Coal-fired Industrial Boilers Research Articles

Experimental simulation of the relative contribution of volatile-N and char-N to NO X formation from a low-capacity bituminous coal-fired industrial boiler

The conversion of fuel-N to NO x is the main contribution of NO x from coal-fired industrial boilers and is the least-studied modelling problem arising from coal combustion. This paper summarises the current understanding of the mechanisms that account for the formation of NO x from fuel-N during coal combustion. Further experimentation on NO x emissions during bituminous coal combustion was simulated with attention focused on the contribution of char-N and volatile-N to fuel-NO x through the Coal/Char combustion method. The critical analysis of this issue allowed for the identification of uncertainties and produced well-founded conclusions. The results indicated that fuel-NO x formation was a very complex physical-chemical process involving many competing mechanisms. These mechanisms included chemical reactions, convective mass transfer, heat transfer, adsorption and desorption. The contribution of char-N in this experiment varied between 30% and 70%. There may be a slight question as to the exact identity of the main contributor to fuel-NO x , and no definitive conclusion can be made as of yet. This uncertainty is because the contribution of char-N to fuel-NO x was heavily affected by the combustion conditions and the contribution of char-N increased monotonically as temperature increased. There was a critical point in the relationship between particle size, air flow, O2 concentration and the contribution of char-N. The contribution of char-N increased with the increase of particle size and air flow initially when less than the critical value, and decreased when more than thecritical value. The contribution of char-N initially decreased when the O2 concentration was increased from 10% to 15% and increased more with the further increase in O2 concentration.

An optical system for measuring nitric oxide using spectral separation techniques

An optical sensor based on differential absorption spectroscopy for real-time monitoring of industrial nitric oxide (NO) gas emission is described. The influence of gas absorption interference from sulfur dioxide (SO2) in the environment was considered and a spectral separation technique was developed in order to eliminate this interference effect. The absorption spectrum of SO2 around 226 nm was evaluated by the SO2 concentration obtained using the experimentally recorded absorption spectrum around 300 nm. The absorption spectrum of NO around 226 nm was obtained by subtracting the absorption of SO2 from the integral absorption spectrum of SO2 and NO. The concentration measurements were performed at atmospheric pressure. The technique was found to have a lower detection limit of 0.8 ppm for NO per meter path length (SNR=2) and be immune from the influence from SO2 on the NO measurement. The sensor based on this technique was successfully employed for in situ measurement of SO2 and NO concentrations in the flue gas emitted from an industrial coal-fired boiler.

Simultaneous measurements of the release of atomic sodium, particle diameter and particle temperature for a single burning coal particle

The temporal history of the release of volatile alkali species during coal combustion is a significant, but poorly understood factor in the fouling and corrosion of heat transfer surfaces within industrial coal-fired boilers. We present new results of the simultaneous measurement of particle temperature, particle size and the atomic sodium concentration in the plume of a burning coal particle. During the char phase, the sodium concentration in the plume was found to be linearly dependent on the inverse of particle diameter, but during the ash phase the sodium concentration was found to decay exponentially with decreasing particle temperature. The centreline decay of Na within the plume above the burning particle consists of one region controlled by a first order chemical reaction and a second region controlled by diffusion.

Quantitative measurement of atomic sodium in the plume of a single burning coal particle

The release of volatile sodium during coal combustion is a significant factor in the fouling and corrosion of heat transfer surfaces within industrial coal-fired boilers. A method for measuring the temporal release of atomic sodium from a single coal particle is described. Laser absorption was used to calibrate laser-induced fluorescence measurements of atomic sodium utilising the sodium D1 line (589.59 nm) in a purpose-designed flat flame environment. The calibration was then applied to planar laser-induced fluorescence measurements of sodium atoms in the plume from a single Victorian brown coal particle (53 mg) suspended within the flat flame. The peak concentration of atomic sodium was approximately 64.1 ppb after 1080.5 s, which appears to correspond to the end of char combustion. To our knowledge this is the first in situ quantitative measurement of the concentration field of atomic sodium in the plume above a burning particle. A simple kinetic model has been used to estimate the rate of sodium decay in the post-flame gases. Comparison of the estimated and measured decay rates showed reasonable agreement.

Broadband spectroscopic sensor for real-time monitoring of industrial SO_2 emissions

A spectroscopic system for continuous real-time monitoring of SO(2) concentrations in industrial emissions was developed. The sensor is well suited for field applications due to simple and compact instrumental design, and robust data evaluation based on ultraviolet broadband absorption without the use of any calibration cell. The sensor has a detection limit of 1 ppm, and was employed both for gas-flow simulations with and without suspended particles, and for in situ measurement of SO(2) concentrations in the flue gas emitted from an industrial coal-fired boiler. The price/performance ratio of the instrument is expected to be superior to other comparable real-time monitoring systems.

Feasibility Analysis of Wood Pellets Production and Utilization in China as a Substitute for Coal

Wood pellets are regarded as one of the substitutes for fossil fuels like coal and oil for heating and co-generation. Wood pellets are a successful example of market penetration of renewable energy in some countries in Europe, e.g., Sweden. An analysis process is proposed in this paper and used to conduct a techno-economic assessment of wood pellets production and applications in some areas in China with the consideration of technology transfer from Sweden by examining their market competitiveness with coal in these areas. Financial indices such as net present value (NPV), internal return rate (IRR) and year-to-positive cash flow are calculated to investigate the profitability of the technology transfer. Four locations of applications in China have been considered as case studies. The result indicates that in the market-only-based scenario, wood pellets production will not be profitable in all selected areas. New scenarios from the analysis process show that reducing investment and increasing the amount of bank loan will be helpful to increase the project’s profitability in general; adding taxes on coal could be effective, but it depends on Chinese government’s future efforts on climate change mitigation; carbon credits on wood pellets through the clean development mechanism (CDM) might make wood pellet projects profitable giving wood pellets a nich-market. The potential global environment benefits of CO2 emission reduction by using wood pellets to replace coal in a 7 MWth coal-fired industrial boiler with a thermal efficiency of 80% and 5000 hours of operation time are also presented.

Evolution of particulate regulation in China--prospects and challenges of exposure-based control.

China's urban and rural populations face very serious health risks from combustion particles. Major sources of exposure to inhalable particulates include the burning solid fuels (biomass and coal) for household cooking and heating, coal-fired industrial and residential boilers, tobacco smoking, and diesel motor vehicles. China began to address particulate pollution problems over 25 years ago and has implemented a series of progressively more aggressive policies. This paper reviews the successes and limitations of past and existing policies for particulate controls, as well as the effects of China's economic reforms and energy policies on particulate exposure and pollution management. We examine the challenge of emissions reporting, required as part of both China's pollution levy system and emerging system for "total emissions control." Finally, we discuss practical steps toward exposure-based regulation of particulates, which would take advantage of the high cost-effectiveness for lifesaving of controlling particulate exposure from household and neighborhood sources relative to that of controlling exposure from industrial sources.

A proposed industrial-boiler efficiency program in Shanxi: potential CO 2-mitigation, health benefits and associated costs

An industrial boiler-efficiency improvement program (IBEI) that focuses on simple, inexpensive measures to improve the operating efficiency of coal-fired industrial boilers in Shanxi, China, is presented. The potential mitigation of CO 2 emissions and its cost, based on this program, are calculated together with estimates of health benefits associated with the reduction of air pollution. The results show that, if the average efficiency of industrial boilers were improved from 60 to 70%, 3 million tons of coal could be saved, and CO 2 emissions be reduced by 5 million tons annually at a cost of less than US$2 per ton of CO 2. The health benefits are valued at about US$86 million per year, including the avoidance of about 700 premature deaths annually. The proposed IBEI program would, therefore provide an ideal case by which to address the issue of global warming in China and to achieve national goals concerning the growth of the economy, and environmental protection.

00/02973 SO 2 pollution from industrial coal-fired boiler and application of industrial sulfur-fixed coal

Municipal solid waste incinerator (MSWI) fly ash has been examined for possible use as landfill interim cover. For this aim, three anaerobic bioreactors, 1.2 m high and 0.2 m in diameter, were used to assess the co-digestion or co-disposal performance of MSW and MSWI fly ash. Two bioreactors contained ratios of 10 and 20 g fly ash per liter of MSW (or 0.2 and 0.4 g g−1 VS, that is, 0.2 and 0.4 g fly ash per gram volatile solids (VS) of MSW). The remaining bioreactor was used as control, without fly ash addition. The results showed that gas production rate was enhanced by the appropriate addition of MSWI fly ash, with a rate of ∼6.5 l day−1 kg−1 VS at peak production in the ash-added bioreactors, compared to ∼4 l day−1 kg−1 VS in control. Conductivity, alkali metals and VS in leachate were higher in the fly ash-added bioreactors compared to control. The results show that MSW decomposition was maintained throughout at near-neutral pH and might be improved by release of alkali and trace metals from fly ash. Heavy metals exerted no inhibitory effect on MSW digestion in all three bioreactors. These phenomena indicate that proper amounts of MSWI fly ash, co-disposed or co-digested with MSW, could facilitate bacterial activity, digestion efficiency and gas production rates.

00/00395 A comparison between ceramic membrane filters and conventional fabric filters for fine particulate removal from a coal-fired industrial boiler

Penn State is developing technologies for ultralow emissions when firing coal-based fuels, i.e., micronized coal and coal-water slurry fuel (CWSF) in industrial boilers. Emissions being addressed are SO{sub 2}, NOx, fine particulate matter (PM{sub 10} and PM{sub 2.5}), and air toxics (trace elements and volatile organic compounds). Results from trace element and polynuclear aromatic hydrocarbon emissions testing, when firing coal-based fuels, are reported elsewhere in these proceedings. This paper discusses the evaluation of ceramic membrane filters for fine particulate removal in a package boiler when firing micronized coal and CWSF.

96/03144 - Co-combustion of production residues in brown coal-fired industrial boilers

96/03144 - Co-combustion of production residues in brown coal-fired industrial boilers

Distributed multivariable control system design for coal-fired boilers

Abstract This paper describes the multivariable characteristics of industrial coal-fired boilers and associated mathematical models, such as combustion model, a water drum level model and a superheated steam model. The purpose of the paper is to design multivariable control systems using multivariable system frequency domain design theory and the Smith-predictor technique. A specific application shows how to design a model-based distributed multivariable control system for coal-fired boilers in a small-scale power station.

048 Knowledge based intelligent control system for industrial coal-fired boiler

048 Knowledge based intelligent control system for industrial coal-fired boiler

Knowledge Based Intelligent Control System for Industrial Coal-Fired Boiler

The hierarchical intelligent control structure of expert control—multimode control—self-tuning PID control is presented in the paper. The authors propose an expert control algorithm for burning process of industrial coal-fired boiler on the basis of summing up knowledge and judgement from control expert and experienced boiler operator, comprehesively considering the current values and changing trends of relevant running parameters, and taking the furnace temperature as the principal one. The results of digital and hybrid simulation as well as industrial worksite running show that the design of the knowledge based intelligent control system for industrial boiler and the scheme of multi-mode control and self-tuning algorithm of PID parameters discussed in this paper are feasible. Thus the control effect on coal-fired boiler is obviously improved.

Emissions of trace elements from coal-fired industrial boilers

Discharges to atmosphere of eleven potentially harmful trace elements from both stoker-fired and fluidized bed-fired industrial boilers have been measured. For most elements; rates of emissions depend on the efficiency of the cleaning plant. Arsenic, however, is critically affected by the gas exit temperature and showed an eleven-fold variation in emission rate over the range of temperatures encountered. In general, rates of emission to atmosphere were so low that estimated ground level concentrations were smaller by several orders of magnitude than the values commonly assumed for whole population exposure limits.

Emission of trace elements from coal-fired industrial boilers. A survey of relevant literature

Present evidence is not sufficient for an evaluation of the hazard, if any, that might be caused by trace elements as a result of the increasing industrial market for coal. Measurements are reported for large pulverized fuel plant and small experimental, fluidized bed combustion rigs but there are hardly any data relating to industrial boilers. Present data are too inconsistent to permit generalized conclusions. Methods of sampling, sample preparation and analysis are assessed and those most suitable for a comparison of emissions from fluidized bed and stoker fired boilers are indicated.

Analysis of Industrial Boiler Solid Waste Impacts

This paper presents an examination of industrial coal-fired boiler waste products. Presently the atmospheric emissions from all new boilers larger than 250 × 106 Btu/hr are controlled by existing New Source Performance Standards, and boilers smaller than 250 × 106 Btu/hr are controlled to levels required by the regulations of the particular state in which the facility is located. The 1977 Clean Air Act Amendments, however, specify categories of sources for which EPA must develop revised New Source Performance Standards. Industrial coal-fired boilers are included as one of these categories, and a relevant issue concerns the potential amount of solid waste generated as a result of tightened emission standards that require flue gas desulfurization. This paper examines the air quality and solid waste impacts of moderate and stringent emission controls for particulate and SO2 emissions from industrial coal-fired boilers. Comparisons are presented of physical and chemical characterizations of the emissions and ...