Cracked Gas Precooling Stage Using Absorption Cooling
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Solution Overview
Problem
The compression of cracked gas in hydrocarbon feedstock cracking processes is energy-intensive, with expensive turbine-driven centrifugal compressors being bottlenecks in steam cracker plants, and existing methods do not efficiently utilize available heat sources for precooling.
Innovation Solution
A compression stage that includes a liquid separator for separating liquid components from gaseous components, a compressor, and a gas precooler using an absorption cooling system to precool the cracked gas before compression, utilizing available heat sources such as quench water to reduce compressor workload and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If cracked gas is compressed directly without precooling, then the compression process is simpler, but the compressor work and energy consumption increase significantly
Solution Approach 1:
The gas precooler is positioned before the compressor to precool the cracked gas before compression. This preliminary cooling action reduces the temperature and volume of the gas entering the compressor, thereby reducing the compressor work required. The absorption cooling system generates cooling fluid using available heat sources (quench water, cooling water) to perform this precooling action in advance of compression.
2Productivity
If a larger compressor is used to handle hot cracked gas, then the compression capacity is sufficient, but the equipment cost and plant investment increase
Solution Approach 1:
By precooling the cracked gas before it enters the compressor, the gas volume is reduced, allowing a smaller compressor to achieve the same compression capacity. This preliminary temperature reduction enables the use of more compact, less expensive compressor equipment while maintaining the required productivity.
3Loss of energy
If conventional cooling systems are used, then the cooling function is provided, but available heat sources are not efficiently utilized
Solution Approach 1:
The system converts waste heat from quench water and cooling water into useful cooling capacity. The absorption cooling system uses these available heat sources to generate cooling fluid, which is then used by the gas precooler to cool the cracked gas. This transforms what would otherwise be wasted thermal energy into a beneficial cooling resource, significantly improving heat source utilization efficiency.
Solution Approach 2:
The absorption cooling system is self-sufficient, generating its own cooling fluid using available process heat sources rather than requiring external utility systems. The system uses quench water and cooling water from the cracking process itself to drive the absorption cooling cycle, making the cooling function self-service and reducing dependency on external utilities.
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 reduces the overall workload on compressors, saves approximately 3 MW of mechanical power, and allows for a less expensive compressor design with reduced fouling, while efficiently using available heat sources, thereby enhancing the efficiency of the compression process.
Implementation Method 1
The gas precooling means comprises a heat exchanging means and an absorption cooling means, wherein the heat exchanging means is cooled by a second cooling fluid from the absorption cooling means
Implementation Method 2
the heat exchanging means is cooled by a second cooling fluid from the absorption cooling means
Implementation Method 3
a liquid separating means or a liquid separator for separating liquid components from gaseous components of a cracked gas
Implementation Method 4
a compressor connected to the liquid separating means or the liquid separator
Implementation Method 5
The compression is typically performed by a turbine-driven centrifugal compressor
Data Source
AI summary
A compression stage for the compression of cracked gas, the compression stage comprising a liquid separating means for separating liquid components from gaseous components of a cracked gas, a compressor connected to the liquid separating means, a gas cooling means connected to the compressor for cooling the compressed gas from the compressor, wherein the gas cooling means are cooled by a first cooling fluid from the cooling fluid source. The stage further comprises gas precooling means connected to the liquid separating means cracked gas, having an inlet for receiving the cracked gas.