Method for treating a filter for filtering particulate matter and filter obtained by said method

Abstract

A method for treating a filter (2) that filters particulate matter from exhaust gas, wherein dry powder (4) is sprayed towards an inlet face of the filter (2), the dry powder being entrained in a primary gas stream to pass through the inlet face to contact a porous structure of the filter. Back pressure of the filter (2) is monitored during spraying of the dry powder (4), and the spraying of the dry powder (4) is stopped when the back pressure of the filter (2) reaches a desired value. The desired value can be equal to an absolute back pressure, or a predetermined target back pressure of the filter minus an offset pressure, or an estimated back pressure of the filter.

Description

A method for treating a filter that filters particulate matter and a filter obtained by said method Technical Field

[0001] This disclosure relates to improvements to particulate filters for filtering particulate matter from exhaust gases, or improvements related to particulate filters for filtering particulate matter from exhaust gases. Specifically, the invention relates to a method of coating a filter comprising a porous substrate having an inlet surface and an outlet surface, wherein the inlet surface is separated from the outlet surface by a porous structure. The filter may be a wall-flow filter. Background Technology

[0002] There are concerns about particulate matter (PM) emissions (commonly known as soot) from internal combustion engines, particularly diesel and gasoline engines used in automotive applications. The main concern is related to potential health effects, especially the presence of very small particles in the nanometer range.

[0003] Diesel particulate filters (DPFs) and gasoline particulate filters (GPFs) are manufactured using a variety of materials, including sintered metals, ceramics, or metal fibers. The most common type in actual mass production is the wall-flow type, made of porous ceramic materials, which are manufactured as a monolithic array of numerous small channels extending along the length of the body. Alternating channels are blocked at one end, thus forcing exhaust gas through the porous ceramic channel walls, which prevent most particles from passing through, allowing only filtered gas to enter the environment. Commercially produced ceramic wall-flow filters include those made of cordierite, various forms of silicon carbide, and aluminum titanate. The actual shape and size of the filters used in vehicles, as well as characteristics such as channel wall thickness and porosity, depend on the application of interest. The average pore size in the filter channel walls of ceramic wall-flow filters through which gas passes is typically in the range of 5 μm to 50 μm, and usually around 20 μm. In stark contrast, most diesel particulate matter from high-speed diesel engines in modern passenger cars is very small, for example, 10 nm to 200 nm.

[0004] Some particulate matter (PM) may remain within the pore structure of the filter wall, and in some applications this can gradually accumulate until the pores are bridged by a network of PM, which then allows for the easy formation of a particulate cake on the inner wall of the filter channels. This particulate cake is an excellent filter medium, and its presence provides very high filtration efficiency. In some applications, soot is continuously burned on the filter during deposition, preventing the accumulation of particulate cake. For some filters, such as light diesel particulate filters, it is necessary to periodically remove captured PM from the filter to prevent the buildup of excessive back pressure, which is detrimental to engine performance and can lead to poor fuel economy. Therefore, in diesel applications, the retained PM is removed from the filter by burning it in air in a process during which the amount of available air and excess fuel required to reach the high temperature needed to ignite the retained PM is carefully controlled. At the end of this process, commonly referred to as regeneration, removing the last remaining particles from the filter can result in a significant decrease in filtration efficiency and a burst of many small particles into the environment. Therefore, the filter may have low filtration efficiency when used for the first time and subsequently after each regeneration event and also during the latter part of each regeneration process.

[0005] Therefore, it is desirable to improve and / or maintain filtration efficiency at any time, such as during the early life of the filter when it is first used, and / or during and immediately after regeneration, and / or when the filter is loaded with soot.

[0006] Liu, X., Szente, J., Pakko, J., Lambert, C., et al., “Using Artificial Ash to Improve GPF Performance at Zero Mileage,” SAE Technical Paper 2019-01-0974, 2019, doi:10.4271 / 2019-01-0974 describes a process for loading a bare filter substrate with submicron alumina particles generated by an atomizer to create an “artificial ash” coating to reduce soot emissions during cold start conditions. The process consists of: generating aerosol particles by atomizing a liquid suspension with compressed air; drying the resulting ash-containing droplets by passing them through an oven; and capturing the dried ash particles by filtration to load them into a filter. This process utilizes… A high-capacity atomizer (model PLG-2100, PALAS, Germany) was used to provide a flow rate of 100 l / min for all sizes of bricks. Filter loading was monitored by recording the pressure drop across the filter and the PM concentrations before and after the filter using a DustTrak aerosol monitor (TSI, Minnesota, USA). While the process showed reduced soot emissions during cold start conditions, it is limited to substances that can be spray-dried, requires an atomizer, drying oven, and aerosol monitor, and the artificial ash loading conditions may be constrained by the conditions required to achieve complete drying of the liquid aerosol before it reaches the filter substrate.

[0007] WO2011 / 151711 describes a method for manufacturing a filter for filtering particulate matter from exhaust gases emitted from a lean-burning internal combustion engine. The filter includes a porous substrate having an inlet surface and an outlet surface, wherein the inlet surface is separated from the outlet surface by a porous structure containing pores of a first average pore size. The inlet surface includes a bridging network comprising interconnected refractory material particles on the pores of the porous structure. The method includes the step of contacting the inlet surface of the filter substrate with an aerosol comprising a refractory material in the form of dry powder. While the described process shows a reduction in PM emissions upon initial use and subsequently after each regeneration event, improvements to the process are desired, particularly improvements regarding the controllability of the parameters of the resulting filter.

[0008] US2019 / 0048771 describes an engine exhaust particulate filter comprising a porous substrate having inert nanoparticles at a concentration ranging from 0.01 g / L to 60 g / L relative to the filter volume of the substrate, a portion of the nanoparticles being arranged to form a regenerable porous structure configured to capture particulates from the exhaust gas stream. While the filter is intended to provide an improvement in zero-mileage efficiency of particulate filters, improvements in the process are desired, particularly in process controllability and flexibility.

[0009] The applicant has discovered (as fully described in its application GB1911704 filed on August 15, 2019, which is incorporated herein by reference in its entirety) that filters with improved filtration efficiency during the early lifespan of the filter upon initial use and / or during and immediately thereafter during regeneration and / or when the filter is loaded with soot can be obtained by a treatment method comprising the following steps:

[0010] a) The dry powder is contained in the storage container;

[0011] b) Positioning a filter in a filter holder, the filter comprising a porous substrate having an inlet face and an outlet face separated by a porous structure;

[0012] c) A primary airflow through the porous structure of the filter is established by applying a pressure reduction to the outlet surface of the filter;

[0013] d) Transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; and

[0014] e) Using the spraying device, spray the dry powder toward the inlet face of the filter, such that the dry powder is entrained in the primary airflow and passes through the inlet face of the filter to contact the porous structure.

[0015] In GB1911704, the applicant describes how the dry powder may preferably comprise one or more of pyrolytic alumina, pyrolytic silica, pyrolytic titanium dioxide, silica aerogel, alumina aerogel, carbon aerogel, titanium dioxide aerogel, zirconium oxide aerogel, or cerium dioxide aerogel. Specifically, an example of a filter coated with pyrolytic alumina having a tap density of 0.05 g / L and a d50 of 5.97 microns is described.

[0016] Although this treatment method has been found to produce filters with improved filtration efficiency, further improvements are needed in the treatment of such filters, specifically, improvements in the durability of the treated filters.

[0017] Therefore, the applicant has discovered (as fully described in its application GB2002483 filed on February 21, 2020, the entire contents of which are hereby incorporated by reference) that the durability of treated filters can be improved by using dry powder containing a metal compound for forming metal oxides by thermal decomposition during the spraying process.

[0018] In GB2002483, the applicant describes how using a metal compound that decomposes into a metal oxide as a dry powder can substantially improve the durability of the treated filter compared to treatment with metal oxides (including, for example, pyrolytic alumina), particularly the substantial improvement in the ability of the dry powder to remain adhered to the porous structure and resist detachment from the porous structure during subsequent operation of the filter.

[0019] Surprisingly, the applicant has discovered that improved adhesion of these dry powders can be achieved without the presence of any additional adhesives or adhesion promoters, or without the need for any high-temperature sintering of the filter. Specifically, it has been surprisingly found that good adhesion can be produced using such dry powders while maintaining high filtration efficiency and acceptable cold flow back pressure.

[0020] Although the processing methods in GB1911704 and GB2002483 have been found to be effective in producing improved filters, there is still a desire to improve these methods. Summary of the Invention

[0021] In a first aspect, this disclosure provides a method for treating a filter that filters particulate matter from exhaust gas, the method comprising the following steps:

[0022] a) The dry powder is contained in the storage container;

[0023] b) Positioning a filter in a filter holder, the filter comprising a porous substrate having an inlet face and an outlet face separated by a porous structure;

[0024] c) A primary airflow through the porous structure of the filter is established by applying a pressure reduction to the outlet surface of the filter;

[0025] d) Transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter;

[0026] e) Using the spraying device, spray the dry powder toward the inlet face of the filter, such that the dry powder is entrained in the primary airflow and passes through the inlet face of the filter to contact the porous structure; and

[0027] f) Monitor the back pressure of the filter during at least step e), and stop the spraying of the dry powder toward the inlet face of the filter when:

[0028] p BP ≥p target - p offset

[0029] in,

[0030] p BP This is the back pressure of the filter;

[0031] p 目标 The predetermined target back pressure for the filter; and

[0032] p 偏移 For the pre-selected offset pressure.

[0033] Advantageously, this method allows the back pressure of the produced filter to more closely match the predetermined target back pressure. This method helps limit any overshoot of the target back pressure and reduces the occurrence of target back pressure overshoot.

[0034] The predetermined target back pressure p of the filter 目标 This can be the absolute back pressure of the filter. For example, the predetermined target back pressure p of the filter. 目标 The target back pressure can be from 20 mbar to 180 mbar. Alternatively, the predetermined target back pressure p of the filter... 目标 This can be the relative back pressure of the filter. For example, the predetermined target back pressure p of the filter. 目标 This can be the back pressure related to the initial back pressure of the filter before the dry powder is sprayed. For example, the predetermined target back pressure p of the filter. 目标 The initial back pressure of the filter can be 105% to 200%, optionally 125% to 150%.

[0035] In step f), when p BP ≥p 目标 -p 偏移 For the minimum time interval t min When true, the spraying of the dry powder toward the inlet face of the filter can be stopped, wherein t min ≥0.1s, optionally ≥0.5s, optionally ≥1.0s. In this way, the method can be configured to avoid the cessation of the spray due to short-term fluctuations in the back pressure reading, which may be caused by, for example, system noise and do not reflect the true back pressure of the filter.

[0036] p 偏移 It can be, for example, 1 mbar to 10 mbar, optionally 2 mbar to 5 mbar, optionally 3 mbar to 5 mbar. For example, this p 偏移Can be used in p 目标 For cases ranging from 20 mbar to 180 mbar.

[0037] In step f), the back pressure of the filter can be continuously monitored at least during step e). Optionally, this can be achieved by using ≥1 sample.s -1 Optional ≥5 samples. -1，任选 ≥10 samples.s -1 The sampling rate is used to measure the back pressure to continuously monitor it.

[0038] The method may further include, in step c), monitoring the back pressure of the filter and allowing the primary airflow through the porous structure of the filter until the back pressure of the filter stabilizes before starting step d). In this way, a more accurate and reliable measurement of the initial back pressure of the filter can be obtained. Additionally, this stable back pressure also indicates a stable flow of the primary airflow through the porous structure of the filter. The predetermined target back pressure p of the filter... 目标 This can be related to the stable back pressure monitored in step c). For example, the predetermined target back pressure p of the filter. 目标 It can be 105% to 200%, optionally 125% to 150%, of the stable back pressure monitored in step c).

[0039] The method may further include the steps of: monitoring the back pressure of the filter, and maintaining the primary airflow through the porous structure of the filter after the spraying of the dry powder has stopped, until the back pressure of the filter stabilizes. This improves the ability to determine that the correct cold flow back pressure (CFBP) of the filter has been obtained.

[0040] The back pressure of the filter can be considered stable under the following conditions:

[0041] i) The primary airflow velocity is within 0.5% of the predetermined velocity;

[0042] ii) The first derivative of the primary airflow velocity is ≤ ±0.15m. 3 hr -1 .s -1 ;as well as

[0043] iii) The first derivative of the back pressure of this filter is ≤ ±1.5 mbar.s -1 .

[0044] The back pressure p BP It can be the absolute back pressure measured relative to atmospheric pressure.

[0045] This method can be implemented using a coating device to perform at least steps a) to f), wherein the predetermined target back pressure p of the filter 目标 The following steps can be used to calculate:

[0046] - Select the desired back pressure for the filter, as will be measured by testing equipment different from the coating equipment;

[0047] - Establish a calibration map to convert the back pressure measured on the test equipment to the back pressure measured on the coating equipment; and

[0048] - Use the calibration chart to convert the desired back pressure to establish the predetermined target back pressure p 目标 .

[0049] Advantageously, using a calibration chart in this manner allows the final back pressure of the filter to be targeted at a figure that will be measured on a test device, without having to use that test device during the filter coating process. This can be advantageous because the filter's back pressure will typically be measured by the filter purchaser on their own test device to confirm that the filter meets their requirements. For example, the purchaser may test the filter on a test device such as the Superflow Flow Bench 1050, available from Superflow of Sussex, WI, USA. When testing on the Superflow Flow Bench 1050, a back pressure of, for example, 65 mbar ± 5 mbar may be required for the filter. Using a calibration chart allows selection of a predetermined target back pressure p, as measured by the coating device. 目标 This is to achieve the desired back pressure on Superflow FlowBench 1050.

[0050] In a second aspect, this disclosure provides a method for treating a filter that filters particulate matter from exhaust gas, the method comprising the following steps:

[0051] a) The dry powder is contained in the storage container;

[0052] b) Positioning a filter in a filter holder, the filter comprising a porous substrate having an inlet face and an outlet face separated by a porous structure;

[0053] c) A primary airflow through the porous structure of the filter is established by applying a pressure reduction to the outlet face of the filter while monitoring the back pressure of the filter, and the primary airflow is passed through the porous structure of the filter until the back pressure of the filter stabilizes.

[0054] d) After establishing the stable back pressure of the filter, the dry powder is transferred from the reservoir to a spray device located upstream of the inlet face of the filter;

[0055] e) Using the spraying device, spray the dry powder toward the inlet face of the filter, so that the dry powder is entrained in the primary airflow and passes through the inlet face of the filter to contact the porous structure, while monitoring the back pressure of the filter.

[0056] f) Stop the spraying of the dry powder toward the inlet face of the filter; and

[0057] g) Continue to monitor the back pressure of the filter, and after the spraying of the dry powder has stopped, maintain the primary airflow through the porous structure of the filter until the back pressure of the filter stabilizes.

[0058] When the first derivative of the primary airflow velocity is ≤ ±Xm 3 hr -1 .s -1 When X = 0 to 0.30, or optionally X = 0.10 to 0.20 or X = 0.15, the back pressure of the filter can be considered stable.

[0059] Additionally or alternatively, when the first derivative of the back pressure of the filter is ≤ ±Y mbar.s -1 When the back pressure of the filter is stable, Y = 0.5 to 3.0, optionally Y = 1.0 to 2.0, optionally Y = 1.5.

[0060] Additionally or alternatively, the back pressure of the filter is considered stable when the primary airflow velocity is within Z% of a predetermined velocity, where Z = 1.5, optionally Z = 1.0, and optionally Z = 0.5.

[0061] The back pressure can be an absolute back pressure measured relative to atmospheric pressure. The back pressure of the filter can be measured using a pressure sensor; optionally, a single pressure sensor located in the filter retainer or another housing fluidly connected to the outlet face of the filter.

[0062] In a third aspect, this disclosure provides a method for treating a filter that filters particulate matter from exhaust gas, the method comprising the following steps:

[0063] a) The dry powder is contained in the storage container;

[0064] b) Positioning a filter in a filter holder, the filter comprising a porous substrate having an inlet face and an outlet face separated by a porous structure;

[0065] c) A primary airflow through the porous structure of the filter is established by applying a pressure reduction to the outlet surface of the filter;

[0066] d) Transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter;

[0067] e) Using the spraying device, spray the dry powder toward the inlet face of the filter, such that the dry powder is entrained in the primary airflow and passes through the inlet face of the filter to contact the porous structure; and

[0068] f) Monitor the back pressure of the filter during at least step e), and stop the spraying of the dry powder toward the inlet face of the filter when:

[0069] p estimate ≥ p target

[0070] in,

[0071] p 目标 The predetermined target back pressure for the filter; and

[0072] p 估计 This is the estimated final back pressure for the filter;

[0073] p is calculated by extrapolating the back pressure data of the filter obtained during step f). 估计 .

[0074] Advantageously, this method allows the back pressure of the produced filter to more closely match the predetermined target back pressure. This method helps limit any overshoot of the target back pressure and reduces its occurrence. Specifically, for filters with different loading characteristics, this method allows the back pressure to better match the predetermined target back pressure. For example, different filters (even within a batch of filters) may exhibit different rates of back pressure change when loaded with dry powder. The third aspect of the method helps accommodate different loading characteristics by using an estimated final back pressure parameter that can be calculated for each individual filter. Therefore, this method enables the production of filters with low variations in the filter's CFBP.

[0075] The measured back pressure data can be extrapolated forward by T over time. s The estimated final back pressure p of the filter is calculated in seconds. 估计 T s Settlement time.

[0076] This method can be performed on a coating device, and the settling time T s It can be a variable related to the coating equipment and can preferably be independent of the filter.

[0077] For example, the settling time of a coating device can be affected by design aspects such as valve closing time, powder spray rate, flow duct size, and any hysteresis in pressure measurements taken by pressure sensors. Therefore, the settling time T... s The parameters can be selected to characterize the performance of the coating equipment. Settling time T s Theoretical calculations can be performed on the coating equipment. Alternatively, the settling time T of the coating equipment can be determined experimentally by testing sample filters. s .

[0078] The estimated final back pressure p of the filter can be calculated by curve fitting the measured back pressure data and extrapolating the fitted curve forward over time. 估计 .

[0079] Any of the above aspects may additionally include one or more of the following features:

[0080] In some examples, the dry powder may comprise or consist of one or more refractory powders, preferably including one or more pyrolytic refractory powders and / or one or more aerogels. The one or more pyrolytic refractory powders may be produced by a pyrochemical process, such as flame pyrolysis. The one or more pyrolytic refractory powders may include one or more of pyrolytic alumina, pyrolytic silica, pyrolytic titanium dioxide, other pyrolytic metal oxides, and pyrolytic mixed oxides. The one or more aerogels may include one or more of silica aerogel, alumina aerogel, carbon aerogel, titanium dioxide aerogel, zirconium oxide aerogel, cerium dioxide aerogel, metal oxide aerogel, and mixed oxide aerogel.

[0081] In these examples, the method may further include a maximum loading of a filter providing <10 g / L of dry powder, optionally <5 g / L of dry powder, optionally <2 g / L of dry powder. The dry powder may have a density of less than 0.10 g / cm³. 3 Optionally less than 0.08 g / cm³ 3 Optionally less than 0.07 g / cm³ 3 Optionally less than 0.06 g / cm³ 3 Optionally less than 0.05 g / cm³ 3 The tap density. The dry powder may have a d50 (by volume) of less than 25 micrometers, preferably less than 20 micrometers, and more preferably less than 10 micrometers.

[0082] In some other examples, the dry powder may contain or consist of a metal compound for forming a metal oxide by thermal decomposition. The dry powder may consist of a single metal compound, or it may consist of a mixture or blend, or a continuous dose of two or more metal compounds. The metal compound, or each metal compound, may contain one or more metal cations. In the presence of multiple metal cations, these metal compounds may use the same or different metals. The metal compound may contain or consist of: metal hydroxides, metal phosphates, metal carbonates, metal sulfates, metal perchlorates, metal iodides, metal oxalates, metal acetates, metal chlorates, or mixtures thereof. The metal of the metal compound may contain or consist of: one or more of magnesium, calcium, strontium, barium, aluminum, zirconium, manganese, lithium, iron, cobalt, nickel, copper, or gallium. The dry powder may also contain metal oxides or mixed metal oxides. Preferably, the dry powder contains 90% by weight or more of a metal compound for forming a metal oxide by thermal decomposition, and 10% by weight or less of a metal oxide or mixed metal oxide. More preferably, the dry powder contains 95% by weight or more of a metal compound for forming a metal oxide by thermal decomposition, and 5% by weight or less of a metal oxide or mixed metal oxide. Optionally, the dry powder contains 99% by weight or more of a metal compound for forming a metal oxide by thermal decomposition, and 1% by weight or less of a metal oxide or mixed metal oxide. The metal in the metal oxide or mixed metal oxide may contain or consist of one or more of the following: aluminum, magnesium, calcium, strontium, barium, aluminum, zirconium, manganese, lithium, iron, cobalt, nickel, copper, or gallium. Preferably, the dry powder contains or consists of the following: metal hydroxides, metal phosphates, metal carbonates, or mixtures thereof. The metal hydroxide may be selected from the group consisting of: magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide. The metal phosphate may be selected from the group consisting of: magnesium phosphate, calcium phosphate, strontium phosphate, and barium phosphate. The metal carbonate may be selected from the group consisting of: magnesium carbonate, calcium carbonate, strontium carbonate, and barium carbonate.

[0083] In these examples, the method may further include providing a maximum filter loading of 10 g / L to 40 g / L, optionally 15 g / L to 30 g / L, optionally about 20 g / L. The dry powder may have a concentration of 1 g / cm³. 3 Up to 3g / cm 3 Optional 1.5g / cm 3 Up to 2.5g / cm 3 Approximately 2g / cm³ (optional) 3The tap density. The d50 (by volume) of the dry powder can be less than 10 micrometers, optionally less than 5 micrometers, optionally about 2 micrometers. Surprisingly, the applicant has discovered that using metal hydroxide, metal phosphate, and / or metal carbonate powders with such relatively small particle size can still produce an effective wall-mounted filtration layer on the walls of a porous substrate.

[0084] Dry powder can consist of a single powder type or a mixture of powder types.

[0085] The method may further include the step of calcining the filter. In examples where the dry powder contains a metal compound that forms a metal oxide through thermal decomposition, or is composed of such a metal compound, the calcination of the filter may be carried out at a temperature selected to produce the thermal decomposition of the dry powder. Preferably, at least a majority of such dry powder, more preferably all or substantially all of the dry powder, may thermally decompose during calcination. However, it should be understood that a residual amount of non-decomposed dry powder may remain after calcination.

[0086] The calcination temperature can be selected to be at least 150°C, optionally at least 250°C, and optionally at least 500°C. In some embodiments, it is preferred that the calcination temperature is not greater than 550°C. However, in other embodiments, the calcination temperature can be selected to be greater than 550°C. The calcination temperature can be selected to be up to 900°C, optionally up to 1150°C. In one example, the calcination temperature can be selected to be between 300°C and 500°C. In another example, the calcination temperature can be selected to be about 520°C. In another example, the calcination temperature can be selected to be about 580°C. In yet another example, the calcination temperature can be selected to be about 900°C.

[0087] Calcination can be carried out for a period of 30 to 90 minutes, optionally 30 to 60 minutes. In one example, the period is about 35 minutes. In another example, the period is about 60 minutes. Within any such calcination, the residence time of each filter is preferably 1 to 15 minutes, preferably 5 to 10 minutes.

[0088] In this document, "calcination" refers to the process of firing a filter in air at a desired temperature for a desired length of time, typically but not exclusively. However, it should be understood that even with microwave assistance, it is generally not possible to immediately raise the filter temperature to the specified temperature. Instead, those skilled in the art will understand that in a typical calcination process, the filter is fed into a dynamic furnace via a belt conveyor or mounted on a tray in a static oven, and in either case, the furnace or oven temperature will rise to the desired temperature; in the case of a furnace, this can be achieved by heating the internal zones to the desired temperature. That is, raising the filter to the desired temperature may take some time. Therefore, the calcination temperature as defined herein refers to the preferred peak temperature at which the filter is calcined. Within a relatively short period of the entire calcination cycle (the so-called "residence time"), the filter may eventually reach and remain at the peak temperature. The inventors have discovered that the duration of residence time is important for achieving the desired adhesion of the powder to itself and, in particular, to the porous structure of the filter. Therefore, "calcination" as used herein refers to the entire duration or cycle of heating, residence time, and cooling of the calcination process. Therefore, the calcination process as a whole (including heating, residence time, and cooling) may be 90 minutes long, but within these 90 minutes, the residence time may only be 1 to 15 minutes.

[0089] Without being bound by theory, it is believed that applying metal hydroxides, metal phosphates, metal carbonates, or mixtures thereof as dry powder followed by calcination can produce a particularly effective porous layer comprising at least a portion of the dry powder retained on the walls of a porous substrate. Specifically, it is believed that the decomposition of metal hydroxides, metal phosphates, and / or metal carbonates into metal oxides creates a cementing effect between the dry powder particles and between the dry powder and the porous substrate.

[0090] The calcined vehicle exhaust filter achieves a filtration efficiency greater than 90%, preferably greater than 95%, more preferably greater than 98%, and more preferably greater than 99% with a soot loading of 0.02 g / L. The calcined vehicle exhaust filter has a filtration efficiency of 600 m... 3 The back pressure at a flow rate of / hour can be 20 mbar-180 mbar.

[0091] The calcined vehicle exhaust filter exhibits a substantially linear load back pressure response when loaded with soot greater than 0.1 g / L, preferably greater than 0.05 g / L.

[0092] The method may further include coating the filter with a carrier coating, preferably a catalyst carrier coating.

[0093] Dry powder can be transferred from the reservoir to the spray device using a secondary airflow separate from the primary airflow; and optionally, the secondary airflow is controllable independently of the primary airflow.

[0094] Secondary airflow may include compressed gas flow, preferably air flow.

[0095] The secondary airflow can be applied as a single burst or multiple intermittent bursts.

[0096] A vacuum generator can be used to create the primary airflow through the porous structure of the filter. The level of pressure reduction generated by the vacuum generator can be controlled independently of the speed or mass rate at which the dry powder is transferred from the reservoir to the spray device.

[0097] The volumetric flow rate of the primary airflow can be 10 m³ / s. 3 / hour to 5000m 3 / hour, preferably 400m 3 / hour to 2000m 3 / hour, preferably 600m 3 / hour to 1000m 3 / Hour.

[0098] A pressure sensor, preferably a single pressure sensor, can be used to monitor the back pressure. The pressure sensor, preferably a single pressure sensor, can be located in the filter retainer or another housing where the fluid is connected to the outlet side of the filter. The same pressure sensor, preferably the same single pressure sensor, can be used to monitor the back pressure of the filter during at least steps c) and f).

[0099] In step e), dry powder can be sprayed from one or more outlets of the spraying device.

[0100] One or more outlets of the spray device may have an orifice size of 1 mm to 10 mm, optionally 0.5 mm to 5.0 mm, optionally 1.0 mm to 2.5 mm, optionally 1.0 mm to 2.0 mm.

[0101] Dry powder can be sprayed from one or more fixed outlets of the spraying device. Alternatively, dry powder can be sprayed from one or more movable outlets of the spraying device, preferably from one or more oscillating outlets.

[0102] The method may further include, in step e), guiding the dry powder from the spraying device to the inlet face of the filter within a flow conduit. The flow conduit provides an unobstructed flow path between the spraying device and the inlet face of the filter. Alternatively, the flow conduit may include a flow conditioner inserted between the spraying device and the inlet face of the filter to facilitate dispersion of the dry powder within the airflow. The flow conditioner may include one or more of a static mixer, a mesh, a sieve, a baffle, and an orifice plate.

[0103] The filter inlet face can be located at a distance greater than 10 cm, optionally greater than 20 cm, from the nozzle outlet of the spray nozzle. Particular benefits can be found when the filter inlet face is located at a distance greater than 75 cm, optionally greater than 100 cm, from the nozzle outlet of the spray nozzle. Advantageously, such spacing increases the percentage area of ​​the filter's inlet face for receiving dry powder, resulting in improved homogeneity of the dry powder applied to the filter. Additionally or alternatively, the spray nozzle outlet nozzle can be located at a distance from the filter inlet face, which is up to four times the diameter of the filter inlet face.

[0104] The method may further include dispensing dry powder from the storage container in step d). Dispensing may include dispensing by one or more of the following: by weight, by volume, by particle number, and by time.

[0105] The method may include feeding dry powder to the dispensing device by weight.

[0106] A loss-in-weight feeder can be used for batching.

[0107] In step a), the dry powder may be contained in one or more hoppers.

[0108] In step b), the filter can be positioned in the retainer with the inlet face at the top in a vertical orientation. In step d), the spray device can be vertically positioned above the inlet face; and preferably, the spray direction of the spray device can be coaxial with the longitudinal axis of the filter; and preferably, the spray direction and the longitudinal axis coincide.

[0109] Porous substrates can be wall-flow filters.

[0110] This disclosure extends to filters that can be obtained by any of the methods described above.

[0111] The filter can be a catalytic soot filter (CSF), a selective catalytic reduction filter (SCRF), a lean NOx trap filter (LNTF), or a gasoline particulate filter (GPF).

[0112] In this specification, the term "filter" refers to a porous substrate having a porous structure suitable for filtering particulate matter from exhaust gases. The porous substrate can be formed, for example, from sintered metal, ceramic, or metal fibers. Filters can be of the wall-flow type made of porous materials (e.g., ceramic), manufactured as a monolithic array of numerous small channels extending along the length of the substrate. For example, filters can be formed from cordierite, various forms of silicon carbide, or aluminum titanate.

[0113] The filter can be a "bare" filter or alternatively a filter with incorporated catalytic capabilities (such as oxidation, NOx capture, or selective catalytic reduction activity). The porous substrate can include a composition of porous structures coated with the filter (referred to as a support coating). The support coating can be a catalytic support coating. The catalytic support coating can include a catalyst selected from the group consisting of: hydrocarbon traps, three-way catalysts (TWCs), NOx absorbers, oxidation catalysts, selective catalytic reduction (SCR) catalysts, lean NOx catalysts, and any combination of two or more of these. The catalyst (e.g., TWCs, NOx absorbers, oxidation catalysts, hydrocarbon traps, and lean NOx catalysts) can contain one or more platinum group metals, particularly those selected from the group consisting of platinum, palladium, and rhodium.

[0114] Therefore, the coated filter can be, for example, a catalytic soot filter (CSF), a selective catalytic reduction filter (SCRF), a lean NOx trap filter (LNTF), a gasoline particulate filter (GPF), an ammonia leak catalyst filter (ASCF), or a combination of two or more of them (e.g., a filter including a selective catalytic reduction (SCR) catalyst and an ammonia leak catalyst (ASC).

[0115] The shape and dimensions of a filter (e.g., characteristics such as channel wall thickness and porosity) can vary depending on the intended application of the filter. A filter can be configured for use with an internal combustion engine to filter exhaust gases emitted by that engine. The internal combustion engine can be a gasoline spark-ignition engine. However, when configured for use with an internal combustion engine in the form of a diesel or gasoline engine, the filter has a specific application.

[0116] In this specification, the term "dry powder" refers to a particulate composition that is not suspended or dissolved in a liquid. This does not necessarily mean the complete absence of all water molecules. The dry powder is preferably free-flowing.

[0117] In this specification, the term "tap density" refers to the tap density of a powder measured by 1250 taps according to Method 1 of Section 2.9.35 of the European Pharmacopoeia 7.0.

[0118] In this specification, the term "g / l" (grams per liter) refers to the mass of the dry powder divided by the volume of the filter.

[0119] In this specification, when referring to the amount of dry powder, the terms "load" and "mass load" refer to the mass of powder added to the filter, and can be measured by weighing the filter before and after the powder is applied to it.

[0120] In this specification, the term "d50 (by volume)" refers to Malvern Panalytical Ltd. of Malvern, UK, which uses Aero s dispersion units. d50 (by volume) measurement results from 3000. Dispersion conditions: air pressure = 2 barg, feed rate = 65%, hopper gap = 1.2 mm. (Based on Malvern) The instructions in the 3000 user manual provide guidance on setting the refractive index and absorption parameters.

[0121] In this specification, the term "vacuum generator" refers to a device or combination of devices used to generate a reduced pressure. Non-limiting examples of suitable devices include vacuum generators operating according to the Venturi principle, vacuum pumps such as rotary vane and liquid ring vacuum pumps, and regenerative blowers.

[0122] In this specification, the term "pressure sensor" refers to a device or combination of devices used to measure absolute pressure and / or relative pressure. Non-limiting examples of suitable devices include pressure transducers that can be diaphragm pressure transducers. For example, the P30 pressure transmitter, available from WIKA Alexander Wiegand SE&Co.KG in Klingenberg, Germany, can be used.

[0123] In this specification, the term "controller" refers to a function that may include hardware and / or software. A controller may include a control unit or a computer program that runs on dedicated or shared computing resources. A controller may include a single unit or may consist of multiple subunits operatively connected. A controller may reside on a single processing resource or may be distributed across spatially separated processing resources. A controller may include a microcontroller, one or more processors (such as one or more microprocessors), memory, configurable logic, firmware, etc.

[0124] In this specification, ranges and quantities may be expressed as “about” a specific value or range. “About” also includes exact quantities. For example, “about 2 micrometers” means “about 2 micrometers” as well as “2 micrometers”. Generally, the term “about” includes quantities expected to be within experimental error. The term “about” can include values ​​within 5% less to 5% greater than the provided value. For example, “about 2 micrometers” means “between 1.9 micrometers and 2.1 micrometers”.

[0125] In this specification, the expression "composed of" means that the dry powder is essentially composed of only the specified ingredients, excluding unavoidable impurities that are commonly encountered and will be recognized by those skilled in the art. Attached Figure Description

[0126] Aspects and embodiments of this disclosure will now be described by way of example only with reference to the accompanying drawings, in which:

[0127] Figure 1 is a schematic diagram of an apparatus for treating a filter that filters particulate matter from exhaust gas according to the present disclosure;

[0128] Figure 2 is a flowchart illustrating a method for manufacturing a filter according to the present disclosure, which is incorporated into a method for processing a filter using the apparatus of Figure 1;

[0129] Figure 3 is a flowchart illustrating a method for treating a filter that filters particulate matter from exhaust gas using the apparatus of Figure 1;

[0130] Figure 4 is a graph showing the back pressure of two filters treated with dry powder of different masses as a function of time.

[0131] Figures 5 and 6 are graphs showing the back pressure of two filters subjected to two different schemes for spray drying powder as a function of time.

[0132] Figure 7 shows a calibration diagram of cold flow back pressure (CFBP) on the comparison coating and testing equipment;

[0133] Figures 8 and 9 show further calibration diagrams of the CFBP on the comparative coating and testing equipment;

[0134] Figure 10 shows the curves of back pressure variation over time for the eight filters;

[0135] Figure 11 shows the back pressure versus time curves for two of the eight filters in Figure 10; and

[0136] Figure 12 is a graph showing the back pressure of one of the eight filters in Figure 10 under two different schemes for spray dry powder. Detailed Implementation

[0137] Readers in the art will recognize that, unless the present context otherwise teaches, one or more features of one aspect or embodiment of this disclosure may be combined with one or more features of any other aspect or embodiment of this disclosure.

[0138] An example of an apparatus for performing the methods of this disclosure will now be described with reference to FIG1, which illustrates a schematic diagram of an apparatus 1 for treating a filter 2 that filters particulate matter from exhaust gas. The filter 2 is of the type comprising a porous substrate having an inlet surface and an outlet surface separated by a porous structure.

[0139] The device 1 includes a reservoir 3 for containing dry powder 4. A filter retainer 5 is provided for holding the filter 2. A vacuum generator 6 is provided for establishing a primary airflow through the porous structure of the filter 2 during use by applying reduced pressure to the outlet face of the filter 2. A conveying device 8 is provided for conveying the dry powder 4 from the reservoir 3 to a spraying device 7. A spraying device 7 is provided for receiving the dry powder 4 from the conveying device 8 and spraying the dry powder 4 toward the inlet face of the filter 2. A controller 9 is provided, which is configured to control the operation of the device 1.

[0140] The reservoir 3 can receive dry powder 4 from the dry powder inlet 11. The dry powder inlet 11 can be the output of the upstream stacked supply of dry powder. For example, the dry powder inlet 11 can be a conduit connected upstream to another reservoir of dry powder 4. The dry powder inlet 11 can represent manual, semi-automatic, or automatic refilling of the reservoir 3 through a cover or opening of the reservoir 3.

[0141] The reservoir 3 may include one or more hoppers. The reservoir 3 may include a single hopper. In the example shown in FIG1, the reservoir 3 includes a first hopper 12 and a second hopper 13. The second hopper 13 may be downstream of the first hopper 12 to receive dry powder 4 as an output from the first hopper 12. One or more hoppers may be housed in a separate housing. Alternatively, one or more hoppers may be housed in a single housing. One or more hoppers may include one or more chambers of a single container.

[0142] The storage container 3 may include a dispensing device 15. The dispensing device 15 may dispense dry powder 4 by one or more of the following: weight, volume, number of particles, and time. The dispensing device 15 may be located at or near the outlet of the storage container 3. The dispensing device 15 may be located at or near the outlet of one or more hoppers of the storage container 3. The dispensing device may be located at or near the outlet of the first hopper 12.

[0143] The feeding device 15 can feed dry powder 4 from the storage tank 3 by weight.

[0144] The feeding device 15 may be a loss-in-weight feeder. The feeding device 15 may be a volumetric feeder including a helical or threaded arrangement. Non-limiting examples of suitable feeding devices include those available from Coperion GmbH, Stuttgart, Germany. The K-Tron Type K2-ML-T35 gravity twin-screw feeder is available from All-Fill International Ltd, Sandy, UK. Series S1 Micro-Fill and Series 10 gravity or volumetric screw filler.

[0145] The conveying device 8 transports the dry powder 4 from the storage container 3 to the spraying device 7. The conveying device 8 can feed the dry powder 4 at least partially toward the spraying device 7 in a gravimetric or volumetric manner.

[0146] The conveying device 8 may include one or more components. The conveying device 8 may include one or more conduits, such as channels, pipes, hoses, etc.

[0147] In cases where the reservoir 3 includes more than one hopper, the conveying device 8 can convey the dry powder 4 between the hoppers. The conveying device 8 can feed the dry powder 4 between the hoppers in a gravimetric or volumetric manner. The conveying device 8 may include a first conduit 14 extending between the first hopper 12 and the second hopper 13. The first conduit 14 can extend from the first housing to the second housing. Alternatively, the first conduit 14 can extend from the first chamber to the second chamber of a single container. The dry powder 4 can be fed along the first conduit 14 in a gravimetric manner.

[0148] The conveying device 8 may include a second conduit 16 extending from the second hopper 13 to the spraying device 7.

[0149] A spraying device 7 is provided for receiving dry powder 4 from a conveying device 8 and spraying the dry powder 4 toward the inlet face of the filter 2. The spraying device 7 may include a secondary airflow generator for generating a secondary airflow that can be used to spray the dry powder 4 toward the inlet face of the filter 2.

[0150] The spray device 7 may further include one or more outlets for discharging the dry powder 4 toward the inlet face of the filter 2. The one or more outlets of the spray device may include orifices ranging from 0.5 mm to 10 mm in size. The orifices may be circular, partially circular, or slotted. The one or more outlets may be one or more fixed outlets. Alternatively, the one or more outlets may be one or more movable outlets, such as one or more oscillating outlets.

[0151] The one or more outlets can be disposed in one or more nozzles. Each of the one or more nozzles may include one or more spray outlets. In the illustrative example of Figure 1, a single nozzle 25 including multiple spray orifices is provided.

[0152] The secondary airflow generator may include a compressed gas generator. In the illustrative example of Figure 1, the secondary airflow generator includes a compressed air generator, which may include a compressor 22. The compressor 22 may receive air from an air inlet 21 and supply compressed air to one or more outlets of the spray device 7 via a feed line 23. A return line 24 may be provided. Valves and controls required for operation may be provided, as will be known to those skilled in the art.

[0153] An interconnection may be provided between the conveying device 8 and the spraying device 7, at which the dry powder 4 is transferred from the conveying device 8 to the spraying device 7. The interconnection may be located at or near one or more outlets of the spraying device 7. In one example, the interconnection may be provided in the nozzle 25. Alternatively, the interconnection may be located at or near the reservoir 3, for example, at or near the second hopper 13 of the reservoir 3. In one example, the interconnection is a fluid connection between the feed line 23 and the second conduit 16. For example, the secondary airflow of the spraying device 7 may be fluidly connected to the second conduit 16 at or near the outlet of the second hopper 13 to fluidize the dry powder 4, thereby aiding in the delivery of the dry powder 4 along at least a portion of the second conduit 16. In another example, the dry powder 4 may be fed along the second conduit 16 by gravity. The dry powder 4 may be aided in flowing downward along the second conduit 16 by suction that draws the dry powder 4 toward the outlet of the second conduit 16. For example, the spray nozzle 25 may generate suction to aid in drawing the dry powder 4 along the second conduit 16 and through the spray nozzle 25. For example, the nozzle 25 may utilize a secondary airflow from the feed line 23 to generate suction in the powder flow conduit of the nozzle 25 via a venturi device or similar equipment.

[0154] In one example, the spray device 7 includes a compressed air gun. A non-limiting example of a suitable compressed air gun is the STAR Professional Gravity Feed Spray Gun 1.4mm, part number STA2591100C.

[0155] The filter retainer 5 can be used to hold the filter 2 in a stationary position during processing. The filter retainer 5 can grip the upper and / or lower ends of the filter 2. The filter retainer 5 may include an expandable upper sealing bladder 31 (also referred to as an upper expandable collar) and / or an expandable lower sealing bladder 30 (also referred to as a lower expandable collar), which support the respective upper and lower ends of the filter 2. The expandable upper sealing bladder 31 and the expandable lower sealing bladder 30 may contact and / or engage with the outer surface of the filter 2. They may each form a liquid-impermeable or air-impermeable seal around the filter 2. The expandable upper sealing bladder 31 and the expandable lower sealing bladder 30 may be supported by one or more housings (e.g., by the inner walls of one or more housings).

[0156] Device 1 can be configured such that filter 2 is positioned vertically within filter holder 5 with the filter inlet face at the top. At least a portion of spray device 7 can be vertically positioned above the inlet face. The spray direction of spray device 7 can be coaxial with the longitudinal axis of filter 2. The spray direction and the longitudinal axis of filter 2 can coincide.

[0157] The device 1 may further include a flow conduit 10 located between the spray device 7 and the inlet face of the filter 2. The flow conduit 10 may be used to constrain and guide the primary airflow toward the inlet face of the filter 2. The flow conduit 10 may be used to align the primary airflow such that when the primary airflow contacts the inlet face of the filter 2, the flow direction of the primary airflow is perpendicular to the inlet face.

[0158] The flow conduit 10 may be empty to provide an unobstructed flow path between the spray device 7 and the inlet face of the filter 2. Alternatively, the flow conduit 10 may include a flow conditioner inserted between the spray device 7 and the inlet face of the filter 2 to facilitate the dispersion of the dry powder 4. For example, the flow conditioner may include one or more of a static mixer, a mesh, a sieve, a baffle, and an orifice plate.

[0159] The flow conduit 10 may include a pipe. The flow conduit 10 may include a cross-sectional shape that matches the cross-sectional shape of the inlet face of the filter 2. The flow conduit 10 may include a size that matches the size of the inlet face of the filter 2.

[0160] The spray device 7 can extend into the flow conduit 10. One or more outlets of the spray device 7 can be located within the flow conduit 10. For example, the nozzle 25 can be located in the upper region of the flow conduit 10. The nozzle 25 can coincide with the longitudinal axis of the filter 2.

[0161] The inlet face of filter 2 may be located at a distance greater than 10 cm, optionally greater than 20 cm, from the spraying device, for example, from the nozzle 25 of spraying device 7. A particular benefit may be found when the inlet face of filter 2 is located at a distance greater than 75 cm, optionally greater than 100 cm, from the nozzle outlet of spray nozzle 25. Additionally or alternatively, the spraying device (e.g., the nozzle 25 of spraying device 7) may be located at a distance from the inlet face of filter 2, which is up to four times the diameter of the inlet face of filter 2.

[0162] A vacuum generator 6 is provided to establish a primary airflow through the porous structure of the filter 2 during use by applying reduced pressure to the outlet face of the filter 2. The vacuum generator 6 may include a vacuum cone 40 that defines a funnel engaging the outlet face of the filter 2. An expandable lower sealing bladder 30 may form a seal between the outlet face of the filter 2 and the vacuum cone 40. The vacuum generator 6 may include a vacuum pump 42 connected to the flow cone via a conduit 43. The vacuum pump 42 can be controlled to control the volumetric flow rate of the primary airflow.

[0163] The vacuum generator 6 may be equipped with a volumetric flow sensor. The volumetric flow sensor may be an orifice plate 44 combined with a pressure sensor 45 positioned along the conduit 43. The vacuum generator 6 may include a bypass conduit 46 extending to the inlet 47.

[0164] Device 1 may further include a pressure sensor 41 for monitoring the back pressure of filter 2. A single pressure sensor 41 may be used. The single pressure sensor 41 may be located in vacuum generator 6, preferably in the filter holder or other housing of vacuum generator, such as vacuum cone 40.

[0165] Controller 9 controls the operation of at least vacuum generator 6 and spray device 7. In Figure 1, for clarity, the operational connections between controller 9 and the rest of device 1 are omitted. However, those skilled in the art will understand that necessary connections can be provided in any suitable manner. Such connections can be wired or wireless.

[0166] The controller 9 can be configured to control the transfer of dry powder 4 from the reservoir 3 to the spraying device 7 via the conveying device 8, independently of controlling the primary airflow generated by the vacuum generator 6. For example, the controller 9 can control the operation of the dispensing device 15.

[0167] The controller 9 can be configured to control the spraying of dry powder 4 toward the inlet face of the filter 2 independently of controlling the primary airflow. As used in this specification, 'independent' refers to the ability of the controller 9 to control each variable of the spraying of dry powder 4 and the primary airflow independently of the state of other variables. For example, the controller 9 can establish the primary airflow even when dry powder 4 is not sprayed simultaneously. For example, the controller 9 can increase or decrease the spraying rate of dry powder 4 without changing the volumetric flow rate of the primary airflow. For example, the controller 9 can increase or decrease the volumetric flow rate of the primary airflow without changing the spraying rate of dry powder 4. For example, the controller 9 can control the operation of the spraying device 7 independently of controlling the operation of the vacuum pump 42.

[0168] The controller 9 can be configured to operate the vacuum generator 6 to establish a primary airflow before the dry powder 4 is transferred to the spray device 7 and sprayed toward the inlet face of the filter 2.

[0169] The controller 9 can be configured to control the secondary airflow generator, such as the compressor 22, independently of the vacuum generator 6. The controller 9 can be configured to operate the vacuum generator 6 to maintain the primary airflow as a continuous airflow through the porous structure, and to operate the secondary airflow generator (e.g., the compressor 22) only for a portion of the time period of the primary airflow.

[0170] The controller 9 can be configured to control the vacuum generator 6 independently of the control conveying device 8 and / or the spraying device 7 to control the speed or mass rate of the dry powder 4 sprayed toward the inlet face of the filter 2, thereby controlling the level of pressure reduction applied to the outlet face of the filter 2.

[0171] The controller 9 can be configured to stop the spraying of dry powder 4 toward the inlet face of the filter 2 when a desired value of the back pressure of the filter 2, for example, is reached, as detected by the pressure sensor 41.

[0172] Device 1 can be used to treat a filter with dry powder 4, the dry powder comprising or consisting of one or more refractory powders, optionally comprising one or more pyrolytic refractory powders and / or one or more aerogels. Additionally or alternatively, device 1 can be used to treat a filter with dry powder 4, the dry powder containing or consisting of a metal compound for forming a metal oxide through thermal decomposition. In an example, the metal compound may contain or consist of: metal hydroxides, metal phosphates, metal carbonates, metal sulfates, metal perchlorates, metal iodides, metal oxalates, metal acetates, metal chlorates, or mixtures thereof.

[0173] An example of a method for processing a filter according to the present disclosure will now be described with reference to FIG2, which shows a flowchart illustrating a method for manufacturing a filter 2 incorporated into the use of apparatus 1. The method will be described with reference only to a filter 2 provided with a catalytic coating.

[0174] In step S21, a catalytic slurry is prepared by methods known in the art.

[0175] In step S22, a support coating is prepared from the catalytic slurry using methods known in the art. The support coating may be, for example, a hydrocarbon trap, a three-way catalyst (TWC), a NOx absorbent, an oxidation catalyst, a selective catalytic reduction (SCR) catalyst, a NOx-lean catalyst, and any combination of two or more thereof.

[0176] In step S23, the carrier coating is dosed and applied to the bare filter 2 using methods known in the art. For example, the carrier coating may be applied to a first side (e.g., the top) of the filter 2, and the opposite second side (e.g., the bottom) of the filter 2 may be subjected to at least a partial vacuum to allow the carrier coating to move through the porous structure of the filter 2. The filter 2 may be coated with a single dose, wherein the carrier coating may be applied to the filter 2 in a single step, wherein the filter 2 is held in a single orientation. Alternatively, the filter 2 may be coated with two doses. For example, in the first dose, the filter 2 may be in a first orientation, wherein the first side is on top and the second side is on the bottom. The coating is applied to the first side and coats a portion of the length of the filter 2. The filter 2 may then be inverted such that the second side is on top. The coating may then be applied to the second side to coat the portion of the filter 2 not coated with the first dose. Advantageously, the dual-dose process allows different coatings to be applied to each end of the filter 2.

[0177] In step S24, filter 2 can be dried.

[0178] In step S25, the filter 2 can be calcined using methods known in the art.

[0179] In optional step S26, the back pressure of filter 2 before treatment can be measured.

[0180] In optional step S27, filter 2 can be placed in inventory awaiting processing. Subsequently, in step S28, filter 2 can be retrieved from inventory and processed. Alternatively, filter 2 can be processed immediately, i.e., proceeding directly to step S29.

[0181] In step S29, filter 2 is processed according to this disclosure, as will be described in further detail below with reference to FIG3.

[0182] In step S30, after processing, filter 2 can be calcined.

[0183] The filter can be calcined at a selected temperature to produce the thermal decomposition of dry powder 4.

[0184] The calcination temperature can be selected to be at least 150°C, optionally at least 250°C, or optionally at least 500°C.

[0185] In some embodiments, a calcination temperature not exceeding 550°C is preferred. However, in other embodiments, the calcination temperature can be selected to be greater than 550°C. The calcination temperature can be selected to be up to 900°C, optionally up to 1150°C.

[0186] In one example, the calcination temperature can be selected between 300°C and 500°C. In another example, the calcination temperature can be selected at approximately 520°C. In yet another example, the calcination temperature can be selected at approximately 580°C. In yet another example, the calcination temperature can be selected at approximately 900°C.

[0187] Calcination can be carried out for a period of 30 to 90 minutes, optionally 30 to 60 minutes. In one example, the period is about 35 minutes. In another example, the period is about 60 minutes. During calcination, the residence time is 1 to 15 minutes, preferably 5 to 10 minutes.

[0188] In optional step S31, the back pressure of the treated filter 2 can be measured.

[0189] In step S32, the finished filter 2 can be prepared for delivery to the customer.

[0190] Figure 3 shows a flowchart illustrating step S29 of Figure 2.

[0191] In step S29-1, the filter can be loaded into the filter holder 5. The filter 2 can be held in a stationary position during processing. The filter 2 can be gripped by the filter holder 5 at its upper and / or lower ends. The expandable upper sealing bladder 31 and the expandable lower sealing bladder 30 can expand to contact and / or engage with the outer surface of the filter 2. The filter 2 can be held in a vertical orientation with the filter inlet face at the top. The operation of the filter holder 5, such as the expansion of the expandable upper sealing bladder 31 and the expandable lower sealing bladder 30, can be controlled by the controller 9.

[0192] In step S29-2, the vacuum generator 6 can be activated by the controller 9 to establish a primary airflow through the filter 2. Preferably, the primary airflow is established before the dry powder 4 is transferred to the spray device 7 and sprayed toward the inlet face of the filter 2. The level of pressure reduction generated by the vacuum generator 6 can be controlled by the controller 9 independently of the speed or mass rate at which the dry powder 4 is transferred from the reservoir 3 to the spray device 7. The primary airflow can have a flow rate of 10 m. 3 / hr to 5,000m 3 / hr, preferably 400m 3 / hr to 2,000m 3 / hr, preferably 600m 3 / hr to 1000m 3 / hr volumetric flow rate.

[0193] In step S29-3, the back pressure of filter 2 can be measured before the primary airflow is established but before the secondary airflow is established. The back pressure can be measured in this step until it has stabilized.

[0194] When the first derivative of the primary airflow velocity is ≤ ±Xm 3 hr -1 .s -1 When X = 0 to 0.30, optionally X = 0.10 to 0.20, or X = 0.15, the back pressure of filter 2 can be considered stable. Additionally or alternatively, when the first derivative of the filter's back pressure is ≤ ±Y mbar.s -1 When the back pressure of filter 2 is stable, Y can be considered to be from 0.5 to 3.0, optionally Y = 1.0 to 2.0, optionally Y = 1.5. Additionally or alternatively, when the primary airflow velocity is within Z% of the predetermined velocity, the back pressure of filter 2 can be considered to be stable, wherein Z = 1.5, optionally Z = 1.0, optionally Z = 0.5.

[0195] Back pressure can be measured using pressure sensor 41. The back pressure measurement in steps S29-3 can supplement or replace the back pressure measurement in step S26. Alternatively, the back pressure measurement in step S26 can replace the back pressure measurement in step S29-3. The back pressure measurement in step S26 and / or the back pressure measurement in step S29-3 can be used by controller 9 as a measure of the first back pressure of filter 2 before processing.

[0196] In step S29-4, the dry powder 4 is sprayed onto the inlet face of the filter 2 by the spraying device 7. During the spraying of the dry powder 4, the dry powder 4 can be supplied to the spraying device 7 by the conveying device 8.

[0197] The spray of dry powder 4 toward the inlet face of filter 2 is preferably controllable by controller 9 independently of establishing and controlling the primary airflow.

[0198] During steps S29-4, a secondary airflow, separated from the primary airflow and provided by, for example, compressor 22, can be used to transfer dry powder 4 from reservoir 3 to spray device 7. Preferably, the secondary airflow is controllable by controller 9 independently of the primary airflow. For example, controller 9 can control the operation of compressor 22 and / or valves and / or nozzles 25 of spray device 7 independently of the operation of vacuum pump 42. Dry powder 4 can be sprayed toward the inlet face of filter 2 using the secondary airflow. The secondary airflow may include a compressed gas flow, preferably an air flow.

[0199] During step S29-4, the primary airflow is preferably maintained as a continuous flow. During step S29-4, the secondary airflow can be applied as a single burst or multiple intermittent bursts.

[0200] In step S29-5, the back pressure of filter 2 is monitored while the dry powder 4 is being sprayed. The back pressure can be monitored using a pressure sensor 41. Controller 9 can be configured to stop the spraying of dry powder 4 toward the inlet face of filter 2 when the back pressure of filter 2 reaches a desired value. If the desired back pressure value has not yet been reached, controller 9 is configured to return to step S29-4 and continue spraying dry powder 4. This feedback can be continuous and does not necessarily involve any pause in the spraying of dry powder 4; that is, controller 9 can continuously monitor the back pressure of filter 2 while the spraying of dry powder 4 is in progress. The back pressure of filter 2 can be continuously monitored at least during step S29-5. This can be achieved by using ≥1 sample.s -1 Optional ≥5 samples. -1，任选 ≥10 samples.s -1 The sampling rate is used to measure back pressure to continuously monitor it. Pressure sensor 41 can incorporate a degree of damping to reduce or eliminate the influence of transient readings that may be associated with noise.

[0201] In step S29-6, the spraying of dry powder 4 is stopped. This can be achieved, for example, by the controller 9 stopping the transfer of dry powder via the conveyor 8 and / or by stopping the secondary airflow of the spraying device 7. After the spraying of dry powder 4 is stopped in step S29-6, the primary airflow can be maintained through the porous structure of the filter 2 for a certain period of time. The controller 9 can be configured to operate the vacuum generator 6 for a certain period of time after the spraying of dry powder 4 is stopped. For example, the primary airflow can be maintained until the back pressure measured in this step has stabilized.

[0202] As above, when the first derivative of the primary airflow velocity is ≤ ±Xm 3 hr -1 .s -1 When X = 0 to 0.30, optionally X = 0.10 to 0.20, or X = 0.15, the back pressure of filter 2 can be considered stable. Additionally or alternatively, when the first derivative of the filter's back pressure is ≤ ±Y mbar.s -1 When the back pressure of filter 2 is stable, Y can be considered to be from 0.5 to 3.0, optionally Y = 1.0 to 2.0, optionally Y = 1.5. Additionally or alternatively, when the primary airflow velocity is within Z% of the predetermined velocity, the back pressure of filter 2 can be considered to be stable, wherein Z = 1.5, optionally Z = 1.0, optionally Z = 0.5.

[0203] Optionally, in steps S29-6, the amount of dry powder 4 delivered toward the inlet face of the filter 2 can be measured. The controller 9 is configured to determine the amount of dry powder 4 delivered based on the signal output of the dispensing device 15, for example, based on the output from the loss-in-weight feeder.

[0204] The method can be configured to deliver a maximum load of dry powder 4 to a filter of 10 g / l to 40 g / l, optionally 15 g / l to 30 g / l, optionally about 20 g / l; or to deliver a maximum load of dry powder 4 to a filter of 10 g / l, optionally 5 g / l, optionally 2 g / l.

[0205] In steps S29-7, the primary airflow through filter 2 is stopped. This can be achieved by the controller 9 stopping the vacuum generator 6, i.e., stopping the vacuum pump 42. Alternatively, this can be achieved by the controller operating a valve on the vacuum generator 6 to redirect the suction through the bypass duct 46 to suction air through the inlet 47. This avoids the need to stop the vacuum pump 42 between consecutive processes of filter 2, which could result in a faster cycle time.

[0206] In steps S29-8, the filter 2 is unloaded from the filter holder 5 by, for example, contracting the expandable upper sealing bladder 31 and the expandable lower sealing bladder 30. The filter 2 can then be removed and the process proceeds to step S30 as described above.

[0207] Returning to steps 29-5, the event that triggers the stopping of the spray of dry powder 4 will be discussed in more detail.

[0208] When treating filter 2, the applicant has found that the final back pressure of the filter cannot be simply controlled by controlling the mass loading of the dry powder 4 applied to filter 2. For example, Figure 4 shows the treatment of two filters A and B, which had similar initial back pressures (36 mbar and 38 mbar) before coating. After treatment with dry powder 4, the two filters had similar back pressures of 64 mbar and 67 mbar, respectively. However, the mass loading of the filters was very different. Filter A was treated with 2.8 g of dry powder for 7 s. Filter B was treated with 8 g of dry powder for 20 s. The difference in the mass loading of dry powder required to achieve similar back pressure is thought to be due to differences in the substrate properties of the filters, including but not limited to the pore size and location of any applied carrier coating.

[0209] Therefore, it may be advantageous to monitor the back pressure of the filter 2 during the spraying of the dry powder 4 in step S29-5, and as described above, when the back pressure of the filter 2 reaches the desired value, the controller 9 stops the spraying of the dry powder 4 toward the inlet surface of the filter 2.

[0210] In some examples, when the spraying of dry powder 4 stops, the desired value of the back pressure of filter 2 can be the predetermined target back pressure p of filter 2. 目标 Predetermined back pressure p 目标 This can be the desired final back pressure of filter 2, as measured by device 1 (i.e., the coating device). The predetermined back pressure p 目标 This can be absolute back pressure. For example, at 600m... 3 At a flow rate of / hr, the absolute back pressure can range from 20mbar to 180mbar.

[0211] The applicant has discovered that if the required value is selected as the predetermined back pressure p 目标 If so, the final back pressure of filter 2 may exceed the target. For example, as shown in the example in Figure 5, the target p with a predetermined back pressure... 目标 (63 mbar) Processing filter. Dry powder spraying begins at approximately 17 seconds, at which point the filter back pressure has stabilized, and stops at approximately 29 seconds, at which point the filter back pressure p... BP The target of 63 mbar was achieved. However, the back pressure of the filter continued to increase (i.e., overshoot) and eventually stabilized at about 70 mbar.

[0212] Therefore, the applicant has discovered that an improved treatment method can be achieved by monitoring the back pressure of filter 2 in step S29-5 and stopping the spraying of dry powder 4 toward the inlet face of filter 2 when the following conditions are met:

[0213] p BP ≥p target - p offset

[0214] in,

[0215] p BP The back pressure of filter 2;

[0216] p 目标 The predetermined target back pressure for filter 2; and

[0217] p 偏移 For the pre-selected offset pressure.

[0218] For example, Figure 6 illustrates the modified processing procedure, where, as above, the target p of the predetermined back pressure... 目 The pressure is set to 63 mbar. An offset pressure p offset of 3 mbar is selected. Dry powder spraying begins at approximately 14 seconds, at which point the filter back pressure has stabilized, and stops at approximately 37 seconds, at which point the filter back pressure PBP reaches 60 mbar (i.e., from 63 mbar to 3 mbar). After the dry powder spraying stops, the filter back pressure continues to increase and eventually stabilizes at approximately 63 mbar (i.e., the desired final back pressure).

[0219] The predetermined target back pressure p of the filter 目标 This can be the absolute back pressure of filter 2. For example, the predetermined target back pressure p of filter 2. 目标 The target back pressure can range from 20 mbar to 180 mbar. Alternatively, the predetermined target back pressure p of filter 2... 目标 This can be the relative back pressure of filter 2. For example, the predetermined target back pressure p of filter 2. 目标 This can be the back pressure related to the initial back pressure of filter 2 before the dry powder 4 is sprayed. For example, the predetermined target back pressure p of filter 2. 目标 It can be 105% to 200% of the initial back pressure of filter 2, optionally 125% to 150%.

[0220] When p BP ≥p 目标 -p 偏移 For the minimum time interval t min When true, the spraying of dry powder 4 towards the inlet face of filter 2 can be stopped. The minimum time period can be t. min ≥0.1s, optionally ≥0.5s, optionally ≥1.0s.

[0221] p 偏移 It can be, for example, 1 mbar to 10 mbar, optionally 2 mbar to 5 mbar, optionally 3 mbar to 5 mbar. For example, this p 偏移 Can be used in p 目标For cases ranging from 20 mbar to 180 mbar.

[0222] The predetermined target back pressure p of the filter 目标 The following steps can be used to calculate:

[0223] - Select the desired back pressure for the filter, as will be measured by a test device different from coating device 1;

[0224] - Establish a calibration map to convert the back pressure measured on the test equipment to the back pressure measured on coating equipment 1; and

[0225] - Use a calibration chart to convert the desired back pressure to establish the predetermined target back pressure p 目标 .

[0226] For example, Figure 7 shows a first example of a calibration graph for converting between the back pressure on coating device 1 (shown on the x-axis and named 'Inline CFBP') and the back pressure on the test device (in this case, a Superflow Flow Bench 1050, available from Superflow Corporation, Sussex, Wisconsin, USA). The back pressure on both coating device 1 and the test device is 600 m. 3 The cold flow back pressure (CFBP) was measured in mbar at a flow rate of / hr. It can be seen that, in this case, a linear relationship can be established between the back pressures on the two devices when measured at the same flow rate. In this example, for the range of CFBP of interest, this application has found that calibration plots in the form of linear or quadratic fits accurately allow for the conversion of CFBP between coating device 1 and the test device. In the example of Figure 7, the flow rate for measuring CFBP on both coating device 1 and the test device was 600 M. 3 / hr.

[0227] Furthermore, the applicant has discovered that, provided the same selected flow rate is used on both the coating apparatus 1 and the test apparatus, a single linear or quadratic fit can accurately allow the conversion of CFBPs on both the coating apparatus 1 and the test apparatus, regardless of the selected flow rate or the diameter, length, or substrate characteristics of the filter 2. For example, Figure 8 shows a calibration plot in the form of a single linear or quadratic fit that accurately allows the conversion of CFBPs for two different filters (labeled as Part 1 and Part 2 in Figure 8). Moreover, when both Part 1 and Part 2 are at 600 M… 3 When testing the flow rate at / hr, and when both are at 800M 3 The same linear or quadratic fitting applies when performing / hr tests.

[0228] It may be desirable to switch between CFBPs on coating device 1 and test device, with different flow rates used on each device. The applicant has discovered that this can be achieved using a calibration plot containing a set of linear or quadratic fitted lines. For example, Figure 9 shows a calibration plot with two fitted lines. The leftmost fitted line represents the switching of CFBPs between two different filters (part 1 and part 2), where the flow rate on both coating device 1 and test device is 600 M. 3 / hr. The rightmost fitted line represents the CFBP conversion for the same part 1 and part 2, where the flow rate on coating device 1 is 800M. 3 / hr, and the flow rate on the test device is 600M. 3 / hr. It should be understood that the calibration plot may contain any desired number of fitted lines for any desired combination of coating and testing of CFBP.

[0229] As mentioned above, using offset pressure p 偏移 Improved and acceptable results can be achieved for the final back pressure of filter 2. However, the applicant has found that further improvements can be made. For example, the applicant has found that the characteristics of filter 2 can affect the loading of dry powder, and specifically, the loading rate of dry powder 4 relative to time can be affected by characteristics including the pore size, porosity, wall thickness, and / or pore density of filter 2. Therefore, as described above, using a fixed offset pressure p 偏移 This can still lead to some variation in the final back pressure obtained. This is illustrated in Figure 10, which shows the powder loading stages of eight filters 2 with different pore sizes. It can be seen that the gradients of the back pressure-time response curves differ between the different filters. Therefore, using a fixed offset pressure will not yield a uniform final back pressure for all eight filters 2. For the eight exemplary filters in Figure 10, the final obtained back pressure has an average back pressure of 64.5 mbar (compared to the target of 63 mbar) and a standard deviation of 1.2 mbar.

[0230] For example, Figure 11 illustrates this using filters 4 and 6 from Figure 10. In both cases, spraying of dry powder 4 is stopped when the filter reaches 60 mbar (the target back pressure of 63 mbar minus the offset pressure of 3 mbar). The response curve of filter 6 has a relatively shallow gradient (i.e., a relatively large amount of powder is required for every 1 mbar increase in back pressure), and the final back pressure obtained is very close to the target of 63.1 mbar. However, the response curve of filter 4 has a steeper gradient (i.e., a relatively small amount of powder is required for every 1 mbar increase in back pressure), and the final back pressure obtained exceeds the target and reaches 66.6 mbar.

[0231] Therefore, the applicant has discovered that an improved processing method can be achieved by monitoring the back pressure of the filter 2 during the spraying of the dry powder 4 in step S29-5 and stopping the spraying of the dry powder toward the inlet face of the filter 2 when the following conditions are met:

[0232] p est ≥p target

[0233] in,

[0234] p 目标 The predetermined target back pressure for the filter; and

[0235] p 估计 The estimated final back pressure for the filter;

[0236] p is calculated by extrapolating the back pressure data of the filter obtained during spray drying 4. 估计 .

[0237] The measured back pressure data can be extrapolated forward by T over time. s The estimated final back pressure p of the filter is calculated in seconds. 估计 T s Settlement time.

[0238] This method can be performed on coating equipment 1, and the settling time T s This can be a variable related to the coating equipment and can preferably be independent of filter 2. Settling time T s The parameters can be selected to characterize the performance of coating equipment 1. Settling time T s Theoretical calculations can be performed for coating equipment 1. Alternatively, the settling time T of coating equipment 1 can be determined experimentally by testing sample filters. s For example, experiments can be conducted iteratively to obtain a good estimate of settling time.

[0239] The estimated final back pressure p of filter 2 can be calculated by curve fitting the measured back pressure data and extrapolating the fitted curve forward in time. 估计 For example, during the initial loading of filter 2 with dry powder 4, back pressure measurements can preferably be performed at a high sampling rate. Processor 9 (or other computing resource) can then calculate a fitted line that matches the recorded back pressure data, and then use this fitted line to extrapolate forward in time. In some examples, the fitted line may be a quadratic fitted line that fits all or most of the recorded back pressure measurements. In other examples, the fitted line may be a linear fitted line that matches the current or most recent portion of the recorded back pressure measurements.

[0240] Figure 12 illustrates the application of this method to filter #4 mentioned in Figure 11. The settling time T is calculated based on the results from the eight filters shown in Figure 10.s For the coating equipment 1 used, the settling time is 3.5 seconds.

[0241] In Figure 12, 4.1 refers to filter #4 treated with a fixed offset pressure, as described above with reference to Figure 11. As stated above, powder spraying is stopped when the filter reaches a back pressure of 60 mbar (the target back pressure of 63 mbar minus the offset pressure of 3 mbar) and the final obtained back pressure exceeds the target and reaches 66.6 mbar.

[0242] The result labeled 4.2 shows the time extrapolation of the measured back pressure data by T using an improved method. s The effect is measured in seconds (i.e., 3.5 seconds in this example). It can be seen that the final back pressure obtained is 62.8 mbar, very close to the target of 63 mbar. For the eight exemplary filters in Figure 10, the improved method achieves a final back pressure with an average of 63.7 mbar (compared to the target of 63 mbar) and a standard deviation of 0.85 mbar, representing a significant improvement over the method using a fixed offset pressure.

[0243] According to this disclosure, a treated filter with one or more advantages can be provided compared to prior art filters. Preferably, but not exclusively, the treated filter can be processed according to the method of this disclosure and / or processed using the apparatus according to this disclosure.

[0244] Other aspects and implementations of this disclosure are set forth in the following provisions:

[0245] Clause A1. A method for treating a filter that filters particulate matter from exhaust gas, the method comprising the steps of:

[0246] a) The dry powder is contained in the storage container;

[0247] b) Positioning a filter in a filter holder, the filter comprising a porous substrate having an inlet face and an outlet face separated by a porous structure;

[0248] c) A primary airflow through the porous structure of the filter is established by applying a pressure reduction to the outlet surface of the filter;

[0249] d) Transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter;

[0250] e) Using the spraying device, spray the dry powder toward the inlet face of the filter, such that the dry powder is entrained in the primary airflow and passes through the inlet face of the filter to contact the porous structure; and

[0251] f) Monitor the back pressure of the filter during at least step e), and stop the spraying of the dry powder toward the inlet face of the filter when:

[0252] p BP ≥p target - p offset

[0253] in,

[0254] p BP This is the back pressure of the filter;

[0255] p 目标 The predetermined target back pressure for the filter; and

[0256] p 偏移 For the pre-selected offset pressure.

[0257] Clause A2. The method according to Clause A1, wherein in step f), when p BP ≥p 目标 -p 偏移 For the minimum time interval t min When true, the spraying of the dry powder toward the inlet face of the filter is stopped, where t min ≥0.1s, optionally ≥0.5s, optionally ≥1.0s.

[0258] Clause A3. The method described in accordance with Clause A1 or Clause A2, wherein p 偏移 The range is from 1 mbar to 10 mbar, optionally from 2 mbar to 5 mbar, and optionally from 3 mbar to 5 mbar.

[0259] Clause A4. The method according to any of the preceding clauses, wherein in step f), the back pressure of the filter is continuously monitored during at least step e); and optionally, wherein the back pressure is monitored by means of ≥1 sample.s -1 Optional ≥5 samples. -1 Optional ≥10 samples. -1 The sampling rate is used to measure the back pressure to continuously monitor it.

[0260] Clause A5. The method according to any of the preceding clauses, the method further comprising, in step c), monitoring the back pressure of the filter and passing the primary airflow through the porous structure of the filter until the back pressure of the filter stabilizes, before starting step d).

[0261] Clause A6. The method according to Clause A5, wherein the predetermined target back pressure p of the filter 目标 This is related to the stable back pressure monitored in step c).

[0262] Clause A7. The method described according to any of the preceding clauses further includes the following steps:

[0263] g) Monitor the back pressure of the filter and, after the spraying of the dry powder has stopped, maintain the primary airflow through the porous structure of the filter until the back pressure of the filter stabilizes.

[0264] Clause A8. The method according to any one of Clauses A5 to A7, wherein the back pressure of the filter is considered stable when:

[0265] i) The primary airflow velocity is within 0.5% of the predetermined velocity;

[0266] ii) The first derivative of the primary airflow velocity is ≤ ±0.15m. 3 hr -1 .s -1 ;as well as

[0267] iii) The first derivative of the back pressure of this filter is ≤ ±1.5 mbar.s -1 .

[0268] Clause A9. The method according to any of the preceding clauses, wherein the back pressure p BP This is the absolute back pressure measured relative to atmospheric pressure.

[0269] Clause A10. The method according to any of the preceding clauses, wherein the method uses a coating device to perform at least steps a) to f), wherein the predetermined target back pressure p of the filter 目标 The calculation is performed using the following steps:

[0270] - Select the desired back pressure for the filter, as will be measured by testing equipment different from the coating equipment;

[0271] - Establish a calibration map to convert the back pressure measured on the test equipment to the back pressure measured on the coating equipment; and

[0272] - Use the calibration chart to convert the desired back pressure to establish the predetermined target back pressure p 目标 .

[0273] Clause B1. A method for treating a filter that filters particulate matter from exhaust gas, the method comprising the steps of:

[0274] a) The dry powder is contained in the storage container;

[0275] b) Positioning a filter in a filter holder, the filter comprising a porous substrate having an inlet face and an outlet face separated by a porous structure;

[0276] c) A primary airflow through the porous structure of the filter is established by applying a pressure reduction to the outlet face of the filter while monitoring the back pressure of the filter, and the primary airflow is passed through the porous structure of the filter until the back pressure of the filter stabilizes.

[0277] d) After establishing the stable back pressure of the filter, the dry powder is transferred from the reservoir to a spray device located upstream of the inlet face of the filter;

[0278] e) Using the spraying device, spray the dry powder toward the inlet face of the filter, so that the dry powder is entrained in the primary airflow and passes through the inlet face of the filter to contact the porous structure, while monitoring the back pressure of the filter.

[0279] f) Stop the spraying of the dry powder toward the inlet face of the filter; and

[0280] g) Continue to monitor the back pressure of the filter, and after the spraying of the dry powder has stopped, maintain the primary airflow through the porous structure of the filter until the back pressure of the filter stabilizes.

[0281] Clause B2. The method according to Clause B1, wherein the first derivative of the primary airflow velocity is ≤ ±Xm 3 hr -1 .s -1 When X = 0 to 0.30, or optionally X = 0.10 to 0.20 or X = 0.15, the back pressure of the filter can be considered stable.

[0282] Clause B3. The method described in Clause B1 or Clause B2, wherein the first derivative of the back pressure of the filter is ≤ ±Y mbar. -1 When the back pressure of the filter is considered to be stable, Y = 0.5 to 3.0, optionally Y = 1.0 to 2.0, optionally Y = 1.5.

[0283] Clause B4. The method according to any one of Clauses B1 to B3, wherein the back pressure of the filter is considered stable when the primary airflow velocity is within Z% of a predetermined velocity, wherein Z = 1.5, optionally Z = 1.0, optionally Z = 0.5.

[0284] Clause B5. The method according to any one of Clauses B1 to B4, wherein the back pressure is an absolute back pressure measured relative to atmospheric pressure.

[0285] Clause C1. The method according to any one of Clauses A1 to A10 or B1 to B5, wherein the back pressure of the filter is measured using: a pressure sensor; optionally a single pressure sensor located in a filter retainer or another housing fluidly connected to the outlet face of the filter.

[0286] Clause D1. A method for treating a filter that filters particulate matter from exhaust gas, the method comprising the steps of:

[0287] a) The dry powder is contained in the storage container;

[0288] b) Positioning a filter in a filter holder, the filter comprising a porous substrate having an inlet face and an outlet face separated by a porous structure;

[0289] c) A primary airflow through the porous structure of the filter is established by applying a pressure reduction to the outlet surface of the filter;

[0290] d) Transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter;

[0291] e) Using the spraying device, spray the dry powder toward the inlet face of the filter, such that the dry powder is entrained in the primary airflow and passes through the inlet face of the filter to contact the porous structure; and

[0292] f) Monitor the back pressure of the filter during at least step e), and stop the spraying of the dry powder toward the inlet face of the filter when:

[0293] p 估计 ≥p 目标

[0294] in,

[0295] p 目标 The predetermined target back pressure for this filter; and

[0296] p 估计 This is the estimated final back pressure for the filter;

[0297] p is calculated by extrapolating the measured back pressure data of the filter obtained during step f). 估计 .

[0298] Clause D2. The method according to Clause D1, wherein the measured back pressure data is extrapolated forward in time by T s Calculate p in seconds 估计 T s Settlement time.

[0299] Clause D3. The method according to Clause D2, wherein the method is performed on a coating device, and the settling time T s These are variables related to the coating equipment and are preferably independent of the filter.

[0300] Clause D4. The method according to any one of Clauses D1 to D3, wherein p is calculated by curve fitting the measured back pressure data and extrapolating the fitted curve forward in time. 估计 .

[0301] Clause E1. The method according to any one of Clauses A1 to A10, B1 to B5, C1 to C2, or D1 to D4, wherein the dry powder comprises or consists of the following:

[0302] a) Metal compounds used to form metal oxides through thermal decomposition;

[0303] b) Metal oxides; or

[0304] c) Aerogel.

[0305] Clause E2. The method according to Clause E1, wherein the metal compound comprises or consists of the following: metal hydroxide, metal phosphate, metal carbonate, metal sulfate, metal perchlorate, metal iodide, metal oxalate, metal acetate, metal chlorate, or mixtures thereof.

[0306] Clause E3. The method according to Clause E1 or E2, wherein the metal of the metal compound comprises or is composed of one or more of the following: magnesium, calcium, strontium, barium, aluminum, zirconium, manganese, lithium, iron, cobalt, nickel, copper or gallium.

[0307] Clause E4. The method according to any one of Clauses E1 to E3, wherein the metal oxide of option c) comprises one or more pyrolytic metal oxides or pyrolytic mixed oxides, such as pyrolytic alumina, pyrolytic silicon dioxide or pyrolytic titanium dioxide.

[0308] Clause E5. The method according to any one of Clauses E1 to E4, wherein the aerogel comprises one or more of silica aerogel, alumina aerogel, carbon aerogel, titanium dioxide aerogel, zirconium oxide aerogel, cerium dioxide aerogel, metal oxide aerogel and mixed oxide aerogel.

[0309] Clause E6. The method according to any one of clauses E1 to E5, wherein the dry powder has a concentration of 1 g / cm³. 3 Up to 3g / cm 3 Optional 1.5g / cm 3 Up to 2.5g / cm3 Approximately 2g / cm³ (optional) 3 The tap density; or the dry powder has a tap density of less than 0.10 g / cm³. 3 Optionally less than 0.08 g / cm³ 3 Optionally less than 0.07 g / cm³ 3 Optionally less than 0.06 g / cm³ 3 Optionally less than 0.05 g / cm³ 3 The tap density.

[0310] Clause E7. The method according to any one of Clauses E1 to E6, wherein the dry powder has a d50 (by volume) of less than 10 micrometers, optionally less than 5 micrometers, optionally about 2 micrometers.

[0311] Clause E8. The method according to any one of Clauses E1 to E7, the method comprising providing a maximum load of the filter of the dry powder at 10 g / l to 40 g / l, optionally 15 g / l to 30 g / l, optionally about 20 g / l; or providing a maximum load of the filter of the dry powder at <10 g / l, optionally <5 g / l, optionally <2 g / l.

[0312] Clause E9. The method according to any one of Clauses E1 to E8, further comprising coating the filter with a carrier coating, preferably a catalyst carrier coating, prior to step b).

[0313] Clause F1. The method according to any of the preceding clauses further includes the step of calcining the filter after loading it with the dry powder.

[0314] Clause F2. The method according to Clause F1, wherein the calcination is carried out at a temperature of at least 150°C, optionally at least 250°C, optionally at least 500°C.

[0315] Clause F3. The method according to Clause F1 or Clause F2, wherein the calcination is carried out at a temperature not exceeding 550°C; alternatively, at a temperature exceeding 550°C; optionally, at a temperature up to 900°C; optionally, at a temperature up to 1150°C.

[0316] Clause F4. The method according to any one of Clauses F1 to F3, wherein the calcination is carried out for a period of 30 to 90 minutes, optionally 30 to 60 minutes, and includes a dwell time of 1 to 15 minutes, preferably 5 to 10 minutes.

[0317] Clause G1. The method according to any of the preceding clauses, wherein in step d), the dry powder is transferred from the reservoir to the spray device using a secondary airflow separate from the primary airflow; and optionally, the secondary airflow is controllable independently of the primary airflow.

[0318] Clause G1. The method according to Clause G1, wherein the secondary airflow comprises a compressed gas flow, preferably an air flow.

[0319] Clause G2. The method described in accordance with Clause G1 or Clause G2, wherein the secondary gas flow is applied as a single burst or multiple intermittent bursts.

[0320] Clause G3. The method according to any of the preceding clauses, the method comprising using a vacuum generator to establish the primary airflow through the porous structure of the filter.

[0321] Clause G4. The method according to Clause G3, wherein the level of pressure reduction generated by the vacuum generator is controllable independently of the rate or mass rate at which the dry powder is transferred from the reservoir to the spray device.

[0322] Clause G5. The method according to any of the preceding clauses, wherein the primary airflow has a depth of 10m. 3 / hr to 5,000m 3 / hr, preferably 400m 3 / hr to 2,000m 3 / hr, preferably 600m 3 / hr to 1000m 3 / hr volumetric flow rate.

[0323] Clause G6. The method described in Clause G5, further comprising using a pressure sensor, preferably a single pressure sensor, to monitor the back pressure.

[0324] Clause G7. The method according to Clause G6, wherein the pressure sensor, preferably the single pressure sensor, is located in the filter retainer or in another housing that is fluidly connected to the outlet side of the filter.

[0325] Clause G8. The method according to Clause G6 or Clause G7, wherein the same pressure sensor, preferably the same single pressure sensor, is used to monitor the back pressure of the filter during at least steps c) and f).

[0326] Clause G9. The method according to any of the preceding clauses, wherein in step e), the dry powder is sprayed from one or more outlets of the spraying device.

[0327] Clause G10. The method according to Clause G9, wherein the one or more outlets of the spraying device include an orifice size of 1 mm to 10 mm, optionally 0.5 mm to 5.0 mm, optionally 1.0 mm to 2.5 mm, optionally 1.0 mm to 2.0 mm.

[0328] Clause G11. The method according to Clause G9 or Clause G10, wherein the dry powder is sprayed from one or more fixed outlets of the spraying device.

[0329] Clause G12. The method according to Clause G9 or Clause G10, wherein the dry powder is sprayed from one or more movable outlets of the spraying device, preferably from one or more oscillating outlets.

[0330] Clause G13. The method according to any of the preceding clauses, the method further comprising, in step e), guiding the dry powder from the spray device to the inlet face of the filter within the flow conduit.

[0331] Clause G14. The method according to Clause G13, wherein the flow conduit provides an unobstructed flow path between the spray device and the inlet face of the filter.

[0332] Clause G15. The method according to Clause G13, wherein the flow conduit includes a flow regulator inserted between the spray device and the inlet face of the filter, the flow regulator being used to promote the dispersion of the dry powder in the airflow.

[0333] Clause G16. The method according to Clause G15, wherein the flow regulator comprises one or more of a static mixer, a screen, a sieve, a baffle, and an orifice plate.

[0334] Clause G17. The method according to any of the preceding clauses, wherein the inlet surface of the filter is 10 cm to 80 cm, preferably 15 cm to 20 cm, from the spray device, and or the spray device is located at a distance from the inlet surface of the filter, the distance being up to 4 times the diameter of the inlet surface of the filter.

[0335] Clause G18. The method according to any of the preceding clauses, the method further comprising dispensing the dry powder from the storage tank in step d).

[0336] Clause G19. The method described in Clause G18, wherein the dispensing includes dispensing by one or more of weight, volume, number of particles, and time.

[0337] Clause G20. The method described in accordance with Clause G18 or Clause G19, the method comprising feeding the dry powder into the dosing device by weight.

[0338] Clause G21. The method according to any one of Clauses G18 to G20, wherein the feeding uses a loss-in-weight feeder.

[0339] Clause G22. The method according to any of the preceding clauses, wherein in step a), the dry powder is contained in one or more hoppers.

[0340] Clause G23. The method according to any of the preceding clauses, wherein in step b), the filter is positioned in the retainer with the inlet face at the uppermost vertical orientation.

[0341] Clause G24. The method according to Clause G23, wherein in step d), the spraying device is vertically positioned above the inlet surface; and preferably, the spraying direction of the spraying device is coaxial with the longitudinal axis of the filter; and preferably, the spraying direction and the longitudinal axis coincide.

[0342] Clause G25. The method according to any of the preceding clauses, wherein the porous substrate is a wall-flow filter.

[0343] Clause H1. A filter that can be obtained by means of the method described in accordance with any of the preceding clauses.

[0344] Clause H2. The filter described in Clause H1 is one or more of a catalytic soot filter (CSF), a selective catalytic reduction filter (SCRF), a lean NOx trap filter (LNTF), and a gasoline particulate filter (GPF).

Claims

1. A method for treating a filter that filters particulate matter from exhaust gas, the method comprising the following steps: a) Containing dry powder in a reservoir; b) Positioning a filter in a filter holder, the filter comprising a porous substrate having an inlet face and an outlet face separated by a porous structure; c) Establishing a primary airflow through the porous structure of the filter by applying a pressure reduction to the outlet face of the filter; d) Transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; e) Spraying the dry powder toward the inlet face of the filter using the spray device, such that the dry powder is entrained in the primary airflow and passes through the inlet face of the filter to contact the porous structure; and f) Monitoring the back pressure of the filter during at least step e), and stopping the spraying of the dry powder toward the inlet face of the filter when: p BP ≥p target - p offset where, p BP The back pressure of the filter; p 目标 The predetermined target back pressure of the filter; and p 偏移 For the pre-selected offset pressure.

2. The method according to claim 1, wherein in step f), when p BP≥ p 目标 -p 偏移 For the minimum time interval t min When true, the spraying of the dry powder toward the inlet face of the filter is stopped, wherein t min ≥0.1s.

3. The method according to claim 1, wherein p 偏移 The range is from 1 mbar to 10 mbar.

4. The method of claim 1, wherein in step f), the back pressure of the filter is continuously monitored during at least step e).

5. The method of claim 1, further comprising, in step c), monitoring the back pressure of the filter and allowing the primary airflow through the porous structure of the filter until the back pressure of the filter stabilizes, before starting step d).

6. The method of claim 5, wherein the predetermined target back pressure p of the filter 目标 This is related to the stable back pressure monitored in step c).

7. The method according to claim 1, further comprising the following steps: g) Monitor the back pressure of the filter, and after the spraying of the dry powder has stopped, maintain the primary airflow through the porous structure of the filter until the back pressure of the filter stabilizes.

8. The method of claim 5, wherein the back pressure of the filter is considered stable when: i) the primary airflow velocity is within 0.5% of a predetermined velocity; ii) the first derivative of the primary airflow velocity is ≤ ±0.15 m. 3 hr -1 .s -1 ; and iii) the first derivative of the back pressure of the filter is ≤ ±1.5 mbar.s -1 .

9. The method according to claim 1, wherein the back pressure p BP This is the absolute back pressure measured relative to atmospheric pressure.

10. The method of claim 1, wherein the method uses a coating apparatus to perform at least steps a) to f), wherein the predetermined target back pressure p of the filter 目标 The calculation is performed by: - ​​selecting a desired back pressure for the filter, such as that measured by a test device different from the coating device; - establishing a calibration chart to convert the back pressure measured on the test device to the back pressure measured on the coating device; and - using the calibration chart to convert the desired back pressure to establish the predetermined target back pressure p.

11. The method of claim 1, wherein the back pressure of the filter is measured using a pressure sensor located in a filter retainer or another housing fluidly connected to the outlet face of the filter.

12. The method of claim 1, further comprising the step of calcining the filter after loading it with the dry powder.

13. The method of claim 1, further comprising coating the filter with a carrier coating prior to step b).

14. The method of claim 1, wherein the method comprises providing a maximum load of the filter of the dry powder at a concentration of 10 g / L to 40 g / L.

15. The method of claim 1, wherein the method comprises providing a maximum load of the filter for delivering <10 g / L of the dry powder.

16. The method according to claim 1, wherein the dry powder has a content of 1 g / cm³. 3 Up to 3g / cm 3 The tap density.

17. The method according to claim 1, wherein the dry powder has a content of less than 0.10 g / cm³. 3 The tap density.

18. The method of claim 1, wherein the dry powder has a volumetric d50 of less than 10 micrometers.

19. The method of claim 1, wherein in step d), the dry powder is transferred from the reservoir to the spray device using a secondary airflow separate from the primary airflow.

20. The method of claim 19, wherein the secondary gas flow comprises a compressed gas flow.

21. The method of claim 1, wherein the dry powder comprises or is composed of a metal compound for forming a metal oxide by thermal decomposition.

22. A method for treating a filter that filters particulate matter from exhaust gas, the method comprising the steps of: a) Containing dry powder in a reservoir; b) Positioning a filter in a filter holder, the filter comprising a porous substrate having an inlet face and an outlet face separated by a porous structure; c) Establishing a primary airflow through the porous structure of the filter by applying a pressure reduction to the outlet face of the filter while monitoring the back pressure of the filter, and allowing the primary airflow through the porous structure of the filter until the back pressure of the filter stabilizes; d) After establishing a stable back pressure of the filter, transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; e) Spraying the dry powder toward the inlet face of the filter using the spray device, such that the dry powder is entrained in the primary airflow and passes through the inlet face of the filter to contact the porous structure, while monitoring the back pressure of the filter; f) Stop the spraying of the dry powder toward the inlet face of the filter; and g) continue to monitor the back pressure of the filter while maintaining the primary airflow through the porous structure of the filter until the back pressure of the filter stabilizes after the spraying of the dry powder has stopped.

23. The method according to claim 22, wherein the first derivative of the primary airflow velocity is ≤ ±Xm 3 hr - 1 .s -1 When X = 0 to 0.30, the back pressure of the filter is considered stable.

24. The method of claim 22, wherein the first derivative of the back pressure of the filter is ≤ ± Y mbar.s -1 When the back pressure of the filter is considered to be stable, Y = 0.5 to 3.

0.

25. The method of claim 22, wherein the back pressure of the filter is considered stable when the primary airflow velocity is within Z% of a predetermined velocity, wherein Z = 1.

5.

26. The method of claim 22, wherein the back pressure is an absolute back pressure measured relative to atmospheric pressure.

27. A method for treating a filter that filters particulate matter from exhaust gas, the method comprising the steps of: a) Containing dry powder in a reservoir; b) Positioning a filter in a filter holder, the filter comprising a porous substrate having an inlet face and an outlet face separated by a porous structure; c) Establishing a primary airflow through the porous structure of the filter by applying a pressure reduction to the outlet face of the filter; d) Transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; e) Spraying the dry powder toward the inlet face of the filter using the spray device, such that the dry powder is entrained in the primary airflow and passes through the inlet face of the filter to contact the porous structure; and f) Monitoring the back pressure of the filter during at least step e), and stopping the spraying of the dry powder toward the inlet face of the filter when: p_estimated ≥ p_target, where p 目标 The predetermined target back pressure of the filter; and p 估计 The estimated final back pressure of the filter; p is calculated by extrapolating the measured back pressure data of the filter obtained during step f). 估计 .

28. The method of claim 27, wherein the measured back pressure data is extrapolated forward in time by T. s Calculate p in seconds 估计 T s Settlement time.

29. The method of claim 28, wherein the method is performed on a coating apparatus, and the settling time T s These are variables related to the coating equipment.

30. The method of claim 27, wherein p is calculated by curve fitting the measured back pressure data and extrapolating the fitted curve forward in time. 估计 .

31. A filter that can be obtained by the method according to claim 1.

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