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Title: Coal gasification system with a modulated on/off control system

Abstract

A modulated control system is provided for improving regulation of the bed level in a fixed-bed coal gasifier into which coal is fed from a rotary coal feeder. A nuclear bed level gauge using a cobalt source and an ion chamber detector is used to detect the coal bed level in the gasifier. The detector signal is compared to a bed level set point signal in a primary controller which operates in proportional/integral modes to produce an error signal. The error signal is modulated by the injection of a triangular wave signal of a frequency of about 0.0004 Hz and an amplitude of about 80% of the primary deadband. The modulated error signal is fed to a triple-deadband secondary controller which jogs the coal feeder speed up or down by on/off control of a feeder speed change driver such that the gasifier bed level is driven toward the set point while preventing excessive cycling (oscillation) common in on/off mode automatic controllers of this type. Regulation of the bed level is achieved without excessive feeder speed control jogging.

Inventors:
 [1]
  1. (Morgantown, WV)
Issue Date:
Research Org.:
National Energy Technology Laboratory, Pittsburgh, PA, and Morgantown, WV
OSTI Identifier:
865044
Patent Number(s):
4453950
Assignee:
United States of America as represented by United States (Washington, DC) NETL
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
coal; gasification; modulated; control; provided; improving; regulation; bed; level; fixed-bed; gasifier; fed; rotary; feeder; nuclear; gauge; cobalt; source; chamber; detector; detect; signal; compared; set; primary; controller; operates; proportional; integral; modes; produce; error; injection; triangular; wave; frequency; 0004; hz; amplitude; 80; deadband; triple-deadband; secondary; jogs; speed; change; driver; driven; preventing; excessive; cycling; oscillation; common; mode; automatic; controllers; type; achieved; jogging; speed control; coal feeder; fixed-bed coal; automatic control; preventing excessive; coal feed; coal bed; bed level; coal gasifier; coal gasification; error signal; coal gas; bed coal; triangular wave; wave signal; modulated control; detector signal; chamber detector; /48/414/422/

Citation Formats

Fasching, George E. Coal gasification system with a modulated on/off control system. United States: N. p., 1984. Web.
Fasching, George E. Coal gasification system with a modulated on/off control system. United States.
Fasching, George E. Sun . "Coal gasification system with a modulated on/off control system". United States. https://www.osti.gov/servlets/purl/865044.
@article{osti_865044,
title = {Coal gasification system with a modulated on/off control system},
author = {Fasching, George E.},
abstractNote = {A modulated control system is provided for improving regulation of the bed level in a fixed-bed coal gasifier into which coal is fed from a rotary coal feeder. A nuclear bed level gauge using a cobalt source and an ion chamber detector is used to detect the coal bed level in the gasifier. The detector signal is compared to a bed level set point signal in a primary controller which operates in proportional/integral modes to produce an error signal. The error signal is modulated by the injection of a triangular wave signal of a frequency of about 0.0004 Hz and an amplitude of about 80% of the primary deadband. The modulated error signal is fed to a triple-deadband secondary controller which jogs the coal feeder speed up or down by on/off control of a feeder speed change driver such that the gasifier bed level is driven toward the set point while preventing excessive cycling (oscillation) common in on/off mode automatic controllers of this type. Regulation of the bed level is achieved without excessive feeder speed control jogging.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1984},
month = {1}
}

Patent:

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