Characteristics of Oxyfuel and Air–Fuel Combustion in an Industrial Water Tube Boiler

Abstract

The characteristics of oxyfuel combustion are compared to those of air-fuel combustion in the furnace of a typical industrial water tube boiler. Two oxyfuel cases are considered. These correspond to 21% O 2 and 29% O 2 by volume. Validations for both oxyfuel combustion and air-fuel combustion indicate that the temperature levels are reduced in oxyfuel combustion. The results show that, as the percentage of recirculated CO 2 is increased, the temperature levels are greatly reduced. It is concluded that the flame propagation speed in O 2 /CO 2 environment is lower than that in O 2 /N 2 . It is found that the fuel and oxygen consumption rates are slower in oxyfuel combustion relative to air-fuel combustion. Heat transfer from the burnt gases to the water jacket along the different surfaces of the furnace is calculated. It is shown that the energy absorbed is much higher in the case of air-fuel combustion along all surfaces except for the end part of the furnace close to the furnace rear wall.

Review of Fuel/Oxidizer-Flexible Combustion in Gas Turbines

“…From a combustion perspective, there are also some challenges in the pathway of successful adoption of the oxy-combustion technology. The greater CO 2 concentration within the combustor (∼70% by mass) reduces the chemical kinetic rates, which, in turn, reduce the laminar burning velocity , as well as the combustion efficiency, , as compared to air combustion. The CO 2 -rich oxy-fuel premixed reactant mixture requires more oxygen (above 21%) than the corresponding air combustion system operating at the same equivalence ratio, to obtain a stable flame. , In a comparative numerical study of a porous combustor, it has been reported that oxy-combustion with an oxygen fraction of 30% by volume can yield an adiabatic flame temperature similar to that of air combustion under identical operating conditions .…”

“…Lastly, transported CO 2 can be stored safely in geographical rock deep beneath the surface of the Earth, in depleted oil fields for enhanced oil recovery processes, or in deep saline aquifers. Capturing CO 2 can be performed by three methods, pre-, post-, and oxy-fuel combustion. − In the pre-combustion technique, CO 2 is partly captured by converting the fuel into syngas before going into the combustion zone. The post-combustion technique captures CO 2 from the exhaust gas after the combustion process, through absorption, adsorption, membrane separation, or cryogenic processes. − The use of air as an oxidizer (air combustion) is, however, not beneficial from a carbon-capture perspective, because unreacted nitrogen from air forms the primary constituent of GT exhaust, which reduces the CO 2 concentration in it, thus complicating the CO 2 separation process and increasing the associated costs of carbon capture.…”

Numerical simulation of combustion, flow, and heat transfer process of an oilfield heating furnace under different production conditions

“…[6][7][8] Since boilers and industrial furnaces are one of the largest consumers of fossil fuels, optimization and retrofitting these facilities are of the most essential tasks that can be done to reduce fuel consumption and pollutant emission into the environment. 2,[9][10][11] Therefore, in order to evaluate the operation condition of oilfield heating furnace more accurately, it is necessary to carry out the numerical simulation technology study, which can lay a foundation for the realization of the national energy conservation and emission reduction binding goals.…”

Investigation of performance of fire-tube boilers integrated with ion transport membrane for oxy-fuel combustion

“…The CO/CO 2 concentration in conventional coal‐fired boiler is 95% higher than oxy‐fuel combustion with NO x emission reported to have reduced by a one‐third as a result of use of oxy‐fuel combustion . A comparison of oxy‐fuel, with nitrogen replaced by carbon dioxide, to air‐fuel combustion shows a reduced temperature levels and a slower fuel consumption in the oxy‐fuel combustion system . Pure oxygen required for oxy‐fuel combustion is produced by the cryogenic air separation technology which has been reported to be expensive and thermodynamically inefficient .…”

“…Oxy-fuel combustion is gradually gaining attention especially because of its of zero-emission potential [2] and its applicability to solid, liquid and gaseous fuel. In oxy-combustion of methane gas, CH 4 reacts with the O 2 to give a product of CO 2 + H 2 O. The CO 2 is captured after condensation of steam in a simple cooling process.…”