Thursday, March 30, 2017

Steam Boiler Optimization

Steam Boiler Optimization
The primary function of a utility boiler is to convert water into steam to be used by a steam turbine/ generator in producing electricity. The boiler consists of a furnace, where air and fuel are combined and burned to produce combustion gases, and a feedwater tube system, the contents of which are heated by these gases. The tubes are connected to the steam drum, where the generated water vapor is drawn. In larger utility boilers, if superheated steam (low vapor saturation) is to be generated, the steam through the drum is passed through superheated tubes, which are also exposed to combustion gases. Boiler drum pressures can reach 2800 psi with temperatures over 680°F. Small to intermediate size boilers can reach drum pressures between 800 and 900 psi at temperatures of only 520°F if superheated steam is desired. Small to intermediate size boilers are only being considered for this application note.

With oil‐burning and gas‐burning boiler efficiencies over 90%, power plants are examining all associated processes and controls for efficiency improvements. Between 1 and 3% of the gross work produced by a boiler is used to pump feedwater. One method of improving overall efficiency is by controlling feedwater pump speed to save on pump power.

Read the entire document below. Contact  Flow-Tech with any questions regarding boiler optimization. In Maryland call 410-666-3200. In Virginia call 804-752-3450. 

Tuesday, March 28, 2017

Tuesday, March 21, 2017

Industrial Temperature Control Basics

Process Controllers
Process Controllers used with thermocouples or RTDs
for temperature control (courtesy of Yokogawa)
The regulation of temperature is a common operation throughout many facets of modern life. Environmental control in commercial, industrial, and institutional buildings, even residential spaces, uses the regulation of temperature as the primary measure of successful operation. There are also countless applications for the control of temperature found throughout manufacturing, processing, and research. Everywhere that temperature needs to be regulated, a device or method is needed that will control the delivery of a heating or cooling means.

For industrial process applications, the temperature control function is found in two basic forms. It can reside as an operational feature within a programmable logic controller or other centralized process control device or system. Another form is a standalone process temperature controller, with self-contained input, output, processing, and user interface. Depending upon the needs of the application, one may have an advantage over the other. The evolution of both forms, integrated and standalone, has resulted in each offering consistently greater levels of functionality.

There are two basic means of temperature control, regardless of the actual device used. Open loop control delivers a predetermined amount of output action without regard to the process condition. Its simplicity makes open loop control economical. Best applications for this type of control action are processes that are well understood and that can tolerate a potentially wide variation in temperature. A change in the process condition will not be detected, or responded to, by open loop control. The second temperature control method, and the one most employed for industrial process control, is closed loop.

Closed loop control relies on an input that represents the process condition, an algorithm or internal mechanical means to produce an output action related to the process condition, and some type of output device that delivers the output action. Closed loop controllers require less process knowledge on the part of the operator than open loop to regulate temperature. The controllers rely on the internal processing and comparison of input (process temperature) to a setpoint value. The difference between the two is the deviation or error.  Generally, a greater error will produce a greater change in the output of the controller, delivering more heating or cooling to the process and driving the process temperature toward the setpoint.

The current product offering for standalone closed loop temperature controllers ranges from very simple on/off regulators to highly developed products with multiple inputs and outputs, as well as many auxiliary functions and communications. The range of product features almost assures a unit is available for every application. Evaluating the staggering range of products available and producing a good match between process requirements and product capabilities can be facilitated by reaching out to a process control products specialist. Combine your own process knowledge and experience with their product application expertise to develop effective solution options.

Wednesday, March 15, 2017

Combustion and Fired Heater E-Book

[All quoted passages in this article are taken from the Yokogawa e-book]

Yokogawa, globally recognized leader in a number of process control fields, has authored an e-book which provides useful insight into how operators of combustion based equipment and systems can improve efficiency and enhance safety by employing modern technology.

The Yokogawa e-book Combustion & Fired Heater Optimization offers "an analytical approach to improving safe & efficient operations" related to the use of combustion & fired heaters in the process industries. Through presenting an overview of combustion sources, such as furnaces and fired heaters, the book states that while "fired heaters pose a series of problems from safety risks to poor energy efficiency," those problems "represent an opportunity for improved safety, control, energy efficiency and environmental compliance." Fired heaters "account for 37% of the U.S. manufacturing energy end use." Tunable Diode Laser Spectrometer (TDLS) technology helps mitigate safety concerns by "measuring average gas concentrations across the high temperature radiant sections."

The book states that the four main concerns applicable to fired heaters are asset sustainability, inefficient operations, the operator skillset, and safety and compliance. Outdated diagnostics and controls have placed unnecessary stress on operator response, making sustainability of fired heaters difficult. The emissions of fired heaters are generally higher than designed, and can be coupled with control schemes for firing rates little changed over the past 40 years. Operators, generally, lack a clear understanding of design, and even engineering principles of heat transfer are not typically included in education related to fired heaters. Confounding the situation further, "many natural draft heaters do not meet this [safety regulation] guideline with existing instrumentation and control systems." These complications combine to form a noticeable problem Yokogawa's technology hopes to address. The company notes how the fired heater relies on natural draft instead of forced air, meaning the heaters "typically lack the degree of automation applied to other process units in the plant." Offering a full detail of both the control state of most fired heaters and their systems defines the process situation currently considered common in the field, while emphasizing high excess air as providing a "false sense of safety."

The proposed TDLS system allows for the measurement of "both the upper and lower conditions in a fired heater" by "simultaneously controlling the fuel and air supply based on fast sample intervals." Safer burner monitoring and heater efficiency results from the TDLS measurements of CO, CH4, and O2. The optimization of air flow control reduces "O2 concentration … from 6% to 2%" and increases the furnace's thermal efficiency. Combustion control is achieved by managing fuel flow and the arch draft. The TDLS integrated system works in tandem with already established logic solver systems in the plant. The TDLS technology works as a non-contacting measurement with "full diagnostic capability" and offers "distinct advantages over single point in situ analyzers" via reduction of false readings. Specific gas measurements, fast response time, optical measurement technology, and "high and variable light obstruction" are featured components of the TDLS system highlighted to show the technology's durability and flexibility. The longevity and reliability of the system is showcased by how the TDLS combustion management system has been operational in a major refinery since 2010. The percentage of excess O2 in sample fired heaters has decreased by 1% to 1.5%. Measurements by the TDLS system have been verified by other gas analyzers. The furnace conditions in the plant are more efficiently monitored and controlled. As a result, the furnace in the functional environment is "now near its optimum operating point, using minimum excess air."
Yokogawa presents a process-related problem, then details the key points of the problem while unpacking the causes. The e-book introduces Yokogawa's technology, explains the mechanics, and demonstrates how TDLS acts as a solution to the problem, supported by a tangible example. The book offers great insight for both the operational principles of fired heaters and a new technology designed to maximize efficiency in the control process.

The e-book can be downloaded here.  More detail is available from product application specialists, with whom you should share your combustion and fired heater related challenges. Combining your own facilities and process knowledge and experience with their product application expertise will lead to effective solutions.