Question

* What are the controls which are used to control the emissions of a biomass Large combustion plant? When biomass is burned :- Required Control for O Nox co 1 coz o Sox 6 Particals or Particular Matter (PM)

I need to know how we can control or reduce the pollutants or emissions of biomass combustion in a large biomass combustion plant for power generation

Answer 1

Biomass, like any other fuel, emits certain pollutants from combustion, nitrogen oxides (NOx) being one of them. Control of NOx emission, originated in biomass combustion, is becoming a very significant technical challenge due to the imposition of increasingly strict emission limits.

DeNOx TECHNIQUES The selection of biomass combustion technology is determined mainly by the characteristics of the fuel, its accessibility and annual availability, existing environmental legislation, the costs, and performance of the equipment available, as well as the energy and capacity needed (heat, electricity). For any biomass combustion application, emission reduction, besides efficiency improvement, is a major goal. Accordingly, controlling NOx emissions is becoming increasingly demanding technical challenge as tightening emissions regulations are being imposed. The NOx control technologies can broadly be classified into: 1. pre-combustion which involves the use of low nitrogen biomass or biomass blends with reduced the total N content, 2. combustion control or primary measures - modifying the design and operating features of the combustion unit, and 3. post-combustion techniques (end-of-pipe treatment) or secondary measures - flue gas treatment (FGT) after the combustion process. The pre-combustion measures refer to some affordable solutions as an informed choice of biomass (e.g. knowledge on fertilizer treatment, the length of storage and harvest time because natural senescence decreases N content, as the N is remobilized to the roots or rhizomes) and/or pretreatments with a target of minimizing heterocyclic-N-compounds?. The chemical composition of a fuel has a direct influence on NOx emissions therefore in selecting the type of biomass it is necessary to bear in mind the classification given in Table 1. Table 1. Classification of biomass fuels [22] Class Type Woodlike Strawlike N-rich (agricultural &herbaceous) Nitrogen content [w% d.a.f] <0.3 0.3-1 3 Proper selection of the biomass is illustrated in the following example - burning the kernel of various non-food cereal crops, as third class biomass fuel (see tab 1), leads to the high nitrous oxide (NOx) emissions. The answer to this issue is to burn oats because it has a lower N

content in relation to other cereals. The lower the protein level, the lower the nitrogen content of the kernel and, consequently, the lower the resulting NOx emission. For that reason, oat grain is the most common second-rate cereal- used for residential heating in Sweden [23]. The pre-combustion measures are also a modification of the fuel composition by usage of fuel additives [24), biomass fuel blending [25] and biomass co-combustion with fossil fuels [26, 27). Significant reduction potential was observed for blends with wood and herbaceous biomass [25). The use of biomass/coal co-firing decreases both NOX and SOx emissions [28]. Thus coke (the quenched char from coal) as ultra-low nitrogen fuel can be very successful at co-combustion of biomass rich in nitrogen because nitrogen in the volatile fraction of the coal is removed in making coke, while it is very rich in carbon (acting as a catalyst for the NOX reduction) Primary and secondary measures of NOx reduction are given in Figure 1. NOx control Combustion control Flue gas treatment (FGT) Wet systems Dry systems Optimum combustion • excess air • temperature } reduction • water or steam injection Absorption/Scrubbing SNCR Air staging Electron beam FGT NSCR Fuel staging SCR Pulsed corona discharge Flue gas recirculation Low NOx burner Figure 1 Overview of deNOx techniques 3. COMBUSTION CONTROL SYSTEMS Combustion control systems are commonly applied with various possible options, each resulting in a more or less significant reduction of NOx-levels formed during combustion. These options often combine several measures that rely on any of following strategies: (a) reducing peak temperatures in the combustion zone: (b) reducing the gas residence time in the high-temperature zone, (c) reducing oxygen concentrations in the combustion zone and (d) improving mixing conditions. These can be achieved either through process modifications or by modifying operating conditions on existing furnaces without the use of additional reactor/flue gas pollution abatement equipment behind the main combustion zone. Process modifications include the application of a low NOx burner, air/combustion staging, gas recirculation, reduced air preheating and combustion rates, water or steam injection, and low excess air or surplus oxygen present for combustion. The method of combustion control used
i think you must refer a research paper (it's a part of research)....as I am sharing a link

https://www.researchgate.net/publication/320848417_Denitrification_techniques_for_biomass_combustion

Thankyou.... please upvote it