Waste-to-Energy Plant Overhead Cranes: Essential Configuration and Selection Guide

Overhead cranes play a crucial role in waste-to-energy plants, including material handling, equipment installation, and maintenance. Proper configuration of these cranes not only enhances the operational efficiency of the plant but also ensures safety and stability in production. Based on years of engineering practice, this article explores the configuration and role of waste-to-energy plant overhead cranes, providing valuable insights for the design and operation of such facilities globally.

I. Basic Configuration of Cranes in Waste-to-Energy Plants

The scale of waste-to-energy plants varies significantly, ranging from small plants with a single line processing 300–500 tons per day (t/d) to large plants with 4–6 lines processing 750–850 t/d per line. Table 1 summarizes the crane configurations and setups in existing projects. The elevation data refers to the rail top elevation, with the effective grab bucket volume indicated in parentheses.

Table 1: Main Technical Parameters of Cranes in Waste-to-Energy Plants

II. Functions and Configurations of Various Cranes

Double Girder Grab Overhead Crane

(1)Waste Handling Crane

The function of the waste handling crane is to grab, pile, dump, and feed the waste inside the waste pit. It is installed above the waste pit, with the lowest point of the grab at least 2 meters clear of the waste feeding hopper level. The garbage grab crane control room is located either opposite or to the side of the waste hopper. The garbage crane and incinerator must operate simultaneously to ensure the safe and stable operation of the incineration plant; otherwise, it will disrupt the feed to the incinerator, potentially causing a shutdown of the entire plant. Therefore, the garbage disposal crane is a core piece of equipment in the incineration plant, requiring extremely high precision, stability, and reliability. Its duty class must meet A8 standards and should be configured with one active and one standby unit.

Additionally, considering the harsh environment (e.g., humid, acidic, containing harmful gases such as CH₄ and H₂S), it is critical to use mature and stable components for the grab, hydraulic systems, and electrical components. Based on years of operational experience, the concentration of flammable and explosive gases in the area where the waste handling crane operates is generally not high, and in most cases, explosion-proof settings are not required.

(2) Ash Grab Crane

The function of the ash grab crane is to move the slag discharged from the incinerator to the transport vehicles. Compared to the garbage grab crane, the performance requirements for the ash grab crane are relatively lower, as it does not need to operate in sync with the incinerator. Considering the limited volume of the slag pit, it is required that the maximum time to resolve any fault in the slag pit should not exceed one day. The control room for the ash grab crane is usually located on the side or at the end of the slag pit, and some incineration plants use remote control for operation.

The duty class of the ash grab crane is generally lower than that of the garbage grab crane, with A6 being sufficient. However, the actual configuration of the unit and the slag storage container should also be considered. In general, incineration plants with more than two incineration lines should use a duty class of A7 or A8. For large incineration plants with four incineration lines, considering the large width of the slag storage area, two ash grab cranes should be used.

Double Girder Overhead Crane

The double girder overhead crane refers to the turbine installation and maintenance crane (hereafter referred to as the turbine crane). Its main function is the installation and maintenance of turbines and generators. Unlike the garbage grab crane and ash grab crane, the turbine crane is only used after the plant is operational. Due to the large size and mass of turbine-generator units, they are typically transported to the waste-to-energy plant in separate parts from the manufacturing facility. The turbine crane is then used to lift and install the components of the turbine and generator. After installation, the turbine crane must be used regularly for the maintenance and inspection of the turbine and generator. The crane is required to operate at full capacity at least twice per year (2 times/a).

Electric Single Girder Underslung Crane

The electric single girder underslung crane is primarily responsible for the maintenance and inspection of the comprehensive pump room, fly ash temporary storage room, workshop, and the baghouse dust collector itself. The design of these rooms requires the hoist to have lifting, trolley, and crane movement functions. For example, in the baghouse dust collector, components such as ash cleaners and bag cages need to be lifted and positioned across the entire work surface. The hoist must be able to reach all areas of the workspace, and the maintenance hoist should be used at least twice per year (2 times/a).

Electric Monorail Cranes

The track of the electric monorail crane is relatively simple, and it is mainly used for lifting and transporting fixed heavy equipment such as fans, pumps, and other rotating machinery. The maximum lifting capacity is no more than 10 tons, with most requiring movement along a single-direction track, while a few only need the lifting function. It is important to note that in some areas, there may be flammable and explosive gases such as H₂S, CO, and NH₃, requiring the use of explosion-proof motors.

III. Crane Selection Methods for Waste-to-Energy Plants

In waste-to-energy plants, there are multiple sets of cranes, each varying significantly in type, lifting capacity, technical requirements, and layout. Items 1 to 3 in Table 1 generally represent the standard configurations for waste-to-energy plants, while other equipment is determined based on the plant’s scale, equipment configuration, and the owner’s requirements.

Cranes can be divided into operational equipment and maintenance equipment according to their function. Both the garbage grab crane and the ash grab crane fall under operational equipment, requiring daily operational hours. In particular, the garbage grab crane must operate continuously with precision and stability, and at least two sets of cranes are necessary. Most projects also require an additional standby grab crane to ensure that operations do not come to a halt due to a malfunction in the garbage grab crane. Maintenance cranes are used less frequently, and their environmental requirements vary.

(1) The maximum lifting capacity of the garbage grab crane is determined by the project’s unit configuration, processing capacity, and waste pit layout. Based on previous project designs, the lifting capacities and grab bucket volumes for garbage grab cranes and ash grab cranes are summarized in the table below.

(2) The lifting capacity of the turbine crane is related to the maximum weight of a single component during the unloading and installation of the generator. Based on accumulated experience, for waste-to-energy units with a capacity below 30 MW and fewer than 3 units, a single turbine crane is generally selected. When the number of units is equal to or exceeds 3, it may be advisable to choose two turbine cranes (one large and one small).

(3) The lifting capacity of other maintenance cranes (items 4–15 in Table 1) depends on the maximum weight of the equipment being serviced. The factors considered when determining the need for a hoist vary:

• The maximum weight of the primary air fan and the induced draft fan is closely related to the processing capacity of each furnace. This is because the incinerator and fan operate on a one-to-one basis—the larger the processing capacity of a single incinerator, the greater the air and exhaust requirements, which in turn increases the size and weight of the fan equipment. Based on engineering project experience, it is recommended to install maintenance hoists for the primary and induced draft fans associated with incinerators processing more than 600 t/d.
• The need for maintenance hoists for feedwater pumps and compressors is not directly related to processing capacity. The decision is based on the maximum weight of the equipment.
• Other hoists, such as those for deacidification towers, dust collectors, and boiler tops, are often positioned at high elevations to prevent falls and ensure worker safety.
• The leachate pump is located in a sealed space filled with humidity, heat, and harmful gases, making the addition of a maintenance hoist helpful in reducing workload and improving safety for maintenance personnel.

In general, the configuration of maintenance cranes in this range is similar to that of other industrial plants (such as wastewater treatment plants, thermal power plants, chemical plants, and steel mills). The main goal is to meet the maintenance needs of equipment, minimize maintenance time, and reduce labor intensity. When selecting small cranes for these applications, the characteristics of waste-to-energy plants do not significantly affect the choice of crane. Engineers can configure cranes according to relevant national or industry standards and site conditions.

Reference: Waste-to-energy Plant Cranes Configuration

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