Project BCI – Bag Filter, Gas Suspension Absorber, Reagent Dosing for a Challenging Carbon Process

Project BCI – Bag Filter, Gas Suspension Absorber, Reagent Dosing for a Challenging Carbon Process

The Problem

The client supply carbon products for the metal smelting industry to a wide range of users both in the UK and abroad.

Following a serious fire at the site resulting in the destruction of the raw material handling building and the subsequent loss of production for more than 12 months we were contacted by the client, via recommendation of a respected industry consultant.

Due to the challenging nature of the extraction system required for this application, the client’s options for an extract system at that point were limited to a single European company. That company required a 12 month period from placement of order for the design phase of the project. From initial enquiry to starting production, Filter Designs completed the project in 9 months.

The client’s process required the extraction of gases from the process, which involved mixing a hot tar pitch with raw powdered carbon.

The Solution

Our supply covered a CleanPulse filter with a rotary valve to two individual screw conveyors on the discharge system. Unlike most other systems these discharge screws fed into a bulk bag via a scalping box which features two screws which feed the carbon back into a CleanSorb tower on the inlet to the filter.

​Carbon added ‘upstream’ of the tower ensures that the carbon is constantly recirculating and new material is added.

As the quantity of material increases it reaches a high point in the re-circulating box where material is ‘scalped’ off into a bulk bag via a tubular screw.

Each of the screws in the recirculation box are inverter driven to allow full control over the rate of activated carbon use.

The filter itself is an FDL designed ‘CleanPulse’ CPB 294, designed for an air volume of 18,900Am³/hr and utilises Polyester filter bags, suitable for the operating temperature of 80°C and a 37kW inverter driven fan with a sound attenuator on the discharge.

The design of the extraction system needs to take into account the wet sticky nature of the fume and dust so stainless steel ducting was employed throughout.

FDL used ducting with silicone seals and stainless steel band clamps for each flange.

This meant that if the product built up in the ducting, it could easily be dismantled and cleaned out.

A series of stainless steel hoods and slide gate dampers to each branch of ducting were installed on the main press which forms the carbon blocks and a stainless steel chevron eliminator box was incorporated into the ducting extracting from here also.

As the batch is mixed and weighed in the tower, prior to filling each press mould, it was essential to keep the heat in the ducting.

This prevented the product cooling and solidifying so in addition to stainless modular ducting, trace heating and cladding was used.

Flexible connections are used to prevent the introduction of air breaks to allow the use of load cells for accurately weighing the batch.

Trace heated and insulated stainless steel quick connect ducting are specified.

Each branch of ducting in the tower ran back to a Carbon scrubbing ‘drop’ box where dry carbon ‘fines’ were introduced into the gas flow to absorb the fume in the process gas.

The system is sealed, so we added heaters to an air inlet damper. A non-return damper was incorporated here for safety in operation.

The carbon fines were blown from outside using three variable speed fans into cyclone drop boxes.

We installed our own design of bulk bag dispenser and a three way variable rate feeder system using pneumatic conveying hose lines.

These heated ducts run back to the filter, prior to the CleanSorb tower.

The press and tower ducting combine into a single duct and another dose of Carbon is introduced via another bulk bag dispenser, this time with a single variable speed feeder outlet.

The controls supply included a dedicated panel for the trace heating circuits which shows a live readout of the temperature inside each heated branch of ducting.

This panel also give feedback to the clients main control room.

We also provided a fully integrated controls system for the extraction system which featured a colour HMI (Human-Machine Interface) panel to allow for full control of each motor speed.

Alarm signals and states are sent back to the clients main control room.

The emergency stop system was incorporated into the clients system also for maximum safety in operation.

Full mechanical and electrical installation as well as commissioning was included in our scope to provide a complete turnkey installation.

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Project BCI - Bag Filter, Gas Suspension Absorber, Reagent Dosing for a Challenging Carbon Process

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