, the suppliers of the gasification unit process package and the design institute must earnestly comply with strict gas supply requirements. Therefore, whether it is a quenching process, a non-quenching process, or liquid slag discharge, it is necessary to meet the requirement of \"extremely low levels of dry-based gas dust and liquid droplets\". The scrubber tower, high-temperature filter elements, and electrostatic precipitators (for dust and tar removal) serve as the final stages in various slag-gasification processes. But obviously, it is not feasible to rely solely on each of these final treatment stages to achieve a situation where \"one person can hold off thousands of attackers.\" After all, the washing tower, ceramic filters, and electrostatic precipitators serve the purpose of handling detailed tasks; they are economic solutions for achieving precise dust removal from air streams containing trace amounts of dust. If these devices were expected to handle all tasks, both simple and complex, then the operation of such a system would be far too expensive. So how is that ‘rough work’ done? The principle is: if a problem can be solved using a two-phase approach, do not resort to a three-phase solution; if it can be resolved directly, avoid using any additional methods. This is because high-temperature wet dust removal not only requires a large amount of desalinated water, but also needs it for heat recovery, in addition to presenting difficulties in post-treatment. For dry processing to carry out the ‘rough work’ of removing the vast majority of dust and liquid droplets, barrier-type devices cannot be used (as their flow surfaces tend to get clogged); instead, dynamic cyclone methods must be employed to separate large amounts of dust and liquid droplets from the hot gas stream. Among the equipment for cyclone-based gas-solid (liquid) separation technologies, the multi-factor cyclone parent-child separator offers significant advantages over traditional cyclone separators in terms of separation accuracy, depth, operational flexibility, and equipment size. Based on my many years of experience and data from domestic and international design platforms for cyclonic gas-solid (liquid) separation, it is feasible to achieve 4N-level separation of solid particles with a size of 5 microns – that is, 99.99% removal of dust particles of 5 microns or larger. Particles with a size of 3 microns or less exhibit significant Brownian behavior; the smaller the particle diameter, the more pronounced this behavior becomes, making separation through dynamic methods increasingly difficult. Particles of 3 microns and smaller, especially those tiny dust particles whose apparent density is already very low, preventing them from aggregating and growing larger due to surface tension. What are the effective methods for separating it from the gas phase? The first approach is to use high-temperature filter elements directly, namely a primary pre-filter equipped with a backup unit, followed by a secondary precision coalescing filter also equipped with a backup unit. The gas that passes through the secondary precision coalescing filter must meet the requirement that the solid content be below 3 mg/Nm^3, and the liquid droplet content must not exceed 1 mg/Nm^3 (as per process requirements). Since the filter elements are prone to clogging with dust, it is necessary to consider replacing them regularly, which requires additional capital investment. There are also ongoing costs associated with the procurement of spare parts for maintenance. In particular, coalescing filter elements are much more expensive than regular filter elements, resulting in high operational and maintenance costs for the system. The second approach involves using electric capture equipment directly, namely a first-stage electric captor equipped with a backup unit, followed by a second-stage electric captor also equipped with a backup unit. The gas emerging from the second-stage electric captor must meet the requirement that the solid load be below 3 mg/Nm^3, and the liquid mist load must not exceed 1 mg/Nm^3 (as per process specifications). Since electrostatic precipitators require consideration for high-temperature insulation, high-temperature sealing, high-temperature corona effects, as well as the issue of electrodes being easily covered by particulate matter, and since they can only function effectively in typical aerosol environments, their application is relatively limited. Regular replacement of internal components is necessary, which leads to increased capital costs for equipment, and the operational and maintenance expenses for such systems are also high. The third method is to use demineralized water in a wet process to remove dust. In some process packages, as soon as the gas stream exits the gasifier, it is washed in a spray scrubber using deionized water to remove large-sized dust particles. I don’t agree. Wet high-temperature dust removal requires a large amount of desalinated water, and it is not economical to use this expensive desalinated water in situations where it isn’t necessary (where dry cyclone dust separators can be used). After the initial dust removal carried out by the upstream dust removal equipment, a first-stage fixed venturi washer and a first-stage multi-factor cyclone separator are used. In the first-stage venturi washer, large amounts of high-speed desalinated water are used to break up the tiny dust particles, thereby wetting them, agglomerating them, and causing them to grow larger. Subsequently, the washing water, liquid droplets, and the dust particles that have been wetted, agglomerated, and enlarged are removed from the gas phase using the first-stage multi-factor cyclone separator ； In the approximately 8%~10% of the airflow that escapes, a small amount of particulate matter remains. This remaining material passes through a secondary adjustable venturi washer along with a secondary multi-factor cyclone separator. In the secondary adjustable venturi washer, high-speed desalination is used to break apart the tiny dust particles, thereby wetting and agglomerating them so that they grow larger. The washing water, liquid droplets, and the agglomerated residual dust particles are then removed from the gas phase using the secondary multi-factor cyclone separator. After treatment with a two-stage adjustable venturi scrubber + a two-stage multi-factor cyclone separator, approximately 0.05% of even finer dust particles remain in the airflow; therefore, the following method is required: 1. Electrostatic dust collection (no additional equipment needed) ； Or 2, Precision coalescing filter (no spare unit required) ； Or 3: An immersion-type scrubber is used to capture extremely small amounts of dust; in addition, an efficient vane-type demister must be installed at the gas outlet at the top of the scrubber to remove any liquid droplets or sludge present in the gas stream. This ensures that the amount of solids carried in the gas stream is below 3 mg/Nm^3, and that the amount of liquid droplets does not exceed 1 mg/Nm^3 (as required by the process specifications). Therefore, following the above approach, the process should be as follows: Step 1 – Dry method: A1: Gasification furnace + multi-factor swirl separator for mother and daughter separation + primary filter (with spare unit) + secondary coalescing filter (with spare unit). Advantages: 1. Reliable product quality ； 2. Less desalinated water is used. Disadvantages: High investment and high operating and maintenance costs. A2: Gasification furnace + multi-factor swirl mother-son separator + primary electrostatic precipitator (including spare unit) + secondary electrostatic precipitator (including spare unit). Advantages: 1. Less desalinated water is used. Disadvantages: High investment and high operating and maintenance costs. II. Wet method: B1: Gasification furnace + jet scrubber + primary fixed venturi scrubber and primary multi-factor swirl parent-child separator + secondary adjustable venturi scrubber and secondary multi-factor swirl parent-child separator + scrubber tower. Advantages: 1. Reliable product quality ； 2. Low investment, no spare parts required. Disadvantages: 1. A large amount of demineralized water is required. III. Wet-dry hybrid method: C1: Gasification furnace + primary multi-factor cyclone mother-son separator + primary fixed venturi scrubber and primary multi-factor cyclone mother-son separator + secondary adjustable venturi scrubber and secondary multi-factor cyclone mother-son separator + scrubber tower. Advantages: 1. Reliable product quality ； 2. Low investment, no spare parts required. Disadvantages: 1. A large amount of desalinated water is required. C2: Gasifier + primary multi-factor swirl mother-son separator + primary fixed venturi scrubber and primary multi-factor swirl mother-son separator + secondary adjustable venturi scrubber and secondary multi-factor swirl mother-son separator + electrostatic precipitator (no standby unit required). Advantages: 1. Reliable product quality ； 2. The investment and operation and maintenance costs are moderate. Disadvantages: 1. A certain amount of deionized water is required. C3: Gasifier + primary multi-factor swirl mother-son separator + primary fixed venturi scrubber and primary multi-factor swirl mother-son separator + secondary adjustable venturi scrubber and secondary multi-factor swirl mother-son separator + secondary precision coalescing filter (no backup unit required). Advantages: 1. Reliable product quality ； 2. The investment and operation and maintenance costs are moderate. Disadvantages: 1. A certain amount of deionized water is required. I welcome colleagues to have in-depth discussions.

Before 2017, there were no dust removal filters of such high quality in China; now they do exist. They can withstand temperatures of 1000℃ and have an emission level of 5 milligrams. Mr. Shao from Yixing Aibo Fiber: 13961591138