Adaptation of Grain Cleaning Equipment for Kalonji and Sesame Seeds

Abstract

Threshing and cleaning are crucial for efficient harvest procedures that are carried out to separate the grains from the biomass and eliminate any potential contaminants or foreign debris. This study examines the cleaning capabilities of the grain cleaning equipment Kimseed Cleaner MK3, a vibratory sieve and air-screen device, for tiny oilseed crops, particularly kalonji (Nigella sativa) and sesame (Sesamum indicum L.), which are valued for their industrial, medicinal, and nutritional properties. These crops frequently provide post-harvest cleaning issues because of their tiny size and vulnerability to contamination from weed seeds, plant residues, and immature or damaged conditions. In order to determine the ideal operating parameters, 0.5 kg of threshed seed samples with 10% moisture content were utilised in the experiment. A variety of shaker frequencies (0.1–10 Hz) and airflow speeds (0.1–10 m/s) were assessed. A two-stage cleaning method was applied for sesame: the first stage targeted larger contaminants (6.5–7.0 Hz and 1.25–1.5 m/s), while the second stage targeted finer impurities (5.25–5.5 Hz and 1.75–2.0 m/s). With a single-stage procedure (5.5–6.0 Hz and 1.0–1.5 m/s), kalonji was successfully cleaned. The findings demonstrated that sesame attained 98.5% purity at the output rate of 200.6 g/min (12.03 kg/h) while kalonji reached 97.6% seed purity at an output rate of 370.2 g/min (22.2 kg/h). These results demonstrate how important carefully regulated shaker frequency and airflow speed are for improving output quality and cleaning effectiveness. The study shows that the Kimseed MK3 is a suitable low-cost, scalable option for research operations and smallholder farmers, providing better seed quality and processing efficiency for underutilised yet economically valuable oilseed crops.

1. Introduction

Sesame (Sesamum indicum L.) and kalonji (Nigella sativa) are small-seed crops that are valued around the world for their numerous uses in cosmetics, health foods, and medicine. According to Peter [1], these plants’ raw seeds are used as staples in cooking and are valued for their nutritional content. Their extracted oils are also used in traditional medicines and cosmetics. These crops, which are specific to areas with a long history of farming, produce a plentiful post-harvest product that is often hampered by the presence of straw, weed debris, and faulty seeds after threshing. Since weed residues in stored grain can encourage fungal development, resulting in spoiling and a noticeable decline in seed integrity, this contamination presents a serious challenge to maintaining quality [1]. As an outcome, efficient cleaning becomes a crucial post-harvest procedure that separates superior seeds from undesirable components to guarantee a longer shelf life and suitability for use later on.

The physical characteristics of kalonji and sesame seeds make the process much more difficult. With a true density of 1224 kg/m³ and sphericity of 62.8% [2], sesame seeds normally have dimensions of 2.80 mm for length, 1.69 mm for width, and 0.82 mm for thickness [3]. Although they have morphological similarities with sesame seeds, kalonji seeds are characterised by their black colour and slightly bigger size, measuring an average of 3.02 mm in length, 1.28 mm in width, and 0.8 mm in thickness, with a true density of 1028% [4] and a sphericity of roughly 48.2% [5]. However, these characteristics may vary slightly depending on the variety and growth environment. These subtle differences highlight the necessity of using precise cleaning methods that are suited to their particular characteristics. Historically, manual methods have been used for seed cleaning, which limits efficiency and scalability because they are time-consuming and labour-intensive [6]. Mechanisation presents a viable option to improve productivity and output quality and to streamline processes as the demand for these crops rises.

To overcome these obstacles, a variety of mechanised cleaning techniques have been created, such as hybrid aeromechanical methods that take advantage of surface texture variations, mechanical approaches that use sieves, and aerodynamic systems that use fans [7]. Air-screen cleaners that can handle a variety of seed lots with extreme precision are frequently used in conjunction with vibratory sieve cleaning, which has gained popularity among these due to its effectiveness in separating seeds from pollutants [8]. The extensive use of different grain cleaning technologies indicates that the agricultural sector has accepted them [9]. However, because of their small size and unique physical characteristics [2,10,11], small oilseed crops like sesame and kalonji frequently require specialised adaptations, making standard equipment inadequate. Due to the current market’s limited possibilities, there is a lack of easily available and efficient methods for processing these important crops.

The Kimseed Cleaner MK3 is a vibratory sieve and air-screen equipment designed especially for the laboratory and small-scale farm environments [12]. This equipment, which is intended to treat harvested grains on-site, incorporates airflow mechanisms and adjustable sieves to address the complexities of small-seed cleaning. It is a viable option for addressing the requirements of post-harvest management for sesame and kalonji due to its small size and dual cleaning method, which combines mechanical vibration with aerodynamic separation [13].

The study aims to evaluate the cleaning performance of the Kimseed Cleaner MK3 for sesame and kalonji seeds, focusing on its ability to remove impurities and identify optimal operational parameters. Emphasis is placed on determining the optimal shaker frequencies and airflow speeds that maximise cleaning efficiency and minimise seed loss. Although there are many different seed cleaning technologies, little research has been conducted on how well they work for small, light oilseeds like kalonji and sesame, especially in environments that are accessible to smallholder or low-input systems. Although these crops are becoming more commercially significant [14,15], cleaning them is still a labour-intensive and inadequately automated process [16]. By experimentally optimising the machine parameters for these commodities, this study fills this gap and advances the creation of workable, scalable post-harvest seed processing solutions. The outcomes will help small-scale growers benefit from improved accessibility and efficiency in mechanised seed cleaning.

2. Methodology

This study used a factorial experimental approach to evaluate the cleaning performance of the Kimseed Cleaner MK3 (Figure 1) for kalonji and sesame seeds. The objective was to identify the best airflow speed and shaker frequency combinations, two crucial operating parameters, to achieve optimal cleaning efficiency and minimise seed loss.

2.1. Research Materials

This study used sesame and kalonji seeds pre-processed using the Kimseed Cleaner MK3 to ensure consistency and uniformity in the input samples. The samples contained seeds with impurities such as capsule fragments and stem residues. Each cleaning trial used 0.5 kg of material at approximately 10% moisture content (dry basis), measured using an OHAUS MB25 moisture analyser.

2.2. Cleaning Equipment

The Kimseed Cleaner MK3 is a bench-scale device with movable sieves and controls that allow for adjustment of the airflow speed (1–10 m/s) and shaker frequency (1–10 Hz) [12]. The study sought to adjust the equipment to the physical properties of small oilseed crops by methodically testing various parameter combinations.

This machine separates the clean seed based on two physical characteristics: size and weight. The input material is automatically fed onto the screen as it is loaded into the hopper after opening the hopper gate. While heavier, appropriately sized seeds pass through to the clean seed output, lighter or larger particles are eliminated using a mix of vibratory screening and airflow separation. The machine specifications and seed flow diagram are shown in

Table 1. Kimseed Cleaner specifications.

Parameter Name	Value
Number of sieves	2
Diameter of the top sieve	380 mm
Diameter of the bottom sieve	247 mm
Hole dimension—top sieve	2.5 mm
Hole dimension—bottom sieve	1.6 mm
Hopper height	1.4 m
Vibration frequency	0.1–10 Hz
Airflow	0.1–10 m/s
Hopper volume	0.018 m3
Angle of inclination of the sieve	7.3 degree

and Figure 2, respectively.

2.3. Experimental Design and Procedure

Cleaning trials were conducted by manually feeding the standardised samples (Figure 3) into the machine. Each trial tested a unique combination of shaker frequency and airflow rate to assess their impact on machine performance.

A two-step cleaning process was implemented for sesame seed cleaning. In Step 1, a 3.5 mm top sieve and a 1.6 mm bottom sieve were used to eliminate large contaminants such as stems and capsule husks. Ten treatment combinations were tested across five shaker frequencies (6.0–8.0 Hz) and two airflow settings (1.25 and 1.5 m/s). Step 2 involved finer cleaning with a 2.0 mm top sieve and the same bottom sieve, across twelve trials using three shaker frequencies (5.25–5.75 Hz) and four airflow speeds (1.5–2.5 m/s).

For kalonji, a single-step cleaning protocol was used with a 2.5 mm top sieve and a 1.6 mm bottom sieve. Twelve treatment combinations were tested, involving shaker frequencies from 5.0–6.5 Hz and airflow speeds of 1.0–1.75 m/s.

While the airflow speed and vibration frequency were changed during the trials, the sieves’ mesh size stayed constant and was chosen according to the size of the seeds. Each trial’s operation time, seed loss, and pollutants left in the clean seed were noted. Because of the machine’s comparatively small capacity, a 50 g clean seed sample was chosen for manual inspection to evaluate cleaning quality. To detect any seed loss, the pollutant output was also analysed.

2.4. Performance Parameters and Calculations

This research was performed to determine the machine’s cleaning rate and efficiency for each trial based on the mass of pollutants and seed loss. The equations that follow were used to determine key performance indicators for each experiment based on the mass of pollutants and lost seeds:

The percentage of clean seeds ${(G}_C)$ was calculated as follows [17]:

$$G_C={\displaystyle \frac{W_S-C_{cg}}{W_S}}\times 100$$

(1)

where $W_S$ is the weight of the sample, (g). $C_{cg}$ is the weight of contaminants in the output cleaned seed, (g).

The percentage of seed loss ${(C}_L)$ was calculated as follows [18]:

$$C_L={\displaystyle \frac{F_L+S_L}{T_S}}\times 100$$

(2)

where $F_L$ is the weight of seed loss by the fan, (g). $S_L$ is the weight of seed loss by the sieve, (g). $T_S$ is the total sample mass (g).

The cleaning efficiency $\left(\eta \right)$ was calculated as follows [19]:

$$\eta ={\displaystyle \frac{G_0}{G_0+C_{cg}}}\times 100$$

(3)

where $G_0$ is the weight of the output clean seed, (g). $C_{cg}$ is the weight of contaminants in the output cleaned seed, (g).

3. Results

3.1. Sesame Cleaning Results

The cleaning of sesame was carried out in two steps after it was threshed in the Kimseed thresher. The first step was conducted with high frequency and low airflow speed to maximise the quantity of the cleaned seed output. The second step was performed with the medium frequency of the shaker, and the airflow speed was higher than that of the first step to increase the percentage of clean seed. Two-step cleaning could cut the cleaning time and produce more clean sesame seeds than one-step cleaning. This could be explained by the fact that when running at low frequency, the straw became caught at the hopper’s outlet, and the mesh of the sieves caused a time-consuming cleaning process. If high-frequency and high-speed airflow are present simultaneously, it leads to significant seed loss. Figure 4 shows the sesame input and output for each step in the experiment with the Kimseed Cleaner MK3. In the first step of cleaning the sesame, the mesh size of the top and bottom sieves was 3.5 mm and 1.6 mm, respectively.

The sample was pre-tested with airflow speeds of 1.0, 1.25, 1.5, and 2.0 m/s before the experiments. It was observed that the clean seed with an airflow speed of 1.0 m/s contained more contaminants than other airflow speeds. Furthermore, the airflow speed of 2.0 m/s resulted in good seeds being blown away into the trash bins. Thus, the airflow speeds of 1.25 m/s and 1.5 m/s were chosen for the experiments.

As presented in

Table 2. Summary of results of cleaning experiments for sesame, Step 1.

Trial	Setting Parameters		Results
	Shaker Frequency (Hz)	Airflow (m/s)	Operation Time (s)	Clean Seed per Hour (g/min)	Seed Loss per Hour (g/min)	Clean Seed Percentage (%)
1	6	1.25	185	46.05	0.02	78.87
2	6	1.5	180	43.67	0.03	80.15
3	6.5	1.25	140	55.71	0.10	81.15
4	6.5	1.5	137	51.24	0.12	82.91
5	7	1.25	92	76.96	0.32	84.75
6	7	1.5	90	76.67	0.34	85.22
7	7.5	1.25	53	131.32	1.35	85.34
8	7.5	1.5	54	124.44	1.49	86.61
9	8	1.25	35	200.57	2.56	86.32
10	8	1.5	37	193.33	2.95	86.64

, the results showed that at the same frequency level of the shaker, the clean seed output rate at the airflow speed of 1.5 m/s was slightly lower than the clean seed output rate at the airflow speed of 1.25 m/s. In contrast, the clean seed percentage at an airflow speed of 1.5 m/s was higher than that at an airflow speed of 1.25 m/s. The highest clean seed output rate that could be reached in this experiment was around 200.57 g/min with the shaker’s frequency of 8 Hz and the airflow speed of 1.25 m/s.

Figure 5 illustrates how the shaker frequency and air velocity affect the clean seed output rate and seed loss (1.25 m/s and 1.5 m/s). Both air velocities exhibit a notable increase in the clean seed output rate as the shaker frequency rises from 6 to 8 Hz, with 1.5 m/s continuously reaching higher capacities. Both higher frequency and air velocity improve separation efficiency, as seen by the clean seed output rate reaching about 200 g/min for 1.25 m/s and over 400 g/min for 1.5 m/s for 8 Hz. But this also results in more seed loss, especially at higher air velocities. At lower frequencies, seed loss is minimal, but after 7 Hz, it increases significantly, particularly for 1.5 m/s, which peaks at 5 g/min. This highlights the necessity to balance cleaning effectiveness and grain retention because higher throughput increases grain ejection.

Figure 6 shows that the clean seed percentage improves as the shaker frequency increases from 6 Hz to 7.5 Hz for both airflow rates. At 1.5 m/s, the clean seed percentage peaks around 87%, demonstrating higher cleaning efficiency. However, beyond 7.5 Hz, there is no further improvement, and the efficiency plateaus. In contrast, at 1.25 m/s, the clean seed percentage reaches about 85% but begins to decline slightly at 8 Hz, indicating the limitations of lower airflow velocity in achieving optimal cleaning at higher frequencies. Thus, 1.5 m/s airflow velocity is more effective for maximising the clean seed percentage, provided the seed loss is managed carefully.

In the second step of cleaning the sesame seed, the mesh of the top sieve was changed for one with a hole diameter of 2.0 mm. The result of cleaning the sesame in this step is shown in

Table 3. Summary of results of cleaning experiments for sesame, Step 2.

Trial	Setting Parameters		Results
	Shaker Frequency (Hz)	Airflow (m/s)	Operation Time (s)	Clean Seed (g/min)	Seed Loss (g/min)	Clean Seed Percentage (%)
1	5.25	1.5	14	42.86	2.99	96.70
2	5.25	1.75	14	41.10	3.21	97.10
3	5.25	2	14	38.32	3.48	97.50
4	5.25	2.5	14	35.47	6.21	98.20
5	5.5	1.5	10	54.40	4.36	96.90
6	5.5	1.75	11	50.20	5.02	97.20
7	5.5	2	10	48.08	5.92	97.70
8	5.5	2.5	11	44.31	9.02	98.30
9	5.75	1.5	8	68.35	6.94	96.80
10	5.75	1.75	8	65.31	9.66	97.20
11	5.75	2	8	61.06	16.19	97.80
12	5.75	2.5	8	57.32	20.84	98.50

.

Figure 7 evaluates the combined effect of shaker frequency and higher air velocities (1.5 to 2.5 m/s) within a narrower frequency range (5.25 to 5.75 Hz). The clean seed output rate improves steadily with increased shaker frequency and airflow, reaching approximately 270 g/min at 2.5 m/s and 5.75 Hz. While higher air velocities enhance cleaning output, they also lead to greater unintended seed discharge. The amount of separated but uncollected grain remains low at 1.5 m/s but rises markedly with increasing airflow, peaking around 55 g/min at 2.5 m/s. This trend suggests that although more vigorous air streams improve the throughput, they simultaneously increase the volume of grain inadvertently expelled. Therefore, precise tuning is essential to avoid excessive grain rejection while maintaining high cleaning efficiency.

Figure 8 highlights the clean seed percentage and shows a clear improvement with increasing airflow velocity. At 2.5 m/s, the clean seed percentage is the highest, ranging from 98.2% to 98.5%. For 2.0 m/s, the clean seed percentage also improves slightly with increasing frequency, rising from 97.5% to 97.8%. In contrast, at 1.75 m/s, the clean seed percentage remains stable around 97.1–97.2%, while at 1.5 m/s, the lowest efficiency is observed, fluctuating around 96.7%.

3.2. Result of Cleaning Kalonji

During the cleaning process of kalonji, the shaking frequency of the cleaner ranged from 5 to 6.5 Hz. When the shaking frequency was set below 5.0 Hz, it resulted in a time-consuming cleaning process for the kalonji seeds. On the other hand, when the shaking frequency was set higher than 6.5 Hz, many seeds were lost. The hole diameter of the top and bottom mesh of the cleaner was 2.5 mm and 1.6 mm, respectively.

Table 4. Summary of results of cleaning experiments.

Trial	Setting Parameters		Results
	Shaker Frequency (Hz)	Airflow (m/s)	Operation Time (s)	Clean Seed (g/min)	Seed Loss (g/min)	Clean Seed Percentage (%)
1	5	1	195	135.38	4.68	93.61
2	5	1.5	196	118.16	7.44	95.28
3	5	1.75	193	91.09	10.40	97.18
4	5.5	1	156	165.00	6.86	93.81
5	5.5	1.5	155	147.10	10.00	95.32
6	5.5	1.75	155	108.39	13.53	97.27
7	6	1	123	203.90	9.64	93.91
8	6	1.5	125	180.48	13.13	95.43
9	6	1.75	124	131.61	17.65	97.38
10	6.5	1	65	370.15	19.64	94.03
11	6.5	1.5	64	305.63	28.50	95.58
12	6.5	1.75	65	214.15	35.78	97.63

and Figure 8 display the results of cleaning kalonji using the machine’s vibration frequency ranging from 5.0 to 6.5 Hz and airflow ranging from 1.0 to 1.75 m/s for the sample weight of 0.5 kg.

Figure 9 illustrates the clean seed percentages. The clean seed output of the machine increased when the shaker frequency increased. With the shaker frequencies of 5.0 Hz and 6.5 Hz, the cleaning machine recorded the lowest and highest capacities at about 91.1 g/min and 370.2 g/min, respectively. The machine’s capacity diminished when the airflow increased, and the clean seed percentage grew. If the machine was set at the frequency and airflow of 6.5 Hz and 1.75 m/s, it reached the maximum percentage of the clean seed output around 97.6%. The clean seed percentage was lowest at 93.6% when the machine operated with a shaker frequency of 5.0 Hz and an airflow of 1.0 m/s. The kalonji seed before and after cleaning is shown in Figure 10.

4. Discussion

The machine’s cleaning efficiency and seed loss for both sesame and kalonji seeds were shown to be highly impacted by two crucial operating parameters: airflow speed and shaker frequency. The experimental results confirmed the working hypothesis, which was that proper modification of these parameters would improve cleaning efficacy while minimising seed loss.

In most cases, increasing the shaker frequency resulted in a slight rise in cleaning effectiveness but also significantly increased seed loss. This pattern is consistent with earlier research findings on seed cleaning. In a study on cleaning peanut seeds, for example, El-Sayed et al. [2] found that while higher oscillation frequency marginally boosted separation efficiency, it significantly increased the rate of seed loss. Similarly, Kharitonov et al. [20] found that increased grain loss resulted from higher oscillation frequencies in sieve mills. According to this, greater shaker frequencies can help transport and stratify seed material through sieves, but they can also push viable seeds into the trash stream, especially when it comes to lightweight or irregularly shaped seeds like kalonji.

The results show that higher airflow speed enhanced cleaning efficiency but also increased seed loss. This is in line with the findings of Liu et al. [6], who observed that higher kernel loss resulted from airflow surpassing the floating velocity of seed pods, while lower airflow rates reduced cleaning efficiency because of inadequate impurity separation. A distinct pattern appeared from the data in Table 2, Table 3 and Table 4, showing that higher airflow speeds enhanced the percentage of clean seed (up to 98.5% in certain sesame and kalonji trials), but they also increased the rate of seed loss. Simonyan and Yiljep [19] similarly validated this trend.

Under optimised conditions, the Kimseed Cleaner MK3 performs similarly to conventional grain cleaning technologies, as seen by the most significant clean seed percentage of 96.7% to 98.5% attained across trials. For example, in a wheat seed cleaning system with optimal feed and airflow conditions, Ali et al. [21] reported 96.25% cleanliness.

Sesame seeds were found to be best cleaned with a shaker frequency of 6.5–7.0 Hz and airflow of 1.25–1.5 m/s in the first cleaning step, and 5.25–5.5 Hz and airflow of 1.75–2.0 m/s in the second cleaning step. Kalonji performed best when the shaker frequency was between 5.5 and 6.0 Hz and the airflow was between 1.0 and 1.5 m/s. These parameter combinations maintained acceptable seed loss levels while optimising cleaning effectiveness. Moreover, the cleanliness percentage of the seeds is also influenced by the sieve’s slope angle and the feed rate. In research on cleaning canola seed, Ghonİmy and Rostom [22] reported that the sieves slope angle changed by 4, 7, and 10 degrees at the same frequency, and the clean seed percentage changed by 97%, 99.2%, and 98%, respectively. Additionally, Hanna and El Ashmawy [23] mentioned that the high feed rate leads to thick layers of material being accumulated on sieves, resulting in a substantial reduction in the conditions required for seeds to penetrate the perforations of the sieves. Thus, it is necessary to evaluate the influence of the feed rate and sieve slope angle on the effectiveness of the cleaning machine.

The findings of this study have applications for small- to medium-sized seed processing, particularly in improving the productivity of the post-harvest mechanisation for oilseed crops like kalonji and sesame. The study provides a framework to enhance processing efficiency, lower losses, and improve seed quality by determining the best machine settings. The combined impacts of feed rate, sieve inclination, and seed flow under semi-automated circumstances, however, require further study due to restrictions like fixed feed rate and sieve slope. The findings might then be more accurately applied, and their scope could be expanded with additional research on continuous-flow systems, other seed varieties, and the combination of sensor-based automation and real-time loss monitoring.

5. Conclusions

This study systematically assessed the cleaning performance of the Kimseed Cleaner MK3 for sesame and kalonji seeds, with a focus on the impact of shaker frequency and airflow speed on cleaning efficiency and capacity. The results demonstrate the significance of adjusting machine settings for each crop type by confirming that both parameters have a significant impact on impurity separation and seed loss. Cleaning sesame in two steps is recommended to remove both large and fine impurities efficiently. A shaker frequency of 6.5–7.0 Hz and an airflow speed of 1.25–1.5 m/s produced the best results in the first step, while 5.25–5.5 Hz and an airflow speed of 1.75–2.0 m/s produced the best results in the second step. An airflow speed of 1.0 to 1.5 m/s and a shaker frequency of 5.5 to 6.0 Hz provided the best cleaning results for kalonji.

Increasing the shaker frequency and airflow generally increased the cleaning efficiency; however, high values resulted in increased seed loss, which had a detrimental effect on overall seed recovery. This compromise emphasises the necessity of carefully adjusting machine settings to balance efficiency and the least amount of seed loss.

The investigation was carried out with a set feed rate and sieve slope angle, both of which can affect material flow and separation, even though it was successful in identifying efficient operating ranges. To improve accuracy and scalability for continuous operations, further studies should examine the effects of feed rate, sieve inclination, and possible automation of feeding processes.