Consensus on Operating Practices for the Control of Feedwater and Boiler Water Chemistry in Industrial and Institutional Boilers

The Water Technology Subcommittee of the ASME Research and Technology Committee on Water and Steam in Thermal Systems, under the leadership of Mr. Robert D. Bartholomew has revised the Consensus on Operating Practices for the Control of Feedwater Boiler Water Chemistry in Modern Industrial Boilers, first published in 1979 with prior revisions published in 1994 and 1998. The task group consisted of a cross section of manufacturers, operators, chemical treatment contractors and consultants involved in the fabrication and operation of industrial and institutional boilers. Members of this group are listed in the acknowledgments. This current document is an expansion and revision of the original, with reordered and modified texts where considered necessary. While significant revisions have been incorporated, it is recognized that there are areas of operating practice not addressed herein. Additional information is available from the references. It is the plan of the ASME Research Committee to continue to review this information, and revise and reissue this document as necessary to comply with advances in boiler design and water conditioning technology.

Energy Conversion Using the Supercritical Steam Cycle

A supercritical steam (or Rankine) cycle is used today for more most of the new coal-fired power plants. More recently, it has been proposed as well for future water-cooled nuclear reactors to enhance their efficiency and to reduce their costs. This chapter provides the technical background explaining this technology. Some criteria for boiler design and operation, like drum or once-through boiler design, fixed or sliding pressure operation, and coolant mixing, are discussed in general to explain the particular challenges of supercritical steam cycles. Examples of technical solutions are given for two large-scale applications: a coal-fired power plant and a supercritical water-cooled reactor, both producing around 1000 MW electric power.

Safety issues in solid fuel heating installed in closed systems without heat dissipation devices

The objective of this paper is to raise awareness of the risk of boiling liquid expanding vapor explosions (steam explosions) in heating systems in Serbia caused by a combination of the following factors: solid fuel burning, older boiler design, closed systems, and non-installation of heat dissipation devices. The practice is in accordance with neither Standard SRPS EN 303-5:2012 nor subject literature, which both demand that this type of heating be installed in open systems. Explosions do occur; there was one in 2014 in Futog, Serbia, with fatal consequences. The main protection element, safety valve, is designed for temperatures up to 110?C. Its operation above 110?C is unknown. The experiment physically simulated the worst case scenario, where there is no circulation in the heating system. It used a 90 L water-filled vessel with six 3 kW electric heaters installed and safety valves attached. This paper presents the first results for the case where the set pressure of the safety valve was 1.5 bar and one heater of 3 kW was in operation. The results showed that the safety valve did not prevent boiling. The recorded pressure peaks were at 2.2 bar and the lows were at 0.8 bar, so its operation intensified boiling. Therefore, the system cannot be considered safe even with a brand new safety valve and at low overheating rates. Better air removal in the system is to be solved in future experiments. Tests will be done with different safety valves and overheating rates.

PERFORMANCE OPTIMIZATION OF EXISTING BOILERS AT SHAKARGANJ LLIMITED, JHANG

There are numerous well-documented phenomena that plague the efficient operation of bagasse boilers. Key Parameters that influence boiler combustion and operation are studied with the aid of combustion and flue gas analyzer. Combustion stability and efficiency is linked to various parameters such as fuel moisture and air temperatures supplied to the boiler and are investigated in this paper as part of a case study. The paper highlights number of modern developments that have been implemented at Shakarganj Limited, Jhang to optimize the existing boiler design to enhance the Boiler capacity from 65 tph to 80 tph. Along with that impact of various devices on performance improvement of boiler has been shown with experimental data for comprehensive evaluation of boiler operation and combustion efficiency. Results of suitable measures after installation of low cost retrofits to reduce losses including combustion instabilities, unburnt fuel, moisture in fuel and deposition of ash on tubes are also part of the paper.

MEASUREMENT OF THERMAL EFFICIENCY OF HEATING BOILER WITH FURNACE WALL WATERFLOW

This article deals with the improvement of thermal efficiency of heating boilers with furnace wall waterflow. During one cycle in a PK-38 boiler the average level of the heat flow decreases by 25–30 %. The incident heat flux is measured with a thermal probe which, however, gives a large error in the measurement results. Experiments show that the error depends on the penetration of the thermal probe into the outer surface of thermal zone as well as on cavities in sealing the thermal probe, and different thermophysical properties of the latter and metal material of the heating surface. The accuracy of the measured parameters is affected by the thermal probe sealing. It is found that the distortion of temperature fields is more significant at the lower boundary of the thermal probe junction at frequently used sealing. Studies show that the waterflow leads to the restoration of local coefficients of thermal efficiency to the previous values. The obtained results can be used in boiler design and allow improving the measurement methods for thermal efficiency of heating boilers with furnace wall waterflow.

Analysis of the possibility of identifying incorrect operation of heating devices in real conditions

The paper presents a preliminary stage of works aiming at a development of a method of identification of a wrong use of heating equipment under actual conditions of operation based on an a continuous analysis of oxygen level in the exhaust gas. The investigations were carried out on a test stand at the Chair of Thermal Engineering of Poznan University of Technology. For the tests, the author used a Q-EKO 15 boiler by Heiztechnik available in the Polish and European markets. In order to develop the method of identification of a wrong use of the boiler, the investigations were divided into two stages. In the first stage, the boiler was tested according to the PN-EN 303-5 standard using the manufacturer-recommended fuel. In the second stage of the investigations, an experiment was performed simulating a wrong use of the boiler burning waste material under actual conditions of operation. To this end, generally applied modifications in the boiler design were performed allowing the use of waste material as fuel. During the tests, the amount of oxygen O2 in the exhaust gas was monitored. It was observed that even slight attempt to operate the boiler incorrectly could be detected based on the analysis of the oxygen level in the exhaust gas.

PERANCANGAN BOILER DENGAN MEMANFAATKAN SAMPAH KERING UNTUK BAHAN BAKAR PLTU MINI 3 kW STT-PLN

Boiler is a heat exchanger that serves to evaporate boiler feed water to produce dry steam to drive the turbines in order to produce electricity. The fuels used in this study are dry wastes such as paper, plastic, and wood. The process of designing this boiler is carried out so that the use of diesel to generate steam on energy conversion practicum/experiment in STT-PLN is no longer needed. Instead, they can use dry waste as fuel to produce steam which later will drive the turbines. The residue of burning waste process in the form of ashes is approximately 0.053% of the weight or volume of dry waste before burnt. The calculation conducted on this works is to determine the design of evaporator and economizer pipe. The calculation is also adjusted to the generated steam needed in order to spin the turbines. The pressure produced from this boiler design should be 2.9 bar and for the amount of steam was 21 kg / hour. As a result, the calculation of evaporator surface area is 8,83 m2, result simulation HTRI 8.95m2 with 88 pipes and 1500 mm for each pipe, while the heated surface area for economizer is 0,46 m2 result simulation HTRI 0,45 m2 with 18 pipes and 400 mm long for each pipe.