WO2023007310A1

WO2023007310A1 - A device for uniform drying of coated monolith using monotonous hot air distribution

Info

Publication number: WO2023007310A1
Application number: PCT/IB2022/056620
Authority: WO
Inventors: Alireza DEHGHAN BEIDOKHTI; Yousef ZEINALY; Seyed Pouya PISHBIN; Mojtaba GOL
Original assignee: Ayegh Khodro Toos Co
Priority date: 2021-07-28
Filing date: 2022-07-19
Publication date: 2023-02-02

Abstract

The present invention is "A device for uniform drying of coated monolith using monotonous hot air distribution". One of the main steps in the automotive exhaust gas catalyst production process is the monolith drying step after wash coating. The purpose is the controlled evaporation of the moisture of the coated slurry in order to stabilize the slurry on the monolith channel walls. A continuous dryer based on a hot air system is designed in which by proper and uniform direction of hot air to the interior of monolith channels, uniform drying speed and consequently uniform distribution of precious metals in the catalyst is maintained between different channels and the heat efficiency of the process is increased. Besides, the proposed device operates continuously and, unlike conventional equipment, will require only one operator for continuous operation. The design is modular and it is possible to easily change the type of loaded monolith.

Description

A device for uniform drying of coated monolith using monotonous hot air distribution

This invention belongs to the field of mechanics affiliated with the automotive industry

In invention No. 201720266723.5 dated March 17, 2017, the inventor has disclosed a coated honeycomb dryer that can intermittently dry coated monoliths. In this invention, special horizontal cavities are provided for placing the coated monoliths on both sides of the equipment. A blower is located in the center of the device and heating elements are installed on both sides.

The direction of rotation of the blower blades and, consequently, the direction of air movement between two sides of the device in which the parts are arranged inside the cavities, changes according to a predetermined program.

According to the inventor, the main advantage of this device is to improve the uniformity of the appearance of the parts after drying, which is achieved by changing the direction of airflow over the parts via changing the direction of rotation of the blower blades so to dry parts from both sides.

This device will operate in a batch-wise mode and due to the placement of the retaining plates under each piece, the uniformity of air flow between different channels of a covered monolith will not be met, depending on the position of the piece inside the wall cavities.

In Patent No. US 7,601,671 B2 dated October 13, 2009, the inventor disclosed a method for drying. In this method, the use of microwave dryers with a wavelength of 2.5 GHz is proposed. The inventor claims that by using microwave dryers, unlike conventional dryers in which the drying process starts from the surface channels, the drying process starts from the middle channels of the coated monolith. This will create a proper distribution of precious metals in the side and middle channels of the coated monolith. In addition, according to the inventor, the use of microwave dryers will reduce the drying time compared to conventional dryers to about 10 minutes. In this design, for continuous operation, the parts are placed on a movable conveyor that passes through the dryer cab, and again at least two operators are required, one at the inlet and one at the outlet of the device.

To evaluate the performance of the proposed design and compare it with the existing systems, a commercial model of exhaust gas catalyst was dried using the device disclosed in the present. The sample contains 35 gr/ft3 of total precious metals (three metals of platinum, palladium, and rhodium with a ratio of 14/5/1). The sampling operation is performed according to what is presented in the US Patent 7,601,671 B2 dated 10/13/2009, at five specific points of monolith cross-section, according to . Removing 1 inch from monolith inlet face, a cross-section with 0.5-inch thickness is extracted.

To examine the uniformity of precious metals distribution, the platinum content of 5 stipulated samples was measured using ICP (Inductively Coupled Plasma) VISTA-MPX device and was compared with data from Patent number US 7,601,671 B2 dated 10/13/2009 (Table 1). As can be seen from the results, the present invention provides a more uniform distribution of precious metals between different channels compared to conventional conveyor equipment as well as the microwave dryer.

Technical Problem

The exhaust gas catalyst consists of a monolith (mainly ceramic or metal) that is coated with a slurry containing the active phase of the catalyst. Given its important role in providing the required contact surface between the active phase and the pollutants emitted from the engine, monoliths mainly are in the form of honeycomb structures. The cell density of the monoliths can vary between 100 and 900 cells per square inch (CPSI). Given the sensitivity of the process and to avoid dripping of slurry coated on the walls of monolith channels and also to affix the precious metals to the oxide support, the slurry water content should be reduced to a certain extent immediately after washcoating. currently, the devices used in the coated honeycomb drying process are mainly conveyor dryer types, in which coated monoliths are placed over a moving conveyor, pass through a cabin exposed to a stream of hot air at elevated temperatures, and dry to the desired extent.

In this type of dryer, the vast portion of hot air, passes around the monolith, drying usually begins from the outer walls and the nearby channels, then gradually the heat is transferred to the middle channels.

Studies show that despite the uniform coating of precious metals on the raw monolith, this difference in drying time between the exterior and interior channels of the coated monolith will cause the precious metals of the slurry to migrate from the inner channels to the outer channels. Based on this, there is a build-up of precious metals in the exterior channels. this phenomenon may cause performance deterioration of the final catalytic converter. As compensation, the total amount of precious metals in a coated monolith is generally increased to recompense for the deficiency caused by active phase migration from inner channels. The present invention with a suitable and unique design minimizes the hot air circumventing around the monolith, and the difference between the drying times in different channels is minimized by uniformly directing the hot air flow to the channels. Due to the high price of precious metals used in the exhaust gas catalyst as the active phase, this will have a positive effect on reducing the consumption of precious metals, and consequently on the final price of the product. Furthermore, the new design can lead to considerable energy efficiency since it conducts hot air through the monolith channels rather than its surrounding environment.

The conveyor dryers currently in use take up a lot of space on the production line and require two operators for each dryer. One operator places the coated monolith at the inlet of the device and the other collects the dried parts at the outlet. In the present device, due to the rotating design concept and circular motion of the parts, one operator can simultaneously load and unload the wet and dried coated monolith. This design, in addition to saving operating costs, will facilitate the use of robots and full process automation in the future. Another point is that in the present invention, because of proper design, the occupied space will be much less than conventional devices.

Solution to Problem

The present invention is "A device for uniform drying of coated monolith using monotonous hot air distribution" which consists of the following components: a rotating plate for the placement of the parts (1), a set of frames, and a chassis of the device (2), hot air distribution channel (3), rotating plate guide set (4), dryer chamber (5), hot air production unit (6), cooling unit (7), electrical panel and control system (8), shaft and power generation and transmission system (9), cap holder compartment (10), inlet air filter (11), user panel (12) and a specific seat on the rotating plate that includes: guide rods (13), coated monolith (14), top plate (15) and bottom plate (16).

The main idea in the proposed device is based on two parts. The first is the proper conduction of hot air through the interior channels of the drying monolith, and the second is the uniform distribution of hot air between different channels of a monolith, so the drying rate of washcoat in all channels tends to be similar. To put these two concepts into practice, a continuously operating device has been constructed, the schematic of the various parts of which is presented in .

The hot air production unit (5) consists of a blower that conducts ambient air through an intake air filter (11) to the heating element chamber. The airflow rate can be adjusted by the control system (8). The electrical power of the elements is also determined by the control system (8) to reach the desired operating temperature. After heating, the air enters the hot air distribution channel (3). The hot air production unit (6), hot air distribution channel (3), and inlet air filter (11) are installed on the frame and chassis of the device (2) so that the hot air distribution channel (3) is located exactly below the rotating plate (1). The rotating plate (1) is connected to the shaft and the power generation and transmission system (9). The power generation and transmission system (9) consists of an electric motor and a gearbox that provides the necessary torque to rotate the rotating plate (1) and transmits the generated torque through the shaft to the rotating plate (1). The space around the top of the rotating plate is surrounded by a drying chamber (5).

The rotating plate (1) is shifted to a certain extent each time the button is pressed, and the idle time in each position can be altered by the control system (8). So, the residence time of the parts inside the dryer chamber (5) and as a result, the amount of evaporated water content can be adjusted. To maintain the uniform and smooth movement of the rotating plate (1), to prevent its deformation in the long term, and to properly direct the flow of hot air from the hot air distribution channel (3) to the dryer chamber (5), the guide set of the rotating plate (4) is installed below the rotating plate (1) and between the rotating plate (1) and the hot air distribution channel (3).

The guide set of the rotating plate (4) consists of a fixed center plate and a number of bearings mounted on the center plate which are installed close to the peripheral edges of the rotating plate (1) (so as not to disturb the transfer of hot air from the hot air distribution duct (3) to the rotating plate (1) and dryer chamber (5)). The bearings both have the task of smoothing the rotational motion of the rotating plate (1) and also bear part of the weight of the rotating plate (1) and prevent its deformation. The center plate is also installed in such a way that, in addition to maintaining the bearings, it ensures proper airflow in the location of coated monoliths (and the interior of the monolith channels (14)). Also, to prevent hot air from passing through the space between the rotating plates (1) and the guide set of the rotating plate (4), suitable seals are placed on the fixed center plate and near the peripheral edges of the rotating plate. The wet coated monoliths are placed by the operator on a rotating plate (1) and in the specific places. In fact, holes of fixed diameter are mounted on the rotating plate (1). The diameter of these holes is selected according to the dimensions of the largest piece to be dried by this device. Inside these holes are seats that are customized according to the type and dimensions of the exact product.

exhibits an example of specific monolith places from a close-up view. This figure exhibits the guide rods (13), the coated monolith of exhaust gas catalyst (14), the top plate (15), and the bottom plate (16). The outer diameter of the top plate (15) and the bottom plate (16) is selected so that the outer diameter of the top plate (15) is greater than the diameter of the fixed holes on the rotating plate (1) and the outer diameter of the bottom plate (16) is less than the diameter of the fixed holes on the rotating plate (1). Consequently, the seat is placed on the hole and the weight of the seat fixes it in place. The top plate (15) and the bottom plate (16) are connected by guide bars and are placed parallel to each other at a certain distance from each other. The distance between the top plate (15) and the bottom plate (16) is less than the thickness of the rotating plate (1).

In addition to connecting the top (15) and bottom (16) plate, the guide rods help to fix the monolith (14) during the drying process, and avoid tilting and falling due to airflow or rotating plate movement (1). There is a delicate clearance between the upper plate (15) and the lower plate (16) with the outer diameter of the desired monolith (14); for which the seat is customized; so, the monolith can be easily placed on the seat and removed. this clearance is of high practical importance in reducing the airflow through the space around the monolith (14) and also in conducting hot air flow through the monolith channels which will increase the efficiency of the drying process. To place the piece properly on the seat, small protrusions are provided on the bottom plate (16), to prevent the monolith from falling into the hot air distribution channel (3). Since these protrusions cover a part of the cross-sectional area of the monolith (14) and prevent the entry of hot air into some of its channels, the smaller the area of these protrusions, the less the number of channels, in which hot air does not pass through, and the drying process will be more uniform. To facilitate and increase the speed of the operator in the process of laying and removing the wet and dried coated monoliths (14), the upper edges of the guide rods (13) are slightly inclined outwards. The important point is that this device can be easily used to dry monoliths (14) of various sizes by changing the seat. It is just enough to design the new seat according to the diameter and dimensions of the new monolith (14).

Not all seats may be filled with monoliths (14) during device operation, depending on production capacity, or during start-up and shut-down of the device, consequently, in these conditions, most of the hot air will tend to pass through the empty seats and reach the dryer chamber. In this case, the flow of hot air passing through empty seats will be drastically reduced and as a result, the efficiency of the device will also decrease. To solve this problem, metal caps with a diameter equal to the outer diameter of the monolith (14) are made and stored in a lid container (10). When needed, the operator places these caps on the empty seats (14).

During the operation of the device, the operator places the monolith (14) in the seat position on the rotating plate (1). The operator then moves the rotating plate (1) using the control panel (12) and the monolith (14) enters the dryer chamber (5). Each time the operator moves the rotating plate (1), a wet monolith enters the drying chamber (5) and a dried monolith exits the drying chamber (5). Because the output monoliths of the drying chamber (5) have a high surface temperature, it will not be easy for the operator to remove them by hand or even with special gloves. For this reason, a cooling unit (7) is installed at the outlet of the drying chamber (5). In this unit, ambient air is blown into the surface of the dried monolith (14) using several blowers. At the outlet of the cooling unit, an operator can remove the dried part and replace it with a new part in the relevant seat and move the rotating plate (1). In this way, a single operator will be able to easily perform both the loading and unloading process of the device continuously.

Inside the drying chamber (5), the air passing through the filter (11) enters the hot air production unit (6) and after increasing the temperature, through the hot air distribution channel (3), it is guided towards the monoliths (14) on a rotating plate (1). by design, the maximum possible amount of hot air will pass through the interior of the channels of the monoliths, and this will increase the efficiency of the device. The hot air, after passing through the inside of the monolith channels, enters the drying chamber and from there, it is directed to the outlet path and the outside environment. According to the design, almost all the internal channels of the loaded parts are evenly exposed to the hot air, which means that they feel the same flow and temperature. This is one of the key points of the present design, which will lead to uniform drying of the coated slurry on the surface of different channels and will ultimately improve the uniformity of the distribution of the precious metals. To make inspections and access to the interior of the drying chamber (5) possible, access gates have been provided on different sides of the drying chamber. Also, to improve the efficiency of the device, it is possible to recover part of the hot exhaust air, through a duct between the drying chamber (5) and the inlet air filter set (11). A damper is also installed on this duct to control the amount of recovered hot air flow.

Advantageous Effects of Invention

In general, the advantages of this invention can be listed as follows:

Improving heat efficiency, saving energy, and reducing drying time

Increasing catalyst efficiency and lifetime

Saving the consumption of precious metals, working costs of the production process, and reducing the production costs

The movement path of the parts in this device is designed in a circle, and this makes it possible for an operator to both load and unloads the device, despite continuous operation.

Fig.1

This figure exhibits an explosive view of the whole invention

Fig.2

This figure exhibits the front view of the device and its dimensions

Fig.3

This figure exhibits an explosive view of the designed special seat on a rotating plate.

Fig.4

This figure exhibits the sampling points in a monolith cross-section, in accordance with US Patent No. 7,601,671 B2.

Fig.5

[Table 1] This table exhibits the results of measuring the mass percentage of platinum in specific positions of the monolithic cross-section according to , along with a comparison of the results.

First, the hot air production unit is activated so that the inlet air passes through the set of thermal elements, and the air temperature rises. After the device warms up and when the air temperature is fixed at the desired setpoint value, the operation will be started. The operator removes the lid from the seat and replaces it with a monolith. By pressing the button on the user panel, the operator issues the command to move the rotating plate, and thus, by moving the rotating plate to a certain size, the loaded part enters the drying chamber. When the amount of displacement defined for the rotating plate is completed, it stops and the operator can insert another piece. Again, the operator presses the button from the user panel, and the rotating screen proceeds by the adjusted size. In this way, the latter piece enters the drying chamber and the former piece, which was placed in the previous step, moves one step inside the chamber towards the outlet. this process continues and new parts are loaded until the first part travels the entire path of the chamber and the cooling unit. At this stage, the operator must remove the dried product and replace it with a wet monolith. From now until the device operation is finished, the operator will replace the new parts with wet ones each time.

When the operation is finished and there is no wet monolith to be charged, the operator must replace the dried part with a cap each time a dried part is removed. In this way, at the end of the process, all seats are closed again using the lid and the device will be ready to shut down.

The speed of rotation of the rotating plate, the amount of motion with each press of the button, the minimum amount of idle time of the rotating plate between two consecutive presses of the button, the speed of movement, and consequently the inlet air flow and operating temperature of the device are among the adjustable parameters which can be tuned through the control panel, with respect to the type and characteristics of the monolith to be dried. The heat load of the heating elements will also be used by the control system to regulate the operating temperature of the device.

The present invention is "A device for uniform drying of coated monolith using monotonous hot air distribution" which will be used in the production process of catalytic converters for various types of vehicles. High heat efficiency, energy-saving, reduction of drying process time, drying process uniformity and consequently saving precious metal consumption, continuous process performance, and labor-saving is among other items which guarantee the use of this equipment in the production lines of various types of catalytic converters.

Claims

The claimed invention is "A device for uniform drying of coated monolith using monotonous hot air distribution" which consists of the main frame, a hot air distribution system connected to the hot air production unit at the bottom, and a rotating plate equipped with dedicated specific seats for monolith placement located at the top of it. This device is capable of drying coated monoliths of various sizes and shapes by directing and distributing the hot air flow to the interior of the monolith channels. the proposed device recovers a portion of the exhaust hot air, and reuses it at the inlet of the device, and consists of the following components:
Rotating plate where the parts are placed

Specific seats for parts placement

Set of frame and chassis of the device

Hot air distribution channel

Rotating plate guide set

Drying chamber

Hot air production unit

Cooling unit

Control system and electrical panel

Shaft and power generation and transmission system

Lids storage compartment

Inlet air filter

User Panel
The hot air production unit consists of a blower that directs the ambient air to the heating elements chamber after passing through the inlet air filter. After heating, the air enters the hot air distribution channel. The hot air production unit, hot air distribution duct, and inlet air filter are installed on the frame and chassis of the device so that the hot air distribution duct is located just below the rotating plate. The rotating plate is connected to the shaft and the power generation and transmission system. The power generation and transmission system consist of an electric motor and a gearbox and related bearings and couplings that provide the torque needed to rotate the rotating plate and transmit the generated torque through the shaft to the rotating plate. The space around the top of the rotating plate is surrounded by a drying chamber. The rotating plate guide set is located below the rotating plate and between the rotating plate and the hot air distribution channel. The rotating plate guide set consists of a fixed center plate and a number of bearings mounted on the center plate near the peripheral edges of the rotating plate. To prevent hot air from passing through the space between the rotating plate and the rotating plate guide set, suitable seals are installed on the middle plate and near the peripheral edges of the rotating plate. Fixed diameter holes are mounted on the rotating plate. These holes are filled by seats that are customized according to the type and dimensions of the products. The top plate and the bottom plates of the specific seat are connected by guide bars and placed parallel to each other at a certain distance from each other. To place the piece properly on the seat, small protrusions are considered on the bottom plate, and metal lids, with a diameter equal to the outer diameter of the monolith, are made and kept in the storage compartment of the lids. A cooling unit is installed at the outlet of the drying chamber. In this unit, ambient air is blown into the surface of the dried monoliths using several blowers. To make possible inspections and access to the interior of the drying chamber, access gates have been provided on different sides of the drying chamber. Also, it is possible to recover part of the hot exhaust air through a connection duct between the dryer chamber and the inlet air filter set to improve the efficiency of the device. A damper is also installed on this duct to control the amount of recovered hot air flow.
According to claim 1, which is a customized specific seat that minimizes the passage of hot air through the space around the monolith.
According to claim 1, that the hot air distribution channel is such that hot air is evenly distributed between the various coated monoliths in the drying chamber and also between different channels of each monolith.
According to claim 1, which is a set of rotating plate guides, designed to prevent deformation of the rotating plate by bearing a part of its weight and to facilitate the smooth movement of the rotating plate; also, with proper sealing, it prevents the loss of hot air from the space between the rotating plate and the hot air distribution channel.
According to claim 1, in which the rotational speed of the rotating plate, its amount of motion with each press of a button, the idle time of the rotating plate between two consecutive presses of a button, the speed of movement, and consequently the inlet air flow and operating temperature of the device are the parameters that can be adjusted according to the type and specifications of the coated monolith to be dried. The heat load of the heating elements will be determined by the control system to adjust the operating temperature of the device.
According to claim 1, that by replacing specific seats, the device can be used to dry all types of car catalysts.
According to claim 1, that the protrusions embedded in the lower panel of the seat prevent the monolith from falling into the hot air distribution channel.
According to claim 1, that lids of the same size as monoliths are installed to be placed on empty seats to prevent hot air from passing through these seats.
According to claim 1, that a cooling unit is located at the outlet of the drying chamber
According to claim 1, that an inlet air filter is installed on the device to prevent the input of ambient dust into the hot air production unit and the internal side of the device.
According to claim 1, that it is possible to recover the exhaust heat by returning part of the air from the drying chamber and reusing it at the inlet of the hot air production unit.