Complete Combustion Control for a Steam Boiler Plant

Abstract

Steam boiler is one of the most widely used industrial systems. The boiler is used in many industrial applications. It produces steam and is used for many purposes, for example as a heat exchanger used in the refining and separation of oil and is used in electricity production also. Like any combustion system, boilers burn fossil fuels to generate steam. Emissions from fuel include carbon monoxide and nitrogen oxides. Incomplete combustion increases these emissions. The way to reduce these emissions is the control of combustion to make complete combustion by monitoring exhaust components like (NOx, CO2, CO and O2). Steam boilers are usually controlled for steam pressure only without including the exhaust components in the control loop. In this paper, a limiter for exhaust components will be included in the control loop beside the steam pressure control. This paper outlines the various stages of operation involved in the conversion of a manually operated boiler towards a fully automated one. Over the years, the demand for high quality, greater efficiency and automated machines has increased. The first part of the paper focuses on passing the inputs to the boiler at a required temperature, so as to constantly maintain a particular temperature in the boiler. The air preheater and economizer help in this process. The paper mainly focuses on level, pressure and flow control at the various stages of the boiler plant. The temperature in the boiler is constantly monitored. The automation is further enhanced by constant monitoring using a Supervisory Control and Data Acquisition system (SCADA) screen which is connected to the PLC by means of a communication cable. This paper describes the construction of SCADA and the corresponding Human Machine Interface (HMI) for a steam boiler plant. This last consists of the water drum, the air heaters and the main boiler. The control system of the plant is implemented using Siemens SIMATIC S7 PLC with ladder programming and WINCC to create the SCADA/ HMI system.