Ammonia Scrubbing for Pulp Mill Gas NOx Reduction
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Solution Overview
Problem
Current methods for treating odorous gases in pulp mills result in high NOx emissions during combustion, primarily due to the reaction of ammonia with oxygen, which is environmentally harmful and exceeds regulatory limits.
Innovation Solution
A method involving scrubbing of odorous gases with an aqueous solution containing a pH-decreasing compound, such as an acid, to reduce ammonia levels before combustion, thereby minimizing NOx formation during the combustion process in regular boilers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If odorous gases are combusted in regular boilers with excess air to oxidize sulfur compounds, then sulfur compounds are effectively oxidized to sulfur dioxide and/or sulfur trioxide, but ammonia reacts with oxygen to form nitrogen oxides (NOx) which exceed environmental regulations
Solution Approach 1:
The patent applies preliminary action by removing ammonia from odorous gases before combustion through scrubbing with acidified water. This pre-treatment step reduces ammonia content to below 1000 ppm, preventing excessive NOx formation during subsequent combustion while maintaining effective sulfur compound oxidation.
Solution Approach 2:
The patent extracts the harmful ammonia component from the odorous gas mixture before combustion. By using acidified water to scrub and remove ammonia, the gas stream is purified to contain minimal ammonia, thereby eliminating the source of problematic NOx emissions during combustion.
2Object-generated harmful factors
If ammonia is removed from odorous gases by scrubbing with acidified water, then nitrogen oxide emissions during combustion are significantly reduced, but the scrubbing process requires additional equipment and operational complexity
Solution Approach 1:
The patent applies self-service by utilizing acidified water that can be generated from the pulp mill's own processes. The system uses readily available acids (sulfuric acid, hydrochloric acid, or nitric acid) already present in the mill, eliminating the need for external chemical supply chains and reducing overall system complexity.
Solution Approach 2:
The scrubbing system serves multiple functions: it removes ammonia from odorous gases, produces ammonium salts as byproducts, and can utilize acids already present in the mill's process streams. This multi-functionality reduces the need for separate dedicated systems and minimizes overall complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The scrubbing process effectively reduces ammonia levels in odorous gases, leading to significantly lower NOx emissions during combustion, aligning with environmental regulations and allowing for safe handling of odorous gases in pulp mills without excessive NOx production.
Implementation Method 1
The ammonia is removed by scrubbing with an aqueous solution, to which has been added a compound capable of decreasing a pH of the scrubbing solution
Implementation Method 2
a compound capable of decreasing a pH of the scrubbing solution, such as an acid
Implementation Method 3
The ammonia is removed by scrubbing with an aqueous solution
Data Source
AI summary
A method for removing ammonia (NH3) from a gas produced in a pulp mill (100). The method comprises producing raw non-condensable gas comprising ammonia (NH3) in the pulp mill (100) and transferring at least some of the raw non-condensable gas to a scrubber (200) containing aqueous scrubbing solution (130, 140). The method comprises adding a compound capable of decreasing a pH of the scrubbing solution to the scmbbing solution (130, 140) and in the scrubber (200), contacting the raw non-condensable gas with the scmbbing solution (130, 140), to react the ammonia (NH3) of the raw non-condensable gas with the scmbbing solution to produce clean non-condensable gas and ammonium (NH4+). A pulp mill comprising equipment for performing the method.