Song Yunwei, Yu Yijiang, Fang Qi
Abstract: According to the sources of agricultural and forestry wastes as the main biomass in Fuyang City, comparative experiments were designed to study the effects of different types and proportions of raw materials on the quality and economic benefits of biomass pellet fuel.The results showed that 100% Low raw materials for the production of raw materials, the highest calorific value, the best quality; raw material ratio of 80% bamboo + 20% fruit branches or rape, the production of products to meet certain quality requirements of the best economic benefits, the local promotion and application The production of biomass pellet fuel with 80% bamboo cuttings and 20% fruit branches or rapeseed rods has achieved good economic benefits as well as certain social and ecological benefits.
With the development of large-scale agroforestry industry, more and more agricultural and forestry wastes have been produced in the process of production and processing.Although biomass energy such as agricultural and forestry wastes has been attracting wide attention nowadays, The local methods of handling agricultural and forestry wastes are still incineration and landfill, and the utilization rate of agricultural and forestry wastes is generally low, and the production of biomass pellet fuel is one of the main ways to utilize agricultural and forestry wastes at present, thus effectively improving the utilization of granular fuel products The quality has become the main method to improve the utilization rate of agricultural and forestry wastes.
In view of this, the paper selects four kinds of agricultural and forestry wastes (bamboo dust, sawdust (mainly fruit tree branches), rape straw and rice straw which are more common in Fuyang City as raw materials for biomass pellet fuel, Than the impact of raw materials on the quality and economic benefits of pellet fuel products, looking for product quality and the best overall raw material ratio to promote the application in Hangzhou[1].
1 materials and methods
1.1 Test Materials
According to the types and amount of agricultural and forestry wastes in Fuyang City, there are four types of raw materials selected for this trial: bamboo dust, sawdust, rape straw and rice straw. The bamboo dust samples come from the production waste of bamboo processing enterprises , Moisture content 40% ~ 50%; sawdust samples such as pear tree branches and other fruit trees, scattered from the seedlings planted scattered collection, moisture content of about 45%; rape stems and rice straw samples are generally scattered from the local agricultural planting, Moisture content of about 20%.
1.2 test method
The test using cold forming process, the main equipment for the ring mode pellet fuel molding machine (Model JWZLH420T), grinder (Model HX-800), three rotary screw dryer, transmission equipment and dust removal equipment, etc. The main process Process shown in Figure 1.
The collected raw materials are piled in a dedicated warehouse and mixed according to the design requirements of the experiment respectively, after being crushed and dried, extruded by a pelletizing machine as biomass pellet fuel, according to the sampling requirements, Of the pellet fuel samples from the Coal Quality Inspection Center of Zhejiang Coal Geological Prospecting Institute for testing to test the main indicators for the evaluation of product quality.
The test was set according to the requirements of Table 1 were 10 treatments, each treatment selected after the ratio of 75t raw materials, test 3d, 2 times a day, each test 12.5t raw materials, a total of 6 tests, that is, 10 treatment 6 times Repeated, a total of 30d to complete the test test.Comprehensive control of the particle size of the pulverized material is about 7mm, after drying the moisture content of the raw material is about 12%, the final product specifications for the diameter of 10mm, length 30 ~ 60mm, Fuel production and energy production in all aspects of energy consumption values.
1.3 product quality and economic efficiency indicators
The quality analysis indicators of the pellet fuel products are mainly determined by the industrial analysis and the elemental analysis indicators of the samples. The specific technical indicators are: Mt, Aad, Vad, FCad, ad) and low calorie (Qnet).
The index of economic benefits mainly includes raw material acquisition cost, labor cost, mechanical loss and depreciation cost, energy consumption in product production process, product sales price and sales volume, among which, labor cost and mechanical loss depreciation cost are not significantly different from 10 treatments, Can be ignored, the product sales price of 1000 yuan / t (calorific value greater than 17572.8kJ / kg), so the main consideration of the test economic indicators for the raw material acquisition costs and energy consumption of the product production process. Raw materials purchase price of 250 yuan / t, sawdust (fruit branches) 200 yuan / t, rape straw 150 yuan / t, rice straw 400 yuan / t.
2 results and analysis
2.1 Particle fuel product quality index analysis
2.1.1 Analysis of technical indicators of pellet fuel industry analysis From Table 2 and Figure 2, it can be seen that the total moisture content of pellet fuel increases with the decrease of the proportion of bamboo charcoal in the feedstock, and 100% bamboo charcoal is used as raw material Of the product (Treatment 1) had a total moisture content of only 5.84%, while the highest moisture content of Treatment 10 was 7.53%, which was inversely proportional to the content of bamboo dust in the raw material.
The contents of fixed carbon and ash in treatments 2, 5 and 8 were lower than those in other samples. From the aspect of raw material ratio, all the three treatments matched a certain amount of sawdust raw material, and therefore, the fixed carbon and ash content Lower than other rapeseed biomass raw materials.
The volatiles content of 10 treatments ranged from 74% to 78%, and varied irregularly with the ratio of raw materials, ie the ratio of raw materials had little effect on volatiles.
2.1.2 Low calorific value analysis From Figure 3 and Table 2, it can be seen that the lowest calorific value of treatment 1 reached 18978.62kJ / kg, the lowest calorific value of treatment 10 was 16635.58kJ / kg, that is, Reduce the content of bamboo charcoal in the raw material with low heat.
2.1.3 Analysis of whole-sulfur content of pellet fuel element index As can be seen from Table 2 and Figure 4, the total sulfur content shows a slight upward trend with the increase of rapeseed rod and rice straw content in the raw materials, but both are below 0.25% The total sulfur content of the sample is relatively low, the impact on the environment smaller.
In summary, according to the raw material ratio of 1 to 8 produced by the production of products, industrial analysis, elemental analysis and low calorifics and other indicators to meet the requirements of product quality.With 100% bamboo as raw material (treatment 1) Produced the best quality of particulate fuel products.
2.2 particulate fuel products, economic analysis
2.2.1 Analysis of raw material and product unit consumption Based on the 12.5t raw material for each test, the average value of 6 repeated tests per treatment is selected as the basis for calculating the raw material consumption, etc. The test results are shown in Table 3. From Figure 5, 6 It can be seen that the consumption of raw materials per unit of product decreases with the content of bamboo charcoal reduced in the proportion of raw materials, the indicators of treatment 6 to 10 have advantages over the first 5 treatments, the lowest consumption of raw materials per ton of processed products 9, The best economic benefit.From the unit product raw material cost index, the treatment of 3, 5, 6, 8, 9 are better, of which the best 9, 6 times.
2.2.2 Energy Analysis of Production Process Biomass pellet fuel is mainly composed of raw materials and products crushed, dried and pelletized. The main energy consumption of these three phases is electrical energy, and in the drying process Some fuelwood consumption[2-4].
Each test based on 12.5t raw materials, the test records the energy consumption of each production link, select the average of 6 repeated tests, the final energy consumption is converted to standard coal (of which converted by the equivalent value of electricity, the coefficient of 0.313kgce / kW · h, firewood conversion coefficient is 0.571kgce / kg), the test results are shown in Table 4. It can be seen that the energy consumption of the drying part of the largest, the second part of the molding process, the crushing part of the least energy consumption, in the drying process , The proportion of diesel consumption accounted for about 85% of energy consumption.Because the fuel used in the drying part of the basic self-provided, so the cost of energy expenditure is the main cost of the entire production process costs.
As can be seen from Figure 7, from the power point of view, the largest energy consumption of particle molding machine, accounting for more than 57% of the power consumption throughout the production process from the sample point of view, to deal with 6,9,10 comprehensive energy consumption Lowest and the best economic benefit.According to the quality index and the economic benefit index of the pellet fuel products, the quality and economic benefit of the pellet fuel processing 6 is the best qualified product with the calorific value of less than 17572.8kJ / kg, which is suitable for the region Promote use.
3 Conclusion
(1) From the perspective of the product quality of pellet fuel, ie heat value, the product with 100% bamboo charcoal raw material has the highest calorific value and the best quality, which basically can replace raw coal.
(2) From the perspective of economic efficiency, the best products produced by other agricultural and forestry wastes such as 80% bamboo charcoal + 20% fruit tree branches or rapeseed rods, on the one hand, the product calorific value can meet the requirements of customers; on the other hand, Acquisition costs for raw materials for agricultural and forestry wastes such as rapeseed rods are relatively low, and energy costs incurred in the production of pellet fuels are at a minimum.
(3) From the point of view of environmental benefit, the 10 treatments of this experiment can rationally utilize agricultural and forestry wastes and improve their utilization efficiency.According to the actual situation of raw materials in all regions, starting from the quality requirements of pellet fuel and combining with economy The optimal ratio of raw materials of 80% bamboo charcoal and 20% rapeseed rod to the best results of social, economic and environmental benefits can be obtained from the following aspects:
4 project examples
Fuyang Ruifeng New Energy Co., Ltd. is a biomass solid fuel pellet production company.Was put into operation, the bamboo pellets as the main raw material for biomass pellet fuel, the annual production of 4300t pellet fuel products, consumption of bamboo waste up to 9000t. After testing, the calorific value of the products is over 18828kJ / kg. The purchase price of bamboo scraps is RMB 250 / t and the cost of raw material acquisition is RMB 2.25 million. Due to the lack of relevant standards of biomass pellet fuel, The market price is based on the calorific value of the product, but not the absolute value of the calorific value of the product. As long as the calorific value is greater than 17572.8 kJ / kg, the price of the pellet fuel product is 1,000 yuan / t.
According to the test results, the raw material ratio was changed to 80% bamboo charcoal + 20% fruit tree branches, rape straw and other agricultural and forestry wastes. After a period of production and testing, the calorific value of the product is about 17991.2 kJ / kg, The average purchase price of other agricultural and forestry wastes such as fruit tree branches and rapeseed rods is about 150 yuan / t, which is much lower than that of bamboo charcoal. According to the current raw material ratio and the current production capacity of the company, the annual raw material purchase cost 207 million yuan, the annual cost savings of 180,000 yuan raw materials.
The energy consumption of products made from bamboo chips is 100kg standard coal / t, the unit power consumption is 121kW · h / t, while the energy consumption of products produced from 80% bamboo cuttings, 20% fruit branches, rape stems, etc. For 82kg standard coal / t, unit power consumption of 106kW · h / t.According to the annual production of 4300t particulate fuel products, the annual savings of 64,500 kW · h.
Comprehensive raw material costs and energy costs in the production process costs, with 80% bamboo + 20% fruit tree branches, rape straw instead of 100% bamboo as raw material to produce particulate fuel products can save 250,000 yuan to ensure product quality, But also save costs and increase economic benefits. It can also improve the status quo of environmental pollution caused by burning firewood and straw, thus achieving a win-win situation of social benefits, economic benefits and environmental benefits.
references
'1' Yao Zonglu, Tian Yishui, Meng Haibo, et al. Biomass solid molding fuel processing production line and related equipment 'J' .Journal of Agricultural Engineering, 2010, 26 (9): 280-285.
'2' MA Xiaoqin. Research Status and Evaluation of Biomass Compression Molding Technology 'J'. Resource Conservation and Comprehensive Utilization, 1998 (3): 39-42.
'3' Shengkui Chuan, Jiang Chengqiu, Zhong Jianli. A Review of Biomass Compression Molding Technologies [J]. Energy Engineering, 1996 (6): 8-11.
'4' Jiang Yang, Qu Jingxia, Guo Jun, et al. Study on the forming conditions of biomass pellet fuel 'J'. Renewable Energy, 2006 (5): 16-18.
