Heat Exchanger Anti-Icing via Recirculation Conduit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ammonia and hydrogen production processes face issues with icing in heat exchangers at low ambient temperatures, leading to potential damage and inefficient operation, and the use of glycol-water mixtures is undesirable.
Innovation Solution
The apparatus includes a recirculation conduit that preheats a gas stream using waste heat from a steam reformer, which is then used to maintain the heat exchanger above the freezing point, preventing icing and allowing for efficient start-up and operation, even at low ambient temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a heat exchanger is used to preheat combustion air in a steam reformer, then energy efficiency is improved by recovering waste heat, but at low ambient temperatures the heat exchanger experiences icing which leads to damage and operational failures
Solution Approach 1:
The patent introduces a recirculation line that allows process gas to circulate through the heat exchanger before the formal start-up process begins. This preliminary circulation preheats the heat exchanger walls and prevents freezing of the heating medium during cold start-up conditions, while still maintaining energy efficiency through waste heat recovery.
Solution Approach 2:
The patent uses a recirculating process gas stream as an intermediary medium to transfer heat from the waste heat section to the heat exchanger during start-up. This intermediary approach allows controlled heat transfer without directly exposing the heating medium to freezing temperatures, thereby protecting the heat exchanger while maintaining energy recovery.
2Reliability
If glycol-water mixture is used as heating medium to prevent freezing, then freezing protection is improved, but the complexity of the system increases and glycol availability becomes a constraint
Solution Approach 1:
The patent enables the heat exchanger to serve itself during start-up by recirculating process gas through the heat exchanger before formal operation begins. This self-service approach preheats the heat exchanger walls using waste heat, eliminating the need for external anti-freeze measures like glycol-water mixtures and reducing system complexity.
Solution Approach 2:
The patent changes the operational parameters by introducing a preliminary recirculation phase before formal start-up. During this phase, the heat exchanger operates at different temperature and flow conditions to gradually warm up the walls, preventing freezing without requiring chemical additives or complex heating systems.
3Reliability
If the heat exchanger is operated with process condensate during start-up, then the freezing point is lowered, but the wall temperature corresponds merely to exterior temperature which causes freezing before the heating medium is available
Solution Approach 1:
The patent performs preliminary heating of the heat exchanger walls by recirculating process gas through the heat exchanger before process condensate becomes available. This preliminary action raises the wall temperature above freezing point in advance, preventing freezing when the heating medium is finally introduced and reducing overall start-up time.
Solution Approach 2:
The patent maintains continuous useful action by recirculating process gas through the heat exchanger during the entire pre-start-up period. This continuous circulation ensures constant heat transfer to the heat exchanger walls, maintaining them above freezing temperature throughout the waiting period for heating medium availability.
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 solution effectively prevents freezing in the heat exchanger, ensuring damage-free and efficient operation of ammonia or hydrogen production plants by utilizing waste heat to maintain the heat exchanger temperature above freezing, even during unplanned low ambient temperatures.
Implementation Method 1
a recirculation conduit (8) which is located downstream of the gas stream preheater (5) and leads to the gas stream feed conduit (9) and a connecting conduit (10) which is located downstream of the gas stream preheater (5) and leads to the steam reformer (3), wherein the flow of the gas stream which has been heated in the gas stream preheater (5) through the recirculation conduit (8) and thus also through the connecting conduit (10) which is located downstream of the gas stream preheater (5) and leads to the steam reformer (3) can be regulated
Data Source
AI summary
An apparatus for producing ammonia or hydrogen may include a) a gas stream feed conduit having a connecting conduit to a steam reformer with a waste heat section; b) a heat exchanger downstream of the gas stream feed conduit; c) a gas stream preheater downstream of the heat exchanger; d) a recirculation conduit which is located downstream of the gas stream preheater and leads to the gas stream feed conduit or, upstream of the heat exchanger, to the connecting conduit; and e) the steam reformer with the waste heat section, where the waste heat section may be in thermal contact with the gas stream preheater and the flow of the gas stream which has been heated in the gas stream preheater through the recirculation conduit can be regulated. A process for producing ammonia or hydrogen may employ such an apparatus.