On most projects a bench test is conducted to determine the best reagent to address the site contaminates and the correct reagent-soil ratio to obtain the required clean-up standards. After the reagent and ratio have been established in the lab it is necessary to duplicate the lab procedures in the field to insure that field results will be satisfactory. LTC has developed equipment and procedures that accurately duplicate, in the field, what was done under laboratory conditions, ensuring field success.
The Lab Procedure The reagents and the site soil sample are accurately weighed & the correct ratio of reagent and soil is prepared. The reagents and soil are thoroughly blended into a homogeneous mixture.
The LTC Dual Axis Blender Lang Tool Co. developed the Dual Axis Blender in order to duplicate lab mixing. This blender turns on a vertical axis while the mixing drums counter-rotate on a horizontal axis. Reagents are delivered between the rotating drums to the area of highest mixing energy. This powerful blender produces effective mixing even in hard clay soils & is durable enough to stand up to the harsh job environment.
The DUAL AXIS BLENDER has the potential to enable the in-situ treatment of sites that were previously regarded as beyond the scope of in-situ treatment and to substantially reduce the cost of treatment in undisturbed, hard soil conditions. When the soil type is hard clay direct injection doesn’t work because the additive mixture takes the path of least resistance. Conventional soil blenders don’t have enough torque to cut hard clay at the depths required and often do not produce a homogenous mixture at these depths. The usual work plan is to do the project in lifts. This involves considerable expense as it requires more equipment and man power. This method is often difficult to perform in tight quarters because it is necessary to have a place to stockpile the excavated material. In some instances it also raises concerns that excavating the material is “transporting hazardous waste”.
CHEMICAL OXIDATION PROJECT 15’ Treatment depth with extremely hard soil conditions 290-LTC equipped with the Dual Axis Blender
Accurate Additive Delivery Effective mixing is only one of the aspects necessary to duplicate lab procedures. The reagents must be accurately measured and delivered in the correct ratio. Lang Tool Co. has developed additional equipment and procedures to insure successful field results virtually 100% of the time. The first step is to produce an accurate AutoCAD drawing of the site treatment area and overlay a cell grid. The cells are designated as in a spreadsheet with alphabetical columns and numerical rows. A corresponding spread sheet is developed that lists the reagent quantities for each cell. The drawing is loaded into the Dual Axis Blender’s onboard GPS location system, allowing the operator to see the cell grid, and the machine and tool location. This information is also broadcasted to a screen on the LTC Chemical Additive Mixing and Pumping Truck.
LTC Mix Truck The LTC Mix Truck is equipped with dual 750 gallon solution tanks. The truck operator controls the consistency of the solution and the rate and quantity of reagent delivery to the blender. While reagent is pumped from tank A to the blender, reagent and water is mixed in tank B and vice versa. The dual tank set up allows soil mixing to continue without interruption, maximizing efficiency and reducing project costs.
Mix Truck Instruments & Controls The LTC Mix Truck has precise controls for the water and reagents delivered into the tanks and the reagent solution sent out to the blender. Dry reagent is vacuum transferred from the onboard scales to the mix tanks. This is a closed system. The truck operator is not exposed to reagent dust.
The Additive Mixing Truck is specifically designed to efficiently and accurately mix, meter, and pump chemical amendments to the soil mixing equipment. This truck is equipped with two 750 gallon tanks and two 4’x4’ platform scales. The truck is hooked into the water supply. The truck has a programmable “IN” meter that shuts the water off when the entered quantity of water is reached. The reagent is delivered to the site in plastic 55 gallon drums with four drums to a pallet. A pallet of reagent is placed on each scale. The vacuum system is programmable in the same manner as the water system. The quantity of water to be added to the selected tank is entered into the water control system and the quantity of reagent to be transferred to the tank is entered into the vacuum control system. The vacuum transfers the dry chemical to the tank while water is being introduced. When the entered quantity of water and reagent is reached the control system shuts off the vacuum transfer and the water. The tanks have agitators and the pumps re-circulate the mixture constantly. When the batch is made the “OUT” meter can be programmed for the cell quantity that is called for on the spreadsheet. The truck has the capability to transfer liquid reagent from the scales to the mix tanks with a pneumatic diaphragm pump. The pump system is programmable in same manner as the vacuum system.
Each treatment cell is 10’ x 10’. The DAB will begin making a vertical plunge in one quadrant of a cell. The truck operator will start to send the reagent solution to the blender. The truck has instrumentation that shows the rate of reagent delivery and the quantity of reagent delivered to each cell. The rate of delivery is adjustable. The truck operator will time the delivery rate to coincide with the rate of decent of the DAB. The accuracy of this operation is enhanced by the GPS system. The blender operator has a split screen showing an aerial view with the machine position and the cell designation and a side cross-sectional view showing the tool depth. This same view is broadcast to a screen on the mix truck so that the truck operator has real time depth information even if the blender is positioned so that the truck operator can’t see the blender boom. When the plunge in the first quadrant is complete the DAB operator will move to the remaining three quadrants and repeat the procedure. When reagent solution has been distributed to all four quadrants the DAB operator will thoroughly mix and homogenize the entire cell.
The truck operator will regulate the flow to coincide with the mixing rate of the blender. The truck will shut off the flow when the programmed cell volume is reached. While the solution is being pumped from the A tank, the B tank will be loaded with water and dry reagent in the same manner as the A tank was. This process will continue so that the blender does not have to stop for a batch to be mixed- while A is unloading B is filling and vice versa. The solution is pumped through flexible hose to the blender. There is a connection at the rear of the machine. The plumbing that commences at the rear of the machine continues over the carbody, up the boom, and to a swivel connection at the top of the Dual Axis blender attachment. From that point the plumbing enters the main casing of the Dual Axis blender and protrudes from the casing near the bottom. This outlet is in the area of the highest mixing energy. All additive pumping, metering, and plumbing components are stainless steel, Viton, Teflon, poly, or EPDM. The system is extremely accurate, insuring that the specified mixture is delivered to the soil mixer at the desired rate. Accuracy in delivery reduces the need for retreatment.
The LTC Mix Truck can transfer liquid reagents such as hydrogen peroxide from the scales to the batch tanks with an air operated diaphragm pump.
The LTC In Situ Chemical Oxidation system was designed to insure that our projects will be implemented efficiently and successfully. High Energy Mixing +Accurate Additive Delivery= A Successful Project
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