Nitric Acid Plant Tail Gas Heating Heat Exchanger
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Solution Overview
Problem
Modern nitric acid production plants face challenges in optimizing energy usage and reducing nitrogen oxides vented into the atmosphere, particularly in the dual pressure process where higher acid concentrations and absorption rates are desired while minimizing environmental impact.
Innovation Solution
The plant design incorporates a tail gas treatment system with a heat exchanger positioned downstream of the steam circuit heat exchanger and upstream of the gas outlet, heating the tail gas to a temperature greater than 460°C, which increases kinetic energy and enhances energy efficiency in driving compressors, and allows for more effective nitrogen oxides conversion and purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the tail gas is heated to higher temperature to increase kinetic energy for driving compressors, then energy efficiency is improved, but additional energy input is required which increases operational expenses
Solution Approach 1:
The patent combines the tail gas heating function with the existing steam circuit heat exchanger, merging two thermal processing functions into a single piece of equipment. The tail gas is heated using waste heat from the steam circuit, eliminating the need for separate auxiliary heating systems and natural gas consumption, thereby improving energy efficiency without increasing operational expenses
Solution Approach 2:
The patent converts the waste heat from the steam circuit into a beneficial resource for heating tail gas. By utilizing what would otherwise be wasted thermal energy, the system increases kinetic energy of tail gas for compressor drive without requiring additional energy input, thus improving energy efficiency while avoiding increased operational costs
2Object-generated harmful factors
If a separate auxiliary heating system is installed for NOx abatement, then nitrogen oxides conversion is improved, but capital expenses and device complexity increase
Solution Approach 1:
The patent merges the tail gas heating function with the steam circuit heat exchanger, eliminating the need for separate auxiliary heating equipment. This integration achieves effective NOx conversion through heated tail gas while avoiding additional capital expenses and device complexity that would result from installing independent heating systems
Solution Approach 2:
The steam circuit heat exchanger is designed to serve multiple functions: steam generation and tail gas heating. This multi-functionality allows the system to achieve nitrogen oxides conversion without requiring dedicated auxiliary heating equipment, thereby reducing capital expenses and maintaining simple device architecture
3Object-generated harmful factors
If natural gas is used for heating tail gas in NOx abatement, then nitrogen oxides conversion is improved, but operational expenses increase
Solution Approach 1:
The patent converts waste heat from the steam circuit into a useful resource for tail gas heating and NOx abatement. This eliminates the need for natural gas consumption in the heating process, achieving effective nitrogen oxides conversion while avoiding the increased operational expenses that would result from burning fossil fuels
Solution Approach 2:
The system uses its own waste heat resources to fulfill the heating requirement for NOx abatement. The steam circuit's thermal energy serves dual purposes, and the tail gas heating is achieved through internal heat recovery rather than external fuel consumption, thereby reducing operational expenses
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 approach results in improved energy efficiency, reduced nitrogen oxides emissions, and lower capital and operational expenses by increasing the energy available from expanding tail gas, enabling higher energy recovery and lower emissions without the need for auxiliary natural gas in the NOx abatement system.
Implementation Method 1
a heat exchanger configured to receive heat from the burner gas stream... heating the tail gas to a temperature greater than 460°C
Implementation Method 2
a steam circuit heat exchanger configured to transfer heat from the burner gas stream to the steam circuit so as to generate superheated steam
Implementation Method 3
a condensation section configured to condense the cooled burner gas so as to form a nitric acid solution and an uncondensed nitrogen oxides gas stream
Data Source
AI summary
Disclosed is a dual pressure plant for the production of nitric acid on the basis of the oxidation of ammonia. The plant comprises a reactor configured to produce a burner gas stream; a gas cooling section configured to form a cooled burner gas; a condensation section configured to form an aqueous nitric acid condensate and an uncondensed nitrogen oxides gas stream; an absorption section configured to produce raw nitric acid and a tail gas; and a tail gas treatment system configured to form a purified tail gas. In a tail gas heating section a further heat exchanger configured to receive heat from the burner gas stream, said further heat exchanger being positioned relatively close to the reactor.