FIELD OF THE INVENTION
The present invention relates to a control system of electrostatic precipitator
used for air pollution control. More particularly, the invention relates to an
advanced system for continuous and reliable monitoring of Ash level and Hopper
Heater status of Electrostatic Precipitator.
BACKGROUND OF THE INVENTION
Electrostatic precipitation is one of the most effective processes to control air
pollution generated by industrial emissions. This technique, which has proved to
be highly effective in controlling air pollution, is used for removal of undesirable
matter from a gas stream by electrostatic precipitation. Electrostatic precipitator
(hereafter referred to as ESP) is an air pollution control device designed to
electrically charge and collect particulates generated from industrial processes
such as those occurring in power plants, cement plants, pulp and paper mills and
utilities. Electrostatic dust removing basic working principle is that: when the
dust laden gas flow through the high-voltage static electric field inside ESP, dust
is charged due to collisions with positive and negative ion, under the action of
the electric field the charged dust particle moves to opposite charged electrode

plates, viz., discharge electrode and collection plate, and eventually gets
adsorbed, thus achieving dust-collecting effect. ESP is divided into a plurality of
fields depending on the dust load. During continuous operation of an
electrostatic precipitator, the dust from the collector plates and the discharge
electrodes must be periodically removed for further conveying of the collected
dust. Dust collected on the electrodes is removed by periodically rapping/hitting
the electrodes with mechanical hammers controlled by rapping motors. The
rapping mechanism is critical to ESP efficiency and so is controlled automatically
by a dedicated controlled or by the ESP Power supply controller itself.
In the ESP, the removed dust from electrodes is collected at the Hopper, which is
located at the bottom of ESP. The hopper js generally in pyramidal or conical
shape and is sized to store the collected ash for a specific period so that the ash
evacuation can occur intermittently. Electronic probes (Ash Level Indicators) are
available to sense and indicate the present storage condition. Such Ash Level
Indicators (ALI) are so positioned in Hopper typically at two locations such as
LOW and HIGH positions to indicate the ash filling. LOW position is placed at the
bottom and HIGH is placed at top of hopper. Generally, such ALI systems will
indicate its output in the form of switch such that one position of switch to
indicate ash-filled-up and one position to indicate no-ash-filled-up. The
respective user system will read such switch position and ascertain the status.
For a typical ESP of 8-field & 4-Pass, there will be 64 Hoppers and therefore 128
ALI systems. Mechanism exists in the prior art to sense Ash presence in Hopper
and suitably indicate in the form of switch.

In the ESP, Hoppers are filled with ash after rapping process. The filled-up ash is
evacuated from Hoppers through various means like ash-handling-system. For
maintaining smooth evacuation of ash, the Hopper temperature shall be kept
close to ESP inside temperature to maintain fluidity. Hopper Heaters are
employed for this purpose. They are so arranged in Hopper walls such that all
sides are uniformly heated for better efficiency. Hopper heater failures, if
unnoticed, can lead to ash build up in hopper which can eventually led to ESP
collapse. In the prior art, systems are available to uniformly heat Hopper walls
for a set temperature and suitably inform the user of the running status in the
form of switch.
The prior arts, has individual standalone control systems to cater to control and
monitoring of Heaters for hopper, shaft insulator, support insulator and Ash
Level Indicator Monitoring of ESP. In the prior art, the operator will monitor ash
filled condition and suitably operate ash evacuation system manually. Also the
operator will not have any information on the actual ash level in hopper as there
is no continuous monitoring or monitoring of intermediate levels of ash in
hopper. Existing systems provide only LOW and HIGH states of ash level in
hopper. Status of hopper, shaft and support heaters of ESP is monitored through
the status of the power supply contatctor for the heaters. This is not an accurate
method as it cannot detect heater failure. Even if the heater is damaged and

open / short circuited, existing system will show heater as running as it takes
status of the power contactor alone. Also , the prior art systems doesnot have
any signal isolator or repeater and all these status signals from Heaters and Ash
level indicators are directly going to the main control system.
The prior art for example, CN 202734909 U disclose ways to detect ash
accumulation in suitable storage area or Hopper. However, the system doesnot
have any feature for monitoring of heater status integrated to the ash level
monitoring system. It also lacks provision for signal repeater / isolation provision.
The prior art publication CN103537160A refers to a method to improve the
reliability of ESP by control of heaters. It lacks an accurate/reliable monitoring of
heater status based on current sensing. The system doesnot have provisions for
monitoring hopper ash level also.
The prior art publication, CN 201644232 U refers to a material and method of
how to heat the hopper but it does not have any provision for accurate
monitoring of the heater status.
The prior art patents for example WO 2007051239 A1 & EP 0052435 A1
discloses an integrated management system and efficiency enhancement method
for ESP. But they are not disclosing how Hopper Heater and ash level status are
monitored and used by the central control system.

Accordingly, the prior art ESPs generally lack a system for continuous and
absolute monitoring and control of Heaters for hopper and Ash Level Indicator
Monitoring of ESP . It also lacks provision for signal isolator / repeater.
OB3ECTS OF THE INVENTION
It is therefore an object of the invention to propose an advanced system for
continuous and reliable monitoring of Hopper Heater status and Ash Level Status
for efficient operation of Electro static precipitators ( ESP).
Another object of the invention is to propose an advanced system for continuous
and reliable monitoring of Hopper Heater status and Ash Level Status for efficient
operation of Electro static precipitators ( ESP) which is enabled to alert the
Central Plant Computer on potential catastrophic failure condition of ESP.
Yet another objective of the invention is to propose an advanced system for
continuous and reliable monitoring of Hopper Heater status and Ash Level Status
for efficient operation of Electro static precipitators ( ESP) in which the
hardware controllers are connected through standard communication means.
A further object of the invention is to propose an advanced system for
continuous and reliable monitoring of Hopper Heater status and Ash Level Status
for efficient operation of Electro static precipitators ( ESP) which provides signal
isolation between field level sensors and the central plant control.

SUMMARY OF THE INVENTION
Accordingly, there is provided an integrated system capable of continuous and
absolute monitoring of Hopper Heater status and Ash Level Fill-up status at
Hopper through a single common hardware.
The invented system has hardware and the associated software for continuous
and absolute monitoring of Hopper Heater status and Ash Level filled-up status
in Hopper of ESP. It has provisions to read the continouos input signals coming
from sensors and process it to interpret as ESP operating status.
The invented system has hardware and associated software components for
communicating among peers including a central computer via Controller Area
Network (CAN) and IEEE802.15.4 Wireless interface.
The invented system has hardware and associated software components for
generating continuous signals / repeats the incoming signal to. send to one or
more control systems and to suitably alert central computer for safe operation.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG 1 : Hardware scheme of the system for continuous monitoring of Ash Level
and Heater Status of ESP hopper.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Fig: 1 shows the hardware scheme of the advanced system. The controller (1)
has a Central Processing unit [CPU] (2) which is connected to other peripheral
devices via internal signal bus. The CPU (2) has an inbuilt memory to store a
computer program to execute the method steps to read input signals, process
and interpret the signals, give out control signals and to drive communication
interfaces. Field inputs are sensed through an input circuit (3) which couples
standard 4-20 mA (milli ampere) or 0 - 5 volts signals from a transducer (8) to
the CPU (2). The current transducer(8) senses the current flowing to a heater
coil(9) from a power supply(lO) and produces standard 4-20 mA (milli ampere)
or 0 - 5 volts signal. Similarly, the ash level in hoppers(7) is sensed by another
transducer (6) and produces the standard 4-20 mA (milli ampere) or 0 - 5 volts
signals to be coupled to controller (1) through an input interface (3). The
controller (1) has provision for outputting standard 4-20 mA (milli ampere) or 0 -
5 volts signal to other controllers or the central plant control system through an
output interface(4). Thus, The controller (1) can act as a signal repeater or
isolator.Communication interface circuits viz., Controller Area Network (CAN)
interface (5) and wireless IEEE802.15.4 protocol interface (11) are providing
connections to external world.The controller (1) connects the peers or the central
computer both through the Controller Area network (5) and Wireless
IEEE802.15.4 (11).

WE CLAIM :
1. An advanced system to continuously and reliably monitor hopper heater
status and Ash level of Hopper of electrostatic precipitator to enhance the
efficiency of the (ESP) comprising :
a central processing unit (CPU) having an in-built memory with control
logic, an input interface, an output interface which is on one hand
connected to multiple peripheral devices via an internal signal bus, on
the other hand operably connected to a central plant control system
including a plurality of peer controllers via open standard
communication protocol;
a first current transducer sensing current flowing through a heater coil
from a power supply and transmits signals to the (CPU);
an input circuit receiving data relating to ash-level in the hoppers
sensed by a second transducer for transmitting the data to the (CPU);
the (CPU) processing the received data and transmiting the processed
data to the central plant system including the plurality of peer
controllers via interfaces of controller Area Network and wireless
protocol interface.

2. An advanced system as claimed in 1, wherein the heater status comprises
heater fault (coil short circuit or open circuit) status or normal running status to
keep the ESP hopper at a specified temperature to fluidize ash evacuation
3. An advanced system as claimed in 1, wherein the heater status is monitored
by sensing the current flowing through the heater coil using a current transducer
which produces a standard 4-20 mA (milli ampere) or 0 - 5 volts signal to the
controller
4. An advanced system as claimed in 1, wherein the Ash level in hopper is
monitored by using a transducer which produces a standard 4-20 mA (milli
ampere) or 0 - 5 volts signal to the controller
5. An advanced system as claimed in 1, wherein the controller is capable to
receive the standard 4-20 mA or 0 - 5 volts signal from the transducers, process
it and automatically monitors the Heater status, ash level status and
communicates to the central plant control system on possible system failure due
to prevailing conditions.
6. An advanced system as claimed in 1, wherein the controller is capable of
producing standard 4-20 mA or 0 - 5 volts signal and transmitting to any other
peer controller or control system, thus acting as an analog signal repeater or
isolator.

7. An advanced system as claimed in 1, wherein the hopper heater staus and
Ash level of Hopper of ESP are consolidated in the form of communication
frames and transmitted to the central plant Control System using an open
standard communication protocol for displaying to the operator.
8. An advanced system as claimed in 7, whereas the open standard
communication protocols means includes Controller Area Network protocol and
IEEE 802.15.4 based protocols, through which the communication frames are
formatted and interfaced.

ABSTRACT

The invention relates to an advanced system to continuously and reliably monitor
hopper heater status and Ash level of Hopper of electrostatic precipitator to
enhance the efficiency of the (ESP) comprising a central processing unit (CPU)
having an in-built memory with control logic, an input interface, an output
interface which is on one hand connected to multiple peripheral devices via an
internal signal bus, on the other hand operably connected to a central plant
control system including a plurality of peer controllers via open standard
communication protocol; a first current transducer sensing current flowing
through a heater coil from a power supply and transmits signals to the (CPU); an
input circuit receiving data relating to ash-level in the hoppers sensed by a
second transducer for transmitting the data to the (CPU); the (CPU) processing
the received data and transmiting the processed data to the central plant system
including the plurality of peer controllers via interfaces of controller Area Network
and wireless protocol interface.