Dry Sorbent Injection for Low-Temperature Desulfurization
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Solution Overview
Problem
Dry scrubber desulfurization systems are ineffective during startup, shutdown, or malfunction periods due to low flue gas temperatures below 220°F, leading to higher SOx emissions, as they require temperatures above 220°F for efficient operation and alkaline slurry spraying.
Innovation Solution
Injecting dry calcium hydroxide powder into the flue gas upstream of the spray dryer absorber and downstream of the combustion chamber, followed by water spraying in the absorber to form a filter cake in the baghouse, which reduces SOx emissions without the need for liquid injection between the injection location and the spray dryer absorber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spray dryer absorber is used for desulfurization, then SOx removal efficiency is improved, but it cannot operate effectively during startup/shutdown due to low temperature below 220°F
Solution Approach 1:
The patent applies preliminary action by injecting dry calcium hydroxide powder into the flue gas stream before the spray dryer absorber processes the gas. This preliminary injection ensures that alkaline material is available in the baghouse filter cakes even when the spray dryer absorber temperature is below the 220°F threshold, enabling SOx removal during startup and shutdown periods without requiring the absorber to reach operational temperature first
Solution Approach 2:
The patent uses dry calcium hydroxide powder as an intermediary substance that bridges the gap between the flue gas stream and the baghouse filter cakes. This intermediary form of alkaline material can be introduced independently of the spray dryer absorber's thermal state, allowing the baghouse to perform desulfurization function even when the absorber cannot operate effectively due to low temperature
2Temperature
If flue gas temperature is increased to above 220°F, then spray dryer absorber operation is enabled, but during startup this temperature is not reached until after significant SOx emissions occur
Solution Approach 1:
The patent implements preliminary action by introducing dry calcium hydroxide powder into the flue gas stream before the temperature reaches 220°F. This allows the baghouse to begin capturing SOx during the warming-up period, eliminating the time delay loss associated with waiting for the spray dryer absorber to reach operational temperature before any SOx removal can occur
3Productivity
If liquid injection is used to provide alkaline material, then desulfurization can occur, but liquid must be injected between injection location and spray dryer absorber which complicates the system
Solution Approach 1:
The patent employs dry calcium hydroxide powder as a simple, easily injectable alkaline material that can be introduced directly into the flue gas stream without requiring complex liquid injection systems. The dry powder form eliminates the need for additional liquid handling equipment between the injection location and spray dryer absorber, reducing system complexity while maintaining desulfurization capability
Solution Approach 2:
The patent changes the physical state parameter of the alkaline material from liquid (slurry) to dry powder form. This parameter change allows the material to be injected directly into the gas stream without requiring liquid injection infrastructure, simplifying the system architecture while preserving the chemical functionality needed for SOx removal
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
This method allows for effective SOx emission reduction during non-steady state conditions by forming a filter cake that captures pollutants, enhancing desulfurization efficiency and reducing overall emissions, even at low temperatures, and can be implemented before the spray dryer absorber reaches operational temperature.
Implementation Method 1
injecting dry calcium hydroxide powder into the flue gas upstream of the spray dryer absorber and downstream of the combustion chamber, followed by water spraying in the absorber to form a filter cake in the baghouse, which reduces SOx emissions
Implementation Method 2
The alkaline reagent reacts with the pollutants, and particulates are formed. The water evaporates and cools the hot flue gas
Implementation Method 3
The water evaporates and cools the hot flue gas
Implementation Method 4
injecting dry calcium hydroxide powder into the flue gas upstream of the spray dryer absorber and downstream of the combustion chamber
Data Source
AI summary
Methods of reducing emissions levels during upset periods such as startup are disclosed for use with a dry scrubber desulfurization system. A dry calcium hydroxide powder is injected into the gas flowpath and hydrated in the spray dryer absorber. The resulting hydrated powder is then deposited on the filter bags in the baghouse. This can be done at lower temperatures than the spray dryer absorber would otherwise be operable, enabling desulfurization to occur earlier in the combustion process, such as during startup of a cold combustion system at ambient temperature. The operation of the combustion system can also be backed up, made up, trimmed, or augmented depending on various operating scenarios.