Modernization of a Tube Furnace as Part of Zero-Waste Practice

Abstract

Modern research laboratories are constantly evolving to meet the growing demands for precision, quality, and flexibility in scientific work. The modernization of existing experimental test benches plays a crucial role in improving efficiency, optimizing processes, and ensuring operational safety. This requires updates to their design, experimental methods, data collection, and results recording—all of which provide the foundation for developing new research concepts. An increasing number of innovations are now guided by the principle of minimizing environmental impact. In line with this approach, an innovative modernization of a tube furnace research station was carried out, based on the concepts of sustainable development and the zero-waste philosophy. To enable thermogravimetric analyses of coffee waste, a previously incomplete tube furnace was refurbished using recycled components. The primary objective was to expand the research capabilities of the existing workstation. As part of the modernization, three indicators of reuse efficiency were calculated: the quantitative indicator W_re-use, the mass indicator $W_{re\text{-}use}^{mass}$, and the cost indicator $W_{re\text{-}use}^{value}$. A quantitative index of 78% and a mass index of approximately 76% were achieved, while the economic value of the recovered components accounted for 11% of the total value of the revitalized research station. This strategy significantly reduced waste generation, carbon dioxide emissions, and the consumption of primary raw materials.

1. Introduction

In response to growing environmental challenges, green technologies and the zero-waste concept play a pivotal role in advancing sustainable development. Green technologies encompass innovative solutions aimed at minimizing the negative impacts of human activity on ecosystems, including raw material recycling, renewable energy use, and efficient resource management. The zero-waste philosophy, in turn, seeks to eliminate waste through reuse, recycling, and upcycling, thereby supporting the circular economy and reducing dependence on primary raw materials.

Modern technological innovations increasingly make use of waste materials to develop new functional products. Examples include the construction of 3D printers from electronic waste [1], modular hospital buildings made from recycled components such as the modular adaptable convertible [2], and the recovery of rare earth metals from electronic waste for reuse in high-tech industries [3]. Cheng et al. present the potential for recovering rare earth metals from coal-based solid wastes. Their comprehensive study also explores other applications of coal-based solid wastes in areas such as the construction industry, metallurgy, and the development of functional materials [4]. Even food industry by-products can be repurposed—for instance, through the production of detergents from waste frying oil [5].

The integration of modern engineering solutions with sustainable resource management principles underpins ecological transformation and the transition to a low-carbon economy. In line with these challenges and the increasing need to adopt pro-environmental strategies, a laboratory tube furnace system was modernized with the incorporation of recycled components. This approach not only reduced waste but also enhanced functionality and improved the overall efficiency of the revitalized system.

This project reflects a global trend toward the adoption of green technologies in laboratory and scientific practice, underscoring the importance of innovative resource management, particularly in the development of research equipment. Unlike other examples—such as modular architecture or consumer products—this modernization of a tube furnace is distinguished by its direct integration of reuse strategies into the research process itself, rather than restricting them to implementation or design stages.

Overview of Thermal Methods

Thermal analysis is one of the most important techniques for investigating the thermal properties of materials, fuels, biomass, sewage sludge, and municipal waste. It enables the assessment of material behavior under varying temperature conditions. The parameters determined through such analyses include decomposition temperatures, heat of combustion, gas emissions, and other related characteristics [6,7]. These data are essential for the design of thermal processing and conversion systems adapted to the specific properties of different materials [8].

The versatility of thermal analysis allows for its application across a wide range of industrial sectors. In the chemical industry, it supports the optimization of synthesis processes, where decomposition rates and crystallization kinetics influence reaction efficiency and product quality. In the pharmaceutical sector, thermal analysis is used to develop stable drug formulations, particularly for temperature-sensitive active substances or those prone to undesirable polymorphic transformations. In plastics and metallurgy, it facilitates raw material selection, the optimization of manufacturing parameters, and detailed quality control of final products. In the food industry, it assists in evaluating product shelf life and in designing preservation and storage processes [6].

High-temperature processes such as combustion and thermal conversion are typically studied using instruments including thermogravimetric analyzers, differential scanning calorimeters, thermomechanical analyzers, dynamic mechanical analyzers, and tube furnaces. The design of these devices enables experiments under a wide variety of conditions, including protective, oxidizing, and reducing atmospheres, making them highly versatile research tools. Their precision and reliability not only enhance the understanding of material behavior but also support the development of innovative processing technologies. The ability to adjust operating parameters—such as temperature, process duration, and atmosphere type—is particularly valuable, as it allows researchers to optimize experiments for specific objectives. In addition, the identification of thermal decomposition products and detailed characterization facilitate the implementation of appropriate protective measures [7,8]. Thermal analysis also plays a key role in sustainable waste management by providing essential data for the development of recycling and energy recovery technologies [7].

Among the most widely used thermal analysis techniques is differential scanning calorimetry (DSC), which measures heat flow into or out of a sample, enabling the determination of parameters such as phase transition enthalpy and melting temperature. Thermogravimetric analysis (TGA) monitors changes in sample mass during heating or cooling and is critical for evaluating volatile content and thermal decomposition products. Other important methods include thermomechanical analysis (TMA), which records dimensional changes and allows the determination of thermal expansion coefficients, and dynamic mechanical analysis (DMA), which examines the viscoelastic properties of materials—essential for studying polymers, rubbers, and other elastomers [6,9].

Table 1. Overview of thermal analysis techniques.

Technique	Measured Property	Key Applications
DSC Differential Scanning Calorimetry	Enthalpy changes, specific heat capacity, phase transition temperatures (melting, crystallization, polymorphic transitions, glass transition), transformation kinetics	Purity analysis, polymorph identification, thermal stability analysis, investigation of polymer melting and crystallization processes, analysis of pharmaceuticals and food products [6,9,10]
TGA Thermogravimetric Analysis	Sample mass changes as a function of temperature or time, thermal decomposition, quantitative composition, thermal stability	Moisture content determination, analysis of thermal decomposition of polymers, composition analysis of mixtures, thermal stability testing of pharmaceuticals and construction materials [11]
TMA Thermomechanical Analysis	Dimensional changes of the sample in response to temperature (thermal expansion, shrinkage), elastic modulus, viscosity, stress relaxation	Thermal expansion studies of metals, polymers, and ceramics, analysis of material shrinkage, measurement of elastic modulus and viscosity [12]
DMA Dynamic Mechanical Analysis	Dynamic elastic modulus, damping factor, dynamic viscosity, stress relaxation under dynamic conditions	Investigation of elastic modulus and viscoelastic properties of polymers, composites, and elastomers; characterization of plastics; stress relaxation analysis; measurement of dynamic elastic modulus and damping factor [12]
DEA Dielectric Analysis	Changes in the dielectric properties of a material (dielectric constant, dielectric loss) as a function of temperature or frequency	Investigation of dielectric properties of polymers, ceramics, and composites; analysis of polarization and relaxation processes; monitoring of resin curing [13]
EGA Evolved Gas Analysis	Analysis of gases released from the sample during heating, identification of thermal decomposition products	Thermal decomposition studies of polymers, identification of degradation products, analysis of gases released during combustion [14]
TM Thermal Microscopy	Morphological changes of the sample (crystalline structure, phase transitions) as a function of temperature, observation of processes occurring during heating	Observation of melting and crystallization of polymers, analysis of phase transitions in metals and alloys, investigation of crystal morphology [15]
FTIR Fourier Transform Infrared Spectroscopy	Changes in the infrared spectrum of the material as a function of temperature, identification of functional groups, analysis of chemical composition	Investigation of structural changes in polymers, identification of thermal decomposition products, chemical composition analysis [16]
RS Raman Spectroscopy	Changes in the Raman spectrum of the material as a function of temperature, identification of functional groups, analysis of molecular structure	Investigation of structural changes in polymers, identification of functional groups, chemical composition analysis [17]
TL Thermoluminescence	Light emitted by the material after prior irradiation, temperature dependence of light emission	Study of luminescent materials, archaeological dating, radiation dosimetry [18]
MK Microcalorimetry	Heat released or absorbed during chemical and biological processes, enthalpy changes of reactions	Investigation of chemical reactions, biological processes (e.g., cellular metabolism), and intermolecular interactions [19]
ITC Isothermal Titration Calorimetry	Heat released or absorbed during interactions between two substances, reaction enthalpy, equilibrium constant, stoichiometry	Investigation of protein–ligand, enzyme–substrate, and DNA–drug interactions; analysis of association and dissociation processes [19]
MDSC Modulated Differential Scanning Calorimetry	Reversible and irreversible heat, specific heat, phase transition temperatures	Investigation of complex thermal transitions, analysis of structural relaxation, identification of processes occurring during glass transition [10]
DTA Differential Thermal Analysis	Temperature difference between the sample and the reference, phase transition temperatures	Investigation of phase transitions in minerals and ceramics, analysis of mixture composition [6]
DTMA Dynamic Thermomechanical Analysis	Dynamic elastic modulus, damping factor, and dynamic viscosity as a function of temperature and frequency	Investigation of viscoelastic properties of materials, stress relaxation analysis, measurement of dynamic elastic modulus and damping factor [12]
DRS Broadband Dielectric Spectroscopy	Changes in the dielectric properties of a material over a wide range of temperatures and frequencies	Investigation of molecular dynamics, relaxation processes, and ionic conductivity [13]
TSDC Thermally Stimulated Depolarization Currents	Depolarization currents as a function of temperature, activation energy of relaxation processes	Investigation of defects in dielectrics, analysis of relaxation processes [13]
IRT Infrared Thermography	Temperature distribution on the surface of an object, infrared radiation emission	Thermal diagnostics in industry, medicine, and construction [20]

provides an overview of the fundamental thermal analysis techniques.

All applications of the thermal analysis techniques summarized in Table 1 support the prediction of material behavior under operational conditions. Such analyses provide a deeper understanding not only of the temperatures at which a substance melts or decomposes but also of the corresponding decomposition pathways and by-products. These insights, in turn, facilitate more effective manufacturing process planning, the design of materials with specific properties, and the enhancement of product quality and safety [6].

Table 2. Overview of selected models and specifications of instruments used in thermal analysis.

Technique	Example Type and Model of Instrument	Brief Specification
DSC Differential Scanning Calorimetry	Thermal Analysis System DSC 3, Mettler Toledo	Wide temperature range, high sensitivity and measurement precision, and intuitive data analysis software; used for studying phase transitions, specific heat, reaction kinetics, and thermal stability of materials [21]
TGA Thermogravimetric Analysis	TGA 2, Mettler Toledo	High mass measurement precision, wide temperature range, and the ability to couple with other techniques such as DSC or MS; enables the study of thermal decomposition, quantitative composition, and thermal stability of materials [22]
TMA Thermomechanical Analysis	TMA 450, TA Instruments	Wide range of forces and temperatures, high resolution in dimensional change measurements, and intuitive data analysis software; enables investigation of thermal expansion, creep, stress relaxation, and elastic modulus of materials [23]
DMA Dynamic Mechanical Analysis	RSA-G2, TA Instruments	Wide range of frequencies and oscillation amplitudes, high sensitivity in measuring modulus and damping; capable of operating in various deformation modes; enables the study of viscoelastic properties, stress relaxation analysis, and measurement of dynamic elastic modulus [24]
DEA Dielectric Analysis	DEA 288 Epsilon, NETZSCH	Wide temperature and frequency range, high precision in dielectric property measurements, capability to conduct tests under various atmospheric conditions; enables the study of polarization and relaxation processes, ionic conductivity, and monitoring of resin curing [25]
EGA Evolved Gas Analysis	EGA system coupled with a mass spectrometer NETZSCH	Enables real-time analysis of gases released from the sample during heating, allowing identification of thermal decomposition products, chemical composition analysis, and investigation of reaction mechanisms [26]
TM Thermal Microscopy	Thermal Microscope Linkam	Enables observation of morphological changes in the sample as a function of temperature; microscopes equipped with precise heating stages, imaging systems, and data analysis software [27]
FTIR Fourier Transform Infrared Spectroscopy	Nicolet iS Series FTIR Spectrometer, Thermo Fisher Scientific	High spectral resolution, broad spectral range, and the ability to couple with other techniques such as microscopy or GC; enables identification of functional groups, chemical composition analysis, and investigation of structural changes in materials [28]
RS Raman Spectroscopy	inVia Series Raman Spectrometer, Renishaw	High sensitivity, measurement precision, and spatial mapping capability; enables chemical composition identification, molecular structure analysis, and investigation of intermolecular interactions [29]
TL Thermoluminescence	Czytnik TL/OSL Risø National Laboratory	Used for measuring thermoluminescence and optically stimulated luminescence (OSL); enables applications such as archaeological dating, radiation dosimetry, and the study of luminescent materials [30]
TG Thermography	Flir A-Series thermal imaging camera Flir	Enables measurement and imaging of temperature distribution on object surfaces; used for thermal diagnostics in industry, medicine, and construction [31]
MK Microcalorimetry	Microcalorimeter TAM III, TA Instruments	High sensitivity and precision in measuring heat released or absorbed during chemical and biological processes; enables studies of chemical reactions, metabolic processes, and intermolecular interactions [32]
ITC Isothermal Titration Calorimetry	MicroCal PEAQ, Malvern Panalytical	Heat released or absorbed during interactions between two substances, reaction enthalpy, equilibrium constant, stoichiometry [33]
MDSC Modulated Differential Scanning Calorimetry	Q2000 Series DSC, TA Instruments	Precise heat measurement, temperature modulation, separation of reversible and irreversible heat; specific heat capacity, phase transition temperatures, structural relaxation [34]
DTA Differential Thermal Analysis	STA 449 F3 Jupiter, NETZSCH	High sensitivity, wide temperature range, capability to couple with MS; measurement of temperature difference between the sample and the reference, phase transition temperatures [35]
DTMA Dynamic Thermomechanical Analysis	Eplexor DMA, NETZSCH	Wide range of forces and temperatures, precise measurement of mechanical properties as a function of temperature and frequency; dynamic elastic modulus, damping factor, dynamic viscosity, stress relaxation [36]
DRS Broadband Dielectric Spectroscopy	Concept 80, Novocontrol Technologies	Wide frequency range, precise measurement of dielectric properties; changes in dielectric properties (dielectric constant, dielectric loss) over a wide range of temperatures and frequencies [37]
TSDC Thermally Stimulated Depolarization Currents	TSC/TSDC, SystemPhysTech GmbH	Precise measurement of depolarization currents, analysis of relaxation processes; depolarization currents as a function of temperature, activation energy of relaxation processes [38]
IRT Infrared Thermography	A-Series, FLIR Systems	High thermal image resolution, wide temperature range, ability to measure temperature from a long distance; temperature distribution on the surface of an object, infrared radiation emission [31]

presents an overview of the specialized instruments employed for each technique.

Tube furnaces are fundamental components in the design of thermal analysis instruments. They are also widely used in research laboratories as standalone heating and measurement systems, particularly for processes that require precise temperature control, such as material synthesis, calcination, and sintering. Their primary function is to provide uniform heating of samples under controlled thermal conditions, ensuring the accuracy and reproducibility of experimental results. The working tube of the furnace, fabricated from high-temperature-resistant materials, serves as the heating chamber, provides effective thermal insulation, and protects the heating elements from direct contact with samples.

The choice of heating elements depends on the specific requirements of the process. The most commonly used types include Kanthal (Sandvik Materials Technology, Sandviken, Sweden) spirals, molybdenum disilicide (MoSi₂) elements, and graphite heaters [39].

Laboratory tube furnaces are available in a variety of designs, each serving a wide range of applications. In standard processes, single-zone furnaces provide uniform temperature distribution along the entire length of the combustion chamber. Multi-zone furnaces allow the creation of temperature gradients, making them particularly suitable for advanced materials research. For dynamic thermal processes, split-tube furnaces are used, allowing rapid sample access and cooling. Rotary tube furnaces, which rotate the sample load, ensure uniform heating and are especially advantageous in material synthesis [40].

In order to meet the requirements of modern research laboratories, a comprehensive evaluation of the existing system’s design and functionality was undertaken. Before modernization, the setup featured a vertically oriented tube furnace, with samples inserted from above via a basket suspended beneath the balance.

A major limitation restricting the system’s potential was the absence of furnace rotation, which significantly reduced the versatility of the research station. Another drawback, identified during the thermal analysis of compacted waste, concerned the sample feeding system. During experiments, the feeding mechanism often caught on or pressed against the inner walls of the tube furnace and the balance insulation, affecting measurement accuracy. Additionally, solid samples often passed through the perforated bottom of the basket into the combustion chamber during incineration, resulting in inaccurate mass measurements. The system was also incapable of accommodating liquid or non-compacted samples. Moreover, the inability to adjust the setup’s position restricted its potential applications, reducing both versatility and flexibility across different research scenarios. Taken together, these limitations directly impacted the overall functionality of the system.

The aim of the proposed modernization was to enhance the research capabilities of the station while adhering to the principles of sustainable development and the zero-waste philosophy, thereby increasing its versatility and aligning it more closely with the requirements of modern laboratory research.

2. Methodology

The modifications to the long-operating research device (RST 20x200/100M/spec CZYLOK SP. Z O.O., Jastrzębie-Zdrój, Poland) were motivated by the need to adapt the station for a wider range of experimental procedures. The previous configuration of the tube furnace, limited to a single fixed position, was inadequate for more advanced research applications.

The scope of the modernization of the laboratory tube furnace (RST 20x200/100M/spec) included an evaluation of the original structural configuration, the development of a furnace rotation mechanism compliant with mechanical strength requirements, and the design of a sample feeding system, including a stand that enables sample insertion when the furnace is operated in an inverted orientation.

The primary stages of the modernization process, together with the key tasks and outcomes for each stage, are summarized in

Table 3. Stages of the modernization of the tube furnace research station.

Stage	Stage Description	Results
Stage 1 Modernization of the support frame	Selection of a support frame ensuring furnace stability in various positions during operation; mounting of the furnace on the selected frame without the rotary element, in a fixed position	The support frame ensures the load-bearing capacity for the furnace’s own weight, maintains its stability, and allows for vertical position adjustment
Stage 2 Installation of the furnace rotation mechanism	Analysis and selection of the furnace rotation method and the mechanism to perform the task; determination of additional components (steel plate dimensions, thickness, bolts, holes, and clamps); dimensioning and integration of the selected rotation mechanism (turntable) with the support frame	Fabrication of mounting components for attaching the rotary mechanism to the support frame, assembly, and verification of the rotational capability of the mechanism without the furnace load
Stage 2 Installation of the rotary mechanism for the furnace	Installation of the laboratory furnace onto the rotary component of the support frame, followed by verification of the stability of its mounting and overall functionality	Correct installation of the laboratory furnace, stable positioning maintained at every furnace orientation
Stage 4 Weighing the platform for the measurement system	Development of the concept for a balance table platform with adjustable positioning to accommodate specific research requirements	Use of a scissor lift as the main base of the balance table, execution of lifting tests, adjustment, and leveling of the weighing system
Stage 5 Design of the sample insertion stand for the furnace	Conceptual design of the sample insertion stand, material selection, and fabrication of the stand	Execution of tests for the sample feeding system, combustion process conducted using the newly implemented sample insertion setup

.

The modernization of the research station (RST 20x200/100M/spec) consisted of a series of stages, summarized in Table 3 together with the expected outcomes of each action. All steps were carried out systematically, taking into account the structural characteristics of the tube furnace and the sequential requirements for integrating new components. The modernization plan is outlined below:

• Analysis of the current technical condition of the RST 20x200/100M/spec research station.
• Disassembly of existing components.
• Installation of a new support structure.
• Selection and installation of the furnace rotation mechanism.
• Selection and installation of the balance table system.
• Fabrication of a rod-type device for sample insertion into the furnace.
• Testing of the modernized research station, including thermal analysis in the inverted configuration.

2.1. Structure of the Research Station Before Modernization

Figure 1 presents a simplified schematic of the research station equipped with a tube furnace system, highlighting its principal components.

The main component of the research station was the tube furnace (7) (Figure 1), which featured an electric heating system for raising sample temperatures and was used to investigate the physical and chemical properties of compacted waste. The furnace unit (7), together with the laboratory balance (4), was mounted on a support frame (2) and powered via a control and power unit (1). Located in the department’s laboratory, the system played a crucial role in thermal analysis applications. However, its functionality required improvement, particularly regarding adjustable positioning and adaptation to more advanced research needs.

The new prototype of the research station was designed to support a wide range of thermal studies under diverse conditions, significantly enhancing its previous functionality. The following sections provide descriptions, dimensions, and technical drawings of the key components identified during the inventory of the experimental setup.

The most critical component of the RST 20x200/100M/spec research station is the tube furnace module—illustrated in Figure 2—whose construction utilizes modern materials to ensure both durability and high performance. The heating elements are made of Kanthal A1 alloy, providing uniform heat distribution throughout the furnace chamber. The combustion tube is made of heat-resistant H25N20S2 stainless steel, allowing operation at temperatures up to 1200 °C while maintaining corrosion resistance.

The outer surface of the furnace is carefully insulated with ceramic fiber-based rings, minimizing heat loss and stabilizing the internal temperature. The entire furnace casing is constructed from high-quality stainless steel, providing mechanical robustness and long-term reliability [41]. Figure 2 presents the basic dimensions of the tube furnace module and its individual components in top, side, and cross-sectional views.

Figure 3 shows the furnace’s combustion tube in side and top views, along with its dimensions. The tube has a length of l = 485 mm, an internal diameter of d_i = 32.0 mm, and a wall thickness of d_r = 3.0 mm, and is constructed from heat-resistant stainless steel. This component plays a fundamental role in the testing process, ensuring stable and controlled thermal conditions.

Another essential component of the RST 20x200/100M/spec system is the control and power supply module, which delivers electrical power and manages the operation of the device. The system comprises a PID temperature controller, a main switch, overcurrent protection, an electronic power control unit, and a communication interface for computer-based operation. The MRT-4 programmable controller enables temperature measurement, control, and programming within the furnace, allowing users to define detailed operating programs of up to ten segments. Each segment can be configured with parameters such as the target temperature, ramp time to reach the setpoint, and dwell time.

Thanks to its built-in autotuning function, the controller automatically adjusts the PID control parameters, ensuring optimal furnace performance and stable thermal processes [41]. Figure 4 illustrates the control and power supply module, which is responsible for the precise regulation of the tube furnace operation and the provision of power to the components of the research station.

The final component of the RST 20x200/100M/spec tube furnace research station is a laboratory balance with a precision of 0.001 g. Its primary function is to determine the mass of samples before, during, and after experiments, enabling the analysis of mass loss during the thermal decomposition of the investigated material. As shown in Figure 1, the balance’s position and the method of sample insertion were established prior to system modernization. The balance was mounted above the furnace on a shelf insulated with thermal protection material, through which the sample feeding mechanism passes to deliver the sample into the furnace.

The sample feeding system consists of a cylindrical basket, shaped as a vertical cylinder with an outer diameter of d_kZ = 24.89 mm and a height of h_k = 42.12 mm. The bottom of the basket is perforated with 21 holes, each with a diameter of d_o = 2.9 mm, while the wall thickness is d_kS = 2.0 mm. The sidewall contains four elliptical openings with major and minor diameters of 25.45 mm and 6.0 mm, respectively.

During experiments, the basket was suspended from a steel chain beneath the balance and precisely lowered to the midpoint of the combustion chamber within the tube furnace. The sample was inserted axially from the top, which can occasionally cause measurement inaccuracies. These errors primarily occurred when the sample feeding element contacts the thermal insulation cover, affecting the reliability of mass readings.

The geometry of the basket also had a significant impact on measurement quality and reliability. Its design restricts the free flow of oxygen to the sample and limits the removal of process gases during experiments. A geometrical analysis of the sample feeding components—specifically, the ratio of the basket’s external cross-sectional area to the internal cross-sectional area of the combustion chamber—revealed that it reaches nearly 85%, substantially limiting the oxidant supply to the material during thermal treatment.

Although functional, the initial configuration of the tube furnace test rig exhibited significant limitations that hindered its use in advanced research. The lack of furnace rotation, challenges in accurate sample feeding, and restrictions on the types of analyzable materials reduced both the flexibility and reliability of the system. These shortcomings underscored the necessity for modernization aimed at enhancing the versatility, precision, and sustainability of the setup. The following section presents the scope and outcomes of the implemented modifications.

2.2. Modernization of the Research Station

The modernization of the research station began with the replacement of the support frame for the entire experimental system. The stand, a critical structural component supporting the tube furnace unit, was reused from previously used equipment. Made of durable materials, the frame provides high resistance to mechanical loads and vibrations.

The stand consists of several elements: a dual-column main frame, a horizontal mounting plate, and a mobile base with wheels. The wheels are equipped with locking mechanisms, allowing the research station to be easily repositioned within the laboratory for integration with auxiliary instrumentation required by specific research procedures. The locking system ensures stable equipment positioning, eliminating the risk of unintended movement during operation.

The adjustable columns, serving as vertical supports, permit precise height adjustment of the entire experimental system, enhancing flexibility and enabling ergonomic integration with various research configurations. A schematic of the stand, including dimensional details, is presented in Figure 5.

The height adjustment mechanism of the stand allows stepwise vertical positioning of the furnace within a range of 1.2 m to 1.5 m, in 5.0 cm increments. The stand’s design also accommodates the installation of additional components, such as measurement sensors, sample holders, or auxiliary research equipment. Its robust base and precisely engineered connections ensure safe and stable support of the furnace in various positions.

Based on the conducted analysis, a bearing-based rotary mechanism was selected for implementation. For this purpose, a previously acquired turntable from laboratory storage was utilized, together with appropriate mounting bolts.

The sample feeding unit (stand) was constructed using various reclaimed steel components, also sourced from the available inventory. The only newly acquired components incorporated into the modernization of the research station were the rotameter and spirit levels.

Bearing turntables are mechanisms that allow mounted components to rotate around their own axis. They are widely used in mechanical systems, automation, and specialized constructions, where their primary function is to enhance the functionality and positional flexibility of structural elements. Detailed dimensions of the rotary component used are presented in Figure 6.

Figure 7 illustrates the method of mounting the rotating mechanism (turntable) onto the stand structure, while Figure 8 depicts the installation of the rotating element on the tube furnace casing, ensuring a stable connection between the two components.

Figure 5, Figure 6, Figure 7 and Figure 8 show the assembly of the rotating mechanism on the supporting frame and the tube furnace casing, ensuring a secure integration of all components. This configuration allows the furnace to be reoriented to any position, both horizontally and vertically. In the downward orientation, samples can be loaded onto a rigid stand placed on the balance from below, while the upward orientation allows sample loading from the top, suspended beneath the balance above the furnace system, as in the original setup. The horizontal position of the furnace facilitates gradual lateral insertion of samples, for example, during annealing or thermal hardening experiments. Additionally, the modernized system also allows positioning of the furnace at any intermediate angle.

The implementation of the rotary component required calculations of the nominal load for both the furnace and the turntable. It was assumed that the allowable load capacity of the turntable must exceed the combined weight of the mounted element and any potential additional operational loads. The available steel turntable was rated for a maximum load of 100 kg, with geometric dimensions of 171 mm × 171 mm, a sheet thickness of 2.5 mm, and a rotation angle of 360°.

A structural strength analysis of the turntable was subsequently performed to assess its load-bearing capacity. The nominal load, calculated based on the maximum mass of the furnace, was compared with the maximum permissible load specified by the manufacturer. Additionally, the potential bending moment resulting from uneven mass distribution of the furnace or from forces applied offset from the center of rotation was considered. This analysis ensured the safe and stable operation of the rotary system during the use of the modernized research station.

For the analyzed tube furnace, it was assumed that the weight was evenly distributed relative to the center of rotation, allowing the forces acting on the turntable to be considered symmetric. The torque required to initiate movement of the furnace system (i.e., rotation or repositioning) was evaluated. Mounting bolts connecting the turntable to the furnace were selected based on calculations of the nominal load resulting from the furnace’s weight, including the determination of the shear force acting on a single bolt.

Table 4. Tabular summary of the performed estimates and calculations.

No.	Quantity, Description, and Data Used for Calculations	Formula	Result [Unit]	Data Source
1.	Internal Cross-Sectional Area of the Reactor Tube Sr—internal cross-sectional area of the combustion tube in mm2 drw—internal diameter of the combustion tube, drz = 27.0 mm (manufacturer’s specification)	$S_r={\displaystyle \frac{\pi ·d_r^2}{4}}$	572.56 mm2	[44]
2.	External Cross-Sectional Area of the Sample Basket Sk—external cross-sectional surface area of the sample insertion basket, mm2 dkz—external diameter of the sample insertion basket dkz = 24.89 mm (own measurement)	$S_k={\displaystyle \frac{\pi ·d_k^2}{4}}$	486.56 mm2	[45]
3.	Nominal Load on the Turntable Resulting From the Furnace Weight Fp—nominal load of the furnace, N mp—mass of the furnace, mp = 10.1 kg, (manufacturer’s specifications) g—gravitational acceleration, g = 9.81 m·s−2	$F_p=m_p·g$	99.08 N	[46]
4.	Nominal Load Resulting from the Weight of the Turntable Fo—nominal load of the turntable, in N mo—mass of the turntable, mo = 0.846 kg, (manufacturer’s data) g—gravitational acceleration, g = 9.81 m·s−2	$F_o=m_o·g$	8.299 N	[46]
5.	Maximum Load Capacity of the Turntable mmax—maximum mass of the component, m = 50.0 kg (manufacturer’s specifications) Fmax—maximum permissible load of the turntable (50 kg), N	$F_{max}=m_{max}·g$	981.0 N	[46]
6.	Bending Moment Resulting from Furnace Weight Mp—bending moment due to the furnace weight, in N·m Fp—applied force due to the furnace mass, Fp = 99.08 N d—distance from the center of rotation, d = 0.12 m	$M_p=F_p·d$	11.89 N·m	[46]
7	Maximum Bending Moment of the Turntable Fmax—maximum applied load: Fmax = 490.5 N Mmax—maximum bending moment of the turntable in N·m	$M_{max}=F_{max}·d$	117.72 N·m	[46]
8	Shear Force Acting on a Single Mounting Bolt Fs—shear force acting on one bolt, in N Fp—maximum applied load (e.g., maximum permissible load of the turntable), Fp = 99.08 N n—number of mounting bolts, n = 4	$F_s={\displaystyle \frac{F_p}{n}}$	24.77 N	[47]
9	Shear Force Acting on a Single Bolt Securing the Turntable to the Support Frame Fss—shear force acting on one bolt connecting the turntable with the furnace to the support frame, N Fo—nominal load resulting from the weight of the turntable, Fo = 8.299 N Fp—nominal load of the furnace, Fp = 99.08 N n—number of mounting bolts, n = 4	$F_{ss}={\displaystyle \frac{F_o+F_p}{n}}$	27.02 N	[44]
10	Shear Stress Acting on the Bolts Securing the Furnace to the Turntable τs—shear stress in bolts securing the furnace to the turntable, Pa Fs—shear force acting parallel to the surface, N ds2—diameter of the M8 bolt, ds2 = 8.0 mm	${\tau }_s={\displaystyle \frac{F_s}{\frac{\pi ·d_s^2}{4}}}$	0.49 MPa	[47]
11	Shear Stress Acting on Bolts Securing the Turntable with the Furnace to the Support Frame τss—shear stress acting on the bolts securing the turntable with the furnace to the support frame, Pa Fs—shear force acting parallel to the surface, N ds2—diameter of the M8 bolt, ds2 = 8.0 mm	${\tau }_{ss}={\displaystyle \frac{F_{ss}}{\frac{\pi ·d_s^2}{4}}}$	0.537 MPa	[47]

presents the fundamental calculations and estimates used in the selection process.

The nominal load resulting from the furnace’s weight was 99.08 N, approximately one-tenth of the maximum permissible load of the rotary stage, specified at 981.0 N. Similarly, the bending moment generated by the furnace’s weight was calculated as 10% of the maximum bending moment for the applied rotating platform, which was 117.72 N·m. The loads induced by the furnace during orientation changes (rotation) remained significantly below the allowable limits, ensuring sufficient structural integrity and operational safety of the implemented solution.

According to engineering design principles, over-dimensioning components is generally considered suboptimal and uneconomical, as it deviates from the assumptions of efficient and cost-effective design. However, in the context of modernizing an existing laboratory setup, the use of over-dimensioned components may be justified if they ensure the required operational safety and are readily available from the existing inventory. Although such an approach is not optimal from a design perspective, it aligns with sustainable development practices and the zero-waste philosophy, which emphasize maximal use of existing resources and minimization of new component acquisition.

When selecting the bolts for mounting the furnace to the rotating platform, the existing hole pattern in both the platform and support frame was taken into account. M8 bolts (Bispol, Bielsko-Biała, Poland, Wiking, Krakow, Poland), also sourced from the available inventory, were chosen. Verification calculations were subsequently performed to determine the forces acting on the screw connectors and assess their structural adequacy under operational conditions.

Assuming a uniform distribution of the furnace weight over four mounting bolts, the shear force on a single bolt was determined. For the nominal load resulting solely from the furnace mass, the shear force was 24.77 N, whereas including the weight of both the furnace and the rotary stage yielded a shear force of 27.02 N per bolt.

The selected M8 bolts provide a high safety margin and satisfy the mechanical strength requirements for the analyzed assembly. Their tensile strength is 800 MPa [48], and their yield strength is 640 MPa. For the calculations, the permissible shear stress was assumed to be τ_max = 360 MPa, a typical value in bolted joint design according to engineering practice. This corresponds to the common approximation of shear strength as 50–60% of the material’s yield strength and substantially exceeds the stress levels observed in the current assembly, thereby ensuring a considerable safety margin [47].

2.3. Research Station After Modernization

The modernization of the test stand resulted in significant benefits. The replacement of the support frame and the integration of a rotary mechanism have enabled new research possibilities that were previously unavailable. Figure 9 presents a schematic diagram of the modernized test stand.

Before modernization, the tube furnace could only be operated in a fixed vertical position, with samples loaded only from above. The upgraded station now uses a frame adapted from a TV stand, allowing the furnace height to be adjusted. The entire setup is mounted on the platform with lockable wheels, enabling free movement and secure positioning after relocation.

A turntable has also been incorporated, allowing the furnace to be rotated into any orientation—capabilities that were not possible in the original design. Sample feeding has been improved as well. A new stand, placed on a laboratory balance, can be mounted on a vertically adjustable shelf that is part of the TV stand. Alternatively, the stand and scale can be positioned on a scissor lift, providing smooth height adjustment even during experiments.

The redesigned sample stand accommodates a wider variety of sample types, overcoming the limitations of the previous sample basket, which had a porous bottom that restricted sample analysis. Overall, the modernization significantly increased the station’s functionality and flexibility. The furnace is now mobile, height-adjustable, and rotatable, while the new feeding system enables precise handling of various sample types. These improvements make the station more versatile and better suited for advanced laboratory applications.

Figure 10 schematically illustrates the furnace orientation variants used during experimental testing. The vertical upward orientation, shown in Figure 10, is particularly suitable for gas emission analysis, where maintaining a controlled atmosphere during thermal processes is essential. This configuration enables more accurate measurements of gas emission and diffusion parameters. The vertical downward orientation is appropriate for testing samples in gravity-driven processes, such as material combustion or particle deposition. It is especially useful in experiments where the motion of the sample under the influence of gravity is significant. This vertical system for loading solid samples that degrade upon heating (e.g., sintering, cracking, particle shedding, or detachment) ensures that degraded material remains on the stand, guiding the sample into the combustion zone.

The horizontal orientation is ideal for elongated samples, where uniform heat distribution along the sample length is critical. The variant with arbitrary angular positioning enables non-standard experiments designed to meet specific research requirements. As a result of these enhancements, the test stand can now be used not only for thermal analysis but also for uniform heating of samples intended as feedstock or for subsequent experimental evaluation.

The various furnace positioning and sample insertion options also allow for adjustments in the direction of gas flow. Gases passing through the furnace (e.g., air, O₂, N₂) can be arranged in either co-current or counter-current flow. A vertical configuration facilitates the natural rise of hot gases, enhancing homogenization within the reaction zone. Reactions can also be conducted under counter-current conditions (gas from above, sample from below), which is particularly useful for studies on combustion kinetics.

2.4. Evaluation of the Effectiveness of Using Recycled Components

The proposed solution aligns with the principles of the zero-waste philosophy and the circular economy, as evidenced by calculations of component reuse rates based on the research unit’s inventory. Each component was assigned values for quantity, weight (kg), and price (PLN), as presented in

Table 5. Elements of tube furnace modernization: value, weight, price, and source of calculation.

No.	Component Name	Value	Weight kg	Estimated Price, PLN	Data Source
1	TV stand	1	20.00	554.00	[49]
2	Bearing turntable	1	0.846	89.90	[43]
3	Set of bolts, washers, and nuts	1	0.178	4.64	[50]
4	Steel elements used to complete the stand construction	1	0.798	10.00	[51]
5	Elements for constructing a sample loading device	1	0.5	27.00	[50]
6	Scissor lift	1	28.0	475.98	[52]
7	Tube furnace with a programmer	1	15.58	8900.0	[53]
8	Rotameter	1	0.073	159.00	[54]
9	Furnace positioning and leveling control system—spirit levels	1	0.042	10.00	[55]
	Total	9	66.017	10,230.52

, in order to calculate the corresponding indicators.

The quantitative indicator for reused components, W_re-use, was developed based on Gobbo [56] and is calculated as the ratio of repurposed to the total number of elements in the modernized solution.

$$W_{re\text{-}use}={\displaystyle \frac{n_{re\text{-}use}}{n_{total}}}·100\%$$

(1)

where

n_re-use—number of recycled components used, and

n_total—total number of main components of the stand

$$W_{re\text{-}use}={\displaystyle \frac{7}{9}}·100\%=77.78\%$$

(2)

Among the nine main components used in the station’s modernization, seven were recycled, while only two components—the rotameter and the leveling set—were newly purchased. Subsequently, the following indicators were developed and calculated: the mass indicator $W_{re\text{-}use}^{mass}$ and the cost indicator $W_{re\text{-}use}^{value}$, based on Gobbo [56].

The mass index $W_{re\text{-}use}^{mass}$ of recycled materials is defined as the total mass of recycled components relative to the total mass of all components included in the modernized workstation.

$$W_{re\text{-}use}^{mass}={\displaystyle \frac{m_{re\text{-}use}}{m_{total}}}·100\%$$

(3)

where

m_re-use—mass of recycled components used, kg, and

m_total—total mass of main components of the workstation, kg

$$W_{re\text{-}use}^{mass}={\displaystyle \frac{50.322}{66.017}}·100\%=76.23\%$$

(4)

The economic (value) indicator, $W_{re\text{-}use}^{value}$, is defined as the ratio of the economic value of reused components to the total cost of the modernization or construction.

$$W_{re\text{-}use}^{value}={\displaystyle \frac{p_{re\text{-}use}}{p_{total}}}·100\%$$

(5)

where

p_re-use—economic value (purchase value, market value, replacement value) of recycled components, PLN, and

p_total—total value of stand modernization, PLN

$$W_{re\text{-}use}^{value}={\displaystyle \frac{1161.52}{10230.52}}·100\%=11.35\%$$

(6)

2.5. Verification and Testing of the Research Station

Test trials were conducted on the modernized experimental stand. For verification purposes, a sample composed of compacted waste was prepared. The waste material consisted of spent coffee grounds collected from a JURA E6 (JURA, Niederbuchsiten, Switzerland) coffee machine equipped with a grinder. Before compaction, the grounds were dried at 105 °C to remove moisture accumulated during storage and were subsequently compacted using a SIRIO P400 (Sirio Dental, Meldola, Italy) hydraulic press under a pressure of 140 bar.

As a result of the compaction process, a briquette with a mass of m = 1.19 g was obtained from the dried coffee grounds. This sample was used to evaluate the performance of the upgraded experimental stand (research station). The tubular furnace was positioned vertically. The stability of the sample feeding system was verified, the weighing system was leveled, and the sample was inserted from the bottom. The process was conducted in ambient air with an airflow rate of v = 14 × 10⁻³ m³·min⁻¹.

The briquette sample was inserted into the furnace from below using the sample feeding stand. The experiment was conducted at a temperature of up to 450 °C over a duration of 88 min and was terminated when no further mass loss was observed. Throughout the experiment, the sample mass was continuously monitored using a laboratory balance with a precision of 0.01 g. The mass loss over time and the final ash content (mash = 0.01 g) were recorded.

The results of this pilot experiment are presented in Figure 11, illustrating the mass change of the sample as a function of increasing temperature. During the initial stage of heating, no significant changes in the mass of the compacted waste were observed, likely due to the prior drying process performed to prepare the material for storage. Significant mass loss was recorded only at approximately 250 °C.

The second graph (Figure 12) presents the changes in sample mass relative to the duration of the experiment. During the first 20 min, the sample mass remained unchanged, corresponding to the material heating phase. After approximately 40 min, the first noticeable mass changes were observed, coinciding with the temperature exceeding 140 °C. At this stage, the release of bound water and the initial phase of material evaporation likely occurred. In subsequent phases, continued evaporation and combustion of volatile components took place. After 90 min, a significant reduction in sample mass was recorded compared to its initial value.

The observed nonlinearities in the curves result from the complex structure of the material (coffee grounds) and the influence of experimental conditions, such as heat dissipation and mass losses associated with the combustion reaction.

The conducted experiments confirmed that the modernized experimental stand enables precise thermal analysis of compacted waste materials. The implementation of the rotary mechanism and the redesigned sample feeding system ensured stable experimental conditions and uninterrupted process execution. The modernization facilitated the effective combustion of compacted coffee grounds samples. The obtained experimental data were consistent with the initial research assumptions, confirming the capability of achieving accurate and repeatable results regardless of the furnace configuration.

3. Summary and Conclusions

As a result of the modernization, the research station has acquired a number of new functionalities that enhance its utility for conducting experiments. The upgraded configuration allows flexible adjustment of experimental conditions, enabling precise control of operating parameters adjusted to the specifics of the process being performed.

The range of test sample types that can be analyzed has been expanded, including liquid, semi-liquid, paste-like, and non-compacted materials, which was not possible with the previous setup. Improvements have also been made to the sample application method. In addition to the existing vertical top-loading approach, the new configuration allows samples to be inserted from below using a stand, enabling the testing of samples with unconventional shapes or consistencies.

The implemented process and exhaust gas circulation system enable precise dosing, recirculation, and flow balance control. By allowing experiments to be conducted in both co-current and counter-current configurations, the station facilitates the reproduction of diverse process conditions characteristic of real industrial applications.

The research station upgrade project enabled full adjustment of the tube furnace orientation, allowing its position to be adapted to specific experimental requirements. The upgrade introduced 360° rotational capability, enabling precise positioning of the furnace to meet research needs. The integration of the rotary mechanism has significantly enhanced the versatility of the research station, overcoming the major limitations of the previous design. Thanks to the turntable, the furnace can now be positioned horizontally, vertically (upward or downward), or at any intermediate angle, thereby expanding the range of possible experiments, including applications such as the annealing of rod-shaped elements.

System mobility was also improved, allowing easy relocation and adaptation to different laboratory locations and configurations, as well as integration with external or independent devices. Combustion tests of compacted waste materials conducted on the modernized test bench confirmed the validity and effectiveness of the implemented improvements. The observed reuse rates were consistent with the principles of the zero-waste philosophy and the circular economy.

The estimated quantitative reuse rate of components, achieved at 77.78%, demonstrates alignment with the principles of the zero-waste philosophy and the circular economy. The modernization extended the life cycle of the components used, assigning them new functions. Notably, the turntable and screws were repurposed, contributing to sustainability while ensuring adequate mechanical strength through the use of oversized structural elements. This approach minimized new acquisitions, reducing environmental costs and the carbon footprint.

The mass reuse rate of 76.23% provides a more accurate assessment of the environmental benefits, confirming the effectiveness of the modernization. It is noticeable that the cost (economic) indicator, at 11.35%, proved less reliable due to the disproportion between low-value small components and high-value major elements, such as the tube furnace or the controller. Consequently, the economic indicator does not fully reflect the actual environmental effectiveness of the modernization, as it does not account for indirect environmental benefits or the extended potential for reuse of the research infrastructure in the long term.

The cost indicator is most commonly used in comparative analyses. The presented modernization of the laboratory station was practical and purposeful, focusing on restoring and expanding the functionality of the incomplete tube furnace while maintaining the principles of sustainable development and the circular economy. The apparatus was designed with the internal needs of the research team, in particular for experiments related to organic waste processing, rather than as a universal or commercial technical solution.

The study does not claim to provide a universal solution; however, it creates an opportunity for the exchange of experiences, analyses, comparisons, and potentially more advanced modernization of laboratory equipment in accordance with the principles of the circular economy.