The combustion within the boiler burns fuel to create heat energy which then produces electrical power. The combustion of fuel is its reaction with oxygen available in the air. The amount of fuel that can be well burnt is limited by the quantity of oxygen. Once all the fuel is not burnt at all, some of it stays in the boiler and other quantity goes to the atmosphere. Most of the fuels used in the boiler are hydrocarbons which release hydrogen and carbon as residuals. It causes small efficiency

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... nd degradation of the air. It is needed to take the faction of air/fuel to the optimum value to reduce these problems. This paper provides different reviewed algorithms that control the combustion within the boiler and the role of environmental temperature. The author found that the separation of the oxygen from the air combined with the preheating both fuel and oxygen taking into account environmental temperature would provide better stoichiometric values, which improve the performance. [4]. This means for every mole of fuel to be burned require moles of Oxygen and ( ) moles of Nitrogen, and ( ) moles of Nitrite is generated [4], [6]. The stoichiometric or air-fuel ratio (AFR) is the fraction of the air to fuel in the combustion process within the boiler and others for the thermal power plant to burn the fuel to produce heat energy which then transformed into kinetic energy [7] . In the case this ratio is small (when the air is insufficient), it results in incomplete combustion which is the cause of low efficiency and much exhaust gases. [8] In the cases of bigger ratio (too much air presence), there will be the formation of much nitrogen ( ) as indicated by Figure 1 and its composition such as nitrite oxide as indicated by Figure 4 [9] , which are losses and at the same time are accumulated within the burner then disable the next process while reducing the lifetime of the boiler [10]. Different researches have been conducted to control this AFR however there is still a lack of the best way to achieve the exact value of AFR to have optimum combustion considering fuel properties, outdoor temperature, impurities attached to hydrocarbon. This paper reviews the research done so far for various types of fuel. Some determine the novelty of increasing and decreasing the burning air, others explore the role of oxygen and impurities separation, while some of them investigate the impacts of the external climate. Some control algorithms have also been reviewed and discussed. Reviewing the literature gives the capability of comparison in view to choose what can be adapted for the project planned considering the specific situation. The authors also look at the gap of each method and then find the additional thing to do for better results. This paper reviews different models and control parameters in Section 2. In section 3 the impact of climate characteristics is reviewed, and the last section draws the summary and conclusion.