Batch Plant Process of Asahi Glass

At the fall of 2006 Asahi India celebrated “ first glass” from its 700 tonnes new float line in Roorkee. It was a spectacular moment for the Eurotherm glass team that saw its 2.800 I/O point Batch House Automation system come to life, and deliver the first batches of raw material to the melting furnace. It is from that moment that Eurotherm involvement changed from system conceptual design, detailed engineering, cabinet building, system programming, testing and installation and commissioning to actual silo and hopper filing, batch weighing, batch transport, mixing and cullet returns.

The batch process of the float line has been divided into four sections. Each of the sections, or process cells, can be controlled either from the Distributed Control System (DCS) or from the Local Control System (LCS).

Silo feeding

This consists of feeding the raw matarial into one of eleven silos or hoppers. When unloaded from the trucks raw material is conveyed through a series of bucket elevators and conveyor belts to the silica, soda ash, limestone, feldspar or sodium sulphate silo.

Each of these silos are fitted with level transmitters, pressure switches and over pressure flaps that are all mounted and controlled by the EurothermSuite DCS System. The silos have a series of dedusting units that help in trapping the excess dust, which tends to rise as the silos get filled up. These dedusting units comprise of dust collectors and blower fans. At

every stage magnetic separators prevent iron impurities finding their way into silos.

Batch weighing and transport

This section deals with the weighing, dosing and transport issues of the batch plant. Dosing into the weigh scales is either through screw feeders, pneumatic feeders or vibrating feeders.

Both coarse and fine dosing from the feeders into the weigh scales is controlled by Eurotherm AC inverters. The time and sequenced dosing of the raw material is completely controlled by the EurothermSuite System.

The conveyors are again controlled by Eurotherm AC inverters.

Mixers

The plant is equipped with two mixers each driven by a 110kW motor that is controlled with a Eurotherm flux vector AC drive. Raw material is fed to the mixer that has to be filled through a swivel pipe. The EurothermSuite System also controls the elaborate water

and oil feeding options that are used to ensure that the mix reaches the desired consistency before it is fed on to the main conveyor belt.

Cullet is added to the mix on the conveyor belt to get the final mixture that is ready to be loaded in the furnace. When the final mix is not of the desired quality it is rejected and fed to a waste hopper.

A four compartment batch charger takes the final mix to the furnace silo from where it is fed into the melting furnace.

Cullet and cullet return

As with almost every glass producer, Asahi is using cullet from external suppliers or cullet that is returned from its own production line. The cullet handling part of the control system deals with the loading of the cullet silo with material of the cullet yard as well as  

the cullet crushing and return from the float line.

Eurotherm AC inverters control the operation of line crushers, water crushers finger drops and breakers as well as the conveyor

belts that transport the cullet directly back into the batching process or to the cullet yard.

Incoming cullet from external sources is loaded into a hopper that feeds the cullet to a series of crushers. On its way to the cullet silo the cullet passes magnetic detectors and magnetic separators that keep iron parts away from the silo and finally from the raw glass melt.

Safety

From a safety point of view the systems supplied are in compliance with all the relavant safety and machine directives. Emergency stop switches, pull cord switches zero speed detector units and belt sway detectors secure to bring the plant into a safe state when an

emergency does arise. 

Eurotherm supply 

Eurotherm has been responsible for the design, delivery, installation and commissioning of the DCS System and the motor control systems.

The EurothermSuite DCS System comprises of:

5 off T940X Process Supervisor (redundant)

33 off Model 2500 Process I/O units for 2,800 I/O signals

2 off Operator workstations - EurothermSuite Operation Servers

5 off Local operator stations

The model 2500 I/O units communicate with the T940X Process Supervisors via Profibus DP, whilst communication between the T940X’s among each other and the Operator workstations uses a redundant fibre optic Ethernet ring.

The motor control system comprises of 10 Eurotherm 690 Series AC inverters in a range of 10kW to 110kW. The inverters are fully integrated with the PCS system Process Supervisor using a Modbus RTU connection.

System architecture