Asphalt mixing station is the core supporting production facility of road engineering and municipal infrastructure. The site selection directly determines the full-cycle operation cost, production efficiency, environmental protection compliance and long-term development space of the project.When many construction enterprises and building materials manufacturers set up their stations, they only pay attention to low land rent, ignore core elements such as logistics, environmental protection and site supporting facilities, and a series of thorny problems such as freight surge, environmental protection punishment, site congestion and inability to expand appear in the later stage.
In this paper, combining the industry practice specification and standardized site selection logic, the site selection scheme of asphalt mixing plant is completely disassembled from the core significance of site selection, seven evaluation elements, logistics calculation, land use standard, site layout, mobile/fixed station difference and pit avoidance points, so as to solve the high-frequency problems such as "how to select the site of asphalt mixing plant, how much land is occupied, how far it is from residential area, and how much raw material transportation distance is controlled".
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The site selection of asphalt mixing station is not simply to find an empty space, but to determine the project profit and sustainable production of the pre-core decision, an unreasonable site will continue to increase operating costs, lead to compliance risks, high-quality sites can achieve cost reduction and efficiency, long-term stable production, its importance is concentrated in five dimensions:
Asphalt mixture has high temperature supply and rigidity requirements, discharge temperature needs to be maintained at 120-150℃, too long transportation distance will cause mixture cooling, material temperature is not up to standard and rejected by construction site, at the same time, oil consumption of insulation tank car, vehicle loss and labor cost rise synchronously.At the same time, sand, aggregate and asphalt account for more than 90% of the raw materials for production. Long-distance transportation of bulk raw materials will greatly increase the production cost per ton of mixture.If the site is remote, the logistics cost per ton of mixture will increase by 10%-30%, which will erode the project profit rate in the long run.
The mixing station has high requirements on the foundation bearing capacity, water supply and drainage, and electric load.Low-lying, soft soil plots need to invest a lot of extra earthwork leveling, foundation reinforcement, flood control and drainage works; narrow site, insufficient road turning radius will cause heavy vehicle queuing congestion, peak production period discharge efficiency greatly reduced.The supporting hydropower, natural gas and fuel oil supply distance is too far, so it is necessary to lay pipelines separately and add standby generator sets, and the one-time capital investment will be doubled.
planning laws and regulations, shutdown punishment risk Asphalt production has four major pollutions: dust, asphalt smoke, noise and peculiar smell. Natural resources and ecological environment departments in various places have mandatory specifications for the isolation distance of industrial land and sensitive areas.If the site is close to residential areas, schools, drinking water sources and nature reserves, the EIA approval will be rejected directly; even if it is completed and put into operation, continuous complaints from residents will be ordered to rectify within a time limit, limit production or even shut down completely, and at the same time, high environmental protection fines will be incurred, delaying the road construction period.Compliance sites can meet air and noise emission control requirements, significantly reducing approval and operational risks.
The pungent smell generated by asphalt heating, all-weather heavy traffic noise and dust, it is easy to cause complaints from surrounding residents.The site selection shall be preferentially planned in industrial parks and open areas in the wild, which shall be located in the downwind direction of the perennial dominant wind direction. Sufficient greening buffer isolation belts shall be set up to reduce neighborhood disputes from the source, avoid intermittent shutdown of production lines due to mass obstruction, and ensure stable supply of road projects.
the high-quality site has stable geology, high and dry terrain, and is far away from geological disasters such as floods, landslides, and fault zones; the site is clearly divided, and the asphalt storage tank, high-temperature mixing area, office area, material yard, and vehicle passage are safely isolated., reduce the risk of fire and equipment overturning.At the same time, 20%-50% spare land shall be reserved. RAP recycled material system, multi-group hot storage bin and multiple mixing production lines can be added in the later stage to adapt to the growth of regional road construction demand without relocation in a short time.
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Seven core evaluation elements of asphalt mixing station site selection When carrying out site selection, a standardized evaluation system shall be established to comprehensively score from seven dimensions: raw material market, traffic accessibility, land topography, supporting energy, environmental protection laws and regulations, community economy and site risk, balance various conditions, and not single emphasis on one index.
is to supply finished hot mix materials nearby. The first principle of site selection is to balance the two requirements of raw material origin and construction site:
Aggregate sand: preferably close to quarry, sand pit, ideal transportation radius control in 20-50km, reduce the long-distance freight of bulk sand;
Asphalt raw material: close to asphalt storage tank station and refinery to ensure stable asphalt supply and reduce liquid asphalt transportation loss;
Spreading project radiation: in the concentrated area of new construction and reconstruction road engineering in the service area, the optimal radius of finished mixture transportation is 16-50km (10-30 miles), and the risk of mixture cooling and scrapping beyond the scope is significantly increased.
Dozens to hundreds of heavy dump trucks and insulated tankers enter and leave the plant every day. Traffic conditions directly affect the daily production capacity limit:
External roads: close to national roads, provincial roads and urban trunk roads, avoid weight-limited bridges, restricted traffic sections in Urban area, no continuous congestion in rainy season and morning and evening peaks; plots with railway and inland river shipping conditions can greatly reduce aggregate bulk transportation costs;
On-site traffic: the outline of the plot is regular, and a complete circular traffic passage is reserved to meet the turning, queuing, weighing and unloading space of heavy vehicles, so as to avoid traffic jam caused by one-way traffic; the entrance and exit are designed separately, and the raw materials enter the factory and the finished products are discharged separately, without cross traffic.
Land occupation requirements of mixing station vary greatly. Terrain and foundation determine the investment of civil engineering reconstruction:
refers to small mobile mixing station (20-80 tons/hour): 0.5-2 mu (2000-8000㎡), suitable for short-term temporary construction site;
Medium-sized fixed mixing station (80-160 tons/hour): 2-5 mu (8000-20000㎡), mainstream configuration of municipal road projects;
Large-scale high-capacity mixing station (more than 160 tons/hour): more than 5-10 mu (more than 20000㎡), regional commercial asphalt production base.
require that high terrain and smooth natural drainage land shall be selected first, and the slope of the site shall be gentle, so as to eliminate low-lying ponding area; the soil bearing capacity shall meet the standard, avoid soft soil, river beach and geological fracture zone, and prevent the settlement and inclination of mixing main building and powder storage tank; space shall be reserved for site expansion, and new recycled material equipment and storage bin shall be planned in the medium and long term.
Asphalt drying, mixing and asphalt insulation of hydropower and gas supporting infrastructure belong to high energy consumption production, and insufficient supporting facilities will cause continuous production cost increase:
Electric power: match high-voltage industrial power supply, reserve 15%-20% redundant load, ensure stable operation of drying cylinder, screening and dust removal system, without frequent voltage fluctuation; long-term fuel cost of self-contained generator shall be calculated in areas without municipal high-voltage power grid;
Water source: stable industrial water supply, used for spraying dust, equipment cooling, site washing, supporting sedimentation tank, rainwater collection system;
Fuel: natural gas, diesel oil, heavy oil supply channels smooth, the nearest storage tank station to reduce fuel transportation costs.
Nature of land: industrial land, cultivated land, basic farmland and ecological land are prohibited from building mixing stations;
Isolation and buffer: Set a legal safe distance from residential areas, schools, hospitals, and reservoir water sources, and the site is located downwind of the prevailing wind direction all year round;
Approval procedures: connect with Natural Resources Bureau and Ecological Environment Bureau in advance, confirm relevant standards for environmental impact assessment, pollution discharge permit, noise control and dust control, and plan land for environmental protection facilities such as closed storage bin, bag dust removal, noise barrier and rainwater oil trap.
comprehensive comparison of land rent, land acquisition and leveling, hardening and transformation total investment, can not only look at land price;
Local policies: Some industrial parks have industrial tax exemptions and environmental protection supporting subsidies, and remote rural plots may have road administration controls and night production restrictions;
Manpower support: the surrounding villages and towns have stable labor resources of drivers, operators and maintenance technicians to ensure continuous production in two shifts;
Mass acceptance: residents in industrial areas and remote rural plots have lower resistance, and suburban plots need to communicate noise reduction and dust suppression schemes in advance.
Climate risk: avoid perennial waterlogging, blizzard road closure and extreme high temperature areas, reserve aggregate anti-freezing sites in the north, and improve flood control and drainage in the south;
Geological risk: keep away from landslide, debris flow and underground goaf, and conduct geological survey in advance;
Land use restriction: confirm the lease term of the plot, and eliminate the risk of failure to renew the lease and demolition and relocation when the short-term land expires.
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Special evaluation method for logistics transportation cost of asphalt mixing station Logistics is the long-term maximum operation expenditure of mixing station. Quantitative calculation model must be established at the site selection stage, and the transportation distance cannot be judged only by experience.
The minimum paving temperature of hot mix asphalt mixture is 120℃. The temperature of mixture decreases obviously with the increase of transportation distance by 10km. It is easy to cause insufficient material temperature when the transportation distance exceeds 50km, and the pavement compaction is not up to standard, resulting in rework.Therefore, it is suggested that the service radius of fixed commercial mixing station should be controlled within 50km, temporary mobile station should be close to the construction bid section, and the transportation distance should be controlled within 15km.
calculate the total transportation tonnage of sand, mineral powder and asphalt in the whole year, and calculate the total annual raw material transportation cost of different plots in combination with local freight rate and fuel unit price;
Discharge logistics (finished product mixture): calculate annual road engineering demand of the region, calculate average transportation mileage, vehicle shift and insulation tank car loss cost;
Hidden costs: peak traffic jam waiting time, vehicle maintenance, driver overtime, scrap rework loss are all included in the calculation.
suitable for small and medium-sized temporary mixing station, short distance supply;
Railway + highway intermodal transportation: large-scale base mixing station, sand aggregate is transported in large quantities by train, and the freight per ton can be reduced by more than 30%;
Water transport connection: coastal areas along the river, sand and gravel ship transportation, greatly reducing the cost of long-distance heavy vehicle passage.
Insufficient standard land demand and space allocation area of asphalt mixing station is the most common mistake in station construction. Many enterprises rent land only according to the existing equipment size. In the later stage, the material pile is congested, there is no expansion space, and the overall production capacity is limited.
Aggregate stacking area, cold storage bin:
accounting for more than 50% of the total land area, is the largest plate, different specifications of sand and gravel bin isolation, supporting canopy, partition wall to prevent mixing;
Stirring main building, hot storage bin, dust removal environmental protection equipment: accounting for 20%-30%;
Circular passage for vehicle passage, weighing and loading and unloading: 15%-20%, reserving space for queuing multiple vehicles at the same time;
Office living area, maintenance workshop, asphalt storage tank, environmental protection buffer green belt: 10%-15%.
Requirements for hard space of site supporting·Stacking area: It is required to meet the aggregate storage capacity for 7 days of continuous production, and each bin shall be provided with partition wall higher than 2.5m to prevent coarse and fine aggregate from affecting mixture ratio;
Production equipment area: mixing main building, drying drum, bag filter reserved maintenance operation space;
Storage tank area: asphalt insulation tank and fuel oil tank shall be isolated separately, and fire prevention spacing and anti-seepage collection tank shall be set;
Buffer isolation zone: green and soundproof buffer land shall be reserved along the boundary of the plot to meet the isolation distance requirements of environmental protection approval.
Terrain reconstruction cost control points Flat land, gentle slope plot reconstruction cost is the lowest; slope is large, low-lying plot needs large-scale earthwork backfill, drainage ditch construction, civil construction cost increases by more than 40%; soft soil foundation needs piling reinforcement, greatly increase one-time investment, under the same conditions, priority is given to the original hard plot.
The reasonable general layout of the site layout plan of the efficient asphalt mixing station can improve the production efficiency by more than 20%, reduce vehicle crossing, reduce dust emission, simplify environmental protection control, and follow five core principles in layout design: material flow in the forward direction, separation of people and vehicles, isolation of high temperature dangerous areas, wind direction adaptation, and reserved expansion.
Entrance and exit and weighbridge: weighing weighbridge shall be set at the main entrance of the plant, raw material vehicles shall be weighed first when entering the plant, and finished product discharge channel shall be set independently to avoid traffic intersection;
arranged on the higher side of the site, relying on gravity to transport materials, reducing the transfer distance of loaders; arranged in the upwind direction along the perennial dominant wind direction, dust does not drift to the office area;
central location of plant, hot material outlet close to loading channel, shorten hot material conveying distance, reduce heat loss;
the mixing area shall be isolated independently from downwind direction, far away from office and stacking area, and fire isolation belt shall be set to avoid high temperature fire risk;
close to the drying cylinder, shorten the exhaust pipe, reduce the fan energy consumption, and reserve equipment maintenance channels;
the prevailing wind direction throughout the year is upwind, far away from dust and smoke areas, and pedestrian passages are set separately to be completely separated from the heavy vehicle driving route.
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The difference in site selection between mobile and fixed asphalt mixing stations is completely different from that of mobile stations and fixed stations. The site selection evaluation standards are obviously different. The construction enterprises shall select the corresponding site standards according to the project cycle and long-term planning.
Ten common fatal misunderstandings in the location of asphalt mixing stations A large number of enterprises have built stations and stepped on pits. The root cause is that the preliminary site selection research is not comprehensive. The following 10 types of high-frequency errors can cause hundreds of thousands or even millions of economic losses. Avoid:
low-cost wasteland seems to save rent, but raw materials, finished products transportation distance doubled, fuel oil, vehicle loss hundreds of thousands more every year, land rent savings can not cover logistics losses.
The pre-verification planning, the red line of environmental protection approval did not connect with the natural resources and ecological environment departments in advance, the land was rented blindly to build factories, the environmental impact assessment did not pass in the later stage, the land did not conform to the industrial planning, and the equipment was forced to relocate or stop work for rectification after completion.
the aggregate stacking is crowded, there is no new recycled material equipment space, the production capacity is limited after 2-3 years of production, and the site can only be relocated.
Low-lying and soft soil plots were selected regardless of terrain drainage and geological carrying capacity. In the rainy season, water accumulated in the field soaked the equipment, and the foundation of the main building was stirred to settle and tilt. The investment in reinforcement and reconstruction in the later period was huge.
hydropower capacity plot is insufficient to meet the high power consumption of the drying drum, and the high additional cost is incurred by laying high voltage lines separately and installing transformers.
no queuing and turning space for heavy vehicles, large area congestion of vehicles in morning and evening peak production, large drop in material flow at sunrise, delay of supply on construction site.
does not isolate sensitive areas. Asphalt odor, dust and noise cause residents to continue to report. Environmental protection departments limit production time or even stop production directly.
Focus only on short-term projects Fixed stations only serve a single short-term road project, there is no stable order after the completion of the project, the site is idle for a long time, and land and equipment resources are wasted.
and professional evaluation of traffic flow is only based on subjective experience. In the later stage, landslide and flood hidden dangers are found in the plot, and the external road is limited in weight and congested all the year round, which cannot meet the traffic requirements of heavy vehicles.
Raw material feeding and finished product discharging share one channel, loaders and tankers interfere with each other, production efficiency is low, and the risk of collision safety accidents is greatly increased.
It is concluded that the site selection of asphalt mixing station is a comprehensive system engineering integrating logistics cost, land infrastructure, environmental protection regulations, safety production and long-term expansion, which cannot be judged solely by one index of land price and traffic.Scientific site selection process should follow: sorting out the distribution of regional raw materials and construction market → quantitative calculation of logistics cost of multiple plots → checking land nature, environmental protection isolation distance and approval conditions → evaluating site area, topography and geology, hydropower supporting facilities → selecting mobile/fixed mixing station according to project cycle → planning efficient layout in the site, and avoiding common mistakes in site selection.
High-quality site can realize continuous reduction of logistics and energy consumption cost per ton of mixture, stable production in compliance, reserve long-term upgrading and expansion space, and improve the overall profitability of asphalt mixing station from the source; otherwise, hasty site selection will bring irreversible problems such as continuous high operation cost, environmental protection penalty and limited production capacity.For enterprises with station construction planning, it is suggested to complete site survey, logistics calculation and EIA pre-examination before land signing, so as to avoid various business risks to the maximum extent.
