Adsorbent Dense Loading Procedure in Plants and Refineries

This article is about Adsorbent Dense Loading Procedure in Plants and Refineries.

Adsorbent Dense Loading Procedure

1. Purpose

This article provides detailed information regarding adsorbent dense loading procedure for Eluxyl process. We remind the following important points:

• The adsorbent loading is a critical step during the internals installation of the Eluxyl adsorbent towers.
• Dense loading is the only suitable technique for adsorbent loading in the Eluxyl process, and is mandatory for achieving the design adsorbent inventory and for attaining an optimum distribution of the adsorbent particles, with a uniform loading density throughout the adsorbent beds.
• A proprietary AXENS loading device, the CATAPAC machine, is used to obtain a higher and more uniform density than any sock loading technique will permit.

2. Safety Precautions

The molecular sieve adsorbent for the Eluxyl process is an extremely powerful desiccant. While it is not toxic, its dust may irritate the eyes, nose, mouth, and skin. Therefore, adequate precautions must be taken for minimizing direct exposure to the adsorbent and inhalation of adsorbent dust.

The contact of fresh adsorbent with liquid water can release a large amount of heat, which can cause severe burns. All personnel involved in the loading must be properly instructed of the potential hazards of a non-protected exposure to the molecular sieve adsorbent.

Recommended working outfit and protective gear for personnel working inside the adsorbent towers during and after adsorbent loading consists of the following:

• Protective clothing covering the full body.
• Helmet.
• Long gloves covering the forearms.
• Safety shoes or boots with soft soles (e.g. rubber soles).
• Protective covering for dust.
• Dust masks.
• Ear protection.
• Safety harness with life line.
• Radios for communication with personnel on standby outside the adsorber.

3. MANPOWER

The adsorbent loading is an operation that must be performed safely, but also efficiently and carefully. As such, it requires a dedicated team of people that are routinely familiar with all the requirements of this work. This loading team will be working strictly under AXENS’ supervision, and according to AXENS instructions.

The loading team shall be made up of at least the following personnel, which must be available at all times during the loading:

• One foreman who is to be fluent in English, for directing the team under AXENS’ supervision.
• One forklift driver for Big Bag transportation from shelter to the pick-up point for the mobile crane
• One Big Bag handler at grade to verify that a Big Bag is not damaged before lifting, and to attach it to the crane hook.
• One crane operator to operate the mobile crane for lifting the Big Bags from the ground to their drop­ off point on the adsorbent tower top platform.
• One crane instructor to direct the crane operator for bringing the Big Bags to their precise drop-off point on the platform.
• Two top platform operators for the following operations:
  • To ensure all operations from the Big Bags reception on the top platform to the Big Bag unloading into the hopper (hoist operation, opening of the Big Bags etc…).
  • To assist the AXENS loading specialist; e.g., recording package number N and weight, sampling the bag for the composite sample of the bed, etc.
• Four operators for adsorbent bed levelling:
  • A minimum of four workers is necessary to complete the levelling of the adsorbent layer within a reasonable short time, under AXENS loading specialist instructions. While at this point the loading itself is finished, members of this group may be affected to one of the above other tasks.

Read Also: Internals Installation & Sieve Loading | Tower Internals in Plants & Refinery

4. SPECIFIC EQUIPMENTS REQUIRED FOR ADSORBENT LOADING

The purpose of this paragraph is to briefly remind all the specific equipments involved in the bed loading.

4.1 Crane(s) shared for sieve operations and panels installation

For sieve loading operation the crane should be capable to lift up to 1200 Kg to – 40-50 meters. To fit with the Catapac apparatus nominal flowrate (around 15 T/h), minimum of one sieve big bag every 4 minutes shall feed the receiving hopper.

As internals installation and sieve loading will be perfonned in parallel in the two Adsorbent Towers a proper organization shall be established:
► In case of two cranes available (1 per adsorber) are used, proper coordination between cranes operators have to be foreseen to avoid any misaction.
► In case of only one crane available for both adsorbers, the crane must be permanently available to lift the big bags. The loading operation has priority with regard to the trays installation that may go on in the other adsorbent tower.

4.2 Weighting device

A balance or a digital electronic weighting device that can be directly attached to the hook of the crane / hoist shall be foreseen:

► We remind that weight has to be recorded for each bag just prior to its transfer to the upper hopper.
► The accuracy of the weighting device shall be 1 kg maximum for a weight of big bags around 1005 Kg maximum packaging included.

4.3 Adsorbent Transportation Facilities on Site

To be foreseen to move big bags from the warehouse to the adsorbent temporary storage shelter.

4.4 Fully rain proof Adsorbent Temporary Storage Shelter available on Site

To be foreseen in case of rain to protect big bags. We remind that it is not allowed to stack the sieve big bags.

4.5 Adsorbent Handling during Loading

Forklift will be used to move the Big Bags from the adsorbent temporary storage shelter to the mobile crane lift pick-up point.

This is a delicate operation, in the sense that the forklift driver shall make sure at any time not to damage the bags. In case of any damage to a Big Bag, the adsorbent in it ( quantity: 1000 kg/bag) might be lost for loading.

4.6 Adsorbent Loading Hopper

► The loading hopper and its accessories are prefabricated in accordance with AXENS specifications.
► All parts of the hopper must be dry, clean and dust free.
► The inside surfaces of the hopper must be smooth, and free of rust and any painting or coating. Rough edges shall be grinded smooth, while sandblasting will assure a clean surface.

4. 7 Adsorbent Tower Top Manhole and Inlet Nozzle Protection

During loading, it is important to prevent the projection and free falling of the adsorbent beads from being disturbed by any external element (wind, draft):

► Both the top manhole and the adsorber inlet nozzle must thereto have suitable protective covering.
► Directions for applying these covers (typically made of thick transparent plastic) will be provided by the AXENS loading specialist.

In addition, a sufficient quantity of weatherproof covering materials (such as large tarpaulins or plastic sheets), as well as tie ropes, must be available on the top platform of the adsorbers, to be able to cover quickly all equipment for keeping it dry and clean.

4.8 Top head internal CAT AP AC platform and trolley

Refer to drawings supplied by Axens for specifications of the CAT AP AC platform and trolley and CAT AP AC position during adsorbent loading step and internals installation step.

4.9 Adsorbent Bed Levelling Accessories

At the end of the loading, it is necessary to level the adsorbent bed. Some accessories such as scrapers, levelling boards, large and small plywood’s, as well as shovels, buckets, etc. must be available to perform this operation in accordance with AXENS’ recommendations. As the only references for bed levelling will be beams and annular rings on the shell and the Center pipe, scrapers and levelling boards shall be large enough to be set over two beams.

In addition, to minimize disturbance of the adsorbent bed surface during the levelling and the subsequent tray installation, wood planks, gratings, pallets, etc. must be available that set over two beams and be used as platforms and walkways over the bed.

5. PREREQUISITES FOR ADSORBENT LOADING

5.1 Adsorbent Inventory

Prior to the actual loading, the necessary amounts of coarse and fine adsorbents for one adsorbent bed must be transferred from the warehouse to temporary storage shelter near the adsorbent towers, from where they can be withdrawn quickly once the loading starts.

Upon their arrival at site, as they are offloaded and before putting them in this temporary storage shelter, all adsorbent Big Bags shall be weighed (without pallet), and recorded with its weight on a log sheet.

Normal gross weight of a single bag is about 1004-1005 kg. If the measured gross weight exceeds 1015 kg, it is likely that the adsorbent has suffered contamination with moisture during storage. Such bags shall be set aside in the adsorbent temporary storage shelter, for AXENS to decide regarding their final use or disposal.

5.2 CATAPAC Air Supply

The pneumatic motor of the CATAPAC machine is to be driven by dry, oil-free air of IA (Instrument Air) grade quality. Supply pressure shall not be less than 7 bar.g, and shall be as constant as possible. An air hose connection shall be available near each adsorber top manway, with a supply capacity of at least 2 Nm3/min per CATAPAC machine.

Warning: The air supply for the CATAPAC machine must be DRY. The supply pressure of the air for the CATAPAC machine must be at least 7 bar.g.

5.3 Adsorbent Tower Lighting

During loading, it is important to be able to check the adsorbent bed surface profile in the tower. A powerful lighting system must be available for this purpose inside the towers (power supply 24 volts DC), set up in such a way that it does not interfere with the spreading and free fall of the adsorbent.

For operating the loading machine, the CATAPAC platform inside the adsorbent tower must be permanently illuminated during the loading. Directions regarding adequate lighting, and the mounting thereof inside the towers, will be provided by the AXENS loading specialist.

5.4 Bed Final Inspection Approved

Prior to sieve loading bed final inspection has been approved by Ax.ens and particularly:

► Tray installation is achieved and is satisfactorily checked and cleaned.
► Next tray beams are satisfactorily installed.
► Center Pipe ladder and all material for internals installation have been removed.

5.5 CATAPAC Machine Positioning inside Adsorbent Tower

The CAT AP AC machine has been installed inside the adsorbent tower by using the top platform monorail hoist. The CAT AP AC machine has been mounted on its support frame and trolley.

Caution:

Lowering the machine inside the adsorbent tower and mounting it on its trolley must be done very carefully, following precisely the instructions of the AXENS loading specialist, making sure not to damage the distributor plates of the machine.

The AXENS loading specialist has made the necessary adjustments for positioning it correctly on the frame ( centering, levelling, fastening, earthing)

Caution:

Since static electricity is generated by friction of the molecular sieve adsorbent against different parts of the CATAPAC machine, it is mandatory to electrically earth the machine as directed by the AXENS loading specialist.

6. ADSORBENT LOADING

Important Note: For proper sieve loading, it is mandatory to avoid any disruption of the machine during this phase (unless the CATAPAC is stopped by AXENS dense loader for sieve level checking).

6.1 Coarse and Fine Sieve Loading Steps

Before starting the loading, both the coarse and fine adsorbent to be loaded for one bed must be available in the adsorbent temporary storage shelter ahead of the loading. Information of the required quantity for each bed shall be given by the Axens loading specialist.

All the Big Bags intended for the loading should have been checked for any damage, and should have been pre­ weighed and pre-selected, with the measured weight marked clearly on the bag itself. Loading can start as soon as the loading hopper is full and at least one other Big Bag is available on the pick-up point for the monorail crane on the top platform. The typical steps for each big bag are:

► Transfer from the adsorbent temporary storage shelter to the mobile crane lift pick-up point.
► Lifting from ground to the top platform.
► Positioning below the hoist, using roller on the top platform.
► Lifting using the top hoist and position the bag above the top hopper. Use a digital electronic weighting device directly attached to the hook of the hoist to weight the big bag just before introduction in the hopper).
► Emptying in the hopper.
► Lifting the empty bag and its removal to a convenient location.
► Then being ready for the new bag.

Every Big Bag arriving on the top platform must be checked again for any damage due to mishandling. The weight and references of the bag must be recorded and informed to Axens loading specialist. This log sheet must be completed carefully and accurately for every bed.
Main steps of the bed loading are as follows:

► Load the coarse sieve.
► Stop the Catapac and check the levelling of sieve
► Load the fine sieve
► Stop the Catapac and check the loading. These operations could be done several times during loading of fine sieve.
► Catapac operating conditions to be adjusted if necessary.
► Carry on the loading up to the top of beams with a slight excess.

During sieve loading Axens loading specialist recommendations shall be followed.

Caution:

In case of rain, it is mandatory to stop the loading. Liquid water will irreversibly deactivate
the molecular sieve adsorbent in the Eluxyl process.

6.2 Adsorbent Sampling

For adsorbent sampling the following procedure shall be followed:
► 48 plastic bottles of 1.0 liters to be available for sampling purpose. These bottles cover shall be of the seal tight type.
► Bottles should be labelled with the adsorber identifying suffix (A or B), the bed number and small letter a orb to distinguish the first sample from the second.

► Bottle a, is immediately send to the client laboratory to perform Loss Of Ignition (LOI). LOI to be performed within less than 4 hours after the relevant bed had been loaded. This specific laboratory activity measurement has to be clearly scheduled in the lab organization.
► Bottle b is kept under dry air and completely sealed for potential cross checking analyses.
► After LOI measurement, the samples are stored and kept as reference for any analyses which might be necessary later on.

6.3 Adsorbent Bed Levelling and Cleaning

The adsorbent will be loaded with a slight excess to ensure that the whole bed volume available will be fully utilized. At the end of the adsorbent loading, it is necessary to level the adsorbent surface. This must be done as directed by the AXENS loading specialist. Throughout this operation, it is important that all personnel minimize any direct stepping on the adsorbent.

The excess adsorbent loaded into the bed must be carefully collected and together with the unused adsorbent in the loading hopper, must be transferred into (a) clean, empty drum(s) or into an empty Big Bag. The(se) drum(s) or Big Bag must be weighed, covered tightly under a nitrogen or dry air blanket, and stored until the next bed loading.

This material must be loaded immediately after the coarse adsorbent of the following bed. AXENS loading specialist must approve the final levelling and cleanliness of the bed before the following step (internals installation) can be started.

For More Information About: INSTALLATION OF ADSORBENT TOWER INTERNALS & SIEVE LOADING