Multi-Coal Fired Boiler Optimum Control

Multi-Coal Fired Boiler Optimum Control uses a proprietary algorithm from MHI. It monitors the characteristics of coal and the status of combustion in the boiler based on the heat balance of each heating surface of the boiler to support optimum control. This function runs on an operator station (OPS) from DIASYS Netmation.

• DIASYS Netmation
• Operator Station

Features

• A large number of successful deliveries
  Since the first delivery in 1997, a large number of Multi-Coal Fired Boiler Optimum Control systems have been delivered for Mitsubishi supercritical-pressure variable-pressure once-through boilers.
  Parts of this system have also been delivered for drum type boiler plants.
• Changing parameters is not necessary when coal types are switched
  The control parameters of the boiler are automatically set based on estimates of the state of the heating surfaces of the boiler. Consequently, changing parameters whenever a different coal type or coal type group is used is no longer necessary.
  Multi-Coal Fired Boiler Optimum Control can automatically set the control parameters for a boiler even when blended coal is used.
• Shorter adjustment period when a new type of coal is used
  Even when a new type of coal is decided to be used, if it can be burned mechanically by adjusting combustion, Multi-Coal Fired Boiler Optimum Control can reduce or even eliminate the APC adjustment period.

Functions

Multi-Coal Fired Boiler Optimum Control offers the following functions.

Item		Brief description
Characteristics change by coal type (heat absorption characteristics, generated heat)	Estimation of the heat absorption distribution (heat absorption index)	If the heat absorbed by each heating surface is estimated, the control parameters can be adjusted for the heat absorbed by the boiler. Consequently, compared to the case where the control parameters are switched based on a coal type group, more precise control parameters can be fed.
	Adjustment for generated heat	If the heat absorbed by each heating surface is estimated, the heat input from the coal and air and the heat output to the gas at the boiler exit can be calculated online. Based on the heat input and output, the generated heat can be estimated, and the fuel parameters can be adjusted in a precise manner.
	Estimation of the moisture content of the coal	The moisture content of the coal can be estimated from the heat balance in the mill. Using this estimation along with the mill current and roller lift, you can get the characteristics of the columnar coal and automatically set the parameters related to the mill, such as the mill exit temperature, the rotation speed of the mill rotating classifier, and the oil pressure of the mill pressure device.
	Estimation of the mill load ratio	By using model calculations based on a mill model, the hard grove index (HGI) can be estimated. By using this estimation along with the estimate of the moisture content of the coal, you can adjust the reference capacity of the mill, and you can estimate the mill load ratio from the actual amount of supplied coal.
Boiler characteristics change over time	Estimation of the cleanness of the heating surfaces	If the heat absorbed by each heating surface is estimated, the thermal conductivity can be calculated online. As the combustion in the boiler continues, the thermal conductivity decreases. Optimum timing of activating soot blowers should be based on time and also on the thermal conductivity as a good indicator.

System Configuration

• Real-time calculation based on fuzzy logic
  The state of heating surfaces can be estimated based on fuzzy logic. The effect of a coal type can be calculated with high precision in real time from the absorbed heat.
• Constructed from software logic
  The whole Multi-Coal Fired Boiler Optimum Control can be constructed with DIASYS software logic using the Mitsubishi Interpreter DDC Oriented Language (Mitsubishi IDOL).
• Easy extension from a preexisting system
  Except for a few sensors(Note), all sensors necessary for Multi-Coal Fired Boiler Optimum Control are already built into a plant control unit (APC).

(Note) RH spray water flow meter, primary RH entrance steam flow meter, and denitrification entrance gas temperature sensor

Specifications

Hardware specifications

The specifications of the hardware necessary for Multi-Coal Fired Boiler Optimum Control are as follows.

Item		Specification
Model		DIASYS Netmation(duplexed CPU, single PIO system)
Structure		IP-33(dust-proof, water-proof)
Conditions		0 - 54 deg C / 90%RH or less
Num of boards/Dimensions		1board / 800mm(W) x 800mm(D) x 2300mm(H)
Insulation resistance		500VDC / 5MΩ or greater Power supply-FG or I/O modules-FG
Withstand voltage	Power supply-FG	2000VAC/1minute
	Digital I/O terminal-FG	1500VAC/1minute
	Analog I/O terminal-FG	500VAC/1minute
Coating		External,internal,channel base : Munsell 5Y7/1(half gloss)
Other feature		Dedicated maintenance tool and gateway device (to interface with systems other than DIASYS Netmation)

Software specifications

The specifications of the software necessary for Multi-Coal Fired Boiler Optimum Control are as follows.

Item	Variable-pressure once-through boiler	Constant-pressure once-through boiler	Drum boiler
Description lunguage	Mitsubishi Interpreter DDC Oriented Language(IDOL)
Operating speed	100msec
Number of control roops	Depends on the mounted features and existing system.
Absorbed heat quantity index	Available(load change test with at least 3 coal types is required)		Not available
Heating value adjustment	Availbale		Not available
Heating surface fouling	Detected
Moisture percentage in coal	Detected(estimated for each mill)
Mill load factor	Detected(estimated for each mill)