Oily Mill Scale Thermal Storage with Direct Heat Exchange
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Solution Overview
Problem
Existing thermal energy storage systems face challenges in efficiently utilizing waste materials like oily mill scale from steelworks due to high costs and integration complexities, particularly in achieving high thermal conductivity and capacity, while also needing to manage fluctuating waste heat sources effectively.
Innovation Solution
A novel thermal energy storage system utilizing oily mill scale with direct contact between heat exchanger surfaces and the mill scale, integrated within a concrete casing, which enhances thermal conductivity and capacity, and includes a filter for moisture reduction and efficient heat discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If oily mill scale sludge is used as thermal energy storage medium, then thermal capacity and conductivity are improved, but water content reduction and material treatment complexity increase
Solution Approach 1:
The system uses the oily mill scale sludge's own properties (high iron content, thermal conductivity) to serve as the thermal storage medium, eliminating the need for complex external treatment processes. The sludge is directly utilized after minimal processing, allowing it to self-function as the heat storage material while reducing water content through controlled heating.
Solution Approach 2:
The system changes the physical parameters of the oily mill scale sludge by controlling water content reduction through heating to optimal ranges (15-30% or 10-20%), thereby transforming the material into an effective thermal storage medium with enhanced thermal properties and appropriate moisture levels for efficient heat storage and retrieval.
2Use of energy by moving object
If high temperature thermal energy storage is implemented, then energy efficiency is improved, but investment requirements and system complexity increase
Solution Approach 1:
The system converts waste heat from steelmaking operations, which would otherwise be discarded or require complex recovery systems, into useful thermal energy for storage and subsequent utilization. By utilizing the existing high-temperature waste heat streams to charge the thermal storage system, the invention transforms a harmful waste product into a beneficial resource, improving energy efficiency while avoiding additional complex high-temperature generation equipment.
3Loss of energy
If waste heat from steelmaking processes is utilized, then energy recovery is improved, but integration complexity and operational challenges increase
Solution Approach 1:
The thermal energy storage system designed with oily mill scale sludge serves multiple functions: it stores waste heat from various steelmaking processes (BOF, LF, EAF), provides process heat for sludge dewatering, and can supply thermal energy to district heating networks or industrial processes. This multi-functionality simplifies integration by allowing a single system to handle multiple energy recovery and utilization tasks that would otherwise require separate systems.
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 system achieves high thermal energy storage capacity and efficiency, reducing water content in mill scale, preserving its conductivity, and enabling sustainable energy management with versatile applications, including electricity generation and district heating.
Implementation Method 1
Thermal energy storage of sensible heat using liquid and solid materials is well-established in the field
Implementation Method 2
Our research has identified wastes, derived from the very process they are transforming, as the optimal material for thermal energy accumulation due to their high conductivity, capacity
Implementation Method 3
The heat exchanger exchange surfaces, supplying heat or electrical direct heating elements, are directly immersed in the oily mill scale, establishing direct contact between the material of the heat exchangers or electrical heaters and the accumulator material
Implementation Method 4
The energy storage accumulation, with operating temperatures reaching up to 450°C, significantly reduces the water content in oily sludges in each cycle
Data Source
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AI summary
A hybrid thermal storage system (1) comprises one or more sections (2). Each section is encased in concrete (21) and includes integrated pipe bundles (22), a thermal insulation envelope (23), and an opening (24) for manipulating the thermal energy storage material (3) and heat sources (4). The section is filled with oily mill scale waste from steelworks (3). Charging systems (4) consist of either plate or spiral pipe systems (41), centrally positioned within the heat storage material (3) for waste heat flows, or direct electric heating elements (42) for electrical energy surpluses. On the top of opening is installed drum (5) with filter (51) for evaporation of water residuals and exhaust to atmosphere (52). Thermal sensors are placed in various zones: within the concrete casing (T1, T2, T3, T4), in the storage material (T5, T6), at the charging loop (T7, T8) and discharging loop (T9, T10), of thermal energy flows, and at the source of thermal energy from direct electric heating. Optimization is achieved through a control system (6) that gathers data from thermal sensors and external systems. This system evaluates the optimal economic conditions for the operation of thermal energy storage and manages the process of discharging and charging the accumulator with the hybrid possibility of operation, involving both waste heat flows (41) and electrical energy surpluses (42). These pipe bundles may have various geometries. Sludge-like sediments are placed in individual sections without any modification, serving as the primary material for storing thermal energy with high thermal capacity and conductivity. Heat sources, either plate or spiral pipe systems, or resistive electric elements for storing surplus electrical energy into heat, are immersed in the sludges in the sections, or a hybrid combination of both. The secondary material is the concrete casing of the sections, which is enveloped in an insulating layer to prevent heat leakage. The hybrid accumulator is complemented by a control system that, based on data from thermal sensors in the sections, environmental data, forecast, simulation, and energy consumption requirements, manages the process of discharging and charging the accumulator. Individual sections can operate at different thermal levels, effectively combining high-temperature storage with low-temperature storage.