Boilers optimization

Model-based boiler optimization schemes have proved successful in many power plant and industrial boiler applications. Successful NOx reduction through this kind of optimization can avoid or postpone large capital expenditures for low NOx burners, over-fire air modifications, and selective catalytic reduction/selective noncatalytic reduction (SCR/SNCR). 

The models are a set of equations that relate key performance measurements to the major control variables influencing combustion efficiency. Owing to the complexity and uncertainty of the analytical models that are derived from physical principles, empirical models, based entirely upon the plant data, are typically used for practical boiler optimization control. 

Closed-loop multivariable boiler control has to be planned and performed carefully because plant operators are not traditionally willing to reduce air-fuel ratios due to concerns about CO and other symptoms associated with Oz-deficient combustion. Model predictive control (MPC) is by far the most widely used technique for conducting multivariable boiler optimization and control. Forms of MPC that are inherently multivariable and that include real-time constrained optimization in the design are best suited for boiler application. 

Zolo Technologies, Inc. "Introducing ZoloBOSS Boiler Optimization Spectroscopy Sensor." Zolo Technologies, Inc., Presentation, 2009b. http //www.zolotech.com/ pdfs/2008-ZoloBOSS.pdf (accessed April 24, 2009). 

Optimized modern dry scrubbing systems for incinerator gas cleaning are much more effective (and expensive) than their counterparts used so far for utility boiler flue gas cleaning. Brinckman and Maresca [ASME Med. Waste Symp. (1992)] describe the use of dry hydrated lime or sodium bicarbonate injection followed by membrane filtration as preferred treatment technology for control of acid gas and particulate matter emissions from modular medical waste incinerators, which have especially high dioxin emissions. 

Once the highest steam level is set, then intermediate levels must be established. This involves having certain turbines exhaust at intermediate pressures required of lower pressure steam users. These decisions and balances should be done by in-house or contractor personnel having extensive utility experience. People experienced in this work can perform the balances more expeditiously than people with primarily process experience. Utility specialists are experienced in working with boiler manufacturers on the one hand and turbine manufacturers on the other. They have the contacts as well as knowledge of standard procedures and equipment size plateaus to provide commercially workable and optimum systems. At least one company uses a linear program as an aid in steam system optimization. 

NOTE Probably the most important junction of oxygen scavengers is, in reality, the ability to passivate boiler steel. In recognition of this, today most novel oxygen scavenger trials try to identify, not merely comparative oxygen reaction rates, but more importantly, the reduction in iron and copper transport rates through the boiler system. In other words, they seek to optimize the passivation of boiler surfaces and other system components. 

Optimizing Treatment Programs and Control Parameters in High-Pressure Industrial Boilers... 

The transport of iron oxides throughout the system is a very noticeable effect resulting from less than fully optimized chemical treatment programs and associated control parameters in high-pressure boilers. 

As described in the methodology, the curve starts from an optimized operation for the initial process steam demands (Figure 23.54b). At this initial point, the HP extraction of Turbine T4 is set to its minimum of 15 th-1. The first HP segment saves steam by reducing the HP extraction of Turbine T6. Part of this saving is realized by reduction in steam generation in Boiler 2 and the remainder by increasing the LP exhaust of Turbine T6 and the LP... 

Another example of optimization can be encountered in the operation of a boiler. Engineers focus attention on utilities and powerhouse operations within refineries and... 

EXAMPLE 11.4 BOILER/TURBO-GENERATOR SYSTEM OPTIMIZATION... 

Example 11.4 Boiler/Turbo-Generator System Optimization 435... 

In flue gases MISiC sensors can be used to either monitor the gas components, such as CO, nitric oxide (NO), and oxygen, or identify different modes of combustion in the boilers of small power plants. In this way, it is possible to optimize the combustion in boilers of about 0.5-5 MW in which optical techniques such as Fourier transform infrared (FTIR) are too expensive and complex. The authors have performed measurements in a 100-MW boiler, which has been used to heat houses and industries and generate electricity in Nykoping, Sweden, and in which there was a natural randomization of the flue gases [59]. Data was collected over several... 

Consider a forced-draft boiler producing 600-psig steam as shown in Fig. 20.2. The fuel rate on this boiler is fixed and we are going to optimize the oxygen (02) content of the flue gas by adjusting the speed of the forced-draft fan. Do we simply adjust the forced-draft (FD) fan to give 2 percent 02 in the stack because someone once said that 2 percent 02 in the stack was a good number ... 

Process synthesis and design of these non-conventional distillation processes proceed in two steps. The first step—process synthesis—is the selection of one or more candidate entrainers along with the computation of thermodynamic properties like residue curve maps that help assess many column features such as the adequate column configuration and the corresponding product cuts sequence. The second step—process design—involves the search for optimal values of batch distillation parameters such as the entrainer amount, reflux ratio, boiler duty and number of stages. The complexity of the second step depends on the solutions obtained at the previous level, because efficiency in azeotropic and extractive distillation is largely determined by the mixture thermodynamic properties that are closely linked to the nature of the entrainer. Hence, we have established a complete set of rules for the selection of feasible entrainers for the separation of non ideal mixtures... 

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